Emission estimates of particulate matter and heavy metals from mobile sources in Delhi (India).

An attempt has been made to make a comprehensive emission inventory of particulate matter (PM) of various size fractions and also of heavy metals (HMs) emitted from mobile sources (both exhaust and non-exhaust) from the road transport of Delhi, India (1991-2006). COPERT-III and 4 models were mainly used toestimate these emissions. Results show that the annual exhaust emission of PM of size upto 2.5 micrometer (PM2.5) has increased from 3Gg to 4.5Gg during 1991-2006 irrespective of'improvement in vehicle-technology and fuel use. PM emission from exhaust and non-exhaust sources in general has increased. Heavy commercial vehicles-need attention to control particulate emission as it emerged as a predominant source of PM emissions. Among non-exhaust emissions of total suspended particulate matter (TSP), road-surface wear (49%) has the prime contribution. As a result of-introduction of unleaded gasoline Pb has significantly reduced (8 fold) whereas share of Cu and Zn are still considerable. Among non-exhaust sources, Pb release was the most significant one from tyre-wear whereas from break-wear, Cu release was found to be the most significant followed by Pb and Cr + Zn. Because of public health concerns further policies need to be developed to reduce emissions of PM and HMs from the road transport of megacity Delhi.