Resuspension of polychlorinated biphenyl‐contaminated field sediment: release to the water column and determination of site‐specific K_DOC

Abstract

Sediments from the New Bedford Harbor (NBH) U.S. Environmental Protection Agency (U.S. EPA) Superfund site (Massachusetts, USA), contaminated with polychlorinated biphenyls (PCBs), were resuspended under different water column redox conditions: untreated, oxidative, and reductive. The partitioning of PCBs to the overlying water column was measured with polyethylene samplers and compared to partitioning without resuspension. Greater concentrations of total aqueous (freely dissolved + dissolved organic carbon (DOC)-associated) PCBs were found in all resuspended treatments for PCBs with mid-range K(OW)s, but no difference was observed in total aqueous concentrations among different redox conditions. The magnitude of increased concentrations depended on resuspension time and congener K(OW), but ranged from approximately one to eight times those found without resuspension. In a parallel study, DOC was flocculated and removed from smaller-scale NBH sediment resuspensions. In situ K(DOC)s were determined and used to calculate freely dissolved and DOC-associated fractions of the increase in total aqueous PCB concentrations due to resuspension. The importance of DOC-associated PCBs increased with increasing K(OW). In situ K(DOC)s were approximately one to two orders of magnitude greater than those calculated with a commonly used linear free energy relationship (LFER). The present study demonstrates that resuspension of contaminated sediments releases PCBs to the water column, of which a significant fraction are DOC-associated (e.g., 28, 65, and 90% for PCBs 28, 66, and 110, respectively). Results also imply that site-specific PCB K(DOC)s are superior to those calculated with generic LFERs.

Challenges of Using Polyethylene Passive Samplers to Determine Dissolved Concentrations of Parent and Alkylated PAHs under Cold and Saline Conditions

“…36 A similar conclusion was previously reached by Friedman et al, who reported that polychlorinated biphenyls (PCBs) in the New Bedford Harbor estuary sorbed 5−20 times stronger to DOC than predicted. 37 We included results for the DOC correction of apparent dissolved PAH concentrations from liquid−liquid extraction assuming that DOC sorbed PAHs 5 times stronger than predicted by Burkhard,36 resulting in better agreement between HMW PAHs from both methods.…”

Evaluating the Relationship between Equilibrium Passive Sampler Uptake and Aquatic Organism Bioaccumulation

“…The equilibrium status of the target contaminants can be calculated and used to adjust for nonequilibrium conditions by measuring the loss of PRCs following the deployment. There are currently at least three approaches recommended for making the nonequilibrium calculations using the raw PRC concentrations including a first order equation, − a diffusion-based model, ,, and a sampling rate-based correction . When using PRCs, it is worth noting that for highly hydrophobic contaminants, the passive sampler may accumulate relatively low concentrations while under nonequilibrium conditions making quantification analytically challenging.…”

Passive sampling methods for contaminated sediments: Scientific rationale supporting use of freely dissolved concentrations

“…Adams () observed a doubling of C free levels in the Hudson River estuary during spring tide resuspension events; this change was not seen during the neap tides when resuspension was much weaker. Friedman et al () studied the impact of large‐scale resuspension of native sediments on the release of PCBs to the water column using passive samplers. The magnitude of increased concentrations depended on resuspension time and the K ow of the congener ranging from 1 to 8 times those found without resuspension.…”