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Jim Letourneau's Blog

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The Big Picture on Mississippi Nitrate Levels

The USGS just released the results of a comprehensive study on nitrates in the Mississippi watershed. No Consistent Declines in Nitrate Levels in Large Rivers in the Mississippi River Basin

The largest anthropogenic sources of nitrates are septic tanks, application of nitrogen-rich fertilizers to turfgrass, and agricultural processes. (source)

The study determined that nitrate levels at Clinton, Iowa, increased 76% from 1980-2008. While Iowa corn has been a major source of US ethanol supply, it comes at a cost.

As in most of the U.S., surface water in Iowa is never safe to drink untreated, contamination by agricultural runoff including nitrates, herbicides, pesticides, and animal waste is common. (source)

The bottom line is that nitrate transport to the Gulf of Mexico was 10% higher in 2008 than 1980 in spite of a few localized decreases due to conservation practises. The Mississippi River flows into the Gulf of Mexico at New Orleans. High nutrient levels (like nitrate) from the Mississippi contribute to hypoxia, or dead zones, in the Gulf of Mexico.

State and federal partners serving on the Mississippi River Gulf of Mexico Watershed Nutrient Task Force are striving to decrease nutrients transported to the Gulf to reduce the size of the hypoxic zone to less than 5,000 square kilometers (about 2,000 square miles) by 2015. This is roughly the size of Grand Canyon National Park!

When someone starts gesticulating about groundwater problems caused by shale gas wells, or the Gulf of Mexico being destroyed by BP, don't forget to remind them of the Big Picture on Mississippi Nitrate Levels.