Our study examines nitrogen sources and transformations in Xiamen Bay, where eutrophication has increased due to higher nitrogen levels. By analyzing dissolved organic matter (DOM) and nitrate stable isotopes (δ15N-NO3−and δ18O-NO3−), the study finds that nitrate in low salinity areas is influenced by freshwater-seawater mixing and biogeochemical processes, while in high salinity areas, it is mainly affected by physical mixing. Bayesian mixing model (MixSIAR) results show that the primary nitrate sources are fecal matter and sewage, followed by atmospheric deposition. During the high flow period, DOM may facilitate nitrogen transformation and release through processes such as degradation or mineralization. In contrast, during the low flow period, the system is mainly influenced by the physical mixing of saline and freshwater. Studies have shown that DOM can indicate the biogeochemical intensity in water bodies, further identifying the main factors influencing the distribution and transformation processes of nitrate content, providing a basis for mitigating eutrophication in estuarine areas.

中文翻译：

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基于 DOM 和稳定同位素组成的富营养化河口带氮源和转化过程的探索


我们的研究考察了厦门湾的氮源和转变，由于氮水平较高，那里的富营养化加剧。通过分析溶解有机物 （DOM） 和硝酸盐稳定同位素（δ15N-NO3- 和 δ18O-NO3−），研究发现，低盐度地区的硝酸盐受淡水-海水混合和生物地球化学过程的影响，而在高盐度地区，硝酸盐主要受物理混合的影响。贝叶斯混合模型 （MixSIAR） 结果表明，主要硝酸盐来源是粪便和污水，其次是大气沉积。在高流量期间，DOM 可能通过降解或矿化等过程促进氮的转化和释放。相比之下，在低流量期间，系统主要受盐水和淡水的物理混合的影响。研究表明，DOM 可以指示水体中的生物地球化学强度，进一步确定影响硝酸盐含量分布和转化过程的主要因素，为缓解河口地区富营养化提供依据。