Dongting is one of the largest freshwater lakes in China and is connecting to the Yangtze River.In order to investigate the relationship between the composition of dissolved organic matter(DOM)and dissolved organic carbon(DOC)budget of Lake Dongting and the hydraulic connectivity between rivers and the lake,we collected water samples from the four inflowing tributaries Xiang,Zi,Yuan,and Li,and also the Yangtze River via the three inlets Songzi,Hudu,and Ouchi and only one outlet of Lake Dongting to Yangtze River at Chenglingji in May,July,September,and November 2018,and to investigate the compositional divergence characteristics of Dongting Lake basin DOM in response to river-lake hydraulic connectivity.The study shows that DOM absorption a254 and terrestrial humic-like C1of the input rivers and sole outlet was the highest in July when the inflow discharge to the lake was high.DOC decreased from(2.4±1.3)mg/L at the inlet to(2.1±0.3)mg/L at the outlet,while a254 increased from(9.7±2.2)m-1at the inlet to(10.1±1.7)m-1at the outlet.Dissolved organic carbon(DOC)concentration decreased from(2.4±1.0)mg/L prior to microbial incubation to(2.1±0.9)mg/Lpost microbial degradation,and the highest level of biodegradable DOC(BDOC)was found in the River Li(50.3%).The summed DOC fluxes into the lake in May,July,September,and November were(63.7±43.6)×103 t,(60.1±7.3)×103 t,(27.6±3.6)×103 t,and(31.9±13.9)×103 t,respectively.The results show that Dongting Lake is marginally degraded during the process of intra-lake transport due to the short water retention time of the lake itself,and the composition of DOM sources in the whole lake is greatly influenced by the inflowing discharge in different seasons.
维普
万方数据