A New in Situ Method for Tracing Denitrification in Riparian Groundwater.

The spatiotemporal dynamics of denitrification in groundwater are still not well-understood because of a lack of efficient methods to quantify this biogeochemical reaction pathway. Previous research used the ratio of N to argon (Ar) to quantify net production of N via denitrification by separating the biologically generated N component from the atmospheric-generated components. However, this method does not allow the quantification of the atmospheric components accurately because the differences in gas partitioning between N and Ar are being neglected.

Continuous Measurements of Dissolved Ne, Ar, Kr, and Xe Ratios with a Field-Deployable Gas Equilibration Mass Spectrometer.

Noble gases dissolved in natural waters are useful tracers for quantifying physical processes. Here, we describe a field-deployable gas equilibration mass spectrometer (GEMS) that provides continuous, real-time measurements of Ne, Ar, Kr, and Xe mole ratios in natural waters. Gas is equilibrated with a membrane contactor cartridge and measured with a quadrupole mass spectrometer, after in-line purification with reactive metal alloy getters.