硝酸盐氮同位素反硝化细菌法测试技术的建立

A technique for measuring nitrogen isotopic composition of nitrate using the denitrifier method

根据实验室条件,建立了反硝化细菌法测试技术,用于地下水和沉积物硝酸盐氮同位素测试。利用国际同位素参考物质和实际样品开展了一系列条件试验。两个国际同位素标准IAEA-N3和USGS34的分析结果显示,δ15N分析具有很好的重复性,精度变化在0.09‰–0.48‰之间,均值为0.25‰;实际样品的δ15N分析也是可重复的,精度优于0.5‰。结果显示我们建立的反硝化细菌法测试技术可用于地下水和沉积物硝酸盐氮同位素测试。利用该技术对一个厚层包气带沉积物硝酸盐氮同位素测试结果显示,在包气带下部δ15N值不存在随深度增加的趋势,指示包气带下部很少反硝化作用发生。

A measurement technique of the denitrifier method, which was developed for seawater isotopic analysis, was established for analyzing nitrogen isotopic composition of nitrate in groundwater and the vadose zone sediments. Experiments were conducted using international isotopic standards of IAEA-N3 and USGS34 and field samples. δ^1^5N analyses of the two isotopic standards showed good reproducibility, with an average precision of 0.25‰ （ranging from 0.1‰ to 0.5‰）. Groundwater and sediment extracts were accurately reproduced, with precisions of better 0.5‰. The results showed that the measurement technique of the denitrifier method could be used for analyzing nitrogen isotopic composition of nitrate in groundwater and sediments. A case study using the technique showed that a thick vadose zone sediment profle had no increase trend of δ^1^5N values in depths below the vadose zone, indicating little denitrification occurrence.