Measurements in a highly polluted Asian mega city: observations of aerosol number size distribution, modal parameters and nucleation events

[摘要] Diurnal variation of number size distribution (particle size 3-800nm) andmodal parameters (geometric standard deviation, geometric mean diameter andmodal aerosol particle concentration) in a highly polluted urban environmentwas investigated during October and November 2002 in New Delhi, India.Continuous monitoring for more than two weeks with the time resolution of 10minwas conducted using a Differential Mobility Particle Sizer (twinDMPS). The results indicated clear increase in Aitken mode (25-100nm)particles during traffic peak hours, but towards the evenings there weremore Aitken mode particles compared to the mornings. Also highconcentrations of accumulation mode particles (>100nm) were detected inthe evenings only. In the evenings, biomass/refuse burning and cooking arepossible sources beside the traffic. We have also shown that nucleationevents are possible in this kind of atmosphere even though as clearnucleation events as observed in rural sites could not be detected. Theformation rate of 3nm particles (J3) of the observed events varied from 3.3to 13.9cm^-3s^-1 and the growth rate varied from 11.6 to 18.1nmh^-1showing rapid growth and high formation rate, which seems to betypical in urban areas.

[学科分类] 大气科学