Measurements in a highly polluted Asian mega city: observations of aerosol number size distribution, modal parameters and nucleation events P. Mönkkönen1, I. K. Koponen1, K. E. J. Lehtinen1, K. Hämeri1,2, R. Uma3, and M. Kulmala1 1University of Helsinki, Department of Physical Sciences, Finland 2Finnish Institute of Occupational Health, Helsinki, Finland 3The Energy and Resources Institute (TERI), New Delhi, India
Abstract. Diurnal variation of number size distribution (particle size 3-800nm) and
modal parameters (geometric standard deviation, geometric mean diameter and
modal aerosol particle concentration) in a highly polluted urban environment
was investigated during October and November 2002 in New Delhi, India.
Continuous monitoring for more than two weeks with the time resolution of 10min
was conducted using a Differential Mobility Particle Sizer (twin
DMPS). The results indicated clear increase in Aitken mode (25-100nm)
particles during traffic peak hours, but towards the evenings there were
more Aitken mode particles compared to the mornings. Also high
concentrations of accumulation mode particles (>100nm) were detected in
the evenings only. In the evenings, biomass/refuse burning and cooking are
possible sources beside the traffic. We have also shown that nucleation
events are possible in this kind of atmosphere even though as clear
nucleation events as observed in rural sites could not be detected. The
formation rate of 3nm particles (J3) of the observed events varied from 3.3
to 13.9cm-3s-1 and the growth rate varied from 11.6 to 18.1nmh-1
showing rapid growth and high formation rate, which seems to be
typical in urban areas.
Citation: Mönkkönen, P., Koponen, I. K., Lehtinen, K. E. J., Hämeri, K., Uma, R., and Kulmala, M.: Measurements in a highly polluted Asian mega city: observations of aerosol number size distribution, modal parameters and nucleation events, Atmos. Chem. Phys., 5, 57-66, doi:10.5194/acp-5-57-2005, 2005.