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Mercury in Indiana's Waterways

Indiana Precipitation Cleaner, but Streams Deteriorated
 
While mercury is an infrequent contaminant in drinking water, private well owners are responsible for testing their own water. The latest news from Indiana is a reminder that new concerns continually emerge and owners need to periodically examine samples for contamination.
 
Rain and snow falling in Indiana contains less mercury than it did in years past, yet some of the state's major waterways currently have mercury levels that could be harmful to humans and wildlife.  Since groundwater is part of the hydrologic cycle, contaminants in other parts of the cycle, such as mercury in the atmosphere or bodies of surface water, can eventually be transferred into groundwater supplies.
 
According to a U.S. Geological Survey report, six percent of water samples collected from 2004 to 2006 had mercury levels that exceeded the Indiana water-quality standard protecting human health.  Mercury concentrations in 73 percent of the samples exceeded the more restrictive state water-quality standard protecting wildlife.  Over 80 percent of the water samples had detectable methyl-mercury, the most toxic form.
 
"The highest mercury concentrations we measured were downstream of urban and industrial discharges or, in one case, downstream from active and abandoned minelands," said USGS scientist Amanda Ulberg. Mercury in streams comes from atmospheric deposition and discharges of municipal and industrial wastewater.
 
In a separate USGS report, scientists found that mercury concentrations in over 40 percent of the precipitation samples exceeded the Indiana water-quality standard for human health and nearly all concentrations exceeded the standard protecting wildlife.  However, there was a three percent decrease in mercury concentrations in precipitation and an eight percent decrease in the mass of mercury deposited by precipitation at the five Indiana monitoring stations from 2001 to 2005. These decreases may be related to a substantial decrease from 2002 to 2005 in mercury emissions in Indiana. Mercury in the atmosphere comes from human activities that include coal-fueled power generation, metals industries, and cement manufacturing.  
 
SE Indiana among Worst for Deposits of Mercury
 
"Our studies are showing that mercury can be found in the water everywhere we've looked in Indiana, but the mercury varies from place to place and changes both seasonally and year to year," said USGS scientist Martin Risch. By using a new mapping technique, an area in southeastern Indiana was identified where high mercury concentrations in the rain had contributed to some of the highest mercury deposition in the U.S.  The likely reason is the high annual mercury emissions in that particular area.
 
Exposure to very high levels of mercury in drinking water is unlikely, but if mercury is detected, there are water treatment options. The US EPA has identified the Best Available Technologies (BATs) that are capable of removing regulated contaminants from drinking water. The BATs for removing inorganic mercury are distillation and reverse osmosis.  For organic mercury, the BAT is filtration through granulated activated carbon (GAC).

By Michelle Simmons
Get Water Treatment Jobs, Contributing Editor

Source: www.usgs.gov.

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