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 contaminants 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 is being conducted in two phases. Phase I is complete and initial 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. In Phase II, key objectives are to 1) optimize the vibration frequency through mathematical modeling and laboratory experiments, 2) demonstrate passive sampling for PCBs, DDT, and dioxin/furan contaminated sediments, 3) field-test the vibrating passive sampling platform; 4) complete development of a passive sampling material that reliably predicts pore water MeHg concentrations in complex matrices, 5) develop enriched stable isotope MeHg spikes as performance reference compounds, 6) verify the predictive capability of MeHg samplers in natural sediments. The ultimate goal is to develop an in situ, actively shaken deployment platform that can accommodate multiple types of passive samplers (for organics and MeHg).
In Phase II, laboratory studies will be performed to operationalize a platform for the deployment of passive sampling devices. A key innovation in the design will be the incorporation of vibration devices to disrupt the aqueous boundary layer around the passive samplers to enhance mass transfer and provide accurate porewater measurements. The proof-of-concept demonstrated in Phase I will be made ready for field use through optimization of the vibration frequency, increasing the size of the devices to accommodate larger samplers, demonstration with PCB/DDT/dioxin/furan contaminated sediments, and field-testing. It is anticipated that the platform will be able to incorporate passive samplers for both hydrophobic organic contaminants such as dioxins, furans, DDT, and PCBs, as well as new samplers for MeHg.
For MeHg, the goal is the development of an equilibrium passive sampling approach, for which the Phase I study provided proof of concept. Sampler uptake kinetics and equilibrium partitioning for a variety of naturally occurring MeHg compounds will be evaluated, using enriched Hg stable isotope tracers to follow exchange among compounds and samplers. Polymer design will be further optimized to achieve rapid and reversible equilibrium with the aqueous MeHg pool. Critically, the idea that passive sampler measurement of “freely dissolved” MeHg can be used to predict total aqueous MeHg will be experimentally tested.
This research advances the field of bioavailability assessment by developing an improved approach for in situ measurement of bioavailable concentrations of pollutants in sediment porewater. The research addresses key bottlenecks for in situ measurements by enhancing mass transfer and by promoting the development of a passive equilibrium sampler for MeHg. (Anticipated Project Completion - 2021)
Jalalizadeh, M. and U. Ghosh. 2017. Analysis of Measurement Errors in Passive Sampling of Porewater PCB Concentrations under Static and Periodically Vibrated Conditions. Environmental Science and Technology, 51(12):7018-7027. doi.org/10.1021/acs.est.7b01020.
Jalalizadeh, M., U. Ghosh. 2016. In Situ Passive Sampling of Sediment Porewater Enhanced by Periodic Vibration. Environmental Science and Technology, 50(16):8741–8749. doi.org/10.1021/acs.est.6b00531.
Sanders, J.P., A. McBurney, C.C. Gilmour, G. Schwartz, S. Washburn, S.B. Kane Driscoll, S.S. Brown, and U. Ghosh. 2020. Development of a Novel Equilibrium Passive Sampling Device for Methylmercury in Sediment and Soil Porewaters. Environmental Toxicology and Chemistry, 39(2):323–334. doi.org/10.1002/etc.4631.
Washburn, S.J., J. Damond, J.P. Sanders, C.C. Gilmour, and U. Ghosh. 2022. Uptake Mechanisms of a Novel, Activated Carbon-Based Equilibrium Passive Sampler for Estimating Porewater Methylmercury. Environmental Toxicology and Chemistry, 41(9):2052-2064. doi.org/10.1002/etc.5406.
Ghosh, U. and M. Jalalizadeh. 2020. Actively Shaken In-Situ Passive Sampling Device. US Patent. Pub. No. US 2018/0088008A1.
Jada Damond. Second Place, Best Student Platform Presentation, SETAC Chesapeake Potomac Regional Chapter Annual Virtual Meeting, September 2020.
Jada Damond. Third Place, SETAC Chesapeake-Potomac and Hudson-Delaware Regional Chapter (CPRC-HDC) Joint Spring Meeting, April 2022.
Oindrila Ghosh. Third Place, Best Student Platform Presentation, SETAC Chesapeake Potomac Regional Chapter Annual Virtual Meeting, September 2020.
Oindrila Ghosh. Best Student Paper Award at the Battelle International Sediment Conference, January 2023.
Mehregan Jalalizadeh. First Place, Student Poster Award, SETAC Hudson Delaware Chapter Meeting, 2016.
Mehregan Jalalizadeh. Third Place, 8th Annual Geosyntec Student Paper Competition, 2017.
James Sanders. Most Popular Poster, Society of Environmental Toxicology and Chemistry, Chesapeake Potomac Regional Chapter, Virtual Poster Contest, 2016.
James Sanders. Best Student Poster Award, Society of Environmental Toxicology and Chemistry, Hudson Delaware Chapter meeting, April 2017.
James Sanders. Second Place, 8th Annual Geosyntec Student Paper Competition, 2017.
James Sanders. Best Student Paper Award from Society of Environmental Toxicology and Chemistry, 2020.
James Sanders. Top 10 Exceptional Papers of 2020 by the Journal of Environmental Toxicology and Chemistry.