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Relationships Between Polycyclic Aromatic Hydrocarbons In Snow Cover And Atmospheric Pollutants In Harbin

Posted on:2024-07-20Degree:MasterType:Thesis
Country:ChinaCandidate:X YaoFull Text:PDF
GTID:2531306917465854Subject:Physical geography
Abstract/Summary:PDF Full Text Request
Polycyclic aromatic hydrocarbons(PAHs)are a class of persistent organic pollutants widely present in the atmosphere,and their pollution distribution characteristics are controlled by the release source,transport diffusion and removal process.PAHs released during high temperature combustion are easily adsorbed on atmospheric particles and act together with other atmospheric pollutants,thus increasing the pollution level of the atmosphere.As snow has a large specific surface area,high porosity slow settling speed and other characteristics,so that pollutants in the wet deposition process through the snow removal effect accumulated in the snow,which is a good indicator of regional air pollution.Therefore,PAHs in snow can indicate its pollution distribution,and is often used to reveal the impact of human activities on the atmosphere and to identify potential pollution source areas.In this paper,we collected snow samples in Harbin City at the end of 2020,combined with the previous day-by-day air pollutant monitoring data(AQI、PM2.5、PM10、NO2、SO2、CO),to clarify the types of air pollution,pollution characteristics and the distribution characteristics and sources of PAHs in snow cover in Harbin City,to quantitatively analyze the relationship between air pollutants and PAHs in snow cover,to reveal their significance to air pollution,and to identify the potential source areas of winter air pollutants in Harbin City.The results of the study showed that:(1)From November 1,2020 to January 1,2021,the air quality in Harbin was mainly good,and there were three moderately polluted days,and the AQI is decreasing to different degrees due to the type and duration of snowfall,indicating that the snow removal effect is beneficial to improve air quality.The results of the characteristic radar map show that PM2.5 is the main pollutant and is a partial secondary pollution type;ρ(PM2.5)/ρ(PM10)ratio shows an increasing trend to further reveal that it is secondary aerosol pollution,andρ(PM2.5)shows a decreasing trend during the snowfall period,indicating that the snowfall has an obvious effect on the removal of fine particulate matter.The decreasing trend ofρ(NO2)/ρ(SO2)ratio during the study period indicates the enhanced contribution of coal combustion,and the decreasing trend ofρ(CO)/ρ(SO2)ratio indicates the gradual contribution of external pollution source emissions.(2)The concentrations ofΣ16PAHs in snow ranged from 1705 to 7243 ng·L-1,with an average value of 3015 ng·L-1,and were dominated by 2-4 rings PAHs.The spatial distribution ofΣ16PAHs content varied significantly,with higher concentrations located on roads in industrial areas or major urban traffic routes,which were more influenced by oncoming traffic.The sampling sites were classified according to functional areas,and it was found that the content ofΣ16PAHs at each sampling site increased in the order of green areas,residential areas,industrial areas and traffic areas.The source analysis of PAHs in snow was performed by the characteristic ratio method and factor analysis,and the results showed that the PAHs pollution in snow during the study period was mainly from coal and biomass combustion and vehicle exhaust emission sources.(3)Quantitative analysis of snow PAHs and atmospheric pollutants found that PM2.5and AQI correlated best,indicating that the air pollution during the study period was fine particulate matter pollution dominated by PM2.5,followed by PM2.5 and SO2,CO were significantly positively correlated indicating that the pollution mainly came from SO2,CO and particulate matter released from coal combustion sources transformed into secondary aerosol pollution under non-homogeneous reactions The 4-6 rings PAHs andΣ16PAHs,SO2,PM2.5,and PM10 are all significantly and positively correlated,indicating that combustion source PAHs,fossil fuel combustion release pollutants and atmospheric particulate matter have the same pollution source and transport behavior,and are transformed into secondary aerosols through non-homogeneous reactions,while low temperature and high humidity meteorological conditions in winter are favorable to the non-homogeneous chemical processes.(4)Based on the better correlation and common environmental behavior of PAHs components and atmospheric particulate matter,a backward trajectory model was applied to explore the transport paths and potential source areas of atmospheric pollutants in Harbin during the study period.The backward air mass clustering trajectory is significantly influenced by the height of the airflow,and the polluting airflow mainly comes from Xilingol League,Chifeng,Tongliao in Inner Mongolia,Liaoning and Jilin.The WPSCF and WCWT results show that both PM2.5 and PM10 show an increase in potential source area with height,and PM2.5 was the dominant pollutant in Harbin during the study period,and was derived from both fossil fuel combustion from industrial production activities in Liaoning,Jilin,and eastern Inner Mongolia,as well as from the continued accumulation of local domestic coal combustion and vehicle exhaust.The WPSCF and WCWT values of PM10 are small,indicating that the pollution to Harbin is small or non-polluting.
Keywords/Search Tags:polycyclic aromatic hydrocarbons, particulate pollutants, snow cover, historical characteristic radar map, backward trajectory model
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