Numerical Analysis of Passive Capillary Wick Samplers prior to Field Installation
Numerical Analysis of Passive Capillary Wick Samplers prior to Field Installation
复制标题
现场安装前被动毛细管芯采样器的数值分析
DOI：
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
J. Vanderborght
中科院分区：
文献类型：
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作者：
J. Mertens;J. Diels;J. Feyen;J. Vanderborght
准确测量通过包气区的水通量和相关养分或污染物浓度很困难，因为需要对土壤施加适当的吸力才能在不饱和条件下对水进行采样。被动毛细管芯采样系统是廉价且可靠的仪器，可对渗流区的水通量进行可接受的测量；然而，它们在测量实际通量方面的成功取决于它们与安装位置的土壤和气候条件的兼容性。这项研究是在现场实验的预先规划阶段开展的，其主要目标是监测溶解的有机物以及 Cu 2+ 和农药通过包气区的相关转移。我们使用 HYDRUS-2D 软件研究了二维和轴对称三维数值分析的组合，以确定哪种采样器几何结构、吸芯类型、吸芯长度和吸芯数量最适合实验现场的土壤条件。发现灯芯长度随季节变化（冬季 40 厘米，夏季 100 厘米）的 AM3/8HI 灯芯最适合试验田的土壤和气候条件。数值分析表明，设计良好的灯芯采样器对采样器附近的土壤含水量的影响可以忽略不计。建议采用双环灯芯取样器，以最大限度地减少安装坑或沟槽与取样器之间区域的影响。这种方法很容易适用并可转移到其他土壤和灯芯类型以及气候条件。该研究强调了数值模拟在安装前优化实验设计的适用性。
Accurately measuring water fluxes and associated nutrient or contaminant concentrations through the vadose zone is difficult because an appropriate suction needs to be exerted on the soil to sample water under unsaturated conditions. Passive capillary wick sampling systems are cheap and reliable instruments resulting in acceptable measurements of water fluxes in the vadose zone; however, their success in measuring realistic fluxes depends on their compatibility with the soil and climatic conditions in which they are installed. This study was developed in the preplanning phase of a field experiment with its main objective the monitoring of dissolved organic matter and the associated transfer of Cu 2+ and pesticides through the vadose zone. We studied a combination of two-dimensional and axisymmetrical three-dimensional numerical analyses using the HYDRUS-2D software to identify what sampler geometry, wick type, wick length, and number of wicks are most suitable for the soil conditions at the experimental site. An AM3/8HI wick with seasonally varying wick length (40 cm in winter and 100 cm in summer) was found to be most appropriate for the soil and climatic conditions of the experimental field. The numerical analysis indicated that well-designed wick samplers had a negligible effect on the soil moisture content close to the sampler. A double-ring wick sampler is proposed to minimize the effect of the area between the installation pit or trench and the sampler. This approach is easily applicable and transferable to other soil and wick types and climatic conditions. The study emphasizes the suitability of numerical modeling to optimize experimental design before installation.