Thursday, August 8, 2013

New groundwater study shows increases in some pollutants

Winter salt use contributes to water pollution.

One of the roles of the MPCA is to assess the condition of Minnesota’s groundwater. Clean groundwater is vital to the state of Minnesota. Groundwater supplies drinking water to about 75 percent of all Minnesotans and almost all of the water used to irrigate the state’s crops. The inflow of groundwater also is important to Minnesota’s streams, lakes and wetlands.

In a
new groundwater report, MPCA primarily looked at monitoring data from 2007-2011 that included traditional pollutants known to adversely affect groundwater such as nitrate, chloride and volatile organic compounds (VOCs or chemicals that participate in forming ozone). The report also included some newly-recognized pollutants, such as medicines, insect repellents, and fire retardants. The effects of these new pollutants, which are often referred to as contaminants of emerging concern or CECs, onto human and aquatic life are not fully understood at this point. 

Highlights from “The Condition of Minnesota’s Groundwater, 2007-2011” include:
  • Shallow groundwater in the Twin Cities Metropolitan Area (TCMA) is impacted by high chloride concentrations [road and sidewalk salt] with 27 percent of the TCMA monitoring wells in the sand and gravel aquifers having concentrations that were greater than drinking water guidelines set by EPA.
  • If chloride continues to increase in the groundwater, additional waters will likely violate drinking water and water-quality standards in the future.
  • Nitrate contamination generally has not changed over the last 15 years; however concentrations remain high in certain parts of the state.
  • The highest nitrate concentrations occurred in the aquifers in Central and Southwestern Minnesota.
  • CECs were detected in about one-third of the sampled wells in 2010. The most-frequently detected chemicals were the fire retardant tris phosphate, the antibiotic sulfamethoxazole, and bisphenol A and tributyl phosphate. No concentrations violated any applicable human-health guidance set by the state of Minnesota.
Monitoring is ongoing with additional wells being installed to increase the breadth of the monitoring network. This work will serve the state well into the future by detecting contamination problems that occur along with developing and tracking groundwater quality trends. To view the executive summary and full report on the condition of Minnesota’s groundwater, visit the MPCA’s
Groundwater in Minnesota webpage.

This article reprinted from the Minnesota Pollution Control Agency's Waterfront Bulletin with permission.


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