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铵锌镉还原法测试硝酸盐氮、氧同位素方法研究
尹希杰,杨海丽,郭浩然,陈淳青,崔坤磊
0
(自然资源部第三海洋研究所, 福建 厦门 361005)
摘要:
本研究利用铵锌镉还原法将海水、湖水和自来水水体中硝酸盐转化为N2O气体测试氮、氧同位素, 结果表明当反应体系的pH值在6~8之间, NO3-还原为NO2-的转化率大于95%, NO2-还原为N2O的转化率大于99%。配置5种丰度的硝酸盐氮、氧同位素标样, 将实验结果与理论值绘制校准曲线, 氮同位素校准曲线斜率为0.48, 相关性良好(R2=0.999 8), 5种丰度δ15NN2O标准偏差在0.18‰~0.43‰之间(n=5);氧同位素校准曲线斜率为0.70, 相关性良好(R2=0.999 6), 5种丰度δ18ON2O标准偏差在0.27‰~0.46‰之间(n=5)。铵锌镉还原法与镉柱还原法测定硝酸盐氮、氧同位素结果的精密度和准确度一致, 同时海水、湖水和自来水3种不同类型水样的硝酸盐氮、氧同位素测试数据满足实验要求, 而且在实验流程的简洁性和高效性方面更具优势。
关键词:  海洋化学  铵锌镉法  氮同位素  氧同位素  硝酸盐  氧化亚氮
DOI:10.3969/J.ISSN.2095-4972.2021.04.020
基金项目:自然资源部第三海洋研究所基本科研业务费专项资金资助项目(海三科2016046)
Determination of the nitrogen and oxygen isotopic composition of dissolved nitrate by ammonium zinc cadmium reduction method
YIN Xijie,YANG Haili,GUO Haoran,CHEN Chunqing,CUI Kunlei
(Third Institute of Oceanography, MNR, Xiamen 361005, China)
Abstract:
The ammoniumzinccadmium reduction method was used to convert nitrate to nitrous oxide for nitrogen and oxygen isotopic abundance analysis. In water reaction system with pH between 6 and 8, the efficiencies of nitrate reduction to nitrite were above 95%, and the efficiencies of nitrite to nitrous oxide using sodium azide in acetic acid buffer were higher than 99%. An excellent correlation between the known δ15N and δ18O values of nitrate and the measured δ15N and δ18O values of nitrous oxide exhibited a slope of 0.48 for nitrogen and 0.70 for oxygen, respectively, with both R2 values of 0.999 8. The standard deviations of δ15N of 5 nitrogen compositions of N2O were between 0.18‰ and 0.43‰ (n=5). The standard deviations of δ18O were between 0.27‰ and 0.46‰ (n=5). The results show that the precision and accuracy of the test for determination nitrogen and oxygen isotopes of nitrate are the same with other chemical conversion methods. Meanwhile, the data of nitrate nitrogen and oxygen isotopes of different types of water samples meet the experimental requirements. Furthermore the experimental process is also simpler and more efficient with advantage of lower cost.
Key words:  marine chemistry  ammonium-zinc-cadmium  nitrogen isotope  oxygen isotope  nitrate  nitrous oxide

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