使用多种改性方法对几种国产天然沸石进行改性处理，提高其铵氮吸附率，制备符合海水硝酸盐氮同位素预处理要求的沸石。发现重力筛选可提高沸石铵氮吸附率16%以上，钠改性及酸改性后钠改性可提高沸石铵氮吸附率80%以上，微波改性和超声波改性均可进一步提高沸石铵氮吸附率。改性处理后，几种沸石在酸性条件下对低浓度铵氮吸附率达90%以上，其氮同位素分馏较美国UOP沸石分馏系数更小，且更稳定。改性后的国产沸石更适于海水硝酸盐氮同位素预处理。应用改性后沸石对长江口海域硝酸盐水样进行了分析，结果表明，改性后沸石可以应用于海水中溶解态硝酸盐的氮同位素分析，为海水中溶解态氮的来源问题及循环机理研究等提供了有效信息。% Several Chinese natural zeolites were modified with multiple methods to increase their ammonium ad-sorption efficiency for nitrogen isotope analyses. The absorption efficiency of zeolites could be increased 16%and 80% after gravity selection and sodium-involved chemical modification respectively. Micro-wave and ultrasound treatments both further increased the ammonium adsorption efficiency. With our modifications, the adsorption effi-ciency for low-concentration ammonium reached 90%or higher under acidic environments. Nitrogen isotope frac-tionation factors of the modified Chinese zeolites were lower and more homogeneous than those of UOP zeolite. Consequently, the modified Chinese zeolites are ideal tools for nitrogen isotope analysis of nitrate in seawater. The modified Chinese zeolites have been applied to analyze water samples collected from the Changjiang River estuary. The analytical results indicated that they are suitable forδ15N analysis of dissolved nitrate in seawaters. Meanwhile, they could provide valuable information about the sources and cycle mechanism of dissolved nitrogen in estuary waters.
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