Stephen Hamilton, an aquatic ecologist at Michigan State University, studied nine streams that flowed through cities, forests and agricultural land in the Kalamazoo River watershed of southwestern Michigan as part of a nationwide team seeking to understand what happens to the nitrogen that is washed into the water.
The results, published in this week’s issue of Nature, provide the most comprehensive understanding yet of how the complex network of rivers and streams – mighty and small – naturally process nitrogen from the waters before it ends up causing trouble downstream.
“This study presents a picture of unprecedented detail of the extent to which streams can remove nitrate,” Hamilton said. “We also now have a better idea of what makes one stream more efficient at nitrate removal than another.”
The stakes are high. Nitrogen gets into the water as runoff from fertilizers and wastes from human activities. Too much nitrogen can cause noxious algal blooms and lead to oxygen depletion and death of fish and shellfish, as has been recently reported in the Gulf of Mexico.
Rivers and streams naturally can act as the “kidneys of our landscape,” according to lead author Patrick Mulholland of the Oak Ridge National Laboratory and University of Tennessee. They can significantly improve the quality of water, thereby reducing the potential for problems in downstream environments.
Hamilton and his team from MSU and the University of Notre Dame spent three years conducting experiments in which they added small amounts of a harmless, nonradioactive isotope of nitrogen, N-15, into streams. They then were able to track the isotope as it traveled downstream and record what processes removed it from the water.
What they found, which was supported by experiments across 72 streams in eight regions across the United States and Puerto Rico, was that the nitrate was taken up from stream water by tiny organisms such as algae, fungi and bacteria. In addition, a considerable fraction was permanently removed from streams by a bacterial process known as denitrification, which converts nitrate to nitrogen gas that then escapes harmlessly into the atmosphere.
Hamilton said they also learned that not all streams are created equal. Streams that are allowed to meander naturally through a complex channel were more efficient at filtering pollutants than streams that had been engineered to quickly convey water away from farmland or developments.
“What we often do to streams to make them more like drains diminishes their ability to reduce pollutants,” Hamilton said. “Complexity – both biological and physical – helps streams be more effective at removing nitrogen.”
In addition, the effectiveness of streams to remove nitrate was greatest if the streams were not overloaded by nitrogen sources such as fertilizers and wastes from human activities. If overloaded, a stream or river passes nitrogen downstream, where it can cause problems in oceans and coastal waterways.
This appears to put two imperatives at odds – removing water quickly from urban areas or agricultural fields versus trying to reduce pollutants. But Hamilton said there are ways to satisfy both goals, such as directing waters into wetland ponds or buffer strips that allow nature time to gobble the nitrates.
The study, Hamilton said, now presents a comprehensive picture that can help guide stream and river management and land-use planning.
Stephen Hamilton | EurekAlert!
Smart Data Transformation – Surfing the Big Wave
02.12.2016 | Fraunhofer-Institut für Angewandte Informationstechnik FIT
Climate change could outpace EPA Lake Champlain protections
18.11.2016 | University of Vermont
Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.
Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
09.12.2016 | Life Sciences
09.12.2016 | Ecology, The Environment and Conservation
09.12.2016 | Health and Medicine