Soil and plant contamination by lead mining in Bellmunt (Western Mediterranean Area)

Abstract

Galena has been mined in Bellmunt (Priorat, Western Mediterranean Area) since ancient times until 1972. While sediment pollution originated by the mining activity in the Ebro River passing the region has been investigated to some extent, the local impact on soils and plants has received poor attention. Here we report first results on the concentrations of major metal contaminants and antimony in soils and representative plants from four selected sites with different pollutant burdens around the mining area. Total (HNO3, HF digest) soil concentrations were analysed. Soils had alkaline pH (8.0±0.2), organic matter contents ranging from 8 to 24gkg−1, and a sandy-loam or a loamy-sand texture. Present study highlighted that metal accumulation in different plants varied with species, tissues and metals. All analysed plant species showed enhanced root and shoot concentrations of Cu, Pb, Zn, and Sb when growing on the more polluted soils and all, but one, restricted the translocation of metals from roots to shoots exhibiting shoot/root concentration ratios lower or close to unity. A notably exception was Moricandia moricandioides (Boiss.) Heyw. [M. ramburii Webb] where shoot/root Zn concentration ratios up 5.5 were observed. This metal accumulation pattern was only observed for Zn and not for other analysed metal contaminants. The concentrations of other, poorly mobile metals, like Pb or Cu were always higher in roots than in shoots (e.g. Pb shoot/root ratios ranged from 0.13 to 0.24). Taking into account the high Pb burden of the soil samples and these low shoot/root Pb ratios, it can be excluded that the particular Zn accumulation pattern of M. moricandioides was biased by soil contamination of shoot samples. To our best knowledge this is the first report of Zn accumulation behaviour in a Moricandia species. The soil-to-shoot transfer factors (SAF) for this species were, however, relatively low ranging from 0.2 to 1.3. Further studies are required to confirm the possible Zn-accumulator character of M. moricandioides.