Wet deposition fluxes of atmospheric inorganic reactive nitrogen at an urban and rural site in the Indo-Gangetic Plain

Özet

Excess nitrogen deposition is a matter of concern for sensitive ecosystems. However, understanding the sources and transport of Nr species has been a challenge due to limited observations of atmospheric deposition of the key Nr species across India. In this study, wet deposition of atmospheric inorganic Nr species was investigated during the year 2013 at tworegionally representative sites: Delhi (an urban site) and Jaunpur (a rural site). These sites are located in the Indo-Gangetic Plain (IGP) region, which is one of the most populatedand fertile regions ofIndia.The averageNH4 þconcentrations in rainwaterwere found to be 25.4 meql1 and 98.5 meql1 at the rural and urban sites, respectively, whereas average NO3 concentrations were 12.4 meql1 and 28.7 meql1 at the rural and urban sites (respectively). The annual average wet deposition fluxes of NH4 þ and NO3 at Delhi were calculated as 10.45 and 3.05 kgN ha1 yr1 respectively, whereas at Jaunpur the fluxes were 3.19 and 1.56 kgN ha1 yr1 respectively. In order to assess the Nr deposition, our estimates showed 486% increase in NO3 (from 0.52 to 3.05 kgN ha1 yr1) while 283% NH4 þ (2.72e10.44 kgN ha1 yr1) between 1994 and 2013 at Delhi, clearly indicating the effect of urbanization and Land Use Land Cover (LULC) change. Reduced versus oxidized N deposition contribution was also estimated. This study provides key quantitative information to support regional nitrogen budget estimates in south Asia.