Dissolved Organic Matter-mediated Photodegradation Of Anthracene And Pyrene In Water

With the development of China's economy,"made in China" has risen rapidly,but it has also been accompanied by more pollution in manufacturing plants,including all kinds of hard-to-remove pollutants such as polycyclic aromatic hydrocarbons(PAHs)that have a bad impact on the ecology.They are discharged mainly from industrial activities such as processing and incomplete combustion of wastes,and enter the atmosphere,soil,and aquatic environment.As one of the most dangerous typical organic pollutants,polycyclic aromatic hydrocarbons(PAHs)are composed of two or more fused ring in conjugate system,commonly found in trace forms in aquatic environments.Not only do they wreaking havoc on organisms but also as common food contaminant,which are highly toxic,semi-volatile and difficult in degradation that widely concerned in the world.Polycyclic aromatic hydrocarbons(PAHs)in surface water or soil surface can undergo photochemical degradation under solar irradiation.Dissolved organic matters(DOM)are the organic material left by the degradation of plant tissues and biological excreta in the process of biological and abiotic oxidation.The mixture with complex molecular structure,which are common in the water environment.They often have adsorption with the environmental organic pollutants or metal substances,which have a great influence on its biodegradability,solubility in the aquifer and storage.At present,Current research focuses on the adsorption of metal ions and organic pollutants by DOM,and the research results on the influence of the major photochemical degradation methods of PAHs in the environment are not clear enough.Therefore,in order to understand the trend of photochemical reaction of PAHs in water environment in detail,it is necessary to further explore the effect and mechanism of different sources of biological carbon end substances on the photodegradation of PAHs.The main research results are as follows:(1)After 180 min of illumination,results indicated that the photodegradation was the main degradation approach of PAHs,which accorded with the first-order reaction kinetics equation.The extent of degradation of anthracene and pyrene was 36% and 24%,respectively.After four DOM types were added,UMRN could promote the photolysis of anthracene;ESHA,LHA and SRFA all inhibited the photolysis of anthracene and the LHA inhibition was the strongest,followed by ESHA and SRFA.Except SRFA,the other three DOM inhibited pyrene photolysis to a similar extent.The apparent photolysis rate constants of anthracene in SRFA,LHA,UMRN and ESHA were 0.15,0.14,0.20 and 0.17,respectively,and pyrene was 0.09,0.09,0.09 and 0.14.(2)The inhibition mechanism of terrestrial DOM and water-source DOM on the photolysis of anthracene and pyrene was explored,and it was found that there were both mechanism of DOM quenching effect and light shielding effect on PAHs,among which the light shielding effect of DOM was the main reason to inhibit the photolysis of anthracene and pyrene.The binding capacity of the four DOM and anthracene was calculated by fluorescence quenching method.The binding capacity of the four DOM and anthracene was UMRN>LHA>SRFA>ESHA,in turn,and the binding capacities of the four DOM and anthracene were shown as SRFA>UMRN>ESHA>LHA.(3)The quenching effect of DOM on PAHs can be directly observed by synchronous fluorescence spectra and Excitation-Emission spectra.According to EEM spectral scanning,terrestrial DOM has more aromatic structure and larger molecular weight than water source DOM.From the point of view of the combination with anthracene,the terrestrial DOM protein was more sensitive.In the process of binding to pyrene,the water source DOM humic acid and tyrosin-like components are relatively easy to bind to DOM.For anthracene,protein-like components are more prone to photolysis,while from the point of view of the interaction between DOM and pyrene,the degradation rate of each fluorophore region is as easy as the protein-like> humic acid-like > metabolic by-product of the soluble microorganism(4)The binding of terrestrial DOM with anthracene mainly involves the contractive vibration of N-H and the contractive vibration of C-O of polysaccharide carboxylic acid.The binding of water source DOM with anthracene is related to the contractive vibration of N-H and the S-O contractive vibration of inorganic sulfate.The binding of four kinds of DOM with pyrene is mainly caused by the asymmetric stretching vibration of C-O-C bonds in aliphatic rings.At the same time,C-O functional groups are formed.