Bioavailability of contaminants in sediment is an important consideration in the determination of potential risk of adverse effects from exposure to benthic invertebrate.
Numerous tools are used to assess bioavailability, including measurement of contaminants in tissue via bioaccumulation testing and sediment porewater with passive sampling. These tools and different methods of applications vary in cost effectiveness, efficiency, and ability to incorporate field conditions.
The performance a thin-layer habitat enhancement sand cap (target depth 6 inches) to reduce bioavailable concentrations of organochlorine pesticides (e.g., 4,4’-dichlorodiphenyldichloroethane [4,4’-DDD] and 4,4’-dichlorodiphenyldichloroethylene [4,4’-DDE]) in sediment was evaluated at Site 99 Quantico Embayment in the Quantico Marine Corps Base, Quantico, Virginia, USA. The thin-layer cap placement is expected to reduce concentrations of total DDX in sediment more rapidly than natural recovery processes alone. Prior to and following installation of the cap, monitoring at the site included three tools to assess bioavailability. Concentrations of pesticides in tissue were obtained via two-week deployment of in situ bioaccumulation testing with Sediment Ecotoxicity Assessment (SEA) Rings using two species, Lumbriculus variegatus (oligocheaete worm) and Corbicula fluminea (Asian clam). Secondly, a two-week deployment of in situ solid phase microextraction (SPME) passive sampling was used to measure porewater from 0 to 24 inches below the sediment-water interface. Lastly, ex situ SPME was also used to measure porewater at multiple depth intervals within and below the cap.
Strong correlation between concentrations of total DDX in worm tissue and surface sediment porewater as measured by both in situ and ex situ passive sampling approaches was observed. However, weak correlation of total DDX concentrations in clam tissue and surface sediment porewater as measured by both in situ and ex situ passive sampling approaches was observed, likely due to the filter feeding clam being exposed to overlying water rather than sediment porewater (moderate correlation between worm and clam tissue was observed).
- Geosyntec Authors: Melissa Grover
- All Authors: Melissa Grover
- Title: 37th SETAC North America Annual Meeting
- Event or Publication: Event
- Practice Areas: Contaminated Sites, Environmental Management
- Citation: November 6-10, 2016
- Date: 2016
- Location: Orlando, Florida