Indicators of groundwater potential for nitrate transformation in a reductive environment

Abstract

Increasing nitrate concentration in many shallow aquifers has become a global environmental problem. In order to determine anoxic aquifer sensitivity to nitrate pollution and potential for nitrogen conservation, we have qualified potential nitrate transformation pathways, by conducting field tests, tracer study, physicochemical and microbiological analysis of the groundwater. Combination of in situ measuring and laboratory analysis of physicochemical properties and selected biological activity reactivity tests (BART™), has enabled estimation of different pathways of NO3- reduction. During five days of nitrate enrichment experiment there was no observed increase in NO3- concentration, nor any observed decrease of TN (total nitrogen) in the groundwater, while NH4+ production rates increased (with the peak concentrations of 4.97 mg N/L) on the first day of the experiment. We assume that inhibited respiratory denitrification and enhanced DNRA (dissimilatory reduction of nitrate to ammonium) may preserve available nitrogen in a bioavailable form of ammonium.