Trace elements absorption by citrus in a heavily polluted mining site

Abstract

This work deals with the problems derived from the agriculture use of soils affected by metal sulphide exploitation in Riotinto mining district (Iberian Pyrite Belt). The distribution of trace elements, the hazard for agriculture in small private orchard and intensive citrus plantations and the absorption by citric trees was investigated. In general, the total concentrations of trace elements exceeded the regional background and threshold values, particularly those affected by mining activity such as As (up to 204mg/kg), Cu (586mg/kg), Pb (598mg/kg) and Zn (795mg/kg). The areal distribution of potentially toxic elements in the soils studied and their availability were used to delimit hazardous zones for agricultural activity in Riotinto area. In spite of a high availability of metals found, their concentrations in citrus leaves were low. The transfer factors calculated showed the following absorption sequence: Zn>Ni>Cu>Pb>As, and no hazard was predicted even for soils with high metal contents. The major risk for agricultural use of soils seemed to be located in small private orchards, where small vegetables could absorb bioavailable elements.