Subscribe free to our newsletters via your
. 24/7 Space News .

Greenland ice cores show industrial record of acid rain, success of US Clean Air Act
by Staff Writers
Seattle WA (SPX) Apr 17, 2014

South Dakota State University's Jihong Cole-Dai is logging an ice-core sample at Summit, Greenland. Image courtesy Joel Savarino, Laboratory of Glaciology and Geophysics of the Environment (LGGE).

The rise and fall of acid rain is a global experiment whose results are preserved in the geologic record. By analyzing samples from the Greenland ice sheet, University of Washington atmospheric scientists found clear evidence of the U.S. Clean Air Act. They also discovered a link between air acidity and how nitrogen is preserved in layers of snow, according to a paper published this week in the Proceedings of the National Academy of Sciences.

Forty-five years ago, acid rain was killing fish and dissolving stone monuments on the East Coast. Air pollution rose beginning with the Industrial Revolution and started to improve when the U.S. Clean Air Act of 1970 required coal power plants and other polluters to scrub sulfur out of their smokestacks.

UW researchers began their study of ice cores interested in smog, not acid rain. They discovered a link between the two forms of pollution in the geologic record.

Nitrogen is emitted as a short-lived compound, NOx, which causes ground-level ozone, the main ingredient in smog, and relates to compounds that are the "detergent" of the atmosphere. Sources of NOx include smokestacks and vehicle tailpipes, as well as wildfires, soil microbes or reactions triggered by lightning strikes.

Teasing out the sources of NOx through history might tell us about the atmosphere of the past, how methane, ozone and other chemicals change in the atmosphere, and also provide a measure of global human emissions.

"How much the nitrate concentrations in ice core records can tell about NOx and the chemistry in the past atmosphere is a longstanding question in the ice-core community," said lead author Lei Geng, a UW postdoctoral researcher in atmospheric sciences.

Unlike other gases, short-lived NOx can't be measured directly from air bubbles trapped in ice cores. Within a day or two most of the NOx changes into nitrate, a water-soluble molecule essential to life that gets deposited in soil and snow.

Earlier research by co-author Eric Steig, a UW professor of Earth and space sciences, suggested that comparing amounts of the two stable forms of nitrogen - nitrogen-15 and nitrogen-14 - in nitrate could pinpoint the emission sources of NOx. Ice cores from Greenland and North American lake sediments showed the nitrogen-15 ratio gradually decreasing since 1850, suggesting a corresponding rise in human emissions.

The new research says: not so fast. The detailed measurements of nitrate, NOx and sulfur show the nitrogen isotope ratio leveling off in 1970, and suggests that ratio is sensitive to the same chemicals that cause acid rain.

"This shows that the relationship between emissions and the isotopes is less direct than we thought, and the final signal recorded in the Greenland ice cores is actually not just the nitrogen emission, but the combined effect of sulfur and nitrogen emissions," Steig said.

The ice cores used in the study were collected in 2007 at Summit Station, Greenland. Total amounts of nitrate for each year were measured and calculated at South Dakota State University, where Geng did his doctoral work. The different forms, or isotopes, were measured in UW's IsoLab.

Geng's work showed that the long-term decrease in the nitrogen-15 isotope since 1850, and its leveling off in 1970, are linked to changes in air chemistry. Airborne nitrate can exist as a gas or a particle, and nitrate with lighter isotopes tends to exist as a gas. But he found that the total fraction of nitrate present as gas or particle varies with the acidity of the atmosphere, and the acidic air causes more of the light isotopes to exist as a gas.

"The isotope records really closely follow the atmospheric acidity trends," said co-author Becky Alexander, a UW associate professor of atmospheric sciences. "You can really see the effect of the Clean Air Act in 1970, which had the most dramatic impact on emission of acid from coal-fired power plants."

What's more, airborne nitrate dissolves in water and falls at the poles as snow. While that snow sits on the ground, sunlight bouncing off the surface triggers chemical reactions that send some of it back into a gas form. Acid air can also influence the reactivity of nitrate in snow and thus the preservation of nitrate in ice cores.

Other ice core records might also be affected by acidity in air, Alexander said. No effect would be expected for stable gases like carbon dioxide and oxygen, or for the water molecules used to calculate temperature variations through time. But acidity in air could influence deposition and preservation of other volatile compounds such as chlorine, mercury or organic materials in ice cores.

Eventually, better understanding of the air chemistry during formation of the layers could allow researchers to correct for the effect, extracting better information of the past from these compounds in the geologic record.

The research was funded by the National Science Foundation. Other co-authors are Eric Sofen and Andrew Schauer at the UW, Jihong Cole-Dai at South Dakota State University and Joel Savarino at University of Grenoble in France. The lead author of the earlier study is Meredith Hastings, now at Brown University.


Related Links
University of Washington
The Air We Breathe at

Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks DiggDigg RedditReddit GoogleGoogle

Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News

Like a giant elevator to the stratosphere
Potsdam, Germany (SPX) Apr 08, 2014
An international team of researchers headed by Potsdam scientist Dr. Markus Rex from the Alfred Wegener Institute has discovered a previously unknown atmospheric phenomenon over the South Seas. Over the tropical West Pacific there is a natural, invisible hole extending over several thousand kilometres in a layer that prevents transport of most of the natural and manmade substances into the strat ... read more

Russian Federal Space Agency is elaborating Moon exploration program

Science, Discovery Channels to broadcast private race to the moon

Take the Plunge: LADEE Impact Challenge

Land a Lunar Laser Reflector Now!

Gusev Crater once held a lake after all

Mars Exploration in a Deep Mine

Images From NASA Mars Rover Include Bright Spots

NASA's rover Curiosity discovers Australia on Mars, sort of

Minorities on display in Chinese tourist boom

Veggie Will Expand Fresh Food Production on ISS

Reporters See NASA's Latest High Tech Exploration Tool Before Testing

Recycling astronaut urine for energy and drinking water

China launches experimental satellite

Tiangong's New Mission

"Space Odyssey": China's aspiration in future space exploration

China to launch first "space shuttle bus" this year

'Cherry tree from space' mystery baffles Japan

Extra-terrestrial Tweet-up links Tokyo with space

Russian cargo ship docks to space station

Progress Departs, New Cargo Ships Awaiting Launch

NASA Ames Launches Nanosatellites, Science Experiments on SpaceX Rocket

On-board camera provides a unique perspective on Arianespace Flight VS07

The DZZ-HR satellite is fueled for Arianespace's upcoming Vega launch

EUTELSAT 3B Mission Status Update

Chance meeting creates celestial diamond ring

Faraway Moon or Faint Star? Possible Exomoon Found

The Importance of Planetary Plumes

Orbital physics is child's play with 'Super Planet Crash'

Vanguard Space Technologies Antenna Reflectors on Amazonas Satellite Launch

Middle Eastern country orders more border radar

Headwall Extends Global Reach in Asia/Pac and Israel

A new twist for better steel

The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.