Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New proxy reveals how humans have disrupted the nitrogen cycle

08.06.2009
More and more, scientists are getting a better grip on the nitrogen cycle. They are learning about sources of nitrogen and how this element changes as it loops from the nonliving, such as the atmosphere, soil or water, to the living, whether plants or animals. Scientists have determined that humans are disrupting the nitrogen cycle by altering the amount of nitrogen that is stored in the biosphere.

The chief culprit is fossil fuel combustion, which releases nitric oxides into the air that combine with other elements to form smog and acid rain. But it has been difficult to know precisely the extent to which such emissions have altered the nitrogen balance.

Researchers from Brown University and the University of Washington have found a new way to make the link. The scientists show that comparing nitrogen isotopes in their deposited form — nitrates — can reveal the sources of atmospheric nitric oxide. In a paper published this week in Science, the group traces the source of nitrates to nitric oxides released through fossil fuel burning that parallels the beginning of the Industrial Revolution. The group also reveals that the greatest change in nitrogen isotope ratios occurred between 1950 and 1980, following a rapid increase in fossil fuel emissions.

"What we find is there has been this significant change to the nitrogen cycle over the past 300 years," said Meredith Hastings, assistant professor of geological sciences at Brown and the paper's lead author. "So we've added this new source — and not just a little bit of it, but a lot of it."

To make the link, Hastings, with Julia Jarvis and Eric Steig from the Department of Earth and Space Sciences at the University of Washington, examined at high resolution for the first time two isotopes of nitrogen found in nitrates in a Greenland ice core. The core, 100 meters long and taken at the peak of the Greenland ice cap in June 2006, contains a record of nitrates from about 1718 to 2006, according to the group.

Tests showed the ratio of the nitrogen-15 isotope to the more common nitrogen-14 isotope had changed from pre-industrial times to the present.

"The only way I can explain the trend over time," Hastings said, "are the nitric oxide sources, because we've introduced this whole new source — and that's fossil fuels burning."

Steig said the work also addresses a long-standing question about changes in lake chemistry in remote regions. "Sediment cores in Arctic lakes show that there have been significant 20th-century declines in the nitrogen isotopic composition of organic nitrogen," Steig said. "It's been unclear whether these are due to changes in the lake biogeochemistry or to the direct effect of changes in the isotopic composition of the incoming nitrate from the atmosphere. Our study makes it clear that it is primarily the latter."

The group now wants to determine the ratio of nitrogen-14 and nitrogen-15 isotopes for individual sources of nitric oxides, including lightning, biomass burning, bacterial "fixing" of nitrogen, and fossil fuel burning. The goal would be to pinpoint sources of nitrogen overloading, whether natural or human-caused.

"For example in Narragansett Bay, we could distinguish between nitrogen caused by sewage overflows or vehicular pollution, power plants, fertilizers, or other sources and know how to attack the problem," Hastings said.

Even more, the researchers want to quantify changes in the natural sources of nitric oxides and see whether climate change is influencing those processes.

The task is complicated, however, because nitrogen, when cycling through the atmosphere or deposited on land or in water, is subject to influences that can alter the isotopic ratios, thus masking the source. So, the scientists will need to tease out the extent of those alterations to trace the isotopic signatures of nitric oxide sources accurately.

The research was funded by the National Science Foundation's Office of Polar Programs and the Joint Institute for the Study of the Atmosphere and the Ocean (JISAO).

Richard Lewis | EurekAlert!
Further information:
http://www.Brown.edu

More articles from Earth Sciences:

nachricht A promising target in the quest for a 1-million-year-old Antarctic ice core
24.05.2018 | University of Washington

nachricht Tropical Peat Swamps: Restoration of Endangered Carbon Reservoirs
24.05.2018 | Leibniz-Zentrum für Marine Tropenforschung (ZMT)

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Powerful IT security for the car of the future – research alliance develops new approaches

The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.

Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...

Im Focus: Molecular switch will facilitate the development of pioneering electro-optical devices

A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.

The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...

Im Focus: LZH showcases laser material processing of tomorrow at the LASYS 2018

At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.

At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...

Im Focus: Self-illuminating pixels for a new display generation

There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?

At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

In focus: Climate adapted plants

25.05.2018 | Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

 
Latest News

In focus: Climate adapted plants

25.05.2018 | Event News

Flow probes from the 3D printer

25.05.2018 | Machine Engineering

Less is more? Gene switch for healthy aging found

25.05.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>