Identification of potential causes of nitrate pollution in three apulian aquifers (Southern Italy)

This study investigates nitrate pollution in three Apulian aquifers (i.e., Murgia, Salento, and Tavoliere) by analysing its relationship with physiochemical variables and land use classes from Corine Land Cover. Geostatistical tools, specifically Ordinary Kriging and Co-Kriging, were used to identify vulnerable areas and determine key factors influencing pollution. Nitrate was chosen due to its prevalence as a groundwater contaminant and its impacts on human health and environmental quality. The analysis is based on 29,367 chemical tests from 217 wells, covering the period 1996–2021 for the coastal karst aquifers of Murgia and Salento, and 2005–2021 for the porous Tavoliere aquifer. This timeframe enables a comprehensive assessment of nitrate variability under different hydrological conditions. Despite limitations in sampling distribution, the study identifies significant drivers of nitrate pollution. The correlation of nitrates with calcium, magnesium, and sulphates suggests that fertilizers containing these elements contribute to their elevated concentrations. Additionally, land use plays a crucial role, as certain crops demand heavy fertilization, while others generate nitrogen surplus depending on soil conditions. These findings emphasize the importance of understanding the factors driving nitrate pollution and the broader implications for groundwater quality. They underscore the need for continuous, spatially and temporally extensive monitoring and integrated management strategies to mitigate nitrate transport from soil to groundwater effectively.