Plants Combined Fungus In Situ Simulation To Repair Heavy Metal Cd Pollution In Rare Earth Tailings

The rare ion-adsorbed rare earth ore in the world is distributed in Ganzhou,Jiangxi.Its mining process is mainly in-situ leaching.Long-term in-situ leaching had caused great pollution risks to the local soil environment.In this thesis,a typical ionadsorbed rare earth tailings of the in-situ leaching process in Xunwu County of Ganzhou was taken as the research object.The research on the plant combined fungi to control heavy metal Cd pollution in the mining area is carried out.By adding exogenous Cd,different gradients(0,0.2,0.6,1 mg/kg)of simulated Cd pollution,using ramie and paspalum as host plants,combined with two kinds of fungi widely present in rare earth mines to study the effects of Cd pollution control and the host plant growth using descriptive statistics,mean analysis,nonparametric test and principal component analysis to explore the effect of different plants and fungi on the treatment of heavy metal Cd pollution in rare earth mines,and the possibility of applying it to bioremediation of soil contaminated by heavy metals.The results were as follows :(1)Two kinds of fungi widely existed in rare earth mines in the south of Ganzhou:Penicillium oxalicum and Trichoderma sp.(2)The growth rate of ramie combined with two fungi: Ramie conbination Penicillium grew best.The dosage of 0.2 mg/kg of exogenous Cd had a certain promoting effect on the Ramie's height and the number of leaves.Under 0.2 mg/kg Cd,the plant height,leaf length and leaf width of the Penicillium group were obvious advantages than other groups.Compared with the control group of 0 mg/kg Cd,the plant height,leaf length,and leaf width of each group's plants were all increased.(3)Changes in soil nutrients of ramie combined with two fungi: little change in soil total phosphorus and total nitrogen,regular application of fertilizer can maintain plant growth,organic matter content was significantly reduced,and ramie nitrogen fixation ability was weak.The cumulative interpretation of environmental factors PCA in the planting Ramie planting area in the principal component sorting diagram reached93.2%,and the main influencing factors were nitrate nitrogen,total nitrogen and ammonium nitrogen,and Cd content before planting.(4)The effect of ramie combined with two fungi on Cd treatment: the Ramie conbination Trichoderma group had the strongest average Cd absorption capacity(78.11%)among the four groups.With regard to the Cd content of the Ramie ground and underground parts: at the dosage of 0-0.6 mg/kg Cd,both the Trichoderma group and the Penicillium group can improve the Ramie transport capacity of Cd.At the dosage of 1 mg/kg Cd,the Penicillium was significantly improves the ability of Ramie to transport Cd(2.73).Moreover,the remaining Cd content in the soil after planted in the non-bacterial group was higher than that in the inoculation group,and the inoculation group was beneficial to reduce the soil Cd content.(5)In terms of growth amount of the two fungi combined with Paspalum:Paspalum growed the best in the Trichoderma group,and with the increase of the Cd gradient,the plant length and the number of plants were increasing;the number of plants in the added fungus group is more than that in the non-added fungus group Fungus added can increase the growth of paspalum.(6)Changes in soil nutrients of the two species of fungi combined in the paspalum:the total phosphorus content of the soil at the 0.6 mg/kg Cd gradient of the Trichoderma group increased significantly,and the rest remained basically the same as before planted.The content of was significantly lower than before planted.Compared with Ramie,Paspalum had a certain ability to improve soil nitrogen fixation.The cumulative interpretation of environmental factors PCA in the planting paspalum area in the principal component sorting diagram reached 69.5%.The main influencing factors were plant height,nitrate nitrogen,ammonium nitrogen and SOD content.(7)Paspalum combined with two fungi to treat Cd: In the process from seed germination to seedling growth,Paspalum didn't have a strong ability to absorb Cd,and the ability to remove Cd in the soil.The ability of remove Cd didn't exceed 50% on average,and the ability to absorb Cd was even low at 15%,the Paspalum combination the two fungi had the highest Cd absorption capacity(20.16%),but the biomass of Paspalum inoculated with Trichoderma was high,and Trichoderma had the effect of promoting seed germination.