Groundwater vulnerability to geogenic contaminants: a case study, Tanzania

Groundwater quality is in most cases influenced by geogenic contaminants, which include arsenic, fluoride, salinity, iron and hardness. The main factors behind the natural occurrence of these constituents in groundwater are geologic settings and types of rocks. In Tanzania, the main sources of fluoride in groundwater are the volcanic ashes caused by rifting of the East African Rift System (EARS). During a field survey in Tanzania, primary and secondary data were collected. Fluoride concentrations were measured by SPADNS Colorimetric method and arsenic by Wagtech Kit. Higher median fluorides were recorded in Shinyanga (2.9 mg/L), Arusha (1.2 mg/L), Singida (1.1 mg/L), and Mwanza Region (1.5 mg/L). All water samples indicated arsenic concentration below the WHO guideline value of 10 μg/L. Excessive salinity in terms of Total Dissolved Solids ranging from 60 to 11300 mg/L, were recorded in Singida, Dar es Salaam, and Kilimanjaro Regions.