Research On Phytoremediation Combination Technology Remedying The Soil Polluted With Lead And Cadmium

Soil polluted with heavy metal not only affects the quality of the mankind living environment, but also endanger human health and life through direct contact, the food chain transfer and other ways. Effective prevention and treatment of soil polluted with heavy metal have arisen more and more world attention. The use of many combination technologies to strengthen phytoremediation can make up for the deficiency of single technology. Phytoremediation combination technology refers to the technology for remedying soil polluted with heavy metal by comprehensively utilizing phytoremediation with treatment of soil polluted with heavy metal. It can remove the heavy metals in the soil with little investment to a large extent, relative to the single remedy method; combination remediation is characterized with short cycle and simple operating procedures.This study is a new attempt for plant combination remedying the soil polluted with heavy metal. Based on studies of bacteria, chelator enhanced-phytoremediation effects, this paper aims to provide great theoretical and practical significances towards China’s environmental pollution treatment and ecological restoration and reconstruction.The laboratory filters out bacteria strains that are strong resistant to heavy metals Pb, Cd, and studies its activation performance, environmental impact factors and adsorption conditions. The difference expression of resistant strains and resistance genes, by adopting the Fluorescence quantitative PCR (qPCR), can provide a theoretical basis for the cloning of resistance genes. This paper makes use of physiological parameters measurement and heavy metal content analysis, expects to filter out hyperaccumulator Pb, Cd from grasses, and studies the impacts of Pb, Cd combined pollution on plants as well as the mechanism of plant enrichment Pb, Cd. This paper also researches the impacts of strains, EDDS, and EDDS/strains on plant enrichment Pb, Cd through the pot experiments, compares plant enrichment Pb, Cd abilities under different treatments, and explores the mechanism of bioremediation, in order to find more efficient and economical remediation measures and provide scientific reference and technical accumulation for sustainable treatment of heavy metal pollution. The main results are as follows:1. The screened2resistant strains JB11and JB12have strong growth potential, activation of lead nitrate, and cadmium sulfate with significant effects, the strain JB12has the highly resistance to Pb, Cd, and JB12is selected as the optimal strains for plant experiments. After physiology and biochemistry and16SrDNA sequencing analysis, JB11is identified to be enterobacteriaceae Pantoea agglomerans with Genbank accession number of JX262490. JB12 is enterobacteriaceae Burkholderia Yabunchi burkholderia cepacia with Genbank accession number of JQ346057.Studies of strain JB11and JB12biological characteristics show that the bacteria strains are generally resistant to heavy metals, antibiotics. Under the optimal culture conditions, adsorption experimental results for JB11and JB12towards Pb2+, Cd2+show that, JB11adsorption of Pb2+shall choose bacteria amount of5g/L, pH5,30min of adsorption; JB11adsorption of Cd2+hall choose bacteria amount of5g/L, pH6, adsorption of35min. JB12adsorption of Pb2+shall choose bacteria amount of6g/L, pH5, adsorption of20min; JB12adsorption of Cd2+shall choose bacteria amount of5g L, pH6, adsorption of20min.2. By using fluorescent quantitative Real-time PCR, this paper studies the genetic expression differences between JB12and Pb2+, Cd2+under the stress of Pb, Cd. Selected natural resistance-associated macrophage proteins(NRAMP) and the adjustment factor CadR of outflow gene CadCA system for objects, in order to study the transcriptional level changes of gene expression under the stress of Pb, Cd.Under the four concentrations of Pb and Cd, after JB12culturing for0.5h,2h and4h, most CadR and Nramp genes are up-regulated expressions, indicating that the stresses of CadR and Nramp genes are very sensitive to Pb and Cd, and play important roles in bacteria Pb, Cd resistance mechanism.3. This paper selects34grasses as the research object, screens hyperaccumulator of Pb, Cd. There are13species of non-hyperaccumulators relatively strong resistant to Pb single pollution,12species of non-hyperaccumulators relatively strong resistant to Cd single pollution,7species of plants relatively strong resistant to combined pollution Pb, Cd, which can be used for phytoremediation for Pb, Cd soil with combined contaminated.Solution with Pb/Cd concentration of500/50mg/kg is used to treat tall fescue and red clover seedlings, respectively determining the overground length, root length, overground dry weight, roots dry weight and chlorophyll content, activity of superoxide dismutase (SOD), peroxidase (POD) activity, malondialdehyde (MDA) content, membrane permeability (CMP), soluble protein contents and other physiological indicators after stressing for5d,10d,15d and20d. As a result, all physiological indicators have significantly changes with the stress prolonging,7species of plants has strong resistance and adaptability to lower concentration of Pb, Cd combined pollution.4.400g soil samples with different concentration of heavy metals are respectively placed into the pots, and tall fescue and red clover seeds are sew in each pot, sow for30d, after plants growing well in soil polluted with heavy metals, JB12or JB11strains are cultivated until the logarithmic growth phase, and the following four treatments are set:pouring sterile water blank control (CK), pouring sterile washed1×106cfu/g broth (JB12or JB11), pouring1.0mmol/kg EDDS, and pouring0.5mmol/kg EDDS+5×105cfu/g broth (1/2EDDS+JB12or JB11). Overground and root dry weight as well as concentration of heavy metal ions shall be weighted after harvest.The results show that JB12and JB11strains can significantly improve the biomass and Pb, Cd absorption amount of tested plant, and the increasing amount of tall fescue is greater than red clover. EDDS can improve plant overground Pb, Cd concentration and total absorption amount. Most absorption amount of plant heavy metal under the1/2EDDS+strains composite treatment is higher than strains and EDDS individual treatment.