Sediment size distribution and composition in a reservoir affected by severe water level fluctuations.
Sediment size distribution and composition in a reservoir affected by severe water level fluctuations.
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DOI：
10.1016/j.scitotenv.2015.06.033
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
P. López;J. López-Tarazón;J. P. Casas‐Ruiz;M. Pompêo;J. Ordóñez;I. Muñoz
中科院分区：
文献类型：
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作者：
P. López;J. López-Tarazón;J. P. Casas‐Ruiz;M. Pompêo;J. Ordóñez;I. Muñoz
储层沉积物是有机碳的重要汇，有机碳的埋藏依赖于沉积和成矿两个相反的过程。因此，诸如严重的水位波动等因素预计会影响OC积累的速度，因为它们可能影响沉积和矿化。Barasona水库在历史上一直受到淤积的威胁，而灌溉用水则导致水位急剧下降。在此背景下，我们研究了Barasona水库近期沉积物的物理化学特征（粒度、主微量元素组成、有机碳和无机碳、氮）及其相互关系，以期：a)阐明OC聚集的主要过程，b)评价OC的矿化速率，c)探讨干旱对该系统沉积物特征的影响。结果表明：Barasona沉积物以细粉砂（>占60%）和粘土（>占20%）为主，平均粒径由尾向坝逐渐减小；干燥使颗粒分选增加，粒径分布呈双峰分布，但对平均粒径没有影响。从组成上看，Barasona沉积物均质性较好，氮（TN）和磷的浓度较低（分别< 1.2 g kg - 1dw和< 0.6 g kg - 1dw）， OC的浓度较高（≈36 g kg - 1dw）。全氮与干重呈负相关。由于水位的剧烈变化，沉积物的混合可能有利于观察到的巴拉索纳沉积物的均匀性，影响碳、主要离子和粒度。Barasona沉积物中OC的高沉积量表明OC对细颗粒的吸附作用比北方湖泊更重要。湿沉淀物的耗氧量为2.26 ~ 3.15 mg O2m−2day−1，与地中海流水的耗氧量相近。
The reservoir sediments are important sinks for organic carbon (OC), the OC burial being dependent on two opposite processes, deposition and mineralization. Hence factors such as severe water level fluctuations are expected to influence the rate of OC accumulation as they may affect both deposition and mineralization. The Barasona Reservoir has been historically threatened by siltation, whilst the use of water for irrigation involves a drastic decrease of the water level. In this context, we have studied the physical and chemical characteristics (grain size, major and minor elemental compositions, organic and inorganic carbon, and nitrogen) of the recent sediments of the Barasona Reservoir and the relationships among them in order to: a) elucidate the main processes governing OC accumulation, b) evaluate the rate of OC mineralization and c) approach the effect of drought on the sediment characteristics in this system. Our results indicated that Barasona sediments were dominated by fine silts (> 60%) and clays (> 20%), the mean particle size decreasing from tail to dam. Desiccation increased particle sorting and size distribution became bimodal, but no effect on average size was observed. Attending to the composition, Barasona sediments were very homogeneous with low concentrations of nitrogen (TN) and phosphorus (< 1.2 g kg− 1dw and < 0.6 g kg− 1dw, respectively) and high concentration of OC (≈ 36 g kg− 1dw). TN was negatively related to dry weight. Sediment mixing due to drastic changes in water level may have favoured the observed homogeneity of Barasona sediments affecting carbon, major ions and grain size. The high amount of OC deposited in Barasona sediment suggested that the adsorption of OC onto fine particles was more important than in boreal lakes. The rate of oxygen consumption by wet sediment ranged from 2.26 to 3.15 mg O2m− 2day− 1, values close to those compiled for Mediterranean running waters.