Fine Aerosol Fraction Research Articles

Exposure to mineral sands dust particles

The aim of this study is to characterize the airborne particles in a Brazilian region with high concentration of mineral sands (Buena village). In this study proton induced X-ray emission (PIXE), plasma desorption mass spectrometry and alpha spectrometry were used for analyses of airborne particles. The analyses of aerosol samples and lichen samples show that the inhabitants of the Buena village are exposed to airborne particles in the fine fraction of aerosols. The main anthropogenic sources of particles are the mineral sands processing plant and truck traffic, and natural sources as the sea, soil and the swamp. The results from the lichen samples show that at least during the last 15 years the inhabitants of the village have been exposed to monazite particles. The results from aerosols and lichens samples also suggested that the swamp is a source of 226Ra and 210Pb bearing particles besides the monazite dust.

Organic compounds present in the natural Amazonian aerosol: Characterization by gas chromatography–mass spectrometry

As part of the Large‐Scale Biosphere‐Atmosphere Experiment in Amazonia (LBA)‐Cooperative LBA Airborne Regional Experiment (CLAIRE) 2001 campaign in July 2001, separate day and nighttime aerosol samples were collected at a ground‐based site in Amazonia, Brazil, in order to examine the composition and temporal variability of the natural “background” aerosol. We used a high‐volume sampler to separate the aerosol into fine (aerodynamic diameter, AD < 2.5 μm) and coarse (AD > 2.5 μm) size fractions and quantified a range of organic compounds in methanolic extracts of the samples by a gas chromatographic‐mass spectrometric technique. The carbon fraction of the compounds could account for an average of 7% of the organic carbon (OC) in both the fine and coarse aerosol fractions. We observed the highest concentrations of sugars, sugar alcohols, and fatty acids in the coarse aerosol samples, which suggests that these compounds are associated with primary biological aerosol particles (PBAP) observed in the forest atmosphere. Of these, trehalose, mannitol, arabitol, and the fatty acids were found to be more prevalent at night, coinciding with a nocturnal increase in PBAP in the 2–10 μm size range (predominantly yeasts and other small fungal spores). In contrast, glucose, fructose, and sucrose showed persistently higher daytime concentrations, coinciding with a daytime increase in large fungal spores, fern spores, pollen grains, and, to a lesser extent, plant fragments (generally >20 μm in diameter), probably driven by lowered relative humidity and enhanced wind speeds/convective activity during the day. For the fine aerosol samples a series of dicarboxylic and hydroxyacids were detected with persistently higher daytime concentrations, suggesting that photochemical production of a secondary organic aerosol from biogenic volatile organic compounds may have made a significant contribution to the fine aerosol. Anhydrosugars (levoglucosan, mannosan, galactosan), which are specific tracers for biomass burning, were detected only at low levels in the fine aerosol samples. On the basis of the levoglucosan‐to‐OC emission ratio measured for biomass burning aerosol, we estimate that an average of ∼16% of the OC in the fine aerosol was due to biomass burning during CLAIRE 2001, indicating that the major fraction was associated with biogenic particles.

Size distribution of acidic sulfate ions in fine ambient particulate matter and assessment of source region effect

Human exposure studies strongly suggested that the fine fraction of ambient particulate matter (PM) and its associated acidic sulfates are closely correlated with observed adverse health effects. Acidic sulfates are the products of atmospheric sulfur dioxide oxidation and neutralization processes. Few data are available on the amount and size distribution of acidic sulfates within the fine fraction of ambient PM. Knowledge of this distribution will help to understand their toxic mechanisms in the human respiratory tract. The goals of this research were: (1) to measure the size distribution of hydrogen ion, sulfate, and ammonium within the fine fraction of the ambient aerosol in air masses originating from different source regions; and (2) to examine the effect of the source region and the seasons on the sampled PM composition. Six size fractions within the fine ambient PM were collected using a micro-orifice impactor. Results from 30 sampling sessions demonstrated that higher total concentrations of these three ions were observed during the warm months than during the cold months of the year. Size distribution results show that the midpoint diameter of the fraction of particles with the largest fraction of hydrogen, sulfate and ammonium ions was 0.38 μm. Although most of the mass containing hydrogen and sulfate ions was measured in the fraction of particles with 0.38 μm midpoint diameter, the ultrafine fraction (<0.1 μm) was found to be more acidic. Ambient ion concentrations varied between sampling sessions and seasons, but the overall size distribution profiles are similar. Air mass back trajectories were used to identify the source region of the sampled aerosols. No apparent source region effect was observed in terms of the distribution profile of the ions. However, samples collected from air masses that originated from, or passed over, high sulfur dioxide emission areas demonstrated higher concentrations of the different ions.

Chemical characterization of ambient aerosol collected during the northeast monsoon season over the Arabian Sea: Labile‐Fe(II) and other trace metals

Ambient aerosol samples were collected over the Arabian Sea during the month of March of 1997, aboard the German R/V Sonne, as part of the German Joint Global Ocean Flux Study (JGOFS) project. This is the third study in a series of analogous measurements taken over the Arabian Sea during different seasons of the monsoon. Dichotomous high‐volume collector samples were analyzed for ferrous iron immediately after collection, while trace metals, anions, and cations were determined upon return to the laboratory. The main crustal component was geochemically well represented by the average crustal composition and amounted to 5.94 ± 3.08 μg m−3. An additional crustal constituent of clay‐like character, rich in water‐soluble Ca and Mg, was seen in the fine fraction in air masses of Arabian origin. Total ferrous iron concentrations varied from 3.9 to 17.2 ng m−3 and averaged 9.8 ± 3.4 ng m−3, with 87.2% of Fe(II) present in the fine aerosol fraction. Fe(II) concentrations accounted for on average 1.3 ± 0.5% of the total Fe. While ferrous iron in the coarse fraction appeared to be correlated with the main crustal component, the fine Fe(II) fraction exhibited a more complex behavior. The anthropogenic contribution to the aerosol, as traced by Pb, Zn, and some anions and cations, was found to be considerably larger, especially during the first 10 days of this cruise, than in previously collected samples from the inter‐monsoon and southwest monsoon of 1995.

Trace metals in the aerosol of the Logoon of Venice

Measurements of metal concentrations in the aerosols were carried out to highlight the importance of this contribution to contamination of the lagoon of Venice. Aerosol samples were collected by high-volume impactors fitted with PM 10 size selective inlets. Particles with aerodynamic diameters<10 μm were classified into six size intervals with cutoff aerodynamic diameters of 72.3. 1.5, 0.95, 0.49 and <0.49 μm. Samples were collected at four stations selecting the wind speed and the direction to characterise aerosols derived from the principal contaminant sources of the Venice Lagoon. Aerosol samples were analysed by ICP-SF-MS to determine the concentration of Li, Pb, U, Cd, Al, V, Mn, Fe, Cu, Zn and Co. The preliminary results obtained show that the elements with clear anthropogenic origin (in particular V and Pb) had a higher concentration in the fine fraction of aerosol, while other elements such as Mn and Fe showed higher concentrations at all sites with a bimodal distribution due to the crustal origin of these elements. On the basis of granulometric distribution of metals for the four sampling sites we can hypothesize that long range transport of contaminants can significantly contribute to the pollution of the Lagoon of Venice.

Aerosol time‐of‐flight mass spectrometry during the Atlanta Supersite Experiment: 1. Measurements

In August 1999 an intensive field campaign was conducted in Atlanta, Georgia, focusing on the characterization of urban particulate matter. During the study an aerosol time‐of‐flight mass spectrometer (ATOFMS) was used to measure continuously the aerodynamic size and chemical composition of individual particles in the fine fraction (0.2–2.5 μm) of the atmospheric aerosol. The inorganic and organic components of the particles were analyzed using laser desorption ionization time‐of‐flight mass spectrometry, generating positive and/or negative ion mass spectra. Here an overview of the ATOFMS results is presented with respect to the major species detected, including sodium, carbon (EC, OC, EC/OC), dust (Li, Na, Al, K, Ca, Fe), sulfate, nitrate, and ammonium. As described, many of the dust particle types have similar composition to those observed in ATOFMS coal source characterization studies. The ion signals, size distributions, and temporal evolution (30–60 min resolution) of the different particle types are described. The complexity of the Atlanta aerosol is shown here on an individual particle basis, demonstrating how single particle data obtained with ATOFMS can be used to gain unique insights into the mixing state of urban aerosols. The second paper in this two part series focuses on the scaling procedures used for converting the unscaled ATOFMS data presented in this paper into atmospherically representative number concentrations [Wenzel et al., 2002].

Seasonal variation of water‐soluble ions of the aerosol at the high‐alpine site Jungfraujoch (3580 m asl)

Within the Global Atmosphere Watch (GAW) Aerosol Program of the World Meteorological Organization (WMO), the aerosol chemical composition has been continuously measured since July 1999 at the Jungfraujoch (JFJ) of which the first 1.5‐year data set is presented. Sampling is performed in two size classes (total suspended particles (TSP) and particles with aerodynamic diameters smaller than 1 μm). The filters are analyzed for major ions, which constitute 30% of the total dry aerosol mass collected at this site. As annual mean, a total ion mass concentration of 1.04 μg m−3 was observed. Sulfate, ammonium, and nitrate were the major components of the fine aerosol fraction, while calcium and nitrate were two major water‐soluble components in the coarse mode. Single particle analysis confirmed the internal mixture of calcium and nitrate in the coarse mode. The total ion mass concentration showed strong seasonal differences, with 1.25, 1.62, 0.70, and 0.25 μg m−3 for spring, summer, fall, and winter, respectively. The variability was stronger for sulfate, ammonium, and nitrate than for calcium. The reason for this is believed to be local sources of calcium, which do not require vertical transport, along with Sahara dust episodes, which occur occasionally over the whole year, independent from the season.

Atmospheric Aerosol Optical Properties in the Persian Gulf

Aerosol optical depth measurements over Bahrain acquired through the ground-based Aerosol Robotic Network (AERONET) are analyzed. Optical depths obtained from ground-based sun/sky radiometers showed a pronounced temporal trend, with a maximum dust aerosol loading observed during the March-July period. The aerosol optical depth probability distribution is rather narrow with a modal value of about 0.25. The Angstrom parameter frequency distribution has two peaks. One peak around 0.7 characterizes a situation when dust aerosol is more dominant, the second peak around 1.2 corresponds to relatively dust-free cases. The correlation between aerosol optical depth and water vapor content in the total atmospheric column is strong (correlation coefficient of 0.82) when dust aerosol is almost absent (Angstrom parameter is greater than 0.7), suggesting possible hygroscopic growth of fine mode particles or source region correlation, and much weaker (correlation coefficient of 0.45) in the presence of dust (Angstrom parameter is less than 0.7). Diurnal variations of the aerosol optical depth and precipitable water were insignificant. Angstrom parameter diurnal variability (;20%-25%) is evident during the April-May period, when dust dominated the atmospheric optical conditions. Variations in the aerosol volume size distributions retrieved from spectral sun and sky radiance data are mainly associated with the changes in the concentration of the coarse aerosol fraction (variation coefficient of 61%). Geometric mean radii for the fine and coarse aerosol fractions are 0.14 mm (std dev 5 0.02) and 2.57 mm (std dev 5 0.27), respectively. The geometric standard deviation of each fraction is 0.41 and 0.73, respectively. In dust-free conditions the single scattering albedo (SSA) decreases with wavelength, while in the presence of dust the SSA either stays neutral or increases slightly with wavelength. The changes in the Angstrom parameter derived from a ground-based nephelometer and a collocated sun photometer during the initial checkout period were quite similar.

STUDY OF WORKER'S EXPOSURE TO THORIUM, URANIUM AND NIOBIUM MINERAL DUST

The aim of this study is to evaluate worker’s exposure to particles, with special attention to thorium, uranium and niobiumbearing particles. A cascade impactor (CI) with six stages was used to collect particles with aerodynamic diameter in the rangeof 0.64 to 19.4 μm. The elemental mass concentrations impacted in each stage of the CI were determined using the PIXE(Particle Induced X-ray Emission) technique. The Mass Median Aerodynamic Diameter (MMAD) and elemental mass concentration in the fine fraction of aerosol (0.5 to 2.5 μm) were determined.Personal air samplers were used by workers to collect fine particles of aerosol. The concentrations of 232Th and 228Th in these air samplers were measured by the alpha spectrometry technique. Faeces and urine samples from the workersand their wives were analyzed to determine the thorium, uranium and niobium mass concentration (mass spectrometry) and 232Th, 228Th, 238U and 234U concentrations (α spectrometry) and then compared to inhabitants of regions with low metal concentrations. The analysis of thefaecesand urine samples from workers and their wives indicated that themain pathway of thorium, uranium and niobium incorporation was byingestion. The observed concentrations of niobium and uranium inurine samples from workers showed a systemic incorporation of niobium and uranium.

Constructing the European aerosol nitrate concentration field from quality analysed data

We report on the construction of the aerosol nitrate concentration field in Europe from an interpolation of data. The first step was an active search for and a subsequent quality assessment of the (long term) data for this semi-volatile component, which is subject to a range of artefacts during sampling. Therefore first an overview of (filter) sampling methods in use in Europe and the associated sampling artefacts are presented. Denuder filter pack combinations have very minor artefacts and data obtained with this technique are therefore used as the starting point. Because of the paucity of data from these devices, values obtained with simple filter sampling were also considered after a critical analysis. We found that the largest artefact associated with inert filters (IF) (Teflon and Quartz) is evaporation of ammonium nitrate. Hence, concentrations obtained with the use of IF are lower values. Next, data from “total nitrate” filters were evaluated. Such filters collect both aerosol nitrate and nitric acid gas and the contribution of the gaseous compound was corrected for. The distances over which nitrate concentrations correlate was then analysed and it was found that in the winter half-year the correlation length was sufficiently long to warrant interpolation of the point data. The nitrate concentration field as obtained from interpolation of nitrate data in the period 1994–1997 was validated with intermediate point data from shorter lasting campaigns. The field has a large area of high nitrate concentrations ranging from southern England over continental western Europe into Poland, with concentrations of nitrate exceeding 5 μg m −3. Strong arguments are provided that the nitrate is predominantly present in the fine aerosol fraction (PM2.5). To the north nitrate concentrations range from 2.5 μg m −3 in southern Sweden to <0.5 μg m −3 in mid-Scandinavia. To the east and west of the central European maximum the nitrate concentration trails off in a more gradual way . It was inferred that the concentration of nitrate in winter in Europe north of the Alps, with the exception of France from which country no data could be found, is 60% or more of that of sulphate. It should further be mentioned that in the Po-Valley ammonium nitrate levels are as high as those in western Europe.

Composition and sources of aerosol in a central African rain forest during the dry season

During the Experiment for Regional Sources and Sinks of Oxidants (EXPRESSO‐96), size‐fractionated aerosol samples were collected in November and December 1996 at a ground site in the tropical rain forest at the N'doki National Park (NNP) in the Republic of Congo. The samples were analyzed for up to 26 elements using particle‐induced X‐ray emission. Elements related to mineral dust and pyrogenic aerosol exhibited greater concentrations during the daytime, while aerosol produced by the rain forest exhibited higher concentrations at night. Samples were also collected at two levels on the tower, above and below the canopy, to characterize vegetation sources. Absolute principal component analysis (APCA) identified three major aerosol source types in each size fraction, which explained more than 90% of the data variance. The fine‐size fraction contained mineral dust (Al, Si, Ca, Ti, and Fe), pyrogenic (black carbon, K, and Zn), and marine/anthropogenic sulfur components. The coarse‐size fraction included a mineral dust (Al, Si, Ca, Ti, Mn, and Fe) and two primary biogenic components consisting of K, P, Zn, and S. Absolute principal component scores were calculated for the components of APCA, and temporal trends were compared to 7 day isopycnic backward trajectories. Consistent relationships between the temporal trends of the fine fraction aerosol components and meteorological patterns were observed. Trade wind air masses transported biomass burning and mineral dust aerosol to NNP during the first half of the experiment. The fine fraction sulfur component correlated well with the pyrogenic activity before the change in meteorological patterns halfway through the experiment. The fine and coarse sulfur concentrations nearly doubled in the latter part of the experiment as a monsoon circulation brought sulfur‐enriched aerosol from the Atlantic Ocean. Various industrial activities on the coast of Cameroon and Gabon probably contributed to the high sulfur concentrations as well.

Characterization of novel di- and tricarboxylic acids in fine tropical aerosols.

Three unknown di- and tricarboxylic acids were characterized in the fine size fraction of aerosols which were collected during the wet season in the Amazon basin (Rondonia, Brazil). For the structural characterization of the methyl esters of these unknown compounds, mass spectrometry with electron ionization (EI) and tandem mass spectral techniques combined with gas chromatographic (GC) separation were employed. Fragment and parent ion spectra were recorded during elution of the GC peaks by linked scanning of the B and E sectors in combination with high-energy collision-induced dissociation. The fragmentation patterns of significant ions in the first-order EI spectra were also obtained for nonanedioic acid, which was examined as a model compound. The compounds were tentatively identified as 4-acetyloxyheptanedioic acid and cis and trans isomers of 5-hexene-1,1,6-tricarboxylic acid. Since there were indications of biomass burning during the aerosol sampling the di- and tricarboxylic acids characterized in the present work could be markers for biomass burning. Furthermore, the characterization of di- and tricarboxylic acids in the fine size fraction of atmospheric aerosols may be important for assessing the effects of organic aerosols in cloud formation.

Humic Marine Matter and Insoluble Materials in Antarctic Snow

The aim of the present work is to show that the insoluble components of marine origin are always present, together with the soluble ones, in both the coarse fraction and in the fine fraction of the marine aerosol and that they make up a non negligible part of the insoluble material in Antarctic snow. The results obtained show that a large proportion of the insoluble matter present in high altitude Antarctic snow consists of marine organic matter involved in the aerosolization process and that the thermolabile fraction (4000C), largely consisting of fulvic acids, increases with increasing altitude. The effect of distance from the sea coast is harder to demonstrate for particulate fulvic acids at least over the short distances investigated herein (150 km) and owing to the complex orography of the sample areas.

Chemical composition of aerosols collected over the tropical North Atlantic Ocean

Ambient aerosol samples were collected over the tropical northern Atlantic Ocean during the month of April 1996 onboard the R/V Seward Johnson. Dichotomous high‐volume collector samples were analyzed for ferrous iron immediately after collection, while trace metals, anions, and cations were determined upon return to the laboratory. Data are analyzed with the aid of enrichment factor, principal component, and weighted multiple linear regression analyses. Average mineral aerosol concentrations amounted to 19.3±16.4 μg m−3 whereby the chemical characteristics and air mass back trajectories indicated the dust to be of a typical shale composition and Saharan origin. Calcite accounted for 3.0 and 7.9% of the mineral aerosol during the first and second halves of the cruise, respectively. Total iron concentrations (averaging 0.84±0.61 μg m−3) are crustally derived, of which 0.51±0.56% is readily released as Fe(II). Eighty‐six percent of this Fe(II) is present in the fine (&lt;3 μm diameter) aerosol fraction and correlates with NSS‐SO42− and oxalate. Approximately 23% of the measured NSS‐SO42− in both size fractions appears to be biogenically derived, and the rest is of anthropogenic nature. Biogenic SO42− /methanesulfonic acid (MSA) ratios could not be easily extracted by employing a multiple linear regression analysis analogous to that of Johansen et al. [1999], possibly due to the varying characteristics of the aerosol chemistry and air temperature during the cruise. Because of the presence of anthropogenic SO42−, the non‐sea‐salt (NSS)‐ SO42−/MSA ratio, 37.4±6.4, is elevated over what would be expected if the NSS ‐ SO42− were purely biogenic. Cl− depletion is seen in all samples and averages 18.3±9.1%. The release of Cl from the aerosol phase appears to occur through acid displacement reactions with primarily HNO3 in the coarse and H2SO4 in the fine fraction.

Contributions to light extinction during project MOHAVE

The contribution of aerosols to light extinction at Meadview, AZ, during summer 1992 was estimated using Mie theory and size-resolved aerosol chemical measurements. Sulfate particle size increased as a function of relative humidity. Twelve-hour average light scattering was estimated to within 15%. Sulfate was the most abundant chemical component in the fine aerosol fraction. On average, Rayleigh scattering, coarse particles, and fine sulfates contributed 39, 21, and 19% to total light extinction. Average estimated light scattering was largely insensitive to assumptions about mixing state, degree of sulfate neutralization and organic carbon water uptake properties. It was estimated that a reduction of Mohave Power Plant (MPP) SO 2 emissions corresponding to a contribution of 19% to ambient sulfate would have resulted in a decrease in total light extinction of between 3.3 and 5.3%.

Moisture Uptake and Its Influence on Pressurized Metered-Dose Inhalers

The objective of this study was to investigate moisture ingress into pressurized metered dose inhalers (pMDIs) containing hydrofluoroalkane (HFA) propellants and the consequences of this ingress. Moisture ingress into the pMDIs containing tetrafluoroethane (HFA 134a) or heptafluoropropane (HFA 227) was evaluated and modeled. The influence of water level in pMDIs on the stability of pMDIs containing triamicinolone acetonide (TAA) and beclomethasone dipropionate (BDP) in terms of particle growth, fine particle fraction, and drug solubility in the propellant system was evaluated using scanning electron microscopy, particle size analysis, single-stage impaction, and HPLC. The water level in HFA-containing pMDIs increased during storage and the process obeyed a diffusion model. HFA 134a had a greater tendency to take up moisture from the environment than did HFA 227. Unlike TAA, the propensity for particle growth of the suspended BDP in HFA propellants was significantly depressed by the increase in water level in the pMDIs. As a result, the fine particle fraction of the emitted BDP aerosols significantly increased as the water level in the HFA propellant was increased. Moisture ingress into pMDIs containing HFAs occurred during storage. The influence of the increased water level in pMDIs on the physical stability of the pMDI formulation and the dose delivery performance was a function of the composition of the internal lining of the container, the type of drug and propellant, and storage temperature.

Source apportionment near a steel plant in Genoa (Italy) by continuous aerosol sampling and PIXE analysis

The particulate emissions near a large steel plant, located inside the town of Genoa (Italy) have been studied from May to December 1997. We have used two-stage continuous streaker samples and subsequent PIXE (particle-induced X-ray emission) analysis with hourly resolution, to follow both seasonal and daily trends. A first streaker sampler remained installed very close to the plant cokery and furnaces, while another sampler was moved to different locations in town. Samples were analysed by PIXE, deducing concentrations for elements from Na to Pb. We have always collected the PM 10 fraction of the aerosol: during part of the campaign, the fine (PM 2.5) and coarse (PM 2.5–10) aerosol fractions have been also resolved. We have measured and analysed about 8500 PIXE spectra. The steel plant emissions have been identified and resolved from other aerosol sources using principal component analysis (PCA) and other statistical techniques. Finally, the impact of the steel smelter on its surrounding has been evaluated.

Matrix effects in PIXE analysis of aerosols and ashes.

A comparison of instrumental neutron activation analysis (INAA) and proton-induced X-ray emission (PIXE) results for size-fractionated atmospheric aerosols ("coarse" and "fine" fractions with an equivalent aerodynamic diameter of 2-10 microns and < 2 microns, respectively, or the PM10 fraction) showed that PIXE yielded significantly lower results for the PM10 and coarse fractions, especially for elements with a low Z resulting from a particle size effect. Somewhat lower PIXE results were also obtained for the fine fraction of atmospheric aerosols. A correction is also needed for irregularly shaped deposits of combustion aerosols collected by a cascade impactor in 11 size fractions ranging from 0.016 to 14.3 microns, as well as for thick samples of fly and bottom ashes. An equivalent layer thickness (ELT) model is proposed to correct the matrix effects in PIXE. The approaches for the calculation of ELT using a comparison of PIXE and INAA results or by comparing PIXE results obtained using two different incident proton beam energies (1.31 and 2.35 MeV) are described. The correction for the ash pellets and irregular deposits are also discussed.

Comparison of two particle-size spectrometers for ambient aerosol measurements

There is an ongoing debate on the question which size fraction of particles in ambient air may be responsible for human health effects observed in epidemiological studies. Since there is no single instrument available for the measurement of the particle-size distribution over the full range of the fine fraction (diameter <2.5 μm) of the atmospheric aerosol, two instruments, the mobile aerosol spectrometer (MAS) and the electrical aerosol spectrometer (EAS), have been tested in a side-by-side comparison measuring ambient aerosol for a time period of six weeks in spring 1996 in the city of Erfurt, Germany. Furthermore, total particle number concentration measured by a condensation particle counter (CPC) and mass concentrations PM 10 and PM 2.5 were determined. Both spectrometers, MAS and EAS, are based on electrical mobility measurements for particles <0.1 μm and <0.5 μm, respectively, while MAS applies optical particle spectrometry and EAS applies again electrical mobility analysis for particles up to 2.5 and 10 μm, respectively. Both instruments proved to be reliable during this comparison providing data availability of >94%. To compare the spectral data, particle numbers were integrated within three size ranges: 0.01 – 0.1, 0.1 – 0.5, 0.5 – 2.5 μm. Hourly mean number concentrations of each size range observed during the six week comparison was: 2.6×10 4±19500 (2.48×10 4±1.79×10 4), 3.1×10 3±1.5×10 3 (4.1×10 3±2.0×10 3), 50±45 (1.9×10 2±1.2×10 2) cm −3 for MAS (EAS), respectively. Both aerosol spectrometers followed the variations of the ambient aerosol in a similar manner and yielded almost identical results for particle number concentrations of particles with diameters smaller than 0.5 μm. Furthermore, the total particle number concentration derived from MAS and EAS measurements (29000±20000; 29000±19000 cm −3) is well comparable with the number concentration derived from an integral counting CPC (31100±22000 cm −3). The results of this side-by-side comparison suggest that MAS and EAS together with PM 2.5 measurements are suitable to reliably characterize size-distribution parameters of number and mass concentration of ambient aerosols.

Non‐sea‐salt sulfate, methanesulfonate, and nitrate aerosol concentrations and size distributions at Cape Grim, Tasmania

We collected weekly aerosol samples using high‐volume impactors over a period of 20 months (1988–1990) at the Cape Grim baseline station on the northwestern coast of Tasmania, Australia. The samples were analyzed for soluble ionic constituents, including sulfate, methanesulfonate (MS−), ammonium, nitrate, and the major sea‐salt ions. The sea‐salt component showed only a slight seasonal variation, whereas the non‐sea‐salt (nss) ions all had pronounced summer maxima. Significant interannual variability was seen between the nss ion concentrations measured during the two summers investigated. Nss sulfate and MS− were present both in the fine and coarse aerosol fractions, in the latter presumably associated with sea‐salt particles. During the winter period, there was more nss sulfate in the coarse fraction than in the fine fraction. These observations are consistent with an important role of liquid‐phase oxidation in haze and cloud droplets for the production of nss sulfate aerosol. The seasonal behavior of the sulfur and nitrogen species at Cape Grim and their mutual correlations suggest that DMS oxidation is the dominant sulfur source during summer, while nonbiogenic sulfur sources make significant contributions to nss sulfate outside of this season. Correlations of CN and CCN concentrations with nss sulfate, MS−, and wind speed suggest that DMS oxidation and, to a lesser extent, seaspray formation contributes to CN and CCN populations. The contrast between the weak seasonality of the sea‐salt component and the pronounced seasonal behavior in both sulfur species and CCN supports the central role of biogenic DMS emissions as precursors of CCN in this region, at least in the biologically productive season.