Toxicity Assessment Of Fluoranthene,Benzo(a)Anthracene And Their Mixed Pollutant In Soil At The Molecular And Animal Levels

Currently,the environmental risk of polycyclic aromatic hydrocarbons(PAHs)in soil has gradually attracted attention due to the incomplete combustion of oil and fossil fuels,as well as the regular and accidental leakage of petroleum hydrocarbon products and raw materials during storage,transportation,and use,and the daily emissions from agriculture and urban residents,which have caused a sharp increase in the content of PAHs in soil.Fluoranthene(Fla)and benzo(a)anthracene(BaA),two important PAHs,have high levels and detection rates in soils of many countries and regions,including China,and are on the U.S.Environmental Protection Agency's(USEPA)Priority Control List for PAHs.Fla and BaA can enrich and fix in the surface or subsurface layers of soil,and then migrate,metabolize,accumulate and expand in organisms through the food chain,eventually becoming potentially hazardous substances that endanger soil ecosystems and even human health.Therefore,considering the widespread presence of Fla and BaA in the soil environment and their significant bio-toxic effects,it is crucial to accurately assess their ecological risks in soilIn this study,we assessed and compared the effects of Fla,BaA and their mixed pollutant on the structure and function of typical enzymes in the soil at the molecular and animal levels,and further investigated the oxidative stress effects induced by different Fla-BaA mixed pollutant exposure conditions in the organism of the earthworm.This thesis contains five sections:Part ?:Firstly.the types,sources and migration pathways of PAHs in the environment were introduced.Secondly,the structure,physicochemical properties and the current status of toxicological studies of Fla and BaA were highlighted.Meanwhile,this part introduced the technical methods,research contents and research significance involved in this study.Part ?:?-Amylase,a typical hydrolytic enzyme in soil,was selected as the object of study,and the effects of Fla and BaA on the structure and function of ?-Amylase were explored and compared by multispectral means,molecular simulation techniques and enzyme activity experiments.The results of this part of the study showed that Fla and BaA had a significant impact on the structure and function of ?-Amylase.The Fla exposure led to a gradual tightening of the backbone structure of ?-Amylase and could immediately lead to the formation of Fla-Amylase complexes.In contrast,BaA was able to disrupt the solvent shell on the surface of ?-Amylase,causing ?-Amylase to tend to disperse.In addition,the interaction of Fla,BaA and ?-Amylase changed the microenvironment around the ?-Amylase chromophore,in which BaA was able to quench the fluorescence of ?-Amylase by static quenching.The molecular docking technique showed that the binding sites of Fla/BaA to ?-Amylase were located near the active site.Part ?:This part explored the effects of Fla-BaA mixed pollutant on the structure and function of ?-Amylase,and deduced the combined mode of Fla and BaA acting together on ?-Amylase.The results of this part of the study showed that the effects of high doses of Fla-BaA mixed pollutant on the structure of ?-Amylase were stronger than those of the system exposed alone,and the effects of BaA on the skeleton structure of ?-Amylase were more significant in the mixed pollutant system.On the other hand,the high concentration of the Fla-BaA mixed pollutant tended to form complexes with?-Amylase more,but the size of the complexes was still smaller than that of ?-Amylase itself.The results of the activity test revealed that the Fla-BaA mixed pollutant inhibited?-Amylase activity more strongly than the system exposed alone.In addition,Fla and BaA acted on ?-Amylase in a near additive combined mode of action.Part ?:This part explored the oxidative stress effects induced by Fla-BaA mixed pollutant on the earthworm at the animal level.The results of this part revealed the two-phase effects of Fla-BaA mixed pollutant on GSH-px and SOD in earthworm and the important function played by POD in mitigating oxidative damage.In addition,the Fla-BaA mixed pollutant showed significant time-dependent effects on T-AOC and MDA levels in earthworm,suggesting that long-term or high-dose exposure conditions can cause oxidative damage in earthworm.Part ?:This part summarized the main conclusions and innovations of this study,and at the same time,it indicated the shortcomings of this study and made an outlook for the next phase of research.In summary,this study combined the molecular-level studies with the animal-level studies to systematically assess the toxicity of Fla,BaA and their mixed pollutant in soil,thus providing a systematic and scientific accumulation of data for toxicity studies of Fla and BaA,and emphasizing the importance of paying attention to the potential risk of Fla and BaA in soil.