Simultaneous measurements of SO2, NO2, HNO3 and NH3: seasonal and spatial variations

摘要

This communication presents simultaneous measurements of atmospheric concentration of gaseous SO2, NO2, HNO3 and NH3 at Dayalbagh, a suburban site and at St. John's, an urban site at Agra (India). The concentration Of SO2, NO2, HNO3 and NH3 in vapour phase is 3.5 +/- 1.4, 5.4 +/- 1.5, 1.5 +/- 0.8 and 10.5 +/- 2.4 mum(-3) respectively at Dayalbagh, while at St John's corresponding values are 4.1 +/- 1.2, 8.6 +/- 1.8, 2.4 +/- 1.0 and 6.6 +/- 1.8 mum(-3), respectively. The high concentration Of SO2, NO2 and HNO3 at the St. John's site may be due to industries nearby and high vehicular traffic, while high concentration of NH3 at the Dayalbagh site may be due to the stockyard nearby and also agricultural practices. Seasonally, SO2 and NO2 showed highest concentration in winter and lowest during the monsoon. This is because of high fuel usage during winter and trapping of the pollutants in the boundary layer due to frequent temperature inversions. HNO3 showed highest concentration in summer, probably due to intense solar radiation and increased photochemical activity, followed by monsoon and winter. NH3 showed highest values during the monsoon and lowest during the winter. The high concentration during monsoon may be due to more vegetation and favourable conditions for microbial activity.