重庆沙溪庙组紫色土土壤基质和优先流入渗的定量测算

Quantitative measurement and calculation of soil matrix and preferential infiltration in Shaximiao purple soil,Chongqing

优先流在野外条件下普遍存在,定量区分基质和优先流入渗可深入认识土壤入渗过程。本试验采用表置式环式入渗仪,选取重庆沙溪庙组紫色土为研究对象,测量土壤基质入渗和总入渗,并计算优先流入渗率,在此基础上分析基质入渗和优先流的定量关系,并将试验结果与前人研究结果进行对比分析,以验证方法的合理性。试验结果表明:在入渗过程中,土壤初渗阶段(0~10 min),优先流入渗率是基质入渗的1.1~1.7倍,优先流占主要优势;随着入渗的进行(10~60 min),优先流入渗率和基质入渗的比值逐步减小,优先流入渗率是基质入渗的0.5~1.6倍;稳渗阶段(60~90 min),优先流入渗率是基质入渗的0.2~1.0倍,基质入渗占主要优势。土壤基质和优先流入渗在沙溪庙组紫色土区水文循环过程起着同等重要的作用。Philip和Kostiakov入渗模型较好地拟合试验点基质入渗过程(R2分别为0.88和0.93,P<0.01)。表置式环式入渗仪对于定量评价优先流特征有较好的应用价值,能够很好的适用于沙溪庙组紫色土入渗性能的测量。

[Background]Preferential flow is prevalent in field conditions,and quantitative differentiation of matrix and preferential flow can provide basic data for soil infiltration process and hydrologic cycle of Shaximiao purple soil.[Methods]We used a surface ring infiltration meters and selected Shaximiao purple soil area in Chongqing as the research object to measure soil matrix infiltration rate(im),total infiltration rate(it),and to calculate the preferential infiltration rate(ip).The success of matrix infiltration measurement was determined by excavating wetted soil via matrix infiltration.The feasibility of replacing the preferential flow process with the matrix infiltration process of adjacent soil was verified by calculating the spatial variability of matrix infiltration.On this basis,the quantitative relationship between matrix infiltration and preferential flow was analyzed,and the experimental results were compared with previous studies to verify the rationality of the method.[Results]1)For im,the initial one is in 480.0-900.0 mm/h,the steady one is in 341.4-403.2 mm/h,the average one is416.3-513.7 mm/h,and the cumulative infiltration is 657.2-805.9 mm.For it,the initial one is984.0-2470.8 mm/h,the steady one is 359.4-720.0 mm/h,the average one is 648.2-1239.3 mm/h,and the cumulative infiltration is 966.2-1898.1 mm.For ip,the initial one is 504.0-1570.8 mm/h,the steady one is 18.0-316.8 mm/h,the average one is 231.3-725.8 mm/h,and the cumulative infiltration is 309.0-1092.7 mm.2)Among the infiltration model fitting parameters(S,K,a,b),imand cumulative infiltration(CI)characterizing soil matrix infiltration process,the coefficient of variation(CV)for S is maximum 15.6%.The spatial variation coefficient of steady infiltration and cumulative infiltration rate is 8.9%and 10.4%,respectively,indicating that the spatial variation coefficient of imis small.3)In the initial stage(0-10 min),ip/imis 1.1-1.7,the preferential flow infiltration is dominant.As the infiltration continues(10-60 min),ip/imdecreases,ip/imis 0.5-1.6.In the steady infiltration stage(60-90 min),ip/imis 0.2-1.0,and the matrix infiltration is dominant.4)Using the Philip and Kostiakov infiltration models to fit the matrix infiltration process of the experimental sites,R2 is 0.88 and 0.93,respectively,P<0.01,these two models fit well for the im.[Conclusions]Soil matrix and preferential flow play an equally important role in the hydrological cycle of purple soil.The surface ring infiltration meters can be well used for measuring the infiltration performance of Shaximiao purple soil in Chongqing.