Effects Of Water-retaining Agent On Water Evaporation Of Improved Tailings And Water Use Characteristics Of Seedlings

Heavy metal lead is an important resource for the development of the country,but the problem of soil pollution brought about by mineral mining cannot be ignored.Since the 1980 s,Vegetation restoration and plant ecological restoration technology has been proposed as a lowcost,good benefit,and environmentally sustainable technology,and scientists have conducted in-depth research from different perspectives.However,there are few studies and applications of water retention in the tailings like how to prevent the leakage,reduce the evaporation of moisture in tailings,and improve the moisture status of vegetation root layer.The effects of the concentration of water-retaining agent and the moisture content of the particulate matrix on the water use status of the vegetation on the tailings and the coupling relationship between the two have not been reported.P.orientalis and A.fruticosa have the characteristics of drought tolerance,salinity tolerance,lead resistance and small transfer coefficient.Together with forestry water-retaining agents,they have great potential to solve the difficult problem of vegetation restoration in mining areas in the arid and semi-arid areas of Northwest China.And to improve the ecological environment has important significance.In thesis,the effects of water-retaining agent and substrate water content on the moisture content of the lead and zinc tailings sand substrate and the water use characteristics of P.orientalis and A.fruticosa were explored through the matrix water evaporation test,field test and pot experiment.Determine the optimal water-retaining agent concentration and the moisture content of the growth of P.orientalis and A.fruticosa in the modified lead-zinc tailings sand matrix.Concluded as follow:(1)The application of water-retaining agent can effectively increase the moisture content of the matrix and reduce the evaporation of water.The water content of the substrate is in the range of 7.89% ～ 13.81%,and the evaporation decreases with the increase of the concentration of water-retaining agent;the water content of the substrate is in the range of 17.95% ～ saturated irrigation,and there is no significant difference in the evaporation of substrate water between different water-retaining agent concentrations.When the concentration of water-retaining agent is 0.87%,the average substrate water evaporation is the smallest,and when the substrate water content is 13.81%,the evaporation is the smallest.In the matrix water evaporation test,the treatment with the best water retention effect is the concentration of the water retaining agent 1% and the substrate moisture content 13.81%.(2)Field test results showed that the plant height and ground diameter of A.fruticosa were the highest when the concentration of water-retaining agent was 0.1%,and the photosynthetic physiological index was the best when the concentration of water-retaining agent was 0.55%.P.orientalis had the largest growth indexes such as plant height and ground diameter at 0.55%water-retaining agent concentration,and the best photosynthetic physiological indexes at 0.1%.(3)Through the pot experiment,the model between the water-retaining agent and the substrate moisture content with the growth and physiological indicators of A.fruticosa and P.orientalis was established;the difference between the effects of the concentration of waterretaining agent and the water content of the substrate on each index is clarified;the combination of the water-retaining agent and the water content of the substrate when different indexes are optimal is obtained.(4)The principal component analysis results of pot experiment show that the best waterretaining agent concentration is 0.19%,and the best substrate water content is 16.18% when using A.fruticosa for vegetation restoration in lead-zinc tailings dam.When using P.orientalis for vegetation restoration,the best treatment condition is 0.10% of water retaining agent,substrate water content 19.73% and the follower is 0.10% of water-retaining agent,and 7.89%of the water content.(5)After comprehensively considering the field test results and the main component analysis results of the pot experiment,it is considered that the water retention agent concentration of A.fruticosa should be 0.19% and the substrate moisture content 16.18%;the P.orientalis should be 0.10% and the substrate moisture content 7.89%.