Differences in the bioaccessibility of metals/metalloids in soils from mining and smelting areas (Copperbelt, Zambia)

Differences in the total and bioaccessible concentrations of As and metals (Co, Cu, Pb, Zn) in topsoils (n = 107) from the mining and smelting areas in the Zambian Copperbelt were evaluated. The mean total concentrations of metals and As in topsoils were generally 2 to 7× higher in the smelting area, indicating significantly higher effect of smelter dust fallout on the degree of topsoil contamination. The contaminant bioaccessibility was tested by an US EPA-adopted in vitro method using a simulating gastric fluid containing a 0.4 M solution of glycine adjusted to pH 1.5 by HCl. Higher bioaccessibilities in the smelter area were observed for As and Pb, attaining 100% of the total metal/metalloid concentration. The maximum bioaccessibilities of As and Pb in the mining area were 84% and 81%, respectively. The ranges, mean and median bioaccessibilities of Co, Cu and Zn were similar for the two areas. The maximum bioaccessibilities of Co, Cu and Zn were 58–65%, 80–83% and 79–83%, respectively. The obtained data indicate that a severe health risk related to topsoil ingestion should be taken into account, especially in smelting areas.

► Contaminant concentrations in topsoils are 2 to 7 times higher in a smelting area.
► Higher gastric bioaccessibility (% of total content) of As and Pb near the smelter.
► Similar Co, Cu and Zn bioaccessibilities for mining and smelting areas.
► Highest health risk related to soil ingestion for Cu and Co in the smelting area.