基于典型站位AERONET数据气溶胶类型分析

气溶胶是影响大气环境的重要因素,气溶胶光学厚度（AOD）是气溶胶的重要光学特征参数之一,气溶胶类型分析可以对区域大气研究提供科学依据.基于2015年12月—2019年11月AERONET数据选取的11个典型站位不同波段的AOD进行层次聚类分析,将所选站位最终划分为北京、沿海、太湖、西藏4个区域.然后基于图形分类法划分为6种气溶胶类型（清洁、沙漠粉尘、大陆、次大陆、城市工业和生物质燃烧型）.北京区域主要的气溶胶类型为城市工业型和大陆型,其中冬季主要为大陆型和清洁型、春季为大陆型和城市工业型、夏季和秋季主要为城市工业型气溶胶;沿海区域主要的气溶胶类型为大陆型气溶胶,其中冬、夏和秋季主要为大陆型和清洁型、春季主要为城市工业型和大陆型气溶胶;太湖区域城市工业型气溶胶占比最多,为41.96%,冬、春和夏季主要为城市工业型气溶胶,秋季主要为大陆型气溶胶;西藏区域清洁型气溶胶占比为80.53%,春夏秋冬四季以清洁型气溶胶为主.     

天津市冬季气溶胶吸湿因子的粒径分布特征

气溶胶粒径吸湿增长因子［g（RH）］是影响气溶胶消光和气溶胶辐射强迫的重要因素.利用吸湿性串联差分电迁移率分析仪（HTDMA）观测了天津市冬季不同污染状态下气溶胶粒子g_m（RH）的粒径分布.同时基于水溶性离子的粒径分布,利用κ-Köhler理论获取了较宽粒径范围内（60 nm~9.8 μm）的g_κ（RH）,为环境状态下气溶胶光学参数和直接辐射强迫的模拟提供基础.结果表明,清洁状态下大气光化学反应较为活跃,超细粒子（<100 nm）的g_m（RH）较高,g_m（RH=80%）在1.30以上.重度污染天,气溶胶中水溶性离子的质量分数随粒子粒径增大而增加,导致g_m（RH）随着粒子粒径增大而增大,300 nm粒子的g_m（RH=80%）和g_m（RH=85%）分别可达1.39和1.46.在较宽粒径范围（60 nm~9.8 μm）内,不同模态气溶胶的吸湿性强弱表现为积聚模态>爱根模态>粗模态.大气重污染过程中气溶胶粒径明显增大,积聚模态气溶胶中NO₃^-和SO₄^2-含量较清洁天明显增加,受此影响,污染状态下积聚模态气溶胶的吸湿性较清洁天明显增强,g_κ（RH）达到1.3~1.4,具有强吸湿性的气溶胶粒径范围也同时扩大,在0.18~3.1 μm粒径段均较高,对能见度恶化有重要的贡献.     

Deliquescence of Deposited Atmospheric Particles on Leaf Surfaces

A large fraction of deposited aerosol particles on leafsurfaces represents hygroscopic material in a high humidity environment, likely to become deliquescent within the water vapour transpired by the leaf. Microscopic observations on leaf surfaces of beech, kohlrabi and elder leaves grown in a particle-free environment and/or treated with defined particle load are presented. Spreading of deliquescent particles, formation of salt crusts, and encoating of and by waxes was observed. Deliquescence of NaNO₃ particles (deliquescence point 74% RH at 25 °C) was observed on and near the stomata at 35% relative humidity (RH) of the surrounding air, illustrating the influence of the boundary layer. Aerosols are difficult to identify on leaf surfaces, as similar patterns may be produced by deliquescent particles and processes like salt creep. These problems are especially important on leaves from the natural environment if only scanning electron microscopy (SEM) is used. These patterns could appear similar to the fused waxes described in forest decline research. Strong gradients are formed between deliquescent particles and the apoplastic solution within the leaf, promoting cuticular and stomatal uptake.     

Heterogeneous Sulfate Formation on Dust Surface and Its Dependence on Mineralogy: Balloon-Borne Observations from Balloon-Borne Measurements in The Surface Atmosphere of Beijing, China

This study focuses on providing a direct insight into the process by which sulfate is formed on mineral dust surface in the actual atmosphere. Six sets of aerosol measurements were conducted in the outskirts of Beijing, China, in 2002–2003 using a tethered balloon. The mineralogy of individual dust particles, as well as its influence on the S (sulfur) loadings was investigated by SEM-EDX analysis of the directly collected particles. The mixed layer in the urban atmosphere was found to be quite low (500–600m), often appearing as a particle dense stagnant layer above the surface. It is suggested that mineral dust is a common and important fraction of the coarse particles in Beijing (35–68%), and that it is relatively enriched with Calcite (>28%). An exceptional amount of S was detected in the mineral particles, which can be explained neither by their original composition, nor by coagulation processes between the submicron sulfates and the dust. Heterogeneous uptake of gaseous SO₂, and its subsequent oxidation on dust was suggested as the main pathway that has actually taken place in the ambient environment. The mineral class found with the largest number of particles containing S was Calcite, followed by Dolomite, Clay, Amphibole etc., Feldspar, and Quartz. Among them, Calcite and Dolomite showed distinctly higher efficiency in collecting sulfate than the other types. A positive correlation was found with the number of S containing particles and the relative humidity. Calcite in particular, since almost all of its particles was found to contain S above 60% r.h. On the other hand, the active uptake of SO₂ by the carbonates was not suggested in the free troposphere downwind, and all the mineral classes exhibited similar S content. Relative humidity in the free troposphere was suggested as the key factor controlling the SO₂ uptake among the mineral types. In terms of sulfate loadings, the relationship was not linear, but rather increased exponentially as a function of relative humidity. The humidity-dependent uptake capacity of mineral types altogether showed an intermediate value of 0.07 gSO₄ ²⁻ g⁻¹ mineral at 30% r.h. and 0.40 gSO₄ ²⁻ g⁻¹ mineral at 80%, which is fairly consistent with laboratory experiments.     

Formation and Transport of Atmospheric Aerosol over Athens, Greece

The effects of meteorology on ambient aerosol concentrations and aerosol transport, within the Greater Athens Area during the summer period, was investigated. Measurements of size fractionated anions and cations were made at two sites (inland at Ag. Stefanos and on the coast at Pireas) within the Greater Athens Area. The wind regime exhibited a distinctinfluence such that the sea-breeze circulation strongly enhanced the formation of secondary aerosols. For sulphate the difference in concentration between the two sites was,on average, 8 times greater on sea-breeze days compared with Etesian days (warm days with NE winds). During `normal' days,any differences in concentrations were possibly due to localemissions. Elevated concentrations in the fine mode were detectedat both sites during the sea-breeze days. The sea-breezecirculation enhances the development of secondary aerosolswhich was clearly shown at the inland site. Nitrous acid,hydrochloric acid and particulate nitrate, sulphate andammonium increase during sea-breeze days. Elevated levelsof nitrate, 4 m diameter, were particularly observedon the days with a strong sea-breeze circulation. Sulphatewas well correlated with both sulphur dioxide and ammoniumsuggesting the production of NH₄HSO₄/(NH₄)₂SO₄ aerosols, formedthrough the neutralisation of NH₃ with sulphuric acids.Ammonium sulphate was found to be the major ammoniumcomponent in Athens.     

充装条件对水基热气溶胶灭火剂燃速影响规律的研究

水基热气溶胶灭火剂是以替代哈龙为目的而研制的新一代灭火制；主要论述了充装量，充装密度，燃烧器结构等充装条件对水基热气溶胶灭火剂燃烧速度的影响规律，并分析了充装量，充装密度，燃烧器结构影响燃烧速度的原因。     

电热原子吸收法测定大气中微量元素镉

用HNO_3—HClO_4硝解聚氯乙烯膜,用石墨炉原子吸收法直接测定大气颗粒物中的镉,方法准确度使用标准物质,在选定的条件下,相对误差0.011％,变异系数为10.83％,回收率在90.2～101.6％,方法操作简便测定速度快。     

Eperimental study of photooxidation products of ethylbenzene

Smog chamber experiments were performed to investigate the composition of products formed from photooxidation of aromatic hydrocarbon ethylbenzene.Vacuum ultraviolet photoionization mass spectrometer and aerosol time-of-flight mass spectrometer were used to measure the products in the gas and particle phases in real-time.Experimental results demonstrated that ethylphenol,methylglyoxal,phenol,benzaldehyde,and 2-ethylfurane were the predominant photooxidation products in both the gas and particle phases.However,there were some differences between detected gas phase products and those of particle phase,for example,2-ethylfurane,ethylglyoxylie acid,nitroethylbenzene,3,4-dioxopentanal and ethyl-nitrophenol were only existing in the particle-phase.The possible reaction mechanisms leading to these products were also discussed and proposed.     

Ecophysiological responses of winter wheat seedling to aerosol wet deposition of Xi’an area, China

Aerosol leads to 30% reduction in solar radiation reaching the earth’s surface, and a similar reduction in crops yield for both wheat and rice. To determine the effect of aerosol wet deposition on crops, aerosol samples were collected in September, 2006 at Xi’an urban suburb (34?44 N, 109?49 E), and wheat seedlings were treated with aerosol of different concentrations in laboratory conditions. Changes in physiological and biochemical parameters of wheat seedlings were measured. In comparison with the control, the activities of superoxide dismudase (SOD) and catalase (CAT) and the concentration malondialdehyde (MDA) and oxidized glutathione (GSSG) of wheat seedlings increased progressively with increasing concentrations of added aerosol, while the opposite trend was seen for the activities of nitric oxide synthase (NOS), the concentrations of glutathione (GSH) and nitric oxide (NO), and the ratio of GSH/GSSG. When the seedlings were treated with the aerosol of 1 and 2 mg/L, the coleoptile elongation, shoot elongation and biomass accumulation were increased, the effect at treatment of 2 mg/L was most significant. However, aerosol treatments with rates of 3 and 4 mg/L resulted in a decrease in coleoptile elongation, shoot elongation and biomass accumulation in seedlings, and significant effect was for the treatment of 4 mg/L. Hence, lower concentrations of aerosol wet deposition were in favor of crops growth, but its higher concentrations could result in deleterious effects for crops and decreased crops growth.     

沙漠地区沙尘气溶胶含量变化的原因分析

利用中国大陆气溶胶指数(TOMS AI)、太阳辐射、沙尘能见度、降水量等观测资料,对中国西北部沙漠地区沙尘气溶胶含量进行分析.结果表明,沙漠地区AI值不但取决于沙尘暴的发生,而且取决于太阳辐射.这表明沙尘暴起沙模型和尘卷风与干热对流的联合起沙模型互为补充,沙漠地区上空的沙尘气溶胶含量是它们共同作用的结果,而由太阳辐射引发的尘卷风与干热对流较沙尘暴过程更为重要.