Study On Remediation Of Cd Contaminated Soil With Amaranthus Hypochondriacus L. And Microorganism

In order to study out a remediation technique which is suitable for Cd contaminated soil,this experiment first studied the germination of amaranth?Amaranthus hypochondriacus L.?seeds under different Cd stresses and seek out the reasonable sowing method.Then set different cutting intensity to cut the stubble grain of amaranth and select the best cutting way;secondly,the combination experiments using the microorganisms of Pseudomonas aeruginosa,Enterobacter cloacae,Paenibacillus polymyxa and Bacillus mucilaginosus krassilnikov were under the Cd concentration of 25mg/L to select the best microbial combination.Finally,amaranth was treated with optimal mowing and dominant microorganism combination technology.Last obtained the technology of combined remediation of cadmium contaminated soil by grain amaranth and microorganisms.The conclusions are as follows:?1?The experiment on seed germination of amaranth under Cd stress and the selection of sowing method:Seeds'germination under Cd concentration of 0,0.5,2.5,12.5mg/L was conducted.The germination rate,germination potential,germination index,vigor index,seedling root length and seedling height were all analyzed.It was found that the germination rate and germination index first increased and then decreased with the increase of Cd concentration.The germination potential,vigor index,root length and seedling height were all decreased.Low concentrations of Cd promoted germination rate and germination index,but high and low concentrations of Cd were not conducive to seedling growth.Therefore,this experiment decided to adopt seedling transplanting method to sow seeds.?2?The selection of the best cutting techniques:Light cutting?at the stubble height of 50cm?,moderate cutting?at the stubble height of 30cm?and heavy cutting?at the stubble height of10cm?were set to cut the stubble of amaranth.It was found that the plant height,biomass and plant Cd enrichment of grain amaranth were all increased under moderate mowing treatment.As a result,moderate mowing was considered as the best mowing method.?3?The selection of dominant microbial combinations:Pseudomonas aeruginosa,Enterobacter cloacae,Paenibacillus polymyxa and Bacillus mucilaginosus krassilnikov were combined under the Cd concentration of 25mg/L to detect the ability of symbiotic effect,iron carrier and IAA secretion.It was found that combination 8?The combination of Pseudomonas aeruginosa 0.3mL,Enterobacter cloacae 0.2mL,Paenibacillus polymyxa0.3mL and Bacillus mucilaginosus krassilnikov 0.1mL?had the better secretion capacity than other combinations.?4?The results of the combined remediation test of amaranth and microorganism:Amaranth was integrated with the combination of medium mowing and the best dominant microorganism,and it was found that the plant height and biomass of amaranth which treated with this technology reached the maximum value of 241.67cm and 593.05g/plant.Cd content in root,stem and leaf tissues reached the optimal level of 4.48mg/kg,3.58mg/kg and7.1mg/kg.The transfer and enrichment coefficients reached the maximum values of 12.34and 4.37,reaching the superrich plant standard.The maximum biomass per hectare was37077.49kg/hm²,and the total amount of Cd absorbed by plants was 159.74g/hm²,after the test,the technology reduced the content of Cd in the soil to 0.564mg/kg,with the best Cd removal rate of 4.57%and the best remediation effect.In summary,the experimental results showed that the integrated technology had the best remediation effect.The specific operations are as follows:?1?Seedling transplanting and sowing method:Select round and full seeds,soak them in warm water for 14h,remove them to dry and mix them with fine sand at the proportion of1:10 to sow seeds,evenly cover the nutritive soil,and observe the emergence of seedlings.?2?Optimal mowing treatment:The seedlings were transplanted and supplemented with 5⁶cotyledons at 15cm,the plant and row spacing were 40cm×40cm,and the planting density was 62520 plants/hm².Plant height of 60⁷0cm,soil to prevent lodging;The plant height was 90¹00cm and the stubble height was 30cm.?3?Preparation of the dominant microorganism:Four kinds of OD₆₀₀?1.0 microorganisms were mixed in the volume of Pseudomonas aeruginosa?300mL?,Enterobacter cloacae?200mL?,Paenibacillus polymyxa?300mL?and Bacillus mucilaginosus krassilnikov?100mL?to make a bottle of 900mL biological bacterial liquid.?4?Dominant microorganism treatment:10mL/plant biological bacteria liquid was applied to the root after mowing,and was treated once for 7d,four times continuously,and harvested at the rate of 45d.