Taihu Laboratory for Lake Ecosystem Research, State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing, 210008, People's Republic of China.
Environ Sci Pollut Res Int. 2015 Sep;22(17):12992-3003. doi: 10.1007/s11356-015-4556-x. Epub 2015 Apr 29.
High concentrations of chromophoric dissolved organic matter (CDOM) are terrestrially derived from upstream tributaries to Lake Taihu, China, and are influenced by hydrological conditions of the upstream watershed. To investigate how the dynamics of CDOM in Lake Taihu are influenced by upstream inflow runoff, four sampling cruises, differing in hydrological conditions, were undertaken in the lake and its three major tributaries, rivers Yincun, Dapu, and Changdou. CDOM absorption, fluorescence spectroscopy, chemical oxygen demand (COD), and stable isotope δ(13)C and δ(15)N measurements were conducted to characterize the dynamics of CDOM. The mean absorption coefficient a(350) collected from the three river profiles (5.15 ± 1.92 m(-1)) was significantly higher than that of the lake (2.95 ± 1.88 m(-1)), indicating that the upstream rivers carried a substantial load of CDOM to the lake. This finding was substantiated by the exclusively terrestrial signal exhibited by the level of δ(13)C (-26.23 ± 0.49‰) of CDOM samples collected from the rivers. Mean a(350) and COD in Lake Taihu were significantly higher in the wet season than in the dry season (t test, p < 0.0001), suggesting that the abundance of CDOM in the lake is strongly influenced by hydrological conditions of the watershed. Four components were identified by parallel factor analysis, including two protein-like components (C1 and C2), a terrestrial humic-like component (C3), and a microbial humic-like (C4) component. The contribution percentage of the two humic-like components relative to the summed fluorescence intensity of the four components (C humic) increased significantly from the dry to the wet season. This seasonal difference in contribution further substantiated that an enhanced rainfall followed by an elevated inflow runoff in the lake watershed in the wet season may result in an increase in humic-like substances being discharged into the lake compared to that in the dry season. This finding was further supported by an elevated a(250)/a(365) of CDOM samples collected in the lake in the wet season than in the dry season. Significantly higher mean levels of C3 and a(350) were recorded for CDOM samples collected from River Yincun than those from rivers Dapu and Changdou, differing in seasons, suggesting the significance of terrestrial CDOM input from River Yincun.
高浓度的有色溶解有机物（CDOM）源自中国太湖上游的支流，受到上游流域水文条件的影响。为了研究太湖 CDOM 的动态如何受到上游入湖径流水的影响，在太湖及其三大支流银村河、大浦河和长兜河进行了四次采样巡航，这些巡航在水文条件上有所不同。进行了 CDOM 吸收、荧光光谱、化学需氧量（COD）以及稳定同位素δ(13)C 和 δ(15)N 测量，以表征 CDOM 的动态。从三条河流剖面采集的平均吸收系数 a(350)（5.15 ± 1.92 m(-1))）明显高于湖泊的吸收系数 a(350)（2.95 ± 1.88 m(-1))），表明上游河流向湖泊输送了大量的 CDOM。这一发现得到了从河流采集的 CDOM 样品中所表现出的完全是陆地信号的δ(13)C（-26.23 ± 0.49‰）水平的支持。太湖的平均 a(350)和 COD 在雨季显著高于旱季（t 检验，p < 0.0001），表明流域的水文条件强烈影响了湖泊中 CDOM 的丰度。平行因子分析确定了四个组分，包括两个蛋白质样组分（C1 和 C2）、一个陆地腐殖质样组分（C3）和一个微生物腐殖质样（C4）组分。与四个组分的总荧光强度相比，两个腐殖质样组分的贡献百分比（C 腐殖质）从旱季到雨季显著增加。这种季节性差异的贡献进一步证实，与旱季相比，雨季降雨增加后，流域流入湖中的腐殖质样物质可能会增加。这一发现得到了雨季在湖泊中采集的 CDOM 样品的 a(250)/a(365)高于旱季的支持。与大浦河和长兜河相比，雨季从银村河采集的 CDOM 样品的 C3 和 a(350)平均值明显较高，表明银村河输入的陆地 CDOM 的重要性。
