Spatial patterns of air pollution in the Delhi Metropolitan Region

In the present study hourly air pollution data for major pollutants including NO2, SO2, and O3 from five pollution monitoring stations within Delhi Metropolitan Region (DMR) were collected for 2011-2013. These seven stations maintained by the local pollution control board , are representative of the major categories of land uses that exist in the DMR, consisting of residential and industrial areas. The analyses were conducted at the seasonal scale in view of substantial seasonal level differences in atmospheric conditions during a year, mainly attributable to its inland location in the Indian subcontinent as well as rapidly increasing population accompanied with changes in land use. The seasonal classification used for the present study are winter season (January to March), dry summer season (April to June), wet monsoon season (July to September), and retreating/northeast monsoon season (October to December). The global standards for air pollution were used to determine the number of days exceeding the acceptable standards for different air pollutants. The results of the study indicate substantial spatial variations in levels of air pollution not only at the seasonal scale but also at the local spatial scale. The spatial patterns of air pollution were closely related to the prevailing land use at a particular site as well as the weather conditions. For instance, northern and eastern parts of DMR have relatively higher concentration of industrial activities, with high levels of emissions from some of the manufacturing units. The pollutants being generated in some of these industrial sites are also transported to other parts of DMR leading to substantially higher pollution levels in adjacent residential areas. The results of this study are important, mainly in view of significant health impacts rising pollution levels can cause on the local population.