Influence of land use and change in the proportion of electron donors required for denitrification on N2O in groundwater

Nitrate (NO3-) and nitrous oxide (N2O) accumulate in groundwater in relation to human activities and pose multiple threats to the global environment (harming human health and atmospheric damage). This study focused on the evaluation of groundwater NO3-, N2O, and its indirect emission factor under different land use types (agricultural land, urban land, and forest) and response mechanism of major anions to dissolved N2O within groundwater in Dexing which has the largest copper mine in Asia. Specifically, this work used self-organizing maps (SOMs) to identify which anion conditions (NO3-, SO42-, F-, Cl-) and water quality parameters were suitable for the accumulation of groundwater N2O. Finally, we found that the shallow groundwater of agricultural land has a high concentration of NO3- and N2O and the agricultural activity has a significant effect on the temporal and spatial variation of N2O in groundwater. The result of SOMs combined with the positive correlation between N2O and NO3-/SO42- suggested that the electron donor required for denitrification has a significant effect on N2O accumulation. In this respect, when an increased proportion of reduced sulfur is available as an electron donor for autotrophic denitrification, this results in lower concentrations of N2O in groundwater. Through the comprehensive evaluation of the anion conditions and N2O in groundwater under different land use types, this study case can help to estimate the N2O indirect emission from groundwater, so as to constrain the global nitrogen budget.