ARSENIC AND HEAVY METALS IN SURFACE WATER IN SWAZILAND, SOUTHERN AFRICA

Swaziland, an independent kingdom in southern Africa, suffers from the highest per capita rates of both HIV (26-31% of adult population) and tuberculosis (1.3% of adult population) infection in the world. There is considerable overlap among the infected populations as 80% of tuberculosis patients are also HIV positive. Recent studies have shown that elevated levels of As and heavy metals (especially Pb and Cd) in blood, hair, and nails are good predictors of development of secondary infections such as tuberculosis in individuals who are HIV positive. Swaziland is an area that would be expected to have elevated As in surface water and groundwater due to the abundance of Au, Fe and Sn mines, and the continued use of arsenical pesticides and herbicides in sugarcane farming and pulp forestry. The objective of this study is to carry out the first As survey in Swaziland. The first step has been to focus on surface water, which can provide a rapid assessment of As in the regional hydrologic system. Water samples have been collected from 84 sites throughout Swaziland from the major rivers (Komati, Umbuluzi, Usutu, Ngwempsi, and Lusushwana) and their tributaries. Water temperature and pH were measured on-site with the Hach EC10 pH Meter. Concentrations of nitrate, phosphate and sulfate were measured with the Hach DR-2700 Spectrophotometer. The Optima 8000 ICP-OES (Inductively Coupled Plasma - Optical Emission Spectrometer) is being used to measure concentrations of As and the associated sulfide-forming elements Ag, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Ti and Zn. Out of 55 sites analyzed thus far, WHO drinking water standards for As, Pb and Cd were exceeded for 44%, 78% and 20% of sites, respectively. Maximum concentrations for As, Pb and Cd were 0.209 mg/L, 0.210 mg/L and 0.087 mg/L, respectively, with geometric mean concentrations of 0.014 mg/L, 0.028 mg/L, and 0.001 mg/L, respectively. Strong positive linear correlations were found between As and Pb (R² = 0.77, P < 0.001) and Cr (R² = 0.76, P < 0.001), with weaker positive linear correlations between As and Ag (R² = 0.45, P < 0.001), Ni (R² = 0.28, P < 0.001), Ti (R² = 0.11, P = 0.01), and Cd (R² = 0.10, P = 0.02). The above correlations are consistent with As mobilization by sulfide oxidation, which suggests an impact of mining on surface water. Further results will be reported at the meeting.