The monograph describes the concentrations of ambient NH3 and other trace gases (NO, NO2, SO2, O3 and CO) and its interaction over Delhi, NCR, IGP, Himalayan region and Bay of Bengal of India. The average concentrations of ambient NH3, NO, NO2, SO2 and CO were recorded as 21. 2 ± 5. 4 ppb, 19. 5 ± 4. 9 ppb, 17. 4 ± 1. 4 ppb, 1. 7 ± 0. 5 ppb and 1. 6 ± 0. 7 ppm respectively during winter, whereas the average concentrations of ambient NH3, NO, NO2, SO2 and CO were recorded as 20. 8 ± 4. 7 ppb, 21. 7 ± 6. 3 ppb, 16. 8 ± 3. 1 ppb, 2. 2 ± 0. 8 ppb and 1. 8 ± 0. 9 ppm respectively during summer at Delhi. The results emphasized that the traffic could be one of the significant sources of ambient NH3 at the urban site of Delhi as illustrated by positive correlations of NH3 with traffic related pollutants (NO, NO2 and CO). Surface wind analysis and wind directions also support the road side traffic and agricultural activities at the nearby area indicating possible major sources of ambient NH3 at the study site. NH3 emission from rice-wheat cropping system of subtropical agricultural soil of Delhi, India has also been demostrated. About 9% of the applied N was lost as NH3 during the rice and wheat crops
