The spatiotemporal variation in lead and zinc contents in the Moulouya River (northeastern Morocco)

Abstract

In the context of the challenges imposed by climate change, which exerts constant pressure on water security in Morocco, the Moulouya River, one of the main sources of surface water, frequently undergoes spatiotemporal variations in its quality. This situation is particularly worrying in the upstream part of the river, where the old Zaida mine is located, which is now inactive and leaves significant residues in the form of slag heaps in direct contact with the waters of the Moulouya River. To assess the impact of this abandoned mining waste, eight (08) water sampling stations (S1 to S8) were chosen to analyse the concentrations of two (02) essential metals, namely, lead and zinc. The results revealed lead concentrations of approximately 0.13 mg/L on average during the dry period and 0.09 mg/L during the humid period. The average zinc concentration was 0.29 mg/L during the dry season and 0.32 mg/L during the humid season. The maximum concentrations were recorded at the stations closest to the aforementioned mine, in particular, S1, S2 and S3. Other maximum concentrations were observed at station S6. These results highlighted the significant impact of mining slag heaps exposed to the open sky on the physico-chemical and metallic quality of Moulouya waters. This finding highlights the urgency of continued monitoring of this vital water resource to protect it against potential risks of contamination.