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| INVESTIGATIONS AND MONITORING OF MERCURY IN INDIANA BY THE U.S. GEOLOGICAL SURVEY |
| Mercury is a persistent toxic pollutant that poses a risk to humans and wildlife, primarily through fish consumption. Small concentrations of inorganic mercury in precipitation, dry atmospheric deposition, and wastewater discharges that enter aquatic ecosystems can be converted to organic methylmercury. Methylmercury accumulates in the food chains of aquatic ecosystems and magnifies in concentration so that mammals (including humans) and birds at the top of the food chain can be exposed to methylmercury concentrations that pose a health risk. The primary health risks are to the brain and nervous systems, especially for the young and unborn. | Mercury has been detected in nearly all
fish-tissue samples collected in Indiana since 1983. Concentrations
of mercury in some tissue samples from fish caught in Indiana waters
have prompted State health officials to issue advisories that warn
about human consumption of these fish. These advisories apply
statewide to certain sizes and species of fish and include
additional warnings for specific streams and lakes.
As of 2006, mercury advisories affected 3,113 mi of streams, 40,628 acres of lakes, and 59 mi of Great Lakes shoreline in Indiana. Each year, some 833,000 resident anglers, 16 years and older, spend 15.5 million days and $469 million for fishing as recreation. An estimated 286,000 more resident anglers are 6 to 15 years old. Based on these numbers, fish-consumption advisories affect approximately 1 of 6 Indiana residents. |
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The Mercury Cycle in Aquatic Ecosystems |
| Methylmercury is produced from inorganic mercury by a microbial process that occurs under certain conditions in aquatic ecosystems. Fish living in aquatic ecosystems with low concentrations of inorganic mercury are known to accumulate methylmercury in their tissue. Concentrations of methylmercury can increase up the food chain so that higher-level organisms tend to accumulate the highest levels of methylmercury. | |
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Monitoring of Mercury in Indiana |
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The U.S. Geological Survey (USGS) in a partnership with the Indiana Department of Environmental Management (IDEM) operates two statewide monitoring networks for mercury in Indiana. One network measures mercury concentrations in precipitation to compute wet deposition of atmospheric mercury. The other network determines |
Mercury in Precipitation in Indiana |
Mercury in Indiana Streams |
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Mercury in precipitation has been monitored by USGS since 2001. Weekly precipitation samples are collected at five stations across Indiana, using an automated precipitation sampler. The precipitation amount is measured with a digital recording rain gage inside a wind shield. Samples are analyzed for total mercury with methods which quantify concentrations less than a part per trillion. These five monitoring stations are part of the National Atmospheric Deposition Program Mercury Deposition Network, which coordinated 110 monitoring stations in North America in 2008. |
Mercury in streams of Indiana has been monitored by the USGS since 2004. The monitoring network includes 25 stations in 2004-2006 (list, map) and in 2007-2009 (list, map) near USGS streamgages. The monitoring stations are located on streams with watersheds draining more than 80 percent of the land area in the state. Water and samples are collected on a seasonal schedule using ultra-clean methods. Sample processing is done in controlled laboratory conditions. Mercury is analyzed with methods which quantify concentrations less than a part per trillion. Streamflow data enable calculations of mercury loads transported in the streams. |
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| More Information
Mercury in precipitation monitoring is coordinated |
Investigations of Mercury in Indiana Measurement of Atmospheric Mercury Species with Manual Sampling and Analysis Methods in a Case Study in Indiana by Martin R. Risch, Eric M. Prestbo, and Lucas Hawkins An Alternate Method for Creating a Statewide Isopleth Map of Total Mercury Wet Deposition USGS Pilot Study of Mercury in Litterfall at National Atmospheric Deposition Program Mercury Deposition Network Sites, 2007--2008 by Martin Risch |
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Go to the USGS Indiana Water Science Center
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Monitoring of mercury in precipitation and streams in cooperation with the Indiana Department of Environmental Management
