The influence of geochemical and physicochemical factors on the spatial variation of the abundance of bacteriological contaminants in the groundwater of a Bouregreg watershed in Morocco

Abstract

Preserving the integrity of groundwater ecosystems and safeguarding their native microbial biodiversity has emerged as a critical global challenge for the sustainable management of these water resources, particularly with regard to quality and the prevention of water-borne diseases. However, the degradation of these ecosystems is increasingly attributed to the ability of non-indigenous bacteria to survive and multiply in favorable conditions often linked to geogenic and physicochemical factors. This work aims to investigate this hypothesis and to study the influence of geochemical and physicochemical factors on the contamination of groundwater in the Bouregreg watershed in Morocco. This study's novelty lies in the combined application of multiple advanced analytical techniques — namely Self-Organizing Maps (SOM), Ascending Hierarchical Classification applied to SOM (AHC-SOM), and Principal Component Analysis (PCA) — to simultaneously explore the spatial and statistical relationships between bacteriological contamination and geochemical/physicochemical factors. The results indicate that, irrespective of the type of soil lithology, contamination by various non-indigenous bacteria is consistently observed. However, the underlying limestone and shales exhibited higher concentrations of total coliforms and E. coli than the sandstone bedrock. Multivariate statistical analysis revealed no significant correlation between bacterial contamination and physicochemical parameters, except for organic matter. The geospatial analysis identified areas at risk in the northwestern sector with a high abundance of bacteriological contaminants (TC, FC, E. coli and EI), in contrast to an absence for others (SRB and V. cholerae) throughout the study region. Further investigations are recommended to study the conditions governing the survival and multiplication of SRB and V. cholerae and the associated environmental factors.