Study On Soil Improvement And Remediation In Abandoned Mining Area By Plant With Sewage Sludge

In recent years,with the shortage of land resources in China,the treatment of abandoned mine soil has gradually attracted people's attention.Phytoremediation is widely used in mine soil remediation due to its environmental friendly and less damage.However,the content of soil nutrients is low in phytoremediation,which is not conducive to plant survival.In theory,the application of sewage sludge can make up for the shortcoming.In this paper,the Commelina communis was used to repair the abandoned mining soil by the application of sewage sludge.Firstly,the effect of sewage sludge on soil improvement in mining area was studied.Then the remediation effect of Commelina communis on heavy metal contaminated mineral soil was analyzed.Finally,the absorption and accumulation mechanism of heavy metals by Commelina communis under Cu and Zn pollution was discussed.The main conclusions are as follows:(1)The addition of sewage sludge improved soil structure,increased nutrient content and promoted plant growth.At the same time,the pollution of heavy metals in soil had also been aggravated to some extent.When the sewage sludge content was controlled with 15%,it was feasible to improve the soil in mining area.The soil p H was stable at 6.6-6.7,the bulk density of soil was 1.39g/cm3,and the soil nutrient content reached the level I of soil(dry land)fertilizer grading reference indexes.The increase rates of Cu,Zn,Pb and Cd in soil were 1.16%,6.16%,4.01% and 1.58%,respectively.(2)The growth of Commelina communis improved soil environment and increased soil enzyme activity.In addition,Commelina communis showed a certain removal ability to Cu,Zn,Pb and Cd in the soil.After 120 days,the removal efficiency of Cu and Zn by Commelina communis were 27.5% and 18.3%,respectively.The removal rate of Pb and Cd by plant was about 13%,which was relatively low.(3)Cu and Zn were indispensable trace elements for the growth of Commelina communis.Low concentrations of Cu and Zn had a synergistic effect,which promoted the growth of Commelina communis and enhanced its accumulation to heavy metals.And the accumulation method of plant was mainly to transfer heavy metals to its above-ground part for fixation.On the contrary,high concentrations of Cu and Zn strongly inhibited the physiological activities of Commelina communis.The accumulationn of Cu and Zn in Commelina communis was mainly reflected in the antioxidant enzyme system.The antioxidant enzymes such as SOD,POD,and CAT in Commelina communis could decompose active oxygen generated by the accumulation of heavy metals in the plant body,avoiding damage to its own tissue,thereby achieving absorption and accumulation of Cu and Zn.