Change in metals and arsenic distribution in soil and their bioavailability beside old tailing ponds.

The objectives of this study were to determine the metals and arsenic transfer from mining ponds to agricultural and forest soils, and identify the dynamic of metal(loid)s in the soil-plant system for a native plant species (Ballota hirsuta) in two old mining districts: La Unión and Mazarrón (Spain). Soils and plants from mining ponds and natural and agricultural areas were collected and analyzed for soil properties, and chemical partitioning of Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn and As. Results showed that mine, forest and agricultural soils were contaminated by As, Cd, Cu, Pb, and Zn. Chemical partitioning revealed higher mobility of metals in mining ponds than natural and agricultural soils except for Fe and As which were mostly bound to soil matrix due to the mineralogical compositions of soils. The accumulation of metal(loid)s in B. hirsuta in La Unión decreased as Fe > As > Cr > Ni > Cu > Zn > Cd > Mn > Co > Pb while in Mazarrón was As > Fe > Cr > Pb > Cu > Ni > Co > Mn > Zn > Cd, showing that B. hirsuta has high ability to bio-accumulate Fe, As, Cr, Cu and Ni; and Pb (in Mazarrón), transferring a significant concentration of theses metal(loid)s, except Pb, to edible parts without exceeding the toxicity limits for animals. Therefore, B. hirsuta could be useful as phytoextractor species for Cr, Cu, As and Ni, while it can be used as phytostabilizer species for Zn, Co, Pb and Cd.