Arsenic in groundwater from mineralised Proterozoic basement rocks of Burkina Faso

Abstract

This study describes the hydrogeochemistry and distributions of As in groundwater from a newly investigated area of Burkina Faso. Groundwaters have been sampled from handpumped boreholes and dug wells close to the town of Ouahigouya in northern Burkina Faso.Although most analysed groundwaters have As concentrations of less than 10 µg L -1 , they have a large range from <0.5 to 1630 µg L -1 . The highest concentrations are found in borehole waters; all dug wells analysed in this study have As concentrations of <10 µg L -1 .Skin disorders (melanosis, keratosis and more rare skin tumour) have been identified among the populations in three villages in northern Burkina Faso, two within the study area.Although detailed epidemiological studies have not been carried out, similarities with documented symptoms in other parts of the world suggest that these are likely to be linked to high concentrations of As in drinking water. The high-As groundwaters observed derive from zones of gold mineralisation in Birimian (Lower Proterozoic) volcano-sedimentary rocks, the gold occurring in vein structures along with quartz and altered sulphide minerals (pyrite, chalcopyrite, arsenopyrite). However, the spatial variability in As concentrations in the mineralised zones is large and the degree of testing both laterally and with depth so far limited. Hence, concentrations are difficult to predict on a local scale. From available data, the groundwater appears to be mainly oxic and the dissolved As occurs almost entirely as As(V) although concentrations are highest in groundwaters with dissolved-oxygen concentrations <2 mg L -1 . The source is likely to be the oxidised sulphide minerals and secondary iron oxides in the mineralised zones. Positive correlations are observed between dissolved As and both Mo and W which are also believed to be derived from ore minerals and oxides in the mineralised zones. The discovery of high As concentrations in some groundwaters from the Birimian rocks of northern Burkina Faso reiterates the need for reconnaissance surveys in mineralised areas of crystalline basement.

Arsenic in African Waters: A Review

“…In contrast to surface waters, the origin of the high levels of arsenic in groundwater is mainly natural. So, the high concentrations of arsenic reported in the groundwater by Smedley et al (2007) in Burkina Faso (1630 μg L −1 ) and Kusimi and Kusimi (2012) in Ghana (1760 μg L −1 ) have for origin weathered rocks of the underlying geology and are not due to mining activities. When considering the concentrations of arsenic in surface waters (0.5 to 73 μg L −1 ) and in groundwaters (<0.1 to 4 μg L −1 ) from Tarkwa (Asante et al 2007), or the ones in Obuasi ranging from <2 to 175 μg L −1 and from <2 to 64 μg L −1 , respectively, in surface waters and groundwater (Smedley 1996), two gold mining areas in Ghana, it can be noticed that mining activities affect less the groundwaters than surface waters.…”

Arsenic in drinking water: a worldwide water quality concern for water supply companies

“…In the past years, more and more countries have found their waters to be affected by arsenic contamination due to mining wastes, e.g., Poland, Korea and Brazil (Marszałek and Wasik, 2000;Woo and Choi, 2001;Borba et al, 2003). More recently, groundwater in Burkino Faso was measured to be contaminated by arsenic, up to 1630 µg L −1 , caused by mining activities (Smedley et al, 2007). Furthermore, Gunduz et al (2009) reported elevated arsenic levels (max.…”

“…Only contamination by pathogenic microorganisms has a bigger impact worldwide. Figure 1 Arsenic-affected countries (red) of the world (Smedley and Kinniburgh, 2002;Appleyard et al, 2006;Petrusevski et al, 2007;Smedley et al, 2007;Gunduz et al, 2009) Arsenic contamination of groundwater has been found to occur due to geothermallyinfluenced groundwater, mineral dissolution (e.g., pyrite oxidation), desorption in the oxidising environment, and reductive desorption and dissolution (Smedley and Kinniburgh, 2002). Table 1 gives an overview of the arsenic concentrations Figure 1.…”

“…Table 1 gives an overview of the arsenic concentrations Figure 1. Arsenic-affected countries (red) of the world (Smedley and Kinniburgh, 2002;Appleyard et al, 2006;Petrusevski et al, 2007;Smedley et al, 2007;Gunduz et al, 2009). arsenic in wallpaper. The manufacturers denied all claims.…”

Hard-rock aquifers in tropical regions: using science to inform development and management policy

“…There remain many instances of 'drilling blind' in rural water-supply provision, constructing unnecessarily deep waterwells, and failing potable drinking-water quality standards (due to hazardous or troublesome constituents such as fluoride, soluble iron or salinity; Chilton and Foster 1995;Edmunds and Smedley 2005;Smedley et al 2007). Such problems are widely increasing the unit cost of rural water-supply provision, and in some areas mean that adequate sources are not being provided.…”