Relationships between heavy metals content and soil properties in minesoils

Mining can be important causes of environmental degradation. Opencast mines produce a large amount of waste because the ore is a small fraction of the total volume of the mined material. In mine spoils, the formed soils have severe physical, chemical and biological limitations. Minesoils usually have high heavy metal levels because wastes contain metallic minerals. High trace elements levels, mainly in available form, will impede the revegetation to stabilize the tailings. Twenty-five soils (Anthropic Regosols) were selected and characterized. Minesoils come from two mine tailings (Touro: copper mine and Meirama: lignite mine) located in Galicia (Spain). Total, DTPA-extractable and total dissolved contents of Cd, Cr, Cu, Ni, Pb and Zn were determined. Minesoils characteristics and heavy metal availability were related to establish the dependency among them. Total heavy metal dissolved and DTPA–extractable contents are low in all the soils except the Cu-dissolved content in soils from copper mine spoils. These soils have a total Cu content higher than the intervention limit of diverse reference guides. In Touro minesoils, Cr, Ni and Zn total contents come from the parent matter of these soils. The correlation established between the Cr, Ni, and Zn total content suggests its common origin through the soils parent matter. Heavy metal contents of Meirama minesoils, furthermore, come from the fertilizers, and animal manure. Iron and manganese oxides, humified organic matter, and clay minerals, like gibbsite, chlorite, smectite and goethite, are the soil components with greater effect in the decrease of heavy metal availability.