Investigating Nitrate Pollution Sources and NaturalBackground in Groundwater of the Densu Basin: A Model-based Approach

Nitrate is one of the dominant chemical pollutants of groundwater, and there is a need to mitigate groundwater pollution in rural, urban and industrial terrains in an aquifer system. The study assesses the extent of nitrate pollution in the Densu Basin because of its predominance in agriculture and urbanized vicinities by employing robust techniques for estimating both the natural background and human-induced concentrations. The statistical methods used to estimate these concentrations are the pre-selection method, graphical approach (probability plot),non-parametric approach (kernel density estimation), and parametric approach (Gaussian mixture model). The study shows that the Gaussian mixture model is robust enough in determining the spectral distribution and clustering of the nitrate concentration in the basin. It estimated the natural background and human-induced concentration at1.7±1.3 and 9.8±5.6, respectively. The results show that the natural background concentration in the basin is more dominant and hence, conducive for drinking. Also, we show that26%of anthropogenic sources have leaked into the natural groundwater of the Basin. The data suggest that the nitrate concentration in the Densu aquifer system is sourced from agricultural input, domestic effluent and atmospheric deposition. High nitrate loading was observed in areas of active agricultural activities (Suhum, AkwapemNorth, Ayensuano and Upper West Akim). These areas should be protected from further anthropogenic exposure