水中硝酸盐氮稳定同位素比值测定前处理方法的优化  

Optimization of Pretreatment Methods for Nitrogen Isotopic Analysis of Nitrate in Water

作　　者：袁红朝[1,2] 贺珍 张丽萍 耿梅梅[1] 许丽卫[1] 陈闻[1] 彭灿 唐思宇 王久荣 YUAN Hongzhao;HE Zhen;ZHANG Liping;GENG Meimei;XU Liwei;CHEN Wen;PENG Can;TANG Siyu;WANG Jiurong(CAS,Key Laboratory of Agro-Ecological Processes in Subtropical Region,Institute of Subtropical Agriculture,Changsha,Hunan 410125,China;Hunan Provincial Key Laboratory of Agricultural Ecological Engineering,Changsha,Hunan 410125,China)

机构地区：[1]中国科学院亚热带农业生态研究所,亚热带农业生态过程重点实验室,长沙410125 [2]农业生态工程湖南省重点实验室,长沙410125

出　　处：《中国无机分析化学》2024年第7期889-895,共7页Chinese Journal of Inorganic Analytical Chemistry

基　　金：国家自然科学基金资助项目(42177330,U21A2007);中国科学院技术支撑人才项目(2022000014);中国科学院仪器功能开发项目。

摘　　要：水体中过量的硝酸盐会导致严重的水生生态恶化和环境污染问题。氮稳定同位素技术为水体污染来源的判断及水生系统氮素转化机理研究提供了强有力的工具。在前人基础上,通过开发Cu^(2+)-Cd复合催化结合超声波辅助加速反应,优化硝酸盐氮同位素比值测定前处理方法。考察了Cu^(2+)添加量、超声功率以及反应时间变化对NO_(3)^(-)-N转化生成N_(2)O气体及其氮同位素比值的影响,在单因素实验基础上采用正交实验优化得到了最佳反应条件,并采用不同^(15)N同位素比值的KNO_(3)标准溶液结合气体预浓缩装置与稳定同位素质谱仪联用系统对新方法进行了验证。新方法单次反应体系中氮最低量为1.0μg,其中自然丰度和高丰度样品δ^(15)N分析精度小于1‰,富集样品的^(15)N分析精度可达0.1 atom%以内(CV<1%);且所有标准样品的^(15)N测定值与参考值基本一致。将优化后的方法应用于不同来源水样中硝酸盐氮稳定同位素比值测定,均可获得较好的精度,较原方法提高了前处理效率,且精度更优。建立的方法准确可靠,操作简单,耗时短,适用于水中硝酸盐氮稳定同位素比值测定的批量、快速前处理。Excessive nitrate in water can lead to serious ecological degradation and environmental pollution.The nitrogen stable isotope technology provides a powerful tool for the identification of water pollution sources and the study of nitrogen transformation mechanisms in aquatic systems.On the basis of previous studies,a pre-treatment method of Cd-Cu^(2+)catalytic compound combined with ultrasonic assisted acceleration reaction was developed for nitrogen isotopic analysis of nitrate in water.The effects of Cu^(2+)addition,ultrasound power,and reaction time on the conversion of NO_(3)^(-)-N to N_(2)O gas and its nitrogen isotope ratio were investigated.Based on single factor experiments,the optimal reaction conditions were optimized using orthogonal experiments.The new method was validated using KNO_(3) standard solutions with different ^(15)N isotope ratios combined with a gas pre concentration device and a stable isotope mass spectrometer system.The minimum nitrogen content in a single reaction system of the new method was as low as 1.0μg,with natural and high abundance samples δ^(15)N analysis accuracy were within 1‰.The ^(15)N analysis accuracy of enriched samples can reach within 0.1 atom%(CV<1%).And the ^(15)N measurement values of all standard samples were basically consistent with the reference values.The optimized method had been applied to analyze stable isotope ratios of nitrate nitrogen in various water samples from different sources and achieved good accuracy.The comparison of the analytical data from the two analytical systems indicated that the new method improved pre-treatment efficiency and had better accuracy compared to the original method.Overall,the established method has the advantages of accurate,reliable,easy to operate and time-consuming,suitable for batch and rapid pre-treatment of N stable isotope ratio analysis of nitrate in water.

关 键 词：水体 硝酸盐 氮同位素测定 前处理 超声波辅助 

分 类 号：O657.32[理学—分析化学]