Keller Jason M, Brusseau Mark L
Department of Soil, Water, & Environmental Science, The University of Arizona, 429 Shantz Building, Tucson, Arizona 85721, USA.
Environ Sci Technol. 2003 Jul 15;37(14):3141-4. doi: 10.1021/es0340329.
Field-scale tests were performed to evaluate the effectiveness of the gas-phase partitioning tracer method for in-situ measurement of soil-water content. The tracer tests were conducted before and after a controlled infiltration event to evaluate performance at two water contents. Nonpartitioning (sulfur hexafluoride) and water-partitioning (difluoromethane) tracers were injected into the test zone, and their effluent breakthrough curves were analyzed using the method of moments to calculate retardation factors for difluoromethane. Soil-water contents estimated using the tracer data were compared to soil-water contents obtained independently using gravimetric core analysis, neutron scattering, and bore-hole ground penetrating radar. For the test conducted under drier soil conditions, the soil-water content estimated from the tracer test was identical to the independently measured values of 8.6% (equivalent to water saturation of 23%). For the test conducted under wetter soil conditions, the tracer test derived soil-water content was 81% of the independently measured values of 12.2% (equivalent to water saturation of 32%). The reduced efficacy at the higher soil-water content may reflectthe impact of advective and/ or diffusive mass transfer constraints on gas-phase transport. The results presented herein indicate that the partitioning tracer method is an effective technique to measure soil-water content at the field scale, especially for sites with moderate to low soil-water contents.
进行了田间尺度试验，以评估气相分配示踪剂法原位测量土壤含水量的有效性。在控制入渗事件前后进行示踪剂试验，以评估两种含水量条件下的性能。将非分配性（六氟化硫）和水分配性（二氟甲烷）示踪剂注入试验区，并使用矩量法分析其流出突破曲线，以计算二氟甲烷的延迟因子。将利用示踪剂数据估算的土壤含水量与通过重量法岩芯分析、中子散射和钻孔探地雷达独立获得的土壤含水量进行比较。在较干燥土壤条件下进行的试验中，示踪剂试验估算的土壤含水量与独立测量值8.6%（相当于23%的水饱和度）相同。在较湿润土壤条件下进行的试验中，示踪剂试验得出的土壤含水量为独立测量值12.2%（相当于32%的水饱和度）的81%。在较高土壤含水量下效能降低可能反映了对流和/或扩散传质限制对气相传输的影响。本文给出的结果表明，分配示踪剂法是一种在田间尺度测量土壤含水量的有效技术，尤其适用于土壤含水量为中低水平的场地。
