Integrated assessment of groundwater quality beneath the rural area of R'mel, Northwest of Morocco

This study evaluates the effect of anthropogenic activities on the quality of groundwater beneath a rural area (R'mel area) located in the perimeter of Loukkos, Northwest Morocco. Ten public wells for drinking water were sampled and characterized for physicochemical parameters, heavy metals and pesticides occurrence. Multivariate Statistical Analysis (MSA), Water Quality Index (WQI) and geographic information system (GIS) were employed to identify the sources of groundwater pollution, the suitability for drinking purposes and the groundwater quality distribution within the R'mel aquifer. The results showed that almost all the samples had concentrations of NO3− and Ca2+ exceeding the WHO limits set at 50 mg/L and 75 mg/L, respectively. The heavy metal content was very low in the groundwater except for arsenic which exceeded the WHO threshold of 10 μg/L in four locations. Nine pesticides including Atrazine, Trietazine, Terbutryn, Chlorpyriphos ethyl, Endosulfan sulphate, Endosulfan alpha, Endosulfan beta, Metribuzin and Metolachlor were detected in four sites. However, no pesticides exceeded the standard of 0.1 μg/L set by the European Union. The Principal Component Analysis (PCA) demonstrated that the R'mel groundwater was exposed to two types of pollution that depend on groundwater redox conditions, the first being defined as the release of geogenic/anthropogenic As under reducing conditions (minor pollution), while the second represents the nonpoint source pollution from agriculture (major pollution). The Hierarchical Cluster Analysis (HCA) has classified the samples into four clusters reflecting the rate of groundwater mineralization in the study area. Differently to HCA, the WQI has generated three groups. The comparison between WQI and HCA showed that the combined use of the two methods may lead to a better classification of groundwater samples. The spatial distribution of NO3− and WQI indicated the areas affected by irrigated agriculture, and the impact of anthropogenic activities on the R'mel groundwater has been assessed. [Display omitted] •A wide range of pesticides (80 multi-residues) was analyzed for the first time on the scale of the Loukkous perimeter.•A drastic contamination of drinking groundwater by agricultural effluents has been identified.•A possible combination and/or merger between WQI and HCA can be used to effectively optimize the groundwater classification.•An excess of fertilizers could reduce DO and increase DOC levels accelerating