Persistent reductions in the bioavailability of PCBs at a tidally inundated Phragmites australis marsh amended with activated carbon

Abstract

In situ amendment of sediments with highly sorbent materials like activated carbon (AC) is an increasingly viable strategy to reduce the bioavailability of persistent, sediment-associated contaminants to benthic communities. Because in situ sediment remediation is an emerging strategy, much remains to be learned about the field conditions under which amendments can be effective, the resilience of amendment materials toward extreme weather conditions, and the optimal design of engineered applications. We report the results of a multiyear, pilot-scale field investigation designed to measure the persistence and efficacy of AC amendments to reduce the bioavailability of polychlorinated biphenyls (PCBs) in an intertidal Phragmites marsh. The amendments tested were granular AC (GAC), GAC with a layer of sand, and a pelletized fine AC. Key metrics presented include vertically resolved black carbon concentrations in sediment and PCB concentrations in sediment, porewater, and several invertebrate species. The results demonstrate that all 3 amendments withstood Hurricane Sandy and remained in place for the duration of the study, successfully reducing porewater PCB concentrations by 34 to 97%. Reductions in invertebrate bioaccumulation were observed in all amendment scenarios, with pelletized fine AC producing the most pronounced effect. The present findings support the use of engineered AC amendments in intertidal marshes and can be used to inform amendment design, delivery, and monitoring at other contaminated sediment sites. Environ Toxicol Chem 2018;37:2496-2505. © 2018 SETAC.

A Pilot-Scale Field Study: In Situ Treatment of PCB-Impacted Sediments with Bioamended Activated Carbon

“…PE passive samplers used to measure PCB concentrations in porewater were analyzed as described by Sanders et al 18 PCB concentrations in PE were converted to estimated PCB concentrations in the porewater phase based on equilibrium partitioning constants (K PE ) described by Ghosh et al 19 PCBs 29, 69, 103, 155, and 192 were included in the PE samplers as performance reference compounds to correct for nonequilibrium conditions and assess porewater concentration using the first order nonequilibrium correction method described in Oen et al 20 Gas chromatographic analysis of PCBs and chloroethenes is described in the SI (Text S3).…”

Evaluation of passive sampling polymers and nonequilibrium adjustment methods in a multiyear surveillance of sediment porewater PCBs

“…No trend with depth was apparent in plot B. In plot A, Σ C pw values were higher at each successive depth interval below 1 cm, suggesting a profile in loose accord with that of black carbon, measured separately (Sanders et al ). However, no statistically significant trend with depth could be determined because of variability in the data.…”

“…In the present study, passive sampling data were generated as part of a multiyear monitoring effort for a pilot-scale sediment remediation project, which is described in greater detail elsewhere (Sanders et al 2018). The goals of the passive sampling effort were as follows: 1) compare different sampling polymers in a remediated marsh setting; 2) compare different PRC adjustment methods; and 3) evaluate PRC adjustment methods in the context of altered sediment partitioning constant (K d ).…”

Evaluation of Manganese Oxide Amendments for Mercury Remediation in Contaminated Aquatic Sediments

“…The control (C) treatment contained no added amendment. The Mn treatment bucket contained a Carulite addition of 5% by dry weight, a common dose for sorbent sediment amendments. ,, The AC contained 1% granular activated carbon by dry weight. The lower amendment percentage in the AC treatment was intended to adjust for the higher specific surface area of the granular activated carbon compared to the Carulite, which was estimated to be five times larger based on the manufacturers’ reported values.…”