Aerosol mass measurements made using Andersen cascade impactor at different
locations in an urban area were used to study the variation in power-law e
xponent in the Junge-type number distribution. The discrete mass size data
were inverted by modified Twomey algorithm to obtain continuous mass size d
istribution from which number distributions were derived. These were used f
or evaluating actinic fluxes and hence NO2 photolysis rate constants employ
ing a radiative transfer model with delta-Eddington approximation.
Results of the spatial variation of Junge power-law exponent over the urban
region are presented. The relative magnitude of photolysis rate constants
over regions with differing aerosol emission characteristics are illustrate
d Parametric studies indicated the importance of considering fractional ele
mental carbon content of the aerosols in the atmosphere. Results of a limit
ed validation study of the model are also presented using quartz crystal mi
crobalance impactor data at one of the sites. (C) 1999 Elsevier Science Ltd
. All rights reserved.