• 关键词：碳循环  溶解有机质  特征  来源  紫外-可见吸收光谱  三维荧光光谱

• 基金项目：中国科学院战略性先导科技专项（B 类）（No.XDB40020504）；国家自然科学基金项目（No.42177244，41573133）

• 吴婧
• 中国科学院地球化学研究所，贵阳 550081;中国科学院大学，北京 100049

• 张润宇
• 中国科学院地球化学研究所，贵阳 550081

• 王立英
• 中国科学院地球化学研究所，贵阳 550081

• 张志
• 中国科学院地球化学研究所，贵阳 550081;中国科学院大学，北京 100049

• 袁海军
• 中国科学院地球化学研究所，贵阳 550081;中国科学院大学，北京 100049

• 摘要：由于喀斯特地区水生生态系统中碳循环的复杂性，给溶解有机质（Dissolved organic matter，DOM）的来源解析带来了巨大的挑战和困难.本研究应用C/N比值、δ¹³C组成、紫外-可见吸收光谱与三维荧光光谱等表征技术，综合对比了西南喀斯特地区典型土壤与水生植物样品DOM的多维特征，探讨了示踪喀斯特地区DOM来源的可靠方法与指标.结果表明：水生植物的C/N比值波动范围较大，石灰土的C/N比值偏低，水生植物与土壤样品的C/N比值及δ¹³C组成有所重叠，难以区分DOM的来源.多种紫外吸收系数（a₂₅₄、a₂₈₀、a₃₀₀与a₃₅₀）侧面反映了不同DOM样品中芳香族化合物的相对丰度，SUVA₂₅₄、E2/E3、E4/E6与腐殖化指数（HIX、HIX_ohno）指示了样品之间腐殖化程度的差异，特别是HIX、荧光指数（FI）、S_R较好区分了浮游藻类与土壤DOM.修正荧光指数（YFI）还揭示了不同DOM样品的化学组成，与三维荧光光谱的平行因子分析相吻合.此外，黄壤因较低的pH值会使土壤有机质酸解为含氮组分，导致HIX、FI和S_R的匹配性不好.除浮游藻类外，HIX表明水生植物DOM均为内源，S_R却显示其主要为外源，而FI指示兼有内源和外源.因此，在进行喀斯特地区DOM来源解析时，光谱技术相比C/N比值和δ¹³C分析更加简便、有效，同时应注意不同土壤类型的异质性与水生生态系统的复杂性.

• Abstract：Due to the complexity of the carbon cycle in aquatic ecosystems in karst areas， it has brought huge challenges and difficulties to the source apportionment of dissolved organic matter （DOM）. In this study， the C/N ratio， δ¹³C composition， ultraviolet-visible absorption and three-dimensional fluorescence spectroscopy techniques were comprehensively used to compare the multidimensional features of DOM from typical soils and aquatic plants in the Southwest China Karst Region， in order to explore reliable methods and effective indicators for tracing the source of DOM in karst areas. The results showed that the C/N ratio of limestone soil was low， and the C/N ratio of aquatic plants and soil samples overlapped as well as the δ¹³C values； thus， it is difficult to distinguish the sources of DOM. A variety of UV absorption coefficients （a₂₅₄、a₂₈₀、a₃₀₀、a₃₅₀） together with SUVA₂₅₄， E2/E3， E4/E6 better reflected the relative abundance of aromatic compounds in different DOM samples. The humification index （HIX and HIX_ohno） indicated different humification degree among various DOM samples. Particularly， HIX， the fluorescence index （FI）， and S_R， effectively distinguished DOM from algae and soil end-members. The modified fluorescence index YFI further revealed the main chemical composition of different DOM samples， in accordance with with the parallel factor analysis of the three-dimensional fluorescence spectrum. However， the low pH value of yellow soil will promote the acid decomposition of soil organic matter into nitrogen-containing components， resulting in poor matching of HIX， FI， and S_R. Except for algae， the HIX indices indicated that the DOM of aquatic plants was endogenous， S_R indicated exogenous DOM， and the FI reflected both endogenous and exogenous DOM. Therefore， when determining the sources of organic matter in karst areas， the spectroscopy technique is more effective and reliable than the C/N ratio and δ¹³C analysis. Meanwhile， more attention should be given to the heterogeneity of different soil types and the complexity of aquatic ecosystems.

• Key words：carbon cycle  dissolved organic matter  characteristics  source  Ultraviolet-visible absorption spectroscopy  three-dimensional fluorescence spectroscopy

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