Wintertime and summertime São Paulo aerosol source apportionment study

A detailed aerosol source apportionment study was performed with two sampling campaigns, during wintertime and summertime in the heavily polluted metropolitan area of São Paulo, Brazil. In addition to 12 h fine and coarse mode filter sampling, several real time aerosol and trace gas monitors were used. PM₁₀ was sampled using stacked filter units that collects fine (d<2.5 μm) and coarse (2.5<d<10 μm) particulate matter, providing mass, black carbon (BC) and elemental concentration for each aerosol mode. The concentration of about 20 elements was determined using the particle induce X-ray emission technique. Real time aerosol monitors provided PM₁₀ aerosol mass (TEOM), organic and elemental carbon (Carbon Monitor 5400, R&P) and BC concentration (Aethalometer). A complex system of sources and meteorological conditions modulates the heavy air pollution of the urban area of São Paulo. The boundary layer height and the primary emissions by motor vehicles controls the strong pattern of diurnal cycles obtained for PM₁₀, BC, CO, NO_x, and SO₂. Absolute principal factor analysis results showed a very similar source pattern between winter and summer field campaigns, despite the different locations of the sampling sites of both campaigns, pointing that there are no significant change in the main air pollution sources. The source identified as motor vehicle represented 28% and 24% of the PM_2.5 for winter and summer, respectively. Resuspended soil dust accounted for 25% and 30%. The oil combustion source represented 18% and 21%. Sulfates accounts for 23% and 17% and finally industrial emissions contributed with 5% and 6% of PM_2.5, for winter and summer, respectively. The resuspended soil dust accounted for a large fraction (75–78%) of the coarse mode aerosol mass. Certainly automobile traffic and soil dust are the main air pollution sources in São Paulo. The sampling and analytical procedures applied in this study showed that it is possible to perform a quantitative aerosol source apportionment in a complex urban area such as São Paulo.     

Quantifying the sources of hazardous elements of suspended particulate matter aerosol collected in Yokohama,Japan

We analyzed metals (Mg, Al, Ca, V, Cr, Mn, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Ag, Cd, Cs, Ba, Pb and Bi), water-soluble ions (Na⁺, NH₄⁺, K⁺, Ca²⁺, Cl^?, NO₃^? and SO₄^2?) and carbonaceous mass (EC and OC) in SPM aerosol samples using an ICP-MS, ion chromatograph and CHN corder, respectively. The SPM samples were collected from 1999 to 2005 at two locations (urban site A and industrial site B) of Yokohama, Japan with concentrations in mean and ranges of 34.2 and 19.7–50.3 μg m^?3 and 22.9 and 12.7–35.1 μg m^?3 for the respective location. Source apportionment of SPM aerosol was conducted appropriately for the first time to these locations employing PCA-APCS technique. Major sources of SPM at site A were a) crustal source, b) urban origin, c) undefined, and d) mineral rock. At site B, the sources were predicted as a) urban origin, b) undefined, c) crustal source, and d) secondarily formed aerosol. The tracers and nature of the source related to urban origin at both sites were similar but retaining different source strength. Secondarily formed aerosol was quite unique at site B. However, mineral rock was remarkable at site A.     

Atmospheric nitrogen fluxes at the Belgian coast: 2004–2006

Daily and seasonal variations in dry and wet atmospheric nitrogen fluxes have been studied during four campaigns between 2004 and 2006 at a coastal site of the Southern North Sea at De Haan (Belgium) located at coordinates of 51.1723° N and 3.0369° E. Concentrations of inorganic N-compounds were determined in the gaseous phase, size-segregated aerosol (coarse, medium, and fine), and rainwater samples. Dissolved organic nitrogen (DON) was quantified in rainwater. The daily variations in N-fluxes of compounds were evaluated with air-mass backward trajectories, classified into the main air-masses arriving at the sampling site (i.e., continental, North Sea, and Atlantic/UK/Channel).The three, non-episodic campaigns showed broadly consistent fluxes, but during the late summer campaign exceptionally high episodic N-deposition was observed. The average dry and wet fluxes for non-episodic campaigns amounted to 2.6 and 4.0 mg N m^?2 d^?1, respectively, whereas during the episodic late summer period these fluxes were as high as 5.2 and 6.2 mg N m^?2 d^?1, respectively.Non-episodic seasons/campaigns experienced average aerosol fluxes of 0.9–1.4 mg N m^?2 d^?1. Generally, the contribution of aerosol NH₄⁺ was more significant in the medium and fine particulate fractions than that of aerosol NO₃^?, whereas the latter contributed more in the coarse fraction, especially in continental air-masses. During the dry mid-summer campaign, the DON contributed considerably (～15%) to the total N-budget.Exceptionally high episodic aerosol-N inputs have been observed for the late summer campaign, with especially high deposition rates of 3.6 and 2.9 mg N m^?2 d^?1 for Atlantic/UK/Channel and North Sea-continental (mixed) air-masses, respectively. During this pollution episode, the flux of NH₄⁺ was dominating in each aerosol fraction/air-mass, except for coarse continental aerosols. High deposition of gaseous-N was also observed in this campaign with an average total N-flux of 2–2.5-times higher than in other campaigns.     

Water-soluble organic nitrogen (WSON) in size-segregated atmospheric particles over the Eastern Mediterranean

Atmospheric water-soluble organic nitrogen (WSON) was determined on size-segregated aerosol particles collected during a two years period (2005–2006) in a remote marine location in the Eastern Mediterranean (Finokalia, Crete island). Average concentration of WSON was 5.5 ± 3.9 nmol m^?3 and 11.6 ± 14.0 nmol m^?3 for coarse (PM_1.3-10) and fine (PM_1.3) mode respectively, corresponding to 13% of Total Dissolved Nitrogen (TDN) in both modes. Air masses origin and correlation with tracers of natural and anthropogenic sources indicate that combustion process (biomass burning and fossil fuel) and African dust play an important role in regulating levels of WSON in both coarse and fine aerosol fractions. Chemical speciation of organic nitrogen pool was attempted by analyzing 47 fine aerosol samples (PM₁) for 17 free amino acids (N-FAA), dimethylamine (DMA) and trimethylamine (TMA). The average concentration of N-FAA was 0.5 ± 0.5 nmol m^?3, while the average concentration of DMA was 0.2 ± 0.8 nmol m^?3, TMA was below detection limit. The percentage contribution of N-FAA and DMA to WSON was 2.1 ± 2.3% and 0.9 ± 3.4%, respectively.     

Seasonal and spatial trends in the sources of fine particle organic carbon in Israel,Jordan, and Palestine

A study of carbonaceous particulate matter (PM) was conducted in the Middle East at sites in Israel, Jordan, and Palestine. The sources and seasonal variation of organic carbon, as well as the contribution to fine aerosol (PM_2.5) mass, were determined. Of the 11 sites studied, Nablus had the highest contribution of organic carbon (OC), 29%, and elemental carbon (EC), 19%, to total PM_2.5 mass. The lowest concentrations of PM_2.5 mass, OC, and EC were measured at southern desert sites, located in Aqaba, Eilat, and Rachma. The OC contribution to PM_2.5 mass at these sites ranged between 9.4% and 16%, with mean annual PM_2.5 mass concentrations ranging from 21 to 25 ug m^?3. These sites were also observed to have the highest OC to EC ratios (4.1–5.0), indicative of smaller contributions from primary combustion sources and/or a higher contribution of secondary organic aerosol. Biomass burning and vehicular emissions were found to be important sources of carbonaceous PM in this region at the non-southern desert sites, which together accounted for 30%–55% of the fine particle organic carbon at these sites. The fraction of measured OC unapportioned to primary sources (1.4 μgC m^?3 to 4.9 μgC m^?3; 30%–74%), which has been shown to be largely from secondary organic aerosol, is relatively constant at the sites examined in this study. This suggests that secondary organic aerosol is important in the Middle East during all seasons of the year.     

Aerosol mass-size distributions at a tropical coastal environment: response to mesoscale and synoptic processes

Regular measurements of total mass concentration and mass-size distribution of near-surface aerosols, made using a ten-channel Quartz Crystal Microbalance (qcm) Impactor for the period October 1998–December 1999 at the tropical coastal station Trivandrum (8.5°N, 77°E), are used to study the response of aerosol characteristics to regional mesoscale and synoptic processes. Results reveal that aerosol mass concentrations are generally higher under land breeze conditions. The sea breeze generally has a cleansing effect, depleting the aerosol loading. The continental air (LB regime) is richer in accumulation mode (submicron) aerosols than the marine air. On a synoptic scale, aerosol mass concentration in the submicron mode decreased from an average high value of ∼86 μg m⁻³ during the dry months (January–March) to ∼11 μg m⁻³ during the monsoon season (June–September). On the contrary mass concentration in the supermicron mode increased from a low value of ∼15 μg m⁻³ during the dry months to reach a comparatively high value of ∼35 μg m⁻³ during April, May. Correspondingly, the effective radius (R_eff) increased from a low value of 0.15–0.17 μm to ∼0.3 μm indicating a seasonal change in the size distribution. The mass-size distribution shows mainly three modes, a fine mode (∼0.1 μm); a large mode (∼0.5 μm) and a coarse mode (∼3 μm). The fine mode dominates in winter. In summer the large mode becomes more conspicuous and the coarse mode builds up. The fine mode is highly reduced in monsoon and the large and coarse modes continue to remain high (replenished) so that their relative dominance increases. The size distribution tends to revert to the winter pattern in the post-monsoon season. Accumulation (submicron) aerosols account for ∼98% of the total surface area and ∼70% of the total volume of aerosols during winter. During monsoon, even though they still account for ∼90% of the area, their contribution to the volume is reduced to ∼50%; the coarse aerosols account for the rest.     

Seasonal characteristics of water-soluble organic carbon in atmospheric particles in the inland Kanto plain,Japan

An investigation of water-soluble organic carbon (WSOC) in atmospheric particles was conducted as an index of the formation of secondary organic aerosol (SOA) from April 2005 to March 2006 at Maebashi and Akagi located in the inland Kanto plain in Japan. Fine (<2.1 μm) and coarse (2.1–11 μm) particles were collected by using an Andersen low-volume air sampler, and WSOC, organic carbon (OC), elemental carbon (EC), and ionic components were measured. The mean mass concentrations of the fine particles were 22.2 and 10.5 μg m^?3 at Maebashi and Akagi, respectively. The WSOC in fine particles accounted for a large proportion (83%) of total WSOC. The concentration of fine WSOC ranged from 1.2 to 3.5 μg-C m^?3 at Maebashi, rising from summer to fall. At Akagi, it rose from spring to summer, associated with the southerly wind from urban areas. The WSOC/OC ratio increased in summer at both sites, but the ratio at Akagi was higher, which we attributed to differences in primary emissions and secondary formation between the sites. The fine WSOC concentration was significantly positively correlated with concentrations of SO₄^2?, EC, and K⁺, and we inferred that WSOC was produced by photochemical reaction and caused by the combustion of both fuel and biomass. We estimated that SOA accounted for 11–30% of the fine particle mass concentration in this study, suggesting that SOA is a significant year-round component in fine particles.     

Inorganic,organic and macromolecular components of fine aerosol in different areas of Europe in relation to their water solubility

A chemical mass balance of fine aerosol (<1.5 μm AED) collected at three European sites was performed with reference to the water solubility of the different aerosol classes of components. The sampling sites are characterised by different pollution conditions and aerosol loading in the air. Aspvreten is a background site in central Sweden, K-puszta is a rural site in the Great Hungarian Plain and San Pietro Capofiume is located in the polluted Po Valley, northern Italy. The average fine aerosol mass concentration was 5.9 μg m^-3 at the background site Aspvreten, 24 μg m^-3 at the rural K-puszta and 38 μg m^-3 at the polluted site San Pietro Capofiume. However, a similarly high soluble fraction of the aerosol (65–75%) was measured at the three sites, while the percentage of water soluble organic species with respect to the total soluble mass was much higher at the background site (ca. 50%) than at the other two sites (ca. 25%). A very high fraction (over 70%) of organic compounds in the aerosol consisted of polar species. The presence of water soluble macromolecular compounds was revealed in the samples from K-puszta and San Pietro Capofiume. At both sites these species accounted for between ca. 20–50% of the water soluble organic fraction. The origin of the compounds was tentatively attributed to biomass combustion.     

Study of size distribution of atmospheric aerosol at Agra

Measurements on size distribution of atmospheric aerosol were made at Dayalbagh, Agra during July to September 1998. A 4-stage cascade particle sampler (CPS - 105) which fractionates particles in sizes ranging between 0.7 and >10.9 μm, was used. Samples were collected on Whatman 41 filters. The filters were analyzed for the major water-soluble ions. The anions (F, Cl, NO₃ and SO₄) were analyzed by Dionex DX-500 ion chromatograph while atomic absorption and colorimetric techniques were used for the analysis of cations (Na, K, Ca and Mg) and NH₄, respectively. The average mass of aerosol was found to be 131.6 μg m⁻³ and aerosol composition was found to be influenced by terrigeneous sources. The mass size distribution of total aerosol and the ions NH₄, Cl, NO₃, K, Ca, Mg, SO₄ and Na was bimodal while that of F was unimodal. SO₄, F, K and NH₄ dominated in the fine mode while Ca, Mg, Cl and NO₃ were in abundance in coarse fraction. Na was found in both coarse as well as fine mode. Coarse mode SO₄ and NO₃ have been ascribed to contribution from re-suspension of soil and formation by heterogeneous oxidation on soil derived particles. Preponderance of K in fine mode is attributed to emissions from vegetation and from burning of plant materials. Ca, Mg, Cl and NO₃ are largely soil derived and hence dominate in coarse fraction. Equivalent ratios of NH₄/(SO₄+NO₃) were calculated for both fine and coarse aerosols. The coarse mode ratio varied between 0.7 and 1.4 while in fine mode it ranged between 1.4 and 1.9. It shows that aerosol is basic, the basicity of coarse mode is due to higher concentration of soil-derived alkaline components while the basicity in fine mode is due to neutralization of acidity by NH₃.     

Deposition rates on smooth surfaces and coagulation of aerosol particles inside a test chamber

Because aerosol particle deposition is an important factor in indoor air quality, many empirical and theoretical studies have attempted to understand the process. In this study, we estimated the deposition rate of aerosol particles on smooth aluminum surfaces inside a test chamber. We investigated the influence of turbulent intensity due to ventilation and fan operation. We also investigated two important processes in particle deposition: turbophoresis, which is significant for micron particles, and coagulation, which is relevant to ultrafine particles (UFP diameter <0.1 μm) at high particle concentrations. Our analysis included semi-empirical estimates of the deposition rates that were compared to available deposition models and verified with simulations of an aerosol dynamics model. In agreement with previous studies, this study found that induced turbulent intensity greatly enhanced deposition rates of fine particles (FP diameter <1 μm). The deposition rate of FP was proportional to the ventilation rate, and it increased monotonically with fan speed. With our setup, turbophoresis was very important for coarse particles larger than 5 μm. The coagulation of aerosol particles was insignificant when the particle concentration was less than 10⁴ cm^?3 during fan operation. The model simulation results verified that the aerosol dynamics module incorporated in our Multi-Compartment and Size-Resolved Indoor Aerosol Model (MC-SIAM) was valid. The behavior of aerosol particles inside our chamber was similar to that found in real-life conditions with the same ventilation rates (0.018–0.39 h^?1) and similar air mixing modes. Therefore, our findings provide insight into indoor particle behavior.     

Characterisation of PM10 atmospheric aerosols for the wet season 2005 at two sites in East Africa

Ambient daily PM₁₀ aerosol samples were collected at two sites in Tanzania in May and June 2005 (during the wet season), and their chemical characteristics were studied. The sites were a rural site in Morogoro and an urban kerbside site in Dar es Salaam. A Gent PM₁₀ stacked filter unit sampler with sequential Nuclepore polycarbonate filters, providing fine and coarse size fractions, and a PM₁₀ sampler with quartz fibre filters were deployed. Parallel collections of 24 h were made with the two samplers and the number of these collections was 13 in Morogoro and 16 in Dar es Salaam. The average mass concentration of PM₁₀ was 27 ± 11 μg/m³ in Morogoro and 51 ± 21 μg/m³ in Dar es Salaam. In Morogoro, the mean concentrations of organic carbon (OC), elemental carbon (EC), and water-soluble organic carbon (WSOC) were 6.8, 0.51, and 2.8 μg/m³, respectively. In contrast, higher mean concentrations (11.9, 4.6, and 3.3 μg/m³, respectively) were obtained for Dar es Salaam. At both sites, species and elements, such as black carbon, NH₄⁺, non-sea-salt SO₄^2?, K, and Ni (and at Dar es Salaam also V, As, Br, and Pb) were mainly present in the fine size fraction. The common crustal and sea-salt elements, including Na, Mg, Al, Si, Cl, Ca, Ti, Mn, Fe, and Sr, and also NO₃^? and P (and to a lesser extent Cu and Zn) were concentrated in the coarse particles. Aerosol chemical mass closure indicated that the PM₁₀ mass in Morogoro consisted, on average, of 48% organic matter (OM), 44% crustal matter, 4% sea salt, and 2% EC, while in Dar es Salaam OM, crustal matter, sea salt, and EC represented 37%, 32%, 9%, and 9% of the PM₁₀ mass. The contributions of the secondary inorganic aerosol (non-sea-salt sulphate, nitrate, and ammonium) were small, i.e., only 5% in total at each site. Carbonaceous materials and crustal matter were thus the most important components of the PM₁₀ mass. It is suggested that biomass burning is a major contributor to the OM; at Dar es Salaam there is also a very substantial contribution from traffic. A source apportionment calculation indicated that 68% of the OC at this site originated from traffic exhaust versus 32% from charcoal burning. The crustal matter at Morogoro is likely mainly attributable to soil dust resuspension, whereas in Dar es Salaam it is likely mostly resuspended road dust.     

Source apportionment analysis of atmospheric particulates in an industrialised urban site in southwestern Spain

A detailed physical and chemical characterisation of total suspended particles (TSP) in the highly industrialised city of Huelva (southwestern Spain) was carried out. The results evidenced a coarse grain-size prevalence (PM₁₀ accounting for only 40% of TSP mass, 37 and 91 μg/m³, respectively). PM₁₀ levels are in the usual range for urban background sites in Spain. The crustal, anthropogenic and marine components accounted for a mean of a 40%, 24% and 5% of bulk TSP, respectively. As expected from the industrial activities, relatively high PO₄³⁻ and As levels for an urban site were detected. In addition to the crustal and marine components, source apportionment analysis revealed three additional emission sources influencing the levels and composition of TSP: (a) a petrochemical source, (b) a mixed metallurgical-phosphate source, (c) and an unknown source (Sb and NO₃⁻).Due to the high local emissions, the mean TSP anthropogenic contribution (mostly PM₁₀) obtained for all possible air mass transport scenarios reached 18–29 μg/m³. The 2010 annual EU PM₁₀ limit value (20 μg/m³) would be exceeded by the anthropogenic load recorded for all the air mass transport scenarios, with the exception of the North Atlantic transport (only 15% of the sampling days). Under African air mass transport scenarios (20% of sampling days), the TSP crustal contribution reached near three times the local crustal contribution. It must be pointed out that this crustal input should diminish when sampling PM₁₀ due to the dominant coarse size distribution of this type of particles.     

Iron,manganese and copper emitted by cargo and passenger trains in Zürich (Switzerland): Size-segregated mass concentrations in ambient air

Particle emissions caused by railway traffic have hardly been investigated in the past, due to their obviously minor influence on air quality compared to automotive traffic. In this study, emissions related to particle abrasion from wheels and tracks were investigated next to a busy railway line in Zürich (Switzerland), where trains run nearly exclusively with electrical locomotives. Hourly size-segregated aerosol samples (0.1–1, 1–2.5 and 2.5–10 μm) were collected with a rotating drum impactor (RDI) and subsequently analyzed by synchrotron radiation X-ray fluorescence spectrometry (SR-XRF). In this way, hourly elemental mass concentrations were obtained for chromium, manganese, iron and copper, which are the elements most relevant for railway abrasion. Additionally, daily aerosol filters were collected at the same site as well as at a background site for subsequent analysis by gravimetry and wavelength dispersive XRF (WD-XRF). Railway related ambient air concentrations of iron and manganese were calculated for the coarse (2.5–10 μm) and fine (<2.5 μm) particle fraction by means of a Mn/Fe ratio investigation. The comparison to train type and frequency data showed that 75% and 60% of the iron and manganese mass concentrations related to cargo and passenger trains, respectively, were found in the coarse mode. The railway related iron mass concentration normalized by the train frequency ranges between 10 and 100 ng m⁻³ h iron in 10 m distance to the tracks, depending on train type. It is estimated that the personal exposure next to a busy railway line above ground is more than a magnitude lower than inside a subway station.     

Fire and biofuel contributions to annual mean aerosol mass concentrations in the United States

We estimate the contributions from biomass burning (summer wildfires, other fires, residential biofuel, and industrial biofuel) to seasonal and annual aerosol concentrations in the United States. Our approach is to use total carbonaceous (TC) and non-soil potassium (ns-K) aerosol mass concentrations for 2001–2004 from the nationwide IMPROVE network of surface sites, together with satellite fire data. We find that summer wildfires largely drive the observed interannual variability of TC aerosol concentrations in the United States. TC/ns-K mass enhancement ratios from fires range from 10 for grassland and shrub fires in the south to 130 for forest fires in the north. The resulting summer wildfire contributions to annual TC aerosol concentrations for 2001–2004 are 0.26 μg C m⁻³ in the west and 0.14 μg C m⁻³ in the east; Canadian fires are a major contributor in the east. Non-summer wildfires and prescribed burns contribute on an annual mean basis 0.27 and 0.31 μg C m⁻³ in the west and the east, highest in the southeast because of prescribed burning. Residential biofuel is a large contributor in the northeast with annual mean concentration of up to 2.2 μg C m⁻³ in Maine. Industrial biofuel (mainly paper and pulp mills) contributes up to 0.3 μg C m⁻³ in the southeast. Total annual mean fine aerosol concentrations from biomass burning average 1.2 and 1.6 μg m⁻³ in the west and east, respectively, contributing about 50% of observed annual mean TC concentrations in both regions and accounting for 30% (west) and 20% (east) of total observed fine aerosol concentrations. Our analysis supports bottom-up source estimates for the contiguous United States of 0.7–0.9 Tg C yr⁻¹ from open fires (climatological) and 0.4 Tg C yr⁻¹ from biofuel use. Biomass burning is thus an important contributor to US air quality degradation, which is likely to grow in the future.     

Aerosol physical,chemical and optical properties during the Rocky Mountain Airborne Nitrogen and Sulfur study

During the Rocky Mountain Airborne Nitrogen and Sulfur (RoMANS) study, conducted during the spring and summer of 2006, a suite of instruments located near the eastern boundary of Rocky Mountain National Park (RMNP) measured aerosol physical, chemical and optical properties. Three instruments, a differential mobility particle sizer (DMPS), an optical particle counter (OPC), and an aerodynamic particle sizer (APS), measured aerosol size distributions. Aerosols were sampled by an Interagency Monitoring of Protected Visual Environments (IMPROVE) sampler and a URG denuder/filter-pack system for compositional analysis. An Optec integrating nephelometer measured aerosol light scattering. The spring time period had lower aerosol concentrations, with an average volume concentration of 2.2 ± 2.6 μm³ cm^?3 compared to 6.5 ± 3.9 μm³ cm^?3 in the summer. During the spring, soil was the single largest constituent of PM_2.5 mass, accounting for 32%. During the summer, organic carbon accounted for 60% of the PM_2.5 mass. Sulfates and nitrates had higher fractional contributions in the spring than the summer. Variability in aerosol number and volume concentrations and in composition was greater in the spring than in the summer, reflecting differing meteorological conditions. Aerosol scattering coefficients (b_sp) measured by the nephelometer compared well with those calculated from Mie theory using size distributions, composition data and modeled RH dependent water contents.     

Sources of sodium in atmospheric fine particles

Concentrations of size fractionated particulate sodium and potassium were measured in both marine and urban air. Marine air sampling was conducted during a cruise on R/V Hakuho-maru in the northwestern North Pacific in the summer of 1998. Urban air sampling was performed in the central part of Tokyo in 1997 and 1998. The fine sodium concentration (D<1.1 μm) in “Urban” air (180 ng m⁻³) was 3 times higher than that in “Marine” air (56 ng m⁻³). In the urban air samples, the size distributions of sodium and potassium showed bimodal peaks in the fine particle range (D<1.1 μm) and in the coarse particle range (D>1.1 μm). The existence of anthropogenic sodium in the fine particle range was detected in the urban air. The K/Na weight ratios in the fine particle range of the urban air (1.8–2.7) was 50–75 times higher than that in seawater (0.036). Potassium in the urban air is thought to be derived largely from anthropogenic sources. In the urban air samples, a high correlation between fine sodium and fine potassium concentrations suggests that they have the same anthropogenic source. Reevaluating the K/Na ratios in marine air to be relatively higher than that in seawater, we can estimate that several percents of anthropogenic sodium can be transported from land to remote marine air.     

Effects of acid-washing filter treatment on quantification of aerosol organic compounds

The tests of standard mixtures and four sets of atmospheric particulate samples showed that an acid-wash (AW) pretreatment of fluorocarbon-coated glass fiber filters prior to aerosol sampling enhanced the quantifiable organic compounds for more than 29% (or 66 ng m⁻³); in particular, 47–273 ng m⁻³ (21–366%) more water-soluble organic compounds (WSOCs) were measured. When the acid-pretreated filters were employed, up to nine more organic species were measured in the individual daily samples. Because the acid pretreatment reduced the metal contaminants in the glass fiber filters, using the AW filters for aerosol sampling allows higher extraction recoveries of organic compounds. Since the fingerprinting compounds were more accurately determined when the aerosol samples were collected on the AW filters, better assessment of emission sources and toxicity of air pollutants can be obtained.     

Source apportionment of primary and secondary organic aerosols using positive matrix factorization (PMF) of molecular markers

Monthly average ambient concentrations of more than eighty particle-phase organic compounds, as well as total organic carbon (OC) and elemental carbon (EC), were measured from March 2004 through February 2005 in five cities in the Midwestern United States. A multi-variant source apportionment receptor model, positive matrix factorization (PMF), was applied to explore the average source contributions to the five sampling sites using molecular markers for primary and secondary organic aerosols (POA, SOA). Using the molecular makers in the model, POA and SOA were estimated for each month at each site. Three POA factors were derived, which were dominated by primary molecular markers such as EC, hopanes, steranes, and polycyclic aromatic hydrocarbons (PAHs), and which represented the following POA sources: urban primary sources, mobile sources, and other combustion sources. The three POA sources accounted for 57% of total average ambient OC. Three factors, characterized by the presence of reaction products of isoprene, α-pinene and β-caryophyllene, and displaying distinct seasonal trends, were consistent with the characteristics of SOA. The SOA factors made up 43% of the total average measured OC. The PMF-derived results are in good agreement with estimated SOA concentrations obtained from SOA to tracer yield estimates obtained from smog chamber experiments. A linear regression comparing the smog chamber yield estimates and the PMF SOA contributions had a regression slope of 1.01 ± 0.07 and an intercept of 0.19 ± 0.10 μg OC m^?3 (adjusted R² of 0.763, n = 58).     

Coarse atmospheric aerosol: size distributions of trace elements

A sampler, employing nine single stage impactors placed in parallel within a portable wind tunnel, has been used to determine the metal content of coarse atmospheric aerosol. The wind tunnel maintains a constant flow environment for the collectors housed inside it, so that representative sampling conditions are achieved compared to the varied ambient wind conditions. At a flow rate of 8 m s⁻¹ the 50% cut-off diameters of the impactors ranged from 7.8 to 38.8 μm. Measurements were conducted at a rural and urban site near Colchester in south east England. The samplers were analysed by PIXE for P, K, Ca, Fe, Ti, Mn, Cu, V, Co, Cr, Br, Zn, Ni, Sc and Pb. It is found that the sampler can be employed to quantitatively characterise the elemental mass size distribution for aerosol larger than 10 μm. The results indicate that a small fraction of the above earth and trace elements’ metal mass is present in particles greater than 10 μm. This fraction for earth metals (Ca, K, Ti) is comparatively greater in the rural site than the urban site, while for trace metals (Mn, V, Cu, Cr) this fraction constitutes a more significant part of the coarse mass at the urban site. Trace element concentrations were of a similar order of magnitude to earlier literature reports. Although the number of measurements was limited it can be concluded that the size distributions obtained were characteristic of an unpolluted area.     

Carbonaceous and inorganic composition in long-range transported aerosols over northern Japan: Implication for aging of water-soluble organic fraction

To better understand the influence of sources and atmospheric processing on aerosol chemical composition, we collected atmospheric particles in Sapporo, northern Japan during spring and early summer 2005 under the air mass transport conditions from Siberia, China and surrounding seas. The aerosols were analyzed for inorganic ions, organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC), and the major water-soluble organic compound classes (i.e., dicarboxylic acids and sugars). SO₄^2? is the most abundant inorganic constituent (average 44% of the identified inorganic ion mass) followed by NH₄⁺ (21%) and NO₃^? (13%). Concentrations of OC, EC, and WSOC ranged from 2.0–16, 0.24–2.9, and 0.80–7.9 μg m^?3 with a mean of 7.4, 1.0, and 3.1 μg m^?3, respectively. High OC/EC ratios (range: 3.6–19, mean: 8.7) were obtained, however WSOC/OC ratios (0.23–0.69, 0.44) do not show any significant diurnal changes. These results suggest that the Sapporo aerosols were already aged, but were not seriously affected by local photochemical processes. Identified water-soluble organic compounds (diacids + sugars) account for <10% of WSOC. Based on some marker species and air mass back trajectory analyses, and using stable carbon isotopic compositions of shorter-chain diacids (i.e., C₂–C₄) as photochemical aging factor of organic aerosols, the present study suggests that a fraction of WSOC in OC is most likely influenced by aerosol aging, although the OC loading in aerosols may be more influenced by their sources and source regions.