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首页> 外文期刊>The Science of the Total Environment >Riparian land cover and hydrology influence stream dissolved organic matter composition in an agricultural watershed
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Riparian land cover and hydrology influence stream dissolved organic matter composition in an agricultural watershed

机译：河岸土地覆盖和水文影响农业流域中河流溶解性有机物的组成

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摘要

Dissolved organic matter (DOM) represents an essential component of the carbon cycle and controls biogeochem-ical and ecological processes in aquatic systems. The composition and reactivity of DOM are determined by the spatial distribution of its sources and its residence time in a watershed. While the effects of agricultural land cover on DOM quality have been reported across spatial and temporal scales, the influence of riparian land cover on stream DOM composition has received little attention. Furthermore, the combined effects of riparian land cover and streamflow rates on DOM composition require investigation. To this end, a multi-year (2016-2018) DOM characterization study was conducted using bi-weekly water samples collected from seven sub-watersheds nested within the Little River Experimental Watershed (LREW) near Tifton, Georgia, USA DOM optical properties were determined to assess compositional variations using UV-Vis and excitation-emission matrix (EEM) fluorescence spectroscopy coupled with parallel factor (PARAFAC) analysis. PARAFAC analysis indicated that DOM in the LREW was dominated by three humic-like fluorescing components of terrestrial, microbial, and anthropogenic origin and a protein-like component. DOM composition was influenced by riparian land cover and hydrology, and shifted towards recently produced, low molecular weight DOM with low aroma-ticity as the percentage of agricultural land within riparian wetlands increased. During periods of high discharge and high baseflow, the DOM pool was dominated by recalcitrant and terrestrial-derived material but shifted towards protein-like and microbial-derived with increasing cropland in the riparian area. The results of this two-year study indicate that the replacement of forested riparian buffers with agricultural land can result in altered DOM composition which may affect carbon cycling and downstream water quality in agricultural watersheds.
机译：溶解有机物（DOM）代表碳循环的重要组成部分，并控制水生系统中的生物地球化学和生态过程。 DOM的组成和反应性取决于其来源的空间分布及其在流域中的停留时间。尽管已在空间和时间尺度上报道了农业土地覆盖对DOM质量的影响，但河岸土地覆盖对河流DOM组成的影响却鲜有关注。此外，河岸土地覆盖和水流量对DOM组成的综合影响需要调查。为此，使用每两周一次的水样进行了多年（2016-2018年）DOM表征研究，该水样是从嵌套在美国佐治亚州蒂夫顿附近的小河实验流域（LREW）中的七个子流域收集的。确定使用紫外线可见光谱和激发发射矩阵（EEM）荧光光谱结合平行因子（PARAFAC）分析来评估成分变化。 PARAFAC分析表明，LREW中的DOM主要由陆地，微生物和人为来源的三个腐殖质状荧光成分和一个蛋白状成分控制。 DOM的组成受河岸土地覆盖和水文学的影响，随着河岸湿地中农业用地的增加，向近期生产的，低香气度的低分子量DOM转移。在高流量和高基流时期，DOM库主要由顽固的和陆生的物质主导，但随着河岸地区耕地的增加，其向类蛋白质和微生物源转变。这项为期两年的研究结果表明，用农业用地代替森林河岸缓冲带会导致DOM组成发生变化，这可能会影响农业流域的碳循环和下游水质。

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