Research On Microbiological Remediation Of PCP Under Different Pollution Environments

Pentachlorophenol(PCP),as one of the organochlorine pesticides,has been widely used as fungicide,molluscicide,algaecide,pesticide,herbicide and wood preservatives,etc.,thereafter it enters the environment such as water,soil and the sediment of the rivers and lakes.But due to its steady chemical feature,long persistence and high toxicity,it is of wide toxicity and mutagenicity to human being and animals.PCP is considered as the one of the main POPs in the environment and one of the priority pollutants.Therefore the biohazards,transportation,transformation and degradation of PCP have been the hot topic all over the world.While white rot fungi have shown great potential in the degradation of the hard-to-be-degraded organic matters like PCP.Because this kind of Basidiomycetes has very special features,such as non-specific,degrading pollutants completely,wide range of target pollutants,suitable for both liquid and solid substrate and excreting special extracellular enzymes,it can degrade many kinds of xenobiotics.Among the researched fungi,Phanerochaete chrysosporium is the one receiving the most concern.According to different typical environments for PCP,that is agricultural waste, wastewater,river sediment and soil,free Phanerochaete chrysosporium,laccase generated from Phanerochaete chrysosporium and immobilized Phanerochaete chrysosporium were respectively added for the treatment and bioremediation.The adsorption kinetics and thermodynamic of Xiang river sediment on PCP was also investigated,which can provide the theoretical reference for the assessment and prediction of the transportation,treatment of PCP in water environment.Firstly,the degradation effect of Phanerochaete chrysosporium on PCP and lignin in agricultural waste with straws through solid-state fermentation was investigated.It is found that the change of biomass,enzyme activities and degradation ratio of PCP and lignin are in a similar tendency.In the first 10 days the biomass and enzyme activity increased quite fast and reached the maximum on the 10^thday and afterwards they decreased gradually.The degradation ration of PCP and lignin changed correspondingly.It means there's close relationship among the strain growth and enzyme activity and degradation ratio.By ultraviolet spectrum and infrared spectrum analysis it can be seen that the lignin structure in the straw has been destroyed by P.chrysosporium,the difficult-to-be-degraded big-molecule long-bond hydrocarbons were cutted into small-molecule short-bond hydrocarbons.That means P. chrysosporium can degrade both PCP and straw lignin.Secondly,the optimum condition for the laccase generation by P.chrysosporium was investigated,and the laccase generated under the optimum condition was applied in the treatment of the PCP-polluted water.Although it has been considered in the past that P.chrysosporiumon can not generate laccase,the result obtained in the experiment proved that under specific condition laccase can be generated by P. chrysosporium.The optimum condition for the laccase generation is as follows:the mixture of banana skin and corncob is 1∶2 and with the inducer of 0.4mM CuSO₄. Using either CuSO₄ or veratryl alcohol as inducer the laccase activity will be enhanced.The draft and purified laccase obtained under the above condition were applied for the PCP-contaminated water treatment.The purified laccase functioned better than draft laccase,and the medium-ABTS could also help the function of laccase.Making use of low-cost agriculture waste as the fermentation substrate to produce enzyme is a both economical and high-efficient method,that is it can not only solve the environmental problems caused by the agriculture waste,but also produce valuable enzyme.Besides,the treatment effect of immobilized and free P.chrysosporium on PCP and the change of parameters,such as organic matters,C/N,lignin,cellulose,humus, seed germination and microbe biomass in the composting were investigated.After 2-month composting,the compost is mature and the toxicity of PCP is also almost eliminated.It can be concluded from the experiment that composting is an effective bioremediation method for the PCP-polluted soil and adding P.chrysosporium will also facilitate the degradation of lignin,cellulose and the generation of humus,and the immobilization method is also feasible in the bioremediation.Finally five sediment samples from Xiang river in Changsha was analyzed and the physical and chemical features and adsorption kinetics and thermodynamic of Xiang river sediment on PCP was also investigated.The linear model can fit the adsorption kinetics better than Parabola model.The adsorption isotherm was also obtained and fitting with linear adsorption model,non-linear Freundlich adsorption model,Dual Reactive Domain Model,from which it can be concluded that the adsorption of PCP on sediment complies with Freundlich adsorption model,which is non-linear.The adsorption calorific value was obtained by the thermodynamic experiment and it can be concluded that the main adsorption mechanism is the physical adsorption.The adsorption is mainly the action of hydrophilic bond, meanwhile van der waals forces,hydrogen bond forces and dipole bond forces may also exist.The result can be provided as a reference for the estimation,assessment and prediction of the transportation,artificial control of PCP in water environment.