Aquatic sediments are often the ultimate receptors of contaminants. Sediment contamination is particularly difficult to manage due to the tendency for contaminants to be retained within sediments for long periods of time. According to an estimate by the U.S. Environmental Protection Agency (U.S. EPA), approximately 10% or 1.2 billion cubic yards of the sediment underlying the country’s surface water is sufficiently contaminated with toxic pollutants to pose potential risks to fish and to humans and wildlife that eat fish. This represents the upper 5 centimeters of sediment where many bottom-dwelling organisms live, and where the primary exchange processes between the sediment and overlying surface water occur.
SERDP and ESTCP have been investing in technologies to improve our management of contaminated sediments for over 10 years. An overview of this research can be found at the Contaminated Sediments program page. The Program has hosted several expert panel workshops to guide investments in this area, with the most recent workshop held in 2012. The results of this workshop are summarized in the Workshop Report and have led to the selection of a suite of new projects focused on improving our understanding of the impact of ongoing, low-level contaminant influx to aquatic sediment site restoration.
Recontamination of sediments from off-site sources can slow or even reverse recovery. In most urban and industrial harbors and rivers, where it is unlikely that sources will be completely controlled, a fundamental technical challenge is assessing “How controlled is controlled?” This requires better scientific and technical capabilities to understand contaminant releases from these sources and how these source levels relate to potential recontamination of the sediment bed. This also drives a more rigorous approach to remedy selection and risk management that incorporates the resilience of remedies into the criteria for remedy selection (within the existing context of long-term effectiveness).
Four projects new for FY14 will be addressing different aspects of this issue.
- Dr. Phil Gschwend from MIT will be combining mass balance modeling with passive sampling to evaluate continuing inputs and food web responses to remedial actions under SERDP Project ER-2429.
- Dr. Danny Reible from Texas Tech University will be examining the impact of stormwater on recontamination of sediments in SERDP Project ER-2428.
- Dr. Todd Bridges from the U.S. Army ERDC will investigate the use of quantitative thermodynamic exposure assessment to support restoration resiliency under SERDP Project ER-2431.
- Dr. Anna Knox from Savannah River National Laboratory will work towards understanding the relationships among low level metal influx, remediated sediments, and biological receptors under SERDP Project ER-2427.