傀儡湖沉积物-水界面硝酸盐异养还原过程研究

Dissimilatory nitrate reduction processes at the sediment-water interface in Lake Kuilei

反硝化(DNF)和硝酸盐异养还原为氨(DNRA)是水域生态系统中硝酸盐异养还原的2个主要过程.DNF和DNRA之间的竞争控制着硝酸盐在水域生态系统中的异养还原方式和最终归趋.选取太湖流域的傀儡湖为研究对象,采用室内培养实验和稳定氮同位素示踪技术,考察傀儡湖沉积物-水界面的DNF和DNRA速率及其对硝酸盐异养还原过程的贡献.结果显示,沉积物表现为NH_4^+-N的源和NO_3^--N的汇,潜在DNF速率为18.89~54.00μmol/(kg·h)[均值(36.39±3.86)μmol/(kg·h)],DNRA反应速率为1.02~5.89μmol/(kg·h)[均值(3.21±1.15)μmol/(kg·h)].DNF与沉积物有机质含量和含水率存在显著的正相关关系,DNRA与沉积物需氧量(SOD)之间存在相关性.反硝化是傀儡湖中硝酸盐异养还原的主导过程,贡献率为84.23%~96.90%,而DNRA过程只占3.10%~15.77%.与海洋河口区域相比,淡水湖泊生态系统中DNRA速率和DNRA在硝酸盐异养还原中所占的比重均较小.

Denitrification（DNF） and dissimilatory nitrate reduction to ammonium（DNRA） are two major processes of dissimilatory nitrate reduction in aquatic ecosystems. The competition between DNF and DNRA controls the dissimilatory reduction pattern and the final fate of nitrate in aquatic ecosystems. In this study, DNF and DNRA processes at the sediment-water interface（SWI） in Lake Kuilei（a shallow freshwater lake in Lake Taihu basin） were studied by using the stable nitrogen isotope tracing method. DNF and DNRA rates at the SWI and potential contributions to the total dissimilatory nitrate reduction from both processes were quantitatively estimated. Results showed that sediments served as the source of NH4＋-N and the sink of NO3--N in Lake Kuilei. DNF and DNRA rates at the SWI were 18.8854.00 μmol/（kg·h）（mean value of 36.39±3.86 μmol/（kg·h）） and 1.025.88 μmol/（kg·h）（mean values of 36.39±3.86, 3.21±1.15 μmol/（kg·h））, respectively. The DNF rate was significantly correlated with the sediment organic matter and the water content, while the DNRA rate was correlated with the sediment oxygen demand（SOD）. Moreover, DNF was confirmed as the predominant process of dissimilatory nitrate reduction process in Lake Kuilei, which contributed 84.2396.90% to the total dissimilatory nitrate reduction compared with only 3.10%15.77% from DNRA. Compared with marine and estuarine areas, lower DNRA rates and fewer DNRA contributions to the total nitrate reduction were observed in freshwater lake ecosystems.