Major ions, δD, δ18O and microbial characterization of drinking water sources along the West Coast of Cameroon

Abstract

Hydrochemical data coupled to microbial content are required for a comprehensive understanding of water quality. Such knowledge is pertinent to the design of sustainable livelihoods related to water resources. Here we present physico-chemical, stable environmental isotopes and microbial characteristics of drinking water sources that were investigated during the dry and rainy seasons of 2015 and 2018, along the West Coast of Cameroon to assess potability, health impacts and impacts of climate change. Field work involved mapping, collection of water samples and measurement of physical parameters (pH, EC and temperature). Major ions and total coliform were analyzed using Ion Chromatography and the Violet Red Bile Lactose Agar, respectively. Microbial contaminated samples were analyzed for Escherichia coli and Salmonella spp. bacteria using MacConkey agar and Salmonella Shigella Agar agar, respectively. The health impacts of the water on the population were assessed based on records of water borne diseases from health centers and a hospital within the study area. δ18O and δD isotopic ratios of 6 monthly rainfall samples and 12 samples from the different water sources were analyzed with the PICARRO made Cavity Ring Down Spectrometer, model L2120. The results revealed various seasonal dependent water chemistry with facies such as Ca+Mg-HCO3, Na+K-Cl and Ca+Mg-Cl+SO4, Ca+Mg-HCO3, Na+K-HCO3 for the wet and dry seasons, respectively. Furthermore, except for some rivers that showed slight evaporation effects, the waters in the springs and wells represent pristine rainwater, which shows δ18O depletion trend in the 1960s and enrichment between 1972 and 2017. 57% of the water sources were contaminated by either Escherichia coli and/or Salmonella spp., thus not potable as records from health centers indicated high prevalence of water borne diseases, caused by microbial contamination of the drinking water sources and inadequate sanitation and hygiene. Based on major ions content, 16% of the water sources were unsuitable for drinking. Factors that control water chemistry include water–rock interaction, anthropic inputs, and climate change driven seawater intrusion. Integrated water resources management would include among others, construction of drinking water treatment plants and implementation of climate change adaptation measures in the water sector.