Basic Study On Application Of Moss Spray Seeding Crust On Uranium Bearing Substrate

In this paper,through the selection of dominant bryophyte species,the optimization of nutrients and process parameters,the analysis of environmental factors,the response mechanism of bryophytes to uranium stress,and the effect of bryophytes planted in uranium bearing soil on its crust soil,the cultivation system of bryophytes sprayed on uranium bearing substrate was established.The results show that:(1)The dominant moss species in uranium mines is Didymodon vinealis var.Vinealis.Under natural conditions,at the end of cultivation,the crust coverage on the surface of loess matrix,uranium bearing loess matrix and uranium ore soil matrix can reach 73.9%,77.8%and 67.8%respectively,the plant density is 26.8 plants/cm²,28.6 plants/cm²and 24.6plants/cm²respectively,the plant height is 0.43 cm,0.42 cm and 0.36 cm respectively,and the chlorophyll a content is 0.18 mg/g,0.20 mg/g and 0.17 mg/g respectively.Didymodon vinealis var.Vinealis has the best tolerance to uranium,the fastest crust rate,high coverage and dense plants,it can quickly form crust for both simulated and actual uranium soil.(2)The results showed that moss addition and particle size had significant effects on moss crust coverage,plant density and biomass(P<0.01).For moss crust coverage and plant density:moss dosage>crushed particle size>water retaining agent dosage;for biomass:water retaining agent dosage>crushed particle size>moss dosage.The results showed that the optimal combination of moss crust additives was as follows:the amount of moss was689.44g/m²,the particle size was 103.36 mesh,the dosage of water retaining agent was3.99g/m²,the theoretical coverage was 100%,the plant density was 57.45 plants/cm²,the height of single plant was 0.4 cm,and the chlorophyll content was 0.272 mg/g.On the 60th day of cultivation,the crust coverage and plant density of the improved knop nutrient solution increased by 14%and 41.4%respectively compared with the control group.The best combination of different treatments was treatment 18,that is,film mulching shading rate 45%-Bacillus gelatinosus.At the end of cultivation,the coverage,plant density,plant height and chlorophyll a content were 99.43%,46.33 plants/cm²,0.46 cm and 0.28 mg/g,respectively.(3)The enrichment of uranium in the three bryophytes is 12.84?34.89?g/g;the enrichment of uranium in the three bryophytes is 50.72?180.44?g/g;the enrichment of uranium in the three bryophytes is 77.01?205.06?g/g.The adsorption and enrichment of uranium by bryophytes are extracellular enrichment and intracellular absorption,with extracellular enrichment as the main and intracellular absorption as the secondary.The results show that the adsorption and enrichment ability of uranium is as follows:Hypn um cupressiforme L.ex Hedw.var.Cupressiforme>Cyrto-hypnum contortulum(Mitt.)Wu>Barbula unguiculata.The results showed that uranium stress could inhibit photosynthesis and chlorophyll-a synthesis of three bryophytes in varying degrees,and reduce soluble protein content in plants;MDA content in three bryophytes was positively correlated with uranium stress concentration;the response of antioxida-nt system activity of three bryophytes to uranium stress was low promotion and highinhibition.The sensitivity of photosynthetic efficiency of three bryophytes to uranium was as follows:Cyrto-hypnum contortulum(Mitt.)>Hypnum cupressiforme L.ex He-dw.var.cupressiforme>Barbula unguiculata;the degree of uranium toxicity:Cyrto-h-ypnum contortulum(Mitt.)>Hypnum cupressiforme L.ex Hedw.var.Cupressiforme>Barbula unguiculata;the stress of antioxidant enzymes:Barbula unguiculata>Hy-pnum cupressiforme L.ex Hedw.var.Cupressiforme>Cyrto-hypnum contortulum(Mitt.)Wu.Moss crusts can change the microbial community structure of the crusts.(4)Moss crusts can improve the relative abundance of functional bacteria(nitrogen fixation,photosynthesis,metabolic C₁compounds,plant symbiosis,saprophytic)and improve the surface soil microenvironment.There was no significant difference in the dominant species among the treatments.The dominant bacteria of the four treatments were Proteobacteria and Actinobacteria,but the bacterial community composition of each treatment was different.However,the relative abundance of Actinobacteria,Bac-teroidetesand Firmicutes decreased.