Groundwater nitrate contamination: Factors and indicators

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Abstract

Identifying significant determinants of groundwater nitrate contamination is critical in order to define sensible agri-environmental indicators that support the design, enforcement, and monitoring of regulatory policies. We use data from approximately 1200 Austrian municipalities to provide a detailed statistical analysis of (1) the factors influencing groundwater nitrate contamination and (2) the predictive capacity of the Gross Nitrogen Balance, one of the most commonly used agri-environmental indicators. We find that the percentage of cropland in a given region correlates positively with nitrate concentration in groundwater. Additionally, environmental characteristics such as temperature and precipitation are important co-factors. Higher average temperatures result in lower nitrate contamination of groundwater, possibly due to increased evapotranspiration. Higher average precipitation dilutes nitrates in the soil, further reducing groundwater nitrate concentration. Finally, we assess whether the Gross Nitrogen Balance is a valid predictor of groundwater nitrate contamination. Our regression analysis reveals that the Gross Nitrogen Balance is a statistically significant predictor for nitrate contamination. We also show that its predictive power can be improved if we account for average regional precipitation. The Gross Nitrogen Balance predicts nitrate contamination in groundwater more precisely in regions with higher average precipitation.

Highlights

► We provide a statistical analysis of determinants of groundwater nitrate levels. ► We assess the capacity of the Gross Nitrogen Balance to predict nitrate levels. ► High average temperature and precipitation decrease groundwater nitrate levels. ► The Gross Nitrogen Balance is a stat. significant predictor for nitrate levels. ► Its capacity can be improved if precipitation is taken into account.

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Impact of changing land use practices on nitrate export by the Mississippi River

Christopher Kucharik, Simon D. Donner, Jonathan Foley (2004)

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Five years of nitrate removal, denitrification and carbon dynamics in a denitrification wall.

Louis Schipper, Maja Vojvodić-Vuković (2001)

Denitrification walls are a useful approach for removing nitrate from shallow groundwater, but little is known about the sustainability of nitrate removal, which is dependent on the continued supply of organic carbon to denitrifying bacteria. To address this question, we monitored nitrate removal, denitrification and carbon dynamics in a pilot-scale denitrification wall for 5 yr. The wall continuously removed more than 95% of the incoming nitrate in groundwater, which ranged from 5 to 15 mg N L(-1). We did not detect decreases in total carbon during the 5-yr study. Available carbon declined for the first 200 days after the wall was constructed but has since remained relatively constant. While microbial biomass has varied between 350 and 550 microg C g(-1) there was no downward trend, suggesting that carbon availability was not limiting the size of the microbial population. However, there was a large decrease in denitrifying population, as indicated by declines in denitrifying enzyme activity. Despite this decrease, denitrification rates have remained high enough to remove nitrate from groundwater and denitrification was limited by nitrate rather than by carbon. Our data demonstrates that there was sufficient available carbon in this denitrification wall to support denitrification and nitrate removal for at least 5 yr.