| 其他摘要 | Due to the development of analytic technology and in particularly, the emergence of instruments of MC-ICPMS during the end of last century, it has become truth to determine transition metal (Cu, Fe, Zn) isotopes and other non-tradition isotopes (e.g. Li, Se, Cd, Mo etc.) accurately. So applied studies of these isotopes have been popular in science studies now. Among these isotopes, as one of the new tool of isotope technology, Zinc isotope has been applied widely in the fields of geochemistry, environment science, deposit geoscience, oceanography, biology and so on. However, nowadays, reports of Zinc isotope studies about rock-soil-plant system in typical Karst area have not been found yet. Therefore, such work is to be developed in this thesis. The purpose of this study is: 1) to complement data of Zinc isotope composition in such source, and 2) to explore the main factors which lead Zn isotopes of soils and plants to fractionate in this area. This work will be used to supply theory basis for Zn isotope application in rock-soil-plant system in karst area. In this thesis , the general method of Zn isotope analysis has been improved properly. Higher analytic efficiency has been achieved by using this improved method. Baiyi district in Wudang and Wangjiazhai district in Qingzhen in Guiyang city (locates Karst zone in southwest China) were chosen as studied areas. Samples (rocks, soils, plants) of five soil profiles (yellow soil and limestone soil) were collected from there. Zn isotope compositions were analysed by adopting the improved method.The main conclusions are summarized as follows: 1. The improved purification condition of Zn is described here: AGMP-1M resin (200-400mesh, Cl- style) was chosen as anion exchange resin. 1.0mol/L HCl+0.001% H2O2 solution was used to wash matrix and impurity which can interfere Zn isotope measurement, 0.5mol/L HNO3 solution was used to elute Zn from resin after other elements was washed out. The new procedure can purify Zn effectively with a recovery yield close to 100%. There is no Zn isotope fractionation during the process of the purification. The results of three standard samples are consistent with their recommendatory data within the area of uncertainty.The method is charactered of low consumption of reagent and time, and it is adapted to chemical preprocess for bulk samples. 2. The Zn isotope composition of rocks and soils in five profiles has been precisely measured. In two yellow soil profiles, the δ66ZnIRMM show narrow varied range from -0.26 to 0.09‰ for soil samples, -0.07 to 0.02‰ for rocks hosted in soil, 0.24‰ for basal rocks in BY-I section. The δ66ZnIRMM show the same as range in QZ-III section from -0.19 to 0.10‰ for soil samples, -0.06 to 0.23‰ for rocks hosted in soil. Rocks hosted in yellow soil yield heavier Zn isotopic composition than that of soil at the same depth in two stuied sections. In three limestone soil profiles, the δ66ZnIRMM value of soil samples also show narrow range from -0.17 to 0.17‰ in BY-II section，-0.15 to 0.08‰ in QZ-I section，-0.02 to -0.26‰ in QZ-II section，respectively. The characteristic of Zn isotope variation is similar in the same kind of soil prof ile, yet there are their own traits between different kinds of soil profiles.The factors that control Zn isotope fractionation of rocks and soils in this area may be the process of dissolution , sorption , precipitation and organic chelate which affect together. 3. The Zn isotope composition of plants in the five profiles has been obtained. The δ66ZnIRMM of ferns yield wide vierid range from -0.05‰ to 0.45‰ in the five profiles. The larger varied scale of δ66ZnIRMM (-0.77‰ to 0.32‰) is preserved in other plants from five stuied sections. Compare to surface soil, leaves of ferns and pachyrhizus commonly enrich heavy Zn isotope. In contrast, other plants deplete heavy Zn isotope. Based on the study reports of Zn isotope fractionation mechanism in plants, Zn uptake by plants and its translocation in |
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