AIR-POLLUTION IN CALCUTTA DURING WINTER - A 3-YEAR STUDY

Air pollution becomes acute in Calcutta during winter. Pollutants cann ot disperse easily, mainly due to inversion, low wind speed and high c ongestion. Although Calcutta is known to be one of the world's most po lluted cities, available data on pollutant pollution are scanty. So fa r, data on suspended particulate matter (SPM), SO2, NOx in Calcutta fo r a couple of years are available. Relatively small amount of data are available on other parameters like CO, benzene soluble organic matter (BSOM), heavy metals, polynuclear aromatic hydrocarbon (PAH). Almost no data are available on benzene-toluene-xylene (BTX), organolead, hea vy metals in inhalable particulate matter (IPM) and acidity of moistur e.Samples were collected from five important street crossings in the c ore city. The average SPM concentrations during the winter in 1992, 19 93 and 1994 were 982 mu g/m(3), 1007 mu g/m(3) and 1181 mu g/m(3) resp ectively. High SPM in the city air also showed high BSOM. High BSOM wa s associated with high value of PAH. Twelve PAH compounds were identif ied and quantified in the city air. Among the ten heavy metals determi ned, lead concentration in SPM during winter for Calcutta was high in comparison to other cities of the world. The total organolead concentr ations in ambient air were measured and indicated high value of organo lead in the city air. The average organolead concentration for 1992 19 93 and 1994 were 303 ng/m(3), 299 ng/m(3) and 296 ng/m(3) respectively . Concentrations of benzene, toluene and xylene were found to be much higher than in other studies elsewhere in the world. The average benze ne concentration during winter in 1992, 1993 and 1994 were 1004 mu g/m (3), 7082 mu g/m(3) mu g/m(3) and 491 mu g/m(3) respectively. Various factors like use of kerosene and coal as cooking fuel by a large porti on of the city dwellers, large number of registered and unregistered f actories, poorly-maintained cars, poor quality of fuel bad condition o f the city streets, small road area compared to the total city area, h igh population density, miserable slum conditions of habitation and ov erall poor socio-economic status of city dwellers are together respons ible for the serious air pollution in the city.