Nitrate pollution of groundwater

Nitrate pollution is widely recognized as one of the main issues in both rural and urban aquifers, especially in developing countries. In these regions the main contamination sources of nitrates are generally associated to diffuse pollution (due to fertilizers and manure use in agricultural practices), and point source pollution resulting from lacking (or inadequate) sanitation systems. As a result these groundwater often exceed the statutory limit for drinking water (50 mg/L; WHO, 2011) with possible severe consequences on human health and food production.

This is why the clear recognition of nitrate origin is of paramount importance in order to support the correct implementation of long-term management strategies for groundwater protection. In this regards, nitrate isotopes has proven to be a powerful tool for  the identification of nitrate pollution sources.

Within Bir Al-Nas the application of nitrate isotopes to identify the sources of dissolved nitrates in the Grombalia Aquifer is one of the key activities to prevent groundwater from further contamination and reduce the risks associated with public health and food security in the region.
This area is in fact characterized by high (and increasing) nitrate concentrations in groundwater, possibly associated to the widespread use  of fertilizers and manures in the agricultural zone.

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Example of possible nitrate pollution sources in rural areas (Grombalia; Photo V. Re, 2014)

While a complete assessment on nitrate pollution origin is ongoing, this week we had the opportunity to host two experts on nitrate isotopes investigations and analysis:  Dr. Elisa Sacchi (University of Pavia, Italy) and Dr. Enrico Allais (ISO4 Laboratory, Torino, Italy).
During their visit at ENIS, Dr. Sacchi and Dr. Allais illustrated to the ENIS-LRAE students and technicians the principles and laboratory techniques for samples preparation for δ15N_NO3 and δ18O_NO3 analysis.

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Also, during the last day of their visit, Dr. Sacchi gave a lecture on the “Use of stable isotopes to identify origin, transport and removal of dissolved nitrates in groundwater” to the third year Environmental Engineering Students of ENIS and LRAE staff.
The lecture was really appreciated by the audience, especially given the relevance of isotopic techniques applied to pollution control and management.

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In the next months we will equip the LRAE laboratory with the necessary materials for samples preparation prior isotopic analysis to be performed at the ISO4 private laboratory in Italy. This represents an additional step for a closer collaboration between the Tunisian and Italian laboratories.

Photo: Re V. 2014

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