Heavy Metal Pollution in a Cu Mine Dump and in Close Agricultural Soils and Crops in Mozambique

Abstract

Heavy metal pollution is investigated for a mine dump and soils and crops located 0.5, 1, 1.5, 3 and 6 km from a Cu mine, analyzing the total, available and exchangeable Cu, Zn, Cr, Ni, Cd and Pb. The maximum total contents in the dumping site reached 10,000, 1500, 1000, 230, 180 and 0.6 mg kg−1 for Cu, Cr, Ni, Zn, Pb and Cd, respectively. Within agricultural soils, those located 1.5 km away showed the highest total concentrations. The available Cu, Zn, Cd and Pb values were higher in the dump compared with the soils, while Cr and Ni stood out in the samples located 1.5 km away. Regarding crops, the Cu, Cr, Ni, Cd and Pb concentrations were higher in plants situated 3 km away. Considering the toxicity limits, Cr and Ni presented higher levels in most cases, while Cu exceeded the limits in most of the dump and soil samples located 1.5 km away, whereas Pb only exceeded them in the dump. The contents in crops indicated higher values in plants growing 3 km away, with all samples showing Cr pollution problems. These results can be considered of environmental significance, both for Mozambique and globally in areas affected by heavy metal pollution caused by mining activities.