Impacts of hydrogeochemical processes and anthropogenic activities on groundwater quality in the Upper Precambrian sedimentary aquifer of northwestern Burkina Faso

Abstract

This study investigates the hydrogeochemical and anthropogenic factors that control groundwater quality in an Upper Precambrian sedimentary aquifer in the northwestern Burkina Faso. The raw data and statistical and geochemical modeling results were used to identify the sources of major ions in dug well, private borewell and tap water samples. Tap waters were classified as Ca-HCO 3 and Ca-Mg-HCO 3 types, reflecting the weathering of the local dolomitic limestones and silicate minerals. Dug well waters, with a direct contact with various sources of contamination, were classified as Ca-Na-K-HCO 3 type. Two factors that explain 94% of the total variance suggested that water-rock interaction was the most important factor controlling the groundwater chemistry. Factor 1 had high loadings on pH, Ca 2+ , Mg 2+ , HCO 3 − , SO 4 2− and TDS. These variables were also strongly correlated indicating their common geogenic sources. Based on the HCO 3 − /(HCO 3 − + SO 4 2−) ratios (0.8-0.99), carbonic acid weathering appeared to control Ca 2+ , Mg 2+ , HCO 3 − and SO 4 2− acquisition in the groundwater. With relatively lower Ca 2+ and Mg 2+ concentrations, the majority of dug well and borewell waters were soft to moderately hard, whereas tap waters were considered very hard. Thus, the dug well and, to a lesser extent, borewell waters are likely to have a low buffering capacity. Factor 2 had high loadings on Na + , NO 3 − and Cl −. The strong correlation between Na + and NO 3 − and Cl − implied that factor 2 represented the anthropogenic contribution to the groundwater chemistry. In contrast, K + had moderate loadings on factors 1 and 2, consistent with its geogenic and anthropogenic sources. The study demonstrated that waters from dug wells and borewells were bacteriologically unsafe for human consumption, and their low buffering capacity may favor mobility of potentially toxic heavy metals in the aquifer. Not only very hard tap waters have aesthetic inconvenient, but their consumption may also pose health problems.

Groundwater quality assessment and characterization of shallow basement aquifers in parts of ado ekiti metropolis, Southwestern Nigeria

“…The dissolved anionic species in the groundwater of the study area are in this order Cl − >HCO 3 − >SO 4 2− >NO 3 − . [28]. The dissolved cationic species in the groundwater of the study area in the following order is as follows: Ca 2+ >Mg 2+ >Na + >K + .…”

“…This is due to their simplicity and straightforwardness interpretation in the characterization of groundwater quality [12,13,23,24]. The contribution of geogenic and anthropogenic inputs in the pollution of groundwater has been recorded in several places [25][26][27][28]. The geogenic mode of groundwater pollution arises from the dissolved concentrations of ions from the minerals present in the host rock constituting the aquifer system, low resident time, flow paths and flow rates [11,26,29].…”

Mapping Ground Water Access in Two Rural Communes of Burkina Faso

“…Groundwater is generally suitable for drinking, although water quality is problematic in some cases. Shallow groundwater is exposed to nutrient and microbial contamination in many rural areas [26][27][28]. The study region is no exception; informal sanitation predominates, thus posing a risk to groundwater supplies [29][30][31].…”

Hydrogeochemical and Groundwater Quality Studies in the High Bandama Watershed at Tortiya (Northern of Côte d’Ivoire)

“…But Na and Cl may have some other source. According the study of Sako et al (2018) in the northwestern Burkina Faso, atmospheric deposition (dust and rainfall) and decomposition of organic matter may be a source of Cl.…”