基于车流和大气污染物浓度同步增量的机动车平均排放因子估算方法

机动车尾气排放已成为城市大气污染的主要来源并受到了高度关注.机动车排放因子是反映机动车排放状况的最基本参数,但实测排放因子代价较高、代表范围有限,基于国外排放模式估算的排放因子又与我国的实际排放状况存在一定差距.本研究首先基于早高峰时段车流量和道路附近大气污染物浓度呈近线性增加、气象条件和背景污染物浓度相对稳定的特征,将时段内污染物浓度的增加主要归因为车流的增加,从而建立车流和污染物浓度增量之间的关系;然后采用无限线源高斯扩散模式,反推道路实际行驶机动车的平均排放因子.以北京市一条主干道为例,利用早高峰车流量、污染物浓度、气象观测数据,进行了实例研究,并将研究结果同COPERT4排放模型的预测结果进行了对比.本研究和COPERT4排放模型预测的8月一氧化碳平均排放因子分别为2.0 g·km-1和1.2 g·km-1,12月分别为5.5 g·km-1和5.2 g·km-1.结果表明,本方法估算的机动车排放因子在数值大小及季节变化上均与COPERT4排放模型较为接近.所提方法通过消除背景浓度的干扰,为实时获取车队实际排放因子提供了一种新思路.     

Number concentration and size distributions of submicron particles in Jinan urban area： Characteristics in summer and winter

The aerosol number concentration and size distribution were measured with the newly developed Wide-range Particle Spectrometer in summer and winter of 2006 at the urban site of Jinan City.Here reported the characteristics of fine particles of the different observation seasons.Relative high number concentrations for the particles in the diameter range of 10-500 nm were observed in both seasons.It was found that the dominant number distributed in particle diameter smaller than 100 nm and the percentage over the number concentration of all air particles is much higher than what has been measured in other urban sites over the world.The number mean diameter in summer was much smaller than in winter,strongly suggesting the different origin of ultrafine particles in different seasons.That is, particles in ultrafine mode mainly came from nucleation and new particle formation in summer while from traffic emission in winter. The diurnal variation also supported this point.Number concentration in the diameter range of 10-200 nm got their peak values at noontime,well correlated with the mixing ratio of SO_2 and the intensity of solar radiation in summer.While in winter,those in the same diameter range showed the main peaks during the traffic hours happened in the morning and evening.     

‘Enclosing country park land and the conservation of military heritage:’ an Ostromian interpretation of the fools’ paradise

British colonial military heritage structures in Hong Kong are in a state of ruin and government neglect. Urgent attention is required in the form of active management to avoid the loss of valuable heritage resources and the negative impact on the landscape and environment. This paper explores two possible alternatives – user participation and social entrepreneur participation – to achieve innovative solutions to rent dissipation of these structures situated in isolated areas within protected-area boundaries, with a focus on a specific case. Emphasis is placed on fostering public participation, involving the allocation of some property rights. Elinor Ostrom's diagnostic approach to common-pool resource problems is applied to both solutions to determine the conditions necessary to achieve the objectives. The discussions are informed by social entrepreneurship principles and a version of the Coase Theorem, the latter coinciding with Ostrom's view regarding the role of property rights in achieving sustainable outcomes.     

上海早晨边界层的稳定度特征及其对PM2.5峰值浓度的影响

PM_2.5的峰值浓度一般出现在早晨,这是早晨高排放和低边界层共同作用的结果.早晨的边界层结构对PM_2.5峰值浓度及演变具有重要影响,但准确反演早晨较低的边界层高度存在很大困难.基于此,本文以上海为例,采用8：00的L波段气象探空数据,利用高分辨率的垂直风温资料计算总体理查逊数（Rf）来判定早晨边界层的稳定度.研究发现,上海早晨边界层的稳定度具有明显的季节差异,其中,11月、12月和1月基本为稳定边界层结构（SBL）,5—8月为对流边界层结构（CBL）.通过分析风温廓线发现,上海冬季早晨SBL存在明显逆温,高度约为100~200 m,平均逆温强度为2.4℃/100 m;而夏季早晨的CBL可发展至400~500 m.早晨PM_2.5峰值浓度随Rf的升高明显上升,SBL条件下的PM_2.5峰值浓度较CBL条件下偏高约20 μg·m^-3.2013—2017年上海早晨边界层的稳定度在春季和冬季呈波动上升的趋势,其中,2016和2017年的上升幅度尤其明显.2016、2017年春季的SBL频数较2013—2015年同期分别偏多12.5%、17.0%,冬季分别偏多10.8%、9.0%,而2016、2017年春季的PM_2.5浓度却分别下降11.00%、23.00%,冬季分别下降27.94%和34.38%,表明近几年上海早晨的PM_2.5排放强度明显下降.     

Diurnal variation of number concentration and size distribution of ultrafine particles in the urban atmosphere of Beijing in winter

Number concentration and distribution of airborne particles in the size range 5.6 to 560 um diameter were measured in Beijing for a 15-d period in winter 2005.Daily average number concentrations of nucleation mode(5.6-20 nm),Aitken mode(20-100 nm), and accumulation mode(100-560 nm)particles,and total particles were 17500,32000,4000,and 53500 cm~(-3),respectively.Average particle size distribution was monomodal with a mode diameter of about 40 um at night and bimodal with mode diameters of about 10 and about 40 nm during the daytime.New particle formation events,which were connected to diurnal variation of nucleation mode particles,were observed in more than half of the observation days.The events often started around 10:00-11:00 Chinese Standard Time (CST)and ended up after 3-4 h.Concentrations of Aitken and accumulation mode particles increased from midnight and reached their maxima at about 10:00 CST,and then decreased and became the lowest in the afternoon.Analysis of diurnal cycles in traffic volume and meteorological parameters revealed that the accumulation of the particles in Aitken and accumulation modes in the morning was influenced by formation of an inversion and increase in vehicle emission,and dispersion of such particles in the afternoon was associated with more effective vertical mixing and higher wind speed.     

MM5-SMOKE-CMAQ as a modeling tool for 8-h ozone regulatory enforcement: application to the state of Arizona

The Penn State/NCAR Mesoscale Meteorological Model 5 (MM5), Sparse Matrix Operator Kernal Emissions (SMOKE), and Community Multiscale Air Quality (CMAQ) modeling systems were employed to simulate ozone concentration distribution within the State of Arizona, in particular, Phoenix air basin, as supporting information to designate nonattainment areas of the U.S. Environmental Protection Agency's new 8-h ozone standard. In general, based on statistical comparisons between predictions and available (sparsely distributed) observations, the modeling system performed reasonably well for the Phoenix basin, thus proving it to be a useful tool for both regulatory as well as research applications. Detailed inspection, however, revealed a serious problem with respect to the details of the ozone distribution in that for some days the transition from downslope flow to upslope flow in the Phoenix basin was delayed in the model, causing the ozone distribution to show an unrealistic high-ozone bias toward the west valley. Implementation of a modified subgrid parameterization improved the time of transition, and hence the prediction of ozone and its precursor distributions. This study points to possible inadequacies of commonly used subgrid parameterizations in dealing with rapidly changing flow conditions such as morning (and evening) transitions.     

上海市大气羰基化合物水平研究

建立乙腈-水-四氢呋喃三元梯度洗脱方法,利用HPLC-UV分离定量22种羰基化合物,并成功地分离了丙酮和丙烯醛.选取了2个采样点(工业区和商业区)对上海市大气中的羰基化合物进行了研究.结果表明,甲醛、乙醛、丙酮和2-丁酮(C1-C4羰基化合物)是上海市大气浓度较高的化合物,它们分别占羰基化合物总量的78.95%(工业区)和77.63%(商业区).在工业区,甲醛、乙醛、丙酮和2-丁酮的平均浓度分别为10.36、15.32、9.95和4.56μg/m3;在商业区,它们的平均浓度分别为10.00、10.04、7.80和2.81μg/m3.工业区的C1-C4羰基化合物平均水平要高于商业区.羰基化合物总量亦是工业区(53.64μg/m3)高于商业区(41.96μg/m3).羰基化合物的昼夜变化在工业区和商业区也比较一致,均是早高峰和晚上这2个时段的浓度很高,而其它时段较低.