氮氧同位素示踪南昌秋冬季降水中NO3-来源及其贡献

为确定南昌市秋冬季降水中硝酸盐来源及贡献，于2016年9月1日至2017年2月28日对南昌地区雨水进行采集，分析了其化学组成及NO₃^-同位素组成并利用贝叶斯混合模型对NO₃^-四种潜在来源贡献进行计算.结果显示NO₃^-浓度范围为7.3~99.5μmol/L，平均值为36.1μmol/L；δ¹⁵N-NO₃^-变化范围为-6.0‰~+8.3‰，平均值为-0.8‰，两者均呈现冬季高秋季低的变化趋势.NO₃^-浓度季节性变化可能是受到降雨量等因素的影响，而δ¹⁵N-NO₃^-变化可能是冬季降水中机动车尾气排放偏高和秋季降水中煤燃烧来源偏高双重因素作用的结果.同位素及贝叶斯混合模型源解析结果表明，南昌市降水中NO₃^-主要来源于生物质燃烧（32.5%）、机动车尾气排放（30.8%）和煤燃烧（23.1%），三者贡献超过86%；而机动车尾气排放和生物质燃烧释放均超过30%，这可能与近年来机动车快速增加和秋冬季野外生物质大量燃烧有关.煤燃烧虽然也是重要来源，但相对生物质燃烧和机动车尾气排放较小，这可能与近年我国减排措施有关.

Tracking the source and contribution of NO3- in precipitation in Nanchang in autumn and winter by dual isotope

Rainwater was collected from September 1, 2016 to February 28, 2017 in Nanchang, as well as stable isotope of nitrate (δ¹⁵N) and chemical compositions of rainwater were analyzed. The results showed that the concentration of NO₃^- ranged from 7.3 to 99.5μmol/L, and the mean is 36.1μmol/L; the δ¹⁵N of NO₃^- ranged from -6.0‰ to +8.3‰, and the mean is -0.8‰. Combined with chemical composition and isotope analysis, it is shown that NO₃^- was mainly affected by the region and mainly comes from biomass burning, traffic, coal combustion while biological soil is the secondary source in the sampling period. Bayesian mixing model (MixSIA) which took account of the isotope fractionation wes used to make precise estimations of the contribution of different sources. The results showed that the contribution of biomass burning emissions, traffic and coal combustion was more than 86%. However, in this case, the contribution of biomass burning emissions and traffic was more than 63%, and the coal combustion was only 23.1%, which indicated that a necessity to control NO_x from traffic and biomass burning strictly to reduce air pollution.