{"505161":{"#nid":"505161","#data":{"type":"news","title":"Study: Atmospheric Sulfate Particles Reduced, but as Acidic as Ever","body":[{"value":"\u003Cp\u003EWhen acidic materials are spilled, the clean-up procedure involves adding a base chemical to neutralize the acid. Up to a point, the more base added, the more neutral and less toxic the spill becomes.\u003C\/p\u003E\u003Cp\u003ESomething very similar is happening in the atmosphere. Acidic sulfur emissions from power plants have been rapidly declining over the past decade, and the neutralizing base \u2013 ammonia \u2013 is emitted from a different source, and has not declined. This has led many atmospheric scientists to assume that the ambient sulfate particles we all breathe are becoming less acidic and therefore less toxic.\u003C\/p\u003E\u003Cp\u003EBut a new study shows this intuitive expectation hasn\u2019t happened, at least not in the Southeast United States, where the remaining sulfate particles appear to be as acidic as ever.\u003C\/p\u003E\u003Cp\u003EThough they were surprised by the findings, researchers at the Georgia Institute of Technology have developed an explanation that may also ease concerns about yet another atmospheric pollutant that scientists had feared would take the place of the reduced sulfates. Beyond human health, the research has broader implications for atmospheric pollution and global climate change modeling.\u003C\/p\u003E\u003Cp\u003ESponsored by the National Science Foundation and the U.S. Environmental Protection Agency, the research was reported February 22 in the journal\u0026nbsp;\u003Cem\u003ENature Geoscience\u003C\/em\u003E. The conclusions are based on observed gas and aerosol composition, humidity and temperature data collected at a site in rural Alabama as part of the Southern Oxidant and Aerosol Study (SOAS).\u003C\/p\u003E\u003Cp\u003E\u201cSulfates are the major source of acidity in the atmosphere, and gas-phase ammonia \u2013 mostly from agriculture \u2013 had been expected to react with the remaining particles to reduce their acidity,\u201d explained \u003Ca href=\u0022http:\/\/www.eas.gatech.edu\/people\/Rodney_Weber\u0022\u003ERodney Weber\u003C\/a\u003E, a professor in Georgia Tech\u2019s School of Earth \u0026amp; Atmospheric Sciences.\u003C\/p\u003E\u003Cp\u003E \u201cBut what we found is that the system that forms the sulfate particles isn\u2019t very sensitive to the amounts of ammonia neutralizer. This has implications because the acidity of these particles affects other important atmospheric reactions.\u201d\u003C\/p\u003E\u003Cp\u003EInstead of reacting with all of the available acidic sulfates, the alkaline ammonia emitted from agricultural operations and other sources appears to form an equilibrium between gas-phase compounds and particle compounds. These emissions, though seasonal, have remained largely unchanged.\u003C\/p\u003E\u003Cp\u003EWith the same amount of neutralizing ammonia available to react with a much smaller amount of sulfates, scientists had expected the pH of the sulfate fine particles to rise toward neutral levels. But the pH remains between 0 and 2 \u2013 approximately the same level of acidity as battery acid.\u003C\/p\u003E\u003Cp\u003E\u201cSulfates stay in the particle phase and are not volatile,\u201d said Weber, who is the paper\u2019s first author. \u201cAmmonia likes to volatilize and, in part, stay in the gas phase. This means that it is very difficult for it to fully neutralize the acidic particles, which explains why the system tends to be insensitive to the amounts of neutralizer available.\u201d\u003C\/p\u003E\u003Cp\u003EParticles smaller than 2.5 microns in diameter \u2013 known as PM\u003Csub\u003E2.5\u003C\/sub\u003E\u0026nbsp;\u2013 have human health implications because they can travel deep into the lungs to cause respiratory and cardiovascular problems. Because of their potential health impacts, production of the sulfur compounds that form these particles has been reduced by more than 70 percent over the past 15 years in the Southeast United States through installation of scrubbers on coal-fired power plants, replacement of coal with natural gas, and the use of low-sulfur fuels.\u003C\/p\u003E\u003Cp\u003EBeyond reducing the volume of acidic particles in aerosols, cutting the sulfur emissions has also reduced the deposition of acids in lakes and waterways, noted\u0026nbsp;\u003Ca href=\u0022http:\/\/www.cee.gatech.edu\/people\/Faculty\/411\/overview\u0022\u003EArmistead \u201cTed\u201d Russell\u003C\/a\u003E, a Regent\u2019s Professor in Georgia Tech\u2019s School of Civil and Enviromental Engineering\u0026nbsp; and another of the paper\u2019s co-authors.\u003C\/p\u003E\u003Cp\u003EDeclining acidity levels in the sulfate particles had been expected to lead to an increase in the production of atmospheric ammonium nitrates. Those particles also have harmful effects, and had they risen to replace the sulfates, further regulatory action might have been required. The continuing high acidity of the sulfate particles has limited ammonium nitrate formation, the researchers believe.\u003C\/p\u003E\u003Cp\u003E\u201cIt turns out the nitrate levels have been flat,\u201d Russell said. \u201cThey haven\u2019t changed at all, and this is good news. This also has a strong impact on how nitrogen fertilizes ecosystems, which is important to understanding how the earth\u2019s systems respond to pollution.\u201d\u003C\/p\u003E\u003Cp\u003EThe pH of PM\u003Csub\u003E2.5\u003C\/sub\u003E\u0026nbsp;particles can\u2019t be directly measured, so scientists must infer their acidity by studying the distribution of atmospheric species that can be measured and are highly sensitive to the value of the particle pH. This requires modeling, which can be checked by studying compounds \u2013 such as aerosol components and gas-phase components \u2013 that can be directly measured. The data was analyzed using the ISORROPIA-II thermodynamic chemistry model, which was developed by one of the co-authors and is widely used in air quality and climate modeling worldwide.\u003C\/p\u003E\u003Cp\u003EThe paper\u2019s conclusions are based on atmospheric conditions found in the Southeastern United States, and Graduate Research Assistant Hongyu Guo has begun a study of data from the Northeast United States to determine if the same thing happens elsewhere in the country. It is likely that in many parts of the United States \u2013 and in the rest of the world \u2013 the acidity of sulfate particles remains surprisingly high, Weber said.\u003C\/p\u003E\u003Cp\u003EBeyond the health effects, the acidity of the particles affects other aspect of atmospheric chemistry, including the reaction of isoprene, a natural hydrocarbon produced by trees in forests of many kinds, and the solubility of metals found in mineral dust. \u201cThe pH really has a significant effect on many of the processes that affect the overall aerosol mass,\u201d Weber added.\u003C\/p\u003E\u003Cp\u003EThe research may force a re-examination of the role of acidity in atmospheric chemistry, especially where it affects key processes in climate change models.\u003C\/p\u003E\u003Cp\u003E\u201cI think that this research is going to have a long-term influence on how the community evaluates air quality and climate models, because the pH of particles is so important, yet mostly overlooked,\u201d said\u003Ca href=\u0022http:\/\/www.eas.gatech.edu\/people\/Athanasios_Nenes\u0022\u003E Athanasios Nenes\u003C\/a\u003E, a professor and Georgia Power Scholar in the School of Earth \u0026amp; Atmospheric Sciences and the School of Chemical \u0026amp; Biomolecular Engineering and another co-author. \u201cWe think there will be a paradigm shift as people re-evaluate what they had intuitively believed about particle pH and how it responds to emissions.\u201d\u003C\/p\u003E\u003Cp\u003E\u003Cem\u003EThis research was supported by a grant from the National Science Foundation through contract number 1242258, and through U.S. Environmental Protection Agency grants RD835410 and RD834799. The content is solely the responsibility of the authors and does not necessarily represent the official views of the funding agencies.\u003C\/em\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003ECITATION\u003C\/strong\u003E: Rodney J. Weber, Hongyu Guo, Amistead G. Russell and Athanasios Nenes, \u201cHigh aerosol acidity despite declining atmospheric sulfate concentrations over the past 15 years,\u201d (Nature Geoscience, 2016).\u0026nbsp;\u003Ca title=\u0022http:\/\/dx.doi.org\/10.1038\/ngeo2665\u0022 href=\u0022http:\/\/dx.doi.org\/10.1038\/ngeo2665\u0022\u003Ehttp:\/\/dx.doi.org\/10.1038\/ngeo2665\u003C\/a\u003E.\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":[{"value":"Study: Atmospheric Sulfate Particles Reduced, but as Acidic as Ever"}],"field_summary":[{"value":"\u003Cp\u003EWhen acidic materials are spilled, the clean-up procedure involves adding a base chemical to neutralize the acid. Up to a point, the more base added, the more neutral and less toxic the spill becomes.\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"Study: Atmospheric Sulfate Particles Reduced, but as Acidic as Ever"}],"uid":"27271","created_gmt":"2016-02-23 12:55:33","changed_gmt":"2016-10-08 03:20:49","author":"Brad Dixon","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2016-02-23T00:00:00-05:00","iso_date":"2016-02-23T00:00:00-05:00","tz":"America\/New_York"},"extras":[],"hg_media":{"504261":{"id":"504261","type":"image","title":"Field Study","body":null,"created":"1456167600","gmt_created":"2016-02-22 19:00:00","changed":"1475895263","gmt_changed":"2016-10-08 02:54:23","alt":"Field Study","file":{"fid":"204794","name":"machine_outside_0.jpg","image_path":"\/sites\/default\/files\/images\/machine_outside_0_0.jpg","image_full_path":"http:\/\/tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/machine_outside_0_0.jpg","mime":"image\/jpeg","size":625829,"path_740":"http:\/\/tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/machine_outside_0_0.jpg?itok=aiamJKS-"}},"504271":{"id":"504271","type":"image","title":"Study of Sulfate Particles","body":null,"created":"1456167600","gmt_created":"2016-02-22 19:00:00","changed":"1475895265","gmt_changed":"2016-10-08 02:54:25","alt":"Study of Sulfate Particles","file":{"fid":"204795","name":"sulfate-particles.jpg","image_path":"\/sites\/default\/files\/images\/sulfate-particles_0.jpg","image_full_path":"http:\/\/tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/sulfate-particles_0.jpg","mime":"image\/jpeg","size":1666387,"path_740":"http:\/\/tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/sulfate-particles_0.jpg?itok=xnT2_jaE"}}},"media_ids":["504261","504271"],"groups":[{"id":"1240","name":"School of Chemical and Biomolecular Engineering"}],"categories":[{"id":"141","name":"Chemistry and Chemical Engineering"}],"keywords":[{"id":"167750","name":"School of Chemical \u0026 Biomolecular Engineering"},{"id":"169959","name":"sulfate particles"},{"id":"171764","name":"sulfur emissions"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003EJohn Toon (\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E), 404-894-6986\u003C\/p\u003E\u0026nbsp;","format":"limited_html"}],"email":["jtoon@gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}