Surface cloud condensation nuclei and condensation nuclei measurements at Reno,Nevada

Surface aerosol measurements from a moderately populated high mountain valley are interpreted in terms of local wind velocity and meteorology. Diurnal trends are apparent with light winds and especially during wintertime temperature inversions when the concentrations are dominated by local anthropogenic sources. Under conditions of higher wind speeds when the surface concentrations appear to be representative of widespread areas, a seasonal trend is revealed. Cloud condensation nuclei (CCN) concentrations are much higher during the late spring (> 1000 cm⁻³) than during the winter (< 400 cm⁻³) but the condensation nuclei (CN) concentrations are not seasonal. The seasonality of the CCN is probably caused by differences in the long range transport of particles from distant California population centers.     

Project aguila: In situ measurements of Mexico City air pollution by a research aircraft

Measurements of aerosol concentrations, chemical species and meteorological quantities in the air above Mexico City were obtained from an instrumented research aircraft. Concentrations of particles in the size range between 0.12 and 3.12 μm were nearly invariant with height, and typical values were of the order of 5000 cm⁻³. However, particles smaller than 0.12 μm were confined to the lowest few hundred meters of the atmosphere until the morning temperature inversion dissipated, after which time those particles, together with newly formed particles created by secondary processes, mixed to a greater height above the city. Total particle concentrations near the surface attained values in excess of 60,000 cm⁻³. An examination of the corresponding profiles of SO₂ suggests that combustion processes are likely sources for the additional small particles.     

Biogenic and anthropogenic organic compounds in eolian particulates in the East Mediterranean region—I. Occurrence and origin

Lipids of biogenic and anthropogenic origin were determined in aerosol samples, collected seasonally, in a coastal area on the north of the island of Crete. Lipid classes such as n-alkanes, hopanes, polycyclic aromatic hydrocarbons, fatty alcohols, fatty acids, fatty acid salts and α,ω-dicarboxylic acids were characterized by GC/MS and GC/FID analysis, in terms of their contents of homologous compound series. The concentrations ranged between 56 and 215 ng m⁻³ for n-alkanes, 10 and 52 ng m⁻³ for polycyclic aromatic hydrocarbons, 2 and 31 ng m⁻³ for fatty alcohols, 13 and 279 ng m⁻³ for fatty acids, 24 and 220 ng m⁻³ for fatty acid salts and 0.4 and 7.5 ng m⁻³ for α, ω-dicarboxylic acid salts. The prevailing winds were influencing the composition of the eolian particles. Generally, aerosols sampled during south wind events predominantly contained lipids originating from higher plants, while when north and northwest winds prevailed the major components were of marine origin. The absence of unsaturated fatty acids in all aerosol samples is related to the presence of α,ω-dicarboxylic acids, which are believed to be their photo-oxidation products.     

Aerosol characteristics of Arctic haze sampled during AGASP-II

As part of the second Arctic Gas and Aerosol Sampling Program (AGASP-II), Arctic aerosol samples were collected by the NOAA WP-3D aircraft in spring 1986. The samples were analyzed in bulk and individual-particle form, using ion chromatography (IC) and electron microscopy (EM), respectively. Information on the chemical composition of the aerosol as determined by various techniques is presented, as well as morphology, concentration, and size distribution data obtained from individual particle analyses. For most flights, a stratospheric sample and a haze profile samople were collected. Haze samples exhibited greater particle concentrations than stratospheric samples, the highest concentrations in haze reaching ∼10³ cm⁻³ (non-volatile particles > 0.05 μm diam). Sulfur was consistently observed to be a major element in both large and small particles in haze samples. Crustal elements such as Si, Al, K, Ca and Fe were often present in significant concentrations together with S. Particles that did not emit X-rays, possibly organic or sooty C, were observed in significant concentrations in both tropospheric and stratospheric samples. Chemical spot tests confirmed that SO₄²⁻ was the major S-containing species and that NO₃⁻ was not nearly as prevalent as SO₄²⁻ in the Arctic aerosol particles. The mass concentrations of major anions (Cl⁻, SO₄²⁻ and NO₃⁻) and cations (Na⁺, K⁺, NH₄⁺, Ca²⁺ and Mg²⁺) in the bulk aerosols were determined using IC. The ratios between ion concentrations, e.g. Ca²⁺/Na⁺, SO₄²⁻/Na⁺ and Cl⁻/Na⁺, may serve as indicators of aerosol origins and mixing status of various air masses. Aerosols collected on six flights demonstrated variability of particle characteristics in relation to sources and transport of Arctic haze.     

Photochemical formation of particulate dicarboxylic acids under long-range transport in central Japan

Long-range transport (LRT) of photochemical air pollution from the coastal area with large emission sources to the inland mountainous region occurs very frequently in the central Japan region on clear summer days. It is caused by local winds and the transport route is almost-fixed geographically. Along this route, behavior of dicarboxylic acids in the airborne aerosols was investigated in the cooperative field observation of meteorology and chemistry. Measurements were made every 3-h at inland sites.The concentrations of dicarboxylic acids as well as NO₃⁻ and total organic C increased in the daytime and decreased at night. The maximum are attained when the transported air mass was arrived at the sampling sites. These diurnal variations were similar to that of O₃.In the daytime, although the phthalates (di-n-butyl and dioctyl), n-alkanes (C₂₁C₃₂) and pinon aldehyde were abundant in the airborne aerosols, the dicarboxylic acids (C₂C₁₀) were the most abundant species and the total concentrations attained from 30 to 50% of the total organic particulate matter. In addition, of the dicarboxylic acids, more than 70% were estimated to be produced by photochemical reactions in the daytime. Thus, it was concluded that most of the dicarboxylic acids were produced by the photochemical oxidation of anthropogenic compounds during LRT.     

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.     

Anthropogenic contributions to the carbonaceous content of aerosols over the Pacific Ocean

During a joint U.S./U.S.S.R. research cruise from 3 May to 27 July 1987 both total and fine (< 2 μm) particulate material was sampled. This cruise started in the Hawaiian Islands and then proceeded to the Kamchatka peninsula, south to Wellington, New Zealand, south of Australia into the Indian Ocean, to Singapore and then returned to the Hawaiian Islands by sailing just north of the Equator. Particulate samples, collected on quartz fiber and Teflon filters, were analysed for organic and elemental carbon by transmission thermo-optical carbon analysis and for trace elements by energy dispersive X-ray fluorescence.In the Northern Hemisphere the total particulate, organic carbon and elemental carbon concentration ranges were, respectively, 10–25, 0.5–2.5 and 0–0.3 μg m⁻³. In the Southern Hemisphere they were, respectively, 5–10, <0.6 and <0.02 μg m⁻³. In the Northern Hemisphere the fine particulate concentration range was 2–15 μg m⁻³ and the fine fraction varied from 20 to 80% of total aerosol loading. In the Southern Hemisphere the fine particulate loading was 1.2–1.7 μg m⁻³ and was usually less than 20% of the total particulate mass.Chemical mass balance (CMB) modeling was used to determine possible anthropogenic particulate contributions to the ocean aerosol. Readily available source profiles were used for CMB modeling. Sea-salt aerosol was represented by either the conventional EPA marine source profile or by the average of ambient ocean aerosols sampled in very clean mid-ocean regions. Usually 60–90% of ambient particulate mass was “explained” by the CMB model. Sources such as soil, catalytic auto emissions and wood-burning emissions were found to be possible contributors to the ocean aerosol, especially in the Northern Hemisphere. Anthropogenic contributions were estimated to contribute from 10 to 30% of oceanic aerosol mass. Emissions from a hugh forest fire that burned in northern China during the spring of 1987 were possibly detected, but the CMB model cannot distinguish this source from emissions from heating and cooking with wood.Since anthropogenic emissions are mainly combustion emissions which usually contain a large carbon component, carbon data is essential to CMB modeling. The relatively good CMB results obtained in this study suggest that it might be useful to develop source profiles for major emission sources in those countries which contribute most directly to oceanic aerosols. Perhaps characteristic national or regional source profiles could be developed.     

Rainwater composition in Athens,Greece

Wet precipitation-only samplers were used to collect wet deposition at two sites in the Athens basin, Greece for the period March 1986–February 1987.Concentrations of major cations (H⁺, NH⁺₄, Na⁺, K⁺, Ca²⁺ and Mg²⁺) and major anions (Cl⁻, NO⁻₃ and SO²⁻₄) were determined for the first time in rainwater samples in Greece. Bicarbonate concentrations were calculated. The relative importance of natural and anthropogenic sources were estimated by a chemical balance. The majority of rain collected has a neutral or alkaline character. Acidity was due to the presence of H₂SO₄ and HNO₃. The statistical analysis of the correlation between the concentration of chemical species confirm the influence of natural and anthropogenic sources. In all samples, SO²⁻₄ concentrations exceed NO⁻₃ concentrations despite the dominance of low S oil burning in the region. The wet flux of S was calculatd to be 0.34 gm⁻²a⁻¹.     

The vertical distribution of aerosols and acid related compounds in air and cloudwater

Vertical profiles (surface to 5 km) of aerosol particle number concentration, NO_y′ mixing ratio, and cloudwater SO₄²⁻ and NO₃⁻ equivalent concentration were obtained in three field studies: North Bay, Ontario, during the summer of 1982 and the winter of 1983–1984, and Syracuse, New York, during the fall of 1984. The measurements from these locations and different seasons are compared. Generally, airborne concentrations are highest with air-mass back trajectories from the south and lowest with back trajectories from the north. For the southerly trajectories, median particle number concentrations (0.2–2 μm) near ground level (950 mb) vary from 1700 cm⁻³ during the summer project to 800 cm⁻³ during the winter project. At 700 mb, the south trajectory particle number concentration ranged between 60 and 170 cm⁻³. Median NO_y′ mixing ratios for southerly back trajectories were approximately 6 and 9 ppb at 950 mb and 0.4 and 0.8 ppb at 700 mb for the fall and winter projects, respectively. Comparison of particle number concentration profiles outside of cloud with cloud droplet plus interstitial aerosol particle number concentrations inside cloud indicate that cumulus clouds can transport aerosols vertically from below cloud base. In contrast, stratiform clouds have similar concentrations inside the clouds as outside at the same altitude. The vertical variations of cloudwater sulphate and nitrate concentrations and the NO₃⁻/SO₄²⁻ equivalent concentration ratio are discussed for each of the three field studies.     

东海大气气溶胶中二元羧酸的分布特征及来源

大气气溶胶中的二元羧酸因其在全球气候变化中的潜在作用而受到广泛关注.利用2011年5月12日-6月6日在东海采集的气溶胶样品,分析其中水溶性二元羧酸及常量离子浓度,探讨东海气溶胶中二元羧酸的时空分布特征及来源.结果显示东海大气气溶胶中乙二酸、丙二酸和丁二酸的浓度分别为26.0～1475.5 ng·m-3、0.1 ～61.4 ng·m-3和0.1～132.4 ng·m-3,乙二酸在这3种二元羧酸中的贡献最大,为88.3％.东海气溶胶中二元羧酸浓度的昼夜变化不显著.空间分布整体呈现近海高、远海低的趋势.气团的来源和迁移路径以及气象因素影响气溶胶中二元羧酸的分布,气团来自污染较重的陆源时气溶胶中二元羧酸的浓度较高,气团来自清洁的海洋源时,二元羧酸的浓度则较低;阴雾天气时气溶胶中二元羧酸浓度相对较高,降雨发生时二元羧酸的浓度较低.二元羧酸与常量离子的相关性分析表明,自然源和人为源释放的挥发性有机物质在液相中氧化生成二元羧酸是东海大气气溶胶中二元羧酸的主要源,而汽车尾气和生物质燃烧的一次排放、海洋源以及碱性粗颗粒吸收气体二元羧酸不是主要源.液相中乙醛酸氧化形成的乙二酸和长链二元羧酸氧化形成的乙二酸对东海气溶胶中乙二酸的贡献分别为41％和59％.     

Polynuclear aromatic hydrocarbon degradation by heterogeneous reactions with N2O5 on atmospheric particles

The degradation of particulate polynuclear aromatic hydrocarbons (PAH) on atmospheric soot particles in the presence of gas phase dinitrogen pentoxide (N₂O₅) was explored. Dilute diesel and wood soot particles containing PAH were reacted with∼10ppm of N₂O₅ in a 200 ℓ continuous stirred tank reactor (CSTR). To provide a stable source of particles for reaction in the CSTR, diesel or wood soot particles were injected at night into a 25 m³ Teflon outdoor chamber. The large chamber served as a reservoir for the feed aerosol, and the aerosol could then be introduced at a constant flow rate into the CSTR. PAH-N₂O₅ heterogeneous rate constants for wood soot at 15°C ranged from2 × 10⁻¹⁸to5 × 10⁻¹⁸ cm³ molecules⁻¹ s⁻¹. For diesel soot the rate constants at 16°C were higher and ranged from5 × 10⁻¹⁸to30 × 10⁻¹⁸ cm³ molecules⁻¹ s⁻¹. Comparisons with other studies suggest that sunlight is the most important factor which influences PAH decay. This is followed by ozone, NO₂, N₂O₅ and nitric acid. The rate constants of nitro-PAH formation from a parent PAH and N₂O₅ were of the order of1 × 10⁻¹⁹−1 × 10⁻¹⁸ molecules⁻¹s⁻¹. The uncertainty associated with all of these rate constants is± a factor of 3. Given, however, the small magnitude of the rate constants and the low levels of N₂O₅ present in the atmosphere, we concluded that PAH heterogeneous reactions with gas phase N₂O₅ degrade particle-bound PAH or to form nitro-PAH from PAH arenot very important. (Direct application of the specific rate constants derived in this study to ambient atmospheres should not be undertaken unless the ambient particle size distributions and chemical composition of the particles are similar to the ones reported in this study.)     

Vertical distribution of atmospheric aerosol size distribution over south-central New Mexico

The vertical distribution of background atmospheric aerosols was measured over south-central New Mexico as a part of the Atmospheric Lidar Verification Experiment (ALIVE) during four research field periods in the summers and winters of 1989 and 1990. Aerosol size distribution was measured from the surface up to 4500 m above sea level (asl) over the particle size range 0.1∼32 μm, using two Particle Measuring Systems (PMS) probes mounted on the wings of the NOAA King Air research aircraft. Vertical profiles of aerosol number concentrations of both fine- (0.1–2.0 μm) and coarse- (>2.0 μm) particle modes show seasonal differences, with higher number concentrations and higher mixed layer heights during summers. The measured aerosol size distribution data of each ALIVE intensive were averaged for boundary layer and free troposphere regions. These data mostly exhibit bi-modal distributions, typical for the continental atmospheric aerosols. Exceptions were the free troposphere size distributions measured during December 1989 (ALIVE III) and June 1990 (ALIVE IV), which resemble Junge's power-law distribution. Each of the averaged aerosol size distributions was approximated by the sum of log-normal distributions. Different characteristics of aerosol size distribution were observed between the two summer measurements of 1989 and 1990. Back-trajectory analysis revealed that decreased aerosol concentrations were observed during June 1990 when the air mass was transported from the southwestern U.S.A.     

Kinetics of evaporation of ammonium chloride and ammonium nitrate aerosols

The evaporation rates of ammonium chloride and ammonium nitrate were measured by continuously and rapidly removing gaseous NH₃ and HNO₃ or HCl from aerosols in an annular denuder. The experiments gave the evaporation rates in terms of mass loss of chloride or nitrate which can be expressed conveniently as the rates of reduction of aerosol radius with time. Both dry aerosols (humidity 30–60% r.h.) and aqueous aerosols (humidity ca 97% r.h.) were studied. Dry aerosols evaporate at rates of −1.05 Å s⁻¹ for NH₄Cl and −0.45Å s⁻¹ for NH₄NO₃, while the evaporation rates of aqueous aerosols expressed as for equivalent dry particles are −4.52 Å s⁻¹ for NH₄Cl and −0.49 Å s⁻¹ for NH₄NO₃. The experimentally measured rates are independent of particle radius and remarkably low compared with those predicted from existing theories of aerosol evaporation, thus implying that there is an unknown kinetic constraint to the achievement of equilibrium at atmospheric temperature and pressures.     

Evaluation of absorption properties of atmospheric aerosols at solar wavelengths based on chemical characterization

The imaginary part of the complex index of refraction of atmospheric aerosols was determined by calculation based on chemical characterization. Atmospheric aerosols in Sapporo were chemically characterized, and were estimated to be mainly composed of elemental C, organics, (NH₄)₂SO₄, NH₄NO₃, sea salt and soil particles. Using the complex index of refraction of each chemical species, the volume extinction and scattering coefficients of the particles composed of the chemical species were calculated, using Mie scattering theory. The single scattering albedo of the aerosols was obtained as the ratio of the total volume scattering coefficient to the total volume extinction coefficient. The imaginary part of the complex index of refraction of the aerosols was determined by matching the calculated sigle scattering albedo for the aggregate aerosol to that calculated from the sum of the individual aerosol components. The monthly mean imaginary part of the complex index of refraction of aerosols in Sapporo ranged from 0.024 in August to 0.047 in February in 1982.The atmospheric solar heating rate was calculated by solving the equation of radiative transfer in turbid atmospheres. It was estimated that the atmospheric boundary layer in Sapporo was heated at the rate of 2.0–2.5°C day⁻¹ in February as a result of absorption of visible solar radiation by aerosols.     

南半球海洋大气气溶胶单颗粒的理化特性分析

运用透射电子显微镜-X射线能谱技术分析了中国第29次南极科考期间采集的大气气溶胶单颗粒样品,获得颗粒物的形貌特征、混合状态、成分组成及数量分布等信息.结果表明,航渡区域海洋上空的颗粒物主要表现为4类:海盐颗粒、矿物颗粒、富硫颗粒和含碳颗粒,其中海盐颗粒占主导,本研究将海盐颗粒又分为新鲜、部分老化及完全老化的海盐颗粒.部分和完全老化的海盐颗粒占海盐颗粒总数的86%,且部分老化的海盐颗粒表面及完全老化的海盐颗粒以长条状Na2SO4成分为主.同时,发现两处采样点(印度洋中东部和南极内陆)的样品中富硫颗粒较多,根据后向气团轨迹判断这些富硫颗粒主要来源于海洋地区,推测是由海洋表面浮游生物释放的二甲基硫(dimethyl sulfide,DMS)经过大气氧化形成.本研究表明,南半球海洋大气中海盐颗粒老化是由海洋表面释放的DMS控制,这不同于北半球海洋大气中人为源影响的海盐颗粒老化现象.     

秋冬季节京津渤地区局地环流特征及气溶胶分布规律

在平稳天气条件下,京津渤地区受燕山山脉地形影响,形成地形局地环流。地形环流的高度一般在1700m左右,平均水平范围约100—200km。平原中,北京、天津等大城市的作用,又使局地环流流场产生扰动,城市环流的高度约450m,水平范围约30—40km。城市环流的水平辐合可达5×10~(-4)sec~(-1)。在平原增热明显的日子里,渤海湾沿岸出现向岸风,海风深入内陆的距离约30—40km,厚度约300多米,海风与陆上西南风造成辐合,其辐合量达×10~(-4)sec~(-1)。 当京津渤地区在典型的局地环流控制时,如有城市环流和海风环流相迭加,可以出现严重的污染状况,大气气溶胶浓度可比平常情况下高一个量级。     

Emission of particulate and gaseous pollutants from household laser processing machine

Indoor air quality (IAQ) directly affects the health of occupants. Household manufacturing equipment (HME) used for hobbies or educational purposes is a new and unexplored source of air pollution. In this study, we evaluated the characteristics of particulate and gaseous pollutants produced by a household laser processing equipment (HLPE). Various target materials were tested using a commercial HLPE under various operating conditions of laser power and sheath air flow rate. The mode diameters of the emitted particles gradually decreased as laser power increased, while the particle number concentration (PNC) and particle emission rate (PER) increased. In addition, as the sheath air flow rate quadrupled from 10 to 40 L/min, the mode diameter of the emitted particles decreased by nearly 25%, but the effect on the PNC was insignificant. When the laser induced the target materials at 53 mW, the mode diameters of particles were <150 nm, and PNCs were >2.0 × 10⁴ particles/cm³. Particularly, analyses of sampled aerosols indicated that harmful substances such as sulfur and barium were present in particles emitted from leather. The carcinogenic gaseous pollutants such as acrylonitrile, acetaldehyde, 1,3-butadiene, benzene, and C₈ aromatics (ethylbenzene) were emitted from all target materials. In an actual indoor environment, the PNC of inhalable ultrafine particles (UFPs) was >5 × 10⁴ particles/cm³ during 30 min of HLPE operation. Our results suggest that more meticulous control methods are needed, including the use of less harmful target materials along with filters or adsorbents that prevent emission of pollutants.     

上海北侧区域海陆风对污染物扩散的影响

利用数值模拟方法研究了上海北侧区域海陆风对污染物扩散的影响,包括上海城郊-崇明岛-启东市区及这三区域之间的北支水道与南支水道.使用当量法表征太阳辐射和长波辐射引起的近地面空气热量变化,模拟结果与ECMWF再分析数据呈现较好的一致性.结果表明,在海风阶段,宽海(南支水道)、窄海(北支水道)区域都能形成海风,前者较后者发生...     

Processes affecting concentrations of aerosol strong acidity at sites in eastern England

Concentrations of aerosol strong acidity and related species have been measured at sites in eastern England using a sampler in which ammonia is pre-separated by a denuder. High concentrations occurred at a coastal site and were associated with air advected over the North Sea. At inland sites, ammonia concentrations were higher and the aerosol was more substantially neutralized. Daytime concentrations of aerosol H⁺ exceeded those measured at night, despite higher daytime levels of ammonia, presumably due to more effective production of H₂SO₄ during daytime hours. Concentrations of acidic aerosols were within the range 0–178 neq m⁻³, well below those observed at many eastern North American sites with lower concentrations of ammonia.     

The spatial distribution and particle size of some inorganic nitrogen,sulphur and chlorine species over the North Sea

The use of filter packs and a cascade impactor during a series of research cruises in the southern area of the North Sea has yielded detailed spatial distribution patterns of aerosol concentrations, Cl⁻, NO₃⁻, SO₄²⁻¹ and NH₄⁺ and gaseous concentrations, HCl, HNO₃ and NH₃. The overall distribution of the atmospheric concentrations closely parallels published modelled results for metallic species. The chemical transformations of these aerosols and gases are investigated together with their interactions with the seasalt aerosol. Aerosol chloride loss is greatest in the more polluted areas, whilst concentrations products of NH₃ with HNO₃ and HCl appear insufficient to sustain the existence of NH₄NO₃ and NH₄Cl. Nitrate is associated predominantly with larger particles and appears to be present substantially as a surface coating on marine aerosol. The total dry deposition input for nitrogen species is calculated for the southern sector with extrapolation to the whole of the North Sea, using particle size weighted deposition velocities of 0.63 and 0.21 cm s⁻¹ for NO₃⁻¹ and NH₄⁺, respectively, and literature-derived values for the gaseous constituents. Finally the use of air-mass back trajectories illustrates the role of source regions in influencing the chemical composition of the North Sea atmosphere.