Arsenic has to been known to occur in Nigeria especially in the western regions particularly in Ogun state.
Occurrence of arsenic in this region is mainly as a result of weathering of sedimentary rocks (majorly sand stones) which have been found to contain high levels of arsenic and soils and subsequent transportation of the weathering products by air and water into the atmosphere and ground water respectively.
Arsenic has been found to occur in this region in -3, 0, +3 and +5 oxidation states. The concentration of As in this region particularly ground waters ranges between 1-2mg/L and is present as +5 oxidation state. In this region the arsenic occurrence levels increases significantly to about 10mg/Lwhere there are sulphide minerals present in abundance in the sedimentary area.
SUMMARY ON ARSENIC
Arsenic is an extremely toxic and carcinogenic metalloid contaminant that adversely affects the environment and human health. Widespread As contamination of terrestrial and aquatic environments from both geogenic and anthropogenic sources has been discovered in many parts of the world. It (As) exist in water and soil (aquatic and terrestrial respectively) in valence state and are predominantly As(III) (toxic) and As(IV) (non-toxic). Although some considerable amount of arsenic have been known to occur in plants.
Management of As contaminated soil and water are important to promote and sustain environmental health and reduce impact to humans. A number of physical, chemical, and biological technologies involving simple filtration, precipitation, biosorption, and rhizofiltration have been developed to remediate As-contaminated soil and water. Conventional physical and chemical remedial measures usually are quite expensive but may prove highly effective. These technologies however, have only been tested in small scales. Large scale use of these technologies requires skilled and trained personnel to treat the water and soil for use.
Remediation of As contaminated soils and the removal of As from portable ground water and irrigation water requires several approaches. To achieve optimum use of water that is, for drinking, irrigation and other domestic and industrial purposes, the remediation process involves the combination of physical, chemical and biological techniques for effective management of the arsenic contaminated environments.
In Areas where there is high level of pollution by arsenic, particularly in the western part of Africa, I personally recommend phytoremediation as the best possible method of removal in polluted environments. This is due to the low cost of removal and the results after removal are quite satisfactory. Hence, governments can embark on such programs to eliminate problems of groundwater poisoning by arsenic and other related metalloids.