李小飞,侯立军,刘敏.崇明东滩湿地土壤硝酸盐异化还原成铵过程及其影响因素[J].环境科学学报,2019,39(4):1284-1294
崇明东滩湿地土壤硝酸盐异化还原成铵过程及其影响因素
- Dissimilatory nitrate reduction to ammonium and associated biogeochemical controls in the soils of Chongming East wetland
- 基金项目：国家自然科学基金（No.41701548，41761144062）
- 李小飞
- 1. 福建师范大学湿润亚热带生态地理过程教育部重点实验室, 福州 350007;2. 福建师范大学地理科学学院, 福州 350007
- 侯立军
- 华东师范大学河口海岸学国家重点实验室, 上海 200062
- 刘敏
- 华东师范大学地理科学学院, 地理信息科学教育部重点实验室, 上海 200241
- 摘要：以崇明东滩湿地为研究对象，采用同位素示踪结合泥浆实验，研究了从低潮滩向高潮滩变化的土壤硝酸盐异化还原成铵过程（DNRA）及其影响因素.结果表明，土壤硝酸盐异化还原成铵的潜在速率为0.17~0.71 nmol·g-1·h-1，表现为低潮滩位较高、高潮滩位较低的空间变化特征.相关性分析表明，酸盐异化还原成铵潜在速率与氧化还原电位、可溶性有机碳、硝酸盐和硫化物呈显著相关性.此外，nrfA基因丰度与硝酸盐异化还原成铵潜在速率呈显著相关性.逐步回归分析发现，可溶有机碳和总有机碳是影响硝酸盐异化还原成铵潜在速率和nrfA基因丰度的关键性环境因子，分别贡献了总变异的78.8%和50.3%.通过估算得出，东滩湿地硝酸盐异化还原成铵过程将硝酸盐转化成铵盐的潜力为2.5~10.4 t·km-2·a-1，贡献了长江口每年无机氮输入量的0.68%~2.85%，因此，硝酸盐异化还原成铵过程在控制河口湿地氮赋存方面具有着重要的作用.河口潮汐作用导致的湿地环境特征与有机质和硝酸盐含量的变化影响着硝酸盐异化还原成铵过程，进而对河口湿地生态系统中氮动态产生较大的影响.
- Abstract：In this study, nitrogen isotope tracer combined with slurries incubation experiment was used to investigate spatial distribution and associated biogeochemical controls of dissimilatory nitrate reduction to ammonium in the soils ranging from the low to high intertidal sites in Chongming East wetland. The results indicated that the potential rates of dissimilatory nitrate reduction to ammonium (DNRA) were in the range of 0.17~0.71 nmol·g-1·h-1. DNRA rates highly varied across the sampling sites, and were generally higher in low intertidal sites, and lower in high intertidal sites. DNRA rates were significantly related to Eh, DOC, NO3-, and sulfate, indicating that they crucial factors controlling DNRA activity. In addition, the nrfA abundance showed a strong influence on DNRA rates. Stepwise regression analysis further suggested that DOC and TOC were main factors regulating DNRA rate and nrfA abundance, contributing 78.8% and 50.3% to the total variations, respectively. The amount of nitrate reduction to ammonium performed by DNRA was approximately 2.5~10.4 t·km-2·a-1, accounting for roughly 0.68%~2.85% of total annual inorganic nitrogen flux transported into the Yangtze Estuary, suggesting that DNRA plays a crucial role in controlling the nitrogen fate in estuarine wetland. Overall, these results indicate that the variations in environmental conditions and organic matter and nitrate availability induced by the tidal fluctuation affect DNRA process, which further plays an important role regulating the nitrogen dynamics in estuarine ecosystems.
