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首页> 外文学位 >Controls on dissolved organic carbon at Hubbard Brook Experimental Forest and its effects on stream acid-base chemistry.
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Controls on dissolved organic carbon at Hubbard Brook Experimental Forest and its effects on stream acid-base chemistry.

机译：哈伯德布鲁克实验林中溶解有机碳的控制及其对流酸碱化学的影响。

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In this study, I investigated the factors that control the spatial and temporal variations in stream and soil solution dissolved organic carbon (DOC) concentrations and composition within a north-facing watershed (Watershed 9) and across the forested valley at the Hubbard Brook Experimental Forest, New Hampshire.; Soil solutions displayed horizontal patterns in DOC fractions with hydrophobic acids dominating in the Oa horizon. Hydrophobic acids were also the dominant fraction in stream water DOC. Temporal variations in the proportion of DOC fractions were mainly evident in the Oa soil horizon leachate and stream water. Stream DOC fractions varied spatially, with increases in the concentration of both hydrophobic and hydrophilic acid fractions with increasing elevation, however hydrophobic acids increased more markedly. Various factors were related to spatial variations in stream DOC concentration and composition including variations in forest floor C, topographic index, soil depth, and slope. However, forest floor C concentrations exhibited the strongest relationship. During hydrologic events, hydrophobic acids dominated DOC increases at peak discharge. During both base flow and at peak discharge during events, the ratio of hydrophobic acids to hydrophilic acids suggested that DOC in the stream largely originated from a wetland at the headwaters of Watershed 9.; Organic acids are generally thought to play a minor role in the episodic acidification of streams in the U.S., mainly because most streams studied to date are characterized by low concentrations of DOC. I hypothesized that in streams with high concentrations of DOC, episodic acidification will be controlled by increases in naturally occurring organic acids. During snow melt events, organic acids were a minor contributor to the short-term acidification of stream water, with increases in NO3− and dilution of base cations being the dominant mechanisms. During summer rainfall events however, increases in inputs of organic acids were the dominant mechanism of episodic acidification when soil water was the dominant contributor to stream discharge. Also precipitation events occurring after relatively wet antecedent conditions were likely to result in more severe acid episodes than events that followed drier antecedent conditions.
机译：在这项研究中，我研究了在北向分水岭（分水岭9）以及哈伯德布鲁克实验林的整个森林山谷中控制河流和土壤溶液中溶解有机碳（DOC）浓度和组成的时空变化的因素。 ， 新罕布什尔。;土壤溶液在DOC馏分中显示出水平模式，其中疏水酸在Oa层中占主导地位。疏水酸也是溪流水DOC中的主要组分。 DOC组分比例的时间变化主要在Oa土壤层渗滤液和溪流水中明显。流DOC馏分在空间上变化，疏水性和亲水性酸级分的浓度均随高度的增加而增加，但是疏水性酸的增加更为明显。各种因素均与溪流DOC浓度和组成的空间变化有关，包括林地C，地形指数，土壤深度和坡度的变化。但是，林地C浓度表现出最强的关系。在水文事件期间，以疏水酸为主的DOC在峰值放电时增加。在基流和事件高峰排放期间，疏水性酸与亲水性酸的比率表明，流中的DOC主要来自于分水岭9上游的湿地。通常认为有机酸在美国物流的间歇酸化中起次要作用，主要是因为迄今为止研究的大多数物流都以低浓度的DOC为特征。我假设在高浓度DOC的流中，间歇性酸化将受到天然有机酸含量增加的控制。在融雪事件中，有机酸对溪流水短期酸化的贡献较小，NO 3 -的增加和碱阳离子的稀释是主要机制。 。然而，在夏季降雨事件中，当土壤水是溪流排放的主要贡献者时，有机酸输入的增加是突发酸化的主要机制。同样，在较湿的前期条件之后发生的降水事件比在较早的条件下发生的事件更可能导致更严重的酸发作。

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