In Situ Stabilization of Persistent Organic Contaminants in Marine Sediments
Abstract
Effective management of polychlorinated biphenyls (PCBs) in sediments is challenging and expensive. Hydrophobic organic compounds (HOCs) such as PCBs, PAHs, and DDT associate with fine-grained, organic-rich, sediment material. This serves as a contaminant reservoir in shallow estuarine and coastal regions from which fish and bottom-dwelling organisms accumulate toxic compounds passed up the food chain. However, recent work at Stanford University and elsewhere proposes that the bioavailability of hydrophobic organic contaminants depends on how weakly or strongly they are sorbed to sediment organic matter. We find that black carbon particles in a wide variety of sediments act as strong sorbents, which naturally over time tend to concentrate HOCs and make these compounds less available for organisms. Building on these observations, we have tested a new concept for sediment management based on addition of activated carbon to sediment to repartition hydrophobic organic compounds in the sediment, reducing biological uptake and leaching into the overlying water. Sediment from the inter-tidal zone of South Basin, Hunters Point Naval Shipyard, San Francisco Bay (cover picture), was used in this research. Sampling took place during low tide along approximately 150 yards of shoreline within the inter-tidal zone as shown in Figure 1. Historic shipyard and industrial activities in the adjacent region discharged PCBs, PAHs, and heavy metals into the soil and sediment. Previous sampling at the site has shown high PCB and PAH concentrations and this site currently is under investigation for remedial action. Sediment characterization was carried out for the bulk material and also for size and density separated fractions. The total PCB concentration was 9.9 (0.9) mg/kg with predominantly higher chlorinated congeners and resembling Aroclor 1260 in congener distribution. The concentration of 16 EPA priority pollutant PAHs was 8 mg/kg and the total organic carbon (TOC) was 1.7 mg/kg.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 2004
- Accession Number
- ADA604123
Entities
People
- Jeffrey W. Talley
- John R. Zimmerman
- Pamela B. Mcleod
- Richard G Luthy
- Richard Zare
- Rod N. Millward
- Tania Mahajan
- Todd S. Bridges
- Upal Ghosh
Organizations
- Engineer Research and Development Center