Observational study of influence of aerosol hygroscopic growth on scattering coefficient over rural area near Beijing mega-city
- 1Chinese Academy of Meteorological Science, China Meteorological Administration, Beijing, China
- 2Nansen-Zhu International Research Centre, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
- 3Graduate University of Chinese Academy of Sciences, Beijing, China
Abstract. We investigated aerosol hygroscopic growth property and its influence on scattering coefficient using M9003 nephelometers in coupling with humidity controlled inlet system at a rural site near Beijing mega-city from 24 April to 15 May 2006. Inlet relative humidity was controlled in an increasing range of 40%–90% while aerosol hygroscopic growth factor of scattering coefficient, f(RH=80%) as ratio of scattering coefficient at RH=80% to "dry" scattering coefficient (RH<40%) varied in a range of 1.07–2.35 during the measurement. Further analysis indicated that under dust episode, measured f(RH=80%) is 1.2±0.02, and estimated periodic mean value of f(RH=80%) was 1.31±0.03 under clean periods; during urban pollution periods, the aerosol displayed relative strong water absorbing properties with f(RH=80%) of about 1.57±0.02. An examination of chemical composition of daily filter samples highlighted that aerosol hygroscopicity was generally depressed with the increasing ratio of organic matter (OMC)/ammonium sulfate (AS) in particle mass, similar with the results of many previous studies. However, a special case with high value of f(RH=80%)=2.21 and high OMC/AS ratio was also observed, this exception reflected physico-chemical particularities of organic matter and its complex interaction with other compounds during this episode.