| At present,the contradiction between the increasing number of motor vehicles and the lagging infrastructure of road network in Xi’an has become increasingly prominent,which has exacerbated the congestion problem in the city.Compared with unobstructed traffic,fleet emissions are higher when congested,thereby increasing the level of traffic pollution.However,traffic pollution can cause adverse consequences to the health of residents and directly lead to serious social and economic losses.Therefore,it is necessary to conduct an in-depth analysis of traffic pollution in urban congestion,and quantify its health and economic losses,so as to provide a theoretical basis for urban traffic pollution prevention and control policies.In this paper,the concentrations of particulate matter(PM)and black carbon(BC),traffic flow conditions and meteorological conditions in the congested main road and expressway of Xi’an were continuously measured in winter working days.The spatio-temporal variations and influencing factors of PM and BC in congested roads were discussed,and the PM2.5concentration levels in expressways were predicted by using a generalized additive model.Secondly,based on the measured road PM and BC concentration data,the respiratory deposition dose model was used to estimate the hourly exposure doses of PM and BC for pedestrians of different ages.Finally,the number of premature deaths caused by traffic PM10 and PM2.5pollution in Yanta District of Xi’an City was estimated by health assessment model,and the corresponding health economic losses were evaluated by statistical life value method.The main conclusions of this study are as follows:(1)PM and BC pollution and congestion on main roads were more serious than those on express roads.The daily average concentrations of PM10,PM2.5,PM1,and BC on the main roads were 156μg/m~3,72μg/m~3,45μg/m~3,and 4089ng/m~3 respectively,while the express roads corresponded to 95μg/m~3,46μg/m~3,29μg/m~3 and 3509ng/m~3respectively.The PM and BC levels of main roads during the day were 17～64%higher on average than those of express roads.At the same time,the average vehicle speed and occupancy rate of main roads during the day were 11%and 43%lower than those of expressways,respectively.(2)The PM2.5 level of expressway had a linear negative correlation with vehicle speed,and a non-linear positive correlation with relative humidity.When the relative humidity was in the range of 30 to 55%,with the increase of relative humidity and the decrease of vehicle speed,the concentration of PM2.5 on expressway gradually increased.When the speed range was20～35km/h and the relative humidity was about 55%,the PM2.5 concentration of expressway was the highest,about 56μg/m~3.The PM10,PM2.5,PM1,and BC of the main road and expressway were all negatively correlated with temperature,and positively correlated with relative humidity.Among them,PM1 had the strongest correlation with weather conditions.The Pearson correlation coefficient between PM1 and relative humidity was 0.81,and the correlation coefficient with temperature was-0.59.(3)The hourly deposition doses of PM10,PM2.5,PM1,and BC of pedestrians on the main road were 65%,57%,74%and 17%higher than those on the expressway,respectively.Among the three types of pedestrians,children,adults,and the elderly,the elderly had the highest PM and BC hourly deposited doses.The respiratory deposition doses of PM10,PM2.5,PM1 and BC for the elderly in the main road activities were 235.7μg/h,25.7μg/h,9.8μg/h and 6624 ng/h,respectively,corresponding to 143μg/h,16.3μg/h,5.6μg/h and 5684 ng/h on the expressway.(4)According to the estimated result,the number of premature deaths caused by PM10and PM2.5 pollution in Yanta District of Xi’an City traffic in the winter working day of 2019were 4.5 and 2,respectively,and the corresponding economic losses were 9.5 million yuan and4.3 million yuan. |
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