Influence of coal-based thermal power plants on the spatial-temporal variability of tropospheric NO2 column over India

The oxides of nitrogen-NO (x) (NO and NO2)-are an important constituent of the troposphere. The availability of relatively higher spatial (0.25A degrees grid) and temporal (daily) resolution data from ozone monitoring instrument (OMI) onboard Aura helps us to better differentiate between the point sources such as thermal power plants from large cities and rural areas compared to previous sensors. The annual and seasonal (summer and winter) distributions shows very high mean tropospheric NO2 in specific pockets over India especially over the Indo-Gangetic plains (up to 14.2 x 10(15) molecules/cm(2)). These pockets correspond with the known locations of major thermal power plants. The tropospheric NO2 over India show a large seasonal variability that is also observed in the ground NO2 data. The multiple regression analysis show that the influence of a unit of power plant (in gigawatts) over tropospheric NO2 (x10(15) molecules/cm(2)) is around ten times compared to a unit of population (in millions) over India. The OMI data show that the NO2 increases by 0.794 +/- 0.12 (x10(15) molecules/cm(2); annual) per GW compared to a previous estimate of 0.014 (x10(15) molecules/cm(2)) over India. The increase of tropospheric NO2 per gigawatt is found to be 1.088 +/- 0.18, 0.898 +/- 0.14, and 0.395 +/- 0.13 (x10(15) molecules/cm(2)) during winter, summer, and monsoon seasons, respectively. The strong seasonal variation is attributed to the enhancement or suppression of NO2 due to various controlling factors which is discussed here. The recent increasing trend (2005-2007) over rural thermal power plants pockets like Agori and Korba is due to recent large capacity additions in these regions.