Study On Phytoremediation Characteristics And Rhizosphere Degradation Genes In Petroleum-contaminated Soil

With the acceleration of industrial development,the petroleum pollution to the environment has become a serious problem.Recent research shows that the pollution caused by petroleum has been on the rise over the past few decades.Due to the high hydrophobicity of most petroleum pollutants,the pollution is easily absorbed by soil particles and becomes a long-term refractory pollutant in the soil.At the same time,petroleum is toxic to animals and plants,which seriously harms plant growth and animal health.Traditional physical and chemical remediation methods are costly,easily damage the soil structure,and even produce other contaminated waste when soil is contaminated.Bioremediation is an easy-to-implement,low-cost and environment-friendly repair method.Among them,phytoremediation has been proven to have a good repairing ability in the previous research.In this experiment,four plants are selected: mirabilis and ryegrass,which are resistant to petroleum pollution stress,violaceus and rice,which are weak against petroleum pollution.The petroleum is phytoremediation from three aspects: pollutant degradation rate,microbial abundance and degradation gene expression.Pollution capacity is assessed to investigate the effects of plants on soil remediation.The results are as follows:1.Gas chromatography-mass spectrometry was used to determine the levels of alkanes and aromatics in rhizosphere soils of four plants: jasmine,ryegrass,violaceus and rice,and calculate the degradation rate.Judging from the total degradation rate,Mirabilis and Ryegrass can degrade more than half of the alkane pollutants within 15 days,and the degradation effect of pollutants is more than 80% within 45 days,which can effectively degrade petroleum hydrocarbon pollution.At the same time,mirabilis and ryegrass grow rapidly,are easy to plant,have certain economic value and beautify the environment,and can become the preferred solution in petroleum-contaminated phytoremediation.2.Calculate the abundance of rhizosphere microorganisms by plate coating method and microscopic observation counting method.In the experiment,the plants promoted the microbial abundance including bacteria,fungi and actinomycetes,and increased the microbial community abundance in the soil.In contrast,mirabilis and ryegrass are better than violaceus and rice,which proves that the root systems of mirabilis and ryegrass can more effectively stimulate the aggregation of microbial communities.Among soil actinomycetes,the abundance of actinomycetes in each group showed a trend of increasing first and then decreasing.The significant increase in the abundance of actinomycetes on the 30 th day indicates that the response of soil actinomycetes to petroleum pollutants and plants was more obvious.3.Quantitative analysis of alkane monooxygenase gene alkB and naphthalene dioxygenase gene nahAc by using qPCR technology for members of soil bacteria to degrade petroleum pollutants.The results of real-time quantitative PCR showed that the relative expression of alkB gene in rhizosphere soil of all plants increased compared with the control group.Among them,the relative expression of alkB gene in ryegrass rhizosphere microorganisms was the highest,reaching 1.6 times.Similarly,the expression of nahAc genes in rhizosphere microorganisms of mirabilis and ryegrass has a significant increase compared with the bare soil,indicating that mirabilis and ryegrass can degrade polycyclic aromatic hydrocarbons in soil by promoting the expression of nahAc degradation genes.