Chemical characteristics of organic aerosols in Algiers city area: influence of a fat manufacture plant

Total concentrations and homologue distributions of organic fraction constituents have been determined in particulate matter emitted from different units of a fat manufacturer (i.e. oils refining and conditioning plants, and production and conditioning units of a soap industry) located in Algiers area, as well as in atmospheric aerosols. In particular n-alkanes, n-alkanoic and n-alkenoic acids, n-alkan-2-ones and polycyclic aromatic hydrocarbons (PAH) were investigated. Organic aerosol contents varied broadly among the plant units, depending upon nature of the manufactured products. The percent composition of all classes of compounds investigated in ambient atmosphere was similar to those observed indoor at industrial plant units. Organic acids, n-alkanoic as well as n-alkenoic, appeared by far the most abundant organic constituents of aerosols, both indoor and outdoor, ranging from 7.7 to 19.8 and from 12.7 to 17.1 μg m⁻³, respectively. The huge occurrence of acids and n-alkanes in ambient aerosols was consistent with their high levels present in oil and fat materials. Among minor components of aerosols, n-alkan-2-ones and PAH, seemed to be related to thermally induced ageing and direct combustion of raw organic material used for oil and soap production.     

A wintertime study of polycyclic aromatic hydrocarbons (PAHs) in indoor and outdoor air in a big student residence in Algiers,Algeria

The wintertime concentrations and diel cycles of n-alkanes and polycyclic aromatic hydrocarbons (PAHs) associated to atmospheric particulate matter with aerodynamic diameter lesser than 10 μm were determined at the biggest student residence in Algeria located in Bab-Ezzouar, 15 km southeast from Algiers city area. Samplings were carried out from December 2009 to March 2010, and organic compounds were characterized using gas chromatography coupled with mass spectrometric detection. Volatile PAHs were also monitored inside some student residence rooms in order to evaluate the impact of indoor air pollution to student health. For the sake of comparison, aerial concentrations of n-alkanes and PAHs were determined in parallel in the Oued Smar industrial zone and two suburban areas, all located in Algiers. Total concentrations recorded in CUB1 student residence ranged from 101 to 204 ng?m^?3 for n-alkanes and from 8 to 87 ng?m^?3 for PAHs. Diel cycles have shown that, while concentrations of n-alkanes peaked at morning and afternoon–evening and dropped at night, those of PAHs exhibited higher levels at morning and night and lower levels at afternoon–evening, likely due to the reactivity of some PAHs. As expected, the indoor levels of PAHs were larger than in the outdoor of the student residence and were of serious health concern. Overall, the concentrations of n-alkanes and PAHs were as high as those observed in the industrial zone and higher than the two suburban sites.     

Biogenic and anthropogenic organic compounds in rain and snow samples collected in southern california

Ten rainwater and snow samples were collected from the Los Angeles area and its vicinity (semirural and rural areas) in S California. The samples were studied for various types of solvent-extractable organic compounds, including n-alkanes, UCM hydrocarbons, PAHs, FAs, benzoic acids and phenols. (See Table 1 for definition of acronyms.)In rural (mountain) snow samples, the major identifiable species are odd-carbon-numbered n-alkanesin the C₁₇–C₃₅ range and even-carbon-numbered FAs in the C₁₂–C₃₀ range, which are both of biogenic origin. On the other hand, Los Angeles urban rain samples contain abundant phenols, benzoic acids and UCM, which are considered to originate from incomplete combustion of fossil fuels mostly in automobile, as well as biogenic FAs. The results indicate that in urban areas, anthropogenic sources are the most important factor controlling the organic chemistry of rainwater, whereas biogenic sources are a minor contributor.Several indices are discussed for evaluating the anthropogenic/biogenic contribution to organic matter in wet deposition. The CPI of n-alkanes, UCM/n-alkanes ratio, phenols/C₁₂–C₃₀ FA ratio, benzoic acids/C₁₂–C₃₀ FA ratio, UCM/C₁₂–C₃₀FA ratio and PAH/C₁₂–C₃₀ FA ratio change drastically from rural to urban areas, indicating that they are useful indicators.     

Relevant organic components in ambient particulate matter collected at Svalbard Islands (Norway)

n-Alkanes, polynuclear aromatic hydrocarbons and n-alkanoic acids present in the inhalable fraction of airborne particles have been determined at the Italian scientific base sited in the area of Ny Alesund, Spitzbergen Island, Norway. Both the profiles of n-alkane and polynuclear aromatic congeners among the respective classes showed that anthropogenic sources were responsible for the presence of particulate organics in the atmosphere there, since the monomodal distribution of aliphatics and the fresh-emission shape of PAH fraction were observed. The total contents of n-alkanes and PAH ranged from 19 to 97 ng m⁻³ and from 0.6 to 2.0 ng m⁻³, respectively; n-alkanoic acids reached 6 ng m⁻³. The occurrence of nitrated-PAH of photochemical origin at trace extent (i.e. nitrated-fluoranthenes and nitropyrenes) has been also observed. Since the occurrence of OH radicals is required together with NO_x for the processes leading to the generation of 2-nitrofluoranthene and 2-nitropyrene would start, the detection of these nitrated species revealed the occurrence of photochemical processes in that region.     

Characterisation of PM10 emissions from woodstove combustion of common woods grown in Portugal

A series of source tests was performed to evaluate the chemical composition of particle emissions from the woodstove combustion of four prevalent Portuguese species of woods: Pinus pinaster (maritime pine), Eucalyptus globulus (eucalyptus), Quercus suber (cork oak) and Acacia longifolia (golden wattle). Analyses included water-soluble ions, metals, radionuclides, organic and elemental carbon (OC and EC), humic-like substances (HULIS), cellulose and approximately l80 organic compounds. Particle (PM₁₀) emission factors from eucalyptus and oak were higher than those from pine and acacia. The carbonaceous matter represented 44–63% of the particulate mass emitted during the combustion process, regardless of species burned. The major organic components of smoke particles, for all the wood species studied, with the exception of the golden wattle (0.07–1.9% w/w), were anhydrosugars (0.2–17% w/w). Conflicting with what was expected, only small amounts of cellulose were found in wood smoke. As for HULIS, average particle mass concentrations ranged from 1.5% to 3.0%. The golden wattle wood smoke presented much higher concentrations of ions and metal species than the emissions from the other wood types. The results of the analysis of radionuclides revealed that the ²²⁶Ra was the naturally occurring radionuclide more enriched in PM₁₀. The chromatographically resolved organics included n-alkanes, n-alkenes, PAH, oxygenated PAH, n-alkanals, ketones, n-alkanols, terpenoids, triterpenoids, phenolic compounds, phytosterols, alcohols, n-alkanoic acids, n-di-acids, unsaturated acids and alkyl ester acids.     

Identification,abundance and origin of atmospheric organic particulate matter in a Portuguese rural area

Respirable suspended particles high-volume samples were collected from a coastal-rural site in the centre of Portugal in August 1997 and their solvent-extractable organic compounds were subjected to characterisation by gas chromatography-mass spectrometry. Particles were also analysed by a thermal/optical technique in order to determine their black and organic carbon content. The total lipid extract yields ranged from 20 to 63 μg m⁻³, containing mainly aliphatic hydrocarbons such as n-alkanes, acids, alcohols, aldehydes, ketones and polycyclic aromatic hydrocarbons. The higher input of vascular plant wax components was demonstrated by the distribution patterns of the n-alkanes, n-alkanoic acids and n-alkanols homologous series, with C_max at C₂₉, C₂₂/C₂₄ and C₃₀, respectively. The CPI values for these series were in the range 1.8–9.7, being indicative of recent biogenic input from microbial lipid residues and flora epicuticular components. Specific natural constituents (e.g. phytosterols, terpenes, etc.) were identified as molecular markers. Some oxidation products from volatile organic precursors were also present in the aerosols. In addition, all samples had a component of petroleum hydrocarbons representing urban and vehicular emissions probably transported from the nearest cities and from the motorway in the vicinity. This data set could be used to make a mass balance with organic carbon, organic extracts and elutable matter, permitting also the comparison with lipid signatures observed for other regions.     

Particle size distribution of n-alkanes and polycyclic aromatic hydrocarbons (PAHS) in urban and industrial aerosol of Algiers,Algeria

The distribution of ambient air n-alkanes and polycyclic aromatic hydrocarbons (PAHs) associated to particles with aerodynamic diameters lesser than 10 μm (PM₁₀) into six fractions (five stages and a backup filter) was studied for the first time in Algeria. Investigation took place during September of 2007 at an urban and industrial site of Algiers. Size-resolved samples (<0.49, 0.49–0.95, 0.95–1.5, 1.5–3.0, 3.0–7.2, and7.2–10 μm) were concurrently collected at the two sampling sites using five-stage high-volume cascade impactors. Most of n-alkanes (~72 %) and PAHs (~90 %) were associated with fine particles ≤1.5 μm in both urban and industrial atmosphere. In both cases, the n-alkane contents exhibited bimodal or weakly bimodal distribution peaking at the 0.95–1.5-μm size range within the fine mode and at 7.3–10 μm in the coarse mode. Low molecular weight PAHs displayed bimodal patterns peaking at 0.49–0.95 and 7.3–10 μm, while high molecular weight PAHs exhibited mono-modal distribution with maximum in the <0.49-μm fraction. While the mass mean diameter of total n-alkanes in the urban and industrial sites was 0.70 and 0.84 μm, respectively, it did not exceed 0.49 μm for PAHs. Carbon preference index (~1.1), wax% (10.1–12.8), and the diagnostic ratios for PAHs all revealed that vehicular emission was the major source of these organic compounds in PM₁₀ during the study periods and that the contribution of epicuticular waxes emitted by terrestrial plants was minor. According to benzo[a]pyrene-equivalent carcinogenic power rates, ca. 90 % of overall PAH toxicity across PM₁₀ was found in particles ≤0.95 μm in diameter which could induce adverse health effects to the population living in these areas.     

Chemical Characterization of Emissions from Vegetable Oil Processing and Their Contribution to Aerosol Mass Using the Organic Molecular Markers Approach

ABSTRACT

The organic fraction of aerosol emitted from a vegetable oil processing plant was studied to investigate the contribution of emissions to ambient particles in the surrounding area. Solvent-soluble particulate organic compounds emitted from the plant accounted for 10% of total suspended particles. This percentage was lower in the receptor sites (less than 6% of total aerosol mass). Nonpolar, moderate polar, polar, and acidic compounds were detected in both emitted and ambient aerosol samples. The processing and combustion of olive pits yielded a source with strong biogenic characteristics, such as the high values of the carbon preference index (CPI) for all compound classes. Polycyclic aromatic hydrocarbons (PAHs) detected in emissions were associated with both olive pits and diesel combustion. The chromatographic profile of dimethyl-phenanthrenes (DMPs) was characteristic of olive pit combustion. Organic aerosols collected in two receptor sites provided a different pattern.

The significant contribution of vehicular emissions was identified by CPI values (~1) of n-alkanes and the presence of the unresolved complex mixture (UCM). In addition, PAH concentration diagnostic ratios indicated that emissions from catalyst and noncatalyst automobiles and heavy trucks were significant. The strong even-to-odd predominance of n-alkanols, n-alkanoic acids, and their salts indicated the contribution of a source with biogenic characteristics. However, the profile of DMPs at receptor sites was similar to that observed for diesel particulates. These differences indicated that the contribution of vegetable oil processing emissions to the atmosphere was negligible.     

Seasonal distribution of polar organic compounds in the urban atmosphere of two large cities from the North and South of Europe

Polar organic species, including n-alkanols, sterols, anhydrosugars, n-alkanoic acids, n-alkenoic acids and dicarboxylic acids were quantified to typify the composition of fine (PM_2.5) and coarse (PM_10–2.5) aerosols collected simultaneously at roadside and background sites in Oporto (Portugal) and Copenhagen (Denmark) during separate month-long intensive summer and winter campaigns. As a general trend, both cities exhibit roadside average concentrations higher than their correspondent urban background levels. The polar organics are more abundant in the fine fraction, exhibiting a seasonal pattern with high winter concentrations and low summer loads. Aerosols from both cities showed typical distributions of n-alkanols and n-alkanoic acids in the ranges C₁₂–C₂₈ and C₈–C₂₈, respectively. The <C₂₀ homologues, usually attributed to kitchen emissions, vehicular exhausts and microbial origins, dominated the fatty acid fraction. Linear alcohols were mainly represented by higher molecular weight homologues from vegetation waxes. Molecular tracer species for wood smoke (e.g. levoglucosan, mannosan and resinic acids) were found to contribute significantly to the urban aerosol, especially in winter. Ratios between these tracers indicated different biofuel contributions to the atmospheric particles of the two cities. Secondary constituents from both biogenic (e.g. pinonic acid) and anthropogenic precursors (e.g. phthalic and benzoic acids) were detected in both cities and seasons.     

Characterisation of carbonaceous aerosols from the Azorean Island of Terceira

Aerosol samples were collected from 2002 to 2003 in Terceira, one of the islands of the Azores archipelago in the north-eastern Atlantic. The atmospheric samples have been analysed for its carbonaceous content and for lipid class compounds. The major constituents that comprise plant wax are n-alkanes (C₂₃–C₃₃, with and odd-to-even carbon predominance and carbon maxima at 29 or 31), n-alkanols (C₂₂–C₃₀, even-to-odd) and n-alkanoic acids (C₂₂–C₃₀, even-to-odd), with minor amounts of n-alkanals and polycyclic biomarkers, such as phytosterols. Some alkanedioic acids and phthalates were also detected. The occurrence of short-chain homologues may indicate an additional marine source, probably introduced into the atmosphere via sea spray. Changes in the composition of the homologous series derived from terrestrial plants throughout the observation period may be related to alterations in the regional sources and transport pathways. These terrestrial lipids contributed up to 47% of the total compound mass, while the marine input was estimated to be inferior to 19%, both of them being more representative in summer. Biomass burning sources represented approximately 1% of the total inputs to the organic aerosol for the most part of the year, excepting during the spring, when it contributed to 10%. Petroleum products and plasticizers presented higher contributions (up to 19%) during the winter months. Secondary constituents resulting from oxidation during transport varied from 14% to 37% of the apportioned organic mass. The fraction derived from soil resuspension accounted for 2–16%.     

The solvent-extractable organic compounds in the Indonesia biomass burning aerosols – characterization studies

The large-scale air pollution episode due to the out-of-control biomass burning for agricultural purposes in Indonesia started in June 1997, has become a severe environmental problem for itself and the neighboring countries. The fire lasted for almost five months. Its impact on the health and ecology in the affected areas is expected to be substantial, costly and possibly long lasting. Air pollution Index as high as 839 has been reported in Malaysia. API is calculated based on the five pollutants: NO₂, SO₂, O₃, CO, and respirable suspended particulates (PM10). It ranges in value from 0 to 500. An index above 101 is considered to be unhealthy and a value over 201 is very unhealthy (Abidin and Shin, 1996).The solvent-extractable organic compounds from four total suspended particulate (TSP) high-volume samples collected in Kuala Lumpur, Malaysia (Stations Pudu and SIRIM) were subjected to characterization – the abundance was determined and biomarkers were identified. Two of the samples were from early September when the fire was less intense, while the other two were from late September when Kuala Lumpur experienced very heavy smoke coverage which could be easily observed from NOAA/AVHRR satellite images. The samples contained mainly aliphatic hydrocarbons such as n-alkanes and triterpanes, alkanoic acids, alkanols, and polycyclic aromatic hydrocarbons. The difference between the early and late September samples was very significant. The total yield increased from 0.6 to 24.3 μg m^-3 at Pudu and 1.9 to 20.1 μg m^-3 at SIRIM, with increases in concentration in every class. The higher input of vascular plant wax components in the late September samples, when the fire was more intense, was characterized by the distribution patterns of the homologous series n-alkanes, n-alkanoic acids, and n-alkanols, e.g., lower U : R, higher >C₂₂/<C₂₀ for n-alkanoic acids, higher >C₂₀/<C₂₀ for n-alkanols, a shift in C_max from C₁₆ to C₂₆ for n-alkanoic acids and C₁₈ to C₂₈ for n-alkanols, and the presence of abundant moretane (17β(H), 21α(H)-hopanes). The biomarkers dehydroabietic acid and retene were not found in the samples suggesting there is a difference in the long-distance transport samples of an Asian forest fire and the controlled experiments reported in the literature. Similar to the biomass burning in Amazonia (Abas et al., 1995), the present study also showed an absence of conifer tracers in the smoke aerosols indicating tropical wood sources. Abundant friedelin, a specific biomarker for smoke from oak wood fires (Standley and Simoneit, 1990), was present in the late September samples when the fire was more intense. The results were compared to literature values from an earlier study of the haze episode on 29 September 1991 in Kuala Lumpur, Malaysia (Abas and Simoneit, 1996).     

Particulate organic acids in the atmosphere of Italian cities: Are they environmentally relevant?

Mono- and dicarboxylic n-alkyl acids were extensively investigated in downtown Rome, Italy, and in Montelibretti, ～30 km NE of the city, during 2005–2007. Congeners ranging from lauric to mellisic, and from succinic to α,ω-docosanedioic acids were evaluated as well as phthalic, palmitoleic and oleic acids, by solvent extraction of airborne particulates followed by derivatization with propanol in the presence of boron trifluoride, and gas chromatographic-mass spectrometric analysis. Shorter measurements were made in Milan, in Taranto, at suburban and rural sites of Italy, and in the polar regions, from 1996 to 2005. The predominance of palmitic and stearic acids observed elsewhere was confirmed, and the behaviour of azelaic and phthalic acids resulted strongly dependent upon the year season. In the urban sites, among the long-chain compounds, the lignoceric acid was usually the most abundant, while the cerotic, montanic and mellisic homologues cumulatively never exceeded 8% of the total. Unlike other contaminants, the concentrations of organic acids remained fairly invariant over the last decade, suggesting that more attention must be paid to them in the future.     

Source apportionment of PAHs and n-alkanes in respirable particles in Tehran,Iran by wind sector and vertical profile

The vertical concentration profiles and source contributions of polycyclic aromatic hydrocarbons (PAHs) and n-alkanes in respirable particle samples (PM₄) collected at 10, 100, 200 and 300-m altitude from the Milad Tower of Tehran, Iran during fall and winter were investigated. The average concentrations of total PAHs and total n-alkanes were 16.7 and 591 ng/m³, respectively. The positive matrix factorization (PMF) model was applied to the chemical composition and wind data to apportion the contributing sources. The five PAH source factors identified were: ‘diesel’ (56.3 % of total PAHs on average), ‘gasoline’ (15.5 %), ‘wood combustion, and incineration’ (13 %), ‘industry’ (9.2 %), and ‘road soil particle’ (6.0 %). The four n-alkane source factors identified were: ‘petrogenic’ (65 % of total n-alkanes on average), ‘mixture of petrogenic and biomass burning’ (15 %), ‘mixture of biogenic and fossil fuel’ (11.5 %), and ‘biogenic’ (8.5 %). Source contributions by wind sector were also estimated based on the wind sector factor loadings from PMF analysis. Directional dependence of sources was investigated using the conditional probability function (CPF) and directional relative strength (DRS) methods. The calm wind period was found to contribute to 4.4 % of total PAHs and 5.0 % of total n-alkanes on average. Highest average concentrations of PAHs and n-alkanes were found in the 10 and 100 m samples, reflecting the importance of contributions from local sources. Higher average concentrations in the 300 m samples compared to those in the 200 m samples may indicate contributions from long-range transport. The vertical profiles of source factors indicate the gasoline and road soil particle-associated PAHs, and the mixture from biogenic and fossil fuel source-associated n-alkanes were mostly from local emissions. The smaller average contribution of diesel-associated PAHs in the lower altitude samples also indicates that the restriction of diesel-fueled vehicle use in the central area of Tehran has been effective in reducing the PAHs concentration.     

Sediment-associated aliphatic and aromatic hydrocarbons in coastal British Columbia, Canada: concentrations, composition, and associated risks to protected sea otters

Sediment-associated hydrocarbons can pose a risk to wildlife that rely on benthic marine food webs. We measured hydrocarbons in sediments from the habitat of protected sea otters in coastal British Columbia, Canada. Alkane concentrations were dominated by higher odd-chain n-alkanes at all sites, indicating terrestrial plant inputs. While remote sites were dominated by petrogenic polycyclic aromatic hydrocarbons (PAHs), small harbour sites within sea otter habitat and sites from an urban reference area reflected weathered petroleum and biomass and fossil fuel combustion. The partitioning of hydrocarbons between sediments and adjacent food webs provides an important exposure route for sea otters, as they consume ∼25% of their body weight per day in benthic invertebrates. Thus, exceedences of PAH sediment quality guidelines designed to protect aquatic biota at 20% of the sites in sea otter habitat suggest that sea otters are vulnerable to hydrocarbon contamination even in the absence of catastrophic oil spills.     

Aliphatic and aromatic hydrocarbons in different sized aerosols over the Mediterranean Sea: Occurrence and origin

Marine aerosols were collected using a five-stage cascade impactor during the PHYCEMED II cruise in the Western Mediterranean Sea (October 1983). Their composition in aliphatic and aromatic hydrocarbons (HCs) was analyzed, representing the first time that concentrations of polynuclear aromatic HCs (PAH) are reported in relation to particle size for aerosols of remote marine areas. The HC concentrations were found to be dependent on the origin of the air masses. They were higher for air coming from North European countries than for air originating in the Atlantic and the South of Spain. The concentrations range between 7 and 14 ng m⁻³for n-alkanes and between 0.2 and 0.4 ng m⁻³for total PAH. Based on molecular criteria, several sources for these HCs have been identified: continental higher plant waxes, petroleum and pyrolysis (namely coal combustion and vehicular exhausts). Mass medium equivalent diameters (MMED) for the naturally derived n-alkanes are in the 1.79-2.53 μm range, indicating an origin related with the emission of large particles from higher plant waxes or from soil dusts. In contrast, MMED for the anthropogenic HCs, both aliphatic and aromatic, are smaller than the micron, suggesting initial emission of PAH through pyrolytic processes in the vapor phase followed by condensation onto larger sub-μm particles.     

Air quality and organic compounds in aerosols from a coastal rural area in the Western Iberian Peninsula over a year long period: Characterisation,loads and seasonal trends

Ambient samples of fine organic aerosol collected from a rural area (Moitinhos) in the vicinity of the small coastal Portuguese city of Aveiro over a period of more than one year have been solvent-extracted and quantitatively characterised by gas chromatography–mass spectrometry. Particles were also analysed with a thermal-optical technique in order to determine their elemental and organic carbon content. In addition, meteorological sensors and real-time black carbon, ozone and carbon monoxide monitors were used. Particulate matter values were higher than background levels in continental Europe. A patent seasonal variation for organic and elemental carbon concentrations was observed, presumably related to stronger local primary emissions and to limited vertical dispersion. The higher levels were most likely a result of residential wood burning, since black carbon and carbon monoxide maximised during late evening hours in wintertime. Of the bulk of elutable organics, more than a half, on average, was present as acidic fraction. Alcohols, aliphatic and polyaromatic hydrocarbons represented together, more than 30% of the elutable mass, also showing a marked seasonal pattern with a minimum in summer and a maximum in winter. The winter increase was more evident for resinic acids, phytosterols, n-alkanoic acids and polycyclic aromatic hydrocarbons.     

Compositional change of organic matter in rainwater during precipitation events

Ten rain samples were collected at west Los Angeles, California, during two precipitation events. The samples were extracted with CH₂Cl₂ using a separatory funnel followed by continuous steam distillation extraction. Extracts were analyzed for n-alkanes, UCM of hydrocarbons, PAHs, FAs, benzoic acids and phenols using capillary gas chromatography (see Table 1 for definition of acronyms). The concentrations of some compounds decreased with time, whereas those of other compounds increased during the precipitation. Fluctuations of organic concentrations with time are interpreted as being due to washout effect and transient input of organic matter during the precipitation event. The major factor controlling the inputs is suggested to be wind which carries the organic constituents from biogenic and/or anthropogenic (motor vehicle) sources. These results indicate that the origins of air masses scavenged during a rain event may be traced by analysis of the organic constituents in the rain water.     

Covariations in the concentrations of organic compounds associated with springtime atmospheric aerosols

Organic compounds that can be thermally desorbed from airborne particles change cohesively with time, providing information about sources, photochemical transformations and transport of aerosols. In the spring of 1985, 138 airborne particulate samples were collected at an urban site in Boulder, Colorado. Samples were collected by drawing approximately 300 ℓ of air, for 58 min, through a small glass tube containing a quartz fiber filter. Particles were subsequently analyzed by direct thermal desorption of volatile organic compounds into a gas Chromatographic column followed by separation and detection of compounds with flame ionization or mass spectrometry. Factor analysis on the concentrations of 42 organic compounds in 138 1-h samples with time and meteorology revealed characteristic chromatograms for photochemical activity, biological sources and motor vehicle sources. Organic compounds desorbed from particles include terpenoids from biogenic sources, alkanes from vehicular and biological sources and aldehydes, ketones, carboxylic acids, lactones and furans from photochemical transformations and other sources. Concentrations of oxygenated species increased on sunny days relative to cloudy days or nights. Terpenoid concentrations increased when the wind direction was from a forested region west of the sampling site. Odd carbon number n-alkanes increased as temperature increased with the progression of springtime.     

Analysis of particle-associated semi-volatile aromatic and aliphatic hydrocarbons in urban particulate matter on a daily basis

PM_2.5 Particle-associated semi-volatile organic compounds (SVOC) were determined in the city of Augsburg, Germany. Daily samples were collected at a central monitoring station from late summer to late autumn 2002. The concentrations of polycyclic aromatic hydrocarbons (PAH), oxidized PAH (O-PAH), n-alkanes, hopanes and long chain linear alkylbenzenes were determined by direct thermal desorption-gas chromatography-time of flight mass spectrometry (DTD-GC-TOFMS). Additionally, PM_2.5 particle mass and number concentrations were measured. The sampling campaign can be divided into two parts, distinguished by a lower temperature level in the second part of the campaign. The particulate mass concentration showed no significant changes, whereas most of the SVOC had significant higher mean and peak concentrations in the colder period. The analysis of the data showed an increased influence of non-traffic sources in the colder period, reflected by a weak shift in the PAH profile and a significant shift in the hopane pattern. Statistical analysis of the inter-group correlations was carried out. Eight clusters partly representing different sources of the aerosol have been identified.     

Characterization of n-alkanes in PM2.5 of the Taipei aerosol

Ambient concentrations of n-alkanes with carbon number ranging from 17 to 36 were determined for PM_2.5 samples collected in Taipei city during September 1997–February 1998. The measured concentrations of particulate n-alkanes were in the range of 69–702 ng m⁻³, considerably higher than the concentration levels observed in Los Angeles and Hong Kong. The concentration distributions of n-alkanes homologues obtained in this study exhibited peaks at C₁₉, C₂₄ or C₂₅. This suggests that fossil fuel utilization, such as vehicular exhaust and lubricant residues, was an important contributor to the Taipei aerosol. Source apportionment of PM_2.5 was conducted using carbon preference index (CPI, defined as the ratio of the total concentration of particulate n-alkanes with odd carbon number to that with even carbon number) and U : R ratio (the concentration ratio of unresolved components to resolved components obtained from chromatograms). The low CPI value (0.9–1.9) and high U : R ratio (2.6–6.4) for each sample further confirmed that fossil fuel utilization was the major source of n-alkanes in ambient PM_2.5 of Taipei city. Estimates from these results showed that 69–93% of the n-alkanes in PM_2.5 of the Taipei aerosol originated from vehicular exhaust. The higher concentration level of particulate n-alkanes in the Taipei aerosol was mainly a result of vehicular emissions.