Nitrogen oxides, the noxious byproduct of burning fossil fuels that can return to Earth in rain and snow as harmful nitrate, could taint urban water supplies and roadside waterways more than scientists and regulators realize, according to research published Oct. 20 in the online edition of the journal Environmental Science and Technology.
The three-year study, led by Emily Elliott, a professor of geology and planetary science in the University of Pittsburgh’s School of Arts and Sciences, recommends that urban areas and roadways be specifically monitored for nitrogen deposition. Nitrogen oxides can contribute to a wide variety of environmental and health ills. Nitrate—which forms when exhaust from vehicles and smokestacks oxidizes in the atmosphere—is an important contributor to acid rain and can result in stream and soil acidification, forest decline, and coastal water degradation.
Elliott and her colleagues conducted the first large-scale application of a method for determining the source of atmospheric nitrate on rain and snow samples from 33 precipitation collection sites across the Midwestern and Northeastern United States, including Pennsylvania. The sites belong to the National Atmospheric Deposition Program (NADP), a cooperative of private organizations and U.S. government agencies that analyzes precipitation for chemicals such as nitrogen, sulfur, and mercury from more than 250 sites in the United States, Puerto Rico, and the Virgin Islands.
Although vehicles are the single largest source of nitrogen oxides in this region, the researchers found by analyzing the stable isotope composition of nitrate that the primary source of nitrate in their samples were stationary sources, such as power plants and factories, located hundreds of miles away. Stationary sources pump pollutants high into the atmosphere where they can be transported for long distances before falling to the ground. Vehicle exhaust is released close to the ground and more likely deposited over shorter distances near roadways. Most monitoring sites in the NADP network are deliberately located in relatively rural settings away from urban, industrial, or agricultural centers.
The amount of nitrate pouring over the cities and busy roadways thick with vehicles could be higher than monitoring data at most NADP sites reflect, and it is possible that a significant amount of this atmospheric nitrate finds its way into sensitive water supplies, such as the Ohio River or Chesapeake Bay. In aquatic ecosystems, excess nitrate can promote an overgrowth of oxygen-consuming algae and lead to an oxygen deficiency in the water known as hypoxia. Hypoxia kills marine creatures and creates “dead zones” akin to the lifeless area of the Gulf of Mexico at the mouth of the Mississippi River. Determining the fate of major sources of nitrogen emissions is necessary to develop sound regulatory and mitigation strategies for both air and water quality, Elliott said.
“Our results highlight the need to improve our understanding of the fate of vehicle emissions—one way we can do this is by expanding monitoring networks to include more urban sites,” Elliott said, adding that both vehicle and stationary sources are major contributors to air pollution in the region studied.
Elliott said that future research will further characterize the isotopic ratios of nitrogen oxides from various emission sources and quantify how these values change during transport and with different emission controls. She is looking for industrial partners who can provide samples from smokestacks for analysis. Additionally, Elliott is interested in establishing an urban precipitation monitoring site in Pittsburgh to assess pollution sources that contribute to nitrate deposition in the Pittsburgh region.
Morgan Kelly | EurekAlert!
From the Arctic to the tropics: researchers present a unique database on Earth’s vegetation
20.11.2018 | Martin-Luther-Universität Halle-Wittenberg
Fading stripes in Southeast Asia: First insight into the ecology of an elusive and threatened rabbit
20.11.2018 | Forschungsverbund Berlin e.V.
Max Planck researchers revel the nano-structure of molecular trains and the reason for smooth transport in cellular antennas.
Moving around, sensing the extracellular environment, and signaling to other cells are important for a cell to function properly. Responsible for those tasks...
Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection"--the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion--in the Earth's magnetotail, the magnetic environment that trails behind the planet.
Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can...
Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.
Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...
Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.
In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...
On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.
19.11.2018 | Event News
09.11.2018 | Event News
06.11.2018 | Event News
20.11.2018 | Life Sciences
20.11.2018 | Life Sciences
20.11.2018 | Physics and Astronomy