Use of Stable Isotopes of Carbon and Nitrogen to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

Home , Isotopes of carbon, Isotope analysis

Prepared in cooperation with Clean Water Services

Scientific Investigations Report 2010–5154 U.S. Department of the Interior U.S. Geological Survey Cover: Photograph of Tualatin River looking downstream from Farmington bridge, July 19, 2008, by Stewart Rounds, U.S. Geological Survey. Back Cover: Top Photograph of Tualatin River at Lee Falls, September 24, 2001, by Stewart Rounds, U.S. Geological Survey Middle Photograph of the Tualatin River near Stafford Road, September 23, 2005, by Stewart Rounds, U.S. Geological Survey Bottom Photograph of Rock Creek Treatment Facility, June 22, 2000, by Dennis Wentz, U.S. Geological Survey Use of Stable Isotopes of Carbon and Nitrogen to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

By Bernadine A. Bonn and Stewart A. Rounds

Prepared in cooperation with Clean Water Services

Scientific Investigations Report 2010–5154

U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior KEN SALAZAR, Secretary U.S. Geological Survey Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1-888-ASK-USGS For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprod To order this and other USGS information products, visit http://store.usgs.gov

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report.

Suggested citation: Bonn, B.A., and Rounds, S.A., 2010, Use of stable isotopes of carbon and nitrogen to identify sources of organic matter to bed sediments of the Tualatin River, Oregon: U.S. Geological Survey Scientific Investigations Report 2010– 5154, 58 p. iii

Contents

Abstract...... 1 Introduction ...... 1 Stable Isotopes...... 3 Description of Study Area...... 3 Purpose and Scope...... 4 Methods and Procedures...... 4 Sample Collection...... 4 Sample Processing...... 6 Analytical Methods...... 7 Stable Isotope and Elemental Analysis...... 7 Other Analyses...... 8 Statistical Methods...... 8 Data Aggregation and Manipulation...... 8 Acidification Correction...... 8 Standard Deviation Adjustment...... 10 Characterization of Bed Sediment and Source Materials...... 11 Bed Sediment...... 11 Leaf Litter and Soil...... 13 Macrophytes...... 15 Phytoplankton and Periphyton...... 15 Suspended Sediment...... 17 Potential Sources of Organic Matter to Tualatin River Sediments...... 19 Principal Components Analysis...... 21 Summary and Conclusions...... 23 Acknowledgments...... 23 References Cited...... 23 Appendix A. Values of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split samples...... 35 iv

Figures

Figure 1. Map showing the Tualatin River basin in northwestern Oregon… ………………… 2 Figure 2. Map showing location of sampling sites in the Tualatin River basin, Oregon… …… 5 Figure 3. Graphs showing regression results for acidified versus unacidified samples from the Tualatin River basin, Oregon… …………………………………………… 9 Figure 4. Graphs showing stable isotope results and C/N ratios for bed sediment samples from the Tualatin River basin, showing observed ranges and outliers… … 12 Figure 5. Graph showing pairwise δ13C differences for several sampling periods compared to results from late-summer-1999………………………………………… 13 Figure 6. Graphs showing stable isotope results for potential source materials of sedimentary organic matter with shading showing observed ranges for each type of material in the Tualatin River basin, Oregon…………………………… 14 Figure 7. Graphs showing comparison of δ13C, δ15N and C/N results for two size fractions of seston for samples from the Tualatin River basin, Oregon… ……………………… 15 Figure 8. Graphs showing stable isotope results for seston and periphyton samples from the Tualatin River basin, Oregon, with shading showing groups of Tualatin River samples… …………………………………………………………… 16 Figure 9. Graphs showing relations between δ13C, δ15N, and C/N in seston samples from the Tualatin River, Oregon, show that high chlorophyll-a concentrations are associated with low δ13C, high δ15N, and low C/N… …………………………… 17 Figure 10. Graphs showing stable isotope results for suspended sediment samples from the Tualatin River basin, Oregon, with shading showing groups of Tualatin River samples… …………………………………………………………… 18 Figure 11. Graphs showing δ13C, δ15N and C/N values for bed sediment and several types of potential source materials from the Tualatin River basin, Oregon… ……… 19 Figure 12. Plots showing a comparison of δ13C, δ15N and C/N for samples of bed sediment, suspended sediment, and seston from the Tualatin River basin, Oregon… ………… 20 Figure 13. Graphs showing δ13C, δ15N and C/N values of terrestrial materials and bed sediment samples from the Tualatin River basin, Oregon…………………………… 20 Figure 14. Graph showing results of a principal components analysis of δ13C, δ15N, and C/N data for samples taken from the Tualatin River basin, Oregon… ……………… 22

Tables

Table 1. Summary of sample collection at each sampling site, Tualatin River basin, Oregon… …………………………………………………………………………… 6 Table 2. Relation between acidified and unacidified δ13C, δ15N, and C/N results for samples from the Tualatin River basin, Oregon……………………………………… 10 Table 3. Confidence intervals of sample means for samples from the Tualatin River basin, Oregon… …………………………………………………………………… 10 Table 4. Ranges of δ13C and δ15N values and C/N ratios for terrestrial plant material… …… 13 Table 5. Results of principal components analysis…………………………………………… 21 Table 6. Mean values and confidence intervals of stable isotope compositions (δ13C, δ15N) and C/N ratios for samples collected in the Tualatin River basin, Oregon… …………………………………………………………………………… 25 v

Conversion Factors, Datum, and Abbreviations and Acronyms

Conversion Factors

Inch/Pound to SI

Multiply By To obtain foot (ft) 0.3048 meter (m) mile (mi) 1.609 kilometer (km) square mile (mi2) 2.590 square kilometer (km2) ounce, fluid (fl.oz) 0.02957 liter (L) cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s) foot per mile (ft/mi) 0.1894 meter per kilometer (m/km)

SI to Inch/Pound

Multiply By To obtain centimeter (cm) 0.3037 inch (in.) micrometer (µm) 0.00003937 inch (in.) meter (m) 3.281 foot (ft) square meter (m2) 0.0002471 acre liter (L) 33.82 ounce, fluid (fl. oz) gram (g) 0.03537 ounce, avoirdupois (oz)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows: °F=(1.8×°C)+32

Datum

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Abbreviations and Acronyms

DO dissolved oxygen PC1 principal component 1 PC2 principal component 2 PCA principal components analysis RM river mile SOD sediment oxygen demand TMDL Total Maximum Daily Load USGS U.S. Geological Survey WWTF wastewater treatment facility vi

This page intentionally left blank.

Use of Stable Isotopes of Carbon and Nitrogen to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

By Bernadine A. Bonn and Stewart A. Rounds

Abstract Introduction

The potential sources of organic matter to bed Dissolved oxygen is essential to the aquatic health of sediment of the Tualatin River in northwestern Oregon many rivers and lakes, and the concentration of dissolved were investigated by comparing the isotopic fractionation oxygen often is used as a water-quality standard to protect fish of carbon and nitrogen and the carbon/nitrogen ratios of and aquatic life. The dissolved oxygen (DO) concentration in potential sources and bed sediments. Samples of bed sediment, a waterbody is affected by many processes, such as exchange suspended sediment, and seston, as well as potential source with the atmosphere (reaeration), photosynthesis by algae materials, such as soil, plant litter, duckweed, and wastewater or aquatic plants, ammonia nitrification, respiration by algae treatment facility effluent particulate were collected in and bacteria, and the bacterially mediated decomposition of 1998–2000. organic matter suspended in the water column or in surficial Based on the isotopic data, terrestrial plants and sediments. The oxygen consumed through the decomposition soils were determined to be the most likely sources of of organic matter in surficial sediments is called sediment organic material to Tualatin River bed sediments. The δ13C oxygen demand (SOD) and can be one of the most important fractionation matched well, and although the δ15N and carbon/ loss processes for DO, particularly in shallow streams. nitrogen ratio of fresh plant litter did not match those of bed Low DO conditions periodically occur in the sediments, the changes expected with decomposition would lower reaches of the Tualatin River and its tributaries in result in a good match. The fact that the isotopic composition northwestern Oregon (fig. 1), especially during low-flow of decomposed terrestrial plant material closely resembled that periods when the water is warm but algal photosynthesis is of soils and bed sediments supports this conclusion. minimal. During such periods, SOD can account for a large Phytoplankton probably was not a major source of fraction of the total DO consumed. The U.S. Geological organic matter to bed sediments. Compared to the values for Survey (USGS) investigated the effects of SOD in the Tualatin bed sediments, the δ13C values and carbon/nitrogen ratios of River, measured a median SOD rate of 2.3 grams of oxygen phytoplankton were too low and the δ15N values were too per square meter of sediment per day (g/m2/d) (Rounds and high. Decomposition would only exacerbate these differences. Doyle, 1997), and determined that SOD and water-column Although phytoplankton cannot be considered a major source oxygen demand are the largest overall sinks for DO in the of organic material to bed sediment, a few bed sediment Tualatin River (Rounds and others, 1999). samples in the lower reach of the river showed a small In response to water-quality problems in the Tualatin influence from phytoplankton as evidenced by lower 13δ C River, Oregon’s Department of Environmental Quality in values than in other bed sediment samples. 1988 adopted a set of Total Maximum Daily Load (TMDL) Isotopic data and carbon/nitrogen ratios for bed sediments regulations in an effort to restore the aesthetic qualities of the generally were similar throughout the basin, supporting the river and protect the river against low DO concentrations and idea of a widespread source such as terrestrial material. The high pH levels. The TMDLs required substantial ammonia δ15N was slightly lower in tributaries and in the upper reaches and phosphorus reductions, which were designed to increase of the river. Higher rates of sediment oxygen demand have DO concentrations and limit the size of algal blooms during been measured in the tributaries in previous studies and the summer months. At that time, it was assumed that coupled with the isotopic data may indicate the presence of algal-derived biomass settling to the river bottom was an more labile organic matter in these areas. Results from this important source of decomposable organic matter, and that study indicate that strategies to improve oxygen conditions limiting the size of algal blooms would not only eliminate in the Tualatin River are likely to be more successful if they high pH levels but also decrease the SOD and increase DO target sources of soil, leaf litter, and other terrestrially derived concentrations. That assumption was challenged by later organic materials to the river rather than the instream growth measurements that determined that SOD rates generally were of algae. 2 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

123°30' 123°15' 123° 122°45' 122°30' OREGON WASHINGTON

45° COLUMBIA 45' 26 5 TILLAMOOK WASHINGTON

TUALATIN MOUNTAINS 205

COLUMBIA Gales 45° 37' Creek RIVER 30" WILLAMETTE

D a i McKay ry COAST RANGE C Portland S r 84 co Forest g Hillsboro g Cornelius i Grove Creek n RM

k B RIVER s Henry 50 c e 45° o av MULTNOMAH R ROCK e 30' Hagg rto CREEK n Cr Lake TUALATIN RIV ER RM Beaverton RM RM 40 70 Creek 60 Fanno Creek CHEHALEM MOUNTAINS 217 Farmington Lake RM Oswego 30 Tigard RM DURHAM 205 20 RM 45° Study 10 22' Area Tualatin 30" YAMHILL Sherwood OREGON RM 0 5 CLACKAMAS Base modified from U.S. Geological Survey and Metro digital data sets (1:24,000) 0 10 20 MILES Projection: Oregon Lambert, North American Datum 1983 0 10 20 KILOMETERS EXPLANATION Designated Urban Growth Boundary (2001) Basin boundary Wastewater Treatment Facility

Figure 1. Tualatin River basin in northwestern Oregon. not elevated in those reaches of the river that had the largest In order to manage and potentially reduce the effects of algae populations, except at one site in the lower river where a SOD, it is important to determine the sources of the organic slightly higher rate might be ascribed to enhanced deposition matter delivered to stream sediments. Potential sources of of algal biomass (Rounds and Doyle, 1997). Furthermore, such organic matter include not only algae, but aquatic plants, water-quality modeling by USGS showed that even if soils, terrestrial plant material, and possibly the particulate ammonia sources were fully controlled, the Tualatin River still in effluent from wastewater treatment facilities (WWTFs). could be subject to periodic low-DO conditions because of DO Many of these materials, however, may be distinguished consumption by SOD (Rounds and others, 1999). Revision of from one another through measurements of the content and the Tualatin River TMDLs in 2001 recognized the importance characteristics of the carbon and nitrogen present in that of SOD and called for significant decreases (20 percent or organic matter. Measurements of stable isotopes of carbon more) in the SOD rate of the river and its tributaries through and nitrogen have been used for many years to investigate the the control of settleable organic materials (Oregon Department nature and sources of organic matter in freshwater systems of Environmental Quality, 2001). (Middelburg and Nieuwenhuize, 1998; Finlay and Kendall, 2007).

tac10-0486_fig01 Introduction 3

Stable Isotopes reservoir, Henry Hagg Lake, which stores water for irrigation, municipal use, and flow augmentation during summer. Gales An element is defined by the number of protons that it Creek also has a significant headwater area in the Coast Range contains; for example, all carbon atoms contain six protons and primarily is forested (70 percent). Dairy Creek is located and all nitrogen atoms contain seven protons. Atoms of the in the northern center of the basin and has a large area of same element, however, may contain different numbers of agricultural land (50 percent) in its drainage. Rock and Fanno neutrons, which cause them to have different masses. Forms Creeks drain the northeastern part of the basin, and contain of the same element that have different masses are called a substantial amount of urban land use (66 and 100 percent, isotopes; stable isotopes are forms that are not radioactive. respectively; data from 2001 National Land Cover Database, Although isotopes vary in the number of neutrons that they see Homer and others, 2007). contain, their chemical properties essentially are identical. Streamflow in the Tualatin River reflects the regional Many elements of biological interest [carbon (C), nitrogen climate, with higher flow during the winter rainy season (N), oxygen (O), sulfur (S)] have different isotopic forms. The (approximately November–April) and the lowest flow during relative abundances of isotopes can be measured with great the dry summer season (May–October). Typical peak annual precision using a mass spectrometer, and such abundances flows are greater than 5,000 ft3/s, whereas typical summertime have been used to study biogeochemical cycles and ecosystem low flows are less than 200 ft3/s. Summer flows are augmented dynamics. to improve water quality through releases from Henry Hagg The use of stable isotope abundances is based on the Lake and from Barney Reservoir, a smaller storage reservoir in fact that different isotopes of an element participate in the the adjacent Trask River basin to the west. Treated wastewater same chemical reactions, but at slightly different rates due from the Rock Creek and Durham advanced WWTFs also add to their different masses. Lighter isotopes typically react a substantial amount of flow to the river. During late summer, at a slightly faster rate, which causes the relative isotopic treated wastewater and reservoir releases can account for as abundance in the reactants and products to differ. This process much as 50 to 75 percent of the flow in the river (Tualatin is called isotopic fractionation. For example, the growth of River Flow Management Technical Committee, 2000). algae tends to create algal biomass that contains less of the The slope, width, adjacent vegetation, and substrate of heavier carbon-13 isotope and more of the lighter carbon-12 the Tualatin River have an effect on the water quality of the isotope. By examining the isotopic composition of potential river. In the Coast Range, the river is steep and runs over a source materials, it might be possible to identify the sources of bedrock substrate that includes several waterfalls. It is clear, organic matter to river bed sediments. cool, and well shaded, and as a result, it is well oxygenated. Where the river meets the valley bottom upstream of Gaston, its slope decreases to just more than 1 ft/mi and it begins to Description of Study Area suspend fine particulate material as it meanders on valley

2 sediments. The river from Gaston to river mile (RM) 30 is The Tualatin River basin is a 712 mi watershed in about 50 ft wide and still relatively well shaded. The lack of northwestern Oregon. Encompassing most of Washington light means that few algae grow in this reach. Near RM 30, County and parts of Multnomah, Clackamas, and several the river transitions to a pooled reach with a slope less than other counties, the basin includes the western part of the 0.1 ft/mi and a width of about 150 ft, allowing solar radiation Portland metropolitan area and was home to approximately to stimulate the growth of algae. The pooled reach, with 450,000 people at the time of this study (U.S. Census Bureau, depths that often exceed 15 ft, is a depositional area that 2000). The river begins in the forested Coast Range mountains accumulates a large amount of organic-rich sediment. This to the west, meanders through a valley bottom farmed for a reach extends downstream to RM 3.4 at the Oswego Dam, wide variety of agricultural products, and skirts the southern a 4-ft high concrete structure built on a shallow bedrock boundary of the urban area before joining the Willamette sill. During summer, the residence time in the pooled reach River upstream (south) of Portland (fig. 1). can be 10–14 days, which is sufficient time to grow a large Five major tributaries enter the Tualatin River, each of population of phytoplankton (free-floating algae) and/or which has distinct characteristics. Scoggins Creek has most of deplete a substantial amount of DO through SOD. its drainage in the Coast Range and contains the basin’s only 4 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

Purpose and Scope organic detritus) samples were collected at two sites in the Tualatin River. Terrestrial materials, such as leaf litter and soil, This report describes the use of carbon and nitrogen also were collected from several sites. stable isotope measurements and carbon/nitrogen (C/N) After the preliminary study indicated that the method ratios to identify the likely sources of organic material to might be successful in identifying the primary sources of bed sediments of the Tualatin River. In particular, the study organic matter to bed sediment, a more extensive study addresses the following questions: was designed and completed. Bed sediment, suspended sediment, and seston samples were obtained at eight sites • Does bed sediment have a similar isotopic composition along the Tualatin River, near the mouths of four tributaries, throughout the Tualatin River? and from Hagg Lake during four separate sampling periods • Is the isotopic composition of bed sediment in the Tualatin (mid‑summer-1999, late-summer-1999, winter-2000, and River similar to that in the tributaries? early-summer-2000). Not every site-material combination was collected during each sampling period. Sites were selected • What are the isotopic compositions of potential source based on several factors, such as (a) location upstream or materials of bed sediment? downstream of WWTF discharges, (b) the amount of algal growth that typically occurs in different river reaches, (c) the • Based on isotopic composition, what source materials relative size of tributary inputs, and (d) safety considerations. appear to contribute most to bed sediment, and is it likely Sites from RM 5.5 to 9.9 typically are influenced by large that the contribution of algae is significant? populations of algae during summer, and sites downstream of These questions are critical to the management of water RM 38.1 are affected by discharges from major WWTFs (at quality in the Tualatin River basin and will help to determine RMs 38.1 and 9.3), whereas sites upstream are less affected the priority of various source-control efforts related to the by algal growth and WWTF discharges. Tributary sites with TMDLs. major contributions to the river were selected rather than The focus of this study was on bed sediment in the lower sites in smaller tributaries. Finally, sites had to be safely Tualatin River where decomposing organic materials on the accessible—sites that were wadeable or accessible by canoe river bed can consume large amounts of dissolved oxygen. were preferred for collecting bed sediment. In all, 92 samples Sediment oxygen demand tends to be most important in the were collected from July 1999 to June 2000 (fig. 2, table 1). pooled reach of the river between RM 30 downstream of Potential sources to the decomposable material in bed Farmington and RM 3.4 at the Oswego Dam because the slow sediment also were sampled. These included various types travel time in this reach favors the exertion of SOD. The scope of organic material such as leaf litter, woody material, and of the study, however, includes bed sediment samples from organic detritus. Soil samples and effluent from the two major farther upstream and from Tualatin River tributaries as well WWTFs were collected. A sample of bryozoans (filter-feeding as a wide range of potential source materials throughout the aquatic invertebrates) also was collected. Materials were drainage basin. Sampled source materials included soils, leaf selected that were readily found in the basin and were either litter and detritus, plankton, aquatic plants, WWTF effluent known to enter the stream network or could be expected to particulate, and suspended sediment. To examine seasonal do so. In all, 50 samples of potential source materials were variations and assess interannual variability, samples were collected. collected at different times of year between late summer of Bed Sediment.—The method used to collect bed sediment 1998 and the summer of 2000. varied depending on the site and sampling period. For the preliminary study (late-summer-1998), a 4.2-cm diameter rigid plastic tube was used by scuba divers to obtain nine Methods and Procedures bed sediment cores from each of two sites. Core sampling was not feasible for the expanded study because some sites were accessible only by bridge. In addition, the stratigraphic Sample Collection information provided by cores was not needed, so a simpler method was used beginning with the mid-summer-1999 A preliminary study was done in the summer of 1998 sampling period. At wadeable sites, bed sediment was to ascertain if stable isotope analysis might be useful in collected using a stainless steel ladle to skim the top 1–2 cm identifying what materials were the primary contributors of sediment from depositional areas. Areas close to the bank to decomposable organic material in Tualatin River bed were avoided to reduce the contribution from nearby soil. sediment. Bed sediment, suspended sediment, and seston Samples from at least three different depositional areas were (suspended particulate material, including plankton and obtained from each site and composited into an 8-oz glass jar. Methods and Procedures 5

123°15' 123°07'30" 123° 122°52'30" 122°45' k e W e I r L 5 Dairy L C A M y 26 E Gales a ek T Creek K re TE c n C R M so IV Creek on ER Creek Br Forest 21 Hillsboro Beaverton Grove Cornelius Rock 15 45° 16 24 23 14 20Creek 30' Henry PORTLAND 17 Hagg Dilley 22 TUALATIN R Lake IVER 9 Beaverton S 10 c Creek og gins Creek Fanno217 11 25 Farmington Tigard Gaston Lake 8 Oswego 6 King 12 7 City 18 Durham 5 4 13 3 45° 19 2 1 StudyStudy Tualatin 22' 205 30" AreaArea OREGONOREGON

Base modified from U.S. Geological Survey and Metro digital data sets (1:24,000) 0 5 10 Miles Projection: Oregon Lambert, North American Datum 1983 EXPLANATION 0 5 10 Kilometers Designated Urban Growth Boundary (2001) 1 Sampling site and map No.

Figure 2. Location of sampling sites in the Tualatin River basin, Oregon.

At sites accessed by canoe or bridge, the same general method DH-81 hand sampler was used for shallow sites. A total of 4 L was applied to a grab sample of streambed sediment collected of water were collected at each site and stored in polyethylene with an Ekman dredge. Obtaining an intact streambed sample bottles. of a depositional area was difficult at some sites. Chunks of Seston.—A nylon plankton tow net with an 80-μm filter wood, concrete, asphalt, and other debris frequently caught in mesh was used to collect seston samples. The net was slowly the jaws of the Ekman dredge and caused any fine depositional towed (by canoe or by hand) in the upper 1 m of the water material to be washed away as the apparatus was retrieved. column but below the water surface. The concentrates from Some samples consisted of only compacted clay with no each tow were composited into glass jars until approximately depositional material. For these reasons, material from only 1 L of concentrate was collected. Total towing time ranged two depositional areas was composited at the most difficult from as little as 5 minutes to more than 90 minutes, depending sites. Bed sediment sampling in the winter proved especially on the amount of seston in the river or lake. difficult because high flows caused the Ekman dredge to drift Other Samples.—The method used to collect other and become snagged on submerged debris, jeopardizing its samples depended on the sample type. In general, aggregated retrieval. Consequently, bed sediment sampling for the winter samples (soil, duckweed mat, leaf litter) were scooped with a period was discontinued after only two sites were sampled. stainless steel ladle, whereas discrete samples (twigs, leaves Suspended Sediment.—Suspended sediment was or needles, periphyton) were hand picked. All samples were collected using a USGS suspended sediment sampler and the placed in glass containers. Samples of wastewater effluent equal‑width-increment method (Edwards and Glysson, 1999). (50 L in stainless steel milk cans) were collected by the A DH-59 sampler attached to a cable was used for deep sites; a operators of the WWTFs.

tac10-0486_fig02 6 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

Table 1. Summary of sample collection at each sampling site, Tualatin River basin, Oregon.

[Location of map No. is shown in figure 2. Gray shading indicates collection of sample. BS, bed sediment; SS, suspended sediment; Ses, seston. Access: C, canoe; B, Bridge; W, wading; T, terrestrial; O, other. RM, river mile]

Late-summer Mid-summer Late-summer Winter Early-summer Map Site name Access 1998 1999 1999 2000 2000 Other No. BS SS Ses BS SS Ses BS SS Ses BS SS Ses BS SS Ses Mainstem sites 1 Tualatin River at RM 5.5 (Stafford Road) C, B 2 Tualatin River at RM 8.7 (Boones Ferry Bridge) C 3 Tualatin River at RM 9.4 (Basalt sill) C 4 Tualatin River at RM 9.9 (Cook Park) C 5 Tualatin River at RM 16.2 (Elsner Bridge) B 6 Tualatin River at RM 20.3 C 7 Tualatin River at RM 24.5 T 8 Tualatin River at RM 26.9 (Scholls) C, B 9 Tualatin River at RM 38.4 (Rood Bridge) C, B 10 Tualatin River at RM 58.8 (Dilley) W, B 11 Tualatin River at RM 67.8 (Cherry Grove) T Tributary sites 12 Fanno Creek at Durham Road B 13 Fanno Creek at Durham City Park W 14 Rock Creek at Highway 8 W, B 15 Dairy Creek at Highway 8 W, B 16 Gales Creek at old Highway 47 W, B 17 Henry Hagg Lake C Other sites 18 Durham Wastewater Treatment Facility O 19 Onion Flat (Cipole Road and Highway 99W) T 20 Tualatin Nature Park T 21 Oregon Graduate Institute (near Bronson Creek) T 22 Rock Creek Wastewater Treatment Facility O 23 Jackson Bottom (between Miller Swale and holding pond) T 24 Zurcher Farm (Fernhill Road near Tualatin River) T 25 Patton Valley Road (north side, 1 mi east of Cherry Grove) T

Sample Processing was centrifuged before filtering to concentrate the solids. One‑half of the seston sample was filtered though a 202-μm After collection, samples were stored at 4 ºC until nylon filter to remove zooplankton and any macroscopic processing, which generally occurred within 48 hours. Sample debris. The resulting seston filtrate contained phytoplankton processing differed somewhat for bulk materials (including as well as suspended material in the 80–202 μm size range. bed sediment, leaf litter, and soil) versus filterable material Ten mL of this fraction was removed, preserved with formalin, (seston, suspended sediment, and WWTF effluent). and sent for algal speciation analysis. Solids from the seston Bulk Material.—Bulk material first was examined filtrate and the remaining unfiltered fraction were captured visually for extraneous material, which was removed with separately on 0.45-μm glass fiber filters. All sample filters forceps; for example, wood pieces were removed from bed were frozen and then freeze-dried. Each dried filter was cut sediment samples. Some bulk material was hand sorted into into three approximately equal wedges that were divided fractions, such as cones and twigs, which were separated among three glass vials (sample splits) and sent for isotopic from duckweed mat. Next, the sample was frozen and then analysis. freeze‑dried. The resulting dehydrated material was ground Summer 1998.—Sample processing differed for the in a mill and portioned into three glass vials (called “sample preliminary study. Bed-sediment cores were frozen and splits”) that were sent for isotopic analysis. then sectioned according to depth. The top 1, 2, or 3 cm of Filtered Material.—Suspended sediment and solids from a core was used depending on the core. Bed sediment was WWTF effluent were captured on 0.45-μm glass fiber filters not composited; rather, each core-section sample was treated that had been baked at 500 ºC for 4 hours. The WWTF effluent separately. Core sections and other bulk materials were dried Methods and Procedures 7 at 45 or 57 ºC, then ground in a mill and divided into vials. Quality Assurance.—Dr. Kendall’s laboratory routinely Bulk materials (other than core sections) were split into three analyzes approximately 10 percent of samples in duplicate glass vials (sample splits). Samples requiring filtration were and analyzes additional splits if results are not within their treated the same as just described for samples collected after expected reproducibility. About 15 percent of the analyses 1998, except that the filters were dried at 45 or 57 ºC. Filters for this study were laboratory splits (“lab splits”). As were cut into three sections which were divided among vials described, all Tualatin River basin samples (except the 1998 (sample splits). core sections) were submitted to the laboratory as triplicate sample splits. The variance of lab splits was not significantly different from the variance of sample splits (α=0.05, F-test). If Analytical Methods the sample material had not been homogeneous before being divided into triplicate splits, the pooled variance of the sample Stable Isotope and Elemental Analysis splits would have exceeded that of the lab splits. The fact that Sample splits were analyzed for carbon and nitrogen the variances are not different is an indication that all splits isotopic and elemental composition by Dr. Carol Kendall’s (sample and lab) were equivalent. Therefore, lab split and laboratory at the USGS facility in Menlo Park, California. sample split results were treated identically. Their method will be summarized here; for a detailed Some of the Tualatin River basin sample results, especially for bed sediment and suspended sediment samples, description, see Kendall and others (2001). Bulk sample splits 15 were subsampled as received. Sample splits on filters were had poorer than expected reproducibility for δ N. Laboratory scraped into a dish and then ground before subsampling. results indicated that these samples typically contained little Approximately 2 mg subsamples were used for highly organic nitrogen, less than 1 micromole (14 μg). Nitrogen content was samples (seston and plant material) and 18–25 mg subsamples low enough in some cases that it was near the detection limit were used for samples that contained less organic matter (bed of the analytical instrument, causing the measurement to have and suspended sediment and WWTF effluent). Following only one significant digit. This resulted in higher variability their standard protocols, the subsamples were vapor acidified among C/N ratios for the sample. to remove carbonate and then analyzed using a Carlo Erba® After the first sets of samples from the Tualatin River basin had been analyzed, it was evident that acidification was elemental analyzer attached to a Micromass Optima mass 15 13 spectrometer. affecting δ N, but not δ C, which was exactly the opposite Carbon and nitrogen isotopic compositions generally are of the desired effect. Samples typically are acidified to prevent carbonate from affecting the δ13C of the organic carbon in expressed as a δ value in units of per mil (parts per thousand). 15 A δ value is calculated relative to standards, carbon in PeeDee the sample, and the acidification should not alter the δ N. belemnite (PDB) and nitrogen in air (see equation 1). A Evidently, samples from the Tualatin River basin contained substance with a higher δ value contains relatively more of the little carbonate and particularly labile nitrogen (C. Kendall, heavier isotope (13C or 15N) and relatively less of the lighter written commun., February 25, 1999). For a number of isotope (12C or 14N) than a substance with a lower δ value. The subsequent samples, both acidified and unacidified subsamples changes in percent composition are very small—a 1 per mil were analyzed. These results confirmed the previous change corresponds to a 0.0011 and 0.0004 percent change in observations. Only unacidified subsamples were analyzed isotope composition for δ13C and δ15N, respectively. for the last sampling period (early-summer-2000). The Carbon and nitrogen content was measured for all inconsistency in acidification procedures resulted in data that samples. For samples collected on filters, however, an were not necessarily comparable. For about 50 percent of the unknown amount of glass fiber was included when the filter samples, all subsamples were acidified before analyses. For was scraped, thus making the percent carbon and percent about 30 percent of the samples, no subsamples were acidified. nitrogen values individually meaningless. The C/N ratio, The remaining samples had some, but not all subsamples, however, is valid and that is the value reported here as an acidified before analysis. Making these data compatible with atomic ratio. each other required devising a method to remove the artifact associated with acidification; this method is described later in this report (see section, “Acidification Correction”).

13C   15 N         12C  14 N  13  sample  15  sample  δC =  −1 × 1000 δ N =  −1 × 1000 (1)  13C    15 N        12C    14 N     PDB    Air  8 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

Other Analyses 2. With the exception of the 1998 bed sediment samples, the mean and standard deviation were calculated from Algal speciation and enumeration was performed the combined results of sample splits and lab splits for by Aquatic Analysts (Friday Harbor, Washington) on each sample. This approach is valid because the sample formalin‑preserved samples by microscopic examination and split variance and lab split variance were not significantly counting at least 500 colonies. Chlorophyll-a concentrations different. in river water were measured by the Clean Water Services Water-Quality Laboratory (Hillsboro, Oregon) as part of a 3. For 1998 bed sediment samples, lab splits were done for routine monitoring program. Samples were collected weekly; some core-section samples but not for others. Sample splits interpolation was used for dates that did not coincide with a were not done for these samples, and it cannot be assumed routine sampling date. Clean Water Services participates in a that one core section was the same as another core section. quality assurance program for chlorophyll-a analysis with the Consequently, a weighted technique was used to calculate USGS Oregon Water Science Center. the mean and standard deviation, giving the same total weight to each core-section sample. Statistical Methods 4. The standard deviation was adjusted for δ15N and C/N averages that were calculated from only acidified results. Several statistical methods were used in this study. In this case, the variability associated with the acidified- Parametric methods (ordinary least squares, linear regression, unacidified correction equation was incorporated. Details mean, standard deviation, and Student’s t-test) were used to of this adjustment are discussed in section, “Standard evaluate results of sample splits, which can be expected to be Deviation Adjustment.” normally distributed. For comparisons among sample results, non-parametric methods were used, including analysis of variance on ranked data, Mann-Whitney U test, and Spearman Acidification Correction rank-order regression (Miller and Miller, 1988; SAS Institute Inc., 1989; Helsel and Hirsch, 1992). A criterion of α = 0.05 Laboratory personnel judged that acidified splits 13 was used for statistical significance unless otherwise noted. produced the most reliable results for δ C and percent 15 Principal components analysis was performed on normalized carbon, and that unacidified splits were better for δ N and data (SAS Institute Inc., 1989). percent nitrogen. Because acidified and unacidified splits were not analyzed for every sample, it was necessary to devise a correction factor for acidification. Data from the Data Aggregation and Manipulation 32 samples having both acidified and unacidified results were examined. The mean value was used when multiple Triplicate sample splits were submitted for almost lab or sample splits had been analyzed, otherwise discrete all samples, with the intent to calculate a mean value and values were used. Analysis of acidified versus unacidified confidence limits for each sample. Two inconsistencies data regressions (fig. 3) showed that the δ13C regression line related to changes in methods of sample collection and was not significantly different from the y=x line, but the analytical procedures resulted in data that were not necessarily δ15N and C/N regressions were significantly different from compatible among splits and could complicate comparisons the y=x line (α=0.05). These results confirmed previous among samples. Specifically, observations: acidification did not significantly affect13 δ C, but • In the 1998 preliminary study, core sections of bed systematically decreased δ15N. Acidification increased C/N sediment were submitted separately; after 1998, bed slightly, which is consistent with the hypothesis that some of sediment samples were submitted as triplicate sample the nitrogen was labile. splits of homogenized composites of surficial sediment. Data shown in figure 3 represent samples of bed sediment, suspended sediment, seston, plant material, and • Acidification of samples prior to analysis was not WWTF effluent solids. When the effect of acidification on consistent and appeared to affect results for nitrogen. δ15N was first observed, it was thought to be limited to the sediment samples. Treating sediment samples separately The following protocol was devised to produce a final dataset from the others, however, showed similar regression statistics that was as internally consistent as possible. between acidified and unacidified results; therefore, all types 1. If a split (sample or lab) was acidified, the 15δ N and C/N of samples were included. results were “corrected” using a linear relation described in Regression equations were applied to all acidified section, “Acidification Correction.” This correction should results for δ15N and C/N, correcting them to the equivalent make all δ15N and C/N results comparable and equivalent of unacidified results table( 2). No correction was applied to to “unacidified.” No correction was needed for 13δ C. δ13C results because the regression line was not significantly different from y=x. Methods and Procedures 9

-20

EXPLANATION Regression line -24 95% confidence limit of regression line 95% prediction limit of regression y=x line (1-to-1 line) -28

-32 C (Acidified sample), in per mil 13 δ -36

-40 -40 -36 -32 -28 -24 -20 δ13C (Unacidified sample), in per mil

12 50

10 40 mil

per 8 in 30

20 4 N (Acidified sample), 5 1 δ C/N atomic ratio (acidified sample) 10 2

0 0 0 2 4 6 8 10 12 0 10 20 30 40 50 δ15N (Unacidified sample), in per mil C/N atomic ratio (unacidified sample)

Figure 3. Regression results for acidified versus unacidified samples from the Tualatin River basin, Oregon. Regression for δ13C is not significantly different from the y = x line. Regressions for δ15N and the C/N atomic ratio are significantly different from the y = x line (α = 0.05).

tac10-0486_fig03 10 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

Table 2. Relation between acidified and unacidifiedδ 13C, δ15N, and C/N results for samples from the Tualatin River basin, Oregon.

[Abbreviations: r2, square of the Pearson correlation coefficient; N, number of points in regression]

Regression statistics Significantly Parameter Standard different from y = x? Correction equation r2 N error (α = 0.05) δ13C 0.95 0.588 32 No None δ15N 0.95 0.487 32 Yes Unacidified = (Acidified + 0.3675) / 0.9385 C/N 0.96 1.360 32 Yes Unacidified = (Acidified – 0.8405) / 1.0131

Standard Deviation Adjustment

As previously described, the mean and standard deviation acidified, the calculated standard deviation underestimates the of all splits was calculated for each sample (a weighted potential variability because it does not include the variability method was used for bed-sediment core sections) after δ15N associated with the acidification correction regression. To and C/N values were corrected for the effects of acidification. remedy this situation, additional variance was added to the For δ15N and C/N results in the case where all splits were variance for the acidified samples:

2  2  s 1 n( yo − y ) var(x ) =e  + , (2) o 2  n 2  slope slope Sxx 

where 2 SSS− 2 xx yy( xy ) se = n( n− 2) Sxx n n n 2 2 Snxxxx =∑( i − ) and Snyyyy =∑( i − ) and Snxxyyxy =∑( i −)( i − ) i=1 i=1 i=1 n is the number of points in the regression line, and x, y points are unacidified values and acidified values, respectively.

Confidence intervals of the sample means provide guidance for interpreting differences; these intervals were calculated using a two-tailed Student’s t-test at the 95-percent level. The mean 95-percent confidence limits are shown intable 3.

Table 3. Confidence intervals of sample means for samples from the Tualatin River basin, Oregon.

Mean 95-percent confidence interval (number of samples) δ13C δ15N C/N atomic ratio All splits acidified ± 0.32 (55) ± 0.44 (55) ± 1.7 (55) All splits unacidified ± 0.33 (90) ± 0.79 (89) ± 2.3 (90) Mixed acidification ± 0.53 (32) ± 0.74 (32) ± 1.2 (32) Characterization of Bed Sediment and Source Materials 11

Characterization of Bed Sediment and Group A generally is between 4.9 and 6.3 per mil, whereas the δ15N of Group B generally is between 1.7 and 4.9 per mil. The Source Materials difference in δ15N values between these groups is statistically significant. Two possibilities that could account for this Isotopic results for δ13C and δ15N as well as the C/N difference are decomposition and WWTF effects. Increases ratios for each sample are shown in table 6 (at back of report). in δ15N values of several per mil have been observed to occur The full datasets are shown in appendix A. with progressive decomposition (Bernasconi and others, 1997; Kendall and others, 2001). If the degree of decomposition explains the difference between Groups A and B, it could Bed Sediment indicate that the sediments in the tributary and upper river sites were “fresher” than materials found in the lower river. δ13C.—The δ13C of bed sediment for Tualatin River basin This explanation is consistent with observed differences samples generally is between -29.4 and -26.9 per mil (fig. 4). in measured SOD rates, which were statistically higher at No general trend with river mile was evident, although the tributary sites than at Tualatin River sites (Rounds and Doyle, lowest values of δ13C in the river tended to occur at RM 9.9. 1997). Alternatively, if the dissolved nitrogen discharged Among the tributaries, δ13C values for the Rock and Fanno from the WWTFs tends to be heavier (higher δ15N), then it is Creek sites were lower than those for either the Gales or Dairy possible that vegetation in the riparian corridor downstream of Creek sites. There were no statistically significant differences the Rock Creek WWTF (RM 38.1) also might have a heavier between tributary and river sites; however, the Rock and nitrogen content. Transport of leaf litter with a higher δ15N Fanno Creek results more closely resembled Tualatin River from the near riparian area might help explain the higher δ15N results from RM 8.7–9.9, whereas the Gales and Dairy Creek of the bed sediment samples collected at and downstream of results were more similar to results from most upstream river RM 26.9. Neither of these hypotheses, however, can be tested sites. with the available data. The δ13C results for the late-summer-1999 samples were The δ15N results from late-summer-1998 bed sediment lower than those obtained at any other time. The lowest δ13C samples should be regarded with some skepticism. These value measured for bed sediment, -30.6 per mil, was obtained samples were collected and processed using a different method during this sampling period. Median differences for pairwise than the other samples (cores versus surficial sediment grab site-matched comparisons between late-summer-1999 results samples, and drying at about 50 ºC versus freeze drying). It and those from mid-summer-1999 and early-summer-2000 is not known if these collection and processing differences were -1.9 and -1.4 per mil, respectively, which were affected the results, but it would not be unreasonable to statistically different from zero (α = 0.05, fig. 5). Statistical suspect that the higher temperature drying method caused tests for differences with late-summer-1998 and with additional nitrogen fractionation. Laboratory personnel winter-2000 were not possible because the number of samples remarked that the nitrogen in Tualatin River bed sediment was too small. samples was particularly labile. Because of the processing Pairwise site-matched comparisons also showed difference, these samples were omitted from further analysis. that δ13C for mid-summer-1999 was greater than δ13C for C/N ratio.—The C/N atomic ratio of bed sediment early‑summer-2000. Because the difference was consistent samples from the Tualatin River basin generally falls within a among all samples (river and tributaries), it was highly narrow range of 12.5–17.7 (fig. 4). No trends related to river significant (p<0.001), but it also was small (0.7 per mil). mile or sampling period were observed with the exception Although this difference may reflect a real seasonal effect of the two winter-2000 samples which had much higher C/N (such as differences in source material), it is possible that this ratios. Both samples from winter-2000 contained woody is a spurious correlation or an artifact related to laboratory debris and although the larger pieces were removed from performance that changed over time. the samples during processing, it is likely that some wood δ15N.—The δ15N of bed sediment for Tualatin River basin remained in the sample at the time of analysis. Because of this samples generally is between 1.7 and 6.3 per mil (fig. 4). No confounding variable and the general lack of winter samples, trends related to season or sampling period were observed. it is impossible to draw conclusions about C/N ratios in bed Inspection of the δ15N results shows that the data divide sediment during the winter season. Two samples obtained in neatly into two groups: Group A comprising lower river sites early-summer-2000 had particularly low C/N ratios which at and downstream of RM 26.9 plus the Rock Creek site, cannot be attributed to any known cause. and Group B including river sites upstream of RM 26.9 plus the Gales, Dairy and Fanno Creek sites (fig. 4). The δ15N of 12 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

TR-26.9 TR-5.5 L-Su-98

Gales Dairy Rock Fanno Fanno* TR-58.8 TR-38.4 TR-26.9

Mid-Summer-99 TR-20.3 TR-16.2 TR-9.9 TR-8.7 TR-5.5

TR-38.4 TR-26.9 TR-20.3 TR-20.3* TR-16.2 Bed sediment

Late-Summer-99 TR-9.9 TR-5.5

TR-26.9 TR-16.2 Winter-00

Gales Dairy Rock Fanno TR-58.8 TR-38.4 TR-26.9 TR-20.3 Early-Summer-00 TR-16.2 TR-9.9 TR-8.7 TR-5.5

-32 -31 -30 -29 -28 -27 -26 1 2 3 4 5 6 7 8 9 5 10 15 20 25 30 35 δ13C, in per mil δ15N, in per mil C/N atomic ratio EXPLANATION Mean value at dot with line showing 5th–95th percentile of means Outlier—outside 1.5x 95% confidence interval of mean— represented by filled dots interquartile range Open and filled dots divide δ15N data Minimum–maximum of means into two groups represented by open dots

Figure 4. Stable isotope results and C/N ratios for bed sediment samples from the Tualatin River basin, showing observed ranges (shaded areas) and outliers (circled values). Lower river and Rock Creek δ15N values (filled dots) are greater than those for upper river and tributary sites (open dots). [Abbreviations: L-Su = late summer, TR = Tualatin River, number following TR = river mile location, * = sample that included deeper anoxic sediment in addition to surficial sediment]. tac10-0486_fig04 Characterization of Bed Sediment and Source Materials 13

The range for C/N is wide, with the highest values 0.5 associated with cones, seed pods and woody material. Wide EXPLANATION ranges of C/N are not uncommon for terrestrial material in 0.0 L-Su-99 - M-Su-99 various stages of decay (Kendall and others, 2001). L-Su-99 - E-Su-00 L-Su-99 - W-00 As materials decompose, the carbon and nitrogen content L-Su-99 - L-Su-98 both decrease. The rates of decay are such that the C/N ratio -0.5 generally decreases as the material becomes progressively more decomposed (Middelburg and Nieuwenhuize, 1998; -1.0 Kendall and others, 2001). In addition, δ15N tends to shift C difference, in per mil

13 toward higher values as the lighter isotopes are removed during decomposition (Bernasconi and others, 1997; -1.5 Middelburg and Nieuwenhuize, 1998; Kendall and others, 2001). Reported changes in δ13C with decomposition,

Bed sediment δ -2.0 however, show less agreement. Middelburg and Nieuwenhuize (1998) reported that the δ13C was 2-3 per mil lower for more degraded material, but Kendall and others (2001) reported -2.5 40 35 30 25 20 15 10 5 0 that δ13C usually increased with decomposition, although the Tualatin River Mile changes were small. Figure 5. Pairwise δ13C differences for several Two samples of decomposed terrestrial detritus were sampling periods compared to results from late- compared to plant litter in this study. Because only two summer-1999. [L-Su = late-summer, E-Su = early-summer, samples of decomposed terrestrial detritus were collected and M-Su = mid-summer, W = winter]. the same material was not tracked through the decomposition process, caution in interpretation is warranted. The δ13C values for detritus are within the range for plant litter, suggesting that δ13C changed little during decomposition for these samples. Leaf Litter and Soil The detrital δ15N values, however, are at the high end of the range for litter, suggesting that some fractionation of nitrogen Coniferous litter, deciduous litter, and woody litter show 13 15 might have occurred during decomposition. Furthermore, the similar values of δ C, δ N, and C/N ratios (fig. 6). The only C/N ratios for the detritus samples are at the low end of the statistically significant difference among these sample data 15 range for litter, supporting the hypothesis that the C/N ratio is that δ N is slightly higher for woody material than for decreases with increasing decomposition. coniferous litter. Different plants utilize different biochemical Soils collected in the Tualatin River basin resemble plant pathways during photosynthesis, and the pathway affects 13 15 13 15 litter for δ C and δ N, but have lower C/N values that are the isotopic composition. The ranges of δ C, δ N, and C/N similar to those of the decomposed terrestrial detritus (fig. 6). values measured in this study are similar to those reported This change in C/N ratio is what would be expected as soil elsewhere for plants that use the C3 pathway of CO2 uptake organic matter derived from plant material ages and becomes (table 4). Vegetation in the riparian areas of the Tualatin more decomposed. Basin is almost exclusively trees and shrubs that utilize the C3 pathway, rather than plants that use the C4 pathway (corn, bamboo and tropical grasses) or the CAM pathway (cacti and desert plants).

Table 4. Ranges of δ13C and δ15N values and C/N ratios for terrestrial plant material.

δ13C δ15N C/N Source (per mil) (per mil) (atomic ratio) This study -30.4 to -21.1 -3.0 to 5.4 20 to 111 Typical reported range1 -32 to -22 -10 to 10 15 to >50 1Typical reported range for vascular plants (C3 pathway) from Finlay and Kendall (2007).

tac10-0486_fig05 14 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

WR Cedar litter (needles) Oct-98 A A WR Cedar litter (mixed) Aug-99 Douglas Fir litter (needles) Oct-98 Douglas Fir litter (mixed) Aug-99 Cones from duckweed mat (TR-20.3) July-99

Coniferous Litter Cones from duckweed mat (TR-9.9) July-99

Alder leaf litter Oct-98 AB A Oregon Ash leaf litter (JB) Oct-98 Oregon Ash leaf litter (JB) Aug-99 Oregon Ash leaf litter (Fanno) July-99 Oregon Ash leaves in stream (TR-20.3) July-99 Oregon Ash leaves in stream (Fanno) July-99 Oregon Ash seed pod July-99 Deciduous Litter Oregon Ash seed pod in stream July-99 Redtwig Dogwood leaves in stream July-99

Douglas Fir twigs Oct-98 B A Terrestrial Twigs from DW mat (TR-26.9) July-99 Twigs from DW mat (TR-16.2) July-99 Twigs from DW mat (TR-9.9) July-99

Woody Litter Woody Twigs from bed sed sample (TR-16.2) July-99

Decomposed mixed detritus July-99 Decomposed non-woody detritus May-00 Detritus

Chehalis soil (JB) Oct-98 B B Chehalis soil (JB) Aug-99 Wapato soil (Zurcher Farm) Oct-98 Woodburn soil (OGI) Oct-98 Soil Agricultural field soil (Onion Flat) July-99 Eroded stream bank, A-horizon (TR-9.9) July-99 Eroded stream bank, bottom (TR-9.9) July-99

Sorted duckweed (TR-24.5) Sept-98 C BC Sorted duckweed (TR-20.3) July-99 Sorted duckweed (TR-26.9) July-99 Sorted duckweed (TR-9.9) July-99 Unsorted duckweed mat (TR-9.9) July-99

Macrophytes Decomposed duckweed mat (TR-9.9) July-99 Grass in stream (Dairy) May-00

Aquatic RC-WWTF Oct-98 C C RC-WWTF July-99 RC-WWTF June-00 Dur-WWTF July-99 Particulate

WWTF Effluent Dur-WWTF June-00

Bryozoan Aug-98

-36 -34 -32 -30 -28 -26 -24 -4 0 4 8 12 16 20 0 20 40 60 80 100 120 δ13C, in per mil δ15N, in per mil C/N atomic ratio

EXPLANATION Mean value at dot with line showing 95% confidence interval of mean Minimum-maximum of means AB Tukey grouping Figure 6. Stable isotope results for potential source materials of sedimentary organic matter with shading showing observed ranges for each type of material in the Tualatin River basin, Oregon. Groups with statistically significant differences α( = 0.05) are denoted with different letters (Tukey Grouping). No significant differences were found among the groups forδ 13C. [Abbreviations: WR = Western Red, TR = Tualatin River, number following TR = river mile location, JB = Jackson Bottom, DW = duckweed, OGI = Oregon Graduate Institute, RCtac10-0486_fig06 = Rock Creek, Dur = Durham, WWTF = Wastewater Treatment Facility]. Characterization of Bed Sediment and Source Materials 15

Macrophytes -24 EXPLANATION -26 Duckweed is a common macrophyte in the Tualatin Regression line 2 River. Duckweed mats on the order of 1 m or larger are not y=x line (1-to-1 line) unusual during low flow in the summer, particularly where -28 they collect on the upstream side of a stationary floating

C, in per mil -30 object such as a log. In addition to duckweed, these mats 13 collect small cones and twigs. Compared to terrestrial plant -32 litter, sorted duckweed (only duckweed leaves and roots) had slightly lower δ13C (-29.8 to -28.5 per mil), higher δ15N (6.8 to -34 10.5 per mil), and lower C/N (11.2 to 14.6) values (fig. 6); the differences for δ15N and C/N were statistically significant. The -36 δ13C is less than typical values reported in the literature for Seston (80-202 µm) δ -38 aquatic macrophytes (-27 to -20 per mil; Finlay and Kendall, 2007). The C/N range is particularly narrow for duckweed -40 compared to terrestrial plant litter. Compared to sorted -40 -38 -36 -34 -32 -30 -28 -26 -24 Seston (>80 µm) δ13C, in per mil duckweed, the unsorted material had δ15N and C/N values closer to leaf litter, showing the influence of cones and twigs. The decomposed duckweed sample had values similar to the 18 unsorted material. 16 Two large WWTFs discharge treated municipal effluent into the Tualatin River at RMs 38.1 and 9.3. The δ13C values 14 for effluent particulate (>0.45 μm) are similar to those for 15 12 terrestrial plant litter and soils (fig. 6). The δ N values are N, in per mil 15 significantly greater than those measured for the terrestrial 10 plants or soils that were sampled. δ15N results for sorted duckweed and WWTF effluent particulate samples are similar 8 (7.2 to 11.6 per mil). This similarity may be a coincidence, but 6 it is not unreasonable to conclude that duckweed downstream of RM 38.1 obtain a substantial amount of nitrogen from Seston (80-202 µm) δ 4 WWTF effluent. Bioavailable nitrogen is in abundant 2 supply due to the WWTF discharges, and uptake in such circumstances typically does not alter the isotopic composition 0 0 2 4 6 8 10 12 14 16 18 of the nitrogen source (Finlay and Kendall, 2007). Because Seston (>80 µm) δ15N, in per mil only WWTF effluent particulate were analyzed in this study, it is not known if the δ15N of dissolved nitrogen in effluent is similar. Compared to other sources, the C/N values for effluent 20 particulate are very low (5.3 to 8.0). 18

Phytoplankton and Periphyton 16 14 The reservoir reach (RM 30–3.4) of the Tualatin River is known for algal production. Because of the river depth and 12 turbidity in this reach, little light reaches the river bottom except at the edges. As a result, most algae in this reach are 10 phytoplankton (free-floating algae); however, periphyton (attached algae) are common at a few riffle sections. To 8 sample phytoplankton, seston samples were collected during Seston (80-202 µm) C/N atomic ratio the summer from RMs 26.9 to 5.5. As previously described 6 in the Sample Processing section, two size fractions were 4 prepared. Figure 7 shows that the δ13C, δ15N, and C/N values 4 6 8 10 12 14 16 18 20 for the two size fractions of seston (>80 μm and 80–202 μm) Seston (>80 µm) C/N atomic ratio are nearly identical, indicating that the presence of Figure 7. Comparison of δ13C, δ15N and C/N results for zooplankton or macroscopic debris in the >80 μm sample did two size fractions of seston (80–202 μm and >80 μm) for not have a significant effect. Only results for the 80–202 μm samples from the Tualatin River basin, Oregon. size fraction are included in subsequent data analyses. tac10-0486_fig07 16 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

Seston samples showed distinctive and statistically mil at RM 26.9 to an average of -38.0 per mil at RM 5.5. significant (α=0.05) trends with river mile for 13δ C, δ15N and Similarly, C/N values decreased from 16.5 to 6.1. The δ15N C/N (fig. 8). The δ13C decreased from an average of -28.8 per showed a similarly strong, but opposite trend; the average

Hagg Fanno TR-26.9 ρ=0.8 ρ=-0.7 ρ=0.9 TR-20.3 TR-16.2 TR-9.9 Mid-Summer-99 TR-8.7 TR-5.5

Hagg

TR-26.9 ρ=1.0 ρ=-1.0 ρ=1.0 TR-20.3

Seston TR-16.2

Late-Summer-99 TR-9.9 TR-5.5

Hagg TR-26.9 ρ=1.0 ρ=-0.8 ρ=0.9 TR-20.3 TR-16.2 TR-9.9

Early-Summer-00 TR-8.7 TR-5.5

unknown species TR-20.3 TR-5.5 unknown species L-Su-98

Fanno Cladophera TR-9.4 Cladophera Spirogyra M-Su-99 TR-5.5 Periphyton TR-9.4 Cladophera L-Su-99

Rock unknown species Cladophera TR-9.4 E-Su-00

-44 -40 -36 -32 -28 -24 -20 -16 0 4 8 12 16 20 0 4 8 12 16 20 0 8 16 24 32 40 δ13C, in per mil δ15N, in per mil C/N atomic ratio Chlorophyll-a, in micrograms per liter EXPLANATION Mean value at dot with line showing 95% Data and Spearman coefficient (ρ) for Measured or interpolated value confidence interval of mean ρ=0.9 correlation with river mile (α=0.05) Figure 8. Stable isotope results for seston (80-202 μm) and periphyton samples from the Tualatin River basin, Oregon, with shading showing groups of Tualatin River samples. [TR = Tualatin River, number following TR = river mile location, L-Su = late-summer, M-Su = mid-summer, E-Su = early-summer].

tac10-0486_fig08 Characterization of Bed Sediment and Source Materials 17

δ15N increased from 5.8 to 13.4 per mil. These changes reflect 20 the increasing presence of phytoplankton in the lower (more 18 downstream) reaches of the river as evidenced by increasing 24.0 chlorophyll-a concentrations. Samples that contain moderate 16 to large amounts of phytoplankton (>15 μg/L chlorophyll-a), 13 therefore, are characterized by low δ C (< -32 per mil), high 14 20.2 δ15N (>8 per mil) and low C/N (<12). These effects of location 15 and chlorophyll-a level are clearly evident when the δ N N, in per mil 12 and C/N are plotted against δ13C in figure 9 with annotations 15 20.3 16.3 showing the chlorophyll-a concentrations. 10 34.2 19.8 Hagg Lake seston showed a pattern that was different Seston δ from seston in the Tualatin River (fig. 8). Visual examination 8 of all Hagg Lake seston samples showed appreciable amounts 12.1 18.7 4.4 of phytoplankton. The C/N ratios of these samples are similar 6 2.5 to the samples from the lower river that contain the most 6.7 phytoplankton, but the δ13C and δ15N values indicated much 4 less fractionation. The low concentrations of nutrients in 20 Hagg Lake compared to the lower Tualatin River may account EXPLANATION 18 6.7 for the differences between the seston samples from these TR-26.9 TR-20.3 4.4 locations. Algae have been reported to exhibit less isotopic 16 TR-16.2 fractionation when carbon and nitrogen are in short supply TR-9.9 2.5 relative to the algal growth rate (Finlay and Kendall, 2007). TR-8.7 14 TR-5.5 Periphyton samples from this study show a wide 20.3 Chlorophyll-a (µg/L) 13 15 13 range of δ C, δ N, and C/N values (fig. 8). Although δ C 12 values for most periphyton samples are similar to those 16.3 19.8 for phytoplankton-rich seston (<-32 per mil), two samples 10 12.1 18.7 13 (one‑quarter of the total) had anomalously high δ C values Seston C/N atomic ratio 8 20.3 (near -18 per mil). No other samples collected during 20.2 this study had δ13C values that high. The δ15N values for 34.2 periphyton generally were less than those for seston samples 6 with high levels of chlorophyll-a (<8 per mil compared to 24.0 4 >8 per mil); the C/N values for phytoplankton-rich seston and -40 -38 -36 -34 -32 -30 -28 periphyton were similar (<12). Seston δ13C, in per mil Figure 9. Relations between δ13C, δ15N, and C/N in seston Suspended Sediment samples from the Tualatin River, Oregon, show that high chlorophyll-a concentrations are associated with low δ13C, high 15 Suspended sediment samples show trends with river mile δ N, and low C/N. [TR = Tualatin River, number following TR = that resemble those of seston samples, but the trends are not as river mile location]. robust: δ13C and C/N decrease with increasing river mile and sediment samples are a mixture of biological and other δ15N increases (fig. 10). Suspended sediment samples with low materials. δ13C (<-32 per mil), high δ15N (>7 per mil) and low C/N (<10) The decreasing trend in δ13C with river mile persists were from the same sections of the river where phytoplankton somewhat for the suspended sediment samples collected in were most prevalent. This result is not surprising because winter, despite the fact that phytoplankton are not prevalent the suspended sediment sampling did not attempt to exclude at that time of year due to high flow, limited light, and cold phytoplankton. As a result, the filterable material from the temperatures. The general lack of phytoplankton in winter is lower river reaches includes a substantial amount of plankton consistent with the absence of any trends with river mile for during the summertime growing period. The main difference δ15N and C/N during the winter sampling. Consequently, the between the suspended sediment and seston samples is that trend in δ13C during the winter is not directly attributable to the former includes particles both smaller than 80 μm and downstream trends associated with plankton populations. larger than 202 μm. The particles smaller than 80 μm are The δ15N and δ13C results show that the suspended composed of plankton as well as colloidal materials from sediment samples can be separated into two groups: samples soil and streambank materials. Particles larger than 202 μm collected from the Tualatin River at and downstream of include some zooplankton as well as larger sediment and RM 26.9 have lower δ13C and higher δ15N than samples detrital materials. The more robust trend in the seston samples, collected from the upper river and tributaries (α = 0.05). The therefore, is consistent with the fact that the seston samples are primary difference, as discussed above, may be caused by the composed predominantly of plankton whereas the suspended presence of more phytoplankton in the lower river samples. tac10-0486_fig09 18 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

TR-26.9 TR-5.5 L-Su-98

Gales Dairy Rock Fannoa Fannob TR-58.8 ρ=-0.7 ρ=0.8 ρ=0.9 TR-38.4 TR-26.9 TR-20.3

Mid-Summer-99 TR-16.2a TR-16.2b TR-9.9 TR-8.7 TR-5.5

NS TR-38.4 ρ*=0.8 TR-26.9 ρ=-0.7 TR-20.3 TR-16.2 TR-9.9 Late-Summer-99 TR-5.5

Gales

Suspended sediment Dairy Rock Fanno NS TR-58.8 NS

Winter-00 TR-38.4 ρ=0.9 TR-26.9 TR-16.2 TR-5.5

Gales Dairy Rock Fanno TR-58.8 ρ*=0.7 ρ=1.0=-1.0 TR-38.4 TR-26.9 TR-20.3 NS Early-Summer-00 TR-16.2 TR-9.9 TR-8.7 TR-5.5

-38 -36 -34 -32 -30 -28 -26 1 3 5 7 9 11 13 15 0 8 16 24 32 40 δ13C, in per mil δ15N, in per mil C/N atomic ratio

EXPLANATION Mean value at dot with line showing 95% confidence interval of mean Data and Spearman coefficient (ρ) for Filled dots represent river sites downstream of RM 30 ρ=1.0 correlation with river mile Open dots represent tributary sites plus river sites upstream of RM 30 Figure 10. Stable isotope results for suspended sediment samples from the Tualatin River basin, Oregon, with shading showing groups of Tualatin River samples. Trends with river mile shown with a correlation coefficient (Spearmanρ ) were statistically significant α( = 0.05, α = 0.08 for ρ*, NS = not significant). a[ = fraction that settled after 24 hours, b = fraction remaining suspended after 24 hours, TR = Tualatin River, number following TR = river mile location, L-Su = late-summer]. tac10-0486_fig10 Potential Sources of Organic Matter to Tualatin River Sediments 19

Potential Sources of Organic Matter to 18 Tualatin River Sediments 16

14 To assess the degree to which a range of sampled materials (soil, leaf litter, detritus, plankton, duckweed, 12 WWTF effluent) might be important sources of organic material to Tualatin River bed sediment, the carbon and 10 nitrogen isotopic data and C/N ratios of these sources were 8 N, in per mil

compared to those of bed sediment. Because the organic 15 δ material in bed sediment has decomposed over time, the 6 isotopic and C/N values have likely changed relative to their original sources. Microbial decomposition increases the 4 δ15N by a few per mil and can substantially decrease the C/N 2 ratio (Middelburg and Nieuwenhuize, 1998; Kendall and 15 others, 2001). Finlay and Kendall (2007) report that the δ N 0 increases associated with decomposition are most pronounced 36 in streams that contain ample nitrate, a condition that is true EXPLANATION 13 32 for the Tualatin River. Decomposition also may alter the δ C, Bed sediment but the effect is less and tends to be small (Kendall and others, Bryozoan 28 Duckweed 2001). Periphyton Several substances (bryozoan, duckweed, periphyton, 24 WWTF effluent and WWTF effluent particulate) can be dismissed as primary particulate sources of organic matter to bed sediment because the patterns 20 in their isotopic and C/N ratios do not match those of bed 16 sediment, even if trends associated with decomposition are C/N atomic ratio taken into account (fig. 11). The δ13C values for bryozoan 12 and periphyton are substantially different from those of bed sediment. The δ15N values of bryozoan, duckweed, 8 and WWTF effluent particulate are greater than those for 4 bed sediment. The C/N values for bryozoan, periphyton and WWTF effluent particulate are less than those for bed 0 -44 -40 -36 -32 -28 -24 -20 -16 sediment. As these substances decompose, their δ15N values δ13C, in per mil can be expected to increase and their C/N ratios to decrease, making the differences compared to bed sediment even Figure 11. δ13C, δ15N and C/N values for bed sediment and greater. several types of potential source materials from the Tualatin River A comparison of seston and suspended sediment to basin, Oregon. [WWTF = Wastewater Treatment Facility]. bed sediment shows that the seston and suspended sediment samples that contain the most phytoplankton (those at and downstream of RM 16.2) do not resemble bed sediment for to these samples were significant, however, the C/N ratio of δ13C, δ15N or C/N (fig. 12). The expected changes associated the late-summer-1999 bed sediment samples should have with decomposition (increased δ15N, decreased C/N) will been lower. For all of these reasons, phytoplankton probably further amplify these differences. Seston and suspended is not contributing significant amounts of organic matter to sediment obtained from tributaries and in the more upstream Tualatin River bed sediment. This conclusion is consistent reaches of the Tualatin River compare more favorably with field measurements of SOD rates in the Tualatin River, with bed sediment. It is difficult to know whether this which indicated that the river reaches with the largest algal suspended particulate organic material is a source to the bed populations did not have significantly higher SOD rates, sediment or vice versa. Bed sediment samples collected in except at RM 5.5 where a slightly higher rate might be late‑summer-1999 have lower δ13C and higher δ15N than other attributed to some deposition of algal detritus (Rounds and bed sediment samples, which might indicate some contribution Doyle, 1997). from phytoplankton. If the contribution of phytoplankton

tac10-0486_fig11 20 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

A comparison of terrestrial source materials to bed than those for bed sediment, but these ratios are expected sediment shows considerable overlap for δ13C and δ15N for to decrease with decomposition. In fact, the two samples of deciduous litter, woody material, and soil (fig. 13). The range decomposed terrestrial detritus show C/N ratios that are much of δ13C values for plant litter and woody material encompasses more similar to those of bed sediment. The δ13C, δ15N, and the δ13C range for bed sediment. Although δ15N values for C/N data from soil samples also show substantial overlap with many of the deciduous litter samples are lower than those of the bed sediment data. Although this could indicate that eroded bed sediment, increasing these values by 2–3 per mil (within soil is a source of bed sediment, it is equally consistent with the expected effect of decomposition) places them directly plant litter and woody material being the primary source of in the range of δ15N values for bed sediment. The C/N ratios organic matter to soil and Tualatin River bed sediment. for all litter and woody material samples are much higher

20 8

18 6 16

14 4 12

10 2 N, in per mil N, in per mil 15

8 15 δ δ 0 6

4 -2 2

0 -4 36 120

EXPLANATION EXPLANATION 32 Bed sediment Bed sediment Bed sediment, L-Su-99 100 Coniferous litter Seston, RM ≤ 16.2 28 Deciduous litter Seston, RM > 16.2 Decomposed terrestrial Suspended sediment, 80 detritus 24 RM ≤ 26.9 Soil Suspended sediment, Woody material tributaries + RM > 26.9 20 60 C/N atomic ratio

16 C/N atomic ratio 40 12 20 8

4 0 -40 -38 -36 -34 -32 -30 -28 -26 -32 -30 -28 -26 -24 δ13C, in per mil δ13C, in per mil

Figure 12. Comparison of δ13C, δ15N and C/N for Figure 13. δ13C, δ15N and C/N values of terrestrial samples of bed sediment, suspended sediment, and materials and bed sediment samples from the Tualatin seston from the Tualatin River basin, Oregon. [RM = river River basin, Oregon. mile].

tac10-0486_fig12 tac10-0486_fig13 Potential Sources of Organic Matter to Tualatin River Sediments 21

Principal Components Analysis • Terrestrial litter (coniferous, deciduous, or woody) have principal component values characterized by Principal components analysis (PCA) is a statistical higher C/N and lower δ15N compared to bed sediment. technique used to reduced the dimensionality of datasets Decomposition of this material results in decreased C/N that contain multiple variables. In PCA, new axes (principal and increased δ15N. Assuming a 25 percent decrease in components) are created that are linear combinations of the C/N coupled with a 2 per mil increase in δ15N results original variables. The greatest variability within the dataset is in a trajectory that leads directly to the region where captured by the first principal component (PC1). The second bed sediments plot. Examination of data reported by principal component (PC2) is orthogonal to PC1 and captures Middelburg and Nieuwenhuize (1998) for suspended the greatest remaining variability. PCA was applied to this matter in progressive stages of decomposition showed dataset as a method to visualize the three variables δ13C, δ15N, an approximate 10 percent decrease in C/N with each and C/N in a two dimensional plot. As part of PCA, the data 1 per mil increase in δ15N, which is consistent with the were normalized (by subtracting the mean and dividing by the calculated trajectory from this study. standard deviation of the dataset) to account for the different • Decomposition generally leads to increasing δ15N and scales of the three variables (δ13C, δ15N, and C/N). decreasing C/N. Although the slope is unknown, the The results of the PCA are summarized in table 5. typical direction is toward the upper left (lower PC1 Together, PC1 and PC2 capture 86 percent of the variability and higher PC2). Any shift in this direction will make in the dataset. The principal components plot is shown in seston, suspended sediment, WWTF effluent particulate, figure 14. The black vectors (arrows) in that figure originate at periphyton, duckweed, and bryozoan less similar to bed the mean value for the entire dataset and point in the direction sediments. associated with each of the individual variables, δ13C, 15 13 δ N, and C/N. Note that the δ C vector is pointing toward • Increasing amounts of phytoplankton are associated 13 increasing negative values (decreasing δ C ) because that with increasingly negative δ13C and positive δ15N and, direction is most pertinent to this discussion. therefore, cannot be a major source to bed sediment. Examination of the principal components graph (fig. 14) The bed sediment samples from late-summer-1999 from leads to the following observations, several of which were downstream of RM 26.9 shift slightly toward increasing noted earlier: phytoplankton, indicating that phytoplankton probably • Bryozoan, duckweed, and WWTF effluent particulate contributes a small amount of organic material to bed do not plot at locations similar to bed sediments and, sediment during certain times in the lower reaches of the therefore, probably are not major sources of organic river. matter to bed sediment. • Suspended sediment and seston have similar • Several soil samples plot in locations similar to those of characteristics, with seston showing an increased bed sediment, suggesting that soil may contribute organic influence from phytoplankton. Some suspended sediment material to bed sediment or that the organic material in samples are similar to bed sediment and soil, but others soil and bed sediments have a common source. are clearly affected by the presence of phytoplankton.

Table 5. Results of principal components analysis.

Proportion Eigenvectors Equation to calculate PC using original units Principal (loadings) PC = A * 13C + B * 15N + C * C/N + D of variance i i δ i δ i i component (percent) 13 15 δ C δ N C/N Ai Bi Ci Di 1 (PC1) 64 0.529 -0.619 0.580 0.1545 -0.1876 0.03455 5.01 2 (PC2) 22 0.811 0.169 -0.560 0.2369 0.05119 -0.03332 7.33 22 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

The principal components plot also enables a qualitative δ15N, and C/N values of bed sediment. Bed sediment samples examination of the effect of mixing several sources. For plot farther to the upper right than most of the potential source example, a mixture of WWTF effluent particulate and materials except soil and two unusual periphyton samples. terrestrial plant litter mathematically could lead to the Erosional and transport processes throughout the drainage observed bed sediment pattern. This mixture, however, is basin make soil a likely potential source of organic matter not realistic because not all bed sediments were collected in bed sediment. The possibility that some unusual types of downstream of WWTFs. In general, the bed sediment samples periphyton could be present in sufficient quantity to create a plot in a region that makes it unlikely that extensive mixtures mixture resembling bed sediment, however, is remote. of the potential source substances could account for the δ13C,

Increasing δ15N

0 Principal component 2

-1 Potential decomposition trend for terrestrial Increasing vegetation phytoplankton population Increasing C/N -2

Decreasing δ13C

-3

-4 -5 -4 -3 -2 -1 0 1 2 3 4 5 Principal component 1

EXPLANATION Bed sediment without Late-Summer-99 Decomposed terrestrial detritus Bed sediment Late-Summer-99 Periphyton Bryozoan Seston (80–202 µm) Coniferous litter Soil Deciduous litter Suspended sediment Duckweed Woody material Decomposed duckweed WWTF effluent particulate

Figure 14. Results of a principal components analysis of δ13C, δ15N, and C/N data for samples taken from the Tualatin River basin, Oregon. [WWTF = Wastewater Treatment Facility].

tac10-0486_fig14 Summary and Conclusions 23

Summary and Conclusions The δ13C, δ15N, and C/N for samples of soil and decomposed terrestrial organic matter closely resembled Isotopic composition of carbon and nitrogen and C/N results for bed sediments. Although soil may be a direct source ratios were used to assess the potential contribution of various of organic matter to bed sediment, terrestrial plant material sources of organic matter to bed sediment in the Tualatin likely is a source of organic matter to both bed sediments River. Samples of bed sediment, suspended sediment, and and soils. Deciduous litter, woody material, and coniferous 13 seston (suspended particulate material, including plankton litter have δ C values that match soils and bed sediments 15 and organic detritus) in the Tualatin River were collected well. Although the δ N and C/N ratios for fresh leaf litter 15 during five sampling events in 1998–2000. During the same and twigs do not match the δ N and C/N ratios for soils and time period, potential source materials such as soil, plant bed sediments, decomposition of those materials is expected 15 litter, duckweed, and wastewater treatment facility effluent to shift the δ N and C/N toward those of bed sediment, particulate were collected for comparison of their isotopic resulting in a good match. Furthermore, the basin produces a composition. considerable quantity of terrestrial plant litter which easily is Bed sediment δ15N was slightly lower in tributaries and transported to the stream network. It is consistent to conclude, in the upper reaches of the river and may indicate that the therefore, that soil and leaf litter probably are the primary organic matter in these areas is fresher, less decomposed, sources of organic matter to Tualatin River bed sediment. or more labile. Higher SOD rates have been measured in Monitoring and management plans that aim to improve the tributaries compared to the main stem Tualatin River, oxygen conditions in the river would be most successful supporting the hypothesis that this material may be more by concentrating on sources of soil, leaf litter, and other labile. No general trends in δ13C or C/N for bed sediment terrestrially derived organic materials to the river rather than with river location were observed. Bed sediment in the lower on the instream growth of algae. river, which is associated with the most phytoplankton growth, was not usually different from bed sediment farther upstream where less algae is present. Bed sediment collected from the Acknowledgments lower river in late summer (1999), however, did show a small difference, a likely influence of phytoplankton. The authors thank the following people for their Phytoplankton was evident in seston and suspended contributions to this work: Chauncey Anderson, Amy Brooks, 13 sediment samples and characterized by low δ C (< -32 Kurt Carpenter, Micelis Doyle, Wes Jarrell, Matt Johnston, 15 per mil), high δ N (>8 per mil), and low C/N (<12). The and Tammy Wood for assistance in sample collection; Renate increasing amount of phytoplankton in the more downstream Ryan for assistance in not only sample collection but also river samples was reflected in distinct trends in the isotopic processing and freeze-drying; Carol Kendall and the graduate data and C/N ratios with river mile. The isotopic data for and post-doctoral students in her stable isotopes laboratory for samples that contained the most phytoplankton did not the many hours spent analyzing samples from this study and resemble bed sediment. Decomposition of organic matter their help in interpreting the laboratory data; and Jan Miller 15 tends to decrease the C/N ratio and increase the δ N value, of Clean Water Services for helping to organize and fund further increasing the differences compared to bed sediment. the project. Finally, the authors are grateful to the group of Therefore, phytoplankton likely is not a major source of reviewers that provided helpful comments on this report. organic matter to bed sediment. Reductions in the size of the algal community, therefore, may have little effect on the rate of sediment oxygen demand. Compared to bed sediment, the nitrogen content was References Cited heavier (higher δ15N ) and/or the C/N ratio was lower for several types of samples, including duckweed, periphyton Bernasconi, S.M., Barbieri, A., and Simona, M., 1997, Carbon and wastewater treatment facility effluent particulate. Further and nitrogen isotope variations in sedimenting organic decomposition of these materials would tend to increase matter in Lake Lugano: Limnology and Oceanography, the δ15N and decrease the C/N, increasing their differences v. 42, no. 8, p. 1955–1765. compared to bed sediment. It is, therefore, unlikely that duckweed, periphyton, or wastewater treatment facility Edwards, T.K., and Glysson, G.D., 1999, Field methods for effluent are significant sources of organic matter to bed measurement of fluvial sediment: U.S. Geological Survey sediment. Periphyton samples exhibited δ13C values that Techniques of Water-Resources Investigations, book 3, spanned the widest range of any of the types of samples chap. C2, 89 p. collected for this study; the inconsistency of the δ13C of periphyton limits the use of δ13C as a tracer for this class of sample. 24 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

Finlay, J.C., and Kendall, C., 2007, Stable isotope tracing of Oregon Department of Environmental Quality, 2001, Tualatin temporal and spatial variability in organic matter sources to subbasin Total Maximum Daily Load (TMDL): Portland, freshwater ecosystems, in Michener, R.H., and Lajtha, K., Oregon, Oregon Department of Environmental Quality, eds., Stable Isotopes in Ecology and Environmental Science 165 p., accessed October 8, 2009, at http://www.deq.state. (2d ed.): Hoboken, N.J., Wiley-Blackwell, p. 283–333. or.us/wq/TMDLs/docs/willamettebasin/tualatin/tmdlwqmp. pdf. Helsel, D.R., and Hirsch, R.M., 1992, Statistical methods in water resources: Amsterdam, Elsevier Science Publishers, Rounds, S.A., and Doyle, M.C., 1997, Sediment oxygen 522 p. demand in the Tualatin River Basin, Oregon, 1992-1996: U.S. Geological Survey Water-Resources Investigations Homer, C., Dewitz, J., Fry, J., Coan, M., Hossain, N., Report 97-4103, 19 p. Larson, C., Herold, N., McKerrow, A., VanDriel, J.N., and Wickham, J., 2007, Completion of the 2001 National Rounds, S.A., Wood, T.M., and Lynch, D.D., 1999, Modeling Land Cover Database for the conterminous United States: discharge, temperature, and water quality in the Tualatin Photogrammetric Engineering and Remote Sensing, v. 73, River, Oregon: U.S. Geological Survey Water-Supply Paper no. 4, p. 337–341. 2465-B, 121 p. Kendall, C., Silva, S.R., and Kelly, V.J., 2001, Carbon and SAS Institute Inc., 1989, SAS/STAT® version 6.07.01, Cary, nitrogen isotopic compositions of particulate organic N.C. matter in four large river systems across the United States: Hydrological Processes, v. 15, no. 7, 1301–1346. (Also Tualatin River Flow Management Technical Committee, 2000, available at http://dx.doi.org/10.1002/hyp.216.) Annual data report for 1999: Clean Water Services and Oregon Water Resources Department, accessed October 9, Middelburg, J.J., and Nieuwenhuize, J., 1998, Carbon and 2009, at http://www.co.washington.or.us/Watermaster/ nitrogen stable isotopes in suspended matter and sediments SurfaceWater/upload/FlowReport-1999.pdf. from the Schelde Estuary: Marine Chemistry, v. 60, p. 217–225. U.S. Census Bureau, 2000, State and County QuickFacts: U.S. Census Bureau website, accessed October 6, 2009, at http:// Miller, J.C., and Miller, J.N., 1988, Statistics for analytical quickfacts.census.gov/qfd/states/41/41067.html. chemistry (2d ed.): New York, John Wiley and Sons, 227 p. Table 6 25

n 0 0 0 0 0 0 0 4 4 0 0 0 0 0 0 0 0 0 0 1-sf n 6 4 3 4 4 3 4 9 9 4 7 3 3 3 4 4 4 4 4 0.38 1.34 1.12 1.09 0.94 1.53 1.45 2.43 3.29 0.84 1.03 1.63 2.72 8.83 2.29 2.10 1.77 1.34 27.70 95%CI C/N atomic ratio 5.39 4.95 7.69 5.47 4.24 11.68 11.85 11.40 10.33 16.22 17.52 12.38 12.81 24.60 29.08 46.53 32.93 67.04 77.75 Mean

n 0 0 0 0 0 0 0 2 0 0 0 0 0 0 0 0 1 0 0 low-N n 6 4 3 4 4 3 4 9 9 4 7 3 4 3 4 4 4 4 4 N 15 δ 0.33 1.04 0.44 0.46 0.34 0.44 0.50 0.67 1.02 0.41 0.83 0.93 0.25 0.98 0.10 0.23 0.14 1.03 1.34 95%CI 9.34 5.80 6.90 6.82 7.38 4.93 4.32 3.79 5.44 5.08 2.19 -0.87 -0.20 -1.64 -0.55 -2.87 Mean 11.61 12.90 16.13 n 6 4 3 4 4 3 4 9 9 4 7 3 4 3 4 4 4 4 4 0.11 0.75 0.22 0.24 0.12 0.28 0.21 0.36 0.29 0.18 0.09 0.13 0.14 0.39 0.13 0.14 0.42 0.16 0.32 C 95%CI 13 δ Mean -35.03 -33.15 -18.42 -26.34 -29.44 -33.08 -27.95 -28.03 -27.52 -26.64 -26.06 -27.20 -30.41 -26.80 -29.50 -27.41 -26.48 -26.64 -35.36 Date 08-11-98 08-13-98 08-13-98 08-18-98 09-29-98 09-17-98 09-17-98 08-20-98 08-18-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 08-13-98 N) and C/N ratios for samples collected in the Tualatin River basin, Oregon. N) and C/N ratios for samples collected in the Tualatin WWTF, wastewater treatment facililty; µm, micrometer; na, not applicable] WWTF, 15 δ C, 13 Late-Summer 1998 δ – – – – – – – – Sample detail Species not identified Species not identified Duckweed sorted from mat Chehalis soil soil Wapato soil Woodburn Ash leaf litter Oregon Red Cedar litter Western Alder leaf litter Douglas Fir litter Douglas Fir twigs Sample type Seston, >80 μm Periphyton Periphyton Seston, >80 μm Duckweed Suspended sediment Suspended sediment Bed sediment Bed sediment Soil Soil Soil Leaf litter Coniferous litter Leaf litter Coniferous litter material Woody WWTF effluent particulate Bryozoan

Site name RM, river mile; n, number of splits used in calculation mean and confidence interval; 95% CI, 95-percent limit mean; low-N that contained less than Mean values and confidence intervals of stable isotope compositions ( (Stafford Road) (Stafford Road) (Stafford Road) (Stafford (Scholls) Road) (Stafford (Scholls) Swale and holding pond) River) Tualatin Bronson Creek) Swale and holding pond) (Cherry Grove) (Cherry Grove) 1 mi east of Cherry Grove) 1 mi east of Cherry Grove) Facility Treatment Road) (Stafford

Tualatin River at RM 5.5 Tualatin River at RM 5.5 Tualatin River at RM 20.3 Tualatin Henry Hagg Lake River at RM 24.5 Tualatin River at RM 5.5 Tualatin River at RM 26.9 Tualatin River at RM 5.5 Tualatin River at RM 26.9 Tualatin Jackson Bottom (between Miller Zurcher Farm (Fernhill Road near Oregon Graduate Institute (near Jackson Bottom (between Miller River at RM 67.8 Tualatin River at RM 67.8 Tualatin Road (north side, Valley Patton Road (north side, Valley Patton Wastewater Rock Creek River at RM 5.5 Tualatin ID 411 401 402 403 404 405 406 407 408 409 410 412 413 414 415 416 417 418 419 Abbreviations: Table 6. Table [ 1 micromole N; 1-sf n, number of splits in which the percent nitrogen value had only significant digit; 26 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

n 0 0 0 0 0 0 0 2 0 0 0 0 0 0 0 0 0 0 3 0 4 1-sf n 4 3 3 4 3 3 4 3 3 4 3 3 3 4 3 1 3 4 3 3 4 na 0.86 0.18 1.07 1.02 1.00 5.83 1.16 1.74 3.81 2.43 0.99 1.33 2.24 2.00 0.92 1.20 1.30 4.16 25.40 15.43 95%CI C/N atomic ratio 5.41 5.83 7.61 9.47 8.60 11.35 10.19 14.61 31.62 14.67 64.88 30.96 16.55 17.23 14.73 12.00 28.31 10.49 13.66 14.61 Mean 110.57

n 0 0 0 0 0 0 0 0 3 1 0 0 2 2 0 0 0 0 0 0 4 low-N n 4 3 3 4 3 3 4 2 3 4 3 3 3 4 3 1 3 4 3 3 4 N 15 δ na 0.48 0.53 0.63 0.93 0.81 0.48 0.52 3.01 3.34 0.75 0.75 0.60 0.57 0.91 0.70 0.81 0.35 0.61 0.48 0.63 95%CI 7.04 6.33 7.77 7.75 2.65 8.99 5.63 0.16 1.51 0.88 6.67 6.24 6.81 5.89 9.32 5.36 6.41 4.81 4.60 2.62 Mean 10.48 n 4 3 3 4 3 3 4 3 3 4 3 3 3 4 3 1 3 4 3 3 4 na 0.38 0.34 0.16 0.15 0.14 0.78 0.31 0.12 0.35 0.31 0.40 0.13 0.18 0.28 0.38 0.84 0.11 0.46 0.14 0.15 C 95%CI 13 δ Mean -29.06 -28.91 -30.46 -30.70 -28.65 -29.03 -32.24 -27.46 -27.25 -25.55 -27.06 -28.51 -28.27 -28.55 -27.51 -28.48 -26.45 -28.14 -26.74 -26.39 -27.15 Date 07-09-99 07-09-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-16-99 07-16-99 N) and C/N ratios for samples collected in the Tualatin River basin, Oregon.—Continued N) and C/N ratios for samples collected in the Tualatin WWTF, wastewater treatment facililty; µm, micrometer; na, not applicable] WWTF, 15 δ C, 13 Mid-Summer 1999 δ – – – – – – – – – – – – – – Sample detail duckweed mat duckweed mat river surface river surface duckweed mat Duckweed sorted from mat sorted from Twigs Cones sorted from Ash seed pods from Oregon Ash leaves from Oregon Duckweed sorted from mat sorted from Twigs Sample type Seston, >80 μm Seston, 80–202 μm Seston, >80 μm Seston, 80–202 μm Duckweed material Woody Suspended sediment Bed sediment Coniferous litter Leaf litter Leaf litter Seston, >80 μm Seston, 80–202 μm Suspended sediment Bed sediment Duckweed material Woody Suspended sediment Bed sediment Suspended sediment Bed sediment

Henry Hagg Lake Henry Hagg Lake River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 26.9 Tualatin River at RM 26.9 Tualatin River at RM 26.9 Tualatin River at RM 26.9 Tualatin River at RM 26.9 Tualatin River at RM 26.9 Tualatin River at RM 38.4 Tualatin River at RM 38.4 Tualatin Gales Creek at Old Highway 47 Gales Creek at Old Highway 47 1 2 3 4 5 6 7 8 ID 10 12 13 14 15 16 17 18 19 20 21 22 23 Abbreviations: Table 6. Table [ 1 micromole N; 1-sf n, number of splits in which the percent nitrogen value had only significant digit; Table 6 27

n 0 2 3 3 0 0 0 0 0 0 0 0 0 0 6 0 0 0 0 1-sf n 3 3 3 3 3 3 3 3 4 4 3 3 3 5 6 4 3 6 3 1.32 2.52 3.22 2.75 1.66 1.05 1.41 1.39 0.44 1.96 1.03 1.33 1.41 0.78 1.54 1.32 1.00 0.41 16.79 95%CI C/N atomic ratio 8.91 5.78 5.87 5.92 7.29 6.92 6.86 11.08 11.25 16.50 15.35 10.31 15.31 12.35 10.64 13.97 27.21 29.96 90.52 Mean

n 0 1 3 3 1 0 0 0 0 0 0 0 3 0 6 0 0 0 3 low-N n 3 2 3 3 3 3 3 3 4 3 3 3 3 3 6 4 3 6 3 N 15 δ 0.36 0.51 0.74 0.69 1.69 0.69 0.73 0.63 0.57 1.17 0.55 0.54 1.01 0.82 0.29 0.33 0.39 0.15 1.03 95%CI 6.17 4.30 4.10 2.71 5.22 5.81 9.11 9.01 9.22 5.74 6.87 8.25 9.10 7.29 5.48 3.20 6.90 2.30 0.72 Mean n 3 3 3 3 3 3 3 3 4 4 3 3 3 4 6 4 3 6 3 0.18 0.46 0.53 0.33 0.31 0.13 0.18 0.23 0.05 0.72 0.22 0.20 0.33 0.12 0.22 0.33 0.06 1.11 0.05 C 95%CI 13 δ Mean -29.59 -26.92 -27.63 -27.06 -29.21 -27.98 -35.41 -37.46 -37.64 -27.41 -17.36 -35.05 -34.99 -34.98 -28.16 -28.50 -29.85 -27.82 -26.55 Date 07-16-99 07-16-99 07-16-99 07-16-99 07-16-99 07-16-99 07-16-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 N) and C/N ratios for samples collected in the Tualatin River basin, Oregon.—Continued N) and C/N ratios for samples collected in the Tualatin WWTF, wastewater treatment facililty; µm, micrometer; na, not applicable] WWTF, 15 δ C, 13 δ Mid-Summer 1999—Continued – – – – – – – – – – – – – – Sample detail duckweed mat duckweed mat Spirogyra Unsorted duckweed mat Duckweed sorted from mat sorted from Twigs Cones sorted from Sample type Suspended sediment Bed sediment Suspended sediment Bed sediment Suspended sediment Bed sediment Suspended sediment Seston, >80 μm Seston, 80–202 μm Bed sediment Periphyton Seston, >80 μm Seston, 80–202 μm Suspended sediment Bed sediment Duckweed Duckweed material Woody Coniferous litter

Site name RM, river mile; n, number of splits used in calculation mean and confidence interval; 95% CI, 95-percent limit mean; low-N that contained less than Mean values and confidence intervals of stable isotope compositions ( (Dilley) (Dilley) Road) (Stafford Road) (Stafford Road) (Stafford Road) (Stafford Road) (Stafford (Cook Park) (Cook Park) (Cook Park) (Cook Park) (Cook Park) (Cook Park) (Cook Park) (Cook Park)

Dairy Creek at Highway 8 Dairy Creek at Highway 8 River at RM 58.8 Tualatin River at RM 58.8 Tualatin Rock Creek at Highway 8 Rock Creek at Highway 8 River at RM 5.5 Tualatin River at RM 5.5 Tualatin River at RM 5.5 Tualatin River at RM 5.5 Tualatin River at RM 5.5 Tualatin River at RM 9.9 Tualatin River at RM 9.9 Tualatin River at RM 9.9 Tualatin River at RM 9.9 Tualatin River at RM 9.9 Tualatin River at RM 9.9 Tualatin River at RM 9.9 Tualatin River at RM 9.9 Tualatin ID 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 Abbreviations: Table 6. Table [ 1 micromole N; 1-sf n, number of splits in which the percent nitrogen value had only significant digit; 28 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

n 0 4 0 0 0 4 0 0 0 0 3 0 0 0 0 4 0 1-sf n 3 4 3 3 4 4 4 3 7 3 3 2 4 6 3 4 3 3.08 3.14 1.24 1.45 1.16 2.12 0.87 1.63 0.53 1.27 4.70 0.54 1.29 1.02 4.04 4.00 12.02 95%CI C/N atomic ratio 7.61 7.65 6.96 9.06 4.37 29.92 14.29 13.77 12.35 10.07 17.02 91.83 13.52 13.06 14.43 14.58 17.42 Mean

n 0 4 0 3 0 4 0 0 0 3 1 4 0 6 3 4 0 low-N n 3 4 3 3 4 4 3 3 0 3 3 4 4 6 3 4 3 N 15 δ na 1.12 1.71 0.99 1.15 1.11 1.59 1.31 0.64 0.94 0.62 0.47 1.42 1.00 0.45 0.78 0.88 95%CI na 1.38 5.29 5.57 5.55 7.58 5.98 5.20 4.56 4.82 6.26 5.37 3.57 3.56 Mean 10.58 10.88 12.19 n 3 3 3 3 4 4 4 3 7 3 3 4 4 6 3 4 3 0.22 0.28 0.21 0.26 0.13 1.00 0.68 0.32 0.39 0.49 0.87 0.62 0.54 0.64 0.47 0.18 0.30 C 95%CI 13 δ Mean -26.10 -27.12 -34.88 -34.83 -35.82 -27.84 -29.79 -34.42 -29.36 -30.45 -27.18 -27.01 -29.01 -28.74 -28.41 -28.01 -27.99 Date 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 N) and C/N ratios for samples collected in the Tualatin River basin, Oregon.—Continued N) and C/N ratios for samples collected in the Tualatin WWTF, wastewater treatment facililty; µm, micrometer; na, not applicable] WWTF, 15 δ C, 13 δ Mid-Summer 1999—Continued – – – – – – – – – – Sample detail slump edge 24 hours sample sediment 24 hours anoxic fractions A-horizon from bank with Bottom of slump at water Fraction that settled after Aphanizomenon floating on removed from bed Twigs Fraction that settled after 10 cm, both oxic and Top Sample type Soil Soil Seston, >80 μm Seston, 80–202 μm Suspended sediment Bed sediment Suspended sediment Seston, >80 μm Seston, >80 μm Seston, 80–202 μm Bed sediment material Woody Suspended sediment Seston, >80 μm Seston, 80–202 μm Bed sediment Bed sediment

Site name RM, river mile; n, number of splits used in calculation mean and confidence interval; 95% CI, 95-percent limit mean; low-N that contained less than Mean values and confidence intervals of stable isotope compositions ( (Cook Park) (Cook Park) (Boones Ferry Bridge) (Boones Ferry Bridge) (Boones Ferry Bridge) (Boones Ferry Bridge) Bridge) Bridge) Bridge) Bridge) Bridge) Bridge) City Park City Park City Park City Park City Park

Tualatin River at RM 9.9 Tualatin River at RM 9.9 Tualatin River at RM 8.7 Tualatin River at RM 8.7 Tualatin River at RM 8.7 Tualatin River at RM 8.7 Tualatin River at RM 16.2 (Elsner Tualatin River at RM 16.2 (Elsner Tualatin River at RM 16.2 (Elsner Tualatin River at RM 16.2 (Elsner Tualatin River at RM 16.2 (Elsner Tualatin River at RM 16.2 (Elsner Tualatin Fanno Creek at Durham Fanno Creek at Durham Fanno Creek at Durham Fanno Creek at Durham Fanno Creek at Durham ID 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 Abbreviations: Table 6. Table [ 1 micromole N; 1-sf n, number of splits in which the percent nitrogen value had only significant digit; Table 6 29

n 0 0 0 0 0 0 0 0 0 0 0 0 0 3 0 3 1-sf n 3 3 3 2 5 3 3 3 3 3 3 3 6 3 3 3 2.90 9.59 4.13 5.21 4.19 1.21 1.10 1.58 1.41 7.82 3.89 2.20 0.90 1.47 1.42 1.25 95%CI C/N atomic ratio 8.00 6.14 5.31 5.57 11.02 11.14 33.94 51.42 22.21 19.95 46.79 17.40 66.10 37.02 31.90 10.14 Mean

n 0 0 0 0 0 0 0 0 0 0 0 0 0 3 0 1 low-N n 3 3 3 4 5 3 3 3 3 3 3 3 6 3 3 3 N 15 δ 0.53 0.54 0.74 0.37 0.44 0.31 0.39 1.02 0.90 0.98 1.09 1.12 0.84 0.71 0.38 0.38 95%CI 4.46 3.17 4.92 0.88 0.80 4.56 5.50 4.81 6.12 2.02 9.26 6.60 5.06 -2.53 -2.62 Mean 10.46 n 3 3 3 3 5 3 3 2 3 3 3 3 6 3 3 3 0.17 0.10 0.43 0.91 0.95 0.11 0.15 0.13 0.31 0.48 0.29 0.29 1.13 0.10 0.09 0.17 C 95%CI 13 δ Mean -29.60 -26.80 -27.85 -27.29 -26.80 -39.69 -34.14 -27.87 -27.21 -25.06 -24.91 -27.83 -24.77 -26.01 -33.86 -28.41 Date 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-19-99 07-21-99 08-04-99 08-04-99 08-04-99 08-04-99 07-14-99 07-14-99 07-21-99 07-21-99 N) and C/N ratios for samples collected in the Tualatin River basin, Oregon.—Continued N) and C/N ratios for samples collected in the Tualatin WWTF, wastewater treatment facililty; µm, micrometer; na, not applicable] WWTF, 15 δ C, 13 δ Mid-Summer 1999—Continued – – Sample detail in stream stream twigs in stream trail trail planted litter suspended after 24 hours suspended after 24 hours Redtwig dogwood leaves Ash leaves in Oregon Decomposed leaves & Ash leaves from Oregon Ash seed pods from Oregon Cladophera Cladophera not tilled, field, Agricultural Chehalis soil Ash leaves Oregon Red Cedar Western Mixed Mixed Douglas Fir litter Fraction remaining Fraction remaining Sample type detritus Leaf litter Leaf litter Decomposed terrestrial Leaf litter Leaf litter Periphyton Periphyton Soil Soil Leaf litter Coniferous litter Coniferous litter WWTF effluent particulate WWTF effluent particulate Suspended sediment Suspended sediment

Site name RM, river mile; n, number of splits used in calculation mean and confidence interval; 95% CI, 95-percent limit mean; low-N that contained less than Mean values and confidence intervals of stable isotope compositions ( City Park City Park City Park City Park City Park City Park (Basalt sill) and Highway 99W) Swale and holding pond) Swale and holding pond) Facility Treatment Facility Bridge) City Park

Fanno Creek at Durham Fanno Creek at Durham Fanno Creek at Durham Fanno Creek at Durham Fanno Creek at Durham Fanno Creek at Durham River at RM 9.4 Tualatin Onion Flat (Cipole Road Jackson Bottom (between Miller Jackson Bottom (between Miller Nature Park Tualatin Nature Park Tualatin Wastewater Rock Creek Treatment Wastewater Durham River at RM 16.2 (Elsner Tualatin Fanno Creek at Durham ID 60 61 62 63 64 65 67 68 69 70 71 72 73 74 76 77 Abbreviations: Table 6. Table [ 1 micromole N; 1-sf n, number of splits in which the percent nitrogen value had only significant digit; 30 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

n 0 0 2 1 0 0 0 4 0 0 0 0 0 4 0 0 0 0 0 0 1-sf n 3 3 3 8 3 3 4 3 3 4 3 3 5 4 3 3 4 3 3 4 1.54 1.37 0.90 1.03 1.23 1.23 1.04 1.51 1.13 1.62 2.31 2.21 1.38 1.17 1.22 1.17 1.24 0.99 0.90 0.89 95%CI C/N atomic ratio 4.47 6.16 8.24 8.85 8.71 11.91 11.86 13.92 16.13 17.26 10.03 12.63 14.84 15.86 14.75 10.05 10.75 16.45 14.03 14.47 Mean

n 0 0 0 0 0 0 0 4 0 0 0 0 0 4 0 1 4 0 2 0 low-N n 3 3 3 8 3 3 4 4 3 4 3 3 4 4 2 3 4 3 3 4 N 15 δ 0.79 0.50 0.43 0.10 0.59 0.60 0.41 1.48 0.59 0.30 0.93 0.77 0.44 0.77 2.60 0.37 0.40 0.36 0.52 0.32 95%CI 8.46 6.58 4.12 3.95 8.05 7.59 7.35 5.16 4.28 4.17 5.88 6.73 5.49 5.37 7.08 5.96 6.69 6.05 6.38 5.75 Mean n 3 3 3 8 3 3 4 4 3 4 3 3 5 4 3 3 4 3 3 4 0.16 0.16 0.28 0.46 0.62 0.36 0.14 0.74 0.13 0.39 0.41 1.35 0.35 0.27 0.98 0.51 0.53 0.08 0.17 0.13 C 95%CI 13 δ Mean -30.18 -31.22 -31.08 -27.88 -33.19 -33.00 -34.06 -30.58 -35.50 -29.53 -30.86 -30.80 -29.30 -28.72 -32.27 -31.07 -31.41 -28.72 -28.93 -29.00 Date 09-11-99 09-11-99 09-11-99 09-11-99 09-11-99 09-10-99 09-10-99 09-10-99 09-10-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-15-99 09-15-99 N) and C/N ratios for samples collected in the Tualatin River basin, Oregon.—Continued N) and C/N ratios for samples collected in the Tualatin WWTF, wastewater treatment facililty; µm, micrometer; na, not applicable] WWTF, 15 δ C, 13 Late-Summer 1999 δ – – – – – – – – – – – – – – – – – – Sample detail Cladophera Anoxic blue-gray fraction Sample type Seston, >80 μm Seston, 80–202 μm Suspended sediment Bed sediment Seston, >80 μm Seston, 80–202 μm Suspended sediment Bed sediment Periphyton Seston, >80 μm Seston, 80–202 μm Suspended sediment Bed sediment Bed sediment Suspended sediment Seston, >80 μm Seston, 80–202 μm Bed sediment Seston, >80 μm Seston, 80–202 μm

Site name RM, river mile; n, number of splits used in calculation mean and confidence interval; 95% CI, 95-percent limit mean; low-N that contained less than Mean values and confidence intervals of stable isotope compositions ( (Rood Bridge) (Rood Bridge) (Cook Park) (Cook Park) (Cook Park) (Cook Park) (Basalt sill) Bridge) Bridge) Bridge) Bridge) (Scholls) (Scholls)

Henry Hagg Lake Henry Hagg Lake River at RM 38.4 Tualatin River at RM 38.4 Tualatin River at RM 9.9 Tualatin River at RM 9.9 Tualatin River at RM 9.9 Tualatin River at RM 9.9 Tualatin River at RM 9.4 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 16.2 (Elsner Tualatin River at RM 16.2 (Elsner Tualatin River at RM 16.2 (Elsner Tualatin River at RM 16.2 (Elsner Tualatin River at RM 26.9 Tualatin River at RM 26.9 Tualatin ID 111 110 112 113 114 115 116 117 118 119 101 102 103 104 105 106 107 108 109 120 Abbreviations: Table 6. Table [ 1 micromole N; 1-sf n, number of splits in which the percent nitrogen value had only significant digit; Table 6 31

n 0 4 0 0 0 0 3 5 3 0 3 4 2 4 6 4 6 1-sf n 4 7 3 4 3 3 3 5 5 6 3 4 3 5 6 4 6 0.84 1.50 1.18 1.23 1.46 1.21 2.46 1.51 1.76 2.39 2.55 2.24 5.73 1.27 1.44 2.33 1.19 95%CI C/N atomic ratio 9.54 5.69 5.31 14.47 17.45 13.05 12.12 16.19 17.83 32.43 15.36 27.11 33.00 15.19 16.51 17.58 16.11 Mean

n 0 1 0 0 0 0 0 5 3 3 2 4 2 4 4 4 6 low-N n 3 5 3 4 2 3 3 5 3 6 3 4 2 4 6 4 6 N 15 δ 1.07 0.21 1.29 1.39 2.39 0.57 1.38 1.06 0.51 0.67 1.70 0.42 0.80 0.40 0.69 0.44 0.53 95%CI 7.12 5.66 6.29 4.89 4.05 4.29 4.83 3.86 4.07 3.60 3.87 3.61 4.59 4.34 Mean 12.79 16.71 17.36 n 4 7 3 4 3 3 3 5 5 6 3 4 3 5 6 4 6 1.23 0.14 0.30 0.08 0.50 0.08 0.85 0.46 0.35 0.18 0.42 0.31 1.91 0.64 0.72 0.79 0.71 C 95%CI 13 δ Mean -28.47 -29.55 -33.68 -37.66 -38.23 -29.42 -30.71 -32.01 -31.01 -27.64 -30.96 -28.55 -28.88 -31.57 -29.55 -32.51 -31.66 Date 09-15-99 09-15-99 09-15-99 09-15-99 09-15-99 09-15-99 02-08-00 02-04-00 02-04-00 02-04-00 02-04-00 02-04-00 02-07-00 02-07-00 02-07-00 02-07-00 02-07-00 N) and C/N ratios for samples collected in the Tualatin River basin, Oregon.—Continued N) and C/N ratios for samples collected in the Tualatin WWTF, wastewater treatment facililty; µm, micrometer; na, not applicable] WWTF, 15 δ Winter 2000 C, 13 δ Late-Summer 1999—Continued – – – – – – – – – – – – – – – – Sample detail Woody debris removed Woody Sample type Suspended sediment Bed sediment Suspended sediment Seston, >80 μm Seston, 80–202 μm Bed sediment Suspended sediment Suspended sediment Suspended sediment Bed sediment Suspended sediment Bed sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment

Site name RM, river mile; n, number of splits used in calculation mean and confidence interval; 95% CI, 95-percent limit mean; low-N that contained less than Mean values and confidence intervals of stable isotope compositions ( (Scholls) (Scholls) Road) (Stafford Road) (Stafford Road) (Stafford Road) (Stafford (Rood Bridge) Road) (Stafford (Scholls) (Scholls) Bridge) Bridge) (Dilley)

Tualatin River at RM 26.9 Tualatin River at RM 26.9 Tualatin River at RM 5.5 Tualatin River at RM 5.5 Tualatin River at RM 5.5 Tualatin River at RM 5.5 Tualatin River at RM 38.4 Tualatin River at RM 5.5 Tualatin River at RM 26.9 Tualatin River at RM 26.9 Tualatin River at RM 16.2 (Elsner Tualatin River at RM 16.2 (Elsner Tualatin Gales Creek at Old Highway 47 Dairy Creek at Highway 8 River at RM 58.8 Tualatin Rock Creek at Highway 8 Fanno Creek at Durham Road ID 211 121 122 123 124 125 126 201 202 203 204 206 207 208 209 210 212 Abbreviations: Table 6. Table [ 1 micromole N; 1-sf n, number of splits in which the percent nitrogen value had only significant digit; 32 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

n 0 0 0 0 0 0 0 3 0 0 0 0 0 3 0 0 0 0 0 0 1-sf n 4 4 4 3 3 4 3 3 4 4 3 3 3 3 3 4 3 3 3 3 0.43 0.56 0.55 1.23 0.22 0.22 0.35 0.74 0.54 0.32 0.20 0.27 0.10 0.94 1.37 0.40 0.18 0.49 0.56 1.08 95%CI C/N atomic ratio 8.87 8.95 7.82 9.66 9.56 7.70 11.49 11.56 10.07 15.81 15.79 12.73 10.17 15.49 15.27 15.43 10.20 15.09 12.93 12.99 Mean

n 0 1 0 0 0 0 0 3 0 0 0 0 3 3 0 0 0 0 0 0 low-N n 4 4 4 3 3 4 3 3 3 4 3 3 3 3 3 4 3 3 3 3 N 15 δ 0.24 0.14 0.18 0.49 0.49 0.48 0.08 0.62 1.63 0.27 0.13 0.64 1.08 0.34 0.93 0.69 0.12 0.29 1.35 0.25 95%CI 3.38 3.03 5.39 4.06 9.02 8.68 9.50 5.27 7.08 6.81 9.99 9.15 5.92 8.04 7.63 8.77 5.47 Mean 11.46 10.63 10.25 n 4 4 4 3 3 4 3 3 4 4 3 3 3 3 3 4 3 3 3 3 0.17 0.80 0.13 0.12 0.20 0.15 0.17 0.40 0.88 0.04 0.18 0.06 0.97 0.16 0.29 0.02 0.32 0.20 0.48 0.34 C 95%CI 13 δ Mean -26.37 -26.34 -31.14 -28.12 -32.55 -32.56 -35.07 -28.67 -28.73 -36.21 -32.61 -32.64 -35.22 -28.81 -29.61 -29.77 -32.55 -28.29 -30.24 -29.21 Date 06-03-00 06-03-00 06-05-00 06-05-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-05-00 06-05-00 06-05-00 06-05-00 06-02-00 06-02-00 N) and C/N ratios for samples collected in the Tualatin River basin, Oregon.—Continued N) and C/N ratios for samples collected in the Tualatin WWTF, wastewater treatment facililty; µm, micrometer; na, not applicable] WWTF, 15 δ C, 13 δ Early-Summer 2000 – – – – – – – – – – – – – – – – – – Sample detail Decomposed duckweed Cladophera Sample type Seston, >80 μm Seston, 80–202 μm Suspended sediment Bed sediment Seston, >80 μm Seston, 80–202 μm Suspended sediment Bed sediment Duckweed Periphyton Seston, >80 μm Seston, 80–202 μm Suspended sediment Bed sediment Seston, >80 μm Seston, 80–202 μm Suspended sediment Bed sediment Suspended sediment Seston, >80 μm

Site name RM, river mile; n, number of splits used in calculation mean and confidence interval; 95% CI, 95-percent limit mean; low-N that contained less than Mean values and confidence intervals of stable isotope compositions ( (Rood Bridge) (Rood Bridge) (Cook Park) (Cook Park) (Cook Park) (Cook Park) (Cook Park) (Basalt sill) (Boones Ferry Bridge) (Boones Ferry Bridge) (Boones Ferry Bridge) (Boones Ferry Bridge) Bridge) Bridge)

Henry Hagg Lake Henry Hagg Lake River at RM 38.4 Tualatin River at RM 38.4 Tualatin River at RM 9.9 Tualatin River at RM 9.9 Tualatin River at RM 9.9 Tualatin River at RM 9.9 Tualatin River at RM 9.9 Tualatin River at RM 9.4 Tualatin River at RM 8.7 Tualatin River at RM 8.7 Tualatin River at RM 8.7 Tualatin River at RM 8.7 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 16.2 (Elsner Tualatin River at RM 16.2 (Elsner Tualatin ID 311 301 302 303 304 305 306 307 308 309 310 312 313 314 315 316 317 318 319 320 Abbreviations: Table 6. Table [ 1 micromole N; 1-sf n, number of splits in which the percent nitrogen value had only significant digit; Table 6 33

n 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1-sf n 3 3 4 3 3 4 3 3 3 3 3 3 4 3 3 4 3 3 3 4 0.15 1.27 0.30 0.25 0.69 1.32 0.44 0.02 0.13 0.57 1.20 3.63 0.39 3.56 3.36 2.05 1.35 1.27 1.47 0.08 95%CI C/N atomic ratio 6.94 9.48 7.51 7.14 9.22 9.68 8.94 7.71 8.08 10.99 15.17 17.79 17.81 10.63 12.64 10.50 13.10 18.09 16.92 17.31 Mean

n 2 0 2 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 low-N n 3 3 4 3 3 4 3 3 3 4 3 3 4 3 3 4 3 3 3 4 N 15 δ 0.77 0.13 0.57 1.47 0.08 0.27 0.29 0.22 0.10 0.23 0.44 0.29 0.20 0.21 0.02 0.26 0.15 0.14 0.03 0.03 95%CI 5.22 6.23 5.55 7.05 5.26 5.77 3.02 1.72 4.64 2.48 3.71 3.69 4.64 5.61 5.56 3.54 Mean 10.37 12.10 13.58 13.74 n 3 3 4 3 3 4 3 3 3 4 3 3 4 3 3 4 3 3 3 4 0.18 0.44 0.13 0.07 0.66 0.55 0.44 0.23 0.20 0.16 0.10 0.23 0.59 0.17 0.14 0.11 0.13 0.15 0.29 0.22 C 95%CI 13 δ Mean -31.62 -27.93 -28.93 -29.11 -31.13 -27.80 -33.51 -37.81 -37.99 -28.15 -29.72 -27.61 -30.62 -27.77 -31.34 -27.77 -31.09 -32.01 -28.79 -42.84 Date 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 N) and C/N ratios for samples collected in the Tualatin River basin, Oregon.—Continued N) and C/N ratios for samples collected in the Tualatin WWTF, wastewater treatment facililty; µm, micrometer; na, not applicable] WWTF, 15 δ C, 13 δ Early-Summer 2000—Continued – – – – – – – – – – – – – – – – – – Sample detail Grass growing in stream Species not identified Sample type Seston, 80–202 μm Bed sediment Seston, >80 μm Seston, 80–202 μm Suspended sediment Bed sediment Suspended sediment Seston, >80 μm Seston, 80–202 μm Bed sediment Suspended sediment Bed sediment Suspended sediment Bed sediment Suspended sediment Bed sediment Grass Suspended sediment Bed sediment Periphyton Site name RM, river mile; n, number of splits used in calculation mean and confidence interval; 95% CI, 95-percent limit mean; low-N that contained less than Mean values and confidence intervals of stable isotope compositions ( Bridge) Bridge) (Scholls) (Scholls) (Scholls) (Scholls) Road) (Stafford Road) (Stafford Road) (Stafford Road) (Stafford (Dilley) (Dilley)

Tualatin River at RM 16.2 (Elsner Tualatin River at RM 16.2 (Elsner Tualatin River at RM 26.9 Tualatin River at RM 26.9 Tualatin River at RM 26.9 Tualatin River at RM 26.9 Tualatin River at RM 5.5 Tualatin River at RM 5.5 Tualatin River at RM 5.5 Tualatin River at RM 5.5 Tualatin Gales Creek at Old Highway 47 Gales Creek at Old Highway 47 River at RM 58.8 Tualatin River at RM 58.8 Tualatin Dairy Creek at Highway 8 Dairy Creek at Highway 8 Dairy Creek at Highway 8 Rock Creek at Highway 8 Rock Creek at Highway 8 Rock Creek at Highway 8 ID 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 Abbreviations: Table 6. Table [ 1 micromole N; 1-sf n, number of splits in which the percent nitrogen value had only significant digit; 34 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

n 0 0 0 2 2 1-sf n 3 3 4 3 3 2.41 0.68 1.40 2.83 0.89 95%CI C/N atomic ratio 8.86 8.04 7.44 23.13 13.00 Mean

n 0 0 0 2 0 low-N n 3 3 4 3 3 N 15 δ 0.07 0.46 0.19 0.21 0.60 95%CI 5.00 4.43 4.13 7.15 Mean 10.14 n 3 3 4 3 3 1.24 0.18 0.49 0.77 1.18 C 95%CI 13 δ Mean -28.92 -31.82 -28.58 -27.41 -27.94 Date 05-31-00 05-31-00 05-31-00 06-01-00 06-01-00 N) and C/N ratios for samples collected in the Tualatin River basin, Oregon.—Continued N) and C/N ratios for samples collected in the Tualatin WWTF, wastewater treatment facililty; µm, micrometer; na, not applicable] WWTF, 15 δ C, 13 δ Early-Summer 2000—Continued – – – – Sample detail plant material in stream Decomposed non-woody Sample type detritus Decomposed terrestrial Suspended sediment Bed sediment WWTF effluent particulate WWTF effluent particulate

Rock Creek at Highway 8 Fanno Creek at Durham Fanno Creek at Durham Wastewater Rock Creek Treatment Wastewater Durham ID 341 342 343 344 345 Abbreviations: Table 6. Table [ 1 micromole N; 1-sf n, number of splits in which the percent nitrogen value had only significant digit; Appendix A 35

Appendix A. 36 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

E E E

C/N qualifier 3.86 4.86 5.04 4.80 5.00 5.08 4.91 9.83 9.51 9.85 9.36 8.01 9.17 8.42 6.45 6.64 6.20 6.81 C/N 12.44 12.36 12.76 30.02 25.91 25.38 12.37 12.00 13.36 83.38 104.6 N

L L 15 δ qualifier The Acidified code is either The N 7.54 6.76 6.86 6.99 6.58 6.02 6.40 7.50 7.93 7.88 8.05 8.35 6.80 7.81 2.75 2.57 2.64 9.03 8.93 8.99 9.02 6.33 4.94 2.08 15 — -0.16 10.61 10.37 10.47 δ C 13 δ -28.87 -29.37 -28.79 -29.20 -28.70 -28.97 -29.05 -30.39 -30.56 -30.43 -30.55 -30.79 -30.77 -30.67 -28.57 -28.65 -28.72 -28.54 -29.29 -29.26 -31.92 -32.36 -32.27 -32.41 -27.39 -27.50 -27.50 -27.37 -27.35 A A A A A A A A A A A A A A A A A A A A A A U U U U U U U Acidified

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 rep Lab A A B C A B C A B C A B B C A B C A B C A B B C A B C A B split Sample Date 07-09-99 07-09-99 07-09-99 07-09-99 07-09-99 07-09-99 07-09-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 — — — — — — — — — — — — — — — — — — — — — Sample detail duckweed mat duckweed mat duckweed mat duckweed mat duckweed mat Duckweed sorted from mat Duckweed sorted from mat Duckweed sorted from mat sorted from Twigs sorted from Twigs sorted from Twigs Cones sorted from Cones sorted from N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split samples. N) and C/N ratios for samples collected from the Tualatin 15 N qualifier is listed as L if the total nitrogen mass in the sample was less than 1 micromole. The C/N qualifier is listed as E if the percent L if the total nitrogen mass in sample was less than 1 micromole. N qualifier is listed as δ 15 C, Sample type 13 δ RM, river mile; —, no result or sample detail; cm, centimeter] Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, 80–202 μm Seston, 80–202 μm Seston, 80–202 μm Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, 80–202 μm Seston, 80–202 μm Seston, 80–202 μm Seston, 80–202 μm Duckweed Duckweed Duckweed material Woody material Woody material Woody Suspended sediment Suspended sediment Suspended sediment Suspended sediment Bed sediment Bed sediment Bed sediment Coniferous litter Coniferous litter Abbreviations: Site name Values of stable isotope compositions ( Values

Henry Hagg Lake Henry Hagg Lake Henry Hagg Lake Henry Hagg Lake Henry Hagg Lake Henry Hagg Lake Henry Hagg Lake River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin 1 1 1 1 2 2 3 3 3 4 4 4 4 5 5 5 6 6 6 7 7 7 7 8 8 8 ID 10 10 Appendix A. [Sample splits are marked with letter codes (A, B, C, etc) simply to label the replicates. Lab Rep is replicate number (0, 1, 2, for analyses performed on each sample split. The δ The δ values are in per mil. for acidified or U unacidified. A nitrogen result had only one significant digit. Appendix A. 37

C/N qualifier 8.59 8.64 7.72 7.54 C/N 11.80 96.36 44.30 66.21 57.21 54.73 24.90 26.83 27.89 15.40 13.55 13.59 14.91 14.57 14.84 12.40 13.68 10.28 24.79 24.11 23.90 N

L L L L L L 15 δ qualifier N 1.61 1.02 2.00 1.41 1.02 0.98 0.65 6.38 6.89 6.74 6.01 6.20 6.51 6.27 6.28 7.26 7.40 5.95 6.19 5.52 9.32 5.76 5.38 4.94 15 -1.43 δ C 13 δ -27.03 -25.51 -25.83 -25.29 -25.56 -27.08 -27.27 -26.84 -28.50 -28.59 -28.45 -28.37 -28.25 -28.18 -28.33 -28.47 -28.80 -28.60 -27.28 -27.59 -27.67 -28.48 -25.92 -26.67 -26.75 A A A A A A A A A A A A A A A A A A A A A A A A A Acidified

0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 rep Lab C A B C C A B C A B C A B C A A B C A B C A A B C split Sample Date 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 — — — — — — — — — — — — — Sample detail duckweed mat river surface river surface river surface river surface river surface river surface river surface duckweed mat duckweed mat duckweed mat Cones sorted from Ash seed pods from Oregon Ash seed pods from Oregon Ash seed pods from Oregon Ash seed pods from Oregon Ash leaves from Oregon Ash leaves from Oregon Ash leaves from Oregon Duckweed sorted from mat sorted from Twigs sorted from Twigs sorted from Twigs N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split N) and C/N ratios for samples collected from the Tualatin 15 δ C, Sample type 13 δ Coniferous litter Leaf litter Leaf litter Leaf litter Leaf litter Leaf litter Leaf litter Leaf litter Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, 80–202 μm Seston, 80–202 μm Seston, 80–202 μm Suspended sediment Suspended sediment Suspended sediment Suspended sediment Bed sediment Bed sediment Bed sediment Duckweed material Woody material Woody material Woody Site name Values of stable isotope compositions ( Values

Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin ID 10 12 12 12 12 13 13 13 14 14 14 15 15 15 16 16 16 16 17 17 17 18 19 19 19 Appendix A. samples.—Continued 38 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

E E E E E E E E E E E E E E E E C/N qualifier 8.92 9.10 8.89 9.04 7.68 7.17 7.27 9.78 7.97 7.56 7.37 8.18 9.29 9.40 8.90 8.21 C/N 11.38 11.63 11.01 11.01 11.76 12.11 15.33 13.98 12.99 15.18 14.26 13.73 13.98 12.84 13.37 N

L L L L L L L L L L L L 15 δ qualifier N 6.48 6.31 6.31 6.57 5.01 4.94 4.47 4.59 4.80 4.40 2.31 2.36 2.51 3.29 6.26 6.10 6.13 4.24 4.37 3.72 4.13 4.44 2.76 2.97 2.39 4.17 5.75 5.73 6.01 5.42 15 — δ C 13 δ -28.10 -28.06 -28.24 -28.17 -26.46 -26.84 -26.93 -26.32 -26.47 -26.38 -27.08 -27.28 -27.19 -27.04 -29.51 -29.56 -29.70 -27.04 -26.63 -27.08 -27.31 -27.87 -27.72 -26.86 -27.20 -27.12 -29.16 -29.08 -29.40 -27.99 -27.90 A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A U Acidified

0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 rep Lab A A B C A B C A B C A A B C A B C A B C A B C A B C A B C A B split Sample Date 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-16-99 07-16-99 07-16-99 07-16-99 07-16-99 07-16-99 07-16-99 07-16-99 07-16-99 07-16-99 07-16-99 07-16-99 07-16-99 07-16-99 07-16-99 07-16-99 07-16-99 07-16-99 07-16-99 07-16-99 07-16-99 07-16-99 07-16-99 07-16-99 — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — Sample detail N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split N) and C/N ratios for samples collected from the Tualatin 15 δ C, Sample type 13 δ Suspended sediment Suspended sediment Suspended sediment Suspended sediment Bed sediment Bed sediment Bed sediment Suspended sediment Suspended sediment Suspended sediment Bed sediment Bed sediment Bed sediment Bed sediment Suspended sediment Suspended sediment Suspended sediment Bed sediment Bed sediment Bed sediment Suspended sediment Suspended sediment Suspended sediment Bed sediment Bed sediment Bed sediment Suspended sediment Suspended sediment Suspended sediment Bed sediment Bed sediment Site name Values of stable isotope compositions ( Values

Tualatin River at RM 38.4 (Rood Bridge) Tualatin River at RM 38.4 (Rood Bridge) Tualatin River at RM 38.4 (Rood Bridge) Tualatin River at RM 38.4 (Rood Bridge) Tualatin River at RM 38.4 (Rood Bridge) Tualatin River at RM 38.4 (Rood Bridge) Tualatin River at RM 38.4 (Rood Bridge) Tualatin Gales Creek at old Hwy 47 Gales Creek at old Hwy 47 Gales Creek at old Hwy 47 Gales Creek at old Hwy 47 Gales Creek at old Hwy 47 Gales Creek at old Hwy 47 Gales Creek at old Hwy 47 Dairy Creek at Hwy 8 Dairy Creek at Hwy 8 Dairy Creek at Hwy 8 Dairy Creek at Hwy 8 Dairy Creek at Hwy 8 Dairy Creek at Hwy 8 River at RM 58.8 (Dilley) Tualatin River at RM 58.8 (Dilley) Tualatin River at RM 58.8 (Dilley) Tualatin River at RM 58.8 (Dilley) Tualatin River at RM 58.8 (Dilley) Tualatin River at RM 58.8 (Dilley) Tualatin Rock Creek at Hwy 8 Rock Creek at Hwy 8 Rock Creek at Hwy 8 Rock Creek at Hwy 8 Rock Creek at Hwy 8 ID 20 20 20 20 21 21 21 22 22 22 23 23 23 23 24 24 24 25 25 25 26 26 26 27 27 27 28 28 28 29 29 Appendix A. samples.—Continued Appendix A. 39

E E E E C/N qualifier 5.07 4.89 4.92 4.96 5.10 5.05 5.01 5.47 4.97 4.84 9.02 9.15 9.15 9.05 6.10 6.47 6.17 5.78 5.78 6.23 5.72 6.91 5.60 5.54 5.62 C/N 11.48 11.60 13.15 10.25 10.50 13.00 10.67 13.80 N

L L L L L L L 15 δ qualifier N 6.00 9.19 9.28 8.86 9.13 8.95 8.96 8.71 9.08 9.46 9.63 6.42 5.15 5.63 7.02 6.61 6.97 8.15 8.32 8.28 8.60 9.38 9.32 7.34 6.82 7.71 5.73 5.46 5.86 5.11 15 — — — δ C 13 — δ -28.04 -35.30 -35.45 -35.49 -37.36 -37.60 -37.43 -37.64 -37.61 -37.63 -37.69 -27.29 -26.81 -28.06 -27.49 -17.25 -17.49 -17.33 -34.95 -35.04 -35.17 -35.10 -34.78 -35.09 -34.95 -35.10 -34.97 -34.89 -28.15 -28.44 -28.34 -27.87 A A A A A A A A A A A A A A A A A A A A A A A A A A U U U U U U U Acidified

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 1 0 1 0 1 rep Lab C A B C A B C A A B C A A B C A A B A B C A B C A A B C C A A B B split Sample Date 07-16-99 07-16-99 07-16-99 07-16-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — Sample detail Spirogyra Spirogyra Spirogyra N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split N) and C/N ratios for samples collected from the Tualatin 15 δ C, Sample type 13 δ Bed sediment Suspended sediment Suspended sediment Suspended sediment Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, 80–202 μm Seston, 80–202 μm Seston, 80–202 μm Seston, 80–202 μm Bed sediment Bed sediment Bed sediment Bed sediment Periphyton Periphyton Periphyton Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, 80–202 μm Seston, 80–202 μm Seston, 80–202 μm Suspended sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Bed sediment Bed sediment Bed sediment Bed sediment Site name Values of stable isotope compositions ( Values

Rock Creek at Hwy 8 Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin ID 29 30 30 30 31 31 31 32 32 32 32 33 33 33 33 34 34 34 35 35 35 36 36 36 37 37 37 37 37 38 38 38 38 Appendix A. samples.—Continued 40 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

E E E E C/N qualifier 9.68 9.64 9.60 C/N 11.50 11.50 12.40 23.63 24.33 22.68 22.64 25.75 26.34 25.56 25.32 25.61 25.50 77.20 84.49 71.08 26.91 24.73 25.30 10.00 N

L L L L L L L 15 δ qualifier N 5.23 5.51 3.49 2.91 3.24 3.15 6.96 6.85 6.88 2.14 2.20 2.32 2.25 2.59 2.30 1.19 0.60 0.36 1.02 1.15 1.98 4.02 6.95 15 δ C 13 δ -28.22 -27.95 -28.69 -28.68 -28.18 -28.46 -29.89 -29.83 -29.83 -25.80 -27.60 -29.11 -28.31 -28.24 -27.86 -26.57 -26.57 -26.52 -26.03 -26.04 -26.24 -27.29 -27.03 A A A A A A A A A A A A A A A A U U U U U U U Acidified

0 1 0 0 0 0 0 0 0 0 1 0 1 0 0 0 0 0 0 0 0 0 0 rep Lab C C A A B C A B C A A A A B C A B C A B C A B split Sample Date 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 — — Sample detail duckweed mat duckweed mat duckweed mat duckweed mat duckweed mat duckweed mat duckweed mat duckweed mat duckweed mat slump slump slump edge edge Unsorted duckweed mat Unsorted duckweed mat Unsorted duckweed mat Unsorted duckweed mat Duckweed sorted from mat Duckweed sorted from mat Duckweed sorted from mat sorted from Twigs sorted from Twigs sorted from Twigs sorted from Twigs sorted from Twigs sorted from Twigs Cones sorted from Cones sorted from Cones sorted from A-horizon from bank with A-horizon from bank with A-horizon from bank with Bottom of slump at water Bottom of slump at water N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split N) and C/N ratios for samples collected from the Tualatin 15 δ C, Sample type 13 δ Bed sediment Bed sediment Duckweed Duckweed Duckweed Duckweed Duckweed Duckweed Duckweed material Woody material Woody material Woody material Woody material Woody material Woody Coniferous litter Coniferous litter Coniferous litter Soil Soil Soil Soil Soil Site name Values of stable isotope compositions ( Values

E E E E E E C/N qualifier 6.49 6.51 6.56 6.95 6.45 6.27 6.08 6.08 5.95 5.75 7.07 7.67 8.31 8.02 3.91 3.44 3.89 9.86 C/N 13.00 14.50 10.03 12.00 12.00 13.19 10.57 10.54 N

L L L L L L L L L 15 δ qualifier N 4.88 5.30 7.07 5.83 4.76 4.60 6.36 5.30 5.01 7.68 7.77 7.30 15 — — — — 11.30 11.72 11.80 10.23 10.64 10.87 10.43 10.92 12.66 12.57 δ C 13 — δ -27.03 -34.90 -34.98 -34.75 -34.94 -34.89 -34.67 -35.68 -35.87 -35.86 -35.88 -27.08 -27.68 -27.78 -28.81 -29.86 -29.52 -30.45 -29.33 -34.35 -34.62 -34.29 -29.63 -29.80 -29.96 A A A A A A A A A A A A A A A A A A A A A U U U U U Acidified

0 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 1 0 rep Lab C C A B C A B C A B C C A A B C A B B C A B C A A A split Sample Date 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-19-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 — — — — — — — — — — — — — — — — — Sample detail edge edge 24 hours 24 hours 24 hours 24 hours sample sample sample Bottom of slump at water Bottom of slump at water Fraction that settled after Fraction that settled after Fraction that settled after Fraction that settled after Aphanizomenon floating on Aphanizomenon floating on Aphanizomenon floating on N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split N) and C/N ratios for samples collected from the Tualatin 15 δ C, Sample type 13 δ Soil Soil Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, 80–202 μm Seston, 80–202 μm Seston, 80–202 μm Suspended sediment Suspended sediment Suspended sediment Suspended sediment Bed sediment Bed sediment Bed sediment Bed sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, >80 μm Site name Values of stable isotope compositions ( Values

Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 8.7 (Boones Ferry Bridge) Tualatin River at RM 8.7 (Boones Ferry Bridge) Tualatin River at RM 8.7 (Boones Ferry Bridge) Tualatin River at RM 8.7 (Boones Ferry Bridge) Tualatin River at RM 8.7 (Boones Ferry Bridge) Tualatin River at RM 8.7 (Boones Ferry Bridge) Tualatin River at RM 8.7 (Boones Ferry Bridge) Tualatin River at RM 8.7 (Boones Ferry Bridge) Tualatin River at RM 8.7 (Boones Ferry Bridge) Tualatin River at RM 8.7 (Boones Ferry Bridge) Tualatin River at RM 8.7 (Boones Ferry Bridge) Tualatin River at RM 8.7 (Boones Ferry Bridge) Tualatin River at RM 8.7 (Boones Ferry Bridge) Tualatin River at RM 8.7 (Boones Ferry Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin ID 44 44 45 45 45 46 46 46 47 47 47 47 48 48 48 48 49 49 49 49 50 50 50 51 51 51 Appendix A. samples.—Continued 42 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

E E E C/N qualifier 8.36 8.53 9.00 — — C/N 11.19 11.07 11.34 11.33 11.63 11.21 10.00 10.88 16.80 14.47 12.50 78.38 79.05 12.05 10.13 10.70 12.86 10.15 12.12 12.17 12.63 12.30 N

L L L L L L L L L L L L L L L L L L

15 δ qualifier N 5.43 6.34 6.17 4.95 5.53 5.11 4.70 4.23 4.86 4.45 5.57 5.79 4.26 3.67 7.52 7.01 5.95 5.26 6.79 5.05 5.17 5.50 5.46 15 — — — — δ C 13 δ -29.26 -28.88 -29.06 -28.96 -30.41 -30.20 -30.73 -27.28 -26.66 -27.59 -26.61 -27.34 -27.45 -26.64 -28.89 -29.55 -28.63 -28.95 -28.42 -29.50 -28.52 -28.24 -29.59 -28.16 -28.19 -28.35 -28.69 A A A A A A A A A A A A A A A A A A A A A U U U U U U Acidified

0 0 0 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 1 0 0 0 rep Lab B C C C A B C A B C A B B C A A B C A A B C C C A B C split Sample Date 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 — — — — — — — — — — — — — — — — — — — Sample detail sediment sediment sediment sediment 24 hours 24 hours 24 hours 24 hours Twigs removed from bed Twigs removed from bed Twigs removed from bed Twigs removed from bed Twigs Fraction that settled after Fraction that settled after Fraction that settled after Fraction that settled after N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split N) and C/N ratios for samples collected from the Tualatin 15 δ C, Sample type 13 δ Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, 80–202 μm Seston, 80–202 μm Seston, 80–202 μm Bed sediment Bed sediment Bed sediment material Woody material Woody material Woody material Woody Suspended sediment Suspended sediment Suspended sediment Suspended sediment Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, 80–202 μm Seston, 80–202 μm Seston, 80–202 μm Site name Values of stable isotope compositions ( Values

Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park ID 51 51 51 51 52 52 52 53 53 53 54 54 54 54 55 55 55 55 56 56 56 56 56 56 57 57 57 Appendix A. samples.—Continued Appendix A. 43

E E E E C/N qualifier — — C/N 11.01 12.50 15.95 10.52 17.03 13.80 13.98 30.01 28.44 28.81 48.56 42.84 40.81 21.02 18.71 17.37 16.10 18.10 39.13 N

L L L L 15 δ qualifier N 4.14 3.83 3.01 3.29 3.07 3.76 3.87 4.20 4.56 4.63 3.32 3.25 2.94 4.52 5.01 5.24 1.18 1.02 0.61 0.72 0.68 15 δ C 13 — δ -27.81 -28.05 -28.11 -28.05 -27.81 -28.03 -28.13 -29.50 -29.61 -29.68 -26.76 -26.86 -26.78 -27.82 -27.64 -28.10 -27.09 -27.86 -26.93 -26.36 A A A A A A A A A A A A A A A A A A A A U Acidified

0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 rep Lab A B C C A B C A B C A B C A B C A B B C A split Sample Date 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 — — — — Sample detail anoxic fractions anoxic fractions anoxic fractions in stream in stream in stream stream stream stream twigs in stream twigs in stream twigs in stream trail trail trail trail trail Top 10 cm, both oxic and Top 10 cm, both oxic and Top 10 cm, both oxic and Top Redtwig dogwood leaves Redtwig dogwood leaves Redtwig dogwood leaves Ash leaves in Oregon Ash leaves in Oregon Ash leaves in Oregon Decomposed leaves and Decomposed leaves and Decomposed leaves and Ash leaves from Oregon Ash leaves from Oregon Ash leaves from Oregon Ash leaves from Oregon Ash seed pods from Oregon N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split N) and C/N ratios for samples collected from the Tualatin 15 δ C, 13 Sample type δ detritus detritus detritus Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Leaf litter Leaf litter Leaf litter Leaf litter Leaf litter Leaf litter Decomposed terrestrial Decomposed terrestrial Decomposed terrestrial Leaf litter Leaf litter Leaf litter Leaf litter Leaf litter Site name Values of stable isotope compositions ( Values

Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park ID 58 58 58 58 59 59 59 60 60 60 61 61 61 62 62 62 63 63 63 63 64 Appendix A. samples.—Continued 44 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

C/N qualifier 6.87 6.86 6.83 6.92 9.60 9.54 9.20 9.14 9.46 C/N 44.85 39.87 40.49 36.18 14.49 15.60 14.65 10.05 53.91 57.66 58.39 33.25 30.72 N

15 δ qualifier N 1.48 0.57 0.65 0.63 4.59 4.54 4.55 8.47 5.58 5.34 5.58 5.01 4.21 5.21 6.55 5.63 6.17 2.53 1.84 1.68 15 -2.56 -2.59 δ C 13 — δ -26.38 -28.27 -26.43 -26.56 -39.70 -39.63 -39.75 -26.70 -34.12 -34.07 -34.23 -27.90 -27.84 -27.04 -27.38 -27.22 -25.34 -24.82 -25.02 -24.75 -25.07 A A A A A A A A A A A A A A A A A A A A A U Acidified

1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 rep Lab A A B C A B C A A B C A B C A B C A B C A B split Sample Date 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-19-99 07-19-99 07-19-99 07-21-99 07-21-99 07-21-99 08-04-99 08-04-99 08-04-99 08-04-99 08-04-99 08-04-99 08-04-99 08-04-99 Sample detail trail trail trail trail planted planted planted litter litter Oregon Ash seed pods from Oregon Ash seed pods from Oregon Ash seed pods from Oregon Ash seed pods from Oregon Cladophera Cladophera Cladophera Cladophera Cladophera Cladophera Cladophera agricultural field, tilled, not agricultural field, tilled, not agricultural field, tilled, not Chehalis soil Chehalis soil Chehalis soil Ash leaves Oregon Ash leaves Oregon Ash leaves Oregon Red Cedar Western Mixed Red Cedar Western Mixed N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split N) and C/N ratios for samples collected from the Tualatin 15 δ C, Sample type 13 δ Leaf litter Leaf litter Leaf litter Leaf litter Periphyton Periphyton Periphyton Periphyton Periphyton Periphyton Periphyton Soil Soil Soil Soil Soil Soil Leaf litter Leaf litter Leaf litter Coniferous litter Coniferous litter Site name Values of stable isotope compositions ( Values

holding pond) holding pond) holding pond) holding pond) holding pond) holding pond) Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park River at RM 9.4 (Basalt sill) Tualatin River at RM 9.4 (Basalt sill) Tualatin River at RM 9.4 (Basalt sill) Tualatin Onion Flat (Cipole Road and Hwy 99W) Onion Flat (Cipole Road and Hwy 99W) Onion Flat (Cipole Road and Hwy 99W) Jackson Bottom (between Miller Swale and Jackson Bottom (between Miller Swale and Jackson Bottom (between Miller Swale and Jackson Bottom (between Miller Swale and Jackson Bottom (between Miller Swale and Jackson Bottom (between Miller Swale and Nature Park Tualatin Nature Park Tualatin ID 64 64 64 64 65 65 65 66 67 67 67 68 68 68 69 69 69 70 70 70 71 71 Appendix A. samples.—Continued Appendix A. 45

E E E E E E C/N qualifier 4.82 5.17 4.89 6.67 4.50 5.55 4.67 4.39 4.60 4.75 4.78 4.79 8.55 8.48 9.04 3.84 3.70 C/N 31.23 27.48 26.98 27.57 N

L L L L 15 δ qualifier N 9.24 9.08 9.26 9.45 6.70 6.54 6.57 4.91 5.12 5.15 8.43 8.80 15 -2.44 -2.47 -2.68 -2.72 11.47 11.19 10.00 10.80 10.09 δ C 13 δ -24.91 -27.85 -27.97 -27.66 -24.24 -23.71 -26.58 -25.62 -24.63 -23.81 -26.07 -25.96 -25.99 -33.91 -33.82 -33.84 -28.32 -28.50 -28.40 -30.12 -30.14 A A A A A A A A A A A A A A A A A A U U U Acidified

0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 rep Lab C A B C A A A B C C A B C A B C A B C A B split Sample Date 08-04-99 08-04-99 08-04-99 08-04-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-14-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 07-21-99 09-10-99 09-10-99 — — — — — — — — — — — Sample detail litter suspended after 24 hours suspended after 24 hours suspended after 24 hours suspended after 24 hours suspended after 24 hours suspended after 24 hours Mixed Western Red Cedar Western Mixed Mixed Douglas Fir litter Mixed Douglas Fir litter Mixed Douglas Fir litter Fraction remaining Fraction remaining Fraction remaining Fraction remaining Fraction remaining Fraction remaining N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split N) and C/N ratios for samples collected from the Tualatin 15 δ C, Sample type 13 δ particulate particulate particulate particulate particulate particulate particulate particulate particulate Coniferous litter Coniferous litter Coniferous litter Coniferous litter WWTF effluent WWTF effluent WWTF effluent WWTF effluent WWTF effluent WWTF effluent WWTF effluent WWTF effluent WWTF effluent Suspended sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Seston, >80 μm Seston, >80 μm Site name Values of stable isotope compositions ( Values

Tualatin Nature Park Tualatin Nature Park Tualatin Nature Park Tualatin Nature Park Tualatin Facility Treatment Wastewater Rock Creek Facility Treatment Wastewater Rock Creek Facility Treatment Wastewater Rock Creek Facility Treatment Wastewater Rock Creek Facility Treatment Wastewater Rock Creek Facility Treatment Wastewater Rock Creek Facility Treatment Wastewater Durham Facility Treatment Wastewater Durham Facility Treatment Wastewater Durham River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Henry Hagg Lake Henry Hagg Lake ID 71 72 72 72 73 73 73 73 73 73 74 74 74 76 76 76 77 77 77 101 101 Appendix A. samples.—Continued 46 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

E E E E E E C/N qualifier — 3.96 5.36 5.26 5.23 6.90 7.17 7.12 7.83 7.48 7.47 7.26 7.62 7.44 7.54 8.49 8.50 8.79 C/N 11.90 11.89 12.00 14.14 14.27 13.18 15.06 12.91 15.40 13.40 12.27 15.60 14.47 14.30 10.42 N

L L L L 15 δ qualifier N 8.17 6.36 6.67 6.72 4.26 3.95 4.15 4.00 3.85 3.95 4.22 3.87 3.91 3.85 3.94 8.24 7.90 8.00 7.43 7.84 7.49 7.51 7.17 7.38 7.35 6.32 5.78 4.07 4.46 4.33 4.52 3.98 4.09 15 δ C 13 δ -30.28 -31.14 -31.20 -31.31 -30.93 -31.23 -31.07 -26.79 -28.21 -28.07 -27.21 -28.27 -28.11 -28.17 -28.24 -33.49 -32.83 -33.26 -32.80 -33.19 -33.00 -34.15 -33.95 -33.99 -34.14 -30.03 -30.98 -31.08 -30.22 -35.45 -35.47 -35.58 -29.87 A A A A A A A A A A A A A A A A A A A A A A A A A A A A U U U U U Acidified

0 0 0 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 rep Lab C A B C A B C A A A B B C C C A B C A B C A B B C A A B C A B C A split Sample Date 09-11-99 09-11-99 09-11-99 09-11-99 09-11-99 09-11-99 09-11-99 09-11-99 09-11-99 09-11-99 09-11-99 09-11-99 09-11-99 09-11-99 09-11-99 09-11-99 09-11-99 09-10-99 09-10-99 09-10-99 09-10-99 09-10-99 09-10-99 09-10-99 09-10-99 09-10-99 09-10-99 09-10-99 09-10-99 09-10-99 09-10-99 09-10-99 09-13-99 — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — Sample detail Cladophera Cladophera Cladophera N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split N) and C/N ratios for samples collected from the Tualatin 15 δ C, Sample type 13 δ Seston, >80 μm Seston, 80–202 μm Seston, 80–202 μm Seston, 80–202 μm Suspended sediment Suspended sediment Suspended sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, 80–202 μm Seston, 80–202 μm Seston, 80–202 μm Suspended sediment Suspended sediment Suspended sediment Suspended sediment Bed sediment Bed sediment Bed sediment Bed sediment Periphyton Periphyton Periphyton Seston, >80 μm Site name Values of stable isotope compositions ( Values

Henry Hagg Lake Henry Hagg Lake Henry Hagg Lake Henry Hagg Lake River at RM 38.4 (Rood Bridge) Tualatin River at RM 38.4 (Rood Bridge) Tualatin River at RM 38.4 (Rood Bridge) Tualatin River at RM 38.4 (Rood Bridge) Tualatin River at RM 38.4 (Rood Bridge) Tualatin River at RM 38.4 (Rood Bridge) Tualatin River at RM 38.4 (Rood Bridge) Tualatin River at RM 38.4 (Rood Bridge) Tualatin River at RM 38.4 (Rood Bridge) Tualatin River at RM 38.4 (Rood Bridge) Tualatin River at RM 38.4 (Rood Bridge) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.4 (Basalt sill) Tualatin River at RM 9.4 (Basalt sill) Tualatin River at RM 9.4 (Basalt sill) Tualatin River at RM 20.3 Tualatin ID 110 101 102 102 102 103 103 103 104 104 104 104 104 104 104 104 105 105 105 106 106 106 107 107 107 107 108 108 108 108 109 109 109 Appendix A. samples.—Continued Appendix A. 47

E E E E C/N qualifier 9.91 9.32 9.82 8.42 8.56 8.86 8.51 9.30 9.27 9.80 C/N 11.07 11.91 11.26 11.94 11.99 10.05 13.78 12.45 15.26 12.60 13.36 13.78 12.99 13.19 12.40 12.00 12.99 10.52 10.15 14.14 14.28 13.88 12.08 N

L L L L L L L L L L L 15 δ qualifier N 4.28 4.11 4.20 5.41 5.85 6.37 7.12 6.38 6.70 5.10 5.56 5.41 5.87 5.36 4.99 6.11 5.01 7.67 6.49 5.91 6.08 5.88 6.94 6.66 6.55 6.59 6.16 5.98 6.02 6.61 6.34 15 — — δ C 13 δ -29.49 -29.18 -29.56 -31.04 -30.61 -30.94 -30.12 -31.58 -30.71 -28.80 -29.54 -29.53 -29.33 -29.28 -28.52 -28.69 -28.99 -28.69 -31.69 -32.74 -32.38 -31.30 -31.15 -30.76 -31.69 -31.48 -31.61 -30.85 -28.74 -28.67 -28.75 -29.02 -28.84 A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A U U Acidified

0 0 1 0 0 0 0 0 0 0 0 1 0 0 0 1 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 rep Lab B C C A B C A B C A A A B C A A B C A B C A B C A B B C A B C A B split Sample Date 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-13-99 09-15-99 09-15-99 — — — — — — — — — — — — — — — — — — — — — — — — — — — — — Sample detail Anoxic blue-gray fraction Anoxic blue-gray fraction Anoxic blue-gray fraction Anoxic blue-gray fraction N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split N) and C/N ratios for samples collected from the Tualatin 15 δ C, Sample type 13 δ Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, 80–202 μm Seston, 80–202 μm Seston, 80–202 μm Suspended sediment Suspended sediment Suspended sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Suspended sediment Suspended sediment Suspended sediment Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, 80–202 μm Seston, 80–202 μm Seston, 80–202 μm Seston, 80–202 μm Bed sediment Bed sediment Bed sediment Seston, >80 μm Seston, >80 μm Site name Values of stable isotope compositions ( Values

Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin ID 111 111 111 110 110 110 112 112 112 113 113 113 113 113 114 114 114 114 115 115 115 116 116 116 117 117 117 117 118 118 118 119 119 Appendix A. samples.—Continued 48 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

E E E E E E E E E E

C/N qualifier 8.00 8.12 8.40 4.95 4.89 4.83 4.85 4.68 4.49 4.47 9.86 9.70 C/N 11.67 11.51 11.27 11.61 12.01 12.24 12.39 12.79 12.19 12.88 12.48 12.59 17.08 15.00 14.63 16.23 12.67 14.00 15.09 10.78 13.98 N

L L 15 δ qualifier N 6.19 5.66 5.92 5.63 5.79 6.47 7.59 7.29 5.66 5.51 5.79 5.88 5.45 6.55 6.28 6.05 4.56 4.38 5.73 4.72 15 — — — — 13.12 12.36 12.90 16.74 16.60 16.78 16.71 17.17 17.54 δ C 13 δ -28.92 -28.93 -29.12 -28.91 -29.03 -29.69 -27.86 -27.76 -28.56 -29.32 -29.78 -29.61 -29.43 -29.63 -29.43 -29.65 -33.86 -33.63 -33.54 -37.69 -37.72 -37.59 -37.64 -37.91 -38.37 -38.40 -29.37 -29.42 -29.46 -30.48 -31.24 -30.40 -32.32 A A A A A A A A A A A A A A A A A A A A A A A A A A A A U U U U U Acidified

0 0 0 0 1 0 0 0 0 0 0 1 0 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 rep Lab C A B C C A B B C A A A B B B C A B C A A B C A B C A B C A B C A split Sample Date 09-15-99 09-15-99 09-15-99 09-15-99 09-15-99 09-15-99 09-15-99 09-15-99 09-15-99 09-15-99 09-15-99 09-15-99 09-15-99 09-15-99 09-15-99 09-15-99 09-15-99 09-15-99 09-15-99 09-15-99 09-15-99 09-15-99 09-15-99 09-15-99 09-15-99 09-15-99 09-15-99 09-15-99 09-15-99 02-08-00 02-08-00 02-08-00 02-04-00 — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — Sample detail N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split N) and C/N ratios for samples collected from the Tualatin 15 δ C, Sample type 13 δ Seston, >80 μm Seston, 80–202 μm Seston, 80–202 μm Seston, 80–202 μm Seston, 80–202 μm Suspended sediment Suspended sediment Suspended sediment Suspended sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Suspended sediment Suspended sediment Suspended sediment Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, 80–202 μm Seston, 80–202 μm Seston, 80–202 μm Bed sediment Bed sediment Bed sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Site name Values of stable isotope compositions ( Values

Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin River at RM 38.4 (Rood Bridge) Tualatin River at RM 38.4 (Rood Bridge) Tualatin River at RM 38.4 (Rood Bridge) Tualatin Road) River at RM 5.5 (Stafford Tualatin ID 119 120 120 120 120 121 121 121 121 122 122 122 122 122 122 122 123 123 123 124 124 124 124 125 125 125 126 126 126 201 201 201 202 Appendix A. samples.—Continued Appendix A. 49

E E E E E E E E E E E E E E E E E E E E E E E E E E E C/N qualifier C/N 11.80 11.86 12.00 14.96 14.47 13.98 15.21 15.70 17.27 13.98 14.25 25.24 27.62 29.25 28.01 29.24 27.43 13.98 13.73 23.19 24.67 23.02 22.07 30.76 28.29 25.82 12.13 13.80 13.78 13.55 13.11 13.00 14.46 N

L L L L L L L L L L L L L L L L L L L L L L L L 15 δ qualifier N 4.11 2.67 3.72 5.04 4.28 4.58 4.02 4.65 5.34 4.73 4.91 5.59 3.79 4.20 2.81 4.56 4.12 3.76 4.11 4.30 3.75 3.45 4.04 3.45 3.94 4.05 3.16 3.21 3.93 15 — — — — δ C 13 δ -31.57 -31.97 -31.68 -32.49 -30.74 -30.64 -31.19 -31.29 -31.21 -27.87 -27.50 -27.44 -27.80 -27.53 -27.71 -30.78 -30.89 -31.22 -28.54 -28.25 -28.64 -28.78 -27.73 -29.76 -29.15 -31.28 -31.40 -32.55 -31.44 -31.16 -30.94 -28.89 -29.47 A A A A A A A A A A A A A A A A A A A A A A A A A A U U U U U U U Acidified

0 1 0 0 0 0 0 1 0 0 1 0 1 0 1 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 1 rep Lab B B B C A B C C C A A B B C C A B C A B B C A B C A A A B C A A A split Sample Date 02-04-00 02-04-00 02-04-00 02-04-00 02-04-00 02-04-00 02-04-00 02-04-00 02-04-00 02-04-00 02-04-00 02-04-00 02-04-00 02-04-00 02-04-00 02-04-00 02-04-00 02-04-00 02-04-00 02-04-00 02-04-00 02-04-00 02-07-00 02-07-00 02-07-00 02-07-00 02-07-00 02-07-00 02-07-00 02-07-00 02-07-00 02-07-00 02-07-00 — — — — — — — — — — — — — — — — — — — — — — — — — — — Sample detail Woody debris removed Woody debris removed Woody debris removed Woody debris removed Woody debris removed Woody debris removed Woody N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split N) and C/N ratios for samples collected from the Tualatin 15 δ C, Sample type 13 δ Suspended sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Suspended sediment Suspended sediment Suspended sediment Bed sediment Bed sediment Bed sediment Bed sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Site name Values of stable isotope compositions ( Values

Tualatin River at RM 5.5 (Stafford Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin Gales Creek at old Hwy 47 Gales Creek at old Hwy 47 Gales Creek at old Hwy 47 Dairy Creek at Hwy 8 Dairy Creek at Hwy 8 Dairy Creek at Hwy 8 Dairy Creek at Hwy 8 Dairy Creek at Hwy 8 River at RM 58.8 (Dilley) Tualatin River at RM 58.8 (Dilley) Tualatin River at RM 58.8 (Dilley) Tualatin ID 202 202 202 202 203 203 203 203 203 204 204 204 204 204 204 206 206 206 207 207 207 207 208 208 208 209 209 209 209 209 210 210 210 Appendix A. samples.—Continued 50 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

E E E E E E E E E E E E E C/N qualifier 9.97 9.45 9.98 8.61 8.21 9.06 8.64 9.46 9.91 7.71 7.57 7.52 7.49 7.67 C/N 15.95 15.16 13.24 16.50 14.50 15.95 13.32 14.57 13.19 15.46 12.66 13.67 13.33 10.00 10.27 10.00 13.10 13.36 14.20 N

L L L L L L L L L L L L L

15 δ qualifier N 2.68 4.41 4.25 5.01 4.63 4.42 4.28 4.48 4.28 4.05 3.58 4.45 5.19 3.41 3.41 3.13 3.55 2.96 2.98 2.98 3.18 5.56 5.26 5.40 5.34 4.27 4.16 3.76 9.31 8.79 8.96 8.63 9.18 15 δ C 13 δ -29.41 -29.42 -29.14 -32.37 -33.34 -32.27 -32.06 -31.12 -30.95 -31.18 -32.39 -31.63 -32.66 -26.41 -26.26 -26.52 -26.28 -26.07 -26.28 -25.85 -27.17 -31.15 -31.27 -31.06 -31.07 -28.18 -28.05 -28.12 -32.67 -32.53 -32.45 -32.68 -32.43 A A A A A A A A A U U U U U U U U U U U U U U U U U U U U U U U U Acidified

0 0 1 0 1 0 0 0 0 1 0 0 1 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 rep Lab B C C A A B C A B B C C C A B C A B C A B B C A B C A B C A B D D split Sample Date 02-07-00 02-07-00 02-07-00 02-07-00 02-07-00 02-07-00 02-07-00 02-07-00 02-07-00 02-07-00 02-07-00 02-07-00 02-07-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-05-00 06-05-00 06-05-00 06-05-00 06-05-00 06-05-00 06-05-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — Sample detail N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split N) and C/N ratios for samples collected from the Tualatin 15 δ C, Sample type 13 δ Suspended sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, 80–202 μm Seston, 80–202 μm Seston, 80–202 μm Seston, 80–202 μm Suspended sediment Suspended sediment Suspended sediment Suspended sediment Bed sediment Bed sediment Bed sediment Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, 80–202 μm Seston, 80–202 μm Site name Values of stable isotope compositions ( Values

Tualatin River at RM 58.8 (Dilley) Tualatin River at RM 58.8 (Dilley) Tualatin River at RM 58.8 (Dilley) Tualatin Rock Creek at Hwy 8 Rock Creek at Hwy 8 Rock Creek at Hwy 8 Rock Creek at Hwy 8 Fanno Creek at Durham Road Fanno Creek at Durham Road Fanno Creek at Durham Road Fanno Creek at Durham Road Fanno Creek at Durham Road Fanno Creek at Durham Road Henry Hagg Lake Henry Hagg Lake Henry Hagg Lake Henry Hagg Lake Henry Hagg Lake Henry Hagg Lake Henry Hagg Lake Henry Hagg Lake River at RM 38.4 (Rood Bridge) Tualatin River at RM 38.4 (Rood Bridge) Tualatin River at RM 38.4 (Rood Bridge) Tualatin River at RM 38.4 (Rood Bridge) Tualatin River at RM 38.4 (Rood Bridge) Tualatin River at RM 38.4 (Rood Bridge) Tualatin River at RM 38.4 (Rood Bridge) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin ID 211 211 211 211 210 210 210 212 212 212 212 212 212 301 301 301 301 302 302 302 302 303 303 303 303 304 304 304 305 305 305 306 306 Appendix A. samples.—Continued Appendix A. 51

E E E E E E C/N qualifier 7.82 7.70 6.52 6.80 6.80 8.10 8.28 8.19 8.56 8.10 8.19 8.28 8.57 8.81 8.76 6.55 6.62 6.63 C/N 11.02 11.21 13.17 13.86 13.57 10.43 10.98 13.29 13.71 12.83 13.82 12.65 12.79 13.04 13.28 N

L L L L L L L L L 15 δ qualifier N 8.43 8.46 9.45 9.53 9.51 4.97 5.21 5.64 7.62 7.57 6.06 6.60 6.69 7.00 6.95 9.92 9.50 8.80 9.16 5.83 6.13 5.80 7.82 7.68 8.62 8.08 7.96 15 — 11.95 11.62 10.00 10.06 10.81 δ C 13 δ -32.59 -32.52 -35.06 -34.99 -35.17 -28.45 -28.88 -28.68 -29.19 -29.36 -28.11 -28.27 -36.24 -36.19 -36.19 -36.23 -32.71 -32.51 -32.62 -32.60 -32.66 -32.65 -35.82 -34.98 -34.85 -28.86 -28.71 -28.86 -29.43 -29.73 -29.66 -29.79 -29.77 U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U Acidified

0 1 0 0 0 0 0 0 0 0 0 1 0 1 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 rep Lab C C A B C A B C A B C C A A B C A B C A B C A B B A B C A B C A B split Sample Date 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-03-00 06-05-00 06-05-00 06-05-00 06-05-00 06-05-00 — — — — — — — — — — — — — — — — — — — — — — — — — Sample detail Decomposed duckweed Decomposed duckweed Decomposed duckweed Decomposed duckweed Cladophera Cladophera Cladophera Cladophera N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split N) and C/N ratios for samples collected from the Tualatin 15 δ C, Sample type 13 δ Seston, 80–202 μm Seston, 80–202 μm Suspended sediment Suspended sediment Suspended sediment Bed sediment Bed sediment Bed sediment Duckweed Duckweed Duckweed Duckweed Periphyton Periphyton Periphyton Periphyton Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, 80–202 μm Seston, 80–202 μm Seston, 80–202 μm Suspended sediment Suspended sediment Suspended sediment Bed sediment Bed sediment Bed sediment Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, 80–202 μm Seston, 80–202 μm Site name Values of stable isotope compositions ( Values

Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.9 (Cook Park) Tualatin River at RM 9.4 (Basalt sill) Tualatin River at RM 9.4 (Basalt sill) Tualatin River at RM 9.4 (Basalt sill) Tualatin River at RM 9.4 (Basalt sill) Tualatin River at RM 8.7 (Boones Ferry Bridge) Tualatin River at RM 8.7 (Boones Ferry Bridge) Tualatin River at RM 8.7 (Boones Ferry Bridge) Tualatin River at RM 8.7 (Boones Ferry Bridge) Tualatin River at RM 8.7 (Boones Ferry Bridge) Tualatin River at RM 8.7 (Boones Ferry Bridge) Tualatin River at RM 8.7 (Boones Ferry Bridge) Tualatin River at RM 8.7 (Boones Ferry Bridge) Tualatin River at RM 8.7 (Boones Ferry Bridge) Tualatin River at RM 8.7 (Boones Ferry Bridge) Tualatin River at RM 8.7 (Boones Ferry Bridge) Tualatin River at RM 8.7 (Boones Ferry Bridge) Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin ID 311 311 311 306 306 307 307 307 308 308 308 309 309 309 309 310 310 310 310 312 312 312 313 313 313 314 314 314 315 315 315 316 316 Appendix A. samples.—Continued 52 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

C/N qualifier 8.67 8.83 8.72 9.38 9.50 9.39 5.90 6.29 5.65 7.89 7.50 9.32 C/N 11.38 11.40 11.46 13.54 13.03 12.71 12.92 13.17 10.95 10.92 10.56 12.69 12.64 13.69 15.19 15.17 15.52 15.10 15.13 15.30 15.36 N

L L L L L L L 15 δ qualifier N 6.98 7.51 8.80 8.81 8.69 5.38 5.38 5.65 9.82 5.14 5.27 5.24 5.94 6.81 6.22 5.95 5.79 6.21 4.66 7.10 7.01 7.04 5.18 5.54 5.09 15 11.24 10.84 10.09 10.30 10.35 10.03 10.84 10.24 δ C 13 δ -29.76 -29.77 -32.55 -32.73 -32.38 -28.41 -28.20 -28.25 -30.51 -30.22 -29.99 -29.41 -29.04 -29.18 -31.65 -31.51 -31.70 -28.08 -28.05 -27.65 -28.82 -29.04 -28.94 -28.90 -29.07 -29.15 -29.11 -31.30 -30.72 -31.38 -27.54 -28.25 -27.40 U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U Acidified

0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 rep Lab C C A B C A B C B B C A B C A B C A B C A B B C A B C A B C A B C split Sample Date 06-05-00 06-05-00 06-05-00 06-05-00 06-05-00 06-05-00 06-05-00 06-05-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — Sample detail N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split N) and C/N ratios for samples collected from the Tualatin 15 δ C, Sample type 13 δ Seston, 80–202 μm Seston, 80–202 μm Suspended sediment Suspended sediment Suspended sediment Bed sediment Bed sediment Bed sediment Suspended sediment Suspended sediment Suspended sediment Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, 80–202 μm Seston, 80–202 μm Seston, 80–202 μm Bed sediment Bed sediment Bed sediment Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, 80–202 μm Seston, 80–202 μm Seston, 80–202 μm Suspended sediment Suspended sediment Suspended sediment Bed sediment Bed sediment Bed sediment Site name Values of stable isotope compositions ( Values

Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 16.2 (Elsner Bridge) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin ID 316 316 317 317 317 318 318 318 319 319 319 320 320 320 321 321 321 322 322 322 323 323 323 323 324 324 324 325 325 325 326 326 326 Appendix A. samples.—Continued Appendix A. 53

C/N qualifier — 7.78 8.93 9.08 9.33 6.45 6.44 6.43 6.16 6.05 6.15 8.18 7.65 7.89 7.72 8.84 8.33 9.11 8.72 9.28 9.11 8.89 8.50 8.64 5.86 C/N 12.50 10.88 10.00 13.12 10.57 15.62 13.95 15.41 N

15 δ qualifier N 5.23 5.52 5.86 5.79 5.89 2.97 3.28 2.81 1.76 1.86 1.55 4.83 4.66 4.51 4.54 2.36 2.48 2.59 3.72 3.70 3.71 3.80 3.88 3.60 15 11.92 12.22 12.16 13.46 13.70 13.59 13.69 13.80 13.73 δ C 13 δ -28.02 -33.59 -33.70 -33.24 -37.66 -37.88 -37.88 -37.87 -38.01 -38.09 -28.02 -28.20 -28.10 -28.28 -29.66 -29.77 -29.73 -27.74 -27.49 -27.60 -30.26 -30.95 -31.01 -30.24 -27.86 -27.78 -27.68 -31.41 -31.34 -31.26 -27.78 -27.87 -27.76 U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U Acidified

1 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 rep Lab C A B C A B C A B C A A B C A B C A B C A B B C A B C A B C A B C split Sample Date 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 06-02-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — Sample detail N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split N) and C/N ratios for samples collected from the Tualatin 15 δ C, Sample type 13 δ Bed sediment Suspended sediment Suspended sediment Suspended sediment Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, 80–202 μm Seston, 80–202 μm Seston, 80–202 μm Bed sediment Bed sediment Bed sediment Bed sediment Suspended sediment Suspended sediment Suspended sediment Bed sediment Bed sediment Bed sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Bed sediment Bed sediment Bed sediment Suspended sediment Suspended sediment Suspended sediment Bed sediment Bed sediment Bed sediment Site name Values of stable isotope compositions ( Values

Tualatin River at RM 26.9 (Scholls) Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Gales Creek at old Hwy 47 Gales Creek at old Hwy 47 Gales Creek at old Hwy 47 Gales Creek at old Hwy 47 Gales Creek at old Hwy 47 Gales Creek at old Hwy 47 River at RM 58.8 (Dilley) Tualatin River at RM 58.8 (Dilley) Tualatin River at RM 58.8 (Dilley) Tualatin River at RM 58.8 (Dilley) Tualatin River at RM 58.8 (Dilley) Tualatin River at RM 58.8 (Dilley) Tualatin River at RM 58.8 (Dilley) Tualatin Dairy Creek at Hwy 8 Dairy Creek at Hwy 8 Dairy Creek at Hwy 8 Dairy Creek at Hwy 8 Dairy Creek at Hwy 8 Dairy Creek at Hwy 8 ID 326 327 327 327 328 328 328 329 329 329 330 330 330 330 331 331 331 332 332 332 333 333 333 333 334 334 334 335 335 335 336 336 336 Appendix A. samples.—Continued 54 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon

E E E C/N qualifier 7.29 6.33 6.20 6.92 6.94 6.86 6.98 7.53 7.31 7.93 8.40 5.94 6.33 6.86 C/N 11.27 17.05 14.73 14.99 13.79 15.43 15.00 14.09 19.24 19.11 21.13 10.62 12.31 10.38 N

L L 15 δ qualifier N 3.47 4.57 4.62 4.73 5.58 5.69 5.55 5.58 5.55 5.56 3.57 3.53 3.52 3.52 5.04 4.98 4.97 4.14 4.59 4.56 4.30 4.13 3.97 4.11 7.43 15 10.14 10.25 10.02 δ C 13 δ -27.68 -31.09 -31.16 -31.02 -32.07 -32.05 -31.92 -28.63 -28.95 -28.78 -42.79 -42.85 -43.05 -42.68 -28.48 -28.59 -29.70 -31.72 -31.82 -31.92 -29.11 -28.45 -28.42 -28.35 -27.57 -26.93 -27.72 -28.56 U U U U U U U U U U U U U U U U U U U U U U U U U U U U Acidified

1 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 rep Lab C A B C A B C A B C A A B C A B C A B C A B B C A B C A split Sample Date 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 05-31-00 06-01-00 06-01-00 06-01-00 06-01-00 — — — — — — — — — — — — — — — — — — Sample detail plant material in stream plant material in stream plant material in stream Grass growing in stream Grass growing in stream Grass growing in stream Species not identified Species not identified Species not identified Species not identified Decomposed non-woody Decomposed non-woody Decomposed non-woody N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split N) and C/N ratios for samples collected from the Tualatin 15 δ C, Sample type 13 δ detritus detritus detritus particulate particulate particulate particulate Bed sediment Grass Grass Grass Suspended sediment Suspended sediment Suspended sediment Bed sediment Bed sediment Bed sediment Periphyton Periphyton Periphyton Periphyton Decomposed terrestrial Decomposed terrestrial Decomposed terrestrial Suspended sediment Suspended sediment Suspended sediment Bed sediment Bed sediment Bed sediment Bed sediment WWTF effluent WWTF effluent WWTF effluent WWTF effluent Site name Values of stable isotope compositions ( Values

Dairy Creek at Hwy 8 Dairy Creek at Hwy 8 Dairy Creek at Hwy 8 Dairy Creek at Hwy 8 Rock Creek at Hwy 8 Rock Creek at Hwy 8 Rock Creek at Hwy 8 Rock Creek at Hwy 8 Rock Creek at Hwy 8 Rock Creek at Hwy 8 Rock Creek at Hwy 8 Rock Creek at Hwy 8 Rock Creek at Hwy 8 Rock Creek at Hwy 8 Rock Creek at Hwy 8 Rock Creek at Hwy 8 Rock Creek at Hwy 8 Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Fanno Creek at Durham City Park Facility Treatment Wastewater Rock Creek Facility Treatment Wastewater Rock Creek Facility Treatment Wastewater Rock Creek Facility Treatment Wastewater Durham ID 336 337 337 337 338 338 338 339 339 339 340 340 340 340 341 341 341 342 342 342 343 343 343 343 344 344 344 345 Appendix A. samples.—Continued Appendix A. 55 E E E C/N qualifier 6.11 6.17 4.38 4.38 4.96 5.05 4.67 4.31 4.49 4.15 4.39 3.97 9.73 9.12 8.34 9.12 8.83 9.82 7.01 6.16 6.60 9.22 9.80 9.29 C/N 10.05 10.25 10.12 10.25 10.45 10.79 18.56 16.25 N 15 δ qualifier N 7.23 6.79 9.59 9.57 8.96 8.88 9.47 9.58 5.78 5.98 5.63 6.75 7.03 6.67 7.17 6.89 6.89 6.74 6.76 7.42 7.31 7.41 5.26 4.66 5.11 4.66 4.59 5.17 15 12.49 12.86 13.17 13.09 δ C 13 δ -27.99 -27.28 -35.10 -35.03 -35.10 -35.15 -34.89 -34.92 -32.72 -33.36 -32.69 -33.81 -18.50 -18.47 -18.28 -26.23 -26.36 -26.20 -26.58 -29.41 -29.51 -29.33 -29.51 -32.97 -33.26 -33.02 -27.98 -27.99 -28.09 -27.73 -27.40 -27.41 A A A A A A A A A A A A A A A A A A A A A A A A A A U U U U U U Acidified

0 0 0 1 0 1 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 1 0 0 0 0 0 1 0 0 0 1 rep Lab B C A A A A B C A B B C A B C A A B C A B B C A B C A A B C A A split Sample Date 08-11-98 08-11-98 08-11-98 08-11-98 06-01-00 06-01-00 08-13-98 08-13-98 08-13-98 08-13-98 08-13-98 08-13-98 08-13-98 08-13-98 08-13-98 08-13-98 08-18-98 08-18-98 08-18-98 09-29-98 09-29-98 09-29-98 09-29-98 09-17-98 09-17-98 09-17-98 09-17-98 09-17-98 09-17-98 09-17-98 08-20-98 08-20-98 — — — — — — — — — — — — — — — — — — — Sample detail Species not identified Species not identified Species not identified Species not identified Species not identified Species not identified Species not identified Duckweed sorted from mat Duckweed sorted from mat Duckweed sorted from mat Duckweed sorted from mat Core 1, top 3 cm Core 1, top 3 cm N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split N) and C/N ratios for samples collected from the Tualatin 15 δ C, Sample type 13 δ particulate particulate WWTF effluent WWTF effluent Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, >80 μm Periphyton Periphyton Periphyton Periphyton Periphyton Periphyton Periphyton Seston, >80 μm Seston, >80 μm Seston, >80 μm Seston, >80 μm Duckweed Duckweed Duckweed Duckweed Suspended sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Suspended sediment Bed sediment Bed sediment Site name Values of stable isotope compositions ( Values

Durham Wastewater Treatment Facility Treatment Wastewater Durham Facility Treatment Wastewater Durham Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin River at RM 20.3 Tualatin Henry Hagg Lake Henry Hagg Lake Henry Hagg Lake Henry Hagg Lake River at RM 24.5 Tualatin River at RM 24.5 Tualatin River at RM 24.5 Tualatin River at RM 24.5 Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin ID 345 345 401 401 401 401 401 401 402 402 402 402 403 403 403 404 404 404 404 405 405 405 405 406 406 406 407 407 407 407 408.1 408.1 Appendix A. samples.—Continued 56 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon E E E E E E E E E E E E E E C/N qualifier — — — — C/N 11.83 11.67 11.25 11.36 11.94 13.40 17.60 10.52 10.36 12.40 15.86 12.83 12.99 15.09 13.34 12.99 12.99 13.07 12.46 12.54 15.46 16.28 17.59 14.22 14.33 14.33 19.24 16.54 N L L L L L L L L L 15 δ qualifier — — — — N 4.64 4.99 5.05 5.06 6.24 5.32 5.03 4.19 3.95 4.06 3.93 3.27 3.25 4.66 4.18 3.79 3.66 6.03 5.80 5.24 3.10 3.29 2.96 5.01 5.39 4.98 3.16 3.30 15 δ C 13 δ -27.74 -27.80 -27.97 -28.02 -27.99 -28.09 -27.29 -28.16 -27.82 -28.19 -28.34 -27.94 -28.18 -28.41 -28.32 -27.93 -27.47 -27.74 -27.93 -27.83 -27.86 -27.79 -27.15 -27.28 -27.22 -27.24 -27.41 -27.57 -27.53 -27.44 -27.58 -27.75 A A A A A A A A A A A A A A A A A A A A A A A A U U U U U U U U Acidified

0 1 0 1 0 1 2 3 0 0 0 0 1 0 0 0 0 0 1 2 3 0 0 0 0 0 1 2 3 0 0 0 rep Lab A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A split Sample Date 08-20-98 08-20-98 08-20-98 08-20-98 08-20-98 08-20-98 08-20-98 08-20-98 08-20-98 08-20-98 08-20-98 08-20-98 08-20-98 08-20-98 08-20-98 08-18-98 08-18-98 08-18-98 08-18-98 08-18-98 08-18-98 08-18-98 08-18-98 08-18-98 08-18-98 08-18-98 08-18-98 08-18-98 08-18-98 08-18-98 08-18-98 08-18-98 Sample detail Core 2, top 2 cm Core 2, top 2 cm Core 3, top 1 cm Core 3, top 1 cm Core 3, top 1 cm Core 3, top 1 cm Core 3, top 1 cm Core 3, top 1 cm Core 4, top 3 cm Core 5, top 2 cm Core 6, top 1 cm Core 7, top 3 cm Core 7, top 3 cm Core 8, top 2 cm Core 9, top 1 cm Core 1, top 3 cm Core 2, top 2 cm Core 3, top 1 cm Core 3, top 1 cm Core 3, top 1 cm Core 3, top 1 cm Core 3, top 1 cm Core 4, top 3 cm Core 5, top 2 cm Core 6, top 1 cm Core 7, top 3 cm Core 7, top 3 cm Core 7, top 3 cm Core 7, top 3 cm Core 7, top 3 cm Core 8, top 2 cm Core 9, top 1 cm N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split N) and C/N ratios for samples collected from the Tualatin 15 δ C, Sample type 13 δ Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Bed sediment Site name Values of stable isotope compositions ( Values

Tualatin River at RM 5.5 (Stafford Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin River at RM 26.9 (Scholls) Tualatin ID 408.2 408.2 408.3 408.3 408.3 408.3 408.3 408.3 408.4 408.5 408.6 408.7 408.7 408.8 408.9 409.1 409.2 409.3 409.3 409.3 409.3 409.3 409.4 409.5 409.6 409.7 409.7 409.7 409.7 409.7 409.8 409.9 Appendix A. samples.—Continued Appendix A. 57 C/N qualifier — 9.88 9.85 C/N 11.19 11.56 11.89 10.61 10.77 10.60 10.48 12.23 10.24 20.89 20.82 21.54 25.82 23.47 25.48 43.88 40.11 35.65 27.21 28.40 27.13 30.15 55.74 N 15 δ qualifier N 5.67 5.40 5.56 5.13 3.79 4.63 4.50 5.01 6.09 6.47 5.10 2.34 2.33 2.10 1.97 0.38 15 -1.08 -0.75 -0.77 -0.33 -0.66 -1.54 -1.71 -1.62 -1.68 -0.79 δ C 13 δ -26.81 -26.50 -26.59 -26.64 -26.07 -26.09 -25.84 -26.10 -26.16 -26.12 -26.05 -27.19 -27.13 -27.27 -30.43 -30.54 -30.36 -30.30 -26.58 -26.83 -27.00 -29.56 -29.57 -29.48 -29.37 -27.32 A A A A A A A A A A A A A U U U U U U U U U U U U U Acidified

0 0 1 0 0 0 0 1 2 3 0 0 0 0 0 0 0 1 0 0 0 0 1 0 0 0 rep Lab A B B C A B C C C C C A B C A B C C A B C A A B C A split Sample Date 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 Sample detail Chehalis soil Chehalis soil Chehalis soil Chehalis soil soil Wapato soil Wapato soil Wapato soil Wapato soil Wapato soil Wapato soil Wapato soil Woodburn soil Woodburn soil Woodburn Ash leaf litter Oregon Ash leaf litter Oregon Ash leaf litter Oregon Ash leaf litter Oregon Red Cedar litter Western Red Cedar litter Western Red Cedar litter Western Alder leaf litter Alder leaf litter Alder leaf litter Alder leaf litter Douglas Fir litter N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split N) and C/N ratios for samples collected from the Tualatin 15 δ C, Sample type 13 δ Soil Soil Soil Soil Soil Soil Soil Soil Soil Soil Soil Soil Soil Soil Leaf litter Leaf litter Leaf litter Leaf litter Coniferous litter Coniferous litter Coniferous litter Leaf litter Leaf litter Leaf litter Leaf litter Coniferous litter Site name Values of stable isotope compositions ( Values

holding pond) holding pond) holding pond) holding pond) holding pond) holding pond) holding pond) holding pond) Grove) Jackson Bottom (between Miller Swale and Jackson Bottom (between Miller Swale and Jackson Bottom (between Miller Swale and Jackson Bottom (between Miller Swale and River) Tualatin Zurcher Farm (FernhillRoad near River) Tualatin Zurcher Farm (FernhillRoad near River) Tualatin Zurcher Farm (FernhillRoad near River) Tualatin Zurcher Farm (FernhillRoad near River) Tualatin Zurcher Farm (FernhillRoad near River) Tualatin Zurcher Farm (FernhillRoad near River) Tualatin Zurcher Farm (FernhillRoad near Oregon Graduate Institute (near Bronson Creek) Oregon Graduate Institute (near Bronson Creek) Oregon Graduate Institute (near Bronson Creek) Jackson Bottom (between Miller Swale and Jackson Bottom (between Miller Swale and Jackson Bottom (between Miller Swale and Jackson Bottom (between Miller Swale and River at RM 67.8 (Cherry Grove) Tualatin River at RM 67.8 (Cherry Grove) Tualatin River at RM 67.8 (Cherry Grove) Tualatin River at RM 67.8 (Cherry Grove) Tualatin River at RM 67.8 (Cherry Grove) Tualatin River at RM 67.8 (Cherry Grove) Tualatin River at RM 67.8 (Cherry Grove) Tualatin Road (N side, 1 mi E Cherry Valley Patton ID 411 411 411 411 411 411 411 410 410 410 410 412 412 412 413 413 413 413 414 414 414 415 415 415 415 416 Appendix A. samples.—Continued 58 Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon C/N qualifier 3.54 4.85 5.27 5.09 3.65 3.66 3.63 3.58 C/N 58.32 57.19 58.59 74.40 86.49 48.21 57.48 N L 15 δ qualifier N 15 -0.50 -0.41 -0.49 -2.94 -2.75 -2.82 -2.96 11.82 11.88 11.84 10.91 16.13 16.22 16.26 15.92 δ C 13 δ -27.40 -27.55 -27.36 -26.04 -26.55 -26.72 -26.62 -26.75 -26.70 -26.49 -26.62 -35.63 -35.40 -35.07 -35.32 A A A A A A A A U U U U U U U Acidified

0 1 0 0 0 0 1 0 0 0 1 0 0 0 1 rep Lab B B C A B C C A B C C A B C C split Sample Date 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 10-06-98 08-13-98 08-13-98 08-13-98 08-13-98 — — — — — — — — Sample detail Douglas Fir litter Douglas Fir litter Douglas Fir litter Douglas fir twigs Douglas fir twigs Douglas fir twigs Douglas fir twigs N) and C/N ratios for samples collected from the Tualatin River basin, Oregon, including all analyzed split N) and C/N ratios for samples collected from the Tualatin 15 δ C, Sample type 13 δ particulate particulate particulate particulate Coniferous litter Coniferous litter Coniferous litter material Woody material Woody material Woody material Woody WWTF effluent WWTF effluent WWTF effluent WWTF effluent Bryozoan Bryozoan Bryozoan Bryozoan Site name Values of stable isotope compositions ( Values

Grove) Grove) Grove) Grove) Grove) Grove) Grove) Patton Valley Road (N side, 1 mi E Cherry Valley Patton Road (N side, 1 mi E Cherry Valley Patton Road (N side, 1 mi E Cherry Valley Patton Road (N side, 1 mi E Cherry Valley Patton Road (N side, 1 mi E Cherry Valley Patton Road (N side, 1 mi E Cherry Valley Patton Road (N side, 1 mi E Cherry Valley Patton Facility Treatment Wastewater Rock Creek Facility Treatment Wastewater Rock Creek Facility Treatment Wastewater Rock Creek Facility Treatment Wastewater Rock Creek Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin Road) River at RM 5.5 (Stafford Tualatin ID 416 416 416 417 417 417 417 418 418 418 418 419 419 419 419 Appendix A. samples.—Continued Publishing support provided by the U.S. Geological Survey Publishing Network, Tacoma Publishing Service Center

For more information concerning the research in this report, contact the Director, Oregon Water Science Center U.S. Geological Survey 2130 SW 5th Avenue Portland, Oregon 97201 http://or.water.usgs.gov Bonn and Rounds— Use of Stable Isotopes to Identify Sources of Organic Matter to Bed Sediments of the Tualatin River, Oregon—Scientific Investigations Report 2010–5154