【作者】 孙国金；

【导师】 单国荣； 施耀； 张清宇；

【作者基本信息】 浙江大学 ， 化学工程， 2013， 博士

【摘要】 控制机动车排气污染是我国城市大气污染控制中最为迫切与重要的工作之一。机动车排气污染已经成为我国影响城市大气环境质量的主要因素,其中PM2.5、NOx是当前大气环境中的主要污染因子,研究机动车排气的PM2.5、NOx排放特征与污染物减排策略具有重大科学意义与应用背景。本论文以杭州市为主要案例,通过典型道路边人行呼吸带的PM2.5与NOx采样监测,并对采集的样品进行了理化分析和源解析研究；结合基于杭州市排气定期机动车检测/维修制度(I/M计划)的机动车状况研究和道路网特征调查分析,利用修正的IVE模型计算分析了机动车污染物排放清单；以LEAP2011模型为计量工具,预测了未来10年内(2011-2020年)浙江省机动车保有量的变化情况与PM2.5和NOx的排放量。根据以上研究结果,提出了浙江省机动车的PM2.5和NOx减排措施与策略。杭州市呼吸带PM2.5的理化性质研究表明,城市路边与环境空气PM2.5组分相比,具有无机组分含量低、有机组分高的特征。路边PM2.5中NO3-的绝对浓度、NO3-/总阴离子、NO3-/SO42均大于环境点,说明机动车直接排放的颗粒物及气态污染物转化形成的二次颗粒物已经是影响城市路边PM2.5浓度的主要因素。而路边两侧SO2转化率和NOx的转化率超过了0.1,表明有光化学反应发生。富集因子分析表明,机动车污染是道路两侧土壤和灰尘中重金属污染的主要来源。PM2.5中Pb仍维持着较高的富集水平,路边大气污染已经对人体健康有潜在的危害。对城市呼吸带NOx的理化性质研究表明,路边NO2浓度明显高于环境点,路边NO2日变化规律与车流量变化相似,机动车尾气排放是造成道路两侧NO2污染的主要来源,促使市区环境空气污染向煤烟.机动车尾气复合型转变。针对上述机动车排气污染情况,应对排放高的车辆进行筛选及控制。杭州市10多年的I/M数据分析表明,超过50%的机动车车龄在6年以内,25%的轻型客车车龄超过10年,90%的货车车龄在8年以内；NOx等污染物以及烟度值与车龄呈正相关,随着车龄的增加检测车辆的污染物排放越严重。车辆和路况对机动车的排放有重大影响。车辆类型调查表明,杭州市区各车型中乘用车的比例不断增加且比例最大,占到了74.1%,出租车比例基本不变,货车比例有所下降；路况调查则表明杭州市区道路平均行驶速度25.86km/h,高速路、快速路、主干道和民用支路分别为48.61km/h.27.1km/h、15.78km/h和16.76km/h,市区路网中民用支路(65.9%)和主干道路(26.1%)比例较大,快速路不足,主干道上红绿灯频繁,交通拥挤严重,加减速或怠速状态比例高,而匀速比例较低,交通拥堵导致机动车排放大量增加。利用修正的IVE模型计算了杭州市2010年机动车排放的NOX和PM2.5的清单。机动车NOX年排放4.43万吨,PM2.5年排放0.54万吨。NOX和PM2.5的最大贡献车型都是重型柴油车。国I标准前和国I标准车是NOX和PM2.5排放的主要来源,国Ⅲ标准车保有量巨大,但排放量最小,说明通过提高排放标准能够显著减少轻型车排放。机动车污染物排放强度的空间分布整体上呈现由城市中心向城市边缘扩展的递减趋势,中心城区各污染物排放量均占总排放量的70%以上。应用LEAP2011模型预测了浙江省2011～2020年间机动车保有量的变化和机动车污染物排放总量。模型分析显示,至2020年,浙江省城区机动车总保有量从2010年的538.1万辆增至1457.1万辆,年均增长率为10.47%；至2020年浙江省PM2.5和NOX排放分别为5.92万吨和54.45万吨,年均增长率分别为5.37%和8.24%,届时NOX减排、大气PM2.5污染防治的形势将更加严峻。减排措施与策略控制策略研究表明,大力发展公共交通、优化城市道路网、落实检查／维护(I/M)制度、加快老旧车辆更新淘汰、限制高污染车行驶,推行新排放标准,提升油品质量管理,是减少机动车PM2.5及NOX排放的有效措施。从长远来看,控制机动车数量、发展绿色交通、倡导绿色出行是必然选择。更多还原

【Abstract】 Regulating vehicle emission is one of the most urgent and critical missions in the air pollution control in China. Vehicle emission, including PM2.5and NOx, has been the major factor which affects the quality of atmospheric environment in the urban area of Chinese cities. Therefore, it is of great scientific and practical importance to investigate the characteristics of the vehicle emission including both PM2.5and NOx and make pollution reduction plans accordingly.Hangzhou was selected as a representative city in China for this study. The samples collected from the breathing belt beside typical roads were analyzed to examine PM2.5and NOx pollution. Both the physical and chemical characteristics and source decomposition analysis was performed on these samples. By investigating vehicle conditions based on the regular vehicle inspection/maintenance (I/M) program and characteristics of traffic network, the air pollutant emission inventory of vehicles was analyzed through the calculations with the modified IVE model. The number of vehicles and the emission of PM2.5and NOx in the following10years (from2011to2020) in Zhejiang province were predicted with the LEAP2011model. Based on these results, a reduction strategy and measures for the emission of PM2.5and NOx in Zhejiang province was proposed.The physical and chemical analysis of PM2.5on the breathing belt of Hangzhou showed that the PM2.5composition of roadside air is rich in organic constituents but lean in inorganic ones compared with that of ambient air. The absolute concentration of NO3-, the ratio of NO3-to the total anions, and the ratio of NO3-to SO42-for PM2.5in the roadside air are all larger than those in the ambient air, which suggest that the secondary particles, converted from direct vehicle emissions and pollutants in the air, were the leading factor which affected the PM2.5concentration in the roadside air. Both SO2and NOx conversion ratio in the roadside air are larger than0.1indicates the existence of photo-chemical reactions. The analysis on the enrichment factor shows that vehicle emission is the major source of heavy metal pollution observed in the soil and dust on roadsides. The relatively high enrichment level of Pb in PM2.5indicates that the roadside air pollution has posed a potential threaten to human health.The physical and chemical analysis of PM2.5on the breathing belt of Hangzhou showed that the concentration of NO2is1.15～1.59times higher in the roadsides than that in the ambient air. The variation of the concentration of NO2is consistent with the variation of traffic volume, which suggests that the vehicle emission is the major source of the NO2pollution in the roadside air and lead to soot-vehicle exhaust complex air pollution in downtown Hangzhou.In order to deal with the above mentioned pollution from vehicle emission, it is necessary to identify high emission vehicles and impose strict regulation. The analysis of data from I/M program during the past over10years, more than50%vehicles are less than6years old.25%of the light-weighted bus are more than10year old, while90%truck are less than8years old. Smoke degree and the emission of pollutants such as NOx are proportional to the age of a vehicle. The older the vehicle is, the more severe the emission of pollutants is.Vehicles and road conditions have strong influence on the emission of pollutants. The survey on types of vehicles shows that74.1%of vehicles were passenger cars, the number of which is still growing. The percentage of taxi among the vehicles is roughly unchanged while the percentage of truck shows a decline. The survey on traffic conditions shows that the average driving speed in the local area of Hangzhou is25.86km/h. The average driving speeds on freeways, highways, major roads, and civil branch roads are48.61km/h、27.1km/h、15.78km/h, and16.76km/h respectively. Due to the large proportion of major roads (65.9%) and civil branch roads (26.1%), the frequently switched traffic lights, and heavy traffic, many vehicles have to slow down, idle, and speed up frequently, which leads to significantly increase in the amount of vehicle emissions.The vehicle emission inventory of the year2010for NOx and PM2.5pollution in Hangzhou was calculated with revised IVE model. Results show that the NOx emission was44.3thousand tons while the PM2.5emission was5.4thousand tons. Heavy diesel vehicles were the largest contributor of NOx and PM2.5. From the perspective of vehicle emission standards, two types of vehicles (C I before and C I) were identified to be major sources of NOx and PM2.5. Although the number of C III vehicles was huge, the emission from these vehicles was smallest as they were regulated with high emission standards. Therefore, raising the emission standard is an effective way to reduce the emission of light-weighted vehicles. There was a decreasing trend for the vehicle emission intensity from the downtown area of Hangzhou to the suburban area. The emission of various pollutants in the downtown area is over70%of the total emission.The amount of vehicles and the total emission of pollutant from vehicles of Zhejiang province between2011and2020was predicted with LEAP2011model. The results from the analysis of the model shows that the number of vehicle in Zhejiang province will increase from5.381million to14.571million between2010and2020, which is equivalent to a10.47%annual growth rate. The emission of PM2.5and NOx will be59.2thousand and544.5thousand tons, which are equivalent to5.37%and8.24%annual growth rates, respectively. Therefore, the situation of emission control on NOx and PM2.5in2020will be much more severe.Studies on reduction measures and control strategies show that promoting public transportation, optimizing traffic network, applying I/M program, speeding up the replacement of old vehicles, restricting the use of high emission vehicles, enforcing high emission standard, and enhancing the management of oil quality are effective ways of reducing PM2.5and NOx emissions,In a long term perspective, controlling the number of vehicles, developing green transportation system, and encouraging green commute will be ultimate choices.更多还原