Citation:

Baldwin, A., S. Corsi, D. Alvarez, D. Villeneuve, G. Ankley, B. Blackwell, M. Mills, P. Lenaker, AND M. Nott. Potential Hazards of Polycyclic Aromatic Hydrocarbons in Great Lakes Tributaries Using Water Column and Porewater Passive Samplers and Sediment Equilibrium Partitioning. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY. Society of Environmental Toxicology and Chemistry, Pensacola, FL, 43(7):1509-1523, (2024). https://doi.org/10.1002/etc.5896

Impact/Purpose:

Evaluation of risks that sediment contaminants pose to benthic organisms based on chemical monitoring data has often employed equilibrium partitioning to estimate the bioavailable concentration. However, because many environmental variable can strongly influence partitioning, the estimated variability can often be inaccurate leading to potential over- or under-estimation of risk. The current study employed an empirically-based alternative to equilibrium partitioning.  Rather than measure chemical concentration in bulk sediment, polyethylene passive sampling devices were embedded into the sediment. Bioavailable chemical found in the sediment pore-water is able to partition into the passive sampling device, providing an estimated bioavailable concentration that accounts for site specific environmental influences on bioavailability and partitioning behavior. The current manuscript compares bioavailable concentration estimates from both approaches with available toxicity and bioactivity-based effect concentration to identify specific sites and contaminants for which additional investigation is warranted. These results contribute directly to objectives outlined under Focus area 1.3 of the Great Lakes Restoration Initiative. Additionally, these methods can be employed by EPA Regions, States, and Tribes charged with estimating risks to aquatic ecosystems and benthos.  

Description:

The potential for polycyclic aromatic hydrocarbon (PAH)-related effects in benthic organisms is commonly estimated from organic carbon-normalized sediment concentrations based on equilibrium partitioning (EqP). Although this approach is useful for screening purposes, it may overestimate PAH bioavailability by orders of magnitude in some sediments, leading to inflated exposure estimates and potentially unnecessary remediation costs. Recently, passive samplers have been shown to provide an accurate assessment of the freely dissolved concentrations of PAHs, and thus their bioavailability and possible biological effects, in sediment porewater and overlying surface water. We used polyethylene passive sampling devices (PEDs) to measure freely dissolved porewater and water column PAH concentrations at 55 Great Lakes (USA/Canada) tributary locations. The potential for PAH-related biological effects using PED concentrations were estimated with multiple approaches by applying EqP, water quality guidelines, and pathway-based biological activity based on in vitro bioassay results from ToxCast. Results based on the PED-based exposure estimates were compared with EqP-derived exposure estimates for concurrently collected sediment samples. The results indicate a potential overestimation of bioavailable PAH concentrations by up to 960-fold using the EqP-based method compared with measurements using PEDs. Even so, PED-based exposure estimates indicate a high potential for PAH-related biological effects at 14 locations. Our findings provide an updated, weight-of-evidence–based site prioritization to help guide possible future monitoring and mitigation efforts.

URLs/Downloads:

Record Details: