Investigating the potential of dissolved organic matter (DOM) induced denitrification in Dutch groundwater

This research aimed to investigate the potential of dissolved organic matter (DOM) induced denitrification in groundwater. Groundwater was collected from various locations across the Netherlands and laboratory experiments assessed groundwater denitrification potential by measuring NO3, NO2, NH4 and DOC during a 60 day incubation. Organic matter characteristics were evaluated using spectroscopic and fractionation methods. Results show potential for DOM induced denitrification in Dutch groundwater but it remains unclear how DOM is utilized in this process. Partial oxidation and HS moieties with electron donating capacities could be supplying electrons but other NO3 removal processes such as assimilation into biomass can also play a role. It was attempted to identify relationships between organic matter characteristics and the observed NO3 removal but no clear correlation was found. It has been suggested that the presence of hydrophilic compounds such as carbohydrates, organic acids and proteins enhance the biodegradability of DOM. This relationship was not found between the hydrophilic fractions of DOM and the observed NO3 removal. Analytical techniques used were also unable to identify variations in groundwater samples that correlated to land use or depth. Analytical techniques characterizing the molecular structure of DOM are possibly more adequate to link DOM to its origin.