AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
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Reduced New Particle Formation in Urban Air due to Anthropogenic Emissions Reductions
PROVAT SAHA, Ellis Shipley Robinson, Rishabh Shah, Naomi Zimmerman, Joshua Apte, Albert Presto, Allen Robinson, Carnegie Mellon University
Abstract Number: 759 Working Group: Urban Aerosols
Abstract The formation of new particles by homogeneous nucleation is an important source of ultrafine particles in many urban areas. Sulfur dioxide (SO2) and ammonia (NH3) emissions have been indicated as major precursors for nucleation-sourced ultrafine particles in the northeastern United States. Over the past few decades, emissions of SO2 and other air pollutant emissions from anthropogenic sources have been substantially reduced in the United States. However, the extent to which reduction in anthropogenic emissions alters the new particle formation events is largely undetermined. Here, we present observational evidence on how the reduction in anthropogenic emissions influence the frequency and intensity of nucleation events based on long-term comprehensive ambient measurements in the northeastern United States. We analyzed year-long particle size distributions measurements collected at an urban background site in Pittsburgh, Pennsylvania during 2001-02 (Pittsburgh Air Quality Study) and 2016-17 to explore any changes in trends in nucleation events in last 15 years. Our preliminary analysis results show that frequency of regional and local nucleation events and contribution of nucleation-sourced ultrafine particles are lower, and particle growth rates slower than those observed in 15 years ago. The changes are more pronounced during winter than warm seasons. Overall, our results indicate that with a substantial reduction in SO2 and NH3 emissions, the frequency and intensity of nucleation events are reduced in Pittsburgh, consistent with prior modeling study. The results from this study highlight that future reduction in SO2, NH3, and other anthropogenic emissions may considerably reduce the nucleation-sourced ultrafine particles burden in many polluted urban environments.