Simultaneous Measurements of Ambient NH 3 and Its Relationship with Other Trace Gases, PM 2.5 and Meteorological Parameters over Delhi, India

In the present study, trace gases (NH3, NOx, CO and SO2), PM2.5 and meteorological parameters were carried out at 5 different monitoring sites [CSIR-National Physical Laboratory, New Delhi and other 4 air quality measurements (AQMS) sites (Anand Vihar, Mandir Marg, Punjabi Bagh and R.K. Puram) of Delhi Pollution Control Committee (DPCC)] of megacity Delhi, India, from January 2013 to December 2015 to estimate the spatio-temporal variation of pollutants over Delhi. The results showed large spatial and seasonal variations in mixing ratios of ambient trace gases and PM2.5 concentration over Delhi. The average mixing ratios of NH3, NO, NO2, CO and SO2 were 53.4 ± 14.9 ppb, 42.0 ± 14.6 ppb, 39.6 ± 13.0 ppb, 1.9 ± 0.4 ppm and 4.3 ± 1.0 ppb, respectively, whereas average concentration of PM2.5 was 136.2 ± 49.6 µg m−3 during the entire study period. All the trace gases and PM2.5 showed maxima during winter season followed by summer and monsoon seasons at all the sites. The 24-h average mixing ratios of the trace gases (NH3, NO, NO2, CO and SO2) and PM2.5 were recorded higher when compared with other sites of the country. The concentration of PM2.5 is breaching the prescribed standard limit of National Ambient Air Quality Standards (NAAQS) of India.