Supplementary data for "Co-deployment of passive samplers and mussels reveals major source of ongoing PCB inputs to the Anacostia River in Washington DC"
Remedial investigations of sites contaminated with legacy pollutants like polychlorinated biphenyls (PCBs) have traditionally focused on mapping sediment contamination to develop a site conceptual model and select remedy options. This sediment-focused approach often leads to an incomplete understanding of the impacts of ongoing inputs to the water column and over-estimation of potential effectiveness of sediment remediation. Here we demonstrate the utility of co-deployment of passive equilibrium samplers and freshwater mussels as dual lines of evidence to identify ongoing sources of PCBs from eight main tributaries of the Anacostia River in Washington, DC that has been historically polluted from industrial and other human activities. The freely dissolved PCB concentrations measured using passive samplers tracked well with the accumulation in mussels and allowed predictions of biouptake within a factor of 2 for total PCBs and a factor of 4 for most congeners. One tributary was identified as the primary source of PCBs to the water column and became a focus of additional ongoing investigations. Co-deployment of passive samplers and mussels provide strong lines of evidence to identify ongoing sources critical to control to achieve river water quality standards and reduce bioaccumulation in the aquatic food web.
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Passive samplers (low density polyethylene sheet 2mil PE pre-impregnated with performance reference compounds PRC) were deployed in duplicate in the water column and porewater of the five major tributaries of Anacostia River for a period of two-three months during summer 2016 and 2017 along with caged freshwater mussel (adult Elliptio complanata collected at a clean reference site, i.e. Zekiah Swamp). Five to six cages were deployed per site, containing each eight mussels. Passive samplers were also deployed in the water column of three minor tributaries and at five locations in the main stem of the river. Water column deployment was repeated in Spring, Fall and Winter 2017. PCBs were extracted from PE with hexane and the extract was cleaned using EPA SW-846 methods 3660B and 3630C before analysis on GC-ECD. Mussels were depurated overnight, soft tissue were homogenized, composited (3 mussels per cage), freeze-dried and extracted for PCBs using EPA SW-846 methods 3550B, 3665A, 3660B, and modified 3620C, then analyzed on GC-ECD. PCB congener 14 and 65 were spiked at the beginning of the extraction and used as surrogate. PCB congener 30 and 204 were spiked in the sample before the run on the GC and used as internal standards. Software Chemstation was used for PCB peak identification and quantification. Sample exhibiting surrogate recovery outside of acceptable range (<60%, >140%) were removed from the dataset. Lipid content were also measured in the freeze-dried mussel tissue using methods described in Smedes et al (1999). Passive sampler data was normalized per gram of PE and further corrected at the congener level based on PRC loss as described in Sanders et al (2018). Samples exhibiting aberrant PRC loss regression (ke vs Kow or Kd vs Kow) were removed from the dataset. PCB congeners exhibiting a fractional equilibrium below 0.1 were not reported. PCB congener concentrations in the water column were back calculated using partitioning coefficient Kpew as reported in the dataset. The present dataset was not corrected for water temperature. Mussel data was normalized per mass of wet tissue. Water content and lipid content is reported to perform other normalization as required. References: Gray, M. W.; Kreeger, D. Monitoring Fitness of Caged Mussels (Elliptio Complanata) to Assess and Prioritize Streams for Restoration. Aquat. Conserv. Mar. Freshw. Ecosyst. 2014, 24 (2), 218–230. https://doi.org/10.1002/aqc.2395. Smedes, F. Determination of Total Lipid Using Non-Chlorinated Solvents. Analyst 1999, 124, 1711–1718. Sanders, J. P.; Andrade, N. A.; Ghosh, U. Evaluation of Passive Sampling Polymers and Nonequilibrium Adjustment Methods in a Multiyear Surveillance of Sediment Porewater PCBs. Environ. Toxicol. Chem. 2018, 37 (9), 2487–2495. https://doi.org/10.1002/etc.4223