Temporal controls on dissolved organic matter and lignin biogeochemistry in a pristine tropical river
Temporal controls on dissolved organic matter and lignin biogeochemistry in a pristine tropical river
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DOI：
10.1029/2009jg001180
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发表时间：
2009-12
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通讯作者：
R. Spencer;P. Hernes;R. Ruf;A. Baker;R. Dyda;Aron Stubbins;J. Six
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作者：
R. Spencer;P. Hernes;R. Ruf;A. Baker;R. Dyda;Aron Stubbins;J. Six
[1]测定了刚果东北部Epulu河的溶解有机碳（DOC）、木质素生物标志物和溶解有机物（DOM）的光学性质，旨在研究热带雨林河流中DOM的数量和化学组成的时间控制。根据该地区的水文状况阶段定义了三个不同的时期，（1）干旱冲洗后时期，（2）中间时期，（3）干旱期开始/冲洗后，进行了采样。DOM的数量和质量的时间变化与最高的DOC，木质素浓度（108）和碳标准化（Λ8）值在冲洗期间归因于更大的地表径流和有机物丰富的层位的淋溶，与最低值在干燥期/冲洗后，一旦源材料被很好地淋溶。CDOM与DOC、DOC 8呈显著正相关（r2分别为0.85和0.83; p < 0.001），CDOM质量测量（SUVA 254、光谱斜率比和荧光指数）与Λ8值强相关（r2分别为0.77、0.69和0.75; p < 0.001），证明了从简单的光学测量获得DOC和木质素输出以及跟踪热带河流系统中DOM质量的能力。这项研究表明，由于不断变化的水文输入的热带河流的DOM的数量和质量的变化，如以前报道的温带和北方高纬度河流的类似影响。因此，在热带河流的冲洗期值得进一步研究，因为它们是了解生态系统地球化学的最大出口新鲜浸出的植物材料发生在这段时间内的关键。
[1] Dissolved organic carbon (DOC), lignin biomarkers, and the optical properties of dissolved organic matter (DOM) were measured in the Epulu River (northeast Democratic Republic of Congo) with the aim of investigating temporal controls on the quantity and chemical composition of DOM in a tropical rainforest river. Three different periods defined by stages of the hydrologic regime of the region, (1) post dry flushing period, (2) intermediary period, and (3) start of the dry period/post flush, were sampled. Temporal variability in DOM quantity and quality was observed with highest DOC, lignin concentration (Σ8) and carbon-normalized (Λ8) values during the flushing period attributed to greater surface runoff and leaching of organic-rich horizons, with lowest values in the dry period/post flush once source materials were well leached. Chromophoric DOM (CDOM) was strongly correlated to DOC and Σ8 (r2 = 0.85 and 0.83, respectively; p < 0.001), and CDOM quality measurements (SUVA254, spectral slope ratio and fluorescence index) were strongly correlated to Λ8 values (r2 = 0.77, 0.69, and 0.75, respectively; p < 0.001), demonstrating the ability to derive DOC and lignin export and to track DOM quality in tropical riverine systems from simple optical measurements. This study demonstrates similar effects in the variability of DOM quantity and quality due to changing hydrologic inputs for a tropical river as has been previously reported for temperate and northern high-latitude rivers. Therefore, flushing periods in tropical rivers warrant further study, as they are critical toward understanding ecosystem biogeochemistry as maximal export of freshly leached plant material occurs during this time period.