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Passive Sampling Methods for Contaminated Sediments

Challenge

Managing contaminated sediments requires accurate measurement of contaminant levels over time to evaluate risks to aquatic organisms and to monitor cleanup efforts. Of particular concern are the dissolved contaminants present in sediment porewater because they are more available to aquatic organisms than the contaminants bound to sediment particles. As the sediment contamination levels drop, concentrations of dissolved contaminants in porewater become more difficult to accurately quantify. Measuring dissolved contaminant concentrations in porewater by traditional methods can be challenging and often requires transporting large volumes of sediment from the field to an analytical laboratory and then separating porewater from sediment particles. 

Passive sampling offers an alternative that allows easier and more accurate measurement of the dissolved contaminants, provides lower detection limits, and eliminates the cost of transporting large and heavy samples back to the lab. Passive samplers use materials designed to adsorb certain contaminants. They can be left in the field to collect contaminants over time and then sent back to the lab for analysis. Battelle is improving passive sampling technologies and deployment methods to facilitate measurement of dissolved contaminants in sediment porewater, as well as surface water and groundwater. 

Solution

Battelle uses low-density polyethylene (LDPE) sheet-based passive samplers, also known as polyethylene devices (PEDs). These sheets are low cost, reliable and easy to adjust to different sizes and geometries for different applications. PEDs provide a reliable and cost-effective way to measure low levels of dissolved hydrophobic contaminants such as polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), chlorinated pesticides, and dioxins and furans. Typically, they are deployed in the field for up to a month. They can be used to measure freely dissolved contaminants in the water column, buried directly in sediment for shallow porewater measurements, or they can be placed in piezometers (screened pipes inserted into the sediment) or monitoring wells when contaminant concentrations in deep sediments or groundwater are of interest. 

Battelle has used PEDs for several projects for the U.S. Environmental Protection Agency (EPA), U.S. Army Corps of Engineers (USACE) and the U.S. Navy. In one USACE project at New Bedford Harbor, PEDs were used to analyze the flux of contamination across the sediment-water interface. The study results were used to help identify sources of contamination to the water column and food web, and to support remedial design. As part of a comprehensive evaluation of the effectiveness of dredging as a potential remedy, Battelle deployed passive samplers at a number of Great Lakes Legacy Act sediment sites for the EPA.

Outcome

Because PEDs concentrate the contaminants, they allow lower detection limits than traditional analytical methods for analysis of porewater, surface water and groundwater. They also provide an estimate of average concentrations over time rather than a single snapshot at the time of collection, which makes the results more reliable for long-term site monitoring. Because their uptake of contaminants is similar to bioaccumulation of contaminants by organisms, they can provide insight into the risks to local aquatic communities. Development of remediation goals based on freely dissolved concentrations, such as those obtained from passive samplers, decreases the uncertainty associated with whole sediment-based contaminant availability predictions. 

Battelle’s work has resulted in the development of optimized methods for use of PEDs for assessing and managing contaminated sediments. Battelle has also exposed PEDs to contaminated sediments in the laboratory and found that the porewater concentrations were equivalent to those measured in the field. Laboratory exposures offer an alternative to field deployments in high boat-traffic areas or areas easily accessible by foot where sampler loss during deployment may be an issue. Additionally, laboratory exposures can be conducted in less time and avoid costly field retrieval activities.

Battelle offers comprehensive list of passive sampling services, including preparation of the samplers, choice of performance reference compounds, deployment and retrieval in a wide variety of environmental settings, laboratory exposure studies, sampler extraction and analysis, and finally data processing and interpretation. Battelle has been a leader in passive sampler development for over 20 years and will work with you to design a study that meets your project’s needs.