This study investigates nitrogen cycling in groundwater from an agricultural area using organic fertilizer. The research combines isotope and microbial studies to track transformations. High-nitrate samples were incubated with a low addition of ¹⁵N tracer. Results showed a shift from archaeal nitrification to bacterial denitrification under low oxygen with glucose, confirmed by isotope and microbial analyses. The findings offer insights for improving water quality and pollution management.

In this work, we show the evidences of anaerobic activity of nitrogen-processing microorganisms that naturally occurred in outcropped organic-rich sediments as Miocene lignites. The results presented in this paper indicate the important role of nitrogen supply processes in environments depleted in this element and at the same time rich in humic substances, such as peat bogs, wetlands, immature sediments containing organic carbon (e.g. gyttja, fossil wood, coal).

Greenhouse gases are produced and consumed via a number of pathways. Quantifying these pathways helps reduce the climate and environmental footprint of anthropogenic activities. The contribution of the pathways can be estimated from the isotopic composition, which acts as a fingerprint for these pathways. We have developed the Time-resolved FRactionation And Mixing Evaluation (TimeFRAME) model to simplify interpretation and estimate the contribution of different pathways and their uncertainty.

This is the first experimental setup combining a complex set of methods (microbial inhibitors and isotopic approaches) to differentiate between N₂O produced by fungi or bacteria during denitrification in three soils. Quantifying the fungal fraction with inhibitors was not successful due to large amounts of uninhibited N₂O production. All successful methods suggested a small or missing fungal contribution. Artefacts occurring with microbial inhibition to determine N₂O fluxes are discussed.

We present the first validation of N₂O isotopic approaches for estimating N₂O source pathways and N₂O reduction. These approaches are widely used for tracing soil nitrogen cycling, but the results of these estimations are very uncertain. Here we report the results from parallel treatments allowing for precise validation of these approaches, and we propose the best strategies for results interpretation, including the new idea of an isotope model integrating three isotopic signatures of N₂O.