ANALYZING CHEMICAL SPECIATION OF NICKEL IN TAILING AND FARMING SOILS IN A Pb/Zn MINING ZONE IN THAI NGUYEN PROVINCE

Abstract

To fully and overall evaluate the contaminated level of heavy metals, it is essential to analyze their chemical speciation. The Ni concentration in 12 soil samples, including tailing samples and farming soils collected in Pb/Zn mining in Thai Nguyen province, was analyzed using inductively coupled plasma mass spectrometry (ICP-MS). Chemical fractions of Ni in the soil were extracted following Tessier’s sequential extraction procedure. Geo-accumulation index (Igeo) and risk assessment code (RAC) were applied to assess the pollution level of Ni in the soil. The results show that Ni existed chiefly in the tailing samples in the order of residue (F5) > Fe/Mn oxides (F3) > carbonate (F2) > exchangeable (F1) ~ organic matters (F4), while it was mainly in the sequence of F5 > F2 > F3> F4 > F1 in the farming soil. Igeo values of Ni were minus (Igeo < 0), indicating that the soil samples had no contamination of Ni. In contrast, RAC values showed that the Ni concentration of the soil samples was in the range of low risk to high risk (10% < RAC < 30%), and three of the seven farming soils were in the level of high risk (RAC > 30%).