Chemicals Studied: This study will examine concentrations of elemental and reactive (Hg(0) and Hg(II)) mercury in the gaseous and particulate phases of the atmosphere and in precipitation samples. Analysis for additional items, including particulate matter, trace elements, sulfur and nitrogen species, will allow for more thorough analysis of sources and atmospheric processes.

Geographic Areas: A series of six monitoring sites are being maintained throughout Michigan, offering considerable coverage of the Great Lakes region as a whole. The monitoring stations are at Eagle Harbor, Pellston, South Haven, Flint, Dexter and Detroit. In all, this series of monitors offers coverage of both urban and rural sites and has at least one monitor within several miles of four of the five Great Lakes.

Project Duration: Monitoring began at these locations in 2001. This project is supporting an additional two years of monitoring, which will provide data through the end of 2005. In all, these five years of monitoring data will provide a time-trend of atmospheric mercury that is unprecedented for the Great Lakes.

Methods Used: Precipitation event samples will be collected at each site by an automated sampling system at all sites. These wet deposition samples will be analyzed for mercury and trace element concentrations. Additionally, speciated ambient mercury measurements will be taken at two sites to assess elemental and reactive mercury in the gaseous and particulate phases. This ambient data will be used to estimate rates of dry deposition. In addition, the mercury and trace element data will be used to apportion mercury contributions to major source categories using statistical models, such as Positive Matrix Factorization and UNMIX.

Potential Results and Implications: This study will produce a collection of mercury data that is unprecedented in the Great Lakes region and will assist in answering a range of questions concerning the sources and processes leading to contamination of the region’s waters. Among the information that will be produced is temporal and spatial trends of mercury concentrations across the region; the speciation pattern of atmospheric mercury; the relationship between urban and rural sites; and the relative contributions of source types and regions. In all, this will provide a much clearer picture of the processes leading to contamination of the Great Lakes and inland lakes across the region.

Project Contact:
Gerald J. Keeler, Ph.D.
Air Quality Laboratory
University of Michigan
109 South Observatory St.
Ann Arbor, MI 48109-2029
Email: jkeeler@umich.edu