Comparative study of line source models for estimating lead levels due to vehicular traffic in Delhi

Studies concerning the concentration of lead (Pb) in Delhi due to vehicular traffic are being conducted under sponsorship of Ministry of Environment and Forests, Government of India. The comparison of results of two line source models based on Gaussian formulation are made with observed lead values at 13 busy intersections in Delhi. Results have been obtained based on predicted emission rates of lead from vehicular traffic over next 10 years. Each year the number of vehicles has increased e.g. it has doubled during the: last 5 years. Two types of studies have been made: i) Hourly lead concentrations due to vehicular traffic in Delhi have been computed using two analytical line source models (IIT and ISCST) are based on the Gaussian plume approach. ii) Monthly average lead concentrations for the period 1985-2000 have been computed by use of the Climatological Dispersion Model (CDM) and the Industrial Source Complex Long Term (ISCLT) model, both of which are U.S. operational models. Models results show that three- monthly averaged Pb levels due to an increasing trend in vehicular traffic in Delhi sometimes exceed the US EPA standard (i.e., 1500 ng m(-3), Federal Register (US EPA) 1971, 1978). Because, there is no Indian standard for ambient concentration of lead, Hence the USEPA standard was used. Accordingly, a strategy needs to be developed for reducing lead emissions from the rapidly increasing vehicular traffic, which is the main source of Pb emissions. Information about vehicular traffic in Delhi over next 10 years indicates that the Government of India needs to introduce appropriate control measures on the emission of lead.