Effect Of Desulfurization Gypsum On Water Movement Characteristics And Parameters Of Saline Soils In The Yinbei Plain

Water infiltration affects the water distribution and solute migration process of saline soils,and the study of water movement characteristics and parameter changes of saline soils can provide reference for clarifying the water and salt transport law of saline soils and formulating reasonable improvement measures for saline soils.In actual production and life,people often improve the soil according to the degree of salinization.Desulfurization gypsum,as a commonly used soil conditioner,is widely promoted because of its high resource utilization efficiency and large production volume,but the water movement characteristics and parameter changes of the soil after adding desulfurization gypsum are not clear,so it is necessary to study the water movement characteristics and parameter changes law of the soil after adding desulfurization gypsum.For the above reasons,this study used a combination of indoor simulation tests and mathematical models to investigate the characteristics of vertical one-dimensional infiltration,horizontal one-dimensional infiltration,changes in moisture characteristics curves and model parameters of saline soils under six groups of treatments with the addition of desulfurization gypsum:0%(T0),1.5%(T1),3%(T2),4.5%(T3),6%(T4)and 7.5%(T5).The method of determining model parameters.The main research contents are as follows.(1)Desulfurized gypsum addition slowed down soil moisture infiltration process.According to the one-dimensional vertical infiltration experiment,the cumulative time spent in the 1.5%to 7.5%treatments increased by 9.09%,13.64%,22.73%,27.27%and 36.36%,respectively,compared to 0%;the magnitudes of the coefficients of determination(R2)of the four infiltration models were:general empirical model>Kostiakov model>Philip model>Horton model.Horton model,the infiltration rate S in the Philip model gradually decreases with the increase of desulfurization gypsum addition ratio;the water content of soil profile decreases with the increase of desulfurization gypsum ratio at the same soil depth;the one-dimensional algebraic model can better simulate the changes of water content of soil profile in different treatments.(2)The addition of desulfurized gypsum changed the horizontal imbibition characteristics and water movement parameters of saline-alkali soil.The results showed that the addition of desulfurization gypsum slowed down the soil water infiltration process,and the cumulative infiltration volume and moisture front transport distance of each treatment gradually decreased with the increase of desulfurization gypsum addition ratio;the power function and Philip model could better fit the water absorption characteristics of saline soils under different desulfurization gypsum addition ratios;with the increase of desulfurization gypsum ratio,the saturated water content of soil increased and the saturated hydraulic conductivity decreased in turn.The soil water holding capacity was significantly improved;in the Brooks-Corey model,the shape coefficient n gradually increased,the inlet suction hd gradually decreased,and the soil aeration was enhanced;under the same water content,the soil water diffusivity decreased as the desulfurization gypsum ratio increased.(3)The addition of desulfurized gypsum changed the distribution of soil pores.Soil moisture characteristics curves showed obvious variability with different desulfurization gypsum addition ratios,in the higher suction section(S>20kPa),the curves of each treatment were basically parallel and the differences in specific water capacity were small;in the low suction section(S<20kPa),the curves of each treatment differed significantly in shape and there were obvious differences in specific water capacity;soil equivalent pore size decreased gradually with desulfurization gypsum addition,compared with T0,T1,T2,T3,T4 and T5 treatments.At the same time,the number of soil macropores decreased after the addition of desulfurization gypsum,and the soil water holding capacity increased.The results of different models(absolute coefficients,sum of squares,root mean square error and mean absolute error)were analyzed,and it was found that the van Genuchten model had better applicability than the Brooks-Corey model in this study,and the VGB(m,2/n)model in the van Genuchten combined model had the best fitting effect.(4)The soil water movement parameters simulated by different mathematical models and data from different sources differed significantly.The results show that the horizontal infiltration data are more suitable for fitting the soil infiltration rate;the Buridne model(DB),Mualem model(DM)and Brooks-Corey model(D)of different treatments can fit the soil moisture diffusivity,but the related fitting models are mostly image-only models,and there is no satisfactory explanation mechanism yet,so the applicability of the models needs to be determined based on a large amount of experimental data;the Brooks-Corey model is more suitable than van Genuchten model to simulate unsaturated soil hydraulic conductivity.