Chromium and nickel contents and their verification of source in serpentinitic soils

• Main Authors: Hsu Wen-Ming, 許文明
• Other Authors: Hseu, Zeng-Yei
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/09055346860340586112

博士 === 國立屏東科技大學 === 環境工程與科學系所 === 101 === Serpentinites were derived from ultramafic igneous rocks through hydrothermal alteration, which original rocks are island silicate framework and high in Fe and Mg. Serpentinites are weakly resistant in weathering and characterized with high Mg and low Ca and abundant levels of Cr and Ni.The serpentinitic soils are characterized low Ca/Mg ratios and large amounts of Cr and Ni. These heavy metals are not produced from human activities in serpentine soils, but may have adverse effects on eco-environment and human health. This study collected nine soil profiles from Japan and six soil profiles from eastern Taiwan which totally are 95 horizon soil samples. Total and DTPA extraction were performed for chromium and nickel measurement. Experimental results indicates that the Japanese pedons were low weathered compared to Taiwanese ones due to the low Ca/Mg ratios in the Japanese soil samples. However, total contents of Cr and Ni in all soils were much higher than non-serpentine soils, and the metal levels in some of them were over the control standards of Taiwan. Regarding the metal fractionation, Cr and Ni were mainly from the mineral lattices, and thus were concentrated in the residual fractions. The mobility sequence followed as Ni > Cr. With respect to DTPA extractable amount, Ni was higher than Cr. The difference in the DTPA extraction between metals was corresponding to the results of lability evalauted by sequential extraction; however, Cr is hardly absorbed by plant. The soil DTPA extraction effectiveness of Cr and Ni concentrations were much lower than the total contents. However, the effectiveness of chromium and nickel and exchangeable Ca//Mg ratio was negatively correlated significantly. This means that the gradual loss of exchangeable Mg with soil weathering. The effectiveness of the Cr and Ni concentrations will be reduced because of the fixation by iron oxides. This phenomenon can not be discerned in artificially contaminated soils to support the verification of Cr and Ni sources for serpentinitic soils.