冻融循环与沸石掺配对黑土物理性质的影响

Effects of freeze-thaw cycles and zeolite blending on black soil physical properties

冻融循环作用是东北黑土区发生土壤侵蚀的原因之一,施加土壤改良剂是减弱土壤侵蚀的有效方法。该研究以未经冻融循环作用和未经沸石掺配的黑土作为对照,将天然沸石与黑土按不同比例掺配,探究冻融循环作用和沸石掺配对黑土物理性质的影响,研究表明:1)冻融循环作用增大黑土容重、粘聚力、微孔占比、次大孔占比,减小土壤总孔隙度和内摩擦角,沸石掺配可以降低冻融循环作用对除内摩擦角以外土壤物理性质的影响;2)沸石掺配黑土增大黑土容重、粘聚力、内摩擦角、微孔占比,减小土壤总孔隙度,冻融循环作用对沸石掺配黑土的作用会产生负面影响,但是随着沸石掺配比例增大,冻融循环作用的影响减弱。

The freeze-thaw cycle is one of the causes of soil erosion in the black soil region of Northeast China.The application of soil conditioner is an effective way to reduce soil erosion.Natural zeolite is an environmentally friendly material and soil conditioner with a wide range of sources,low prices,non-toxic or harm.In this study,the black soil of the Songliao Plain of Northeast China was taken as the research object.Random sampling was carried out at multiple sites in the experimental farmland.Soil moisture content was determined by drying method.The samples of black soil were dried after debris removal.According to the percentage of aggregates of different grain sizes,the soil was reconstructed after sieving.The natural zeolite and the black soil were thoroughly stirred and mixed according to the mass ratio of 0,5%,10%,15%,20%,then the mixed soil samples were used for pot experiment and soil column.The potted soil and soil column were placed in a temperature-adjustable freezer to simulate the freeze-thaw cycle.The initial soil water content of potted soil and soil column was 22.5%,which was consistent with the soil water content of cultivated land when soil was sampled.In this study,freeze-thaw cycles were controlled for 0,1,3,5 and 7 times,and the same proportion of zeolite mixed with black soil was repeated twice under the same freeze-thaw cycles.The effects of freeze-thaw cycles and zeolite blending on black soil physical indices were studied by comparing the black soil without freeze-thaw cycles or without zeolite blending.Soil physical indexes include soil bulk density,soil total porosity,soil pore distribution,and soil cohesion force and soil internal friction angle.Soil bulk density was measured by ring knife method,soil total porosity was calculated by empirical formula,and soil pore distribution was measured by vacuum freeze-drying and mercury intrusion meter method.Soil cohesion force and soil internal friction angle were determined by triaxial shear test.All indicators were averaged by two repetitions.The research shows that:1)For the black soil without zeolite addition,freeze-thaw cycles increase soil bulk density,soil cohesion force,micropore and sub-macropore,decrease soil total porosity,soil internal friction angle,mesopore,macropore and average pore diameter.Zeolite blending can reduce the effect of freeze-thaw cycles on soil physical indexes except soil internal friction angle.The larger proportion of zeolite,the more obvious effect of reducing the effect of freeze-thaw cycles.2)For the black soil that has not experienced freeze-thaw cycles,soil bulk density,soil cohesion force,soil internal friction angle,soil micropores increase,soil total porosity,mesopores and average the pore diameter decreases after zeolite blending.The effect of freeze-thaw cycles on the effect of zeolite-modified black soil will have a negative impact.However,as the zeolite blending ratio increases,the effect of freeze-thaw cycles weakens.This study can lay a foundation for the follow-up study of soil freeze-thaw cycle,and also provide a reference for soil improvement in the black soil region of Northeast China.