玛纳斯河流域土壤斥水性及其影响因素

土壤斥水性(SWR)阻碍入渗及再分布过程.虽然斥水土壤在世界广泛存在,但其产生机理并不明确.本文采用滴水穿透时间(WDPT)法、酒精摩尔浓度(MED)法和接触角(θ)法测定了新疆玛纳斯河流域典型土壤的SWR指标,其中θ的测定采用高度法和质量法.对WDPT是否受烘干及不同容重的影响进行对比,探讨各SWR指标之间的联系,并分析了SWR的关键理化性质影响因子,探讨土壤斥水的机理和原因.结果表明: 高容重土壤的WDPT值更大,烘干土壤的WDPT值比风干土壤大;3种SWR指标(WDPT、MED及θ)之间有一定的相关关系,但MED与θ的相关性并不明显,表明各SWR指标之间虽有一定联系,但表征方面具有差异性;采用高度法和质量法测量水与土壤的θ值时,高度法的θ值大于质量法,高度法之间重复差异小于质量法;使用正辛烷作为参比溶液测量水与土壤的θ值时,其重复的差异较小,低于无水乙醇;在多种理化性质中,黏粒含量比其他土壤属性更显著地影响WDPT和θ;K⁺]、Na⁺]均与θ呈正相关;蒙脱石含量与WDPT、MED呈负相关.综上,土壤SWR的测定方法中,WDPT法操作简单但易受影响;MED法缩短了入渗时间但试验过程耗时;接触角法操作复杂,结果相对精确,采用正辛烷作为参比溶液的高度法更可靠.建议采用多种指标综合表征土壤斥水性.

Water repellency and its influencing factors in Manas River Basin,China

Soil water repellency (SWR) impedes the processes of soil water infiltration and redistribution. Although water repellent soils exist extensively in the world, its causes were not very clear. In this research, three measurement methods including the water droplet penetration time (WDPT), the molarity of ethanol drop (MED) and the contact angle (denoted as θ below) methods, were applied to obtain different SWR indices for the tested soils collected in Manas River Basin, Xinjiang Uygur Autonomous Region, China. The height method and the mass method were conducted to measure θ values. WDPT values of different soil samples were compared to investigate whether WDPT values were affected after being oven-dried or by different bulk densities. The relationships among three SWR indices (WDPT, MED and θ) were compared, and the major soil physico-chemical properties which influenced SWR were analyzed to discuss the intrinsic mechanism that caused SWR. The results showed that WDPT values of higher bulk density were larger than those of lower bulk density, and WDPT values of oven-dried soils were larger than those of air-dried soils. There were correlations between the three SWR indices of WDPT, MED and θ, but MED was insignificantly related to θ, which showed the differences among various SWR indices, although they were related to each other. When measuring θ values of soil-water, θ values obtained using the height method were larger than those obtained using the mass method, and the differences of θ for the three replications with the height method were smaller than those with the mass method. When using octane as the reference liquid for measuring θ values of soil-water, the differences of the three replications were small, being lower than those using ethyl alcohol. Among the studied multi-physico-chemical properties, clay content affected WDPT and θ values more significantly than other soil physico-chemical properties. Concentrations of K⁺ and Na⁺ were both positively correlated to θ va-lues, while the content of montmorillonite was negatively correlated to WDPT and MED values. In summary, among the three SWR measurement methods, the WDPT method was quite simple in operation but was susceptible, the MED method shortened the infiltration time but was time-consuming in operation, and the contact angle method was complicated in operation but the results were relatively accurate. When using octane as the reference liquid for the height method, it was more reliable than using the other liquids. Because each index had its inherent nature, it was suggested to use multiple indices to characterize SWR comprehensively.