Mobility of Ni, Cr and Co in serpentine soils derived on various ultrabasic bedrocks under temperate climate

• Type of parent rock affects the mobility of Ni and Co in serpentine soils.
• Cr is the least mobile element and its mobility does not depend the type of bedrock.
• Mobility of Ni and Co decreases with the degree of metamorphic alteration.
• Metal mobility is controlled by physicochemical and chemical soil proprieties.

Serpentine soil is a common name for soils derived either from igneous peridotites or metamorphic serpentinites. However, differences in mineralogy of these rocks are responsible for some differences between soils occurring on peridotites and serpentinites. In this study, we analyze the mobility of Ni, Cr and Co in six serpentine sites derived from a variety of parent substrates: from partially serpentinized peridotites through serpentinites containing relics of primary minerals and textures to proper serpentinites. The mobility of Ni, Cr and Co, determined using the EDTA extraction, is the highest for Ni whereas Cr is the least mobile element in all soils studied. No relationship between type of parent rock and Cr mobility is found. The lowest proportions of EDTA extractable fractions of Ni and Co (up to 7 and 4% of total concentrations, respectively) are observed in soils derived from proper serpentinites devoid of primary minerals (e.g., olivine, pyroxene) and having non-pseudomorphic texture. The highest proportions of EDTA extractable Ni and Co are noted in soils derived from partially serpentinized peridotite, hornblende peridotite and serpentinite having typical pseudomorphic texture, containing primary Al-rich magnesiochromite (up to 18 and 16% of total concentration respectively). It is therefore justified that type and origin of ultrabasic parent rock affect metal mobility (at least in the case of Ni and Co) in serpentine soils. Furthermore, several soil characteristics (such as pH, total organic C, soil mineralogy) also play an important role in the mobility of Ni, Cr and Co. However, relationships between soil properties and metal availability are more pronounced for soils developed on proper serpentinites than for soils deriving from rocks that experienced less advanced serpentinization.

Figure optionsDownload as PowerPoint slide