基于热转换元素分析同位素比质谱法研究水样中有机物对氢稳定同位素比值的影响

Effect of Organic Matter in Water Samples on the Hydrogen Stable Isotope Ratio Determination by Thermal Conversion/Elemental Analysis-Isotope Ratio Mass Spectrometry

在研究水文水资源方面,水中氢稳定同位素比值(δ^2H)是一项重要的检测参数,它的变化规律可以用于识别和量化水分来源、揭示水循环演化过程及形成机理,因此促进了水中δ^2H检测技术的发展。热转换元素分析同位素比质谱法(TC/EA-IRMS)测定氢稳定同位素具有高效、准确的特点,适合检测含有机物的水样。本文以乙醇为例,利用TC/EA-IRMS检测方法,探究水样中有机物含量对δ^2H值的影响。通过配制不同体积比的乙醇-水溶液,测定溶液的δ^2H值,建立了乙醇体积比与δ^2H值的线性方程,相关系数(R2)可达0.9996,说明水样中有机物会使δ^2H值产生线性变化,随着有机物含量增加,水样测定的δ^2H值逐渐向有机物的δ2H值方向偏移。利用该线性关系在已知有机物δ^2H值和体积比的条件下,可以对样品中H2O的δ^2H值进行修正。以乙醇实验为例,其修正结果与真值的相对误差为1.7%,通过修正可以得到真实水样中水分子的δ^2H值,有助于准确掌握水循环的状态和规律。同时,利用有机物与δ2H值的线性关系也可以对有机物进行溯源,在模拟溯源乙醇的实验中其溯源的δ2H值与真值相对误差仅为0.4%,说明该线性关系在有机物溯源方面具有良好的应用前景。

BACKGROUND: In the study of hydrology and water resources, the hydrogen stable isotope ratio (δ^2H) of water is an important detection parameter, and its changing patterns can be used to identify and quantify the source of water, and reveal the evolution process and formation mechanism of the water cycle. Therefore, the accuracy of δ 2H value is very important, which promotes the development of isotope detection technology. High-temperature combustion pyrolysis-element analysis isotope ratio mass spectrometry is a highly efficient and accurate method for the determination of hydrogen isotopes. It is suitable for the detection of water samples containing organic matter. OBJECTIVES: To explore the influence of organic matter content in water on the hydrogen stable isotope ratio (δ^2H) and establish a relationship curve between them. Use the relationship to modify the δ^2H value of H2O and trace the organic source in organic polluted water. METHODS: Thermal conversion/elemental analysis-isotope ratio mass spectrometry (TC/EA-IRMS) was used as the main detection method. Ethanol water samples with different volume ratios ( r ) were prepared, and the δ 2H values of the samples were determined by TC/EA-IRMS. Taking r and δ^2H as variables, the curve relationship and equation were established. RESULTS: A good linear relationship was established by using the ethanol content and the δ^2H value as variable with R^2 of 0.9996, indicating that the organic matter in the water sample will linearly change the δ^2 H value. As the organic matter content increased, the δ^2 H value measured by the water sample gradually shifted toward the δ^2H value of the organic matter. Using this linear relation, the δ^2H value of H2O in the sample can be corrected when the volume ratio of the organic matter is known. Taking the ethanol experiment as an example, the relative error between the corrected result and the true value was 1.7%. By correcting, the δ^2H value of the water molecules in the water sample can be obtained, which helped to accurately understand the state and regularity of the water cycle. At the same time, the linear relationship can also be used to trace the source of the organic matter. In the ethanol experiment that simulated the traceability of the source ethanol, the relative error was only 0.4%. CONCLUSIONS: The linear relationship between organic matter and δ^ 2H has a good application prospect in organic matter tracing.