长江口-东海陆架咸淡水混合...解性有机质的分布及荧光特征_李明洋.pdf

生态毒理学报Asian Journal of Ecotoxicology第 17 卷 第 6 期 2022 年 12 月Vol.17,No.6 Dec.2022 基金项目:国家自然科学基金面上项目(42176152)第一作者:李明洋(1997),女,硕士研究生,研究方向为生态毒理学,E-mail: *通信作者(Corresponding author),E-mail:DOI:10.7524/AJE.1673-5897.20221014004李明洋,王锐,李梓轩,等.长江口-东海陆架咸淡水混合影响下溶解性有机质的分布及荧光特征J.生态毒理学报,2022,17(6):15-28Li M Y,Wang R,Li Z X,et al.Distribution and fluorescence characteristics of dissolved organic matter along the Yangtze River Estuary-East China SeaShelf Transect under impacts of freshwater-seawater mixing J.Asian Journal of Ecotoxicology,2022,17(6):15-28(in Chinese)长江口-东海陆架咸淡水混合影响下溶解性有机质的分布及荧光特征李明洋,王锐*,李梓轩,黄清辉,尹大强同济大学环境科学与工程学院,长江水环境教育部重点实验室,上海 200092收稿日期:2022-10-14 录用日期:2022-11-29摘要:溶解性有机质(dissolved organic matter,DOM)在河口区域的分布特征和环境行为对于研究河口碳的生物地球化学循环具有重要意义。本文研究了受强烈咸淡水混合影响的长江口-东海内陆架断面 14 个研究点位水体 DOM 的分布和荧光特征,并进一步探究了其与水环境因子的关联。从淡水端到海水端,溶解性有机碳(DOC)浓度逐渐降低且与盐度呈显著负相关,表明长江输入的有机质在该水域占主导地位。基于三维荧光光谱-平行因子分析进一步解析荧光溶解有机质(FDOM)组分,识别出一个类蛋白组分 C1(Ex/Em:278/320)和 3 个类腐殖质组分 C2(Ex/Em:290/385)、C3(Ex/Em:254(341)/424)和 C4(Ex/Em:275/501)。在强烈的长江口咸淡水混合影响下,该断面 4 个 FDOM 组分的荧光强度最大值(Fmax)均与盐度呈显著负相关关系。具体而言,3 个类腐殖质组分的分布主要受长江源类腐殖质在咸淡水混合过程中的稀释效应控制,而 C1 组分在中低盐度区主要受稀释效应控制,但在高盐度区则主要源于海洋自生源类蛋白贡献。大部分点位荧光指数(FI)介于 1.4 1.9 之间,表明微生物源和陆源均对腐殖质有重要贡献。生物源指数(BIX)结果表明,中低盐度点位 FDOM 主要以外源输入为主,高盐度点位则主要来自自生源的贡献。所有研究点位腐殖化指数(HIX)均低于 4,表明长江口水域 DOM 的腐殖化程度较低。关键词:溶解性有机质;长江口;盐度;荧光特征文章编号:1673-5897(2022)6-015-14 中图分类号:X171.5 文献标识码:ADistribution and Fluorescence Characteristics of Dissolved Organic Matteralong the Yangtze River Estuary-East China Sea Shelf Transect under Im-pacts of Freshwater-Seawater MixingLi Mingyang,Wang Rui*,Li Zixuan,Huang Qinghui,Yin DaqiangKey Laboratory of Yangtze River Water Environment of the Ministry of Education,College of Environmental Science and Engineering,Tongji University,Shanghai 200092,ChinaReceived 14 October 2022 accepted 29 November 2022Abstract:The distribution and environmental behavior of dissolved organic matter(DOM)in estuarine regions areimportant for understanding the biogeochemical cycling of carbon in estuary.This study investigated the spatial dis-tribution and fluorescence characteristics of DOM at 14 sites along the Yangtze River Estuary-East China Sea shelftransect,and further explored their relationships with water characteristics.From freshwater to marine sites,the dis-16 生态毒理学报第 17 卷solved organic carbon(DOC)concentration decreased gradually and exhibited a significant negative correlationwith salinity,indicating the predominate contribution of Yangtze River-derived DOM.Based on the 3D fluores-cence spectroscopy-parallel factor analysis,a protein-like component C1(Ex/Em:278/320)and three humic-likecomponents C2(Ex/Em:290/385),C3(Ex/Em:254(341)/424),and C4(Ex/Em:275/501)were identified.Underthe strong impacts of freshwater-seawater mixing,the maximum fluorescence intensity(Fmax)of the four compo-nents all showed significant negative correlations with salinity.Specifically,the spatial distributions of the three hu-mic-like components were mainly controlled by the dilution effect of Yangtze River-derived humic-like substancesduring the freshwater-seawater mixing processes.The distribution of C1 component was mainly controlled by thedilution effect at low and middle salinity sites,but mainly attributed to marine-derived autochthonous protein-likesubstances at high salinity sites.At most sites,the fluorescence index(FI)was between 1.4 and 1.9,indicating theimportant contributions of humic-like substances from both microbial metabolism and terrestrial inputs.The biolog-ical index(BIX)showed that FDOM at low and middle salinity sites was mainly derived from exogenous sources,while largely contributed by autochthonous sources at high salinity sites.The humification index(HIX)was lowerthan 4 at all the studied sites,indicating relatively low humification within the Yangtze River estuary.Keywords:dissolved organic matter;the Yangtze River estuary;salinity;fluorescence characteristics 溶解性有机质(dissolved organic matter,DOM)是芳香族和脂肪族碳氢化合物组成的复杂异质混合物,含有羟基、羰基、羧基、烯醇、硫醇和苯酚等含氧、氮和硫的官能团1-2,广泛存在于不同水生态系统中。DOM 可与持久性有机污染物相结合,作为其有机配体和迁移载体,显著影响其在生态系统中的环境行为和生态效应3。同时,DOM 可与重金属络合,通过改变重金属的化学形态控制其在水环境中的生物可利用性4-5,进而影响其在生物体中的生物累积和毒性效应。有色溶解性有机质(chromophoricdissolved organic matter,CDOM)是 DOM 中可以吸收紫外和可见光的光学活性组分,对海洋中 DOM 的贡献在河口海岸水域可以达到 70%6,在海洋碳元素的生物地球化学循环过程中具有重要意义。荧光溶解性有机质(fluorescent dissolved organic matter,FDOM)是 CDOM 中具有荧光特征的组分。近年来,随着三维荧光光谱(three-dimensional excitation-emission ma-trix spectroscopy,3D-EEMs)技术的发展,3D-EEMs 结合平行因子(parallel factor,PARAFAC)分析已成为表征 FDOM 的有力手段,极大推动了不同水环境中FDOM 组成、来源及迁移转化行为的研究7-10。长江口连接了欧亚大陆和西太平洋,是我国第一大河口。调查结果显示,2009 年长江向东海输送溶解性有机碳(dissolved organic carbon,DOC)的输送量可达 1.581012g,颗粒态有机碳(particle organiccarbon,POC)的输送量可达 1.521012g11。长江口及其邻近海域受长江冲淡水、台湾暖流、闽浙沿岸流和黄海沿岸流等水团的强烈影响12,水动力条件复杂、物质循环活跃,生物地球化学过程复杂多变。在长江口剧烈的咸淡水混合影响下,水体理化因子与生物分布特征呈现出巨大变化13,可改变长江入海DOM 的输送、分布与组成特征。然而,目前关于长江口及其邻近海域 DOM 的研究主要集中在 DOC和 POC 的空间分布及影响因素14-18,基于光谱分析的研究多讨论局部水域 DOM 的分布和荧光特征19-21,对于长江入海 FDOM 在河口水域剧烈的水环境因子变化下的分布特征和影响因素还缺乏研究。本文基于对 2021 年 11 月在长江口-东海内陆架典型断面采集的水体中 DOC 总量测定、FDOM