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An Assessment of Optical Properties of Dissolved Organic Material As Quantitative Source Indicators in the Santa Ana River Basin, Southern California

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An Assessment of Optical Properties of Dissolved Organic Material As Quantitative Source Indicators in the Santa Ana River Basin, Southern California An Assessment of Optical Properties of Dissolved Organic Material as Quantitative Source Indicators in the Santa Ana River Basin, Southern California By Brian A. Bergamaschi, Erica Kalve, Larry Guenther, Gregory O. Mendez, and Kenneth Belitz Prepared in cooperation with the Orange County Water District SIR 2005-5152 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior Gale A. Norton, Secretary U.S. Geological Survey P. Patrick Leahy, Acting Director U.S. Geological Survey, Reston, Virginia: 2005 For sale by U.S. Geological Survey, Information Services Box 25286, Denver Federal Center Denver, CO 80225 For more information about the USGS and its products: Telephone: 1-888-ASK-USGS World Wide Web: http://www.usgs.gov/ Any use of trade, product, or firm names in this publication 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: Bergamaschi, B.A., Kalve, E., Guenther, L., Mendez, G.O., and Belitz, K., 2005, An Assessment of Optical Properties of Dissolved Organic Material as Quantitative Source Indicators in the Santa Ana River Basin, southern California: U.S. Geological Survey Scientific Investigations Report 2005-5152, 38 p. iii Contents Abstract ...........................................................................................................................................................1 Introduction.....................................................................................................................................................1 Purpose and Scope ..............................................................................................................................1 Background............................................................................................................................................2 Acknowledgments ...............................................................................................................................3 Study Area Description ................................................................................................................................4 Sampling and Analytical Methods ..............................................................................................................6 Dissolved Organic Material.................................................................................................................6 Ultraviolet Absorbance .......................................................................................................................6 Fluorescence ........................................................................................................................................6 Data Analysis .........................................................................................................................................7 Definitions .....................................................................................................................................7 Excitation/Emission Pairs .................................................................................................7 Specific Ultraviolet Absorbance (SUVA) ........................................................................8 Specific Fluorescence Intensity ......................................................................................8 Modeling........................................................................................................................................8 Results and Discussion .................................................................................................................................9 Model Endmember Selection ...........................................................................................................11 Model Response to Blank and Replicate Samples ..............................................................14 Diurnal Variation .......................................................................................................................14 Large-Scale Trends ............................................................................................................................20 Results from Monthly Sampling .......................................................................................................21 South Fork of the Santa Ana River .........................................................................................21 Mentone ......................................................................................................................................24 Warm Creek ................................................................................................................................28 Metropolitan Water District Crossing ....................................................................................28 Cucamonga Creek at Highway 60 ...........................................................................................28 Inland Empire Utilities Agency Reclamation Plant 1 ............................................................29 Cucamonga Creek near Mira Loma ........................................................................................29 Prado .........................................................................................................................................29 Santa Ana River at Imperial Highway ....................................................................................30 Results from Storm Sampling ...........................................................................................................30 Results from Comparison to Common Materials ...........................................................................32 Results from Data Reduction ............................................................................................................32 Evaluation of Results ..........................................................................................................................35 Conclusions...................................................................................................................................................36 References Cited..........................................................................................................................................37 iv Figures Figure 1: Location of study area and land use in the Santa Ana River Basin, southern California ........................................................................................................................................4 Figure 2: Locations of sites sampled in the Santa Ana River Basin, southern California. .................5 Figure 3: Results of model application to synthetic data ........................................................................7 Figure 4: Comparison of (A) ultraviolet absorbance and dissolved organic material (DOM) con- centration content, (B) fluorescence intensity and DOM, and (C) specific fluorescence intensity and specific ultraviolet absorbance for samples collected in the Santa Ana River Basin, southern California. ..............................................................................................10 Figure 5: Fluorescence spectral response of representative endmember components used for the optical modeling of samples from the Santa Ana River Basin, southern California. ....................................................................................................................12 Figure 6: Comparison of model-derived endmember assignments for blank samples ....................14 Figure 7: Comparison of model-derived endmember assignments between duplicate samples collected in the Santa Ana River Basin, southern California. ............................................15 Figure 8: Diurnal changes in properties for samples collected between 1530 on July 29 and 0830 on July 30, 1999, Santa Ana River Basin, southern California. ............................................19 Figure 9: Comparison of properties measured in samples collected monthly in the Santa Ana River Basin, southern California. ..............................................................................................20 Figure 10: Model-derived endmember assignments for all samples collected at sites from which representative endmembers samples were selected ..........................................................25 Figure 11: Comparison of hydrologic and model-derived endmember assignments for two sites in the Santa Ana River Basin, southern California ................................................................31 Figure 12: Representative example of model-derived assignments using the full and reduced data sets .......................................................................................................................................33 Figure 13: Ternary diagram showing model apportionment of endmember contributions for fluorescence spectral data in samples collected monthly in the Santa Ana River Basin, southern California .....................................................................................................................35 v Tables Table 1: Concentrations of dissolved organic material, associated optical properties, and normalized parameters of surface-water samples from the Santa Ana
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