Optical characterization of CDOM in a marsh-influenced environment in the Changjiang (Yangtze River) Estuary
Optical characterization of CDOM in a marsh-influenced environment in the Changjiang (Yangtze River) Estuary
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长江口沼泽环境中 CDOM 的光学表征
DOI：
10.1007/s12665-010-0885-8
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发表时间：
2011-10-01
影响因子：
2.8
通讯作者：
Cai, Jingong
中科院分区：
文献类型：
--
作者：
Gao, Lei;Fan, Daidu;Cai, Jingong
为了阐明潮汐沼泽对近岸水体色性溶解有机质（CDOM）数量和化学结构的影响，在长江口潮汐沼泽的3个跨沼泽样带上采集了地表水样品。此外，从沼泽中收集3个沉积物岩心，在加入上覆潮汐水后，在实验室孵育10 h。测定了这些样品的营养成分、DOC、吸收、荧光激发发射矩阵（EEM）光谱等参数，清楚地说明了潮汐沼泽释放DOC、CDOM吸收剂和荧光分子的情况。为了表征沼泽衍生CDOM的化学性质，研究人员绘制了这些样品中一系列光学指标（包括摩尔吸收率、吸收光谱斜率、荧光量子产率和某些激发/发射位置之间的荧光比）的变化，并将其与站的离岸距离以及孵育时间进行了对比。从文献中可以看出，这些变化与CDOM混合物中的分子量、芳香性、腐殖质/腐殖质或异域/原生比例密切相关。这项研究表明，CDOM荧光团从海洋到陆地，在沼泽梯度上变得更像腐殖质，而更不像蛋白质。此外，实验室孵育前后的EEM光谱之间的相减应用于更详细地说明在沉积物-覆盖水界面交换的纯荧光化合物的性质。
To elucidate the influence of tidal marshes on the amount and chemical structure of chromophoric dissolved organic matter (CDOM) in adjacent coastal waters, surface water samples were collected along three cross-marsh transects in tidal marshes within the Changjiang Estuary. In addition, three sediment cores were collected from the marshes and incubated for 10 h in the laboratory after adding overlying tidal waters. Nutrients, DOC, absorption, fluorescence excitation–emission matrix (EEM) spectroscopy, and other parameters were measured in these samples, which clearly illustrated releases by the tidal marshes of DOC, and CDOM absorbent and fluorescent molecules. To characterize the chemical nature of the marsh-derived CDOM, variations in a suite of optical indices (including molar absorptivity, absorption spectral slope, fluorescence quantum yield, and fluorescence ratios between certain excitation/emission locations) in these samples were plotted against the offshore distance of the stations as well as the incubation time. From the literature, it has been suggested that these variations are closely associated with molecular weight, aromaticity, and humic/fulvic or allochthonous/autochthonous ratios in the CDOM mixtures. This study showed that the CDOM fluorophores changed to more humic-like and were less protein-like from sea to land across the marsh gradients. Furthermore, subtractions between EEM spectra before and after laboratory incubations were applied to illustrate in greater detail the properties of the pure fluorescent compounds exchanged at the sediment–overlying water interface.