Triple oxygen isotope analysis of nitrate using the denitrifier method and thermal decomposition of N2O
Triple oxygen isotope analysis of nitrate using the denitrifier method and thermal decomposition of N2O
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DOI：
10.1021/ac061022s
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发表时间：
2007-01-15
影响因子：
7.4
通讯作者：
Sigman, Daniel M.
中科院分区：
文献类型：
--
作者：
Kaiser, Jan;Hastings, Meredith G.;Sigman, Daniel M.
与臭氧的相互作用将其异常（非质量依赖性）O-17富集转移到大气氮氧化物和硝酸盐。硝酸盐的O-17异常（Delta O-17）可用于确定大气硝酸盐输入陆地和水生环境，以及研究臭氧在大气活性氮循环中的作用。我们在这里报告了一种在线分析O-17异常的方法，使用一种增菌剂将硝酸盐转化为N2 O，N2 O在800摄氏度的金炉中定量分解为N-2和O-2，然后进行气相色谱分离和O-2同位素分析。该方法需要类似于50 nmol的硝酸盐，比以前的离线热分解方法少2-3个数量级，以实现Δ O-17的0.5%的类似分析精度。没有显著的记忆效应，但需要通过硝酸盐或N2 O参考物质进行校准以进行标度归一化。N2 O分解方法非常适合各种环境中淡水和海水样品中的硝酸盐分析。
Interaction with ozone transfers its anomalous (non-mass-dependent) O-17 enrichment to atmospheric nitrogen oxides and nitrate. The O-17 anomaly (Delta O-17) in nitrate can be used to identify atmospheric nitrate inputs into terrestrial and aquatic environments as well as to study the role of ozone in the atmosphere's reactive nitrogen cycle. We report here on an online method for analysis of the O-17 anomaly, using a strain of denitrifiers to convert nitrate to N2O, which decomposes quantitatively to N-2 and O-2 in a gold furnace at 800 degrees C, followed by gas chromatographic separation and isotope analysis of O-2. This method requires similar to 50 nmol of nitrate, 2-3 orders of magnitude less than previous offline thermal decomposition methods to achieve a similar analytical precision of 0.5% for Delta O-17. There is no significant memory effect, but calibration via nitrate or N2O reference materials is required for scale normalization. The N2O decomposition method is shown to be well-suited for nitrate analysis in freshwater and seawater samples from various environments.