Abstract
Groundwater nitrate contamination is a source of rising concern that has been faced through the introduction of several regulations in different countries. However the methodologies used in the definition of Nitrate Vulnerable Zones are not included in the regulations. The aim of this work was to compare different methodologies, used to asses groundwater nitrate contamination risks, based on parametric systems or simulation modelling. The work was carried out in Piedmont, Italy, in an area characterised by intensive animal husbandry, high N load, a shallow water table and a coarse type of sub-soil sediments. Only N loads from agricultural non-point sources were considered. Different methodologies with different level of information have been compared to determine the groundwater nitrate contamination risk assessment: N load, IPNOA index, the intrinsic contamination risk from nitrates, leached N and N concentration of the soil solution estimated by the simulation model. The good correlation between the IPNOA index and the intrinsic nitrate contamination risk revealed that the parameters that describe the soil in this area did not lead to a different classification of the parcels. The intrinsic nitrate contamination risk was greatly influenced by N fertilisation, however the effect of the soils increased the variability in comparison to the IPNOA index. The leached N and N concentration in the leaching were closely correlated. The dilution effect of percolated water was almost negligible. Both methodologies were slightly correlated to the N fertilisation and the two indexes. The correlations related to the intrinsic nitrate contamination risk was higher than those related to IPNOA, and this means that the effect of taking into account soil parameters increases the correlation to the prediction of the simulation model.
Highlights
Nitrate contamination of the groundwater throughout the world is a source of rising concern that has been faced through the introduction of several regulations in different countries
The correlations related to the intrinsic nitrate contamination risk was higher than those related to IPNOA, and this means that the effect of taking into account soil parameters increases the correlation to the prediction of the simulation model
The solution adopted in Europe consists in the definition of Nitrate Vulnerable Zones (NVZs), where the risk of N leaching in deep water bodies is high, and in the reduction of the amount of N fertilisers distributed over the fields, as this is considered to be the most effective measure to reduce groundwater contamination
Summary
Nitrate contamination of the groundwater throughout the world is a source of rising concern that has been faced through the introduction of several regulations in different countries. The groundwater nitrate concentrations in Europe exceed the international recommendations for drinking water (50 mg N-NO3- l-1 (1)), in 22% of cultivated land[2]. The Nitrate Directive in Europe[3] requires the implementation of measures to reduce nitrate leaching in water bodies. Agriculture is considered the main source of nitrate contamination in groundwater. The solution adopted in Europe consists in the definition of Nitrate Vulnerable Zones (NVZs), where the risk of N leaching in deep water bodies is high, and in the reduction of the amount of N fertilisers distributed over the fields, as this is considered to be the most effective measure to reduce groundwater contamination. The Italian regulation [5] suggests a parametric system based on empirical relationships between the soil or sub-soil characteristics and N leaching risk
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