RESUMO
Bedrock and soil samples from different soil profile layers were collected in an iron and manganese ore area of Longyan City and total amounts of Pb, Cd, and As were determined. The geochemical patterns of three heavy metal elements in the soil were studied using ordinary Kriging interpolation and their sources were also analyzed. High concentrations of Pb and As were found near the mining area to the west, at the intersection of two rivers in the middle, and near the waste rock heap in the east of the study area, while the main area of Cd contamination is located near to the mining areas and ore dressing plant. Based on a horizontal section, the content of Pb, Cd, and As in soils from the high-value region of each layer decreased with horizontal distance from the mining area. Vertically, the concentrations of heavy metals in different soil layers were significantly correlated. Near the mining area, Pb, Cd, and As concentrations first increased and then decreased with depth. In other high-value regions, the concentrations of these three heavy metals decreased with soil profile depth. These heavy metals inherit the characteristics of the deposit and bedrock during the weathering process, and the content of Pb and As in the soil at different depths was significantly positively correlated with granite and diorite content. Although As has been artificially influenced by mining, this influence does not appear to be strong; parent rock in the study area shows higher concentrations of heavy metals, while at the same time, the Pb and Cd content of soil is significantly higher than in the rock indicating the influence of human activities including mining, transportation, and agricultural production. Further attention should now be paid to the quality and safety of agricultural products, crop growth, and possible environmental risks in the study area.
