Abstract

The capital of Karnataka "Bengaluru" located in the Southern part of India is still facing challenges due to atmospheric pollution. The levels are still very high over the city compared to national and international standards due to vehicular emissions. The ambient gaseous pollutants as O3, CH4, NMHC, CO, NH3, NO, NO2 and SO2 were assessed over Bengaluru since 1st January 2017 to 20th March 2018. The daily average concentrations of O3, CH4, NMHC, CO, NH3, NO, NO2 and SO2 were 35.0 ± 17.50 ppb, 412.8 ± 259 ppm, 1.1 ± 1.1ppb, 0.7 ± 3.1 ppm, 28.8 ± 15.7 ppb, 7.2± 3.1ppb, 27.5 ± 8.4 ppb and 4.8 ± 1.6 ppb, respectively. The methane values were greater during the post-monsoon season (643 ppb) followed-by winter (488.4 ppb), monsoon (333.0 ppb) and summer (286.3 ppb). However, the NMHC was highest in the summer followed by the winter (1.3 ppb), monsoon (0.5 ppb) and post-monsoon seasons (0.4 ppb). Diurnally, fast production of surface ozone (highest: +8.01 ppb h−1) was observed in between 8:00 and 12:00 hours LT because of freshly emitted precursors and photochemical reaction in this period. In evening (in between 17:00 and 19:00 hours LT), it was opposite and fast destruction of surface ozone (-7.82 ppb h-1) because of the lower production of oxides of nitrogen. The study has indicated the reverse diurnal pattern with lowest NO, NO2 and CO concentration when ozone showed the highest Peak indicating the precursor gases for ozone. To enhance the quality of air, the control strategies must be adopted to diminish the emission from source regions.

Keywords: Diurnal; Seasonal; Ozone; Precursor gases; Boundary Layer Height