SOUTH BEND, Ind., Dec. 27 (UPI) -- The world's rivers put the greenhouse gas nitrous oxide into the atmosphere at three times the rate previously estimated, a report by U.S. researchers says.
A study by researchers from Notre Dame University and the U.S. Environmental Protection Agency found human-caused nitrogen loading of river networks through fertilizer runoff is a potentially significant source of nitrous oxide emissions to the atmosphere, ScienceDaily.com reported Monday.
Nitrous oxide is one of the greenhouse gases that contribute to climate change and stratospheric ozone destruction.
"Human activities, including fossil fuel combustion and intensive agriculture, have increased the availability of nitrogen in the environment," Jake Beaulieu of Notre Dame and lead author of the study says. "Much of this nitrogen is transported into river and stream networks where it may be converted to nitrous oxide, a potent greenhouse gas, via the activity of microbes."
Beaulieu and colleagues measured nitrous oxide production rates in 72 streams draining multiple land-use types across the United States.
"This multi-site experiment clearly establishes streams and rivers as important sources of nitrous oxide," says Henry Gholz, program director of the National Science Foundation's Division of Environmental Biology, which funded the research. "This is especially the case for those draining nitrogen-enriched urbanized and agricultural watersheds, highlighting the importance of managing nitrogen before it reaches open water.
"This new global emission estimate is startling."