Use of Tension Infiltrometer Data with Unsaturated Hydraulic Conductivity Models
Use of Tension Infiltrometer Data with Unsaturated Hydraulic Conductivity Models
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使用张力渗透仪数据与不饱和水力电导率模型
DOI：
10.1111/j.1745-6584.1994.tb00941.x
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发表时间：
1994
期刊：
影响因子：
--
通讯作者：
T. Illangasekare
中科院分区：
文献类型：
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作者：
M. Nachabe;T. Illangasekare
提出了一种利用张力仪资料估算非饱和渗透系数与土-水压力关系的新方法。在该方法中，分析了张力渗透计盘下渗透过程的早期瞬变阶段和随后的准稳定阶段。我们的研究表明，早期的入渗率符合水-根-时间关系(Philip，1969)。这一行为允许评估吸水率，这是土壤扩散率的综合衡量标准。随后，渗透计盘下的三维准定常流动发展，圆池水流的Wooding方程被用来计算吸附数和饱和导水率。给出了非饱和导水率的Brooks和Corey模型参数与吸水率和吸附数之间的简单代数表达式。本文介绍的方法将张力渗透仪数据的应用扩展到一大类渗透系数模型，并提供了一种为这些模型确定合适参数值的现场技术。
采用配有超声波雾化器和活性膜倍增检测器的电感耦合等离子体质谱(ICP-MS)直接测定地下水中54种痕量元素。锂、砷、钚、锶、钡和锑的含量在每升微克(十亿分之一=ppb)范围内。大多数其他元素的浓度为每升纳克(百万分之百万分之一=ppt)。采用离子交换预富集，以提高测量浓度低至0.05ppt的稀土元素的灵敏度。血浆中分子物种的形成会对某些元素产生假阳性结果。硅或二氧化碳的存在干扰了钪的测定，锶干扰了铑和钯，而钡干扰了铕。讨论了这些干扰的校正方法。总而言之，内华达州四个泉水中54种元素的浓度几乎跨越了七个数量级。
A new method is presented to estimate the relationship between unsaturated hydraulic conductivity and soil-water pressure using tension infiltrometer data. In this method, both the early transient and the subsequent quasi-steady stages of the infiltration process underneath a tension infiltrometer disc are analyzed. Our investigation indicates that the infiltration rate at early times closely follows the aquare-root-of-time relationship (Philip, 1969). This behavior permits the evaluation of the sorptivity, which is an integrated measure of soil diffusivity. At later times, three-dimensional quasi-steady flow beneath the infiltrometer disc develops, and the Wooding equation for flow from a circular pond is used to evaluate the sorptive number and the saturated hydraulic conductivity. Simple algebraic expressions are introduced to relate the sorptivity and sorptive number to the parameters of the Brooks and Corey model of unsaturated hydraulic conductivity. The method described here extends the utility of tension infiltrometer data to a large class of hydraulic conductivity models and provides an in situ technique to determine suitable parameters values for these models.
An ICP-MS, equipped with an ultrasonic nebulizer and active-film multiplier detector, is used to attempt to determine 54 trace elements directly in ground water. Lithium, arsenic, rubidium, strontium, barium, and antimony are found in the microgram-per-liter (part-per-billion = ppb) range. Most of the other elements are present at nanogram-per-liter (part-per-trillion = ppt) concentrations. Ion exchange preconcentration is utilized in order to improve the sensitivity for measuring the rare earth elements that exist at concentrations as low as 0.05 ppt for lutetium, thulium, and terbium. The formation of molecular species in the plasma produces false positive results for some of the elements. The presence of silicon or carbon dioxide interferes with the measurement of scandium, strontium interferes with rhodium and palladium, and barium interferes with europium. Correction procedures for these interferences are discussed. All together, the concentrations of the 54 elements in water from four Nevada springs span almost seven orders of magnitude.