Study On Biotoxicity Of PM_2.5 Based On Algal Fluorescence Characteristics

With the development of urbanization and industrialization,air pollution has become increasingly serious.Among the many atmospheric pollutants,PM2.5(particles with aerodynamic diameter?2.5?m)is a threat to human health due to its complex source and chemical composition,small diameter,large surface area,and can enter the human body through skin contact and respiratory system.Therefore,it is concerned by the scholars all over the world.The pollution character of PM2.5 was analyzed by the onlion observation method.The PM2.5 samples were collected offline according to the air quality index(AQI).Chlorella pyrenoidosa was used as the experimental algae species,and the biotoxicity characteristics of PM2.5 water-soluble species were identified by the changes of pH,chlorophyll a,rapid fluorescence induction curve,fluorescence parameters and cell morphology.The results are as follows:(1)During the observation period,the most serious time of PM2.5 pollution in Beijing was mainly concentrated in March.NO3-was most correlated with NH4+ among water-soluble species,followed by SO42-and NH4+.NH4NO3 and(NH4)2SO4 are the main binding modes of water-soluble ammonium salt components in PM2.5 of Beijing.NH4NO3 is the main combination of nitrates,and(NH4)2SO4 is the main combination of sulfates.(2)There were good correlations between the three monitoring indexes of algae cell concentration,chlorophyll a content and absorbance OD.The growth curve of Chlorella pyrenoidosa was plotted using absorbance OD.(3)Chlorella pyrenoidosa can be used to evaluate the biotoxic characteristics of PM2.5.A mild or higher pollution level reduces the chlorophyll fluorescence parameter Fv/Fm,and DIo/RC Reaction center unit energy consumption increases as the exposure time becomes higher,to reduce the energy for photosynthesis.(4)When the PM2.5 solution is slightly polluted and above,the algal cells are prone to plasmo separation,the cell membrane is detached from the cell wall,and the regular chloroplast layer structure is destroyed,and the starch granules are blurred.As the pollution level increases,the damage to the cell structure becomes more and more obvious.(5)The water-soluble species that threaten the growth of chlorella are mainly nitrates led by NH4NO3 and sulfates led by(NH4)2SO4.The research results have guiding significance for further exploring the comprehensive toxicity of different chemical components in PM2.5 and its impact on human health.