Field deployment of polyethylene devices to measure PCB concentrations in pore water of contaminated sediment.
ABSTRACT Sediment pore water concentrations of polychlorinated biphenyls (PCBs) in a contaminated mudflat in San Francisco Bay, CA were determined by field-deployed polyethylene devices (PEDs). Sequential sampling of PEDs deployed in the field showed large differences in uptake rates and time to equilibrium compared to PEDs mixed with field-collected sediment in the laboratory. We demonstrate a modeling approach that involves the use of impregnated performance reference compounds (PRCs) and interpretation of the data either by PCB molar volume adjustment or environmental adjustment factors to measure pore water concentrations of 118 PCB congeners. Both adjustment methods predicted comparable sampling rates, and PCB pore water concentrations estimated by use of the molar volume adjustment method were similar to values analytically measured in pore waters from the laboratory and field. The utility of PEDs for sampling pore water in the field was evaluated at a tidal mudflat amended with activated carbon to sequester PCBs. Pore water concentrations decreased up to 60% within 18 months after activated carbon amendment, as compared to a mechanical-mixed control plot Results of this study illustrate PEDs provide an inexpensive, in situ method to measure total PCB contamination in sediment pore water using a small set of PRCs.
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ABSTRACT: Pore concentration and partition coefficients of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) were determined in sediments from five distinct contaminated sites in France (marine harbour, rivers canals and highway sedimentation tank). The assessment of the risk caused by such micropollutants requires, in most cases, the measurement of their availability. To assess this availability, low density polyethylene (LDPE) membrane samplers were exposed to these sediments under constant and low-level agitation over a period of 46days. Freely dissolved pore water contaminant concentrations were estimated from the concentration at equilibrium in the LDPE membrane. The depletion of contaminants in the sediments was monitored by the use of performance reference compounds (PRCs). Marked differences in freely dissolved PAH and PCB concentrations and resulting sediment-pore water partition coefficients between these five sediments were observed. Data set was tested onto different empirical and mechanistic models. As final findings, triple domain sorption (a total organic carbon, black carbon and oil phase model) could model PCB data successfully whereas the best fitting for PAH partitioning was obtained by Raoult's Law model.Science of The Total Environment 12/2013; · 3.16 Impact Factor
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ABSTRACT: Hydrophobic organic compounds (HOCs) like polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) tend to accumulate in sediment beds when they are released into aquatic environments. Due to this buildup of HOCs in the sediment, the highest water concentrations are often in the pore water. Passive samplers can be used in the field (i.e., in situ) to measure freely-dissolved porewater concentrations if target contaminants diffusing through the sediment and into the sampler exhibit the same diffusive retardation factors as performance reference compounds (PRCs) that are diffusing out of the sampler and into the sediment. To test this assumption, polyethylene (PE) passive samplers were placed in an organic- and black- carbon-rich sediment bed in the laboratory with samplers removed every 30 days for 4 months. The concentrations of target contaminants built up in the PE at each time point, corrected using measures of the losses of PRCs, were in good agreement with separately measured equilibrium concentrations in a well-mixed system. Concentrations in the PE passive samplers, normalized by their polyethylene-water partition coefficients, were also in good agreement with directly-measured porewater concentrations. Finally, PE-deduced porewater concentrations were compared with the traditional equilibrium partitioning models and showed that considering sorption to only organic carbon substantially overestimated porewater concentrations. However, predictions improved greatly if sorption to black carbon was also considered.Environmental Science and Technology 08/2014; · 5.48 Impact Factor
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ABSTRACT: This paper details how activity-based passive sampling methods (PSMs), which provide information on bioavailability in terms of freely dissolved contaminant concentrations (Cfree ), can be used to better inform risk management decision-making at multiple points in the process of assessing and managing contaminated sediment sites. Because Cfree is a better predictor of bioavailability than total bulk sediment concentration (Ctotal ) for four key endpoints included in conceptual site models (benthic organism toxicity, bioaccumulation, sediment flux, and water column exposures), PSMs can increase certainty in site investigation and management. Because of their small size, the use of PSDs presents particular challenges with respect to representative sampling for estimating average concentrations and other metrics relevant for exposure and risk assessment. These challenges can be addressed by designing studies that account for sources of variation associated with the PSDs and spatial scales. Possible applications of PSMs include: quantifying spatial and temporal trends in bioavailable contaminants; identifying and evaluating contaminant source contributions; calibrating site-specific models; and, improving weight-of-evidence based decision frameworks. PSM data can be used to: assist in delineating sediment management zones based on likelihood of exposure effects; monitor remedy effectiveness; and, evaluate risk reduction after sediment treatment, disposal, or beneficial reuse following management actions. Examples are provided illustrating why PSMs and Cfree should be incorporated into contaminated sediment investigations and study designs to better understand and focus on contaminant bioavailability, more accurately estimate exposure to sediment-associated contaminants, and better inform risk management decisions. Research and communication needs for encouraging broader use are discussed. Integr Environ Assess Manag © 2013 SETAC.Integrated Environmental Assessment and Management 12/2013;