Study On The Mechanism Of Soluble Organic Matter Affecting The Biodegradation Of Pyrene

Polycyclic aromatic hydrocarbons(PAHs)refer to a class of compounds containing two or more benzene rings.They enter water and soil through sedimentation,and they can interact with dissolved organic matter(DOM).DOM is rich in resources but complex in composition.It is considered to be one of the most abundant organic components in all ecosystems.DOM can interact with microorganisms and affect the degradation process of PAHs.Electrospray ionization combined with Fourier transform cyclotron ion resonance mass spectrometry(ESI FT-ICR MS)has ultra-high resolution,and thus has the ability to analyze the composition of DOM molecules.Therefore,starting from the molecular composition and structural changes of DOM,studying the influence of DOM on the degradation process of PAHs can provide strong theoretical support for the full utilization of DOM resources and the biodegradation of persistent organic pollutants in the environment in the future.Therefore,this paper uses solid-phase extraction technology enrichment technology,selects pyrene as the PAHs model,uses ESI FT-ICR MS and spectroscopy technology to study the molecular structure and change characteristics of DOM,and studies the degradation pathways and degradation of pyrene metabolized by degrading bacteria under the action of DOM Efficiency,as well as the activity of degrading bacteria and changes in surface morphology.The main conclusions are as follows:1.Using three methods of water extraction,acid extraction and salt extraction to extract DOM from soil,the structure difference is significant.The number of molecular formulas obtained by water extraction is the largest,as many as 10,000 and more comprehensive.Among the heteroatom compounds,O_x substances account for the highest proportion of the overall compound,and N-containing compounds mainly exist in the form of binding oxygen atoms.Among them,low-oxygen O₂ and O₃ organics may be benzene polyphenols or benzene carboxylic acids;as the number of oxygen atoms increases,molecules with carboxyl molecular structures gradually increase.2.Set up DOM-pyrene and pyrene control degradation experiments.After 7 days of culture,the degradation efficiency of pyrene is about 10.5%,and the degradation efficiency of pyrene after adding DOM is about 88.5%.The addition of DOM significantly enhances the degradation efficiency of pyrene.When only pyrene is present,the compounds 4,5-pyrene dihydrodiol and 3,4-phenanthrenediol are detected;after the addition of DOM,1,2-dimethoxypyrene and 4,5-diketopyrene are detected.From this,we can infer the degradation path of pyrene:when there is no DOM,the 4 and 5 positions of pyrene are attacked,thereby opening the ring and decarboxylating;and when DOM is present,the 1,2 and 4,5 positions of pyrene are both Being attacked,this shows that DOM can stimulate the ring opening at different sites of pyrene.In addition,the use of CLSM combined with cell staining technology has observed that DOM can increase the activity of degrading bacteria in the process of pyrene degradation and increase the agglomeration phenomenon.3.The analysis of FTIR and Raman spectroscopy shows that there is an NH-?EDA(electron-donor-acceptor,EDA)force between DOM and pyrene degradation.When there is no DOM,a higher pyrene concentration is not conducive to protein and lipid.The generation of quality.The EEM results showed that when both pyrene and DOM exist,the protein and nitrogen source in DOM can be used by degrading bacteria.DOM increases its solubility and allows bacteria to directly bind pyrene.With the increase of pyrene concentration,tyrosine peaks and visible light fulvic acid peaks were detected.Corresponding to the Raman results,the related protein peaks and amino acid peaks also shifted accordingly.The observation results of cell surface morphology show that:DOM can promote the formation of biofilm between degrading bacteria,thereby improving its bioavailability.This thesis studied the composition and structure of DOM in the soil and its influence on the biodegradation of PAHs.It is shown that DOM can make pyrene degrade at two sites(C-1,2 and C-4,5),and improve It improves the activity of degrading bacteria and promotes the production of extracellular polymers,thereby greatly increasing the degradation efficiency of pyrene.This provides a theoretical basis for further research on the migration and transformation of persistent organic pollutants such as PAHs in the soil.