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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 cooperation with the Indiana Department of Environmental Management (IDEM) has operated statewide monitoring networks for assessing mercury concentrations and loads in streams since 2002, and mercury concentrations and deposition from precipitation since 2001. In addition, IDEM has maintained annual fish sampling for mercury since 1993 in support of health-risk-fish-consumption advisories. |
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Mercury in precipitation has been monitored by USGS in cooperation with IDEM since 2001. Weekly composite samples are collected from five stations across Indiana. The monitoring stations are part of the National Atmospheric Deposition Program Mercury Deposition Network, that operated 100 monitoring stations in North America in 2007. |
Atmospheric mercury species were measured with a manual air sampling system at three stations in Indiana in 2004. Samples were analyzed in a laboratory and concentrations were used to estimate mercury dry deposition. |
Mercury in streams in Indiana has been monitored by the USGS since 2004, following a program by IDEM from 2002 to 2004. The monitoring network includes 25 stations at USGS streamgages and samples are collected on a quarterly schedule. The monitoring stations include streams with watersheds representing 80 percent of the land area in the State, and range in size from 59 square miles to 13,756 square miles. |
Low-level mercury sample collection, sample processing, and analysis are done using ultra-clean methods to avoid introducing unintended contaminants into samples. Analytical methods quantify mercury concentrations as small as 0.05 nanograms per liter (parts per trillion). |
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Mercury in Precipitation in Indiana |
Mercury in Indiana Streams |
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Atmospheric Mercury in Indiana |
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Mercury monitoring in cooperation with |
Mercury in precipitation monitoring is part
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Go to the USGS Indiana Water Science Center
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