Ion‐exchange resin and denitrification pretreatment for determining δ15N‐NH4+, δ15N‐NO3-, and δ18O‐NO3- values
Ion‐exchange resin and denitrification pretreatment for determining δ15N‐NH4+, δ15N‐NO3-, and δ18O‐NO3- values
复制标题
用于测定 δ15N-NH4+、δ15N-NO3- 和 δ18O-NO3- 值的离子交换树脂和反硝化预处理
DOI：
10.1002/rcm.9027
复制
发表时间：
2021
影响因子：
2
通讯作者：
Suto Nana
中科院分区：
文献类型：
--
作者：
Kawashima Hiroto;Yoshida Otoha;Suto Nana
目前还没有一种高灵敏度的方法可以同时测量颗粒物中硝酸根离子（NO3−）的δ 15 N和δ 18 O值以及铵离子（NH 4+）的δ 15 N值。在本研究中，我们探索了一种结合使用阴离子交换树脂和净化细菌来进行这种测量的方法。方法使用次溴酸盐和净化细菌法获得的样品的δ 15 N-NH 4+值通过同位素比质谱法进行测量。进行了试验（流速、穿透和酸浓度的影响），以验证使用AG 1-X8阴离子交换树脂进行NH 4+测量和NO3−富集时NO3 −的去除。对于气溶胶样品，采用优化的方法测量了大气颗粒物的δ 15 N-NO3-、δ 18 O-NO3-和δ 15 N-NH 4+值结果用1-6 mol/L HCl萃取，样品流速为1-2 mL/min，总阴离子量小于2.2 mmol，在浓度测试中发现与试剂值非常接近。δ 15 N-NH 4+和δ 15 N-NO3 −值的精确度和准确度在所有情况下都小于1‰。此外，δ 18 O-NO3 −值的准确度小于1.4‰，总体上可以接受。δ 15 N-NH 4+，δ 15 N-NO3-，和δ 18 O-NO3-值在6个PM2.5样品是类似于那些在以前的研究中报道的。结论我们提出的方法去除阴离子使用AG 1-X8树脂，同位素分析使用微生物，并浓缩样品中含有低浓度的NO3-将使它能够进行高精度和准确的分析容易和廉价。这些方法不仅适用于气溶胶，而且适用于来自不同地点的样品，如河流，海洋和南极洲。
RationaleThere has never been a highly sensitive method for simultaneously measuring the δ15N and δ18O values of nitrate ions (NO3−) and the δ15N values of ammonium ions (NH4+) in particulate matter using denitrifying bacteria. In this study, we explored a method that combines use of an anion‐exchange resin and denitrifying bacteria to make such measurements.MethodsThe δ15N‐NH4+values of samples obtained using the hypobromite and denitrifying bacteria method were measured by isotope ratio mass spectrometry. Tests (effect of flow rate, breakthrough, and acid concentration) were conducted to verify the removal of NO3−using an AG1‐X8 anion‐exchange resin for NH4+measurements and the enrichment of NO3−. For aerosol samples, the optimized method was used to measure the δ15N‐NO3−, δ18O‐NO3−, and δ15N‐NH4+values of atmospheric particulate matter (PM2.5, aerodynamic diameter < 2.5 μm).ResultsThe δ15N‐NO3−and δ18O‐NO3−values measured following extraction with 1–6 mol/L HCl, at sample flow rates of 1–2 mL/min, with total anion amounts of less than 2.2 mmol, and in concentration tests were found to be in very close agreement with reagent values. The precisions and the accuracies of the δ15N‐NH4+and δ15N‐NO3−values were in all cases less than 1‰. In addition, the accuracies for the δ18O‐NO3−values were less than 1.4‰ and generally acceptable. The δ15N‐NH4+, δ15N‐NO3−, and δ18O‐NO3−values in six PM2.5samples were similar to those reported in previous studies.ConclusionsOur proposed method for removing anions using AG1‐X8 resin, for isotopic analysis using denitrifying bacteria, and for concentrating samples containing low concentrations of NO3−will make it possible to perform high‐precision and accurate analyses easily and inexpensively. These methods are applicable not only to aerosols, but also to samples from diverse locations such as rivers, oceans, and Antarctica.