School of Marine Sciences, Sun Yat-Sen University, Zhuhai, China.
Third Institute of Oceanography, Ministry of Natural Resources, Xiamen, China.
Mar Pollut Bull. 2024 Jul;204:116528. doi: 10.1016/j.marpolbul.2024.116528. Epub 2024 Jun 3.
Anthropogenic input of excess nutrients stimulates massive nitrous oxide (NO) production in estuaries with distinct seasonal variations. Here, nitrogen isotopic and isotopomeric signatures were utilized to investigate the seasonal dynamics of NO production and nitrification at the middle reach of the eutrophic Pearl River Estuary in the south of China. Elevated NO production primarily via ammonia oxidation (> 1 nM-N d) occurred from April to November, along with increased temperature and decreased dissolved oxygen concentration. This consistently oxygenated water column showed active denitrification, contributing 20-40 % to NO production. The water column microbial NO production generally constituted a minor fraction (10-15 %) of the estuarine water-air interface efflux, suggesting that upstream transport and tidal dilution regulated the dissolved NO inventory in the middle reach of the estuary. Nitrification (up to 3000 nM-N d) played a critical role in bioavailable nitrogen conversion and NO production, albeit with NO yields below 0.05 %.
人为输入过量营养物质会刺激河口地区大量产生氧化亚氮（NO），且具有明显的季节性变化。本研究利用氮同位素和同位素分馏技术，调查了中国南方富营养化的珠江河口中游地区 NO 产生和硝化作用的季节性动态。从 4 月到 11 月，随着温度升高和溶解氧浓度降低，氨氧化作用（> 1 nM-N d）是主要的 NO 产生途径。这种持续富氧的水柱表现出活跃的反硝化作用，对 NO 产生的贡献为 20-40%。水柱微生物 NO 产生一般占河口水-气界面排放通量的一小部分（10-15%），这表明上游输运和潮汐稀释调节了河口中游的溶解态 NO 储量。硝化作用（高达 3000 nM-N d）在生物可利用氮转化和 NO 产生中起着关键作用，尽管其 NO 产率低于 0.05%。
