Assessment of excess N2 for quantifying actual denitrification in NZ groundwater systems

Denitrification in groundwaters is a key nitrate (NO3) attenuation process, where leached NO3 can be reduced to gaseous forms of nitrogen (N2). In this study, calculation of the concentration of excess N2 is applied to the New Zealand context to quanitfy the extent of denitrification occurring in groundwater systems under natural flow conditions. The concentration of dissolved atmospheric N2, according to the recharge conditions of the water, can be established by the measurement of two noble gases that are also part of the atmosphere. This enables differntiation of the excess N2 gas produced via denitrification reactions from atmospherically derived N2 gas.