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<p>In Morocco, despite the importance of agriculture to the national economy and the diversity of aquatic ecosystems, data on pesticide contamination of surface waters remain extremely limited. The Loukkos basin, located in northwest Morocco, is one of the country's most productive agricultural areas, characterized by intensive farming and heavy pesticide use. However, data on pesticide contamination of aquatic environments in this region remain very limited, and no assessment of the risks to aquatic ecosystems from pesticide exposure has yet been carried out. Against this backdrop, this study aims to characterize water and sediment contamination and assess potential risks to aquatic biodiversity using deterministic and probabilistic approaches. Water and sediment samples were collected along the Loukkos River. Pesticides were extracted and analyzed by gas chromatography coupled to an electron capture detector (GC-ECD). Ecotoxicological risks were assessed using a combination of species sensitivity distributions (SSD) to estimate HC5, a probabilistic approach based on the probability of a measured environmental concentration (MEC) affecting a species (P(Φ)), and the classic risk quotient (RQ) method, based on acute and chronic exposure scenarios. Eight pesticides were detected in surface waters and nine in sediments, mainly insecticides and fungicides. The SSDs revealed very low HC5 values for several substances (notably bifenthrin, chlorpyrifos-ethyl, and thiacloprid), revealing high toxicity for sensitive species. Probabilistic assessment showed that some pesticides, in particular chlorpyrifos-ethyl, malathion, parathion-methyl, methidathion, bifenthrin, thiacloprid, pyraclostrobin, and azoxystrobin, can affect more than 5% of aquatic species, especially in the case of chronic exposure. Risk quotient analysis confirms moderate to very high levels of ecological risk, particularly for pesticides accumulated in sediments. The results indicate significant ecotoxicological risks associated with pesticide contamination in the Loukkos River, likely to compromise aquatic biodiversity. The combined SSD, probabilistic assessment, and risk quotient approach provides a robust and relevant framework for ecological risk assessment. This study highlights the urgent need to strengthen pesticide management and monitoring strategies to protect aquatic ecosystems in Morocco.</p>

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Ecotoxicological Risk Assessment of Pesticides in Water and Sediments of the Loukkos River (Larache, Morocco) using Deterministic and Probabilistic Approaches: Risks to Aquatic Biodiversity

  • 期刊论文

  • 发表日期：

    2026年6月22日

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  • Ahmed Bagayou,
  • Ahlem Hamdache,
  • Hicham El Bourki,
  • Yassine Diane,
  • Mohammed Ezziyyani

摘要

In Morocco, despite the importance of agriculture to the national economy and the diversity of aquatic ecosystems, data on pesticide contamination of surface waters remain extremely limited. The Loukkos basin, located in northwest Morocco, is one of the country's most productive agricultural areas, characterized by intensive farming and heavy pesticide use. However, data on pesticide contamination of aquatic environments in this region remain very limited, and no assessment of the risks to aquatic ecosystems from pesticide exposure has yet been carried out. Against this backdrop, this study aims to characterize water and sediment contamination and assess potential risks to aquatic biodiversity using deterministic and probabilistic approaches. Water and sediment samples were collected along the Loukkos River. Pesticides were extracted and analyzed by gas chromatography coupled to an electron capture detector (GC-ECD). Ecotoxicological risks were assessed using a combination of species sensitivity distributions (SSD) to estimate HC5, a probabilistic approach based on the probability of a measured environmental concentration (MEC) affecting a species (P(Φ)), and the classic risk quotient (RQ) method, based on acute and chronic exposure scenarios. Eight pesticides were detected in surface waters and nine in sediments, mainly insecticides and fungicides. The SSDs revealed very low HC5 values for several substances (notably bifenthrin, chlorpyrifos-ethyl, and thiacloprid), revealing high toxicity for sensitive species. Probabilistic assessment showed that some pesticides, in particular chlorpyrifos-ethyl, malathion, parathion-methyl, methidathion, bifenthrin, thiacloprid, pyraclostrobin, and azoxystrobin, can affect more than 5% of aquatic species, especially in the case of chronic exposure. Risk quotient analysis confirms moderate to very high levels of ecological risk, particularly for pesticides accumulated in sediments. The results indicate significant ecotoxicological risks associated with pesticide contamination in the Loukkos River, likely to compromise aquatic biodiversity. The combined SSD, probabilistic assessment, and risk quotient approach provides a robust and relevant framework for ecological risk assessment. This study highlights the urgent need to strengthen pesticide management and monitoring strategies to protect aquatic ecosystems in Morocco.