| 摘要: |
| 以蒸馏法为基础, 研究了适合海水中铵盐稳定氮同位素分析的预处理方法。对蒸馏法预处理过程中的最佳蒸馏时间、沸石的选取、铵盐最适浓度范围等分别进行改进和优化, 获得稳定、高效的海水中铵盐氮稳定同位素分析预处理方法。结果表明: 最佳蒸馏时间为50 min, 铵盐的回收率为(97±5.8)%。测定了不同沸石对不同浓度氨氮的吸附率, 筛选出酸性条件下铵氮吸附效率较高且稳定的康华科技沸石; 确定铵盐的最佳适用浓度范围为2～10 μmol/L, 在该浓度范围内氮回收率94%～99%,氮分馏系数为0.1‰～0.8‰。将此方法应用于长江口海域水样分析, 结果表明, 这一方法可以应用于河口中铵盐的氮同位素分析, 能够为河口中溶解态氮的来源及循环机理等研究提供有效信息。 |
| 关键词: 铵盐 稳定氮同位素 蒸馏法 河口 预处理方法 |
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| 基金项目:国家自然科学基金项目(41276116); 国家基金委创新研究群体科学基金资助项目(41121064); 国家基础研究规划973 项目(2010CB428706) |
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| Pretreatment method for nitrogen isotopic composition determination of dissolved ammonium-nitrogen in estuarine waters |
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| Abstract: |
| A pretreatment method was developed for determination of nitrogen isotopic composition in ammonium based on the rapid steam distillation method. Ammonium was enriched by distillation in alkaline environment and collected on zeolite. The stable nitrogen isotope ratio in dissolved ammonium was obtained by detecting the filtered and dried zeolite. The optimal distillation time, appropriate zeolite, and optimal concentration range of NH4Cl were characterized. The optimal distillation time was 50 min and the average recovery of samples was (97±5.8)%. The optimality zeolite was determined by measurement of the adsorption efficiency of different zeolites under acid conditions. The optimal concentrations of ammonium was 2～10 μmol/L with a ammonium recovery rate of 94%～100%, and the isotopic fractionation was 0.1‰～0.8‰. This method was successfully applied to samples collected from the Changjiang River estuary. The method is suitable for δ15N analysis of dissolved ammonium in seawaters, and could provide valuable information about the source and cycle mechanism of dissolved nitrogen in estuary waters. |
| Key words: ammonium stable nitrogen isotope distillation estuary pretreatment |
