Evaluation of the Hydrogeochemical Characteristics and Heavy Metals Contamination Levels of Shallow Groundwater in the Bafia Agricultural Area, Centre Region Cameroon.

Shallow groundwater is an important resource within the framework of potable, continuous, and reliable water supply in the whole of Cameroon, particularly in Bafia, where there is a limited supply of piped-borne water. Increased population and intense agriculture, which involves the use of diverse agrochemicals, make it crucial to assess groundwater quality both for present and future use. The objectives of this study are to (a) identify the major seasonal hydrogeochemical processes, (b) determine groundwater quality with potential health risks and (c) assist local communities and water resource managers to sustainably manage the resource.  57 water samples (31 wells, 20 boreholes, 4 rivers and 2 springs) were collected, filtered, acidified with HNO3 and analyzed for major ions by Ion chromatography (samples for anions were not acidified) and heavy metals content by ICP-MS (Fe, Co, Ti, Sr, Sb, Al, Cr, Cu, Pb, Ni, As, Zn, Mn, Se, Sn, B, Cd). Results show that groundwater is acidic to neutral, soft to very hard, and generally fresh. Major ion concentrations increased from the rainy to the dry season and were within WHO limits (but for a few). The study shows that albite/anorthite, calcite/dolomite, and ion exchange contribute significantly to the major ion concentration in the study area. The 3 major water facies identified in the rainy season are the Ca-Mg-HCO3, Ca-Mg-Cl, and Na-Cl types; while two water types are identified in the dry season, including the Ca-Mg-HCO3 and Ca-Mg-Cl types, with mixing types like Ca-Mg-SO4-Cl and Na-K-HCO3. Results of heavy metals analyses show that most of the metals are within and some below WHO limits, while high Ti, Mn, Al, Fe, and Sr concentrations were observed in most samples. The heavy metal concentration was evaluated using indices like heavy metal pollution index (HPI), heavy metal evaluation index (HEI), and degree of contamination (Cd). The mean values of HPI and Cd (741 and 5 respectively) exceeded the critical limit, indicating highly contaminated water samples. Based on the HPI and Cd, 93% and 35% of the samples respectively are unacceptable for drinking purposes. Major ions PCA reveals 4 factors; the first is a result of natural processes with silicate weathering and the second reveals anthropogenic influences, mainly fertilizer input. The first factor for heavy metals reveals high pollution from inorganic fertilizers while the second shows water-rock interactions. Agricultural activities have a great impact on the water chemistry around the area; hence, it is recommended that a periodic and systematic study be carried out regularly, especially for the heavy metal concentrations. The study is the first of its kind to provide insight into heavy metals as well as an in-depth evaluation of hydrogeological processes influencing groundwater in the area and thus can offer a valuable reference point for the design of suitable techniques to manage groundwater resources.