Nueces Bay Zinc in Sediment Profiling Assessment Publication CBBEP – 91 Project Number – 1313 January 31, 2014 Prepared by Erin M. Hill, Principal Investigator Mark Besonen, Co-Principal Investigator Brien Nicolau Center for Coastal Studies Texas A&M University-Corpus Christi 6300 Ocean Drive, Suite 3200 Corpus Christi, TX 78412 and Philippe Tissot, Co- Principal Investigator Conrad Blucher Institute Sediment Analysis and Radioanalysis Laboratory Texas A&M University-Corpus Christi 6300 Ocean Drive, Suite 2801 Corpus Christi, TX 78412 Submitted to: Coastal Bend Bays & Estuaries Program 1305 N. Shoreline Blvd., Suite 205 Corpus Christi, TX 78401 The views expressed herein are those of the authors and do not necessarily reflect the views of CBBEP or other organizations that may have provided funding for this project. Nueces Bay Zinc in Sediment Profiling Assessment Final Report by: Erin M. Hill, Principal Investigator Center for Coastal Studies Texas A&M University-Corpus Christi 6300 Ocean Drive, Suite 3200 Corpus Christi, TX 78412 [email protected] Mark Besonen, Co- Principal Investigator Earth System Science Laboratory Texas A&M University-Corpus Christi 6300 Ocean Drive, Suite 3200 Corpus Christi, TX 78412 [email protected] Philippe Tissot, Co- Principal Investigator Conrad Blucher Institute Sediment Analysis and Radioanalysis Laboratory Texas A&M University-Corpus Christi 6300 Ocean Drive, Suite 2801 Corpus Christi, TX 78412 [email protected] Brien A. Nicolau Center for Coastal Studies Texas A&M University-Corpus Christi 6300 Ocean Drive, Suite 3200 Corpus Christi, TX 78412 [email protected] Nueces Bay Zinc in Sediment Profiling Assessment Project 1313 Reporting period: 1September 2012 to 31 January 2014 Date of submission: 31 January 2014 SUBMITTED TO: Coastal Bend Bays & Estuaries Program 1305 N. Shoreline Blvd., Suite 205 Corpus Christi, TX 78401 TAMU-CC-1302-CCS Executive Summary This project addressed two important questions and complements the ongoing TMDL and Implementation Plan for zinc in Nueces Bay. This project (1) identified a legacy layer of zinc in the sediment of Nueces Bay and (2) determined that zinc sediment concentrations that are currently detected in the surficial layer are likely legacy but are also representative of the present zinc loading to Nueces Bay. From 1941-1985 the American Smelting and Refining Company (ASARCO) was a high-grade zinc production facility located on the south side of Nueces Bay on approximately 108 acres. The ASARCO/ENCYCLE facility is located along the northern side of the Corpus Christi Inner Harbor (CCIH) and borders McBride Lane and Valero Refining to the east, and Up River Road and Dona Drive on the south (http://www.tceq.texas.gov/remediation/sites/encycle_facility/encycle). This facility discharged contaminated effluent into Nueces Bay and the CCIH during its period of operation (TCEQ 2006, 2007, 2008, 2010). It is presumed that Nueces Bay received legacy zinc loadings through the Central Power and Light (CPL) electrical generating station that used CCIH water as once pass-through cooling water for facility operations until the operations ceased in December 2002 (Mrini et al. 2003). In 2004, Topaz Power Group purchased the CPL electric facility and began construction in 2008. The electric facility is now the Nueces Bay Energy Center and became commercially operational in 2010 (http://www.topazpowergroup.com/power-plants/nueces-bay-power-plant). The Nueces Bay Energy Center began discharging into Nueces Bay in 2010 (Permit No. WQ0001244-000). The Texas Department of Safety and Health Services (DSHS) closed Nueces Bay to the harvesting of oysters in January 1995 under authority of Chapter 436 of the Texas Health and Safety Code (DSHS 2003; DSHS 2005). Following the 1995 oyster closure, Nueces Bay was put on the Texas Water Quality Inventory and 303(d) List for impaired oyster waters. The DSHS collected oysters from Nueces Bay in 2002 and again found elevated zinc levels in oysters ranging from 479-2300 mg/kg (CBBEP 2005). Since 2006, a Total Maximum Daily Load (TMDL) has been implemented in Nueces Bay (Segment 2482) for zinc in oyster tissue not meeting the State of Texas acceptable level of <700 mg/kg. The TMDL established total zinc criterion for surface water in Nueces Bay is 29 μg/L. For all other marine waters in the State of Texas the TCEQ established criteria for dissolved zinc in water is 87.2 μg/L and zinc in sediment is 410 mg/kg. Nine (9) TCEQ stations in Nueces Bay were sampled in June 2013. Mean water temperature was 28.93° C with station 14833, located near the Topaz Power Group’s Nueces Bay Energy Center, having the warmest reading at 30.40° C. Mean salinity was 38.2 ppt with station 18866 located in back Nueces Bay having the highest salinity at 40.09 ppt. Mean pH was 7.93 and mean DO % and mg/L were 90.94 and 5.65, respectively. A legacy layer of zinc was identified in sediment cores in the southern part of Nueces Bay near the historical ASARCO/ENCYCLE and Central Power and Light (CPL) discharge points (Fig. 1 and Fig. 2). Based on the min and max sediment profile zinc concentrations it was determined the natural occurring zinc in sediment in Nueces Bay appears to be < 124 mg/kg in the middle and northern parts of the bay. This concentration is below the Threshold Effects Level (TEL) based on Long et al. (1995) classification (Long et al. 1995; MacDonald et al. 1996) but Stations 18619 and ii 14833 had zinc concentrations within the Effects Range Level (ERL) and Station 21484 exceeded the Effects Range Median (Table 4). Station 21484 is the only station out of the 9 that appears to have undisturbed sediments and therefore is the focus for dating purposes. Figure 1. Maximum concentration of zinc in sediment (mg/kg) collected from Nueces Bay sediment profile assessment. iii Figure 2. Zinc concentration profiles for Nueces Bay sediment cores from 0-100 cm depth. The horizontal scale for all nine plots is identical, and ranges from 0-450 mg/kg. The graticules mark increments of 10 cm in the vertical direction, and 50 mg/kg in the horizontal direction. The profiles have a blocky appearance because samples were analyzed in 5 cm stratigraphic intervals. iv Though attempts at directly dating the stratigraphy by radioanalysis of 137Cs/210Pb were problematic, we suggest an alternative indirect dating solution based on a historical analysis of ASARCO zinc production rates, and the zinc concentrations seen in the sediment core from Station 21484. Historical references were gathered from a variety of sources to assemble an estimated zinc production rate curve for the ASARCO plant from the start of production (October 1942) up to the closure of the facility in 1985. The production rate curve is admittedly an estimate because it is built from both hard and inferred/anecdotal data (see http://www.tshaonline.org/handbook/online/articles/dkl01). Altogether, these data points were used to assemble the production rate curve seen in (Fig. 3). Figure 3. Estimated zinc production rate at ASARCO plant based on historical analysis. The curve shows a rapid ramp up in 1942 when the plant first came online in October of that year to help with production for World War II. A second quick ramp up occurs in the early 1950’s, and is probably related to production increases for the Korean War. Another ramp occurs from 1960-1961 because ASARCO brought online a new plant that essentially doubled its production capacity. And then from 1970 onward the production rate decreases till the plant finally closed in 1985. If we assume that the amount of effluent from the plant is proportional to the overall zinc production rate, the estimated historical production rate curve shows a remarkable similarity to the shape of the zinc concentration levels seen in the sediment core from Station 21484. This can be seen in Figure 4, which shows multiple data sets plots along the length of the core. In this figure, v the estimated historical production rate curve has been overlaid on to the zinc concentration data to show the notable correspondence between the two curves. We therefore offer this as an indirect dating solution for the stratigraphy at Station 21484. Station 21484 zinc data clearly shows current surficial zinc deposition in Nueces Bay is lower than historical loads related to ASARCO/ENCYLE operations. This study identified sinks or hotspots in Nueces Bay where zinc has the potential to be rereleased back into the water column via natural or human disturbance. Current surficial levels of zinc collected from this study are below TCEQ’s 410 mg/kg criteria however, at deeper levels elevated concentrations exist. Reduced surficial zinc concentrations may be contributed to natural sedimentation rates in Nueces Bay reducing surface zinc concentrations or biological uptake via filtering from the oyster population in Nueces Bay. Future projects involving activities which disturb sediments in Nueces Bay can be better managed since areas with elevated levels of zinc have been identified. vi Figure 4. High-resolution multi-proxy results for the Station 21484 sediment core. This figure shows a color image of the longitudinally-split core from Station 21484 from 0-100 cm (image at left) along with ten data sets produced from analyses along the length of the core (gray dotted lines indicate 10 cm increments). Note that the estimated historical zinc production curve (dotted red curve) is overlaid on to the zinc concentration data, and their shapes are remarkably coincident. Based on this relationship, estimated ages for the stratigraphy are presented alongside the grain size data plot. The ten data sets are split into two groups. The first three data sets with the blocky appearance are from the composited, extruded sediment cores.