Boron And Chlorine Isotopic Chemistry And Study For The Fractionation Mechanism Of Their Isotopes

As an extremely sensitive tracer in geochemistry and environmental science, chlorine and boron isotopic system have been successfully used to study many geochemical processes, such as in the salt lakes, brines and sedimentary environments, paleo-ocean and paleoclimatology, and water contamination. Some new separation methods and instrumental techniques will promote an extending application of chlorine isotope system in a wider field.This dissertation included two parts. The first part was the study on chlorine isotopic chemistry, the second part was the study on the fractionation mechanism of chlorine isotope during the dissolution of NaCl, during the volatilization of HC1 and seawater and on the fractionation mechanism of boron isotope in the sediment of inorganic carbonate in sea facies and land facies.An improved method for extraction and purification of chlorine from natural sample with low-content chlorine was present. The separation and purification of chlorine was carried out using Dowex 50W XX 8 anion resin and 732 anion resin made in Shanghai, China. The results showed that chlorine separation by the ion exchange using Ag-resin, Ba-resin and Cs-resin for isotopic measurement was more effective. It achieved high accuracy of isotopic measurement of chlorine.The factors which can influence on the intensity of Cs₂Cl⁺ ion in the measurement of chlorine isotope was analyzed. The best pH range of loading solution was 2⁷. If the pH value of loading solution was beyond the range, the observed fractionation of chlorine isotope would appear. Within the permittedweight scope of chlorine with l-500μg Cl, the measured chlorine isotopic ratios were irrelative with the loading weight of chlorine. The best ribbon materials for chlorine isotopic measurement were Ta and W.The characteristics of non-reductive thermal ion emission of several carbon nano-materials were studied. Except for C₆0, the others have the efficiency of non-reductive thermal ion emission, which can be fulfilled with the measurement need of chlorine isotope. But the anticipative result was not gotten.The fractionation of chlorine isotope during the dissolution of NaCl was studied systemically. The range of δ³7 C1 was 0.59¹.09%o in saturated Na₂SO₄ solution, 0.19¹.44%o in ethanol solution. Average value of δ³7C1 was 0.80%o in saturated Na₂SO₄ solution, 1.04‰ in ethanol solution. Fractionation factor of chlorine isotope was 1.00029 in saturated Na₂SO₄ solution, which was in accordance to the fractionation factor of chlorine isotope in quick-crystallization, and 0.99951 in ethanol solution, which was identical with the fractionation factor of chlorine isotope in slow-crystallization.The fractionation factors in the volatilization of HCl and seawater were investigated. The chlorine in atmosphere came from that in aerosol above sea which volatized in style of HCl, but chlorine in atmosphere was not from that volatilized from the sea in the style of HCl, maybe from the aerosol or the surface water.In the last, the boron isotopic fractionation factor in sediment of inorganic carbonate of sea facies and land facies was studied. Mg and B content, values of δ¹1B and fractionation factors of boron isotope all become greater with the increase of pH. In the beginning, Fractionation factors of boron isotope was less than 1. but with the increase of pH, Fractionation factors of boron isotope was more than 1. This may be relative with the existing form of boron which co-deposited with CaCO₃.