Effects Of PAM On Water Transport Of Iron Tailings Sand And Growth Of Plant Seedlings

China’s iron ore grade is low,and a large amount of waste is also generated when it is mined in large quantities.The open-pitted iron tailings not only occupy a large area of land resources,but also have serious soil erosion and serious ecological and environmental problems.The structure of the iron tailings is poor,the particles have weak cohesion,fast evaporation,poor ventilation and water permeability,which have a serious inhibitory effect on the growth of plant roots.Therefore,it is very important to study the infiltration of tailings,rationally improve the rationality of tailings,and use vegetation restoration to promote ecological restoration.Therefore,based on the field investigation of the Quanzigou Iron Tailings Ecological Restoration Base in Yuanqu County,Shanxi Province,this paper takes iron tailings as the research object,selects polyacrylamide(PAM)as the modifier,and mixes with the iron tailings according to different concentration gradients.Through the indoor soil column simulation test,the water infiltration rate of PAM(0%,0.05%,0.10%,0.20%,0.30%,0.40%,0.50%)to the tailings sand,the cumulative infiltration volume,the migration of the wet front are studied Distance,volumetric water content and evaporation transport capacity;using plant pot experiment,three different concentrations of PAM(0%,0.05%,0.1%,0.15%,0.2%)were studied on tall fescue,alfalfa,and twig The effects of shrub grass growth at seedling stage and the physical properties of tailings sand.By comparing the growth conditions of plant at seedling stage with different PAM concentrations,combined with the improvement of tailing sand physical properties,it was preliminarily determined that the tailing sand is the best suitable for growing shrub grass and suitable PAM concentration Scope,in order to provide a strong theoretical basis for soil and water conservation and ecological environment restoration in the late tailings area,the main research results are as follows:(1)As the concentration of PAM increases,the initial infiltration rate,average infiltration rate and steady infiltration rate of tailings sand infiltration decrease simultaneously;the cumulative infiltration volume and the forward distance of the wet front also decrease with the increase of concentration The law of small,from large to small,is 0%> 0.05%> 0.1%> 0.2%> 0.3%> 0.4%> 0.5%;but all infiltration parameters do not decrease with the increase of PAM concentration and are not equal gradient,but change with bulk density However,there are different turning points for reduction;the volumetric moisture content of iron tailings infiltration process decreases with varying depths as the depth of the soil layer increases.Among them,the 0-10 cm soil layer has the largest water content,which is significantly different from other soil layers;The water content of the same soil layer will increase significantly with the increase of PAM concentration,and PAM has the effect of retaining water.The test results of natural evaporation of tailings sand show that PAM has the ability to inhibit water loss,and the best water retention is when the concentration is 0.2%.(2)Bulk density has a significant effect on the infiltration performance of iron tailings.The infiltration characteristic values all decrease with the increase of bulk density,and compaction has a significant effect of reducing infiltration,which seriously weakens the infiltration performance of the iron tailings matrix.The kostiakov model can accurately simulate the infiltration process of iron tailings under different PAM concentrations.The average values of R2 and RMSE are 0.966 and 0.021,respectively.(3)The pot experiment found that when the PAM mass concentration was 0.15%,the germination rate and survival rate of the three test plants were all the highest,and the Hu Zhizi all died at the seedling stage;the plant height of tall fescue and alfalfa at 0.1%,The leaf width is the largest.PAM also has a positive effect on plant chlorophyll,aboveground and underground biomass,but the concentration is not as large as possible.Most indicators decrease when the PAM mass concentration is 0.2%.Too high a concentration will inhibit plant growth.Overall,the growth indexes of tall fescue and alfalfa added with PAM are better than the control(CK).It may be because PAM plays a role in water retention,so that the plant roots absorb more water and promote plant growth,so Tall fescue and alfalfa can be used as pioneer shrub species in the restoration of iron tailings wasteland,and it is difficult for Huzhizi to survive in the tailings sand at the seedling stage.(4)The test results of the physical properties of tailings sand show that the bulk density will decrease first and then increase with the increase of the PAM mass concentration,and it is the smallest at 0.15%concentration;from the field water holding capacity and saturated water content,the iron tails with PAM applied Ore sand is significantly increased compared to the control(CK),and the increase is most obvious when the PAM concentration is 0.15%;the application of PAM will reduce the settlement coefficient of iron tailings sand,and as the concentration of PAM increases,the settlement coefficient will increase,but The specific ascending range needs to be further studied;adding PAM to the tailings sand will increase the percentage of large aggregates and reduce the percentage of small aggregates(<0.25mm),and the agglomeration effect becomes more obvious as the concentration increases.