Air pollution in Calcutta during winter - A three-year study

摘要

Air pollution becomes acute in Calcutta during winter. Pollutants cannot disperse easily, mainly due to inversion, low wind speed and high congestion. Although Calcutta is known to be one of the world's most polluted cities, available data on pollutant pollution are scanty. So far, data on suspended particulate matter (SPM), SO2, NOx in Calcutta for 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, heavy metals in inhalable particulate matter (IPM) and acidity of moisture. Samples were collected from five important street crossings in the core city. The average SPM concentrations during the winter in 1992, 1993 and 1994 were 982 mu g/m(3), 1007 mu g/m(3) and 1181 mu g/m(3) respectively. High SPM in the city air also showed high BSOM. High BSOM was associated with high value of PAH. Twelve PAH compounds were identified and quantified in the city air. Among the ten heavy metals determined, lead concentration in SPM during winter for Calcutta was high in comparison to other cities of the world. The total organolead concentrations in ambient air were measured and indicated high value of organolead in the city air. The average organolead concentration for 1992 1993 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 benzene 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 portion of the city dwellers, large number of registered and unregistered factories, poorly-maintained cars, poor quality of fuel bad condition of the city streets, small road area compared to the total city area, high population density, miserable slum conditions of habitation and overall poor socio-economic status of city dwellers are together responsible for the serious air pollution in the city. [References: 80]