Measurement of Ambient Ammonia over the National Capital Region of Delhi, India

Abstract

Mixing ratio of ambient ammonia (NH3) was measured at various locations of the National Capital Region (NCR) of Delhi, India using a NH3-analyzer during January 2010 to June 2012 in campaign mode. The present study has been carried out on campaign based measurement of mixing ratios of NH3 and NOx for short period of time over the NCR of Delhi represent the indicative values over the region. The average mixing ratio of ambient NH3 was 20.9 ± 1.6 ppb during the period. The maximum average mixing ratio of ambient NH3 (28.8 ± 3.0 ppb) was recorded in an industrial area surrounded by intensive vehicular traffic followed by an agricultural farm (27.5 ± 2.1 ppb), whereas the minimum (6.4 ± 1.2 ppb) was recorded in the semi-urban area. The diurnal trend of NH3 depended on the ambient temperature at most of the sites and was affected by wind direction. Ambient NH3 was correlated with the NOx mixing ratio suggesting that the vehicular emission may be one of the sources of ambient NH3 in the NCR of Delhi. However, long-term measurements of ambient NH3 and their precursors will lead to seasonal variation of source apportionment over the NCR, Delhi, India.