Only a very small number of the 98 naturally occurring elements have the potential to be geogenic contaminants. There are three critical factors:
- their concentration in rocks and sediments,
- their solubility under at least some environmental conditions and
- their presence in soluble form in concentrations that are toxic to humans.
The most common soluble ions in groundwater are sodium (Na+), magnesium (Mg2+), calcium (Ca2+), chloride (Cl-), bicarbonate (HCO3-) and sulphate (SO42-). While these can make water unpalatable, they do not pose a direct threat to health. Contamination with dissolved iron (Fe) and manganese (Mn) can occur in groundwaters with little or no oxygen. High levels of these elements are also more of an aesthetic than a health concern, though there is increasing evidence that exposure to manganese in drinking water can cause neurological problems (e.g. Wassermann et al., 2006). Of all inorganic groundwater contaminants, arsenic (As) and fluoride (F) clearly represent the greatest threat to human health. Many millions of people are affected worldwide. Other elements, such as selenium (as selenate), uranium (carbonated anions), boron and chromium (as chromate), can be important locally but are not as widespread as arsenic and fluoride.
Below you can learn about natural contamination related to arsenic and fluoride in groundwater.
Where does arsenic groundwater contamination occur?
Where does fluoride groundwater contamination occur?
NOTE: Article from the Geogenic Contamination Handbook