Geochemical assessment of metal transfer from rock and soil to water in serpentine areas of Sabah (Malaysia)

The mobility of metals in ultramafic rock–soil systems and metal contamination in serpentine soils were investigated from the Ranau area in Sabah, East Malaysia. Metal concentrations were analysed after division into seven operationally defined fractions by selective sequential extraction (SSE). Geochemical studies showed that the soils are exceptionally high in Cr (95%) residing in refractory residual fractions. Metal speciation studies will shed further light on toxicities in the Malaysian ultramafic tropical environment, reconciled against elemental metal tenure, adopted by common standards

Control of nickel availability by nickel bearing minerals in natural and anthropogenic soils

The aim of this paper was i) to determine the Ni-bearing minerals and localize Ni in natural and contaminated Ni-rich soils, ii) to characterize Ni availability with isotopic exchange kinetics (IEK) and iii) to study its interactions with soil mineralogy and characteristics along a gradient of weathering intensity. We sampled 16 soils varying from a recently exposed surface serpentinite in cold regions, to Ferralsols (laterites) from a humid tropical climate including two highly contaminated soils (Ni industry). The minerals identified ranged from primary minerals to secondary phyllosilicates and lastly to Mn/Fe oxides, according to weathering intensity. Primary minerals inherited from the parent materials and secondary phyllosilicates formed in low leaching conditions had concentrations of Ni similar to the rock (0.2-0.3%). When compared to other secondary minerals, Fe oxides displayed slight Ni enrichment in moderate leaching conditions (0.4-0.8%) up to 10-fold enrichment in highly weathered Ferralsols (4-6%). Full characterization of the three factors of Ni availability in soils: the intensity (C-Ni), the quantity (E-t) and the capacity (CF) factors was achieved with IEK. For most of the soils, C-Ni and E-t varied conjointly: elevated values of these two parameters were found in soils dominated by both phyllosilicates and amorphous Fe oxides (high exchange capacity); low values were found in soils with significant amounts of well-crystallized Fe oxides (high retention capacity). In the case of anthropogenic origin, control of soil Ni availability also depends on the type of Ni-bearing minerals