Effect of subcritical hydrophobicity in a sandy soil on water infiltration and mobile water content
Effect of subcritical hydrophobicity in a sandy soil on water infiltration and mobile water content
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DOI：
10.1002/jpln.200521743
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发表时间：
2006-02
影响因子：
2.5
通讯作者：
A. Lamparter;M. Deurer;J. Bachmann;W. Duijnisveld
中科院分区：
文献类型：
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作者：
A. Lamparter;M. Deurer;J. Bachmann;W. Duijnisveld
最近的研究表明，大多数土壤或多或少具有拒水性。已经达到亚临界的疏水性可能导致土壤不完全湿润和优先流动。这两种过程都可能减少水和溶质在渗透区的停留时间，从而增加地下水污染的风险。因此，本文的目的是评价土壤润湿性降低对土壤水分入渗速率的影响，并通过分析入渗区内的不动水含量来研究土壤水分优先流动的趋势。2002年11月，在德国汉诺威北部30公里的针叶林中进行了野外试验。通过测定接触角来定量测定土壤的疏水性。采用双环张力渗透仪在3个土层中测量了灰质沙土的水导率。为了量化可能的优先流动效应，在入渗水中加入了lib示踪剂，以评估入渗后的流动含水量分数。此外，将水的入渗速率与乙醇的入渗速率进行了比较。结果表明：田间湿土的实际防水性主要为亚临界（接触角<90°）；由于亚临界驱避性，水的渗透速率比乙醇的渗透速率降低了3-170倍（不包括润湿效应）。小尺度接触角测量和入渗区平均不动土壤含水量分析都不能很好地反映这种空间变化的入渗行为。我们的结论是，这种由小尺度润湿性效应引起的水的特殊入渗行为可能暂时降低水流路径的局部连通性。
Recent research shows that most soils are more or less water repellent. Already subcritical water repellency may cause incomplete soil wetting and preferential flow. Both processes potentially reduce the residence time of water and solutes in the vadose zone, resulting in an enhanced risk of groundwater contamination. The objective of the present paper is, therefore, to evaluate the impact of reduced soil wettability on the soil water infiltration rate and to investigate the tendency towards preferential flow with the analysis of the immobile water content in the infiltration zone. In november 2002, a field experiment was done in a coniferous forest, 30 km N of Hannover, Germany. Soil hydrophobicity was quantified by measuring the contact angles. The hydraulic conductivity of the podsolic sandy soil was measured depth-dependent with a double-ring tension infiltrometer in three soil horizons. To quantify possible preferential-flow effects, a LiBr-Tracer was added to the infiltrating water to evaluate the mobile water-content fraction after infiltration. Additionally, infiltration rates of water were compared with infiltration rates of ethanol which were determined after water infiltration at the same locations. Results show that the actual water repellency of field-moist soil was mainly subcritical (contact angle <90°). Water infiltration rates were reduced due to subcritical repellency by a factor of 3–170 compared with ethanol infiltration rates (exclusion of wetting effects). This spatially variable infiltration behavior was not clearly reflected neither by the small-scale contact-angle measurements nor by the analysis of the average immobile soil water content in the infiltration zone. We conclude that this specific infiltration behavior of water caused by small-scale wettability effects may temporarily reduce the local connectivity of water-flow pathways.