Jeff Roberts and Karen Bechard Presented at Laurentian SETAC Conference
Jeff Roberts (Ontario) and Karen Bechard (Ontario) presented at the Laurentian Society of Environmental Toxicology and Chemistry (SETAC) 21st Annual General Meeting & Conference entitled "Watershed Science Under Multiple Stressors" at the University of Waterloo in Ontario on June 24, 2016.
Jeff Roberts introduced the SP3 passive sampler in the presentation entitled "Passive sampling for measuring the availability of hydrophobic organic chemicals: The end-user perspective." Karen Bechard highlighted Geosyntec's knowledge of mercury remediation and the benefits of site-specific treatability studies in the presentation entitled "Sequestration of mercury and PCBs in sediments via amendments."
Passive sampling approaches are now recognized as one of the best tools to quantify the availability of organic compounds in sediment, surface water and soil. They provide data to estimate contaminant bioavailability and toxicity to environmental receptors that is more representative than conventional grab samples, as it quantifies contaminants only in the dissolved form. Despite dozens of publications detailing the development and application of passive sampling approaches over the last 15 years, recent enthusiastic regulatory support (e.g., USEPA’s 2012 passive sampling guidance), and a 6-paper series detailing a successful 2012 SETAC Pellston workshop on passive sampling, the majority of the end-user community (i.e., industrial and government organizations with environmental responsibilities and consultants) continues to move slowly in applying this powerful technology.
This presentation will highlight the current real and perceived barriers to widespread application of passive sampling from an end-user’s point of view, as well as practical lessons learned from applying passive sampling techniques in the field. The use of passive samplers in laboratory treatability studies will be discussed and a case study presented where passive samplers were used to characterize PCB concentrations in sediment pore water amended with different amounts of activated carbon to determine the optimal dose of carbon for field application. We will discuss where the field of passive sampling needs to head in the next few years to maximize the adoption of passive sampling approaches. Despite the current challenges and research action items, it is clear that currently-available passive sampling approaches are ready for widespread application and can provide high-quality data to aid environmental decision makers.
Chemicals such as polychlorinated biphenyls (PCBs), and mercury (Hg) are present as contaminants in sediment at numerous sites globally. Amendments are sometimes used in conjunction with Monitored Natural Recovery (MNR) to accelerate chemical sorption, sequestration, or biodegradation processes, and to reduce bioavailability and toxicity. To gain regulatory acceptance for this Enhanced MNR (EMNR) method, the site-specific physical, biological and chemical processes that reduce bioavailability or degrade contaminants must be well understood, demonstrated, and quantified in laboratory treatability tests and in field pilot tests.
Laboratory treatability testing was conducted to demonstrate the potential for a variety of in situ amendments to reduce concentrations of Hg, methylmercury (MeHg) and PCBs in water mixed with sediment from a contaminated sediment site in a tidal estuary with brackish water under simulated anaerobic conditions over eight weeks. The concentrations of PCBs, Hg and MeHg in the aqueous phase were measured and the concentrations in the treated microcosms were compared with the concentrations in the controls. Results of the testing demonstrated that significant reductions in the concentration of PCBs, Hg and MeHg in water in contact with the sediment could be obtained with the specific amendments evaluated in the test. A combination of powdered activated carbon and iron amendments was successful in reducing the concentrations of PCBs in the simulated porewater by over 99% relative to controls and reducing Hg and MeHg by 89% and 82% relative to controls, respectively. Further testing is underway to further assess the bioavailability of Hg in post remediated sediments versus control sediments.
For more information regarding the event, please visit: SETAC Conference