“Nitrogen removal in streams is important because it reduces the potential for eutrophication – the excessive growth of algae and aquatic plants in downstream lakes and coastal marine waters,” said Jack Webster, professor of biology at Virginia Tech. “Eutrophication in the Chesapeake Bay has damaged the oyster industry in Virginia and in the Gulf of Mexico, the Mississippi River has created a vast zone of oxygen depletion with adverse effects on fisheries.”
The research process meant 24-hour monitoring. “The Stream Team involvement was very important,” said Webster.
In the first phase of the study, the scientists added small amounts of a non-radioactive isotope of nitrogen to streams as nitrate, the most prevalent form of nitrogen pollution. They then measured how far downstream the nitrate traveled and how what processes removed it from the water.
The scientists found that the nitrate was taken up from stream water by algae and microorganisms. In addition, a fraction was permanently removed from streams by denitrification, a bacterial process that converts nitrate to nitrogen gas, which harmlessly joins an atmosphere already predominantly composed of nitrogen gas.
In the second phase of the study, the scientists developed a model that predicts nitrate removal as water flows through small streams and into larger streams and rivers. “Our model showed that the entire stream network is important in removing pollution from stream water,” said Patrick Mulholland, lead author of the study, a member of ORNL’s Environmental Sciences Division, and a faculty member at the University of Tennessee. “In addition, the effectiveness of streams to remove nitrate was greatest if the streams were not overloaded by pollutants such as fertilizers and wastes from human activities.”
The largest removal occurred when nitrate entered small healthy streams and traveled throughout the network before reaching large rivers. The scientists concluded from their research that streams and rivers are effective filters that help reduce the amount of nitrate pollution exported from landscapes and thereby reduce eutrophication problems, Webster said.
Authors of the article, “Stream denitrification across biomes and its response to anthropogenic nitrate loading,” are Mulholland; Ashley M. Helton and Geoffrey C. Poole of the University of Georgia (UGA); Robert O. Hall Jr. of the University of Wyoming; Stephen K. Hamilton of Michigan State University; Bruce J. Peterson of Marine Biological Laboratory at Woods Hole; Jennifer L. Tank, a Virginia Tech Ph.D. graduate now at the University of Notre Dame; Linda R. Ashkenas of Oregon State University; Lee W. Cooper of the University of Tennessee; Clifford N. Dahm of the Univesity of New Mexico; Walter K. Dodds of Kansas State University, Stuart E. G. Findlay of the Institute of Ecosystem Studies, Millbrook, NY; Stanley V. Gregory of Oregon State; Nancy B. Grimm of Arizona State University; Sherri L. Johnson of the U.S. Forest Service, Corvallis, Ore.; William H. McDowell of the University of New Hampshire; Judy L. Meyer of UGA; H.Maurice Valett, associate professor of biological sciences at Virginia Tech; Webster; Clay P. Arango and Jake J. Beaulieu of Notre Dame; Melody J. Bernot of Ball State University; Amy J. Burgin of Michigan State; Chelsea L. Crenshaw, a Virginia Tech master’s of science graduate now at the University of New Mexico; Laura Taylor Johnson, who was a Virginia Tech undergraduate and is now at Notre Dame, B. R. (Bobbie) Niederlehner, laboratory specialist at Virginia Tech; Jonathan M. O’Brien of Michigan State; Jody D. Potter of the University of New Hampshire; Richard W. Sheibley of Arizona State; Daniel J. Sobota, who was a Virginia Tech undergraduate now at Oregon State; and Suzanne M. Thomas of Woods Hole.
There were many more people involved than even the list of co-authors reflects, Webster said. “This project was part of collaboration among a group of people who have worked together since 1995,” he said. “The undergraduate research with the Stream Team at Virginia Tech has been important in guiding students toward graduate school and careers.”
The National Science Foundation funded the research. The authors also thanked the U.S. Forest Service, National Park Service, and many private landowners for permission to conduct experiments on their lands.
Value from wastewater
16.08.2017 | Hochschule Landshut
Species Richness – a false friend? Scientists want to improve biodiversity assessments
01.08.2017 | Carl von Ossietzky-Universität Oldenburg
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
Researchers from the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science, the Italian Space Agency (ASI), and the Instituto Geofisico--Escuela Politecnica Nacional (IGEPN) of Ecuador, showed an increasing volcanic danger on Cotopaxi in Ecuador using a powerful technique known as Interferometric Synthetic Aperture Radar (InSAR).
The Andes region in which Cotopaxi volcano is located is known to contain some of the world's most serious volcanic hazard. A mid- to large-size eruption has...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
16.08.2017 | Physics and Astronomy
16.08.2017 | Materials Sciences
16.08.2017 | Interdisciplinary Research