Effect Of Dissolved Organic Matter On Anthracene And Pyrene Degradation In Ice

With the convening of the Third Plenary Session of the 18th CPC Central Committee,China officially entered the 2.0 era.Today China is calculated by industrial output value,and China has become the world's largest industrial country.Urban automobile exhaust,large fossil fuel combustion and improper disposal of solid waste have caused a large amount of organic wastes?HOCs?to enter environmental media.PAHs are typical organic wastes with“triad effect”and genotoxicity,and Its water repellency can accumulate in environmental media and can have a profound impact on humans.Dissolved organic matter?DOM?is a complex organic matter formed by a series of decay mineralization processes by animal and plant residues.It has a non-negligible effect on the regulation of various ecosystems.Studies have shown that DOM and HOCs can produce complex binding and adsorption behaviors,can reduce the concentration of HOCs,and play an important role in the distribution,migration,transformation,photodegradation and biodegradation of biological wastes such as PAHs and biological toxicity.At present,most of the research focuses on the photodegradation of HOCs in aqueous media,ignoring the study of photodegradation under ice conditions.Compared with environmental media such as atmospheric atmosphere and water body,the physical migration process,conventional chemical reaction and microbial action of pollutants in ice are relatively weak,but photochemical action has played a significant role.Studying the photodegradation of PAHs by different sources of DOM in ice not only helps to understand the photochemical properties of DOM in ice,but also understands the biogeochemistry of carbon in cold environment.This paper adopts DOM from water source and land source,water source DOM:Suwannee River Fulvic Acid Standard II?SRFA?,Upper Mississippi River NOM?UMRN?;land source DOM:Elliott Soil Humic Acid Standard IV?ESHA?,Leonardite Humic Acid Standard?LHA?and typical polycyclic aromatic hydrocarbons anthracene and pyrene were studied.The 125 W self-ballasted high-pressure mercury lamp was used as the simulated light source for indoor simulated photolysis experiments to investigate the dissolved organic matter on the degradation of anthracene and pyrene under ice.The results of High performance liquid chromatography,UV-spectroscopy and fluorescence spectroscopy and simultaneous fluorescence analysis show that the effects of dissolved organic matter on the photolysis of anthracene and pyrene in the ice are as follows:Direct photodegradation can occur in anthracene and pyrene in the ice,and when the DOM is mixed with anthracene and pyrene,the DOM will have a light shielding effect on anthracene and pyrene.The obvious difference between water source DOM and terrestrial DOM is the ultraviolet absorption capacity,especially in the range of 230-500 nm.The UV absorption capacity of terrestrial DOM is stronger than that of water source DOM.On the whole,the degree of influence and effect of natural DOM from different sources on pollutants in ice phase is not the same.The influence of water source DOM on pollutants in ice phase is less than that of terrestrial DOM in ice phase.In the ice phase,the photolysis inhibition mechanism of DOM on pollutants from different sources is mainly based on light shielding effect.The effect of·OH on the photolysis promoting mechanism of anthracene and pyrene on different sources of DOM in ice phase is higher than ¹O₂.The molecular structure of DOM from different sources is different,which directly leads to the significant difference in the promotion effect of the same reactive oxygen species on the same pollutant in different DOM.The same active oxygen species promoted the enthalpy during the photolysis of the ice phase pyrene more strongly than the stimulating effect of anthracene.From the perspective of the contribution of two reactive oxygen species,the chromophore content of terrestrial DOM is significantly higher than that of water source DOM.Through investigation,it is found that the mechanism of promoting the degradation of pollutants by DOM in the ice still depends mainly on the contribution of reactive oxygen species.In the analysis of the degree of quenching in the inhibition mechanism,it was found from the fluorescence spectrum that the fluorescence intensity of anthracene and pyrene decreased when DOM was added,but the degree of reduction was different.The DOM of four different sources produced quenching effect on both anthracene and pyrene,and the quenching degree of anthracene the excited state of the same DOM was significantly higher than that of pyrene the excited state.When the degree of quenching of pollutants by DOM in the photolysis process is greater,the apparent photolysis constant is smaller and the degree of inhibition is stronger.From the point of view of the binding constant,for anthracene,the effect of·OH on the binding of DOM to contaminants in the ice is not significant.For pyrene,since ¹O₂weakens the aromaticity of DOM and indirectly weakens the polarity of the molecule,it can reduce the binding ability of DOM to anthracene and pyrene,so that reduce the effect of quenching.In this study,the effect of ¹O₂ on water source DOM is slightly stronger than that of terrestrial DOM.·OH can play a good role in promoting the photolysis of pyrene in the ice and the promotion is stronger than the quenching effect of DOM.The static quenching of the two water sources DOM is more obvious than the dynamic quenching in the process of photolysis with anthracene and pyrene.For the other two terrestrial DOMs,dynamic quenching is more prominent.According to the overall analysis,for the pollutants such as polycyclic aromatic hydrocarbons,the quenching effect of DOM on the photolysis in the ice should be the dynamic and static combined quenching mechanism.There was a significant correlation between SUVA and a₂₅₄54 and E_ET/E_BZZ during the UV index analysis,where there was a extremely significant correlation for pyrene between E_ET/E_BZZ and a₂₅₄.It can be seen that the photolysis process of DOM on anthracene and pyrene in ice have a good revelance,the degree of substitution and the possibility of natural substitution are very high with the content of aromatic compounds containing C=C and C=O,and the degree of aromaticity and humification of DOM.Under the condition of coexistence with DOM,the apparent solution rate constant of the pyrene in the ice phase was significantly positively correlated with the SUVA value of DOM?P<0.01?.In the process of the influence of DOM from different sources on pyrene photolysis in the glacial phase,the influence of DOM on pyrene photolysis is the same as that of the carbon content,aroma degree and humidification degree of DOM.