Modelling 10-year trends of PM10 and related toxic heavy metal concentrations in four cities in India.

Ambient concentrations of PM(10) were measured weekly twice at 3 sites in Delhi, Mumbai, Kolkata and Chennai during 1998-2007. Concentrations of heavy metals Cd, Zn, Ni, Fe, Pb and Cr have been analyzed once in every month. Trend analyses of PM(10) and heavy metals of four mega cities, indicate that PM(10) and heavy metals show decreasing trend. The statistical tests applied for this purpose i.e., t-test adjusted for seasonality and SK test, provide similar conclusions. The inferences obtained are that at two sites in Mumbai, PM(10) levels have shown improvement at the rate of 2 and 3 microg m(-3) yr(-1); in Chennai, PM(10) levels have decreased at the rate of 2.5, 2 and 5 microg m(-3) yr(-1) during the period 1998-2007. In Delhi, Ni, Fe and Pb levels declined at the rate of 1, 29 and 12 ng m(-3) yr(-1); in Mumbai Zn, Ni, Fe and Cr have decreased at the rate of 51, 2, 62 and 0.7 ng m(-3) yr(-1); in Kolkata, the levels of Ni, Pb and Cr declined at the rate of 2, 11 and 1 ng m(-3) yr(-1); and in Chennai Ni, Fe and Cr have shown improvement at the rate of 1, 38 and 1 ng m(-3) yr(-1) in this period. During the last 10 years, many interventions have been undertaken such as, changes in fuel quality, better vehicle technologies, improved industrial fuel mix, shifting of industries outside the city limits, resulting in improvement of urban air quality. 2010 Elsevier B.V. All rights reserved.