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USING SPMDS TO ACCESS MANAGEMENT STRATEGIES FOR PCB CONTAMINATED SEDIMENTS
Citation:
SchubauerBerigan, J, R C. Brenner*, J M. Lazorchak, T. Lyons,T.M., Foote, V. S. Magar, J. E. Abbott, AND Eastep. USING SPMDS TO ACCESS MANAGEMENT STRATEGIES FOR PCB CONTAMINATED SEDIMENTS. Presented at Society of Environmental Toxicology and Chemsitry Annual Meeting, Austin, TX, 11/9-11/03.
Description:
Dredging, in-place treatment, capping and monitored natural recovery, used together or separately are the primary approaches for managing contaminated sediment risks. Understanding how well different approaches work in different environments is critical for choosing an appropriate approach to predictably reduce human and ecological risks. We present the results of a field test of some new sampling devices/approaches we developed to evaluate the effectiveness of risk management strategies for PCB contaminated sediments. This work is part of a larger team effort that includes concurrent studies of sediment respiration, PCB sediment and water profiling, PCB sediment diffusion, PCB water/air volatilization, and PCB biota uptake. The work was conducted at Lake Hartwell, SC, a reservoir contaminated with PBCs. The site is currently being managed using Monitored Natural Recovery (MNR). Historic PCB surface sediment values reported in 1988 for the contaminated upper four miles of the lake range from ~5-65 ppm, but are significantly lower today (~0-6 ppm), primarily due to sedimentation and burial.
Commercially available semipermiable membrane devices (SPMDs), combined with new in-situ sediment sampling devices developed for this study, were evaluated and used to quantify PCB movement and availability between sediments and overlying water. Three locations in Lake Hartwell were examined, a background site (Bkgd) with little or no PCB contamination, a site with moderate contamination (M-N) and a site near the area of highest contamination (O). Time-weighted average (TWA) PCB availability was quantified using stainless steel (SS) racks (R) designed to hold SPMDs in contact with surface sediments, SS valved domes (D) designed to enclose and suspend SPMDs at the sediment water interface and SS cages, which were used for the water column (W) SPMDs. W SPMDs were deployed in triplicate for 28 d at each site and compared with caged minnows and Asian clams deployed for the same period. W SPMDs were also deployed in duplicate for 7, 14, and 56 d, at site O. Sediment SPMD racks and domes were deployed in triplicate for 56 d at all three locations. Additional racks were deployed in triplicate at all three sites for 14 and 28 d. Congener-specific PCB analysis was performed via mass spectrometry on all samples. As expected, regardless of the sampler used, SPMD TWA PCBs were highest at site O (D:473; R:1290; W:1607 ng/g/d) > M-N (D:194; R: 883; W: 1023 ng/g/d) > Bkgd site (D: 5; R: 16; W: 21 ng/g/d). TWA PCBs were highest in the W SPMD's (1607 ng/g/d) > R SPMDs (1290 ng/g/d)> D SPMD's (473 ng/g/d). Coefficient-of-variation for all groups was usually <10%. Time course studies of W and R SPMDs indicated no PCB saturation. Loading rates of the SPMDs appeared to be linear (W > R ). Loading rates of R SPMDs differed with respect to site (O> M-N > Bkgd). The design of sediment samplers also allows us to express TWA PCBs on an aerial basis.