Aerosol structure and vertical distribution in a multi-source dust region

The vertical distribution of aerosols was directly observed under various atmospheric conditions in the free troposphere using surface micro-pulse lidar (MPL4) at the Zhangye Station (39.08°N, 100.27°E) in western China in the spring of 2008. The study shows that the aerosol distribution over Zhangye can be vertically classified into upper, middle and lower layers with altitudes of 4.5 to 9 km, 2.5 to 4.5 km, and less than 2.5 km, respectively. The aerosol in the upper layer originated from the external sources at higher altitude regions, from far desert regions upwind of Zhangye or transported from higher atmospheric layers by free convection, and the altitude of this aerosol layer decreased with time; the aerosols in the middle and lower layers originated from both external and local sources. The aerosol extinction coefficients in the upper and lower layers decreased with altitude, whereas the coefficient in the middle layer changed only slightly, which suggests that aerosol mixing occurs in the middle layer. The distribution of aerosols with altitude has three features: a single peak that forms under stable atmospheric conditions, an exponential decrease with altitude that occurs under unstable atmospheric conditions, and slight change in the mixed layer. Due to the impact of the top of the atmospheric boundary layer, the diurnal variation in the aerosol extinction coefficient has a single peak, which is higher in the afternoon and lower in the morning.     

石家庄春季大气气溶胶数浓度和谱的观测特征

利用美国MSP公司生产的宽范围粒径谱仪(WPS)于2010年5月在石家庄市气象局进行了近地面大气气溶胶数浓度的观测,并结合该市同期的气象资料,分析了该次观测所得的大气气溶胶粒子数浓度和谱的特征及其成因.结果表明,本次观测到的气溶胶以超细粒子(粒径0.1μm)数浓度峰值出现时间为7:00和23:00.     

青岛市不同空气质量下可培养生物气溶胶分布特征及影响因素

利用Andersen空气微生物采样器采集青岛市不同空气质量下的可培养生物气溶胶,分析了其浓度和粒径分布特征,并利用Spearman’s相关性分析了可培养生物气溶胶浓度和空气质量指数中的颗粒物质量浓度〔ρ(PM₁₀)、ρ(PM_2.5)〕、气体污染物质量浓度〔ρ(O₃)、ρ(SO₂)、ρ(NO₂)〕和气象参数(温度、相对湿度、风速)之间的关系.结果表明:可培养真菌和细菌气溶胶浓度范围分别为133～1 113和13～212 CFU/m3.真菌气溶胶浓度与ρ(SO₂)、ρ(PM₁₀)、ρ(PM_2.5)均呈正相关,而与相对湿度呈显著负相关(P<0.05).细菌气溶胶浓度与ρ(NO₂)、ρ(SO₂)呈负相关,而与ρ(O₃)、温度呈正相关.风速对可培养生物气溶胶浓度的影响较小.以AQI(空气质量指数)中ρ(PM₁₀)为依据,将研究时间段空气质量划分为4个空气污染等级.在不同污染等级下,真菌气溶胶均呈对数正态分布,粒径主要分布于2.1～4.7 μm.低污染时细菌气溶胶呈偏态分布(粒径>4.7 μm),高污染时粒径分布发生改变.初步推断,随着空气污染等级的升高,可培养生物(真菌+细菌)气溶胶总浓度增加,但单位颗粒物上的浓度变化较稳定.ρ(PM₁₀)是影响可培养生物气溶胶浓度及粒径分布的主要因素.      

华北山区大气气溶胶浓度及其尺度谱分布的研究

1980年3月,我们在北京北部山区,用光学粒子计数器观测了“干净”地区近地层大气气溶胶浓度与尺度谱分布。发现“有霾”大气气溶胶的浓度及其尺度谱分布的变化特征具有特殊性。计算表明,三参数谱模式的拟合效果较好。     

Analysis of aerosol ammonium nitrate: Departures from equilibrium during SCAQS

The size distribution of the inorganic components of atmospheric aerosols measured during the 1987 Southern California Air Quality Study (SCAQS) are used to investigate the hypothesis that transport limits equilibration of gas- and aerosol-phase ammonium nitrate and influences their size distribution. Estimates of the equilibration time constants at four sites in southern California show a wide range of values; at small values equilibrium is expected whereas at large values departures from equilibrium are expected. An equilibrium indicator is proposed based on the size distributions of aerosol ammonium and nitrate that shows when particles of different size are in mutual equilibrium with respect to ammonium nitrate. Values of the indicator range from unity, demonstrating equilibrium, to less than 0.5, demonstrating that different size particles are not in mutual equilibrium. Comparison of the time constant values to the equilibrium indicator values show a significant correlation, so it is concluded that different size aerosol particles are often not in mutual equilibrium due to transport limitations, supporting the hypothesis. It is concluded that both thermodynamics and mass transport must be considered to predict accurately the size distribution of the volatile inorganics in atmospheric aerosol.     

Properties of atmospheric aerosols inverted from optical remote sensing

A new approach is proposed for optical remote sensing of atmospheric aerosols. A multiwavelength radiometer was used to measure direct solar radiation and sky radiation on the solar almucantar. The scattering phase function, the atmospheric optical depth, and their variation with wavelength were inverted simultaneously. A ‘reserve’ method was used to obtain the size distribution and refractive index of atmospheric aerosols. The results indicated that in Beijing city, the minimum total optical depth was 0.33 measured in September and October, and the maximum was 0.462 measured in March. The average value of the imaginary part of refractive index was 0.034 (0.532 μm) measured in winter (heating periods), and was only 0.016 (0.532 μm) measured in nonheating periods. A parallel observation was made to check the remote method, in which the aerosol size distribution was measured with a cascade sampler and the absorption coefficient of aerosols was obtained with the integrating plate method. The agreement of the results showed that the approach proposed was useful.     

华北地区霾期间对流层中低层气溶胶垂直分布

基于美国宇航局(NASA)的CALIPSO星载激光雷达监测数据,通过分析总后向散射系数、体积退偏比和色比,对华北地区2007年1月1日至2008年12月31日期间出现灰霾时对流层中低层气溶胶光学和微物理特性的垂直分布进行了研究.结果表明:灰霾期间对于4 km以下的对流层中低层大气总体来说,非球形气溶胶出现频率略高于球形气溶胶,小粒径气溶胶出现频率高于大粒径气溶胶.在4 km以下的大气中,气溶胶出现频率在1 ～2 km高度范围内最高,在2～3 km高度范围内最低;球形气溶胶在2～3 km高度范围内出现频率最高,非球形气溶胶出现频率在1 ～2 km高度范围内最高;大粒径气溶胶在l～2 km高度范围内出现频率最高,小粒径气溶胶在0～1 km高度范围内出现频率最高.     

天津城区大气气溶胶复折射指数的反演及消光贡献分析

气溶胶的复折射指数是直接影响其散射特性和吸收特性的基本物理量之一.为深入研究城市大气气溶胶的复折射指数特征,引入一种具有高时间分辨率优点的反演方法来反演气溶胶复折射指数.依据辐射传输理论,将天津大气边界层观测站观测到的高精度散射系数、吸收系数和数浓度谱分布数据利用查表法代入Mie理论气溶胶粒子群消光计算公式,对大气气溶胶复折射指数进行反演.结果表明:①天津城区2011年4月观测地点0.55 μm波长处的气溶胶复折射指数实部平均值为1.64,虚部平均值为0.015.②气溶胶复折射指数实部和虚部均有明显日变化规律,实部和虚部均与相对湿度呈正相关,与风速呈负相关.③利用反演得到的复折射指数对不同粒径大气气溶胶的消光特性进行计算发现,对散射特性而言,>0.25~1.00 μm粒子对散射系数的贡献率达86%;对吸收特性而言,>0.25~2.50 μm粒子对吸收系数的贡献率为53%,>2.50~32.00 μm粒子对吸收系数的贡献率为47%.研究显示,>0.25~1.00和>1.00~32.00 μm的粒子对吸收系数的贡献率均较高,但对散射系数而言,>0.25~1.00 μm的粒子贡献率较高,因此综合考虑气溶胶散射系数、吸收系数和消光系数,控制>0.25~1.00 μm的气溶胶粒子数浓度可有效改善大气能见度.      

江浙沪春节燃放烟花爆竹对垂直大气的影响

基于美国宇航局(NASA)的CALIPSO星载激光雷达L1卫星监测数据,通过分析532 nm总后向散射系数、体积退偏比和色比,对江浙沪地区2009—2014年春节期间大气气溶胶光学与微物理特性进行研究,揭示了江浙沪地区春节期间大气气溶胶散射强度、颗粒规则性与颗粒大小的垂直分布特征.结果表明,燃放烟花爆竹产生的颗粒物主要聚集于对流层中低空,使低层大气散射能力增强、颗粒物尺度增大,使对流层中层大气颗粒物不规则性增强;气溶胶散射能力随高度增大单调减弱,不规则气溶胶在6~8 km高度内占比最大,颗粒随高度增大单调减小;对比各年情况发现,散射能力逐年增强.     

Atmospheric concentrations and size distributions of aircraft-sampled Cd,Cu, Pb and Zn over the southern bight of the North Sea

In an effort to assess the atmospheric input of heavy metals to the Southern Bight of the North Sea, aircraft-based aerosol samplings in the lower troposphere were performed between September 1988 and October 1989. Total atmospheric particulate and size-differentiated concentrations of Cd, Cu, Pb and Zn were determined as a function of altitude, wind direction, air-mass history and season. The obtained data are compared with results of ship-based measurements carried out previously and with literature values of Cu, Pb and Zn, for the marine troposphere of the southern North Sea. The results point out the high variability of the concentrations with the meterological conditions, as well as with time and location. The experimentally found particle size distribution are bimodal with a significant difference in fractions of small and large particles. These large aerosol particles have a direct and essential impact on the air-to-sea transfer of anthropogenic trace metals, in spite of their low numerical abundance and relatively low heavy metal content.     

北京上空气溶胶浓度垂直廓线特征

利用2008—2010年北京地区3.5 km高空内飞机探测的气溶胶(粒径范围为0.10～3.00 μm)数据,分析了该地区气溶胶的时空分布特征. 结果表明:①气溶胶浓度(以数浓度计,下同)均随高度增加而减小,在1.5 km以上高空的气溶胶浓度垂直梯度变化明显低于1.5 km以下的垂直梯度变化. 4—11月气溶胶浓度季节变化表现为夏季最高、秋季次之、春季最低. ②气溶胶浓度廓线逐时(09:00—19:00)变化较清晰地反映出其受大气边界层演变的影响. 在0～1.5 km高空,白天气溶胶浓度高值出现在09:00—11:00,低值出现在13:00—14:00;而在1.5～3.5 km高空的气溶胶浓度时段分布与其相反. ③人为活动是影响气溶胶浓度区域水平分布的重要因子. ④将气溶胶浓度廓线垂直分布分为a、b、c 3类. 类型a的近地面气溶胶浓度(0～4 000 cm-3)低,垂直方向上变化很小;类型b的近地面气溶胶浓度(4 000～9 000 cm-3)较高,垂直递减明显;类型c的近地面气溶胶浓度特别高,量级达到104 cm-3,并在大气边界层顶(约1.5 km)附近迅速递减. 北京地区气溶胶浓度廓线以类型b居多.      

Condensation nucleus size distribution at mawson,Antarctica: seasonal cycle

The size distribution of atmospheric condensation nuclei (CN) has been measured at Mawson, on the Antarctic coast, during the period 1985–1990. A clear seasonal cycle is demonstrated in the size distribution with periods of marked bimodality during early spring and autumn. Between these periods, in late spring and summer, steady growth in particle size followed by a period with a relatively stable size distribution and relatively little new particle production were observed. During the remaining part of the year nucleus mode particle concentrations were low, typically less than 20 cm⁻³.     

中国3个AERONET站点气溶胶大小的识别及特征分析

?ngstr?m波长指数a是判断气溶胶粒子大小的重要参数,但当气溶胶尺度分布不满足Junge分布时,仅用a不能很好的反映气溶胶粒子的尺度信息.利用Mie散射理论和AERONET站点实测资料分析说明在0.750.6;当a2>0.3时,多以粗粒子为主,Vfine/Vtotal<0.4.利用Gobbi气溶胶图解法分析显示SACOL站AOD的大值主要是由于沙尘气溶胶的影响造成的;香河站沙尘和细粒子气溶胶都会产生大值AOD,并且图解法可以很好的区分这两种情况;太湖站受沙尘的影响较小,大值AOD绝大多数是由于细粒子气溶胶造成的.     

2018年中国长江三角洲地区气溶胶的垂直分布特征

利用主动式遥感卫星云-气溶胶激光雷达和红外探测者卫星观测(CALIPSO)提供的激光雷达资料,重点分析了2017-12～2018-11中国长江三角洲地区对流层大气中532 nm气溶胶消光系数,气溶胶退偏比,气溶胶色比以及各类型气溶胶的时空变化特征.对气溶胶的光学参数随高度变化的研究表明,与对流层高空相比,一般在对流层低空中气溶胶消光能力更强,气溶胶粒子更规则,气溶胶粒径更小.对气溶胶的光学参数随季节变化的研究表明,与冬春季相比,一般夏秋季在对流层高空中气溶胶消光能力更强,在2 km以下气溶胶粒子更规则,在对流层高空中气溶胶粒径的范围更大.长江三角洲地区全年中污染沙尘气溶胶出现的频率最高,为37. 481 6%,夏秋季烟尘、污染大陆与洁净海洋气溶胶出现的频率比冬春季高,而夏秋季沙漠沙尘气溶胶出现的频率相对较低.     

Microanalysis of the aerosol collected over south-central New Mexico during the alive field experiment,May–December 1989

Thirty-eight size-segregated aerosol samples were collected in the lower troposphere over the high desert of south-central New Mexico, using cascade impactors mounted onboard two research aircraft. Four of these samples were collected in early May, sixteen in mid-July, and the remaining ones in December 1989, during three segments of the ALIVE field initiative. Analytical electron microscope analyses of aerosol deposits and individual particles from these samples were performed to physically and chemically characterize the major particulate species present in the aerosol.Air-mass trajectories arriving at the sampling area in the May program were quite different from those calculated for the July period. In general, the May trajectories showed strong westerly winds, while the July winds were weaker and southerly, consistently passing over or very near the border cities of El Paso, Texas, and Ciudad Juarez, Mexico. Aerosol samples collected during the May period were predominantly fine (0.1–0.5 μm dia.), liquid H₂SO₄ droplets. Samples from the July experiment were comprised mostly of fine, solid (NH₄)₂SO₄ or mostly neutralized sulfate particles. In both sampling periods, numerous other particle classes were observed, including many types with probable terrestrial or anthropogenic sources. The numbers of these particles, however, were small when compared with the sulfates. Composite particle types, including sulfate/crustal and sulfate/carbonaceous, were also found to be present. The major differences in aerosol composition between the May and July samples (i.e. the extensive neutralization of sulfates in the July samples) can be explained by considering the different aerosol transport pathways and the proximity of the July aerosol to the El Paso/Juarez urban plume.Winds during the December experiment were quite variable, and may have contributed to the widely varying aerosol compositions observed in these samples. When the aircraft sampled the El Paso/Juarez urban plume, high concentrations of carbonaceous particles were collected. These C-rich particles were of three distinct types, two of which showed combustion morphologies and the third an irregular morphology. Concurrent aethalometer measurements of aerosol black carbon concentration were well correlated (r = 0.83) with the total carbonaceous particle fraction in the aerosol samples. Carbonaceous particles were not observed in abundance in any of the May or July samples (even when the winds passed over El Paso), and we attribute the high concentrations in December to increased wintertime burning of wood, fossil fuels and other combustibles in the urban area.     

天气条件及气团来源对青岛春季大气颗粒物数浓度谱分布的影响

利用2010年春季在青岛观测的不同粒径大气颗粒物数浓度,结合同期的Micaps天气图资料及后向轨迹分析资料,探讨了不同天气条件及气团来源不同时青岛大气颗粒物数浓度谱的变化特征.结果表明,沙尘发生前12h,大气中0.3~1.0μm的细粒子数浓度逐渐小幅升高,沙尘发生时>1.0μm粗颗粒物数浓度较沙尘发生前升高了1~10倍,0.3~1.0μm细颗粒物数浓度则降低了20%~45%.降雨使>1.0μm粗粒子数浓度降低>50%,降雨后大气颗粒物尤其是细粒子数浓度很快回升.雾和霾天气发生时1.0μm粗粒子数浓度较高,而局地源气溶胶中粗粒子数浓度较低,<0.7μm细粒子相对贡献较大.     

Size distributions of dust aerosol measured during the Soviet-American experiment in Tadzhikistan, 1989

Size distribution data obtained during the U.S.S.R.-U.S. dust experiment make it possible to propose a general conception about the size distribution of dust aerosols within the size range 0.005–100 μm. The microstructure for the optically active fraction of arid aerosol is approximated in the form of a log-normal distribution with parameters D = 3.5−6 μm, δ² = 0.5−0.8, which can be used when estimating radiative calculations.     

香港大气气溶胶组成与特征

选用香港空气质量监测网中11个监测站1990～1994年间TSP（总悬浮粒子）和RSP（可吸入悬浮粒子）的监测数据,分析香港大气气溶胶的化学组成与时空变化。香港大气气溶胶的浓度较低,其浓度的季节变化主要受气候变化的影响。C是大气气溶胶中最重要的化学成分,它支配着气溶胶的季节和空间变化。SO^2-₄、NH⁺₄和NO^-₃的浓度很低,空间分布很均匀,其季节变化主要受东亚季风控制。海洋气溶胶主要以较大的颗粒形式存在,它的来源稳定且空间分布较均匀。扬尘浓度主要受降雨和湿度的影响。V和Ni浓度的季节变化与燃料油消耗量的季节变化相同,其空间的变化反映了当地工业窑炉排放对香港气溶胶的影响     

Submicron aerosol size distributions measured over the tropical and South Pacific

Size distributions of aerosol particles in the radius range of 0.006–0.53 μm were measured over the Pacific Ocean along the 150° longitude from about 20°N to 55°S. Throughout the tropical trade wind region, the size distribution of fine particles was relatively stable and exhibited a double-peaked characteristic with one peak at about 0.1 μm and the other in the 0.02–0.04 μm region, separated by a minimum at about 0.06 μm. The total concentrations of particles were in the 150–300 cm⁻³ range with 60–150 cm⁻³ residing in the accumulation mode (0.06<r<0.5 μm). South of the trade wind region, the measured size distributions and meteorological conditions were more diverse. Periods with very low concentrations in the accumulation mode were associated with regions of large-scale precipitation. Large increases in the number of nucleation mode particles were found in air masses with low concentrations of particles in the accumulation mode.     

Physicochemical and toxicological characteristics of nanoparticles in aerosols in southern Thailand during recent haze episodes in lower southeast Asia

Transboundary haze from biomass burning is one of the most important air pollutions in Southeast Asia. The most recent serious haze episode occurred in 2015. Southern Thailand was affected by the haze during September to October when the particulate matter concentration hit a record high. We investigated physical and chemical characteristics of aerosols, including concentration and aerosol size distribution down to sub-micron sizes during haze episodes in 2013 and 2015 and, for reference, an insignificant haze period in 2017. The highest total suspended particulates and PM₁₀ levels in Hat Yai city were 340.1 and 322.5 µg/m³. The mass fractions were nanoparticles (< 100 nm) 3.1%-14.8% and fine particles (< 1 µm) 54.6%-59.1%. Polycyclic aromatic hydrocarbon size distributions in haze periods peaked at 0.75 µm and the concentrations are 2-30 times higher than the normal period. High molecular weight (4-6 ring) PAHs during the haze episode contribute to about 56.7%-88.0% for nanoparticles. The average values of benzo(a)pyrene toxic equivalency quotient were 3.34±2.54ng/m³ in the 2015 haze period but only 0.89±0.17 ng/m³ in 2017. It is clear that particles smaller than 1 µm, were highly toxic. Nanoparticles contributed 19.4%-26.0% of total BaP-TEQ, whereas the mass fraction is 13.1%-14.8%. Thus the nanoparticles were more carcinogenic and can cause greater health effect than larger particles. The fraction of BaP-TEQ for nanoparticles during 2017 non-haze period was nearly the same, while the mass fraction was lower. This indicates that nanoparticles are the significant source of carcinogenic aerosols both during haze and non-haze periods.