MANHATTAN, KAN. -- A Kansas State University professor is part of a national research team that discovered that streams and rivers produce three times more greenhouse gas emissions than estimated by the Intergovernmental Panel on Climate Change.
Through his work on the Konza Prairie Biological Station and other local streams, Walter Dodds, university distinguished professor of biology, helped demonstrate that nitrous oxide emissions from rivers and streams make up at least 10 percent of human-caused nitrous oxide emissions -- three times greater than current estimates by the climate change panel.
"This research deals with two important issues," Dodds said. "First, nitrous oxide is a potent greenhouse gas. Second, nitrous oxide also destroys ozone in the upper atmosphere, exposing us to more ultra violet radiation."
The research, "Nitrous oxide emission from denitrification in stream and river networks," appears in this week's Online Early Edition of the Proceedings of the National Academy of Sciences.
For the article, researchers from 23 institutions -- including K-State -- measured nitrous oxide production in 72 streams that drain native, urban or agricultural lands. Nine of those streams were in the Manhattan area, with three at Konza.
The level of nitrous oxide in streams and rivers is related to human activities that can release nitrogen into the environment, such as sewage runoff or crop fertilization. When this nitrogen reaches rivers and streams, it undergoes denitrification, a microbial process that converts nitrogren to nitrous oxide gas, called N2O, and an inert gas called dinitrogen, or N2.
As a greenhouse gas, nitrous oxide has global warming potential that is 300-fold greater than carbon dioxide. In the past century, concentration of atmospheric nitrous oxide has increased 20 percent, making it a strong contributor to climate change and ozone destruction.
"We show that river networks play an important role in how human nitrogen additions for crops influence the global environment," Dodds said.
The findings can lead to more effective mitigation strategies, Dodds said. Researchers suggest that nitrous oxide emissions can be reduced from river networks by changing agricultural and urban land-use practices, such as better management practices for fertilizers. By decreasing nitrogen input to watersheds, the production of nitrous oxide also diminishes.
Jake Beaulieu of the Environmental Protection Agency is the lead author of the paper, produced as part of a project headed by Patrick Mulholland of the Oak Ridge National Laboratory. From 2005 to 2007 the team received $3 million from the National Science Foundation to investigate nitrogen pollution in streams. K-State received $320,000 of the grant.
Journal
Proceedings of the National Academy of Sciences