Pollution Characteristics And Health Risk Of Perchlorate In Atmospheric Particulates

With the rapid development of industrialization and urbanization,air pollution has become more and more serious,and the public has paid more and more attention to air quality.Air pollution has become an important factor that threatens human health and sustainable urban development.As a rapidly developing city,Changsha is facing a series of air pollution problems during the process of urban construction and renovation.In view of the current air pollution problems in Changsha City,this study has carried out the following research work:First,in this study,PM_2.5 and PM_2.5-10 in autumn and winter at the South Campus of Hunan University of Changsha City were sampled using the TH-150 Series intelligent flow sampler.The gravimetric method was used to calculate the concentration of particulate matter and the ion chromatography was used to determine the concentrations of perchlorate.Then we analyzed and discussed the concentrations of PM_2.5 and PM_2.5-10 and the level of perchlorate in them.The results showed that the concentration of PM_2.5 during the sampling period ranged from 44.656?g/m³-125.472?g/m³ and the average concentration was 91.563?g/m³.The concentration range of PM₁₀ was 73.939?g/m³-229.025?g/m³ and the average concentration was153.136?g/m³.In general,the concentration of particulate matter in winter is higher than that in autumn.The perchlorate concentration in PM_2.5 ranged from 3.09 to 5.86ng/m³ and the average concentration was 4.82 ng/m³;the perchlorate concentration in PM_2.5-10 ranged from 2.18 to 4.98 ng/m³ and the average concentration was 3.66 ng/m³.The perchlorate concentration in PM_2.5 is generally higher than the perchlorate concentration in PM_2.5-10.The perchlorate in PM_2.5 accounts for a large proportion in PM₁₀,indicating that perchlorate is predominantly present in fine particles such as PM_2.5 in particles smaller than 10?m in diameter.Secondly,an eight-stage non-viable cascade impactor was used to collect size-segregated airborne particulate matter?APM?in the four seasons of Hunan University's southern campus.The concentration and size distribution of size-segregated APM were analyzed,and the perchlorate concentration in each size-segregated APM was further studied.The concentrations of size-segregated APM ranged from 3.907 to 133.795?g/m³,and the annual average concentration was 287.504?g/m³.The order of the total concentration of particulate matter is:winter>autumn>spring>summer,and the different meteorological conditions in different seasons are an important factor in seasonal variation of particulate matter concentrations.The size-segregated APM show a consistent bimodal distribution in the four seasons.They are mainly distributed on fine particles with a particle size range of 1.1-2.1?m and coarse particles of>9?m,and are easily deposited on the bronchi of the respiratory system.And the particle size of 1.1-2.1?m particles in the PM_2.5 of the largest proportion,particle size of 1.1-2.1?m and 5.8-9.0?m particles in PM₁₀ accounted for the largest proportion.The perchlorate concentration in the fractional particles ranged from 0.79 to 5.00 ng/m³ and the average concentration was 2.17 ng/m³.Perchlorate mainly accumulates in the particle size range of 1.1-2.1?m particles,indicating that perchlorate is mainly accumulated on the fine particles.Finally,this study uses the United States Environmental Protection Agency's?USEPA?health risk assessment model to calculate daily intake of different populations?infants,toddlers,children,adolescents,middle-aged,and elderly?through ingestion,inhalation,and dermal absorption.And on this basis,the Hazard Quotient?HQ?of different populations was calculated,and the health risks caused by perchlorate in size-segregated APM were evaluated.The results showed that the daily intake of perchlorate through three exposure pathways in the four seasons were in the following order:ingestion>dermal absorption>inhalation,and ingestion was significantly greater than that of dermal absorption and inhalation.Ingestion is the primary exposure pathway of daily intake.The order of the daily intake of perchlorate in size-segregated APM is:ultrafine particles>fine particles>coarse particles,indicating that the smaller the particle size,the greater the dose exposure of the population.The order of the health risk of perchlorate in total particulate matter is:ingestion>dermal absorbtion>inhalation.The HQ of ingestion of perchlorate in infants,toddlers and children is greater than 1,indicating that there is a certain non-carcinogenic risk for perchlorate in infants,toddlers and children with ingestion of total particulates.