Research On Concentration Simulation And Health Impact Of Vehicular Fine Particles In Beijing

The composition of fine particles(PM_2.5)in motor vehicle exhaust is complex and highly toxic.Especially,primary PM_2.5 from on-road vehicles would easily accumulate in urban traffic dense areas and form high-concentration hot spots,which would cause greater harm to human body.It is of great significance to study the distribution and identify the hot spots of vehicular primary PM_2.5 concentration and its corresponding population exposure dose and health effects.Based on hourly,link-based vehicle emission inventory and meteorological data,we employed a line-source mode in AERMOD dispersion model to match the inventory to the actual road geometry features and simulate high-resolution PM_2.5concentration distribution.Furthermore,within the sixth ring region of Beijing,the health effects and monetary values,population exposure dose of vehicular primary PM_2.5 under various scenarios are comprehensively assessed referring to localized exposure,health effect and monetization parameters.Daily mean concentrations of vehicular primary PM_2.5 are 0.7-2.9μg·m^-3 in the four seasons under typical weekday emission level,while the concentration during the APEC summit decreases dramatically by 50%.The temporal variation and spatial distribution of simulated concentration are both affected by the dual function of emissions and meteorological conditions.Concentration peaks are often formed at the peak emission hours with unfavorable diffusion conditions.The distribution of medium and high concentration(>3μg·m^-3)also corresponds to mid-high intensity emission and extends toward the downwind of prevailing winds in the season.Under different simulated concentration scenarios,Daily mean exposure concentrations of vehicular primary PM_2.5 are 1.0-2.0μg·m^-3,and daily mean population exposure dose of vehicular primary PM_2.5 in a unit grid is about 6.3-10.9 mg·d^-1.The distribution of exposure is similar to population distribution rather than simulated concentration distributiong.The APEC scenario will lower 58 death and34530 outpatient cases respectively compared with that before APEC summit due to the reduction of vehicular primary PM_2.5.The avoidable death and outpatient cases ouccupy 42%of that before APEC summit.And the economic values of the health benefits would be 110 and 19 billion yuan respectivelyHigh concentration(6.0-71.0μg·m^-3)hot spots were mainly located at national and provincial highways,ring roads and easily congested main roads.Hotspots of exposure dose and health effects are not only near areas with high concentration or high concentration reduction,but are als o concentrated in high population density（7200-43200 people/km²）areas such as Guangximen,Sanyuanqiao,Sanlitun,and Fuchengmen,etc.The exposure dose and health effects of the hotspots accounted about 60%and 70%respectively for the total of the region within the sixth ring road.Identifying hotspots and implementing targeted emission reduction measures would maximize the health benefits of the policy.