Measurements and analysis of criteria pollutants in New Delhi, India

Abstract

Ambient concentrations of carbon monoxide (CO), nitrogen oxides (NO x ), sulfur dioxide (SO 2), and total suspended particulates (TSP) were measured from January 1997 to November 1998 in the center of downtown [the Income Tax Office (ITO) located on B.S.G. Marg] New Delhi, India. The data consist of 24-h averages of SO 2, NO x , and TSP as well as 8 and 24-h averages of CO. The measurements were made in an effort to characterize air pollution in the urban environment of New Delhi and assist in the development of an air quality index. The yearly average CO, NO x , SO 2, and TSP concentrations for 1997 and 1998 were found to be 4810±2287 and 5772±2116 μg/m 3, 83±35 and 64±22 μg/m 3, 20±8 and 23±7 μg/m 3, and 409±110 and 365±100 μg/m 3, respectively. In general, the maximum CO, SO 2, NO x , and TSP values occurred during the winter with minimum values occurring during the summer, which can be attributed to a combination of meteorological conditions and photochemical activity in the region. The ratio of CO/NO x (∼50) indicates that mobile sources are the predominant contributors for these two compounds in the urban air pollution problem in New Delhi. The ratio of SO 2/NO x (∼0.6) indicates that point sources are contributing to SO 2 pollution in the city. The averaged background CO concentrations in New Delhi were also calculated (∼1939 μg/m 3) which exceed those for Eastern USA (∼500 μg/m 3). Further, all measured concentrations exceeded the US National Ambient Air Quality Standards (NAAQS) except for SO 2. TSP was identified as exceeding the standard on the most frequent basis.