by Martin Risch December 2006
Mercury in aquatic ecosystems is a public health and environmental concern. Mercury—especially in its organic form, methylmercury—can affect the central nervous system of adults and children. The primary route of human exposure to methylmercury is dietary, and children are more susceptible than adults to methylmercury’s detrimental effects (National Research Council, 2000).
Fish living in aquatic ecosystems with extremely low concentrations of inorganic mercury are known to accumulate substantial amounts of methylmercury in their tissue (Krabbenhoft and Rickert, 1995). Mercury has been detected in nearly all fish tissue samples collected in Indiana since 1983 (Stahl, 1997). Concentrations of mercury in some fish caught from Indiana waters have prompted health officials to issue advisories that warn about human consumption of these fish (Indiana State Department of Health and others, 2000 through 2005).
In addition, adults and embryos of fish-eating wildlife can suffer damage to the central nervous system from mercury contamination (Krabbenhoft and Weiner, 1999). Figure 1 illustrates how small amounts of mercury increase through the food chain.
Precipitation is a primary mechanism for transporting airborne gaseous or particulate mercury from theatmospheretosurfacewaterandland(U.S.EnvironmentalProtectionAgency,1997).Mercury in the atmosphere can be from human activities (electric-power generation, waste incinerators, steel mills) or from natural processes (forest fires, volcanoes). Mercury emissions to the atmosphere from human activities have been implicated for causing the increased concentrations of methylmercury found in fish (U.S. Environmental Protection Agency, 1997). The connection between mercury in fish and mercury in precipitation is illustrated in figure 2.Mercury has been detected in precipitation at monitoring stations throughout North America (National Atmospheric Deposition Program, 2006). Often, mercury concentrations in precipitation exceed the national fresh-water toxic pollutant standard of 0.012 micrograms per liter (U.S.EnvironmentalProtectionAgency,1999).Until the monitoring program for mercury in precipitation was implemented, limited information was available about the atmospheric deposition of mercury to Indiana’s aquatic ecosystems.
The U.S. Geological Survey (USGS), in cooperation with the Indiana Department of Environmental Management (IDEM), operates the monitoring program for mercury in precipitation in Indiana. The project has been funded by USGS and IDEM’s Office of Air Quality and Office of Water Quality. The monitoring program is coordinated through the IDEM Mercury Work Group and is one of several initiatives to measure and reduce mercury in Indiana’s environment. The USGS has joined with the U.S. Environmental Protection Agency (USEPA) to promote and communicate mercury research for application to national policy decisions (U.S. Environmental Protection Agency, 2000). The USEPA, USGS, and IDEM also have collaborated to monitor mercury as it affects the Great Lakes and surface water in Indiana.
The monitoring measures
Information from monitoring mercury in precipitation in Indiana can indicate:
•the distribution of mercury in precipitation within the state related to mercury emission sources such as electric-power generation, steel mills and foundries, or cement and gypsum manufacturing (2002 Regional Air Pollutant Inventory System for Indiana, 2004, Office of Planning and Assessment, Indiana Department of Environmental Man-agement, unpublished data);
Monitoring stations in Indiana (fig. 3) are being operated as part of the Mercury Deposition Network (MDN) in North America, coordinated by the National Atmospheric Deposition Program (NADP). The NADP is an organization of federal agencies (including the USGS), state agencies, academic institutions, tribal governments, private organizations, and the environmental agencies from Canada and Mexico. For more than 25 years, NADP has provided consistent, accurate, quality-assured atmospheric-deposition data about acid rain to researchers, policymakers and the general public. The MDN started in 1996 and, as of late 2005, had nearly 100 stations (fig. 4).
In 2001, four monitoring stations for mercury in precipitation were strategically located in the state (fig.3), based on potential mercury sources and weather patterns. A fifth station (in Marion County) was added in 2003. The locations, with the MDN identifications (north to south), were selected by IDEM and the rationale for their selection follow.
A monitoring station has an automated precipitation collector and a recording rain gage (fig. 5). The collector has internal temperature controls and operates year round. It has a sensor and motor that open and close a retractable lid for each rainfall or snowfall. Precipitation that is rain or melted snow and ice accumulates in a sample bottle previously fortified with a preservative for mercury. The precipitation amount and collector openings/closings are recorded by the rain gage. The glass sampling supplies (funnel, tube, and bottle) are pre-cleaned and quality assured. The sampling supplies are exchanged weekly on the same day at every MDN station in North America. A weekly sample may be from a single precipitation event or it may be a composite of two or more events in a week.
Weekly samples from the Indiana monitoring stations—because they are part of a national network—are analyzed by one MDN laboratory to maintain consistency and comparability of results. The lab also prepares the sampling supplies. All samples are analyzed for total recoverable mercury by a low-level method capable of quantifying concentrations as small as 0.1 nanogram per liter (generally equivalent to 0.0001 microgram per liter or one-tenth part per trillion). In Indiana during 2001 through 2003, samples also were analyzed for methylmercury. Methylmercury was analyzed because it is the form of mercury that accumulates in the food chain.
In 2002, at Roush Lake, Bloomington, and Clifty Falls, a second weekly precipitation sample was collected for analysis of seven trace metals, including those classified as hazardous air pollutants (arsenic, beryllium, cadmium, chromium, lead, manganese, and zinc.). In 2004, at the Roush Lake, Forth Harrison, and Clifty Falls stations, a second automated collector obtained a weekly air sample that was analyzed for reactive gaseous, particulate-bound, and elemental mercury. Concentrations of mercury in air and meteorological data were recorded at the monitoring stations for use in estimating mercury dry deposition. These additional dry deposition data make it possible to estimate the total mercury load from atmospheric sources at these monitoring stations as the sum of wet and dry deposition.
Data summaries for Indiana are posted on the USGS website for Indiana http://in.water.usgs.gov/newreports/mercury/DataSummaryDec2006.shtml. The NADP archives the monitoring data from the entire MDN at http://nadp.sws.uiuc.edu/mdn.
The IDEM Office of Air Quality uses the monitoring data
The IDEM Office of Water Quality uses the monitoring data
The IDEM Office of Planning and Assessment uses the data:
The USGS, USEPA, and IDEM Mercury Work Group intends to use the data to understand mercury cycling in the environment—to determine relationships among air emissions, atmospheric deposition, concentrations in aquatic ecosystems, levels in fish tissue, and associated risks to human health and wildlife. The NADP data archive for the MDN includes Indiana data for comparisons among states, as the basis for national summaries, and in evaluations of large-scale models for atmospheric transport and deposition of mercury.
Indiana State Department of Health, Indiana Department of Environmental Management, Indiana Department of Natural Resources, 2000, 2001, 2002, 2003, 2004, 2005 (separate publications in consecutive years), Indiana fish consumption advisory: Indiana State Department of Health, Environmental Epidemiology Resource Center.
Krabbenhoft, D.P., and Rickert, D.A., 1995, Mercury contamination of aquatic ecosystems: U.S. Geological Survey Fact Sheet FS-216-95.
Krabbenhoft, D.P., and Weiner, J.G., 1999, Mercury contamination: A nationwide threat to our aquatic resources, and a proposed research agenda for the U.S. Geological Survey, in Morganwalp, D.W., and Buxton, H.T., eds., U.S. Geological Survey Toxic Substances Hydrology Program—Proceedings of the technical meeting, Charleston, S.C., March 8-12, 1999: U.S. Geological Survey Water Resources Investigation Report 99-4018B.
National Research Council, 2000, Toxicological effects of methylmercury: Washington, D.C., National Academy Press, Committee on the Toxicological Effects of Methylmercury, Board of Environmental Studies and Toxicology, 368 p.
Stahl, J.R., 1997, A preliminary appraisal of the biological integrity of Indiana streams in the West Fork White River watershed using fish tissue contamination assessment: Indiana Department of Environmental Management, Office of Water Management, Assessment Branch, Biological Studies Section, Indianapolis, Ind., IDEM/32/03/005/ 1997.
National Atmospheric Deposition Program, 2006, National Atmospheric Deposition Program 2005 annual summary: NADP Data Report 2006-01, Illinois State Water Survey, Champaign, Illinois, 16 p.
National Wildlife Federation, 2000, Clean the rain, clean the lakes: Internet URL http://www.nwf.org
U.S. Environmental Protection Agency, 1997, Mercury study report to Congress—Overview: Office of Air Quality
Planning and Standards and Office of Research and Development,
EPA452/R-97-001.
____ 1999, Mercury update—Impact on fish
advisories: Office of Water, Fact Sheet EPA-823-F-99-016.
____ 2000,
Mercury research strategy: Office of Research and Development,
EPA/600/R-00/073.
Martin Risch,
Project Chief U.S. Geological Survey 5957 Lakeside Boulevard Indianapolis, IN 46278 317-290-3333, ext. 163 mrrisch@usgs.gov http://in.water.usgs.gov |
or | Kathryn
Watson, Chief, Air Programs Branch Indiana Department of Environmental Management 100 Senate Avenue Indianapolis, Indiana 46206-2251 (toll free) 800-451-6027 http://www.in.gov/idem/programs/air/workgroups/mercury/index.html |
This web page is also available in PDF format: Monitoring Program for Mercury in Precipitation in Indiana
Data available from this project: