Characterization of Trace Gases and Green House Gas in Megacity New Delhi

Air pollution and climate change is serious environmental concern due to its visible negative impact on human health. Around 14 Indian cities are placed among top 20 most polluted cities of the world. Trace gas like O3, NOx, CO and CO2 are important pollutants which is associated with human health, climate change and adverse effect on growth and yield of crops. Stratospheric O3 absorbs ultraviolet light and prevents it from reaching to the ground. Greenhouse effect of O3 and CO2 is prominent, O3 in upper troposphere and ranked 3rd for its radiative potential after the carbon dioxide and methane. The amount of O3 generated by photochemical reaction of air pollutants is much larger than the inflow from the stratosphere. This is indicating that trace gases and GHG are generated by anthropogenic activities. It is significantly high in urban area like megacity Delhi as compared to rural area due to excessive anthropogenic activity. The ground level measurements of surface trace gas like O3, NOx, CO and CO2 were conducted in Delhi-Mathura road near traffic intersection for year 2017, January to December. The daily mean concentration of O3, NOx, CO and CO2 were 23.11±17.26ppb (range 58.38 to 6.42ppb), 26.41±4.24ppb (ranges 48.14 to 24.09ppb), 1.56±4.24ppm (ranges 6.6 to 0.69ppm) and 342.54±33.49 (ranges 508.23 to 323.33ppm), respectively. The mixing ratios of O3 were highest of 32ppbv and lowest 17ppbv during the pre-monsoon and monsoon seasons, respectively. While the mixing ratios of both CO and NOx showed highest and lowest values during the winter and monsoon seasons, respectively. The analysis concluded seasonality of O3, CO and NOx were also governed by the long-range transport, mainly with the summer and winter monsoon circulations over the Indian subcontinent. The mixing ratios of CO and NOx show strong correlations during winter and pre-monsoon seasons, while poor correlation in the monsoon season. The mixing ratios of CO and NOx decreased with the increase in wind speed, while O3 tended to increase with the wind speed