September 25th, 2008 · No Comments

By John DeFore

Nitrates, substances which when consumed by humans can be toxic, especially for infants (whose blood can be made less able to carry enough oxygen), are commonly used in fertilizers. While efforts have been made in recent years to reduce fertilizer use, it’s hard to know — since it takes time for substances to migrate from topsoil into aquifers — how quickly changes to agricultural practices affect water supplies.

Now a study published in the Journal of Environmental Quality finds that nitrate levels in ground water are on the rise in many parts of the U.S., leading researchers to call for increased monitoring.

The study was conducted by the U.S. Geological Survey and took place over a span of 16 years. In that period, samples were taken at almost 500 individual wells spread across 24 “well networks,” mainly in agricultural areas. Of those networks, almost a third showed nitrate increases during the period, and three of the 24 well networks studied “increased above the US EPA maximum contaminant level of 10 parts per million.” (Levels decreased significantly in only one of the networks, located in Oregon’s Willamette Valley.)

As U.S. Geology Survey hydrologist Michael Rupert put it in a statement, “This study highlights the importance of maintaining long-term ground-water monitoring programs in the nation, because sustained monitoring provides critical information on changes of our nation’s ground-water quality, and whether pollution prevention programs are effective in protecting this nation’s ground water.”

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