土壤铵态氮中氮稳定同位素比值测定前处理方法优化研究  

Optimization of Pretreatment Methods for Nitrogen Stable Isotope Ratio Analysis in Soil Ammonium Nitrogen

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 李春勇 王久荣[1] YUAN Hongzhao;HE Zhen;ZHANG Liping;GENG Meimei;XU Liwei;CHEN Wen;PENG Can;LI Chunyong;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》2023年第2期129-135,共7页Chinese Journal of Inorganic Analytical Chemistry

基　　金：国家自然科学基金面上项目(42177330,41771334,41771337);湖南省自然科学基金面上项目(2020JJ4655)。

摘　　要：土壤氮素在土壤养分供给和植物生长发育中起着重要作用。利用氮稳定同位素自然丰度或富集标记技术,开展土壤氮循环转化、化肥利用效率和生物有效性等方面的研究,对NH_(4)^(+)-N同位素比值测定提出了更高要求。在前人基础上,开发了一种快速高通量的铵态氮蒸馏分离方法,并使用次氯酸盐替代了次溴酸盐,优化了铵态氮化学转化条件,将转化效率由原方法的25%左右,提高至60%以上。利用新建立的前处理方法结合气体预浓缩装置与稳定同位素质谱仪(PreCon-IRMS)联用系统,分析了不同浓度条件下自然丰度、15 N富集和标记的NH_(4)^(+)-N标准溶液中的氮稳定同位素比值。结果表明,新的反应体系下,当铵态氮浓度为0.5μmol/mL及以上时,所有NH_(4)^(+)-N标准样品均能获得较理想的分析精度,其中自然丰度和15 N富集标准溶液的NH_(4)^(+)-N的δ15 N的精度可控制在0.5‰以内,而15 N标记的标准溶液的15 N atom%测试精度为0.001 atom%~0.006 atom%(CV在0.1%~0.3%)。所有NH_(4)^(+)-N标准样品的15 N测定值与参考值一致,无分馏现象发生。将方法应用于两种不同土地利用类型的旱地和稻田土壤浸提液中NH_(4)^(+)-N稳定同位素丰度的测定,也可获得较好的重现性(CV<0.5%),与原方法测定结果基本一致,且精度更优。优化后的前处理方法操作简单,耗时短,重复性好,适用于土壤溶液铵态氮15 N丰度测定的快速、批量前处理。Nitrogen in soil plays an important role in soil nutrient supply and plant growth.Therefore higher requirements for the determination of NH_(4)^(+)-N isotope ratio is put forward when using nitrogen stable isotope natural abundance or enrichment labeling technology to carry out research on soil nitrogen cycle transformation,fertilizer utilization efficiency and bioavailability.On the basis of predecessors,a rapid and high-throughput ammonium-nitrogen distillation separation method was developed.Furthermore,the chemical conversion condition of ammonium nitrogen was optimized by using hypochlorite instead of hypobromite.Finally,the conversion efficiency was increased from 25%to 60%.Nitrogen in natural abundance,15 N enrichment and labeled NH_(4)^(+)-N standard solution under different concentration conditions were analyzed by using the newly developed pretreatment method combined with the gas preconcentration device and stable isotope mass spectrometer(PreCon-IRMS)system.The results showed that under the new reaction system,all NH_(4)^(+)-N standard samples obtained ideal analytical precision when the concentration of ammonium nitrogen was 0.5μmol/mL and above.Among them,the accuracy ofδ15 N of the natural abundance and enriched standard solution were controlled within 0.5‰,while the test accuracy of 15 N atom%of 15 N-labeled standard solution was 0.001 atom%-0.006 atom%(CV was 0.1%-0.3%).At the same time,the 15 N values of all NH_(4)^(+)-N standard samples were consistent with the reference values,and no fractionation occurred.The method was applied to the determination of NH_(4)^(+)-N stable isotope abundances in soil extracts from two different land types of dryland and paddy fields,and good reproducibility(CV<0.5%)were obtained,which was basically the same and more accurate as that of the original method.Overall,the optimized pretreatment method has the advantages of simple operation,short time consumption and good repeatability and is suitable for rapid and batch pretreatment for determination of 15 N abun

关 键 词：铵态氮 氮同位素 稳定同位素质谱仪 蒸馏 化学转化N_(2)O法 次氯酸盐 

分 类 号：O657.63[理学—分析化学] TH843[理学—化学]