Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao 266100, China.
Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao 266100, China; Institute of Marine Chemistry, Ocean University of China, Qingdao 266100, China.
Sci Total Environ. 2021 Mar 25;762:143164. doi: 10.1016/j.scitotenv.2020.143164. Epub 2020 Oct 22.
Optical properties of dissolved organic matter (DOM) were used as an indicator of the quantitative and qualitative changes occurring in marine DOM. The spatiotemporal distribution, bioavailability, and photoreactivity of chromophoric DOM (CDOM) and dissolved organic carbon (DOC) were investigated in the East China Sea (ECS) and the Yellow Sea (YS) during spring and summer using absorption spectroscopy and fluorescence excitation-emission matrix-parallel factor analysis. Over a 4-month laboratory study, we measured changes in six commonly used optical indices, including spectral slope (S), slope ratio (S: S/S), specific ultraviolet absorbance (SUVA), ratio of the sum of protein-like components to the sum of humic-like components (C/C), biological index (BIX), and humification index (HIX) to determine their changes following biological and photochemical degradation processes. Significant seasonal variations were observed in the spectral characteristics of CDOM in the ECS and the YS, indicating a stronger influence of the terrestrial origin and highly aromatic content of DOM in summer than in spring; this result was likely the consequence of an increase in the Changjiang River discharge, phytoplankton production, and biological activity, resulting in an increase in DOM production. Significant correlation between salinity and optical parameters (SUVA, S, S, C/C) indicated that water mixing strongly influenced the distributions of these optical parameters. The bioreactivity and photoreactivity of DOM varied depending on the source material, and the autochthonous protein-like DOM was more prone to biodegradation than the terrestrial DOM. The photodegradation processes acted preferentially on the CDOM than the colorless DOM. These results demonstrated that the optical parameters exhibited distinct changes during the mixing and the biodegradation and photodegradation processes and explained the seasonal distribution of DOM in the ECS and the YS.
溶解有机物（DOM）的光学性质可作为海洋 DOM 发生定量和定性变化的指示物。本研究采用吸收光谱法和荧光激发-发射矩阵-平行因子分析（EEM-PARAFAC），于春、夏两季调查了东海（ECS）和黄海（YS）中有色溶解有机物（CDOM）和溶解有机碳（DOC）的时空分布、生物可利用性和光反应活性。在为期 4 个月的实验室研究中，我们测量了六种常用光学指数（包括光谱斜率（S）、斜率比（S: S/S）、比紫外吸光度（SUVA）、蛋白类物质与腐殖类物质总和的比值（C/C）、生物指数（BIX）和腐殖化指数（HIX））的变化，以确定它们在生物和光化学降解过程中的变化。ECS 和 YS 中 CDOM 的光谱特征具有明显的季节性变化，表明 DOM 的陆地来源和高芳香性在夏季比春季的影响更强；这一结果可能是由于长江径流量增加、浮游植物生产力和生物活性增强，导致 DOM 产量增加所致。盐度与光学参数（SUVA、S、S、C/C）之间存在显著相关性，表明水混合强烈影响这些光学参数的分布。DOM 的生物反应性和光反应性取决于源材料，自生源蛋白类 DOM 比陆源 DOM 更容易生物降解。光降解过程优先作用于 CDOM 而非无色 DOM。这些结果表明，光学参数在混合、生物降解和光降解过程中表现出明显变化，解释了 ECS 和 YS 中 DOM 的季节性分布。
