Study Of Environmental Persistent Free Radicals' Lab-preparation And Their Biotoxicity

Environmental persistent free radicals?EPFRs?can formed during incomplete combustion of particles with certain organic substances adsorbed on the surface.Study shows that the formation of EPFRs could be affected by many factors such as precursors,carrier particles,and pyrolysis conditions,metal oxides,etc.However,due to the late recognition of EPFRs,the current study data of these EPFRs is still very limited,and also lacks its toxicity of aquatic organisms.This study focuses on the generation of EPFRs during the pyrolysis of particulate matter and their toxic effects on aquatic organisms during the pyrolysis of particulate matter.First,EPFRs were simulated the preparation in our lab with catechol-silica?CT-SiO₂?as model substrate and pyrolysis under oxygen-limited environment.The effects of metal ions?Fe,Cu,Ni,Zn?and their metal oxides,pyrolysis temperature and CT/SiO₂ mass ratio on the formation of EPFRs were investigated.In addition,the generation of·OH in the suspension and the toxicity of synthesized EPFRs were tested.Results of EPR analysis showed that the concentration of metal oxides in matrix could increase the formation of EPFRs,while metal ions could not.The pyrolysis temperature and the mass ratio of CT/SiO₂ were important factors and significantly affected the concentration and types of EPFRs formed in the pyrolysis system,and the highest concentration of EPFRs reached 5.04×10¹⁵ spins·g^-1 with temperature of 400?and CT/SiO₂ mass ratio of 0.032.The combination with the particles might increase its stability so half-lives of EPFRs could reach between 18-80 days at ambient air.Toxicity tests revealed that EPFRs could significantly inhibit the luminescence of P.phosphoreum and also cause zebrafish embryo death and malformation of juvenile fish.It is speculated that the toxicity mechanism may be related to the generation of reactive oxygen species?ROS?in the suspension.Second,CT-contaminated soils were used as a case study to analyze the generation of EPFRs under limited oxygen conditions.The effects of pyrolysis temperature and CT/S-4 mass ratio on the formation of EPFRs were investigated.The results showed that EPFRs mainly exist in clay/mineral/humin part of soil?S-4?,accounting for about 70%of EPFRs content in soil.The results of EPR analysis indicated that the pyrolysis temperature and the mass ratio of CT/S-4 were also important factors and significantly affected the concentration and types of EPFRs formed in the pyrolysis system,and the highest concentration of EPFRs reached8.01×10¹⁷ spins·g^-1 with temperature of 300?and CT/S-4 mass ratio of 0.004.Ultraviolet irradiation experiments were used to further study the detailed information on the formation of EPFRs in CT-contaminated soils.The results showed that the concentration of EPFRs in soil gradually increased with the increasing UV irradiation time and eventually stabilized,with the concomitant production of·OH.Results indicated that EPFRs in soil had a strong risk and may be the reason of acute toxicity to P.phosphoreum.In summary,our results provided the detailed information for the formation of EPFRs and their biotoxicity in environmental processes,which will further necessary for the potential environmental risk of EPFRs.