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。     

含碳气溶胶研究进展：有机碳和元素碳

含碳气溶胶是我国大气区域性复合型污染的重要物种,对全球气候变化、辐射强迫、能见度、环境质量、人类健康等会产生重要影响.主要从含碳气溶胶来源及成因、环境影响、样品采集及测试等方面对国内外相关研究进行了评述,讨论了有机碳和元素碳研究中存在的关键和难点问题,并对其发展前景进行了展望.     

含碳气溶胶采样偏差评估方法研究进展

含碳气溶胶采样偏差是影响含碳气溶胶及大气颗粒物精确测定的主要因素之一,进而影响大气颗粒物的源解析、环境效应分析、污染防治对策制定等。分析了含碳气溶胶采样偏差的产生原因,综述了目前研究所用的衡量采样偏差的方法,并分析了方法的优缺点,探讨了引起采样偏差的主要影响因素,最后对今后的相关研究方向进行了展望。     

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。     

超高效气溶胶净化系统有效性现场检验研究

各类超高效气溶胶净化系统普遍存在的较为突出的问题是:缺乏系统工作有效性现场检测手段,难以判断系统防护是否失效。根据超高效滤料过滤特性和测试原理,并在分析了大气气溶胶对过滤效率测试影响的基础上,提出大气气溶胶背景下,基于粒数浓度测量和使用发生的高浓度单分散气溶胶作为实验气溶胶的净化系统防护有效性现场检验测试技术及系统组成,并进行了验证。     

大气气溶胶含碳物质基本特征综述

准确界定了气溶胶含碳物质,特别是有机碳和元素碳的基本概念,指出了元素碳与黑碳的异同,总结了有机碳和元素碳的排放源,以及二次有机碳的经验公式.阐述了有机碳、元素碳对全球气候、大气化学过程及人体健康带来的危害及机理.归纳了气溶胶中有机碳、元素碳组分的空间分布特征、时间变化特征.概述了国内气溶胶有机碳、元素碳的研究状况,指出国内相关研究重点和趋势.     

大气气溶胶物质来源研究进展

大气气溶胶物质来源研究是大气污染研究极为重要的内容,它对污染物质的追踪评价具有较大的意义。本文较为系统地讨论了大气气溶胶物质来源研究的现状。从气溶胶的特征上分别论述气溶胶物质来源的矿物学（ 颗粒） 、无机化学和有机化学研究的进展。     

杭州市区降水酸度的初步分析

一、引言近数十年来,很多地区的降水酸度明显增加,其主要原因是由于燃烧化石燃料产生了硫和氮的氧化物,形成了呈酸性的大气污染物气溶胶。这些气溶胶粒子和其它物质会以各种方式改变降水的 pH 值,如二氧化硫、硫化氢能局部改变降水的化学性质。氮的氧化物可以转     

气流组织形式对室内微生物气溶胶的影响

为探明空调房间气流形式与通风量对室内微生物气溶胶的影响规律,在一个标准气流实验室,使用Andersen六级撞击式空气采样器对空气中的细菌与真菌气溶胶进行采样,分析了其浓度变化特点,及其与大气细颗粒物PM_(2.5)的相关关系。结果表明,晴朗天气下,气流室内不同气流形式和通风量对微生物气溶胶浓度的影响不同。总体来说,不管是哪种气流形式,通风量的增加均在一定范围内降低了室内微生物气溶胶及大气细颗粒物浓度,其中细菌气溶胶和PM_(2.5)在通风方式为侧面送风侧面排风时的去除效果最好,且分别在换气次数为3次/h和4次/h时其浓度达到最低,其去除效率分别为88.5%和42%,而真菌气溶胶在侧面送风顶面排风时的去除效果最好,在4次/h浓度最低,去除效率为6%。研究结果可以为探究室内环境空气质量及控制室内微生物污染提供基础数据。     

杭州市主城区大气颗粒物的酸缓冲能力及来源解析

通过酸缓冲能力的测定实验,研究杭州市主城区大气颗粒物的酸缓冲能力,并利用二重源解析技术,解析了大气颗粒物中碱性组分的来源.结果表明,杭州市主城区大气颗粒物呈弱碱性,对降水酸度有一定的缓冲作用,但作用较小.总体而言,TSP与PM10的酸缓冲能力与其浓度呈负相关,但相关关系不明显,TSP的酸缓冲能力比PM10强.Ca是影响大气颗粒物酸缓冲能力的关键化学组分.TSP的酸缓冲能力主要来自建筑水泥尘.     

Searching for evidence of acid-catalyzed enhancement of secondary organic aerosol formation using ambient aerosol data

Laboratory experiments suggest that strong acids promote formation of enhanced levels of secondary organic aerosol (SOA), and organic aerosols may contribute to the health impacts of fine PM. We report results from examining hourly speciated fine particle data for evidence of ambient aerosol acidity-catalyzed SOA formation, as indicated by larger increases in the concentrations of organic aerosol mass occurring on days and in locations where more acidic aerosol (lower NH₄⁺/SO₄⁼ molar ratios) exists. Data sets from the southeastern U.S. were examined for which hourly acidity of PM_2.5 aerosols could be estimated, and for which hourly organic carbon (OC) content had been measured simultaneously. Within-day organic aerosol changes during selected periods were statistically related to concurrent aerosol acidity levels estimated from nitrate-corrected ammonium-to-sulfate ratios. Data from the Look Rock, TN, TVA/IMPROVE site for mid-July to mid-August 2004 showed average compositions frequently as acidic as NH₄HSO₄, however, no apparent increases in OC levels with increasing aerosol acidity were observed, even when [OC] changes were compared with time-delayed aerosol acidity estimates. SEARCH network data (2003–2004) for rural Centreville, AL (CTR) and Yorkville, GA (YRK) sites were also examined. Warm-season acidity levels were higher at CTR than at YRK, and daytime levels exceeded those at night at both sites. At the YRK site no consistent positive correlations were found between changes in OC or TC levels and aerosol acidity, even with time lags up to 6 h. Aerosol acidity at this site, however, is relatively low due to nearby agricultural sources of NH₃. In contrast, during selected periods from April to October 2004, at CTR, 6-h lagged OC changes were weakly correlated with daytime, nitrate-corrected NH₄⁺/SO₄⁼ molar ratios, but distinguishing this apparent relationship from meteorological effects on measured OC levels is challenging.     

Formation of organic tracers for isoprene SOA under acidic conditions

The chemical compositions of a series of secondary organic aerosol (SOA) samples, formed by irradiating mixtures of isoprene and NO in a smog chamber in the absence or presence of acidic aerosols, were analyzed using derivatization-based GC–MS methods. In addition to the known isoprene photooxidation products 2-methylglyceric acid, 2-methylthreitol, and 2-methylerythritol, three other peaks of note were detected: one of these was consistent with a silylated-derivative of sulfuric acid, while the remaining two were other oxidized organic compounds detected only when acidic aerosol was present. These two oxidation products were also detected in field samples, and their presence was found to be dependent on both the apparent degree of aerosol acidity as well as the availability of isoprene aerosol. The average concentrations of the sum of these two compounds in the ambient PM_2.5 samples ranged from below the GC–MS detection limit during periods when the isoprene emission rate or apparent acidity were low to approximately 200 ng m^?3 (calibrations being based on a surrogate compound) during periods of high isoprene emissions. These compounds presently unidentified have the potential to serve as organic tracers of isoprene SOA formed exclusively in the presence of acidic aerosol and may also be useful in assessments in determining the importance and impact of aerosol acidity on ambient SOA formation.     

Effects of particle acidity and UV light on secondary organic aerosol formation from oxidation of aromatics in the absence of NOx

Recent laboratory observations have shown that particle acidity increases secondary organic aerosol (SOA) yields. However, these studies have mainly focused on biogenic precursors such as isoprene and terpenes. In this paper, the effects of particle acidity on the SOA yields from aromatic precursors under both dark and UV–visible light conditions were characterized through controlled chamber experiments. SOA was produced from oxidation of toluene and 1,3,5-trimethylbenzene (135-TMB) with OH radicals created by ozonolysis of 2-methyl-2-butene (MB). Particle acidity, described with proton concentrations, varied with inorganic seed aerosol composition and humidity (20–52%). Overall, in the presence of acidic seeds, greater increases in SOA yields were observed for the toluene system than the 135-TMB system. UV irradiation reduced SOA yields for both toluene and 135-TMB systems to different extents.     

Sources,distribution, and acidity of sulfate–ammonium aerosol in the Arctic in winter–spring

We use GEOS-Chem chemical transport model simulations of sulfate–ammonium aerosol data from the NASA ARCTAS and NOAA ARCPAC aircraft campaigns in the North American Arctic in April 2008, together with longer-term data from surface sites, to better understand aerosol sources in the Arctic in winter–spring and the implications for aerosol acidity. Arctic pollution is dominated by transport from mid-latitudes, and we test the relevant ammonia and sulfur dioxide emission inventories in the model by comparison with wet deposition flux data over the source continents. We find that a complicated mix of natural and anthropogenic sources with different vertical signatures is responsible for sulfate concentrations in the Arctic. East Asian pollution influence is weak in winter but becomes important in spring through transport in the free troposphere. European influence is important at all altitudes but never dominant. West Asia (non-Arctic Russia and Kazakhstan) is the largest contributor to Arctic sulfate in surface air in winter, reflecting a southward extension of the Arctic front over that region. Ammonium in Arctic spring mostly originates from anthropogenic sources in East Asia and Europe, with added contribution from boreal fires, resulting in a more neutralized aerosol in the free troposphere than at the surface. The ARCTAS and ARCPAC data indicate a median aerosol neutralization fraction [NH₄⁺]/(2[SO₄^2?] + [NO₃^?]) of 0.5 mol mol^?1 below 2 km and 0.7 mol mol^?1 above. We find that East Asian and European aerosol transported to the Arctic is mostly neutralized, whereas West Asian and North American aerosol is highly acidic. Growth of sulfur emissions in West Asia may be responsible for the observed increase in aerosol acidity at Barrow over the past decade. As global sulfur emissions decline over the next decades, increasing aerosol neutralization in the Arctic is expected, potentially accelerating Arctic warming through indirect radiative forcing and feedbacks.     

Dissolution of trace metals from lava ash: influence on the composition of rainwater in the Mount Etna volcanic area

Dissolution of trace metals from lava ash of the Mount Etna volcano in aqueous suspensions is studied as a function of solution pH and aerosol mass loading. The rate of dissolution and the final concentration increase with decreasing pH. Leaching experiments are found to be consistent with the observations of these metals in rainwater of the volcanic area. Elements such as Fe and Mn are important in the aqueous oxidation of SO(2) which increases the acidity of the rainwater. Leaching of Na, Ca, K, Fe and Mg may have a buffering effect in reacting with cloud and aerosol droplets.     

Aerosol ion characteristics during the Big Bend Regional Aerosol and Visibility Observational study

The ionic compositions of particulate matter with aerodynamic diameter < or = 2.5 microm (PM2.5) and size-resolved aerosol particles were measured in Big Bend National Park, Texas, during the 1999 Big Bend Regional Aerosol and Visibility Observational study. The ionic composition of PM2.5 aerosol was dominated by sulfate (SO4(2-)) and ammonium (NH4+). Daily average SO4(2-) and NH4+ concentrations were strongly correlated (R2 = 0.94). The molar ratio of NH4+ to SO4(2-) averaged 1.54, consistent with concurrent measurements of aerosol acidity. The aerosol was observed to be comprised of a submicron fine mode consisting primarily of ammoniated SO4(2-) and a coarse particle mode containing nitrate (NO3-). The NO3- appears to be primarily associated with sea salt particles where chloride has been replaced by NO3-, although formation of calcium nitrate (Ca(NO3)2) is important, too, on several days. Size-resolved aerosol composition results reveal that a size cut in particulate matter with aerodynamic diameter < or = 1 microm would have provided a much better separation of fine and coarse aerosol modes than the standard PM2.5 size cut utilized for the study. Although considerable nitric acid exists in the gas phase at Big Bend, the aerosol is sufficiently acidic and temperatures sufficiently high that even significant future reductions in PM2.5 SO4(2-) are unlikely to be offset by formation of particulate ammonium nitrate in summer or fall.     

Heterogeneous SOA yield from ozonolysis of monoterpenes in the presence of inorganic acid

The secondary organic aerosol (SOA) yield of a series of montoerpenes was investigated to determine the relative amounts of organic mass, which can be attributed to mass produced by heterogeneous acid-catalyzed reactions. Five monoterpenes (α-pinene, terpinolene, d-limonene, Δ²-carene, β-pinene) were studied using a 2 m³ indoor Teflon chamber and SOA was created in the presence of both acidic and neutral inorganic seed aerosol. The relative humidity was varied to create differing acidic seed environments. The heterogeneous aerosol production was influenced by the seed mass concentration, the acidity of the inorganic seed aerosol, and also molecular structure of the monoterpene ozonolysis products. This study also can be incorporated with our previously presented model of the kinetic expression for SOA mass production from heterogeneous acid-catalyzed reactions.     

Size distribution and sources of aerosol in Launceston, Australia, during winter 1997

As part of a pilot study into the chemical and physical properties of Australian fine particles, a suite of aerosol samples was collected at Ti Tree Bend in Launceston, Tasmania, during June and July 1997. This period represents midwinter in the Southern Hemisphere, a period when aerosol sources in Launceston are dominated by smoke from domestic wood burning. This paper describes the results from this measurement campaign, with the aim of assessing the effect of wood smoke on the chemical and physical characteristics of ambient aerosol. A micro orifice uniform deposit impactor (MOUDI) was used to measure the size distributions of the aerosol from 0.05 to 20 microns aerodynamic diameter. Continuous measurements of fine particle mass were made using a PM2.5 tapered element oscillating microbalance (TEOM) and light scattering coefficients at 530 nm were measured with nephelometers. Mass size distributions tended to be bimodal, with the diameter of the dominant mode tending to smaller sizes with increases in total mass. Non-sea salt potassium and polycyclic aromatic hydrocarbons (PAHs) were used as chemical tracers for wood smoke. Wood smoke was found to increase absolute particle mass (enough to regularly exceed air quality standards), and to concentrate mass in a single mode below 1 micron aerodynamic diameter. The acid-base equilibrium of the aerosol was altered by the wood smoke source, with free acidity hydrogen ion, non-sea salt sulfate, and ammonium concentrations being higher and the concentration of all species, including nitrate (to differing extents), focused in the fine particle size ranges. The wood smoke source also heavily influenced the aerosol scattering efficiency, adding to a strong diurnal cycle in both mass concentration and light scattering.     

Factors influencing aerosol solubility during cloud processes

The water-soluble fraction of an aerosol determines its chemical and physical properties and also its behaviour. The origin of the aerosol and its atmospheric transport influence its solubility. Cloud process simulations have been conducted on both Saharan and anthropogenic aerosols. The rate of solubilisation was followed for native and processed aerosol particles; it is controlled by the pH variations due to release of acids or bases. It appears that one condensation/evaporation cycle increases the solubility of aerosol particles. Increasing the number of cloud process simulations does not affect the solubility profile. The solubility depends only on the conditions of the last cloud cycle and, in particular, on the factor controlling pH during this process.     

A comparison of fine particle and aerosol strong acidity at the interface zone (1540 m) and within (452 m) the planetary boundary layer of the Great Gulf and Presidential-Dry River Class I Wildernesses on the Presidential Range,New Hampshire USA

Mount Washington, NH in the White Mountain National Forest, is flanked to the north-northeast and south by two Class I Wilderness areas, the Great Gulf and Presidential Range-Dry River Wildernesses, respectively. The Clean Air Act protects Class I Area natural resource values from air pollution. Aerosol sulfate, a fine particulate component that is often transported long distances, is a known contributor to visibility degradation and acidic deposition. We examined summertime fine particulate aerosol mass and sulfate, strong acidity and ammonium concentrations from 1988 to 2007 on Mount Washington at two elevations, 452 and 1540 m (msl). The former site is often within, and the latter at the interface of, the planetary boundary layer. Comparisons of sampling interval durations (10 and 24 h) and site vs. site are made. We also examine the extent to which aerosol sulfate is neutralized.Ten hour (daytime) compared to 24 h samples have higher mass and aerosol sulfate concentrations, however paired samples are well correlated. Fine mass concentrations compared between the 452 m and 1540 m sites (standard temperature and pressure corrected) show a weak positive linear relationship with the later being approximately 32% lower. We attribute the lack of a strong correlation to the facts that the 1540 m site is commonly at the interface of and even above the regional planetary boundary layer in summer and that it can intercept different air masses relative to the 452 m site. Sulfate is ～18% lower at the higher elevation site, but comprises a greater percentage of total fine mass; 42% compared to 37% for the high and low elevation site, respectively. Aerosol strong acidity was found to increase with increasing sulfate concentrations at both sites. Further the ratio of hydrogen to sulfate ion was greater in 24 h than 10 h samples at the higher elevation site likely due to overnight transport of fresh acidic aerosols.