Groundwater constituents and trace elements in the basement aquifers of Africa and sedimentary aquifers of Asia: medical hydrogeology of drinking water minerals and toxicants

The use of groundwater, a major source of potable water, in developing countries has proven to be an invaluable resource for local populations. The ability to safely use this water for drinking, however, depends on its chemical quality, a factor primarily controlled by various aquifer attributes such as geology and geochemistry. On a global scale, groundwater is primarily sourced from either sedimentary or basement aquifers. In this study, we compared the groundwater constituents and trace elements found in these two types of aquifer system in the context of medical hydrogeology, i.e. the status of groundwater mineral nutrients and pollutants, and their complex interaction in relation to human health. The evaluation work used a collated geochemical dataset developed for Bangladesh sedimentary aquifer data (n = 474), basement aquifer data from Northern Ghana (n = 184) and Central Tanzania (n = 73). An assessment of the mineral concentration in regards to dietary needs showed that the sedimentary aquifers found in Bangladesh have almost double the concentration of salubrious minerals such as calcium, magnesium and iron relative to the basement aquifers (Ghana and Tanzania). It should be noted, however, that the groundwater was also found to contain excessive levels of arsenic in the sedimentary aquifers and high levels of fluoride in those countries sourcing water from within basement rock; levels at which both elements pose a serious public health threat. Excessive sodium in drinking water is also an issue as this, combined with the normal dietary sodium level intake, may lead to hypertension and cardio-metabolic diseases. Unfortunately, health-based guideline values for drinking water containing sodium are non-existent or poorly defined, a fact which warrants further consideration at both a national and international level. The use of groundwater for drinking may assist in increasing the level of mineral nutrient uptake in the local population, however, it must also be augmented by a nutritious food supply in order to satisfy normal human dietary requirements.