Predoctoral Fellow 2014-2015, Institute for Environmental Science and Policy
Controls on the Accumulation and Transformation of Semi-Volatile Halogenated Persistent Bioaccumulative Toxic Compounds in the Upper Great Lakes
The Laurentian Great Lakes are a collection of five of the largest lakes in the world (Lakes Superior, Michigan, Huron, Erie and Ontario from west to east). The lakes are by far the largest freshwater ecosystem on earth; comprising over one-fifth of the world’s surface freshwater. The Great Lakes are also important economically as a major source of drinking water, food, recreation, employment, and transportation to more than 35 million people (one-third of the Canadian population and one-tenth of the U.S. population)1.The very large surface area to volume ratio of the Great Lakes (nearly two orders of magnitude higher than that of the oceans) makes them particularly sensitive to airborne pollution2,3 because water outflows from the Great Lakes are relatively small compared to the total volume (<1% peryear), persistent pollutants (those that do not degrade) that enter the lakes tend to accumulate in the system. Sediment often acts as the final reservoir for hydrophobic contaminants, particularly for the class of compounds designated by the USEPA as persistent, bioaccumulative toxic compounds (PBTs). PBT-contaminated sediments are a significant problem in the Great Lakes basin, created by decades of industrial and municipal discharges, combined sewer overflows, and urban and agricultural non-point source runoff. Although direct water-phase discharges to the Great Lakes have been greatly diminished over the last few decades, volatile and semi-volatile PBTs (SV-PBTs) also reach the lakes through air transport and deposition onto the water surface, with subsequent sedimentation to the bottom. Progress over the past few decades has substantially reduced discharges of PBTs to the Great Lakes (particularly water-phase). However, past deposition of persistent contaminants has resulted in high levels of the contaminants in the lake sediments, raising concerns about exposure to aquatic organisms, wildlife, and humans as the sediments change from a contaminant sink to a contaminant source. Release and uptake of compounds such as polychlorinated biphenyls (PCBs) from contaminated sediments has been implicated in the development of cancerous tumors, loss of suitable habitat and toxicity, fish consumption advisories, closed commercial fisheries, and restrictions on navigational dredging4-6.
The overall aim of my research is to better understand controls on the sources and fate of persistent bioaccumulative toxic compounds (PBTs) in the Laurentian Great Lakes. The research proposed here grew out of my participation in the Great Lakes Sediment Surveillance Program (GLSSP) funded by the U.S. Environmental Protection Agency (USEPA).
My exploratory research goal is to better understand processes affecting both sources and fate of PBTs in the Great Lakes sediment. This aim will be achieved through the completion of two research objectives; the first focusing on PBT sources and transport to/from Great Lakes sediment, and the second focusing on in situ PBT fate.
Research Objective 1: The first objective of my research is to quantify PBT fluxes to/from sediments through the analysis of depositional histories and in-situ mass transport modeling.
Research Objective 2: The second objective is to better understand the potential for in situ degradation of PBT compounds in sediments of the Great Lakes through the analysis of reconstructed microbial community structures from PBT-contaminated sediments.
- GLRC (Great Lakes Regional Collaboration). (2010). Great Lakes mercury emission reduction strategy.
30 June 2011. http://www.glrc.us/initiatives/toxics/index.html.
- Charette, M., et al. (2010). Oceanogr. 23(2):112-114.
- Quinn, F., et al. (1992) J. Great Lakes Res. 18(1): 22-28.
- Gomes, H., et al. (2013). Sci. Total Environ. 237–260.
- Murínová, S., et al. (2014). Int. Biodeterioration & Biodegr. 91: 52-59.
- Ahlborg, U.G., et al. (1994). Chemosphere. 28(6):1049–1067.