Wet deposition of total nitrogen, dissolved organic carbon and heavy metals investigating role of long-range transport at two sites in Delhi

Precipitation is one of the significant phenomena for deposition of nitrogen, carbon and metal fractions. In the current study, Total Nitrogen (TN), Dissolved Organic Carbon (DOC) and metal concentrations were measured at two sites having distinct land use patterns in Delhi National Capital Region during different seasons in 2018 and 2019 to find out their potential sources. The TN mean concentration was found to be 16.0 mg/l and 7.0 mg/l at DG and JN site respectively. Whereas the DOC mean concentration was found to be 3.8 mg/l and 2.5 mg/l at DG and JN site respectively. The sequence for the metal concentrations was recorded as Ca > Na > Mg >K> Al  > Cu > Fe > Mn > Zn > As for DG site whereas at JN site we recorded different sequence i.e., Ca > Al > Na > K > Mg > Fe > Mn > Zn > Cu > As. Different sources can be attributed to the influence of anthropogenic activities (agriculture, animal husbandry) on nitrogenous species, and biomass burning on dissolved organic carbon species. The wind rose plots indicated that the local and regional sources located in the south-eastern and north-western direction from the sites influenced the wet deposition of the species. Air-mass back trajectory analysis implied the influence of air masses originating from the Bay of Bengal during monsoon season while that of air masses originating from Haryana, Punjab and further north-west during winter season. Presently, very limited information is available on TN and DOC linking with heavy metals. The current study will be filling such gaps to further help nitrogen and carbon budgeting and linking nitrogen with climate change. The study has policy implications as well for north-central India especially for identifying and controlling local, trans-boundary and distance emission sources. The findings facilitate us to understand a holistic view of chemical composition of precipitation so that effective mitigation measures can be taken accordingly.