The use of nitrate isotopes to assess agricultural and domestic impacts on groundwater quality in rural zones. The example of Grombalia basin (Tunisia).

In recent years, the increased groundwater withdrawal for agricultural practices coupled with the widespread use of natural and synthetic fertilizers has affected both groundwater quality and quantity in the Grombalia Plain (Tunisia). In particular, the region is experiencing an increase in nitrate concentration that can have severe effects on human health and food security. In order to identify the origin of groundwater pollution a survey on 48 wells was conducted in between February and March 2014, as the first step for a complete nitrate vulnerability assessment of the region. In most of the investigated sites nitrates exceeds the drinking water limits and the isotopic and hydrogeochemical investigation associated their origin to agricultural and domestic inputs. The occurrence of denitrification processes has been highlighted, suggesting the potential for self-remediation of the contaminated waters.