ST. LOUIS, MO (ST. LOUIS PUBLIC RADIO) - A new study shows that despite decades of effort to reduce nitrate pollution in the Mississippi River Basin, concentrations remain as high today as they were in the 1980s.
The U.S. Geological Survey conducted the study, which looked at nitrate levels at eight sites on the Mississippi, Iowa, Illinois, Missouri, and Ohio rivers.
USGS hydrologist and study lead Lori Sprague said the next step will be to figure out where the pollution is coming from.
"The largest sources of nitrates are fertilizer, livestock, wastewater treatment plants, and industrial emissions," Sprague said. "We can't say for sure which of those are causing the trends that we're seeing and in fact it's probably some combination of all of them."
Nitrates flowing from the Mississippi River into the Gulf of Mexico contribute to the formation of areas known as dead zones, where there is too little oxygen in the water to support marine life.
Véronique LaCapra, St. Louis Public Radio
Image: A map showing each of the sites involved in the U.S. Geological Survey's study on nitrate pollution in the Mississippi River Basin.
(Courtesy U.S. Geological Survey)