轨迹烟流模式计算方法

集合了高斯烟流模式和烟团模式的优点,提出一个新的模型———轨迹烟流模式,既保留了烟流模式计算简单,计算结果连续的特点,又可以根据当时风场,确定不同的烟流轨迹,模拟烟团的弯曲、折回和重叠运动,分段进行计算,提高了计算的准确性扩大了模式应用范围。     

Determination of the optimum MM5 configuration for long term CMAQ simulations of aerosol bound pollutants in Europe

Realistic meteorological fields are a prerequisite for the determination of pollutant concentrations and depositions by means of a chemistry transport model. Different configurations of the 5th generation NCAR/Penn State University mesoscale meteorological model MM5 were tested to determine the optimum set up for long term hindcasts that cover several months up to years. Four dimensional data assimilation (FDDA) significantly enhances the spatio temporal representation of temperature, humidity and wind. Best agreement with radiosonde observations could be achieved when temperature, humidity and wind were grid nudged every 6 h. The quality of the resulting meteorological fields showed no significant systematic temporal or spatial variation over Europe in a model run of the year 2000. It was found that the hydrological cycle was not correctly reproduced by the model when no nudging was applied. The relevant model run showed too high relative humidity and too high rainfall when compared to observations. This led to considerably lower aerosol concentrations close to ground and a shift in the deposition patterns of particle bound pollutants like the carcinogenic benzo(a)pyrene (B(a)P). Guest Editor: Dr. S. T. Rao.     

黄渤海上空气溶胶类型判别及其成因分析

气溶胶是大气环境的重要组成部分,其对天气和气候变化有重要影响,对人类健康也有危害.对气溶胶类型的区分有利于判别气溶胶的来源,这对控制气溶胶污染源、改善区域环境质量有重要的推动作用.本文基于黄渤海区域6个观测点的实测数据和卫星遥感数据,采用聚类分析方法对黄渤海上空的气溶胶进行分类,并采用拉格朗日轨迹追踪法判定气溶胶的来源.研究发现,黄渤海上空的气溶胶类型以清洁大陆型和生物燃烧以及城市/工业型为主,陆源输入是黄渤海上空气溶胶的重要来源.清洁大陆型的气溶胶在黄海中部的贡献率相比于其余海域偏低,这也间接表明近岸的气溶胶更易受到来自陆地的影响,离岸区域受陆地的影响相对较小.     

利用CALPUFF对安徽和河南秸秆焚烧的模拟与研究

秸秆焚烧会产生大量的颗粒物(PM)、氮氧化物、有机碳、苯以及多环芳烃等污染物,不仅影响空气质量,危害人体健康,而且大大降低能见度,对交通运输构成威胁. 针对安徽和河南2009年6月严重的秸秆焚烧现象,对CALPUFF模拟系统和FEPS模型进行重新编译与整合,对空气动力学直径小于10 μm的颗粒物(PM₁₀)进行扩散模拟,得到逐时ρ(PM₁₀₎的烟羽扩散,并对模拟结果进行分析. 结果表明,秸秆焚烧过程中焚烧点附近的ρ(PM₁₀₎较大,研究区域内部分区域的日均ρ(PM₁₀₎大于我国二级标准(150 μg/m3)甚至三级标准(350 μg/m3). 如果考虑二次粒子,其影响程度会更加严重.      

Pathways for the oxidation of sarin in urban atmospheres

The nerve agent sarin has recently been deployed by terrorists in a major city. The molecule is volatile and made its way to many victims by passing as vapor through a highly reactive medium. Here we estimate rates and pathways for the removal of gas phase sarin from a generalized urban atmosphere. Only information from the open scientific literature is used. By structure reactivity comparisons with the organophosphorus pesticides, hydroxyl radical hydrogen abstraction may occur in as little as one hour. Decomposition of side chains after hydroxyl attack leads to organic oxygenates which preserve the phosphonofluoridate and so toxicity. The aqueous aerosol surface is contacted in minutes and offers access to a range of dissolved nucleophiles. Substitution displaces the fluoride leaving group, giving safe phosphoric acid analogs. Because of uncertainties in the electron distribution and in aqueous decay mechanisms, the time constants must be viewed as lower limits.     

Chemical signals of epiphytic lichens in southwestern North America; natural versus man-made sources for airborne particulates

Ambient airborne particulate matter (PM) in southwestern North America consists of naturally derived desert dust, plus anthropogenic inputs from several sources. Epiphytic lichens (Usnea sp.) in this region are a useful biomonitor for the airborne PM because they derive nutrients and moisture largely from incorporated atmospheric aerosols, and not by absorption from the host tree limb from which they are suspended. Using a broad-based sampling strategy from southern Chihuahua, Mexico, to northern New Mexico, USA, we show that select elemental abundance ratios and lead isotopes from epiphytic lichens are useful for distinguishing between sources of airborne PM, and for gauging anthropogenic inputs into desert ecosystems. Abundance patterns of the trace elements La, Nd, and Sm in the lichens suggest origination from continental crust, but rare earth elements display a pronounced enrichment relative to the major element Fe by a factor of about 5. This enrichment appears related to geologic weathering, aeolian transport, and grain-size biases toward trace-element-rich mineral grains in the arid setting. Using the metal Pb as an indicator of human inputs, epiphytic lichens typically show Pb enrichments by a factor of about 25–60 over typical upper crustal values. Regional-scale differences in Pb isotope ratios of these lichens relate to different pollutant sources in southwestern North America.     

New insights into the formation of ammonium nitrate from a physical and chemical level perspective

● Factor analysis of ammonium nitrate formation based on thermodynamic theory. ● Aerosol liquid water content has important role on the ammonium nitrate formation. ● Contribution of coal combustion and vehicle exhaust is significant in haze periods. High levels of fine particulate matter (PM_2.5) is linked to poor air quality and premature deaths, so haze pollution deserves the attention of the world. As abundant inorganic components in PM_2.5, ammonium nitrate (NH₄NO₃) formation includes two processes, the diffusion process (molecule of ammonia and nitric acid move from gas phase to liquid phase) and the ionization process (subsequent dissociation to form ions). In this study, we discuss the impact of meteorological factors, emission sources, and gaseous precursors on NH₄NO₃ formation based on thermodynamic theory, and identify the dominant factors during clean periods and haze periods. Results show that aerosol liquid water content has a more significant effect on ammonium nitrate formation regardless of the severity of pollution. The dust source is dominant emission source in clean periods; while a combination of coal combustion and vehicle exhaust sources is more important in haze periods. And the control of ammonia emission is more effective in reducing the formation of ammonium nitrate. The findings of this work inform the design of effective strategies to control particulate matter pollution.     

Aerosol chemistry and the effect of aerosol water content on visibility impairment and radiative forcing in Guangzhou during the 2006 Pearl River Delta campaign

Optical and chemical aerosol measurements were obtained from 2 to 31 July 2006 at an urban site in the metropolitan area of Guangzhou (China) as part of the Program of Regional Integrated Experiment of Air Quality over Pearl River Delta (PRIDE-PRD2006) to investigate aerosol chemistry and the effect of aerosol water content on visibility impairment and radiative forcing. During the PRIDE-PRD2006 campaign, the average contributions of ammonium sulfate, organic mass by carbon (OMC), elemental carbon (EC), and sea salt (SS) to total PM_2.5 mass were measured to be 36.5%, 5.7%, 27.1%, 7.8%, and 3.7%, respectively. Compared with the clean marine period, (NH₄)₂SO₄, NH₄NO₃, and OMC were all greatly enhanced (by up to 430%) during local haze periods via the accumulation of a secondary aerosol component. The OMC dominance increased when high levels of biomass burning influenced the measurement site while (NH₄)₂SO₄ and OMC did when both biomass burning and industrial emissions influenced it. The effect of aerosol water content on the total light-extinction coefficient was estimated to be 34.2%, of which 25.8% was due to aerosol water in (NH₄)₂SO₄, 5.1% that in NH₄NO₃, and 3.3% that in SS. The average mass-scattering efficiency (MSE) of PM₁₀ particles was determined to be 2.2 ± 0.6 and 4.6 ± 1.7 m² g⁻¹ under dry (RH < 40%) and ambient conditions, respectively. The average single-scattering albedo (SSA) was 0.80 ± 0.08 and 0.90 ± 0.04 under dry and ambient conditions, respectively. Not only are the extinction and scattering coefficients greatly enhanced by aerosol water content, but MSE and SSA are also highly sensitive. It can be concluded that sulfate and carbonaceous aerosol, as well as aerosol water content, play important roles in the processes that determine visibility impairment and radiative forcing in the ambient atmosphere of the Guangzhou urban area.     

渗滤液中有机物在不同氧化还原带中的降解机理与效率研究

通过土柱模拟实验研究了垃圾渗滤液中的有机污染物在地下环境中的降解机理和效率.结果表明,铁还原带对有机污染物的降解起重要作用,平均降解效率达86.24％,其次是氧还原带、硝酸盐还原带、硫酸盐还原带和产甲烷带,分别平均达到75.93％、79.81％、74.02％和65.09％;厌氧还原环境可能对苯并噻唑、安替吡啉、茚等物质的降解起重要作用;萘、环己酮、部分环烷烃等不易被微生物降解;不同污染物在不同氧化还原带中的最大降解效率也不同,如1,1,1-三氯乙烷和邻二甲苯在硫酸盐还原带中的降解效率最高,分别为80％和71.43％;三氯乙烯和MTBE则在硝酸盐还原带中的降解效率最高,分别为81.25％和92.58％;而苯在硫酸盐还原带和铁还原带中均被全部降解.     

液氨泄漏事故伤害范围模拟及人员疏散研究

基于高斯烟羽模型,应用风险评估软件对液氨储罐在不同泄漏模式下的液氨伤害范围进行模拟,得出各模式下液氨伤害范围的变化规律,并分析了风速对液氨扩散的影响作用。制定了液氨储罐特定泄漏模拟场景下的人员疏散路径,为液氨泄漏事故下的人员应急救援以及疏散等提供参考。