Abstract
This paper assesses the impacts of farmers’ intensive use of agrochemicals (fertilizers and pesticides) on groundwater quality in the Kahe catchment. Samples were collected during the wet and dry seasons of the year 2018 and analyzed for the presence of agrochemicals in the water. Groundwater chemistry was dominated by magnesium-sodium-bicarbonate (Mg-Na-HCO3−). The cations levels were in the trend of Mg2+ >Na+ > Ca2+ > K+, whereas anions were HCO3− > Cl− > SO42− for both seasons. The NO3− had an average value of about 18.40 ± 4.04 and 7.6 ± 1.7 mg/L in the wet and dry season, respectively. Elevated levels of nitrate, sulfate, phosphate, and ammonium were found in water samples collected near the large-scale sugarcane plantation in the catchment. For both seasons, Pb, Cd, Fe, Mn, Zn and Cu concentrations averaged approximately 0.08 ± 0.03, 0.11 ± 0.03, 0.16 ± 0.02, 0.11 ± 0.01, 0.46 ± 0.05, and 0.55 ± 0.02 mg/L, respectively. On the other hand, the concentrations were higher in shallow wells than in the deep boreholes. Pesticides’ residues were below the detection limit in all sampled groundwater. The findings from this study provide important information for intervention in groundwater quality management in Kahe Catchment, Tanzania.
Highlights
Groundwater is a vital water supply source to a community for different purposes in many sub-Saharan Africa countries [1]
The analyzed groundwater parameters were compared to the recommended allowable drinking water Tanzanian Bureau of Standard [55] and international guidelines by World Health Organisation (WHO) [24]
Groundwater quality for drinking purposes in the Kahe catchment is generally good; in some areas it is considered undesirable for drinking purposes with elevated concentrations
Summary
Groundwater is a vital water supply source to a community for different purposes in many sub-Saharan Africa countries [1]. It acts as an improved water supply in urban and rural areas so as to cope with surface water scarcity [2]. In agricultural fields, intensive use of agrochemicals (fertilizers and pesticides) have gradually increased in crop production worldwide [6]. Large- and small-scale farmers use agrochemicals to increase their crop yields. As a result, they have increased their rates of fertilizers and pesticides applications, which could be impacting the groundwater quality. Groundwater quality depends on different factors such as geological formation, soil type/soil permeability, the depth to the water table, the amount of rain and the hydraulic conductivity of the aquifer, and solubility of the rock materials within the aquifer system [7]
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