Measurement of Ambient NH3, NO and NO2 at an Urban Area of Kolkata, India

Abstract

Mixing ratios of ambient NH3, NO and NO2 were measured in campaign mode at Kolkata a megacity of Indo-Gangetic plain of India to study the diurnal variation and mixing ratios of NH3, NO and NO2 during 24–27 February 2012. The present study has been carried out on campaign based measurement of mixing ratios of NH3, NO and NO2 for short period of time at Kolkata represent the indicative values over the region. The average mixing ratios of ambient NH3, NO and NO2 were recorded as 43.4 ± 7.0 ppb, 46.0 ± 8.7 ppb and 31.9 ± 5.5 ppb at Kolkata. In the present case, significant diurnal variation of NH3, NO and NO2 were recorded at Kolkata during study. Mixing ratio of ambient NH3 reaches its maxima (78.9 ppb) at night and minimum during daytime. Result reveals that the ambient NH3 mixing ratio is positively correlated with ambient NO (r 2 = 0.395) and NO2 (r 2 = 0.404) mixing ratio and significant negatively correlated with ambient temperature (r 2 = –0.669). Surface wind direction and wind speed analysis indicates that the local acitivities (livestock, drainage, agriculture, vehicles etc.,) may be the possible sources of ambient NH3 at the observational site of Kolkata.