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<p>Natural processes and human-generated pollution have impacted the groundwater quality in several regions worldwide. Identifying the causes and processes of groundwater quality alteration in these regions is fundamental for proper planning and management of water resources. This research aimed to depict the origins of salinity and nitrate in the groundwater and to derive the principal mechanisms governing its chemistry in the agricultural plain of Sidi Smail (northwestern Tunisia). Groundwater samples (<i>n</i> = 28) taken at the end of the hot and dry summer season from 15 boreholes and 13 wells were assessed regarding their physicochemical properties and stable isotope composition (δ<sup>18</sup>O and δ<sup>2</sup>H). The nitrate pollution index (NPI) was used to evaluate the degree of groundwater pollution. The results of the statistical analyses indicate that 88% of the groundwater samples were brackish/saline, with an average TDS value of 2,224 mg/L; moreover, 75% of the samples exhibited nitrate concentrations exceeding 50 mg/L. The groundwater chemistry is regulated by geogenic processes, such as the dissolution of Triassic evaporite and carbonate minerals and reverse ionic exchange reactions, as well as anthropogenic factors, including use of fertilizer in agriculture. Under hot and dry climatic conditions, the evaporation of surface water and groundwater significantly influenced their salinity and isotopic composition. The groundwater samples were grouped into five classes based on NPI values: clean (7%), light pollution (3%), moderate pollution (21%), significant pollution (14%), and very significant pollution (56%). Groundwater nitrate pollution was attributed to the overuse of nitrate-based fertilizers in agriculture and unsuitable conditions for biological denitrification. The combined use of geochemical tools, statistical methods, isotopic techniques, NPI, and geographic information system mapping provides a comprehensive framework for appraising the groundwater quality in a sub-humid to semi-arid region vulnerable to intensive fertilizer use. The findings of this research reveal a global need for adequate fertilizer use to protect groundwater resources from nitrate pollution.</p>

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Assessment of groundwater salinization and nitrate pollution in a sub-humid to semi-arid agricultural area: a case study of the Sidi Smail plain in northwestern Tunisia

  • 期刊论文

  • 发表日期：

    2026年2月16日

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  • Ghofrane Charrada,
  • Brahim Askri,
  • Wissem Hamdi,
  • Salah Jellali,
  • Boulbaba L’taief

摘要

Natural processes and human-generated pollution have impacted the groundwater quality in several regions worldwide. Identifying the causes and processes of groundwater quality alteration in these regions is fundamental for proper planning and management of water resources. This research aimed to depict the origins of salinity and nitrate in the groundwater and to derive the principal mechanisms governing its chemistry in the agricultural plain of Sidi Smail (northwestern Tunisia). Groundwater samples (n = 28) taken at the end of the hot and dry summer season from 15 boreholes and 13 wells were assessed regarding their physicochemical properties and stable isotope composition (δ18O and δ2H). The nitrate pollution index (NPI) was used to evaluate the degree of groundwater pollution. The results of the statistical analyses indicate that 88% of the groundwater samples were brackish/saline, with an average TDS value of 2,224 mg/L; moreover, 75% of the samples exhibited nitrate concentrations exceeding 50 mg/L. The groundwater chemistry is regulated by geogenic processes, such as the dissolution of Triassic evaporite and carbonate minerals and reverse ionic exchange reactions, as well as anthropogenic factors, including use of fertilizer in agriculture. Under hot and dry climatic conditions, the evaporation of surface water and groundwater significantly influenced their salinity and isotopic composition. The groundwater samples were grouped into five classes based on NPI values: clean (7%), light pollution (3%), moderate pollution (21%), significant pollution (14%), and very significant pollution (56%). Groundwater nitrate pollution was attributed to the overuse of nitrate-based fertilizers in agriculture and unsuitable conditions for biological denitrification. The combined use of geochemical tools, statistical methods, isotopic techniques, NPI, and geographic information system mapping provides a comprehensive framework for appraising the groundwater quality in a sub-humid to semi-arid region vulnerable to intensive fertilizer use. The findings of this research reveal a global need for adequate fertilizer use to protect groundwater resources from nitrate pollution.