Contaminated sediments are a significant environmental problem that impacts the use and enjoyment of waterbodies worldwide and contribute to the 3,200 fish consumption advisories issued annually in the US (USEPA). Hydrophobic organic compounds such as polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and pesticides in sediment pose particular problems because they bioaccumulate in aquatic food webs, presenting risks to wildlife and humans that consume fish.
Why Passive Sampling for Sediments is Needed
Understanding the chemistry of hydrophobic compounds in sediment has challenged environmental decision makers for decades, especially identifying contaminated sediments and selecting appropriate management options. Sediment investigation and remedial assessments involve quantifying the availability of the compounds, which relates directly to risks. Direct testing of bulk sediment samples using exhaustive extraction techniques greatly overestimates availability and risk, as the adsorbed contaminants are also quantified. An alternative to extraction methods is mechanically collected porewater samples using probes. Mechanically derived samples are difficult to obtain and are often compromised by surface water and like extraction methods also greatly overestimate contaminant availability and risk.
“SERDP/ESTCP and USEPA have been champions of this powerful technology, so it’s great that they recognize SiREM’s pioneering work.”
Dr. Jason Conder
The use of passive sampling techniques to quantify availability is a solution to the challenges of traditional sediment sampling methods. Passive sampling involves exposure of an inert, sorptive solid media to sediment, followed by the analysis of the chemicals absorbed by the sampler. Through known partition coefficients, the data are converted to a concentration of “freely dissolved” compounds in porewater. Because the sampler is a mild absorbent, like an organism, passive sampling results correlate well with bioavailability and risk. This enables robust site assessments, cleanup goal derivation and remedial treatment evaluations. The use of passive sampling methods avoids the overestimation of availability by traditional methods and allows more precise decision making that is not encumbered with overly conservative assumptions.
Unique features of the SP3™ Approach
To meet the increasing need for passive samplers, SiREM developed the SP3™ sampler and data interpretation service. The sampler can be mounted on a variety of support options facilitating easily placement into sediment. After absorbing contaminants, the sampler is removed and sent to the lab for the specified analysis (e.g., PCB congener