Dicarboxylic acid concentration trends and sampling artifacts

Dicarboxylic acids associated with airborne particulate matter were measured during a summer period in Philadelphia that included multiple air pollution episodes. Samples were collected for two 10 h periods each day using a high-volume sampler with two quartz fiber filters in series, and analyzed by gas chromatography mass spectrometry (GCMS) with diazomethane derivatization. Among the dicarboxylic acids investigated, phthalic acid and adipic acid exhibited the greatest diurnal variations and the strongest linear relationship with maximum daily ozone concentration. Dicarboxylic acids and ozone concentration exhibited a poor linear relationship with organic to elemental carbon ratio. All species investigated were affected by significant sampling artifact errors at low concentrations, but sampling errors were negligible at high concentrations observed during ozone episodes.     

Estimation of atmospheric trace metal emissions in Vilnius City, Lithuania, using vertical concentration gradient and road tunnel measurement data

A new approach for the estimation of trace metal emissions in Vilnius city was implemented, using vertical concentration profiles in the urban boundary layer and road tunnel measurement data. Heavy metal concentrations were examined in fine and coarse particle fractions using a virtual impactor (cut-off size diameter 2.5 μm). Negative vertical concentration gradients were obtained for all metals (Ba, Pb, V, Sb, Zn) and both fractions. It was estimated that the vertical concentration gradient was formed due to emissions from an area of about 12 km². Road tunnel measurements indicated that trace metal concentrations on fine particles were lower than those on coarse particles, which suggested that re-emitted road dust was highly enriched in trace metal due to historic emissions within the tunnel. Emission rates of different pollutants in the road tunnel were calculated using pollutant concentration differences at the tunnel entrance and exit and traffic flow data. Heavy metal emission rates from the area of Vilnius city were estimated using the vertical gradient of heavy metal concentrations and the coefficient of turbulent mixing, as derived from meteorological measurement data. The emission values calculated by the two different methods coincided reasonably well, which indicated that the main source of airborne trace metals in Vilnius city is traffic. The potential of the vertical concentration gradient method for the direct estimation of urban heavy metal emissions was demonstrated.     

北京市冬季气象要素对气溶胶浓度日变化的影响

对2004年1月1—15日北京气溶胶浓度与相对湿度、气压、风速、风向等气象要素的平均日变化进行分析,结果表明:北京冬季ρ(PM₁₀₎日变化明显,受气象要素的日变化影响. ρ(PM₁₀₎与相对湿度和气压呈正相关性;风速对ρ(PM₁₀)的日变化影响明显,09:00—18:00风速和ρ(PM₁₀₎变化趋势一致,呈正相关性,其他时间则呈负相关性; 风向对粗、细粒子的数浓度影响不同,细粒子数浓度在偏东风时大,西、西南风时小,而粗粒子则相反;粗、细粒子的数浓度日变化受气象要素的影响程度不同,相对于粗粒子,细粒子数浓度更易受气象要素日变化的影响.      

郑州地区大气气溶胶光学特性的地基遥感研究

根据自动跟踪扫描光度计观测资料,利用Bouguer-Lamber定律反演郑州地区2007年2~9月气溶胶光学厚度和波长指数,分析郑州地区该时段气溶胶光学特性的季节变化和日变化情况.结果表明,郑州地区2007年2~9月1020nm气溶胶光学厚度为0.49±0.09;870nm气溶胶光学厚度为0.60±0.13;670nm气溶胶光学厚度为0.76±0.20;440nm气溶胶光学厚度为1.08±0.34.季节变化以夏季最高,秋冬次之,春季最低.波长指数春季为0.37~0.69,夏季为1.18~1.26.春季有50%以上的天气,扬尘粒子为主控粒子,而夏季城市-工业气溶胶是主控粒子之一.日变化规律与近地面污染物浓度变化一致,8:30和17:00左右出现峰值,11:30出现谷值,由于气温上升,湍流剧烈,12:30左右气溶胶光学厚度有1个小高峰,但仍处于全天的低值区.     

CHEMIFOG_V – A Model to Simulate Radiation Fogs and their Interaction with Vegetation and Chemistry

Radiation fog is an important modifier of atmosphericcompounds in the planetary boundary layer. In vegetated areas effects are especially pronounced due to the enlarged surface area. Besides affectingthe lower boundary of atmospheric models fog acts as amulti-phase reaction chamber leading to acid deposition. Here we present the 1-dimensional radiation fog modelCHEMIFOG_V to simulate regional radiation fogevents. The key feature of the fog model is thedetailed microphysics, where the aerosol/dropletspectrum is describedwith a joint 2-dimensional distribution, but also thedynamics, thermodynamics, and radiative transfer are calculated. Toinvestigate the interaction between fog and the biosphere amulti-layer vegetation module, including a soil module as well as a drydeposition module were coupled. Vegetation influences thedynamics, thermodynamics, and the radiation field of the lowestatmospheric layers. With CHEMIFOG_V, numerical case studieson dry and moist deposition processes on vegetation surfaces wereperformed. Hereby multi-phase chemistry and the processing of aerosolswere considered. The results show that the chemical composition of thedeposited fog droplets is mainly determined by the aerosol composition. Dry deposition fluxes are dependent on the incoming radiation and the leaves' surface conditions with respect to water coverage.Due to chemical aerosol processing and deposition, the aerosol spectrumis significantly modified in the planetary boundary layer.     

珠江三角洲地区大气气溶胶中有机污染物背景研究

选择肇庆市鼎湖山自然保护区为珠江三角洲大气气溶胶有机污染评价的区域性环境背景．研究结果表明,珠江三角洲地区大气气溶胶中优控多环芳烃背景值萘、苊、二氢苊、芴、菲、蒽、荧蒽、芘、苯并（a）蒽、、苯并（b）荧蒽、苯并（k）荧蒽、苯并（a）芘、茚并（1,2,3-cd）芘、二苯并（a,h）蒽、苯并（ghi）分别为n.d.、n.d.、tr.、0.14、tr.、0．39、0.53、0.19、1.05、1.82、1.41、0.02、2.29、0.53和2．44ng/m³,总量为10.80ng/m³,其来源主要为高等植物排放.     

华北地区气溶胶数浓度和尺度分布的航测研究 ——以石家庄为例

2009年秋季利用河北省人工影响天气办公室机载气溶胶粒子探头(PCASP-100X)和前向散射滴谱探头(FSSP-100-ER)在石家庄市上空进行了多次气溶胶观测.选取2009年9~10月间的7架次雾天、1架次小雨天及1架次密卷云天观测资料,重点研究雾天气溶胶粒子数浓度和直径的垂直、水平分布特征及粒子谱分布,并与密卷云天和小雨天的探测资料进行对比分析.结果表明:石家庄地区气溶胶粒子数浓度较高,近地面最大值达11910个/cm3.气溶胶粒子数浓度主要受天气条件影响,逆温层是影响粒子垂直输送的主要因素,在逆温层下粒子累积形成粒子数浓度的高值区,逆温层以上气溶胶粒子数浓度迅速减少,雾天和密卷云天粒子数浓度随高度多呈负指数分布;雾天多伴有逆温层和较大空气湿度,有利于气溶胶粒子累积,数浓度一般可达104个/cm3以上,容易形成低能见度污染天气;气溶胶粒子数浓度在无降水日有累积效应,降雨对气溶胶粒子有明显清除作用;粒子数浓度和粒子直径在水平方向上呈不均匀分布,随着高度增加粒子数浓度和直径的水平绝对偏差减小,相对偏差往往增大;不同天气下尺度谱型类似,多呈单峰分布,在0.11μm左右处出现峰值,但在雾天、密卷云天、小雨天气下的气溶胶粒子峰值依次变小,并且随高度增加,尺度谱峰值数密度值降低,谱变窄.     

沙尘暴事件中大气颗粒物化学组分的浓度变化和硫酸盐的形成

应用电感耦合等离子体原子发射光谱、质谱和离子色谱分析了2002年3月28日-4月8日在山东长岛县采集的共11对粗、细大气颗粒物样品的化学组成,探讨4月6-8日沙尘暴事件中大气颗粒物化学组分的变化和硫酸盐的形成.沙尘暴事件应区分前锋和后续部分,前锋与大气中各种污染物相互作用,具有硫富集的特征.后续部分较好地保持了长距离传输风沙尘本身的特征.硫酸盐的形成机理可能是多相氧化而不是简单的酸碱中和.硫酸铵是首先生成的含硫物种,这是细颗粒主导的形成过程.硫酸铵逐渐转化为其他硫酸盐,硫的成分也逐渐向粗颗粒转移.在沙尘暴事件中含硫污染物不但有一个从气相向颗粒物转变的过程,也有一个从细颗粒向粗颗粒转化的过程.      

大气气溶胶中有机成分研究进展

有机物是大气气溶胶的重要组成部分,尤其是在细颗粒中,可占其干重的10%～70%。由于有机气溶胶的健康及气候效应,有机物的组成、源分布、颗粒行为等的研究越来越受到人们的重视。其中,有机物成分的鉴别和定量已成为近年来的研究热点。在分析中,就目前有机气溶胶的采样、有机成分提取、分离及定性、定量分析方法进行了综述,并比较了各种方法的优缺点。     

Spatial distribution of aerosol pollution based on MODIS data over Beijing, China

With the help of regression analysis,the relationships were detected between aerosol's contribution to apparent reflectance(ACR) derived from Moderate Resolution Imaging Spectroradiometer(MODIS)on board Terra and hourly PM_(10)mass concentration measured at 30 ground-based locations in Beijing for the August of 2003 and 2004.It was shown that there was a good correlation between the ACR and PM_(10)(linear correlation coefficient,R=0.56).On the basis of this relationship,spatial distribution and possible sources of PM_(10)derived from MODIS were analyzed and two frequently heavily-polluted regions were found,namely downtown of the city and the district near Xishan Mountain.These two regions coincidently are also urban heat island centers.The foundings of this paper will be greatly useful for environmental monitoring and urban planning for Beijing,especially for the 2008 Olympic game to be held in Beijing.