The Root Secretion Effects On Microbial Degradation Of Polycyclic Aromatic Hydrocarbons

With the wide range of sources,polycyclic aromatic hydrocarbons can cause serious harm,which not only influences the ecological environment,but poses a threat to human health.The harm of polycyclic aromatic hydrocarbons has been paid a great attention from all over the world,therefore the research of PAHs pollution has become a hot spot.So this paper mainly studies the bioremediation of polycyclic aromatic hydrocarbons in the soil.The bioremediation is used to save energy and expense.Its overall effect on environment is so little as to be unnoticeable.Moreover it also can be used for the pollution treatment of large area.The above advantage is easily accepted by people,and is widely used to repair the polycyclic aromatic hydrocarbons in the soil.This thesis will further illustrate the specific impact of the plant root secretion and the microbes combined remediation in the degradation of polycyclic aromatic hydrocarbons.Firstly,root secretion,microbes and pollutants have been added in the simulation experiment of liquid,with the gradient addition of root secretion,which have been used to study the effect of different microbes' degradation of PAHs by adding different plant root secretion.Secondly,adding plant root secretion and microbes with good degradation in the simulation experiment of soil,was to move forward to confirm the experiment.What's more,the specific influence of the synergy between plant root secretion and the microbes was shown in the simulation experiment which was much closer to practice.Meanwhile,in the simulation experiments of soil,the influence on community structure in soil was also studied,and the type of bacteria was identified by PCR,DGGE,and sequencing.The result showed that the synergy between plant root secretion and the microbes can actually promote or enhance the degradation of polycyclic aromatic hydrocarbons in the soil;Mycobacterium Ml can degrade the bacteria of polycyclic aromatic hydrocarbons,which had significant power;Clover,soybeans,corn roots in combination with Mycobacterium Ml can increase the rate of the degradation of polycyclic aromatic hydrocarbons,and the effect of synergy was better than adding plant roots or microbial separately;besides,different concentration of plant roots affected the rate of the degradation of polycyclic aromatic hydrocarbons,which were acceptable in the simulation experiments of both liquid and soil.Especially,in the simulation experiments of soil,the effect of root secretion was more significantly,which might have something to do with aged or locked pollutants in the soil.Adding the microbes could change the community structure of soil bacteria.Microbial treatment promoted or enhanced the degradation ability of the strains in the soil,and increased the density of microbes.This study showed it's feasible that the ability of PAHs degradation dominant microbes and specific PAHs repair plant were screened,to improve the efficiency of the degradation of PAHs in soil.We should choose suitable species of microbes and plants in the process of repair.But degrading bacteria and plant adaptability to field soil pollution is still a key limiting factor,in future research we need to develop a variety of microbes and plants of degradation to adapt to the environmental conditions,in order to achieve better repair effect.