Study On The Mechanism Of Fine Particulate Matter (Pm2.5) In Chengdu City And Human Health Hazards Of Pm2.5

Taking Chengdu city as the background of the study, this thesis has collected the basic information of the emission of pollution sources in Chengdu(point source, non-point source and line source). as well as calculated emissions of any pollutant from various pollution sources, and also has established database of particles pollution sources of Chengdu. Meso-scale meteorological model WRF has been adopted to simulate the flow field of the study area and to analyze the structural features of atmospheric boundary layer.Utilizing CMAQ (The third generation of air quality model of the US), we have carried out the simulating calculation and an analysis of the constituents of fine particles PM2.5from atmospheric environment, and arrived at its sources and compositions.By the investigation and data collection, we have made a quantitative analysis of damage to human health caused by PM2.5, and set up an exposure-reaction model, proposed prevention program and countermeasures to control pm2.5, provided a basis for government’s policy in order to promote harmonious development of urban economy and environment.During the research of Chengdu, I have reached the following conclusions:(1) According to the ground flow field distribution, we can see that the transport law of pollutant among regional scale is that the flow is arc linear from northwest to southwest, the pollutant removed from northeast and northwest of Chengdu to the southwest.(2) According to the source and constituents of pm2.5in Chengdu, the proportion that primary particles contributed to pm2.5concentration in Chengdu is58.30%, among which, the proportion of industrial sources, pollution sources of traffic, and dust is21.69%、19.42%、17.19%respectively. The proportion of secondary particles is37.85%, among which. the proportion of sulfate\nitrates\secondary organic aerosols is21.55%、11.20%、5.10%respectively.(3) There is a changing trend of the daily average sediment yields to be firstly increases and then decreases. The result is related to many factors. Major factors are respiration flux、 activity level and microenvironment. According to the annual deposition of five years from2007to2011. we can arrive at that the average annual deposition inside people in Chengdu is around174mg a year per person.Under different microenvironment, the contribution to bodies" amount of soakage and deposition of pm2.5differs greatly. As for the average deposition inside human bodies in microenvironment. the outdoor public parking lot and places near the road ate the biggest contributors, reached around4.76μg/min. next is the other outdoor places or inside the underground transport, with an average level of1.72μg/min. The microenvironment that contributes the least is the house and indoor care center, with an average level of0.46μg/min. From the above analysis, we can find that people who are exposed to the environment of worse air quality including outdoor public parking lot and places near the road, have a larger quantity of fine particles pm2.5inside people.The deposition of pm2.5in people is clearly different under different active state.The deposition is the largest in people who work on cleansing and machinery job about5.5μg/min. When people sleep, the number will be at least0.251μg/min.(4) When exposed to air polluted by PM2.5, the comprehensive health risks to people under the age of4increased significantly as8.050%; followed by people between5to14years, its comprehensive health risk reach to5.462%; comprehensive health risks of exposure to people between15to64years is insignificant, which is about3.422%; the people between65to100years who is affected minimally, and comprehensive health risk is2.921%.(5) The dose-response relations between the amount of deposition of pm2.5and prevalence rate is consistent with Hill model. The confidence of standard dosing schedule is95%, the confidence lower limit will be84.5134mg per year,and the compute limit is75.7073mg per year. It shows that once the deposit of pm2.5in humans reach75.7073mg per year, the prevalence rate of respiratory disease will significantly increase a little,and once it reach97.0132mg per year, the prevalence rate of respiratory disease will significantly increase.