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首页> 外文期刊>Journal of Hydrology >Variations of self-potential and unsaturated water flow with time in sandy loam and clay loam soils
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Variations of self-potential and unsaturated water flow with time in sandy loam and clay loam soils

机译：砂壤土和粘土壤土中自潜水和非饱和水流量随时间的变化

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Accurate assessment of soil-water fluxes is essential in soil physics due to its direct implications in environmental, agronomical or hydrological applications. Field estimations of soil-water fluxes by 'classical' hydraulic methods are often difficult to obtain. Moreover, water fluxes are highly variable in space and time. The obtainment of a reasonable estimate for this variable would require numerous measurement sites. However, such a requirement is rarely met. Thony et al. [CR Acad. Sci. Paris, Earth Planetary Sci. 325 (1997) 317] presented the experimental evidence of a linear relationship between the self-potential (SP) and the unsaturated soil-water flux. Therefore, this relationship would allow the indirect assessment of the water flux using electrical measurements. Such an approach would appear much more flexible and easier to perform than the current hydraulic measurements. The aim of this study is to experimentally investigate the existence and robustness of the flux-SP relationship for different soil types and pedoclimatic conditions. The soil-water fluxes and the SP were monitored in a long-term experiment involving two types of soils, contrasting in hydraulic and electric properties. The soils were placed in lysimeters which were instrumented with tensiometers and TDR probes for monitoring hydraulic heads and moisture content, respectively. Unpolarizable SP electrodes, temperature sensors and suction cups (for collecting pore water) were also installed in the lysimeters. The SP and the fluxes were measured or calculated in the 30-40 cm depth section. Results show that the variations of the SP with time were clearly linked to both rainfall events and evaporation. However, in the long-term, the linear relationship between the unsaturated water flux and the SP evolves from strongly correlated to almost not correlated. The slope (sensitivity) of the flux-SP relationship varies with the soil type, decreasing with more electrically conductive soil. Taking into account a varying soil-electrode contact greatly improves the flux-SP relationship at the scale of the rainfall event, particularly when considering infiltration and drainage phases separately. Nevertheless, at the scale of a year, with alternated rainfalls and evaporation phases, the robustness of the relationship decreases (i.e. the coefficients of the relationship vary between events). This variability could be related to time variations in electrical conductivity, not so much to that of the soil-water, but rather to that of the water from the salted soil mud added to the SP electrodes at the time of installation. This study points out methodological problems associated with the measurement of SP in shallow unsaturated soils over the long-term and the need for designing specific electrodes for this purpose. However, in deep soils beneath the root zone, environmental conditions generally vary slowly and lightly in comparison to surface horizons. In this case and with our present set of SP measurement devices, the flux-SP relationship could be more stable than in the surface soil horizons and useful for examining aquifer recharge, capillary rises or contaminant transfer. (C) 2002 Elsevier Science B.V. All rights reserved. [References: 28]
机译：由于土壤水通量直接影响环境，农艺或水文应用，因此对土壤水通量的准确评估至关重要。通过“经典”水力方法对土壤水通量的现场估算通常很难获得。而且，水通量的时空高度可变。要获得此变量的合理估计值，将需要大量测量位置。但是，这种要求很少得到满足。 Thony等。 [CR Acad。科学巴黎，地球行星科学。 [325（1997）317]提出了自电势（SP）与非饱和土壤水通量之间线性关系的实验证据。因此，这种关系将允许使用电气测量间接评估水通量。与当前的水力测量相比，这种方法显得更加灵活且易于执行。这项研究的目的是通过实验研究不同土壤类型和气候条件下通量-SP关系的存在性和鲁棒性。在一项涉及两种类型土壤的长期实验中，对土壤水通量和SP进行了监测，对比了水力和电学性质。将土壤置于测渗仪中，用张力计和TDR探针分别对水力头和水分含量进行监测。测渗仪中还安装了不可极化的SP电极，温度传感器和吸盘（用于收集孔隙水）。在30-40厘米深的区域中测量或计算SP和通量。结果表明，SP随时间的变化与降雨事件和蒸发都有明显联系。但是，从长期来看，非饱和水通量与SP之间的线性关系从强相关演变为几乎不相关。通量-SP关系的斜率（灵敏度）随土壤类型而变化，随着导电性更强的土壤而减小。考虑到土壤电极接触的变化，在降雨事件的规模上，特别是在分别考虑入渗和排水阶段时，极大地改善了通量-SP关系。然而，在一年的尺度上，随着降雨和蒸发阶段的交替，关系的稳健性降低（即，关系的系数在事件之间有所不同）。这种变化可能与电导率的时间变化有关，与土壤-水的变化不大相关，而与安装时添加到SP电极上的盐渍土壤中的水的变化有关。这项研究指出了长期测量浅层非饱和土壤中SP的方法学问题，并为此需要设计专用电极。但是，在根部区域下方的深层土壤中，与地表水平相比，环境条件通常缓慢而轻微地变化。在这种情况下，使用我们目前的一套SP测量设备，通量-SP关系可能比表层土壤层更稳定，并且对于检查含水层补给，毛细管上升或污染物转移很有用。 （C）2002 Elsevier Science B.V.保留所有权利。 [参考：28]

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