Actively Shaken In Situ Passive Sampler Platform for Methylmercury and Organics

Abstract

Prototype of a periodically vibrated device used to deploy passive samplers in sediments.Accurate bioavailability measurements are needed for improved site risk assessments, proper selection of remedy, and post-remediation monitoring. While freely dissolved porewater concentrations of organic chemicals of concern and aqueous concentrations of bioavailable forms of trace metals in sediments have been demonstrated to be the ideal metrics for assessing bioavailability, accurate measurements of the low environmentally relevant concentrations have been a challenge. Passive sampling for sediment porewater has emerged as a very promising approach, but in situ measurements are complicated by slow mass transfer of strongly hydrophobic compounds. For methylmercury (MeHg), development of passive samplers has been hindered by the lack of an approach that adequately predicts porewater concentrations in complex milieu. This project was conducted in two phases. Phase I efforts successfully demonstrated the feasibility of using periodic vibration to enhance mass transfer and accuracy of measurement of strongly hydrophobic compounds and also demonstrated the feasibility of an equilibrium passive sampling approach for MeHg. The results of Phase I studies can be found in the Final Report. During Phase II, this research focused on advancing passive sampling on two major fronts: 1) use of mathematical modeling and device development to enable short-term passive sampling for hydrophobic pollutants, and 2) development of an equilibrium passive sampler for methylmercury in water and sediment porewater. The proof-of-concept developments in the Phase I project were successfully advanced with further testing and field deployments, paving the way for the extension of passive sampling to these heretofore difficult to measure analytes/conditions.