{"685297":{"#nid":"685297","#data":{"type":"news","title":"Decades in the Making: Seeing the Full Impact From Air Pollution Reductions","body":[{"value":"\u003Cp\u003EResearchers at Georgia Tech have analyzed the seasonal differences of sulfate aerosols \u2014 a major pollutant in the United States \u2014 to examine the long-term impact from sulfur dioxide (SO\u2082) emission reductions since the enactment of the Clean Air Act amendments in 1990.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u003Ca href=\u0022https:\/\/eas.gatech.edu\/\u0022\u003ESchool of Earth and Atmospheric Sciences\u003C\/a\u003E Professor \u003Cstrong\u003EYuhang Wang\u003C\/strong\u003E and his team studied the factors affecting SO\u2082\u0026nbsp;and sulfate concentrations during winter and summer in the \u201cRust Belt\u201d \u2014 from New York through the Midwest \u2014 and the Southeast regions of the U.S. over two decades (2004 to 2023). Supported by the\u0026nbsp;\u003Ca href=\u0022https:\/\/www.nsf.gov\/\u0022\u003ENational Science Foundation\u003C\/a\u003E and Georgia Tech\u2019s\u0026nbsp;\u003Ca href=\u0022https:\/\/research.gatech.edu\/sustainability\u0022\u003EBrook Byers Institute for Sustainable Systems\u003C\/a\u003E, the team also developed an ensemble machine learning approach to project seasonal patterns until 2050.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u201cPower plants, particularly those burning coal and oil, are a major source of SO\u2082 emissions in these regions,\u201d says Wang, who co-authored, with Ph.D. students \u003Cstrong\u003EFanghe Zhao\u003C\/strong\u003E and \u003Cstrong\u003EShengjun Xi\u003C\/strong\u003E, the study recently published in\u0026nbsp;\u003Ca href=\u0022https:\/\/pubs.acs.org\/doi\/full\/10.1021\/acs.estlett.5c00731\u0022\u003E\u003Cem\u003EEnvironmental Science \u0026amp; Technology Letters\u003C\/em\u003E\u003C\/a\u003E.\u0026nbsp;\u003C\/p\u003E\u003Ch3\u003E\u003Cstrong\u003ESeasonal differences in atmospheric chemistry\u0026nbsp;\u003C\/strong\u003E\u003C\/h3\u003E\u003Cp\u003EIn the U.S., the chemistry in the atmosphere varies among the seasons. During summer, solar radiation from ample sunlight activates oxidant reactions that produce hydrogen peroxide (H\u003Cem\u003E\u2082\u003C\/em\u003EO\u003Cem\u003E\u2082\u003C\/em\u003E) in the atmosphere. The supply of H\u003Cem\u003E\u2082\u003C\/em\u003EO\u003Cem\u003E\u2082\u003C\/em\u003E is determined by the amount of emitted air pollution, and once in the atmosphere, H\u003Cem\u003E\u2082\u003C\/em\u003EO\u003Cem\u003E\u2082\u003C\/em\u003E can oxidize SO\u2082\u0026nbsp;quickly into sulfate aerosols in the aqueous phase.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003ESulfate aerosols from the oxidation of SO\u2082 contribute to the formation of particulate matter less than 2.5 micrometers in diameter (PM2.5). Particulate sulfate poses significant environmental and public health risks, including air pollution, acid rain, and circulatory and respiratory issues.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u201cThe supply of H\u003Cem\u003E\u2082\u003C\/em\u003EO\u003Cem\u003E\u2082\u003C\/em\u003E\u0026nbsp;in summer is eight times greater than in winter \u2014 a huge difference \u2014 which means sulfate concentrations are generally higher in summer and a reduction in SO\u2082 emissions leads to a proportional decrease in sulfate concentrations,\u201d explains Wang. \u201cWhen SO\u2082 emissions exceed the available supply of H\u003Cem\u003E\u2082\u003C\/em\u003EO\u003Cem\u003E\u2082\u003C\/em\u003E in winter, the reduction in sulfate concentrations can be much smaller because of a \u2018chemical damping\u2019 effect that causes sulfate levels to decline more slowly than SO\u2082 emissions.\u201d\u0026nbsp;\u003C\/p\u003E\u003Ch3\u003E\u003Cstrong\u003ENarrowing the disparities between seasonal sulfate levels\u0026nbsp;\u003C\/strong\u003E\u003C\/h3\u003E\u003Cp\u003EThe study\u2019s two-decade observations revealed distinct patterns in the reduction of SO\u2082\u0026nbsp;emissions and sulfate concentrations during winter and summer.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EWhile SO\u2082\u0026nbsp;emissions significantly decreased in both seasons\u00ad over time \u2014 primarily from the Clean Air Act and more power plants transitioning from coal to natural gas \u2014 the reduction of sulfate concentrations initially showed large seasonal differences. However, over the past decade, the disparity between winter and summer sulfate levels narrowed as SO\u2082\u0026nbsp;emissions decreased.\u003C\/p\u003E\u003Cp\u003EAccording to Wang, the seasonal disparity of sulfate was caused by changing chemical regimes in winter over time. Although the lower supply of H\u003Cem\u003E\u2082\u003C\/em\u003EO\u003Cem\u003E\u2082\u003C\/em\u003E remained stable in winter, SO\u2082\u0026nbsp;wintertime emissions were higher from 2004 to 2013, then dropped below the level of H\u003Cem\u003E\u2082\u003C\/em\u003EO\u003Cem\u003E\u2082\u003C\/em\u003E\u0026nbsp;after 2013 \u2014 reaching parity with the levels of reduced SO\u2082\u0026nbsp;emissions in the summer.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u201cWhen you have this complexity of atmospheric chemistry, there is a non-linear effect in winter \u2014 as SO\u2082\u0026nbsp;emissions decreased, sulfate aerosol production efficiency increased until 2013, then flattened as of today. The reduction in sulfate aerosols initially lagged behind the decrease in SO\u2082 emissions but eventually caught up as a result of sustained air quality control efforts,\u201d says Wang. \u201cConversely, there is a simple, linear effect in summer \u2014 the more SO\u2082\u0026nbsp;emissions, the more sulfate aerosols in the atmosphere \u2014 and if you reduce one, the other is reduced by the same proportion.\u201d\u003C\/p\u003E\u003Ch3\u003E\u003Cstrong\u003EDecades-long full impact\u0026nbsp;\u003C\/strong\u003E\u003C\/h3\u003E\u003Cp\u003EFrom now until 2050, the researchers\u2019 machine learning projections indicate a continuing decrease of winter and summer sulfate levels, which are currently around 20 percent, as SO\u2082\u0026nbsp;emission controls achieve comparable efficacy across the seasons.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u201cWe\u2019re now seeing the full impact from the Clean Air Act,\u201d concludes Wang, \u201cand the nation\u2019s sustained effort in pollution reduction is key to improving air quality and health outcomes.\u201d\u003C\/p\u003E","summary":"","format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003E\u003Cem\u003EGeorgia Tech researchers analyze seasonal differences of SO\u2082 and sulfate concentrations in the atmosphere over decades to determine the long-term impact of sustained air quality control efforts.\u003C\/em\u003E\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"Georgia Tech researchers analyze seasonal differences of SO\u2082 and sulfate concentrations in the atmosphere over decades to determine the long-term impact of sustained air quality control efforts."}],"uid":"27465","created_gmt":"2025-09-25 21:44:42","changed_gmt":"2025-12-30 19:40:19","author":"Annette Filliat","boilerplate_text":"","field_publication":"","field_article_url":"","location":"Atlanta, GA","dateline":{"date":"2025-09-26T00:00:00-04:00","iso_date":"2025-09-26T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"678151":{"id":"678151","type":"image","title":"NOAA Iridescent Clouds","body":"\u003Cp\u003EIridescent clouds before sunset \/ Source: NOAA\u003Cbr\u003E\u0026nbsp;\u003C\/p\u003E","created":"1758842239","gmt_created":"2025-09-25 23:17:19","changed":"1758842239","gmt_changed":"2025-09-25 23:17:19","alt":"NOAA Iridescent Clouds","file":{"fid":"262138","name":"NOAA-North-Carolina-Clouds.png","image_path":"\/sites\/default\/files\/2025\/09\/25\/NOAA-North-Carolina-Clouds.png","image_full_path":"http:\/\/hg.gatech.edu\/\/sites\/default\/files\/2025\/09\/25\/NOAA-North-Carolina-Clouds.png","mime":"image\/png","size":3019658,"path_740":"http:\/\/hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/2025\/09\/25\/NOAA-North-Carolina-Clouds.png?itok=aC8m6MF-"}},"678152":{"id":"678152","type":"image","title":"Yuhang Wang ","body":"\u003Cp\u003ESchool of Earth and Atmospheric Sciences Professor Yuhang Wang and his team co-authored the study, \u201cChemically Induced Decline in Wintertime SO\u003Cem\u003E\u2082\u003C\/em\u003E\u0026nbsp;Emission Control Efficacy,\u201d which was published in \u003Cem\u003EEnvironmental Science \u0026amp; Technology Letters\u003C\/em\u003E.\u003Cbr\u003E\u003Cbr\u003E\u0026nbsp;\u003C\/p\u003E","created":"1758842459","gmt_created":"2025-09-25 23:20:59","changed":"1758842459","gmt_changed":"2025-09-25 23:20:59","alt":"Yuhang Wang ","file":{"fid":"262139","name":"GT-CoS-Yuhang-Wang-Headshot.png","image_path":"\/sites\/default\/files\/2025\/09\/25\/GT-CoS-Yuhang-Wang-Headshot.png","image_full_path":"http:\/\/hg.gatech.edu\/\/sites\/default\/files\/2025\/09\/25\/GT-CoS-Yuhang-Wang-Headshot.png","mime":"image\/png","size":6600933,"path_740":"http:\/\/hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/2025\/09\/25\/GT-CoS-Yuhang-Wang-Headshot.png?itok=Wga0XlvH"}},"678153":{"id":"678153","type":"image","title":"Fanghe Zhao","body":"\u003Cp\u003EPh.D. student Fanghe Zhao\u003C\/p\u003E","created":"1758843155","gmt_created":"2025-09-25 23:32:35","changed":"1758843155","gmt_changed":"2025-09-25 23:32:35","alt":"Fanghe Zhao","file":{"fid":"262141","name":"GT-CoS-Fanghe-Zhao-Headshot.png","image_path":"\/sites\/default\/files\/2025\/09\/25\/GT-CoS-Fanghe-Zhao-Headshot_0.png","image_full_path":"http:\/\/hg.gatech.edu\/\/sites\/default\/files\/2025\/09\/25\/GT-CoS-Fanghe-Zhao-Headshot_0.png","mime":"image\/png","size":10158591,"path_740":"http:\/\/hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/2025\/09\/25\/GT-CoS-Fanghe-Zhao-Headshot_0.png?itok=rmCNXJa_"}},"678154":{"id":"678154","type":"image","title":"Shengjun Xi","body":"\u003Cdiv\u003EPh.D. student Shengjun Xi\u003C\/div\u003E","created":"1758843283","gmt_created":"2025-09-25 23:34:43","changed":"1758843283","gmt_changed":"2025-09-25 23:34:43","alt":"Shengjun Xi","file":{"fid":"262142","name":"GT-CoS-Shengjun-Xi-Headshot.png","image_path":"\/sites\/default\/files\/2025\/09\/25\/GT-CoS-Shengjun-Xi-Headshot.png","image_full_path":"http:\/\/hg.gatech.edu\/\/sites\/default\/files\/2025\/09\/25\/GT-CoS-Shengjun-Xi-Headshot.png","mime":"image\/png","size":3927326,"path_740":"http:\/\/hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/2025\/09\/25\/GT-CoS-Shengjun-Xi-Headshot.png?itok=ut8CDG5t"}}},"media_ids":["678151","678152","678153","678154"],"related_links":[{"url":"https:\/\/cos.gatech.edu\/news\/study-reveals-wintertime-formation-large-pollution-particles-chinas-skies","title":"Study Reveals Wintertime Formation of Large Pollution Particles in China\u2019s Skies"},{"url":"https:\/\/research.gatech.edu\/everlasting-african-wildfires-fueled-aerosol-feedback","title":"Everlasting African Wildfires Fueled by Aerosol Feedback"}],"groups":[{"id":"1188","name":"Research Horizons"},{"id":"367481","name":"SEI Energy"},{"id":"1280","name":"Strategic Energy Institute"}],"categories":[{"id":"144","name":"Energy"}],"keywords":[{"id":"187915","name":"go-researchnews"},{"id":"192254","name":"cos-climate"},{"id":"194631","name":"cos-georgia"},{"id":"186858","name":"go-sei"}],"core_research_areas":[{"id":"39531","name":"Energy and Sustainable Infrastructure"}],"news_room_topics":[{"id":"71911","name":"Earth and Environment"},{"id":"71891","name":"Health and Medicine"},{"id":"71881","name":"Science and Technology"}],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003E\u003Ca href=\u0022mailto:jess@cos.gatech.edu\u0022\u003E\u003Cstrong\u003EJess Hunt-Ralston\u003C\/strong\u003E\u003C\/a\u003E\u003Cbr\u003EDirector of Communications\u003Cbr\u003ECollege of Sciences at Georgia Tech\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EWriter: Annette Filliat\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EEditor: Lindsay Vidal\u0026nbsp;\u003C\/strong\u003E\u003C\/p\u003E","format":"limited_html"}],"email":["jess@cos.gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}