The distribution and phytoavailability of heavy metal fractions in rhizosphere soils of Paulowniu fortunei (seem) Hems near a Pb/Zn smelter in Guangdong, PR China

In order to understand the change of soil environment induced by re-vegetation, the physico-chemical properties, heavy metal (Cu, Pb, Cd and Zn) distribution and bioavailability was investigated in four different sites with different re-vegetation time. Results showed that soil physico-chemical properties and total content of heavy metals consistently increased with the re-vegetation time. The proportions of carbonate, Fe–Mn oxide and organically bound fractions in the rhizosphere soils were higher than those in the bulk soils. However, the proportions of exchangeable and residual fractions were less. The pH, electrical conductivity (EC) and organic matter (OM) were the most important factors affecting the distribution of heavy metal fraction. The exchangeable and organically bound fractions were easily available for Paulownia fortunei, but carbonate, Fe–Mn oxide and residual fractions were not. The correlation analysis indicated that the heavy metal contents in roots were generally and significantly correlated with total metal contents and metal contents bound to different fractions, thus might be better indicators of heavy metals bioavailability in soil than those in aboveground tissues.