Source Identification and Speciation of Metals in the Topsoil of the Khli Ti Watershed, Thailand

The enrichment factor, multivariate analysis and metal speciation studies were used to identify degree, source and dispersal of metal contamination in Khli Ti watershed, Thailand. Topsoil samples were collected throughout the watershed, analyzed for total metal concentration. Sequential extraction was also carried out to determine geochemical phases of metals which were identified as exchangeable and bound to carbonates, Fe–Mn oxides, organic matter and residuals. Soil characteristics including pH, total organic carbon, redox potential, cation exchange capacity and texture were also analyzed. Principal component analysis yielded three metal groups which explained 83% of the variance. The concentrations of metals which were derived from lithogenic origin, such as Co, Cr, Fe, Ni and V were in natural background levels and were mostly bound to the residual phase. The remaining elements (i.e. Ba, Cd, Cu, Pb, Sb and Zn) were associated with the contamination from previous activities of the Pb-ore concentrator and Zn–Pb mining. Anthropogenic contamination mainly increased Pb and Zn bound to Fe–Mn oxides at the expense of residual fraction. Even though low exchangeable Pb contents in Khli Ti soils indicated low availability to plants, Pb bound to Fe–Mn oxides fraction might increase its mobility under reducing conditions.     

Fingerprinting Hydrocarbons in a Contaminated Soil from an Italian Natural Reserve and Assessment of the Performance of a Low-Impact Bioremediation Approach

An environmentally friendly procedure suitable to restore a protected area was evaluated at laboratory scale. Soil contaminated by high molecular weight (C > 10) aliphatic hydrocarbons and by chromium was withdrawn from the study site and a qualitative study of soil hydrocarbon components was first performed in order to assess the potential source of contamination. To this aim, a number of characteristic diagnostic ratios of hydrocarbon components were derived by processing chromatographic data, and were used as indicators for distinguishing anthropogenic from natural hydrocarbons. Then, the efficiency of landfarming for soil remediation was tested by comparing the effect of a few selected amendments and by monitoring the fate of chromium. Soil microbial abundance and activity were also evaluated. Results showed that soil hydrocarbons were mainly of anthropogenic origin and land treatment allowed effective degradation by native microbial populations even in the absence of amendments. The investigated procedures had no effect on the mobilisation of chromium that remained in its stable form of Cr(III). Conventional land treatment may therefore be an effective and safe procedure for the removal of hydrocarbons even in the presence of chromium, and may be applied to areas where low-impact procedures are strictly required.