• 关键词：溶解性有机质  分子量特征  荧光猝灭  二维相关光谱（2D-COS）  金属结合能力

• 基金项目：国家自然科学基金（No.41977322，41901120）；湖泊科学与环境国家重点实验室开放基金（No.2018SKL004）；山东省自然科学基金（No.ZR2019BD052）

• 姚昕
• 聊城大学地理与环境学院，聊城 252000;中国科学院南京地理与湖泊研究所，湖泊与环境国家重点实验室，南京 210008

• 樊团团
• 聊城大学地理与环境学院，聊城 252000

• 孙小平
• 山东省聊城生态环境监测中心，聊城 252000

• 任浩宇
• 聊城大学地理与环境学院，聊城 252000;北京师范大学水科学学院，北京 100875

• 马飞扬
• 聊城大学地理与环境学院，聊城 252000

• 刘立
• 聊城大学地理与环境学院，聊城 252000

• 摘要：将采集自徒骇河聊城河段沉水植被生长区的DOM分为3个分子量级别：<0.7 μm DOM、<500 kDa DOM、<100 kDa DOM，通过三维荧光结合平行因子分析（EEM-PARAFAC）和荧光滴定法探讨水体中不同分子量DOM的荧光特征及其与重金属（Cu²⁺和Pb²⁺）的络合作用.结果表明：草源DOM的有机碳主要储存在分子量<100 kDa组分中.PARAFAC分析得出4个荧光组分，分别为类色氨酸组分C2、C4，以及酪氨酸组分C1和类腐殖质组分C3.草源DOM主要以分子量<100 kDa的类色氨酸组分C2和酪氨酸组分C1为主.二维相关光谱（2D-COS）表明，与类腐殖物质相比，类蛋白物质优先与Cu²⁺与Pb²⁺发生猝灭，DOM中不同分子量组分与Cu²⁺与Pb²⁺的猝灭顺序未发生改变.在与Cu²⁺结合的过程中，不同 分子量中类腐殖质组分C3的络合常数（logK_a）大于类蛋白组分C1、C2，表明类腐殖质组分的金属结合能力强于类蛋白质组分；随着分子量级别的降低，组分C3的logK_a值逐渐增大（3.47<3.59<3.73），表明低分子量（<100 kDa）中的类腐殖质与Cu²⁺具有更高的结合能力.不同分子量DOM中，类蛋白组分C1、C2、C4在分子量<0.7 μm DOM中的logK_a值均最高，表明高分子量（<0.7 μm）的类蛋白质更容易与Cu²⁺结合，而Pb²⁺与各组分结合出现了荧光增强或猝灭的现象.DOM-Cu²⁺与DOM-Pb²⁺结合表现出不同的结合规律，反映出金属种类与DOM结合的异质性与复杂性.

• Abstract：In this study， DOM samples collected within the submerged plant growing area in the Liaocheng reach of Tuhai River were divided into three molecular weight levels， i.e.， < 0.7 μm DOM， < 500 kDa DOM， and < 100 kDa DOM. Fluorescence characteristics and binding behavior with heavy metals （Cu²⁺ and Pb²⁺） of the fractionated DOM were studied using three-dimensional fluorescence combined with parallel factor analysis （EEM-PARAFAC） and fluorescence titration. Results showed that the organic carbon of macrophytes-derived DOM was mainly stored in <100 kDa fraction. Four fluorescence components were extracted by PARAFAC， including the tryptophan-like components C2 and C4， the tyrosine component C1， and the humic-like component C3. The macrophytes-derived DOM was mainly composed of C1 and C2 in molecular weight <100 kDa. 2D correlation spectra （2D-COS） showed that compared to humic-like substances， protein-like substances preferentially quenched with Cu²⁺ and Pb²⁺. The quenching orders of different molecular weight fractions in DOM with Cu²⁺ and Pb²⁺ did not change. In the process of binding with Cu²⁺， humic-like component C3 possessed higher logK_a values than protein-like components C1 and C2 in different molecular weights DOM， which indicated that humic-like components exhibited higher binding ability than protein-like counterparts. The logK_a values of component C3 （3.47<3.59<3.73） increased gradually with decreased molecular weight level， indicating that the humic-like components in low molecular weight （<100 kDa） had better binding ability to Cu²⁺. In fractioned DOM， the highest logK_a values were found in protein-like components C1， C2， and C4 in <0.7 μm fraction， which indicated that protein-like components in <0.7 μm fraction were easier to bind to Cu²⁺， while the fluorescence intensities of components were enhanced or quenched with the addition of Pb²⁺. Different binding pattern were showed among DOM with Cu²⁺ and Pb²⁺， which reflected the heterogeneity and complexity of the binding between metal species and DOM.

• Key words：dissolved organic matter  molecular weight characteristics  fluorescence quenching  2D-COS  metal-binding ability

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