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Passive Sampling to Measure Baseline Dissolved Persistent Organic Pollutant Concentrations in the Water Column of the Palos Verdes Shelf Superfund Site
Citation:
Fernandez, L., W. Lao, K. Maruya, C. White, AND R. Burgess. Passive Sampling to Measure Baseline Dissolved Persistent Organic Pollutant Concentrations in the Water Column of the Palos Verdes Shelf Superfund Site. ENVIRONMENTAL SCIENCE AND TECHNOLOGY. John Wiley & Sons, Ltd., Indianapolis, IN, 46(21):11937-11947, (2012).
Impact/Purpose:
This paper demonstrates the effective use of passive sampling to determine baseline concentrations of legacy contaminants in the water column of a U.S. EPA Superfund site. These data will be compared to future water column concentrations as the site undergoes remediation activity.
Description:
Passive sampling was used to deduce water concentrations of persistent organic pollutants (POPs) in the vicinity of a marine Superfund site on the Palos Verdes Shelf, California, USA. Pre-calibrated solid phase microextraction (SPME) fibers and polyethylene (PE) strips that were pre-loaded with performance reference compounds (PRCs) were co-deployed for 32 d along an 11 station gradient at bottom, surface and mid-water depths. Retrieved samplers were analyzed for DDT congeners and their breakdown products (DDE, DDD, DDMU, and DDNU) and 43 PCB congeners using GC-EI- and NCI-MS. PRCs were used to calculate compound-specific fractional equilibration achieved in situ for the PE samplers, using both an exponential approach to equilibrium model (EAE) and numerical integration of Fickian diffusion (NI) models. The highest observed concentrations were for p,p’-DDE, 2200 pg/L and 990 pg/L deduced from PE and SPME, respectively. The difference in these estimates could be largely attributed to uncertainty in equilibrium partition coefficients, unaccounted for disequilibrium between samplers and water, or different time scales over which the samplers average. The concordance between PE and SPME estimated concentrations for DDE was high (R2 = 0.95). PCBs were only detected in PE samplers, due to their much larger size. Near-bottom waters adjacent to and down current from sediments with the highest bulk concentrations exhibited aqueous concentrations of DDTs and PCBs that exceeded Ambient Water Quality Criteria (AWQC) for human and aquatic health, indicating the need for future monitoring to determine the effectiveness of remedial activities taken against the most highly contaminated surface sediments.