| Loess is a loose deposits rich in carbonate and porous which recorded relatively continuous and complete information of climate change.As an important water resource in the loess plateau region of China,loess groundwater is directly related to the agricultural production and life in the region.Finding out the infiltration rate of loess and paleosol and discussing the conditions of groundwater enrichment and migration in loess have important practical significance for the development and utilization of groundwater resources in loess.Therefore,I selected the loess profile L1?L4 at Mingzhou town in Suide as the research object,I did the infiltration experiment,and used three common infiltration experience models to conduct fitting analysis on the experimental curve.At the same time,according to the experimental data of particle size,porosity,CaCO3 content and magnetic susceptibility of the samples collected,the influence of each index on the infiltration rate?water-bearing and water-resistance conditions of loess and paleosol were discussed.The main conclusions are as follows:(1)The average initial infiltration rate and infiltration coefficient of the study section from L1 to L4 generally show a decreasing trend from new to old.The average stable infiltration rate of the studied loess profile was 0.88mm/min,the average stable infiltration rate of the 4 layers of loess was 1.02mm/min,and the average stable infiltration rate of the 4 layers of paleosol layers was 0.39mm/min.The stable infiltration rate at the upper part of Li was the highest,which was 1.15mm/min,and the stable infiltration rate of S2 was the lowest,which was only 0.23mm/min.The stable infiltration rate of loess layer is higher than that of paleosol layers.Generally,it takes 40?80min to reach a stable infiltration state.(2)Three infiltration experiment models were used to fit the experimental curve,and we can get best fitting results by General empirical formula,which are all greater than 0.89.The fitting result is good,which shows that the general empirical formula is the best model for studying infiltration law in this area.(3)By comparing the infiltration rate of the loess profile L1?L4 in mingzhou town with that in other areas of shaanxi province,it is found that the infiltration rate from south to north of the Loess Plateau show a gradually decreasing trend.This is different from the previous understanding.The main reason is that the developmental climate of the loess in this area is colder and drier.At that time,the macropore produced by plant root holes was less and the porosity was lower than that in the central and southern regions,which led to the low infiltration rate.(4)The experimental results show that the porosity of the loess layer is larger than that of the paleosol layer and the grain size is thicker than that of the paleosol layer,which is one of the important reasons leading to the high infiltration rate of the loess and the low infiltration rate of the paleosol.It also shows that loess layer is more likely to be a water-bearing layer when saturated water exists,and the paleosol layer is more favorable to be a water-resistance layer.(5)The CaCO3 content and frequency susceptibility of loess layer in the studied section indicate loess layer developed in a relatively cold and dry climate background,pedogenesis is weaker,clay minerals are less,porosity is larger,so the infiltration rate is higher,water-bearing space develops well and loess layer is more likely to be water-bearing layer;paleosol layer was developed in a warm and humid climate,with strong pedogenesis,more clay,and smaller porosity,so the infiltration rate was low and the water-proof conditions is well,which was more favorable to be the water-resistance layer.Therefore,the difference of pedogenesis caused by different climatic conditions is the main factor determining the high infiltration rate of loess and the low infiltration rate of paleosol,and also the main factor affecting the water-bearing and water-resistance conditions of loess and paleosol. |
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