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Photo from U.S. Geological Circular 1225--The Quality of Our Nation's Waters--Nutrients and Pesticides

Photo of the Potomac River at Washington D.C.

(Photo by James M. Gerhart)

Major events affecting streams used for drinking-water purposes may require intensified monitoring during peak fertilizer- and pesticide-application periods. As an example, the Potomac River at Washington, D.C., carried an estimated 3,300 pounds of the herbicide atrazine and 3.3 million pounds of nitrogen in 5 days during a flood in June 1996. On two consecutive days following the storm, atrazine was measured at concentrations greater than the drinking-water standard of 3 micrograms per liter.

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