Evaluation of the diffusion size classifier (meDiSC) for the real-time measurement of particle size and number concentration of nanoaerosols in the range 20-700 nm

In the frame of assessing exposure to nanostructured particles, the aim of this work is to study the performance of a new device devoted to the real-time measurement of nanostructured aerosol: the meDiSC (Diffusion Size Classifier, Matter Engineering, Switzerland). This instrument is based on unipolar diffusion charging of particles which are then collected successively in diffusion and filtration stages. From currents measured in these stages, the instrument is capable of determining aerosol mean size and number concentration. These data were compared to reference measurements regarding monodisperse aerosols in a range from 20 to 700 nm; the relative biases were found unsatisfying. This led us to investigate the principle of the instrument. Consequently, the charging law of the diffusion charger was experimentally established, as well as the calibration curve allowing the determination of the mean size of the particles. The latter analysis was completed by a model based on diffusion theory. Our results indicate the possibility to improve the range of size measurement up to 350 nm. Measured particle size and number concentration were also used to calculate geometric surface-area concentration; the experimental data were compared to a reference calculated surface-area concentration. The results demonstrate the possibility to evaluate this parameter within acceptable uncertainty. In a second step, the meDiSC was challenged with polydisperse aerosols. It was observed that meDiSC overestimates particle size by a factor 1.7, while particle number concentrations are found within ±40% of the reference. The model applied to polydisperse aerosols indicates that polydispersity little influences particle size up to 300 nm while geometric standard deviation remains below 1.7.     

Statistical methods to apportion the sources of particles in the industrial region of Estarreja—Portugal

Factor analysis models are very attractive for source apportionment and have been widely applied. They do not require a priori knowledge of the number and composition of the sources, and they can actually uncover previously unsuspected sources and estimate the composition of the sources using only ambient monitoring data.Aerosol particles were collected from an industrial atmosphere and analyses for water soluble and carbon components. Principal components analysis permitted the evaluation of the contribution due to industries, soil fraction, secondary pollutants and sea spray particles of the total suspended aerosol mass.It can be concluded that the atmospheric aerosol in the Industrial Area of Estarreja (Portugal) contains a relative important fraction that is water soluble. Ammonium sulphates and nitrates are the main components of this fraction. Carbon compounds constitute about 30% of the total aerosol mass. These compounds are mainly formed by organic matter emitted by the industries. Due to the mutagenic and carcinogenic characteristics of some organic compounds processed in the Industrial Area (vinyl chloride, benzene, aniline, etc.), the concern exists of negative human health effects as a result of prolonged inhalation. Soil compounds is another important fraction of the aerosol mass, mainly in summer with dry, sunny and windy weather conditions.A more conclusive idea of the sources and effects of aerosol matter can only be obtained with the specific analysis of organic compounds and the determination of trace elements, characteristic of each particular source.     

Study of odor compounds in gaseous effluents generated during production of poultry feather and viscera meal using headspace solid phase microextraction

This work reports the screening and characterization of odor compounds in gaseous effluents generated during the production of poultry feather and viscera meal, the by-products of the poultry meat industry. Chemical analysis was carried out by solid phase microextraction in the headspace (HS-SPME) mode. Exhaust air of thermal processing of poultry feather and viscera were sampled online from a bench-scale digester, condensed, and collected in sampling flasks. Both volatile and semivolatile organic compounds present in the condensed gases were extracted under agitation at constant temperature. The extracts were analyzed with a gas chromatograph coupled to a mass spectrometric detector (GC/MSD). The identification of compounds was carried out by comparing the mass spectra obtained with those from the Wiley library and quantification was accomplished through authentic analytical standards. For the determination of the best extraction conditions and analysis, extraction fibers of different coatings and polarities were tested: divinylbenzene/carboxen/polydimethyilsiloxane (DVB/CAR/PDMS), carbowax/divinylbenzene (CW/DVB), and polydimethylsiloxane (PDMS) and chromatography columns of different polarities: DB-WAX (polar) and DB-5 (nonpolar). The best extraction conditions and analysis of the compounds of interest were obtained by the use of the SPME fiber with DVB/CAR/PDMS coating and analysis by GC/MSD with polar capillary column. Several carboxylic acids were identified, as well as mercaptans, amines, and aldehydes of great environmental importance.     

Characteristics of black carbon aerosol mass concentration over the East Baltic region from two-year measurements

Continuous measurements of black carbon (BC) aerosol mass concentration were performed at a background site Preila (55°55'N, 21°00'E, 5 m a.s.l., Lithuania) during the period 2008-2009. The data were used to characterize the BC mass concentration distribution over the East Baltic region. High increase in aerosol BC concentration was associated with the change in air mass characteristics and biomass burning during the winter heating season and spring wildfires. Monthly means of BC concentration ranged from 212 to 1268 ng m(-3) and the highest hourly means of concentration were from 4800 to 6300 ng m(-3), predominantly in spring and winter months. During the October-April period the BC mass concentrations were about twice as high as those in the summertime. The BC diurnal pattern in winter was typically different from that in spring indicating the seasonal variation of the atmospheric boundary layer height. The weekday/weekend difference was not strongly pronounced because the BC concentrations in Preila are mainly affected by long-range transport or local sources. Typical periodicities caused by anthropogenic and meteorological influences have been identified using Fourier analysis. It was shown that domestic heating appears as a 365 day periodicity; traffic slightly contributes 5-7 day peaks in the spectrum and elevated long-range BC can be identified as characteristic peaks with periodicities in the range from 16 to 29 days.Temporal evolution and transport of BC aerosols were interpreted by the air mass backward trajectory analysis in conjunction with the examination of the wavelength dependence on the aethalometer data. Air masses originated from the North Atlantic Ocean and Scandinavia were favourable for lower BC concentrations (350 ng m(-3)), while the BC level associated with the Western Europe airflows was significantly higher (970 ng m(-3)). The mean values of ?ngstr?m exponent of the absorption coefficient (monthly means 1.45 ± 0.25 and 0.84 ± 0.50 over January and June, respectively) revealed that the BC concentration observed over the East Baltic is influenced by submicron sized particles as a result of incomplete biomass combustion during the winter season.     

Columnar aerosol optical and radiative properties according to season and air mass transport pattern over East Asia

The column-integrated optical and radiative properties of aerosols in the downwind area of East Asia were investigated based on sun/sky radiometer measurements performed from February 2004 to June 2005 at Gwangju (35.23° N, 126.84° E) and Anmyeon (36.54° N, 126.33° E), Korea. The observed aerosol data were analyzed for differences among three seasons: spring (March-May), summer (June-August), and autumn/winter (September-February). The data were also categorized into five types depending on the air mass origin in arriving in the measurement sites: (a) from a northerly direction in spring (S(N)), (b) from a westerly direction in spring (S(W)), (c) cases with a low ?ngstr?m exponent (<0.8) in spring (dust), (d) from a northerly direction in autumn/winter (AW(N)), and (e) from a westerly direction during other seasons (AW(W)). The highest ?ngstr?m exponents (α) at Gwangju and Anmyeon were 1.43?±?0.30 and 1.49?±?0.20, respectively, observed in summer. The lowest column-mean single-scattering albedo (ω) at 440 nm observed at Gwangju and Anmyeon were 0.89?±?0.02 and 0.88?±?0.02, respectively, during a period marked by the advection of dust from the Asian continent. The highest ω values at Gwangju and Anmyeon were 0.95?±?0.02 and 0.96?±?0.02, respectively, observed in summer. Variations in the aerosol radiative-forcing efficiency (β) were related to the conditions of the air mass origin. The forcing efficiency in summer was -131.7 and -125.6 W?m(-2) at the surface in Gwangju and Anmyeon, respectively. These values are lower than those under the atmospheric conditions of spring and autumn/winter. The highest forcing efficiencies in autumn/winter were -214.3 and -255.9 W?m(-2) at the surface in Gwangju and Anmyeon, respectively, when the air mass was transported from westerly directions.     

Assessment of particulate matter in the urban atmosphere: size distribution, metal composition and source characterization using principal component analysis

In this study, the size distribution of airborne particles and related heavy metals Co, Cd, Sn, Cu, Ni, Cr, Pb and V in two urban areas in Istanbul: Yenibosna and Goztepe, were examined. The different inhalable particles were collected by using a cascade impactor in eight size fractions (<0.4 μm, 0.4-0.7 μm, 1.1-2.1 μm, 2.1-3.3 μm, 3.3-4.7 μm, 4.7-5.8 μm, 5.8-9 μm and >9 μm) for six months at each station. Samples were collected on glass fiber filters and filters were extracted and analyzed using ICP-MS. Log-normal distributions showed that the particles collected at the Yenibosna site have a smaller size compared to the Goztepe samples and the size distribution of PM was represented the best by the tri-modal. The average total particle concentrations and standard deviations were obtained as 67.7 ± 17.0 μg m(-3) and 82.1 ± 21.2 μg m(-3), at the Yenibosna and G?ztepe sites, respectively. The higher metal rate in fine and medium coarse PM showed that the anthropogenic sources were the most significant pollutant source. Principal component analysis identified five components for PM namely traffic, road dust, coal and fuel oil combustion, and industrial.     

Workplace aerosol mass concentration measurement using optical particle counters

Direct-reading aerosol measurement usually uses the optical properties of airborne particles to detect and measure particle concentration. In the case of occupational hygiene, mass concentration measurement is often required. Two aerosol monitoring methods are based on the principle of light scattering: optical particle counting (OPC) and photometry. The former analyses the light scattered by a single particle, the latter by a cloud of particles. Both methods need calibration to transform the quantity of scattered light detected into particle concentration. Photometers are simpler to use and can be directly calibrated to measure mass concentration. However, their response varies not only with aerosol concentration but also with particle size distribution, which frequently contributes to biased measurement. Optical particle counters directly measure the particle number concentration and particle size that allows assessment of the particle mass provided the particles are spherical and of known density. An integrating algorithm is used to calculate the mass concentration of any conventional health-related aerosol fraction. The concentrations calculated thus have been compared with simultaneous measurements by conventional gravimetric sampling to check the possibility of field OPC calibration with real workplace aerosols with a view to further monitoring particle mass concentration. Aerosol concentrations were measured in the food industry using the OPC GRIMM? 1.108 and the CIP 10-Inhalable and CIP 10-Respirable (ARELCO?) aerosol samplers while meat sausages were being brushed and coated with calcium carbonate. Previously, the original OPC inlet had been adapted to sample inhalable aerosol. A mixed aerosol of calcium carbonate and fungi spores was present in the workplace. The OPC particle-size distribution and an estimated average particle density of both aerosol components were used to calculate the mass concentration. The inhalable and respirable aerosol fractions calculated from the OPC data are closely correlated with the results of the particle size-selective sampling using the CIP 10. Furthermore, the OPC data allow calculation of the thoracic fraction of workplace aerosol (not measured by sampling), which is interesting in the presence of allergenic particles like fungi spores. The results also show that the modified COP inlet adequately samples inhalable aerosol in the range of workplace particle-size distribution.     

Qualitative Study of Organic Compounds in Wastewaters of a Swine Slaughterhouse

The main purpose of this work was the preliminary qualitative study of organic compounds in wastewaters of swine slaughterhouses. The samples were collected in a local abattoir and submitted to Liquid-Liquid Extraction (LLE) and Solid-phase Extraction (SPE) with XAD-4^TM resin as stationary phase. The instrumental analysis was performed by Gas Chromatography with Mass Spectrometer Detector (GC/MSD). The compounds present in the LLE and SPE extracts were identified by the GC/MSD library (Wiley). The results pointed out that SPE and LLE can extract practically the same classes of compounds at the same amounts. LLE works well for the extraction of polar organic compounds, with acidified samples, while SPE presents a better performance for the extraction of less polar organic compounds. Aldehydes were main class of the compounds extracted by SPE and LLE and decenal was the major aldehyde identified. Fatty alcohols and carboxylic acids were also identified but in minor proportions.     

Traffic emission factors of ultrafine particles: effects from ambient air

Ultrafine particles have a significant detrimental effect on both human health and climate. In order to abate this problem, it is necessary to identify the sources of ultrafine particles. A parameterisation method is presented for estimating the levels of traffic-emitted ultrafine particles in terms of variables describing the ambient conditions. The method is versatile and could easily be applied to similar datasets in other environments. The data used were collected during a four-week period in February 2005, in Gothenburg, as part of the G?te-2005 campaign. The specific variables tested were temperature (T), relative humidity (RH), carbon monoxide concentration (CO), and the concentration of particles up to 10 μm diameter (PM(10)); all indicators are of importance for aerosol processes such as coagulation and gas-particle partitioning. These variables were selected because of their direct effect on aerosol processes (T and RH) or as proxies for aerosol surface area (CO and PM(10)) and because of their availability in local monitoring programmes, increasing the usability of the parameterization. Emission factors are presented for 10-100 nm particles (ultrafine particles; EF(ufp)), for 10-40 nm particles (EF(10-40)), and for 40-100 nm particles (EF(40-100)). For EF(40-100) no effect of ambient conditions was found. The emission factor equations are calculated based on an emission factor for NO(x) of 1 g km(-1), thus the particle emission factors are easily expressed in units of particles per gram of NO(x) emitted. For 10-100 nm particles the emission factor is EF(ufp) = 1.8×10(15)×(1 - 0.095×CO - 3.2×10(-3)×T) particles km(-1). Alternative equations for the EFs in terms of T and PM(10) concentration are also presented.     

Analysis of crystalline phases in airborne particulate matter by two-dimensional X-ray diffraction (XRD2)

In this work, the potentiality of two-dimensional X-ray diffraction (XRD(2)) to characterise aerosol particles collected on commercial glass filters is presented. Indeed, even if routine analysis usually requires only mass determination, and rarely chemical composition, phase determination is fundamental to recognize the primary or secondary origin of the particulate matter and thus to determine the main sources of the pollution and to model contamination events. The experiments were performed at Daresbury Synchrotron (UK) Laboratory on 14.1 Beamline. The analysis of filters collected in Tuscany (Italy) is discussed with particular attention to the presence of arsenic sulfide. The first results of these experiments are very promising, showing the presence of unexpected compounds in the particulate matter of the investigated area.     

Classification of particles from the farm environment by automated sizing, counting and chemical characterisation with scanning electron microscopy-energy dispersive spectroscopy

About 60,000 particles in 288 aerosol samples collected during farm work have been characterised with automated particle analysis using scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS). Based on EDS-analysis of materials with known composition (potato flour, alpha-quartz, K-feldspar and beta-wollastonite), criteria were developed for classification of particles as: (1) organic, (2) silicon-rich (silica), and (3) other inorganic particles. The reproducibility of the relative mass proportions in dust samples collected during farm work was 0.078 when approximately 200 particles were characterised per sample. Field samples from the farm environment showed clear differences in composition. Generally, inorganic particles dominated the particle mass. The proportion of the organic particle mass was highest for tending of swine and poultry, 55 and 38% respectively. Silica particles amounted to 10 to 20% of the total mass during handling crops, e.g. grain, straw, hay, potatoes, and onions. It seems likely that the results can be used in etiologic studies, but further validation would be needed for quantitative purposes.     

Correlations in the chemical composition of rural background atmospheric aerosol in the UK determined in real time using time-of-flight mass spectrometry

An aerosol time-of-flight mass spectrometer (ATOFMS) was used to determine, in real time, the size and chemical composition of individual particles in the atmosphere at the remote inland site of Eskdalemuir, Scotland. A total of 51,980 particles, in the size range 0.3-7.4 microm, were detected between the 25th and 30th June 2001. Rapid changes in the number density, size and chemical composition of the atmospheric aerosol were observed. These changes are attributed to two distinct types of air mass; a polluted air mass that had passed over the British mainland before reaching Eskdalemuir, interposed between two cleaner air masses that had arrived directly from the sea. Such changes in the background aerosol could clearly be very important to studies of urban aerosols and attempts at source apportionment. The results of an objective method of data analysis are presented. Correlations were sought between the occurrence of: lithium, potassium, rubidium, caesium, beryllium, strontium, barium, ammonium, amines, nitrate, nitrite, boron, mercury, sulfate, phosphate, fluorine, chlorine, bromine, iodine and carbon (both elemental and organic hydrocarbon) in both fine (d < 2.5 microm) and coarse (d > 2.5 microm) particle fractions. Several previously unreported correlations were observed, for instance between the elements lithium, beryllium and boron. The results suggest that about 2 in 3 of all fine particles (by number rather than by mass), and 1 in 2 of all coarse particles containing carbon, consisted of elemental carbon rather than organic hydrocarbon (although a bias in the sensitivity of the ATOFMS could have affected these numbers). The ratio of the number of coarse particles containing nitrate anions to the number of particles containing chloride anions exceeded unity when the air mass had travelled over the British mainland. The analysis also illustrates that an air mass of marine origin that had travelled slowly over agricultural land can accumulate amines and ammonium.     

Evaluation of the effect of different sampling time periods and ambient air pollutant concentrations on the performance of the Radiello diffusive sampler for the analysis of VOCs by TD-GC/MS

The effect of different sampling exposure times and ambient air pollutant concentrations on the performance of Radiello? samplers for analysis of volatile organic compounds (VOCs) is evaluated. Quadruplicate samples of Radiello? passive tubes were taken for 3, 4, 7 and 14 days. Samples were taken indoors during February and March 2010 and outdoors during July 2010 in La Canonja (Tarragona, Spain). The analysis was performed by automatic thermal desorption (ATD) coupled with capillary gas chromatography (GC)/mass spectrometry detection (MS). The results show significant differences (t-test, p < 0.05) between the amounts of VOCs obtained from the sum of two short sampling periods and a single equivalent longer sampling period for 65% of all the data. 17% of the results show significantly larger amounts of pollutant in the sum of two short sampling periods. Back diffusion due to changes in concentrations together with saturation and competitive effects between the compounds during longer sampling periods could be responsible for these differences. The other 48% of the results that are different show significantly larger amounts in the single equivalent longer sampling period. The remaining 35% of the results do not show significant differences. Although significant differences are observed in the amount of several VOCs collected over two shorter sampling intervals compared to the amount collected during a single equivalent longer sampling period, the ratios obtained are very close to unity (between 0.7 and 1.2 in 75% of cases). We conclude that Radiello? passive samplers are useful tools if their limitations are taken into account and the manufacturer's recommendations are followed.     

Characteristics of aerosol types during large-scale transport of air pollution over the Yellow Sea region and at Cheongwon,Korea, in 2008

Episodes of large-scale transport of airborne dust and anthropogenic pollutant particles from different sources in the East Asian continent in 2008 were identified by National Oceanic and Atmospheric Administration satellite RGB (red, green, and blue)-composite images and the mass concentrations of ground level particulate matter. These particles were divided into dust, sea salt, smoke plume, and sulfate by an aerosol classification algorithm. To analyze the aerosol size distribution during large-scale transport of atmospheric aerosols, aerosol optical depth (AOD) and fine aerosol weighting (FW) of moderate imaging spectroradiometer aerosol products were used over the East Asian region. Six episodes of massive airborne dust particles, originating from sandstorms in northern China, Mongolia, and the Loess Plateau of China, were observed at Cheongwon. Classified dust aerosol types were distributed on a large-scale over the Yellow Sea region. The average PM10 and PM2.5 ratio to the total mass concentration TSP were 70% and 15%, respectively. However, the mass concentration of PM2.5 among TSP increased to as high as 23% in an episode where dust traveled in by way of an industrial area in eastern China. In the other five episodes of anthropogenic pollutant particles that flowed into the Korean Peninsula from eastern China, the anthropogenic pollutant particles were largely detected in the form of smoke over the Yellow Sea region. The average PM10 and PM2.5 ratios to TSP were 82% and 65%, respectively. The ratio of PM2.5 mass concentrations among TSP varied significantly depending on the origin and pathway of the airborne dust particles. The average AOD for the large-scale transport of anthropogenic pollutant particles in the East Asian region was measured to be 0.42 ± 0.17, which is higher in terms of the rate against atmospheric aerosols as compared with the AOD (0.36 ± 0.13) for airborne dust particles with sandstorms. In particular, the region ranging from eastern China, the Yellow Sea, and the Korean Peninsula to the Korea East Sea was characterized by high AOD distributions. In the episode of anthropogenic polluted aerosols, FW averaged 0.63 ± 0.16, a value higher than that in the episode of airborne dust particles (0.52 ± 0.13) with sandstorms, showing that fine anthropogenic pollutant particles contribute greatly to atmospheric aerosols in East Asia.     

植物油烟组分的色质联机分析

将植物油烟采集在玻璃纤维滤筒中 ,用环己烷处理样品 ,样品经过净化处理 ,然后进行色质联机分析。对油烟化学成分的分析有助于人们研究油烟对人体健康的影响     

Metallic components of traffic-induced urban aerosol, their spatial variation, and source apportionment

This study proposes a practical method to estimate elemental composition and distribution in order to attribute source and quantify impacts of aerosol particles at an urban region in Kolkata, India. Twelve-hour total particulates were collected in winter (2005–2006) and analyzed by energy-dispersive X-ray fluorescence technique to determine multi-elemental composition, especially trace metals. The aerosols consist of various elements including K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Se, and Pb which exhibit significant concentration at various sites (p?<?0.05). The concentration of different metallic elements were found in the order of Zn ?> ?Pb ?> ?Ni ?> ?Cu ?> ?Cr ?>? Co. Statistical multivariate analysis and correlation matrix analyses were performed for factor identification and consequent source apportionment. Contour profiles demonstrate spatial variation of elemental compositions indicating possible source contribution along with meteorological influences. Spatial differences were clearly most significant for Zn, Ni, Pb, and Cu reflecting the importance of anthropogenic inputs, primarily from automobile sources.     

Characterization of airborne particles at a high-btu coal-gasification pilot plant

Airborne particles in fugitive emissions have been measured at a slagging fixed-bed coal-gasification pilot plant using lignite. Sampling was conducted during shutdown operations and opening of the gasifier following an aborted startup. Aerosol collected with a Sierra high-volume impactor was subjected to analysis by gas chromatography, mass spectrometry, and scanning electron microscopy; aerosol collected with an Andersen low-volume impactor was subjected to flameless atomic absorption analysis. The data show that the bulk of the trace organic material is associated with small particles: these data are similar to data on ambient air reported in the literature. Particle morphologies resemble those of fly ash from coal combustion, including smooth spheres, vesicular spheres, and crystalline material. Trace element size distributions are bimodal and resemble data for ambient air. Pb-containing particles are generally submicron, while particles containing Al, Fe, and other crustal species are mostly of supermicron size. Aluminum-based aerosol enrichment factors calculated from the lignite composition show that the composition of the aerosol resembles that of the coal, with the exception of modest enrichments of Mg, Na, As, and Pb in the submicron size range. Aerosol enrichment factors based on the earth's crustal composition are somewhat greater than those based on coal composition for several elements, suggesting potential errors in using crustal enrichment data to investigate chemical fractionation during aerosol formation.     

Seasonal Variation of the Particle Size Distribution of n-Alkanes and Polycyclic Aromatic Hydrocarbons (PAHs) in Urban Aerosol of Guangzhou, China

Seasonal aerosol samples have been collected by Andersen Hi-Vol pumping system equipped with a five stage cascade impactor and a backup filter (size range: 10–7.2 μ m, 7.2–3.0 μ m, 3.0–1.5 μ m, 1.5–0.95 μ m, 0.95–0.49 μ m, ≤0.49 μ m) in the Liwan district, Guangzhou. n-Alkanes were measured using gas chromatography and PAHs were measured using gas chromatography/mass spectrometry analysis. The bimodal log-normal distributions of n-alkanes and semi-volatile PAHs were found, while for non-volatile PAHs that was unimodal, so much as the mode of semi-volatile PAHs was similar with that of the particles. The n-alkanes and PAHs were preferably associated with fine particles. C _max (carbon number maximum) (C₂₂–C₂₆), CPI (carbon preference index) (1.12–1.21), U/R (unresolved to resolved components ratio) (7.42–10.7), wax% (0.9–3.12%) and the diagnostic ratios for PAHs revealed that vehicular emission was the major source of these organic compounds during the study periods, while the contribution of epicuticular waxes emitted by terrestrial plants was minor. CPI₂ (values for petrogenic hydrocarbons), CPI₃ (values for biogenic n-alkanes) and wax% revealed that the natural preferentially accumulated in the larger aerosol while the anthropogenic in the smaller. In addition, the different MMDs (mass median diameters) for n-alkanes and PAHs were observed in different seasons. The MMDs for n-alkanes and PAHs were higher in autumn/winter than those in spring/summer. The seasonal effect was related to the hydrocarbon content in the individual particulate fractions, showing a preferential association of n-alkanes and PAHs with larger particles in the autumn/winter season.     

4-hours resolution data to study PM10 in a “hot spot” area in Europe

Nowadays, high-time resolved aerosol studies are mandatory to better understand atmospheric processes, such as formation, removal, transport, deposition or chemical reactions. This work focuses on PM10 physical and chemical characterisation with high-time resolution: elements (from Na to Pb), ions and OC/EC fractions concentration were determined during two weeks in summer and two in winter 2006 with 4-hours resolution. Further measurements aimed at hourly elemental characterisation of fine and coarse fractions and at the determination of particles number concentration in the 0.25-32 microm size range in 31 bins. The chemical mass closure was carried out in both seasons, enhancing intra-day differences in PM10 composition. In Milan, the highest contribution came from organic matter (34% and 33% in summer and winter, respectively); other important contributors were secondary inorganic compounds (16% and 24% in summer and winter, respectively) and, in summer, crustal matter (14%). Temporal trends showed strong variations in PM10 composition during contiguous time-slots and diurnal variations in different components contribution were identified. Moreover, peculiar phenomena, which would have hardly been detected with 24-hours samplings, were evidenced. Particles removal due to precipitations, aerosol local production and long range transport were studied in detail.     

武汉地区沙尘天气气溶胶粒径分布特性研究

通过利用湖北省大气复合污染自动监控预警中心的振荡天平法颗粒物监测仪、光散射法气溶胶粒径谱仪,对武汉地区一次典型沙尘天气过程中记录的不同粒径气溶胶颗粒数量浓度、相对质量浓度进行研究。结果表明,在武汉地区沙尘天气过程中,粗颗粒显著增多,而细颗粒显著减少,这与部分研究发现的沙尘天气过程中粗颗粒与细颗粒共同显著增多的结论有所不同。粒径谱仪分析显示,大于PM5颗粒的增多对粗颗粒浓度增加有显著贡献,而小于PM0.5颗粒的减少则对细颗粒浓度降低有主要贡献,这可能是武汉地区沙尘天气过程颗粒物的变化特点。