This work is to establish the hydrochemistry and origin of groundwater in some parts of the Gushegu district of the Northern Region of Ghana. Hydrochemical data from 19 groundwater and 7 rock samples have been used to evaluate water quality, water types, and sources of various ions as well as origin of the groundwater. The study results show that the quality of groundwater from the area is generally not good due to their fluoride (F⁻), bicarbonate (HCO₃⁻) and electrical conductivity (EC) concentrations. The F⁻ contents of the groundwater have values as high as 1.97 mg/L, with 53 % of the groundwater having concentrations of F⁻ exceeding the WHO recommended allowable limits. These high F⁻ values have the potential of causing serious health problems such as kidney failure, dental and skeletal fluorosis, reproductive problem and reduction in intelligent quotient of consumers. A plot of Gibbs diagram reveals that rock weathering and precipitation are the major hydrogeochemical processes regulating the water chemistry of the study area. Petrographic thin-section analyses of rock samples identify minerals present to be muscovite, plagioclase feldspars, quartz, sericite and iron oxide. Stable isotope (¹⁸O and ²H) composition of the waters reveals that most of the groundwater is likely to be recharged from local precipitation, indicating their meteoric origin. Some samples, however, showed considerable evaporation.

An assessment of some heavy metals concentrations in lettuce in irrigated with waste water in Tamale Metropolis in Ghana has been carried out. Analysis of water and lettuce samples revealed that the mean concentrations of Fe, Mn, Cu, Zn, Cd and Pb in lettuce were 0.436, 0.345, 0.068, 0.017, 0.04 and 0.038 mg/L and 0.167, 0.163, 0.104, 0.127, 0.142 respectively. With exception of Mn and Cd, the concentrations of heavy metals in the irrigation water, irrigated soils and irrigated lettuce, were within the FAO recommended levels. The mean concentrations of nutrients (NO3-N, SO4 and PO4-P) in the wastewater-irrigated lettuce, and well water-irrigated lettuce were 15.36, 0.88, 0.28 and 19.09, 1.117, 0.0573 respectively. Though, heavy metals concentrations in the lettuce were low, regular monitoring are required to prevent heavy metal accumulation with their attendant health implications in the consuming public.