Contamination of soils with dust fallout from the tailings dam at the Rosh Pinah area, Namibia: regional assessment, dust dispersion modelling and environmental consequences.

The bioaccessibility of metals and arsenic in topsoils around the Rosh Pinah Pb-Zn mine was tested with an in vitro method using a simulated gastric fluid. Gastric accessible contents of chemical elements in topsoil were found to increase in the ascending sequence: Fe (6.2%):As (8.6%):Cu (23.6%):Zn (39.3%):Mn (66.7%):Pb (85.9%). The evaluation of obtained data on gastric bioaccessibility indicates that a health risk related to soil or dust ingestion should be taken into account only in the case of lead. The areal extend to the area contaminated by dust fallout was verified by studying the distribution of metals in the subaerial parts of grass pasture. Dispersion modelling of suspended dust particles (TSP) in the air revealed that while the whole surface of the tailings dam was dry in the past due to infiltration and evaporation of water, the average yearly concentrations of TPS in the Rosh Pinah town amounted to 100-300 microgram/m3, but when two thirds of tailings dam surface has been covered with water, the concentrations of TPS markedly decreased to 30-100 microgram/m3. The results of dispersion modelling fit well with the results of ground geochemical surveys.
The bioaccessibility of metals and arsenic in topsoils around the Rosh Pinah Pb-Zn mine was tested with an in vitro method using a simulated gastric fluid. Gastric accessible contents of chemical elements in topsoil were found to increase in the ascending sequence: Fe (6.2%):As (8.6%):Cu (23.6%):Zn (39.3%):Mn (66.7%):Pb (85.9%). The evaluation of obtained data on gastric bioaccessibility indicates that a health risk related to soil or dust ingestion should be taken into account only in the case of lead. The areal extend to the area contaminated by dust fallout was verified by studying the distribution of metals in the subaerial parts of grass pasture. Dispersion modelling of suspended dust particles (TSP) in the air revealed that while the whole surface of the tailings dam was dry in the past due to infiltration and evaporation of water, the average yearly concentrations of TPS in the Rosh Pinah town amounted to 100-300 microgram/m3, but when two thirds of tailings dam surface has been covered with water, the concentrations of TPS markedly decreased to 30-100 microgram/m3. The results of dispersion modelling fit well with the results of ground geochemical surveys.