Estimation of biogenic volatile organic compounds emissions in subtropical island--Taiwan

Elevated tropospheric ozone is harmful to human health and plants. It is formed through the photochemical reactions involving volatile organic compounds (VOCs) and nitrogen oxides (NO(x)). The elevated ozone episodes occur mainly in summer months in the United States, while the high-ozone episodes frequently occur during the fall in Taiwan. The unique landscape of Taiwan produces tremendous amounts of biogenic VOCs in the mountain regions that are adjacent to concentrated urban areas. The urban areas, in turn, generate prodigious amounts of anthropogenic emissions. Biogenic VOC emissions have direct influence on tropospheric ozone formation. To explore the air quality problems in Taiwan, this study attempts to develop a biogenic VOC emission model suitable for air quality applications in Taiwan. The emission model is based on the Biogenic Emissions Inventory System Version 2 and coupled with a detailed Taiwan land use database. The 1999 total Taiwan biogenic VOC emissions were estimated at 214,000 metric tons. The emissions of isoprene, monoterpenes, and other VOCs were about 37.2%, 30.4%, and 32.4% of total biogenic VOC emissions, respectively. The annual total biogenic VOC emission per unit area was more than two times the value of that in any European country, implying that detailed emissions estimates in any size of region will benefit the global biogenic emission inventories.     

Biogenic emissions of isoprenoids and NO in China and comparison to anthropogenic emissions

In this study, a regional dynamical model (WRF) is used to drive biogenic emission models to calculate high resolution (10x10 km) biogenic emissions of isoprene (C(5)H(8)), monoterpenes (C(10)H(16)), and nitric oxide (NO) in China. This high resolution biogenic inventory will be available for the community to study the effect of biogenic emissions on photochemical oxidants in China. The biogenic emissions are compared to anthropogenic emissions to gain insight on the potential impact of the biogenic emissions on tropospheric chemistry, especially ozone production in this region. The results show that the biogenic emissions in China exhibit strongly diurnal, seasonal, and spatial variations. The isoprenoid (including both isoprene and monoterpenes) emissions are closely correlated to tree density and strongly vary with season and local time. During winter (January), the biogenic isoprenoid emissions are the lowest, resulting from lower temperature and solar radiation, and highest in summer (July) due to higher temperature and solar radiation. The biogenic NO emissions are also higher during summer and lower during winter, but the magnitude of the seasonal variation is smaller than the emissions of isoprene and monoterpenes. The biogenic emissions of NO are widely spread out in the northern, eastern, and southern China regions, where high-density agricultural soil lands are located. Both biogenic NO and isoprenoid emissions are very small in western China. The calculated total biogenic emission budget is smaller than the total anthropogenic VOC emission budget in China. The biogenic isoprenoid and anthropogenic VOC emissions are 10.9 and 15.1 Tg year(-1), respectively. The total biogenic and anthropogenic emissions of NO are 5.9 and 11.5 Tg(NO) year(-1), respectively. The study shows that in central eastern China, the estimated biogenic emissions of isoprenoids are very small, and the anthropogenic emissions of VOCs are dominant in this region. However, in northeastern and southern China, there are relatively large biogenic emissions of isoprenoids, leading to an important impact on the ozone production in these regions. Furthermore, the emissions of isoprenoids are highest during summer and noontime, which correlates to the peak of ozone production period. For example, the ratio between summer and winter for the emissions of isoprenoids is about 15 in China. As a result, the biogenic emissions of isoprenoids are significantly larger than the anthropogenic emissions of VOCs in China during daytime in summer. Biogenic NO emissions are mostly produced by agricultural soils which co-exist with large populations and human activity. As a result, the biogenic emissions of NO are mostly overlapped with the anthropogenic emissions of NO, leading to the enhancement in NO concentrations in the high anthropogenic NO emission regions. Finally, the future emissions of isoprene and monoterpenes over China are estimated. The results show that the future biogenic emissions may increase significantly due to land cover changes in central eastern China, which could have a very important impact on ozone formation in this region. However, these estimates are highly uncertain and are presented as a potential scenario to show the importance of possible changes of biogenic emissions in China.     

Estimating the biogenic emissions of non-methane volatile organic compounds from the North Western Mediterranean vegetation of Catalonia, Spain

An estimation of the magnitude of non-methane volatile organic compounds (NMVOCs) emitted by vegetation in Catalonia (NE of the Iberian Peninsula, Spain), in addition to their superficial and temporal distribution, is presented for policy and scientific (photochemical modelling) purposes. It was developed for the year 2000, for different time resolutions (hourly, daily, monthly and annual) and using a high-resolution land-use map (1-km2 squared cells). Several meteorological surface stations provided air temperature and solar radiation data. An adjusted mathematical emission model taking account of Catalonia's conditions was built into a geographic information system (GIS) software. This estimation uses the latest information, mainly relating to: (1) emission factors; (2) better knowledge of the composition of Catalonia's forest cover; and (3) better knowledge of the particular emission behaviour of some Mediterranean vegetal species. Results depict an annual cycle with increasing values in the March-April period with the highest emissions in July-August, followed by a decrease in October-November. Annual biogenic NMVOCs emissions reach 46.9 kt, with monoterpenes the most abundant species (24.7 kt), followed by other biogenic volatile organic compounds (e.g. alcohols, aldehydes and acetone) (16.3 kt), and isoprene (5.9 kt). These compounds signify 52%, 35% and 13%, respectively, of total emission estimates. Peak hourly total emission for a winter day could be less than 10% of the corresponding value for a summer day.     

Carbonyl compounds in gas and particle phases of mainstream cigarette smoke

Carbonyl compounds (carbonyls) are important constituents of cigarette smoke and some are toxic and may be carcinogenic or mutagenic to humans. In this study carbonyl emissions in the gas and particle phases of mainstream cigarette smoke were assessed by GC-MS with pentafluorophenyl hydrazine (PFPH) derivatization. Seven brands of cigarettes and one brand of cigar common in the UK market and having differing nicotine, tar and carbon monoxide yields were investigated. Sixteen carbonyl components were identified in gaseous emissions and twenty in the particle phase. In the gaseous emissions, acetaldehyde presented as the predominant species, followed by formaldehyde, 2-propenal, and pentanal. In the particulate emissions, 1-hydroxy-2-propanone was the most abundant followed by formaldehyde, benzaldehyde, and 2,5-dimethylbenzaldehyde. Significant differences were found in carbonyl emissions among the brands of cigarettes. The gaseous carbonyl emissions varied in the range of 216-405 μg cigarette⁻¹ (μg cig⁻¹) and the particulate carbonyl emissions varied in the range of 23-127 μg cig⁻¹. Positive correlations were found between the total emission of carbonyls, tar yield and carbon monoxide yield. Similar gas/particle (G/P) partitioning ratios of carbonyls were found among all cigarettes, which implies that G/P partitions of carbonyls in smoke mainly depend on the physical properties of the carbonyls. The gaseous carbonyl emissions were enhanced by 40% to 130% when some of the water, accounting for 8-12% of cigarettes in mass, was removed from the tobacco. Non-filtered cigarettes showed significantly higher carbonyl emissions compared to their filtered equivalents. Carbonyl particulate accounted for 11-19% by mass of total particulate matter from tobacco smoke. The cigar generated 806 μg cig⁻¹ gaseous and 141 μg cig⁻¹ particulate carbonyls, which is 2-4 times greater than the cigarettes.     

C3-C12 non-methane hydrocarbons in subtropical Hong Kong: spatial-temporal variations, source-receptor relationships and photochemical reactivity

Annual data on C3-C12 non-methane hydrocarbons (NMHCs) from different areas in Hong Kong are analyzed to examine the spatial distribution, seasonal variation, source-receptor relationships, and photochemical reactivity of NMHCs in subtropical Hong Kong. As expected, the highest levels of NMHCs were found at roadsides, and the lowest levels were observed at a rural site. For seasonal variations, the rural site showed the lowest NMHCs levels in summer, but the roadside site gave a different picture, with the highest NMHCs levels in summer. This was believed to be due to the strong evaporation of alkanes in the hot season. With the exception of isoprene, NMHCs levels in Hong Kong were generally low compared to those of other overseas cities. Principal component analysis suggested that while the isoprene at the rural site mainly came from biogenic emissions, vehicular emissions were the major source in the urban areas, especially at roadsides. Ratios of hydrocarbons with different reactivities were also analyzed to evaluate the ages of air masses and emission ratios. A high toluene-to-benzene ratio at roadsides was due to the widespread use of aromatic-rich unleaded fuels in Hong Kong. The ratios of total NMHCs to nitrogen oxides were found to be 2 to 10 (ppbC/ppbv) indicating that the formation of photochemical ozone (O3) in Hong Kong is controlled by the levels of NMHCs. The reactivity of hydroxyl radicals (OH) and O3 formation potential of NMHCs were evaluated using the propene-equivalent concentration and maximum incremental reactivity. Isoprene was found to have the highest OH-reactivity and O3 formation potential at the rural site, while toluene was the most important contributor to the two parameters at the roadside site. These results are valuable for the understanding of O3 pollution in Hong Kong and the formulation of an effective strategy to manage O3.     

Indoor and outdoor carbonyl compounds and BTEX in the hospitals of Guangzhou, China

Indoor and outdoor concentration levels of 21 carbonyl compounds and five BTEX (benzene, toluene, ethylbenzene and xylenes) were measured in four hospitals of Guangzhou from 2nd January to 20th March 2004. Samples were collected in five consecutive daytimes for each hospital. Among most of the samples, acetone was the most abundant carbonyl, followed by acetaldehyde, 2-butanone or formaldehyde. Toluene was the most abundant BTEX and the others were at similar levels. The relatively higher acetone concentrations might have resulted from the high level of background in Guangzhou area due to emission of the factories and LPG-fuel vehicles, and also for the special weather conditions during sampling time. The high concentration of acetaldehyde, which was even higher than that of formaldehyde, might be resulted from the wide use of ethanol in hospital. The partial oxidation of ethanol may form acetaldehyde. The indoor concentrations of carbonyls and BTEX were found a little higher than their outdoor counterparts with only a few exceptions, which showed the anthropogenic sources for these compounds. The low correlations between most carbonyls and BTEX concentrations might be caused by their complex sources. Finally, the human exposure levels of formaldehyde and acetaldehyde in hospitals are discussed.     

The biogenic volatile organic compounds emission inventory in France: application to plant ecosystems in the Berre-Marseilles area (France)

An inventory describing the fluxes of volatile organic compounds (VOCs), isoprene and monoterpenes, and other VOCs (OVOCs) from the biosphere to the atmosphere, has been constructed within the framework of the ESCOMPTE project (fiEld experimentS to COnstrain Models of atmospheric Pollution and Transport of Emissions). The area concerned, located around Berre-Marseilles, is a Mediterranean region frequently subject to high ozone concentrations. The inventory has been developed using a fine scale land use database for the year 1999, forest composition statistics, emission potentials from individual plant species, biomass distribution, temperature and light intensity. The seasonal variations in emission potentials and biomass were also taken into account. Hourly meteorological data for 1999 were calculated from ALADIN data and these were used to predict the hourly isoprene, monoterpene and OVOC fluxes for the area on a 1 kmx1 km spatial grid. Estimates of annual biogenic isoprene, monoterpene and OVOC fluxes for the reference year 1999 were 20.6, 38.9 and 13.3 kt, respectively, Quercus pubescens, Quercus ilex, Pinus halepensis and garrigue vegetation are the dominant emitting species of the area. VOC emissions from vegetation in this region contribute approximately 94% to the NMVOC (non-methane volatile organic compounds) of natural origin and are of the same order of magnitude as NMVOC emissions from anthropogenic sources. These results complete the global ESCOMPTE database needed to make an efficient strategy for tropospheric ozone reduction policy.     

Characterisation of NMHCs in a French urban atmosphere: overview of the main sources

Continuous hourly air quality data involving 37 C2-C9 non-methane hydrocarbons (NMHC) over 4 years are reported for the first time in Lille metropol, northern France, at two urban roadside and background sites. The data have been analysed in two complementary steps: univariate statistics which define the spatial and temporal characteristics of NMHC by constructing the seasonal and daily concentration profiles, and multivariate statistics based on principal component analysis (PCA). A number of important sources have been clearly identified depending on the season: (1) motor vehicle exhaust, which dominates the NMHC distribution and particularly in winter, even for isoprene; (2) wintertime stationary combustion and activities related to fossil fuel consumption in general, such as natural gas leakage of ethane and propane; (3) summertime evaporative emissions from fuel and solvent; and (4) summertime biogenic emissions through isoprene behaviour and their dependence on temperature.     

Biogenic volatile organic compounds (BVOCs) emissions from Abies alba in a French forest

Air quality studies need to be based on accurate and reliable data, particularly in the field of the emissions. Biogenic emissions from forests, crops, and grasslands are now considered as major compounds in photochemical processes. Unfortunately, depending on the type of vegetation, these emissions are not so often reliably defined. As an example, although the silver fir (Abies alba) is a very widespread conifer tree in the French and European areas, its standard emission rate is not available in the literature. This study investigates the isoprene and monoterpenes emission from A. alba in France measured during the fieldwork organised in the Fossé Rhénan, from May to June 2003. A dynamic cuvette method was used. Limonene was the predominant monoterpene emitted, followed by camphene, alpha-pinene and eucalyptol. No isoprene emission was detected. The four monoterpenes measured showed different behaviours according to micrometeorological conditions. In fact, emissions of limonene, alpha-pinene and camphene were temperature-dependant while eucalyptol emissions were temperature and light dependant. Biogenic volatile organic compounds emissions were modeled using information gathered during the field study. Emissions of the three monoterpenes previously quoted were achieved using the monoterpenes algorithm developed by Tingey et al. (1980) [Tingey D, Manning M, Grothaus L, Burns W. Influence of light and temperature on monoterpene emission rates from slash pine. Plant Physiol 1980;65: 797-801.] and the isoprene algorithm [Guenther, A., Monson, R., Fall, R., 1991. Isoprene and monoterpene emission rate variability: observations with eucalyptus and emission rate algorithm development. J Geophys Res 26A: 10799-10808.]; [Guenther, A., Zimmerman, P., Harley, P., Monson, R., Fall, R., 1993. Isoprene and monoterpene emission rate variability: model evaluation and sensitivity analysis. J Geophys Res 98D: 12609-12617.]) was used for the eucalyptol emission. With these methods, simulation results and observations agreed fairly well. The standard emission rate (303 K) and beta-coefficient averaged for limonene, camphene and alpha-pinene were respectively of 0.63 microg gdw-1 h-1 and 0.06 K-1. For eucalyptol, the standard emission rate (T=303 K and PAR=1000 micromol m-2 s-1) was 0.26 microg gdw-1 h-1. This classified A. alba as a weak monoterpenes emitter.     

Volatile organic compound measurements in the California/Mexico border region during SCOS97

Measurements of volatile organic compounds (VOC) were carried out in the California/Mexico border region during the Southern California Ozone Study in the summer of 1997 (SCOS97). Integrated 3-h samples were collected in Rosarito (south of Tijuana, Mexico) and in Mexicali during intensive operational periods (IOP), twice per IOP day. VOC were collected using stainless-steel 6-1 canisters; carbonyl compounds were collected using 2,4-dinitrophenyl-hydrazine (DNPH) impregnated C18 SepPak cartridges. The canister samples were analyzed for speciated volatile hydrocarbons (C2-C12), CO, CO2, CH4, methyl t-butyl ether (MTBE), and halogenated hydrocarbons. DNPH-impregnated cartridges were analyzed for 14 C1-C7 carbonyl compounds. The concentrations of all species were higher at Mexicali than in Rosarito. A good correlation between total non-methane hydrocarbons (TNMHC), CO, and other pollutants associated with motor vehicle emissions observed for Mexicali indicates that the main source of TNMHC at this site is vehicular traffic.     

Seasonal and diurnal variations of carbonyl compounds in the urban atmosphere of Guangzhou, China

Seasonal and diurnal variations of carbonyl compounds were investigated at two sampling sites (Liwan and Wushan) in the ambient air of Guangzhou, China. Air samples were collected during 2005 from January to November, and carbonyl compounds were analyzed with HPLC. The results show that carbonyls exhibit distinct seasonal variation. The total concentrations of 21 carbonyls detected ranged from 2.64 to 103.6 μg m⁻³ at Liwan and from 5.46 to 89.9 μg m⁻³ at Wushan, respectively. The average total concentrations of carbonyls at both Liwan and Wushan decreased in order of summer>spring>autumn>winter. Formaldehyde, acetaldehyde, and acetone were the most abundant carbonyl compounds, which accounted for more than 60% of the total concentrations of carbonyls. The mean concentration ratios of summer/winter were all > 1.0 for the total concentrations and the individual carbonyl compound. The diurnal variation of carbonyls was not distinct in this study. The average concentration ratios of formaldehyde/acetaldehyde (C₁/C₂) varied from 0.71 to 1.32 and 0.65 to 1.14 at Liwan and Wushan, respectively, and the average concentration ratios of acetaldehyde/propionaldehyde (C₂/C₃) varied from 5.42 to 7.70 and 5.02 to 13.9 in Liwan and Wushan, respectively. Regarding photochemical reactivity of carbonyls and the ozone production, acetaldehyde, butyraldehyde, formaldehyde, and valeraldehyde account for 75-90% to the total propene-equivalent concentrations, while formaldehyde, acetaldehyde, valeraldehyde, butyraldehyde, and propionaldehyde contribute 89-96% to the total ozone formation potentials (ranging from 105 to 274 μg m^-3). The ozone formation potentials in summer were higher by 1-2 times than those in the other seasons.     

Analysis of indoor particles and gases and their evolution with natural ventilation

The air composition and reactivity from outdoor and indoor mixing field campaign was conducted to investigate the impacts of natural ventilation (ie, window opening and closing) on indoor air quality. In this study, a thermal desorption aerosol gas chromatograph (TAG) obtained measurements of indoor particle‐ and gas‐phase semi‐ and intermediately volatile organic compounds both inside and outside a single‐family test home. Together with measurements from a suite of instruments, we use TAG data to evaluate changes in indoor particles and gases at three natural ventilation periods. Positive matrix factorization was performed on TAG and adsorbent tube data to explore five distinct chemical and physical processes occurring in the indoor environment. Outdoor‐to‐indoor transport is observed for sulfate, isoprene epoxydiols, polycyclic aromatic hydrocarbons, and heavy alkanes. Dilution of indoor species is observed for volatile, non‐reactive species including methylcyclohexane and decamethylcyclopentasiloxane. Window opening drives enhanced emissions of semi‐ and intermediately volatile species including TXIB, DEET, diethyl phthalate, and carvone from indoor surfaces. Formation via enhanced oxidation was observed for nonanal and 2‐decanone when outdoor oxidants entered the home. Finally, oxidative depletion of gas‐phase terpenes (eg, limonene and α‐pinene) was anticipated but not observed due to limited measurement resolution and dynamically changing conditions.     

Nonmethane hydrocarbon measurements at a suburban site in Changsha City, China

The concentration, composition, and variability of nonmethane hydrocarbons (NMHCs) and carbon monoxide (CO) were characterized in a suburban region of south-central China. Weekly samples were collected in 2007 in the Changsha suburban area and analyzed with a three-stage preconcentration method coupled with GC-MS. A time series of NMHC measurements showed seasonal variation, with a higher level occurring in winter and a lower level in summer. Toluene was the most abundant species with an average concentration of 2.51 ± 1.87 ppbv, followed by benzene (2.04 ± 1.30 pptv). According to the level of identified NMHCs, vehicular exhaust appears to be the main source of NMHCs in Changsha. Among alkanes, the highest level is propane with a concentration of 1.31 ± 0.71 ppbv, it indicated an extensive use and leakage of liquefied petroleum gas (LPG) in Changsha. The concentrations of NMHCs were influenced by the wind direction; a high level of NMHCs was carried by winds from southern China. Significant biogenic isoprene emissions were observed, with good correlation between isoprene level and temperature. Finally, when the typical individual NMHC species and CO in the morning and afternoon were compared, the shorter lifetime of NMHC species relative to CO could explain the poorer correlation observed in the afternoon.     

Atmospheric volatile organic compound measurements during the 1996 Paso del Norte Ozone Study

Ambient air VOC samples were collected at surface air quality monitoring sites, near sources of interest, and aloft on the US (El Paso) and Mexican (Ciudad Juárez) side of the border during a six-week period of the 1996 Paso del Norte Ozone Study. Samples were collected at five sites, three on the US side and two on the Mexican side, during nine intensive operation days when high ozone levels were forecast for the area. Six other sites were sampled to characterize up-wind, down-wind and other emission sources. Samples for determining source profiles were collected for rush hour traffic, propane-powered bus exhaust, automobile paint shop emissions, propane fuels, and industrial manufacturing in Cd. Juárez and a refinery in El Paso. Most samples were collected in electro-polished stainless steel canisters for determination of C2 to C(10+) hydrocarbons by GC-FID. Carbonyl samples were collected on DNPH impregnated cartridges at three surface sites during aircraft flights and analyzed by HPLC. This paper presents the spatial and temporal characteristics of VOC species concentrations and compositions to examine the differences and similarities of the various locations and time periods. Overall surface, total non-methane hydrocarbon values ranged from 0.1 to 3.4 ppmC with the highest concentrations being recorded in the morning and evening at five vehicle-dominated sites, three in Cd. Juárez and two in El Paso. Toluene in El Paso samples and propane, which is used as a cooking and transportation fuel in Cd. Juárez, were the most abundant hydrocarbons. The most abundant carbonyls were acetaldehyde, acetone and formaldehyde.     

Biodiesel emissions profile in modern diesel vehicles. Part 2: Effect of biodiesel origin on carbonyl, PAH, nitro-PAH and oxy-PAH emissions

In the present study, the effects of different biodiesel blends on the unregulated emissions of a Euro 4 compliant passenger car were examined. Two fresh and two oxidized biodiesel fuels of different source materials were blended with an ultra low sulphur automotive diesel fuel at proportions of 10, 20, and 30% v/v. Emission measurements were conducted on a chassis dynamometer with a constant volume sampling (CVS) technique, over the New European Driving Cycle (NEDC) and the Artemis driving cycles. The experimental results revealed that the addition of biodiesel led to important increases in most carbonyl compounds. Sharp increases were observed with the use of the oxidized biodiesel blends, especially those prepared from used frying oil methyl esters. Similar to carbonyl emissions, most PAH compounds increased with the addition of the oxidized biodiesel blends. It can be assumed that the presence of polymerization products and cyclic acids, along with the degree of unsaturation were the main factors that influenced carbonyl and PAH emissions profile.     

Lipophilic organic compounds in lake sediment and American coot (Fulica americana) tissues,both affected and unaffected by avian vacuolar myelinopathy

Avian vacuolar myelinopathy (AVM) is a disease of unknown etiology, which has been diagnosed in a variety of birds from surface water reservoirs in the southeastern United States. Pathology suggests a natural or anthropogenic compound may be the cause of this disease. With the goal of identifying the toxicant that causes AVM, we qualitatively analyzed sediments and American coot (Fulica americana) tissues from reservoirs that were affected and unaffected by AVM using high-resolution gas chromatographic low-resolution mass spectrometry. Polychlorinated biphenyls (PCBs), octachlorodibenzo-p-dioxin, and biogenic and anthropogenic polycyclic aromatic hydrocarbons (such as retene) were the most abundant compounds in the sediment. Penta- and hexachlorobenzene, oxychlordane, p,p'-DDE, dieldrin, and polychlorinated biphenyls were the most abundant compounds in the avian tissues. None of these compounds were more abundant in the AVM affected sediments and tissues than in the unaffected media. Therefore, it is unlikely that any of these compounds are the cause of this avian disease.     

Emission comparison of urban bus engine fueled with diesel oil and 'biodiesel' blend

The chemical and toxicological characteristics of emissions from an urban bus engine fueled with diesel and biodiesel blend were studied. Exhaust gases were produced by a turbocharged EURO 2 heavy-duty diesel engine, operating in steady-state conditions on the European test 13 mode cycle (ECE R49). Regulated and unregulated pollutants, such as carcinogenic polycyclic aromatic hydrocarbons (PAHs) and nitrated derivatives (nitro-PAHs), carbonyl compounds and light aromatic hydrocarbons were quantified. Mutagenicity of the emissions was evaluated by the Salmonella typhimurium/mammalian microsome assay. The effect of the fuels under study on the size distribution of particulate matter (PM) was also evaluated. The use of biodiesel blend seems to result in small reductions of emissions of most of the aromatic and polyaromatic compounds; these differences, however, have no statistical significance at 95% confidence level. Formaldehyde, on the other hand, has a statistically significant increase of 18% with biodiesel blend. In vitro toxicological assays show an overall similar mutagenic potency and genotoxic profile for diesel and biodiesel blend emissions. The electron microscopy analysis indicates that PM for both fuels has the same chemical composition, morphology, shape and granulometric spectrum, with most of the particles in the range 0.06-0.3 microm.     

Origins of n-alkanes, carbonyl compounds and molecular biomarkers in atmospheric fine and coarse particles of Athens, Greece

The abundance and origin of aliphatic hydrocarbons, carbonyl compounds and molecular biomarkers found in the aliphatic fraction of PM_10-2.5 and PM_2.5 in the centre of Athens Greece are discussed in an attempt to reveal seasonal air pollution characteristics of the conurbation. Each extract was fractionated into individual compound classes and was analyzed using gas chromatography coupled to mass spectrometry. Normal alkanes, ranging from C₁₄ to C₃₅, were abundant in PM_10-2.5 and PM_2.5 samples during both sampling campaigns. The daily concentration of total n-alkanes was up to 438 ng m^− 3 for PM_10-2.5 and up to 511 ng m^− 3 for PM_2.5. Additionally, gaseous concentrations of n-alkanes were calculated, revealing that the relative proportions between gaseous and particle phases of individual compounds may differ significantly between summer and late winter. Normal alkanals and alkan-2-ones were only detected in the fine fraction of particulate matter and their concentrations were much lower than the n-alkane concentrations. Several geochemical parameters were used to qualitatively reconcile the sources of organic aerosol. The carbon preference index (CPI) of the coarse particles in August had the highest value, while in March the leaf wax contribution decreased significantly and the CPI value was very close to unity for both sites. Maximum concentrations of carbonyl compounds were reported in the range of C₁₅-C₂₀, demonstrating that they were formed from anthropogenic activity or from atmospheric oxidative processes. 6, 10, 14-trimethylpentadecan-2-one, a marker of biogenic input, was also detected in our samples. Molecular biomarker compounds confirmed that ca. 60% of the aliphatic fraction on the sampled atmospheric particles originated from petroleum and not from any contemporary biogenic sources. Pristane and phytane were detected in the fine fraction with their presence indicating sources of fossil fuel in the range of C₁₆-C₂₀. At all sites the 17α(Η),21β(Η) hopane series was the most abundant hopane group.     

Organic compounds of PM2.5 in Mexico Valley: spatial and temporal patterns, behavior and sources

A longitudinal study on spatial and temporal behavior of particles less than 2.5 μm (PM_2.5), solvent extracted organic matter (SEOM), polycyclic aromatic hydrocarbons (PAH), n-alkanes and nitro-PAH was carried out for a full year in 2006, at five sites simultaneously around the Metropolitan Zone of Mexico Valley (MZMV). There is rather uniform distribution of PM_2.5 and SEOM in the MZMV regarding gravimetric mass concentration, while some specific organic chemical components showed mass heterogeneity. The highest mass concentrations of target compounds occurred in the dry seasons with respect to the rainy season. Bonfires and fireworks are probably responsible for extreme values of PM_2.5, SEOM and PAH (≥ 228 g mol^− 1). Benzo[ghi]perylene was the most abundant PAH, with C₂₄-C₂₆ the most abundant n-alkanes and 2-nitrofluoranthene and 9-nitroanthracene the most abundant nitro-PAH. The northeast zone was the area with the greatest presence of sources of incomplete diesel combustion, while the central for gasoline combustion. In the southwest, the biogenic sources were more abundant over the anthropogenic sources. This was opposite to the other sites. Factor analysis allowed us to relate different compounds to emitting sources. Three main factors were associated with combustion, pyrolysis and biogenic primary sources while the other factors were associated with secondary organic aerosol formation and industry. Correlation analyses indicated that SEOM originates from different primary emission sources or is formed by different processes than the other variables, except in southwest. Associations among variables suggest that PM_2.5 in the northwest and in the southeast originated mainly from primary emissions or consisted of primary organic compounds. PM_2.5 in the northeast, central and southwest contains a greater proportion of secondary organic compounds, with the less oxidized organic aerosols in the northeast and the most aged organic aerosol in the southwest. This follows the trends in the prevailing wind directions in MZMV during 2006.     

Polycyclic aromatic hydrocarbons: levels and phase distributions in preschool microenvironment

This work aims to characterize levels and phase distribution of polycyclic aromatic hydrocarbons (PAHs) in indoor air of preschool environment and to assess the impact of outdoor PAH emissions to indoor environment. Gaseous and particulate (PM₁ and PM_2.5) PAHs (16 USEPA priority pollutants, plus dibenzo[a,l]pyrene, and benzo[j]fluoranthene) were concurrently sampled indoors and outdoors in one urban preschool located in north of Portugal for 35 days. The total concentration of 18 PAHs (ΣPAHs) in indoor air ranged from 19.5 to 82.0 ng/m³; gaseous compounds (range of 14.1–66.1 ng/m³) accounted for 85% ΣPAHs. Particulate PAHs (range 0.7–15.9 ng/m³) were predominantly associated with PM₁ (76% particulate ΣPAHs) with 5‐ring PAHs being the most abundant. Mean indoor/outdoor ratios (I/O) of individual PAHs indicated that outdoor emissions significantly contributed to PAH indoors; emissions from motor vehicles and fuel burning were the major sources.