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Evaluation of Polyethylene Passive Samplers to Estimate Deep Water PCB Concentrations at the Palos Verdes Shelf Superfund Site
Citation:
Burgess, R., R. Lohmann, P. Luey, M. Charpentier, AND C. White. Evaluation of Polyethylene Passive Samplers to Estimate Deep Water PCB Concentrations at the Palos Verdes Shelf Superfund Site. Presented at Society of Environmental Toxicology and Chemistry (SETAC). 33rd Annual Meeting, Long Beach, CA, November 11 - 15, 2012.
Impact/Purpose:
This abstract describes a study evaluating the use of passive samplers in the deep waters of the Palos Verdes Shelf Superfund site to monitor PCB concentrations.
Description:
The Palos Verdes Superfund site is located in over 50 meters of water on the continental shelf and slope off the coast of southern California (USA). The site includes 27 km2 of seabed contaminated over several decades by municipal treatment plant effluent discharged via outfall pipes at a depth of 60 meters. Contaminants of concern include industrial chemicals like polychlorinated biphenyls (PCBs) and the pesticide DDT and its degradation products. Planned remediation of the site includes capping of erosive areas designated as hot spots with clean capping material. A risk to the Palos Verdes system is contaminated sediment resuspension as capping material is placed on the seafloor. Resuspension of sediments and resulting desorption of dissolved contaminants into the water column could cause aqueous concentrations of PCBs and DDTs to exceed marine water quality criteria (WQC). For this preliminary pre-remediation investigation, passive sampling polyethylene devices (PEDs) were deployed on current meters one to five meters above the seabed with various levels of sediment contamination for three to six months at seven stations. The objectives of these measurements were to (1) evaluate the use of passive samplers in deep waters and (2) quantify baseline concentrations of dissolved PCBs in water above the sediments and assess their transport from the site. PEDs absorb contaminants from the water column and provide a robust method for estimating dissolved contaminant concentrations at very low levels conventional water sampling procedures would not be able to detect. At this site, PEDs functioned well as monitoring tools with concentrations of total PCBs ranging from 60 to 400 ng/g polyethylene which corresponds to estimated water column dissolved concentrations of 90 to 1000 pg/L. Mean flow measured by the current meters is along the shelf toward the northwest. Water column PCB concentrations were highest above and to the northwest of the most contaminated sediments, suggesting PCBs are partitioning into the water column from the more contaminated sediments and being transported northwest from the Superfund site by the mean current. These preliminary baseline data, along with more extensive water column baseline monitoring data, will be compared to similar measures taken during and after the remediation to access the magnitude of contaminant release and probability of exceeding WQC.