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Great Lakes Air Deposition Program Sponsored Projects
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Project Title: Monitoring Atmospheric Mercury Species in the Great Lakes
Synopsis: Since 1988, the Michigan Department of Community Health has issued
a state-wide fish consumption advisory for Hg for all of Michigan’s inland
lakes, for certain species of fish in three of the Great Lakes and Lake St. Clair.
Many other states in the Great Lakes region have similar advisories. The atmosphere
has been determined to be the most significant source of Hg to most of the region’s
inland lakes and to the Great Lakes. Mercury has been and is currently being
targeted as a pollutant of concern for source identification, reduction and/or
elimination through a variety of state, federal and international efforts. However,
significant information gaps exist that prevent effective management decisions
concerning this important contaminant. In particular, temporal and spatial trends
across the Great Lakes are not thoroughly established, assessment of dry deposition
is lacking, and the speciation of mercury among its various forms has not been
well studied in the Great Lakes region. This project is filling these important
knowledge gaps through monitoring the spatial and temporal trends in speciated
atmospheric Hg in both rural and urban areas in the Great Lakes.
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
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