10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Observational Evidence of Downdraft Clouds Contributing to Daytime Elevated Nitrate Concentration in an Urban Atmosphere
Jun Tao, Zhisheng Zhang, LEIMING ZHANG, Yunfei Wu, Junji Cao, Peng Cheng, Laiguo Chen, Renjian Zhang, South China Institute of Environmental Sciences
Abstract Number: 20 Working Group: Source Apportionment
Abstract Nitrate has become the most important hydrophilic chemical component in PM2.5 during serious air pollution periods in urban areas of Pearl River Delta (PRD) region of south China, but there is a lack of fully understanding of its formation mechanisms and controlling factors, especially during daytime nitrate episodes. To fill the knowledge gap, water-soluble inorganic ions in PM2.5 and trace gases including SO2, HNO3, NH3, NOx and O3, particle size distribution, vertical distribution of aerosol backscatter density, and selected meteorological factors were synchronously measured at high time resolution at an urban site in PRD. The remarkably enhanced nitrate mass concentration during daytime were identified to be caused by downdraft cloud processes and related cloud recycling and evaporating of atmospheric aerosols. Cloud downdrafts enhanced more of nitrate and ammonium than sulfate concentrations in ambient air, a finding that may have important implications on the sources of secondary inorganic aerosols in this and other similar cloudy regions.