| Since 2010,the number of container throughputs of Shanghai Port has continued to increase,and ranked first in the world for 11 consecutive years,which has created huge economic benefits to Shanghai and even nationwide.However,it has also inevitably brought serious environmental pollution problems.In particular,tens of thousands of container trucks travel between ports and hinterland every day,which generates a large number of traffic emissions.According to the Ministry of Ecology and Environment of the People’s Republic of China,diesel trucks accounted for only 10%of the total number of motor vehicles in Shanghai in 2019,but their particulate emissions accounted for 92%of the city’s total vehicle particulate emissions.It can be seen that the particulate matter emitted by container trucks has a serious impact on the quality of atmospheric environment.Under these circumstances,focusing on container trucks in Shanghai,this study investigated the spatiotemporal distributions of particulate matter from container truck roads based on the field monitoring.Besides,the dispersion of particulate matter from container trucks was revealed through numerical simulations.Finally,some management strategies for container trucks were proposed.The main work is summarized as follows:(1)The fixed-point monitoring was used to reveal the characteristics of particulate matter in container truck hotspots in Shanghai.Firstly,the particulate matter emitted by container trucks in the port area on hazy days and non-hazy days were characterized.Then the characteristics of particulate matter in the port area were compared with those in the urban area.Finally,the principal component analysis was performed to reveal the influence of traffic factors and meteorological factors on particle concentration.The main findings are as follows.The particle concentration on hazy days is found 117.07%to 701.64%higher than that on non-hazy days.On the hazy day,the particle concentration during the morning is 2.89%to 36.81%higher than that during the afternoon,while on the non-hazy day,the result turns out the opposite and shows that the concentration in the afternoon is 64.67%to 144.49%higher than that in the morning.These indicate that air temperature,relative humidity and traffic volume play a role in promoting or inhibiting particle concentration,which can be affected by different weather changes.Besides,the comparison results show that the particulate number concentration in the port area is 16.13%to 119.33%higher than that in the urban area.Particularly concentrations of PM1,PM2 and PM10 in the port areas are respectively 43.68%,61.95%and 103.23%higher than those in the urban areas.The correlation coefficient in the morning is 0.32 to 0.66 between container trucks and particulate matter concentration,while in the afternoon it is less than 0.11.This indicates that the number of container trucks has an appreciable contribution to the particulate variation in the morning hours,while the contribution of meteorological factors is greater than that of traffic emission in the afternoon.In addition,the decrease of temperature and relative humidity,and the increase of wind speeds are conducive to the decrease of particulate matter concentration in the port area.(2)The mobile monitoring was used to reveal the spatiotemporal distributions of particulate matter in Shanghai container truck road network.Firstly,the collected data in the container truck road,residential road,riverside road and elevated road were used to characterize the spatiotemporal distribution of particle concentration in summer and winter.Secondly,the relationship among particle concentration with different particle sizes was analyzed.Finally,the effect of traffic volume and meteorological factors on particle concentration was investigated.The main results are summarized as follows.Particle concentration on the container truck road and elevated road are 30%higher than those on the residential and riverside roads.Traffic conditions and roadside environment jointly determine the spatial variation of particle concentration,The particle concentrations on all of the four roads in winter are more than twice higher than those observed in summer.The seasonal differences of the particle concentration could be largely attributed to the significant differences among air temperature,atmospheric stability,and mixing height in winter and summer.The relationship among particles on the container road and elevated road(R2=0.69 and 0.74)is weaker than that on the residential road and riverside road(R2=0.84 and 0.87).When the proportion of container trucks increases by more than 20%,the particle concentration increases by more than 134%.Although the proportion of container trucks in the total traffic volume is small,the particle concentration emitted by container trucks contributes significantly to the total particle concentration.(3)The dispersion of container truck emission was studied by numerical simulation.Firstly,the parameters of the dispersion model were determined based on the data of traffic volume,meteorology and emission factors,etc.Secondly,the particle concentration dispersion characteristics were simulated by the dispersion model,and then the measured values and the simulated values were compared.Finally,the dispersion characteristics of particle concentration under different wind speeds,traffic volumes and vehicle speeds were simulated.The results reflect that the particle concentrations show negative exponential gradient patterns as the distance from the traffic emission hotspots increases.The correlation coefficient between the simulated value and the measured value is 0.98 on the container truck road.There is a positive correlation between the particle concentration and traffic volume,and there is a negative exponential relationship between the concentration,vehicle speed and wind speed.On the container truck road,when the traffic volume drops by two times,the particle concentration within 100m decreases by 236.84%.When the vehicle speed drops from 60 km/h to 12 km/h,the particle concentration increases by 42.51%at 0m.When the wind speed increases from 0.5m/s to 4m/s,the particle concentration drops by 76.44%at 0m.(4)Some management strategies for reducing container truck emission in Shanghai were proposed based on the driving track of container trucks.Firstly,the traffic distribution of container trucks were displayed in the road network.Secondly,the spatial distribution characteristics of container truck emissions in the road network were obtained through the traffic emission model.Finally,some management strategies for the emission reduction of container trucks were proposed and evaluated by the normalization method and coordinate system method.The results show that the Pudong section of the Shanghai Ring Expressway,which is directly adjacent to the Waigaoqiao Port area,has the largest emissions,where the daily peak emission of PM10 reaches 19.86t.Under the management strategy of single emission reduction,the management strategy of reducing the proportion of highway transportation has the most obvious effect,and the reduction ratios of PM2.5 and PM10 are 55.67%and 54.61%,respectively.The comprehensive management strategy has the best effect,which is composed of traffic restriction,weight restriction,reducing the proportion of highway transportation,improving emission standards and developing underground logistics.The reduction ratio of particle concentration is above 92%,and the emission reduction coefficient reaches 0.18. |
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