Atmospheric Environment (v.42, #1)

Air pollution in mega cities in China by Chak K. Chan; Xiaohong Yao (1-42).
Due to its rapidly expanding economic and industrial developments, China is currently considered to be the engine of the world's economic growth. China's economic growth has been accompanied by an expansion of the urban area population and the emergence of a number of mega cities since the 1990. This expansion has resulted in tremendous increases in energy consumption, emissions of air pollutants and the number of poor air quality days in mega cities and their immediate vicinities. Air pollution has become one of the top environmental concerns in China. Currently, Beijing, Shanghai, and the Pearl River Delta region including Guangzhou, Shenzhen and Hong Kong, and their immediate vicinities are the most economically vibrant regions in China. They accounted for about 20% of the total GDP in China in 2005. These are also areas where many air pollution studies have been conducted, especially over the last 6 years. Based on these previous studies, this review presents the current state of understanding of the air pollution problems in China's mega cities and identifies the immediate challenges to understanding and controlling air pollution in these densely populated areas.
Keywords: Air quality; O3; PM2.5; PM10; Dust storm; Beijing; Shanghai; Hong Kong; Guangzhou;

Nitrated and oxygenated derivatives of polycyclic aromatic hydrocarbons in the ambient air of two French alpine valleys by A. Albinet; E. Leoz-Garziandia; H. Budzinski; E. Villenave; J.-L. Jaffrezo (43-54).
Ambient measurements (gas+particle phases) of 16 polycyclic aromatic hydrocarbons, 17 nitrated PAHs (NPAHs) and eight oxygenated PAHs (OPAHs) were carried out during the winter 2002–2003 and the summer 2003 in two French alpine valleys on various types of sites (traffic, sub-urban, altitude and rural). Atmospheric concentrations of these classes of compounds are of interest because they include potential mutagens and carcinogens. During both summer and winter campaigns, OPAH concentration levels were of the same order of magnitude as PAH ones while NPAH concentrations were one to two orders of magnitude lower. Total particulate PAH, OPAH and NPAH concentrations were higher in the Chamonix valley than in the Maurienne valley. A heavier pollutant accumulation process in the Chamonix valley and geomorphology promoting their dispersion seem to explain such differences. Despite reaching lower atmospheric concentrations, NPAHs seemed to account up to 20% of carcinogenic potency of particulates collected at the sites away from pollution sources. The formation of secondary compounds such as NPAHs increases significantly the carcinogenic risk at the sites away from pollution sources. Study with 2-nitrofluoranthene/1-nitropyrene ratio showed that NPAH gas phase formation was hindered in winter, and when relative contribution from primary sources was higher. Nevertheless, in winter under specific conditions, evidence of secondary NPAH formations was observed at sub-urban and traffic sites (snowfalls) and rural site (accumulation of pollutants and snowfalls). For all sampling sites, the daytime OH initiated reaction seemed to be the dominant gas phase formation pathway over the NO3 initiated reaction. The fraction of PAHs, OPAHs and NPAHs associated with the particle phase was strongly depending on their vapour pressure and the ambient conditions.
Keywords: Polycyclic aromatic hydrocarbons; Nitrated polycyclic aromatic hydrocarbons; Oxygenated polycyclic aromatic hydrocarbons; Atmospheric pollution; POVA (Pollution des Vallées Alpines); Alpine valleys;

The size distribution of polycyclic aromatic hydrocarbons (PAHs) and PAH derivatives was determined during the intensive sampling campaigns of the POVA (Pollution des Vallées Alpines) research programme, in two French alpine valleys, in winter and summer. The size distributions of PAHs, oxygenated PAHs (OPAHs) and nitrated PAHs (NPAHs) present large variations with year time and site type (traffic; suburban and rural). In general, these compounds were mainly associated (60–90%) with fine particles (D p<1.3 μm) in agreement with their release from sources (primary and/or secondary). The pollutant distributions with particle size were unimodal and centred at 0.85 μm both in the Chamonix and Maurienne valleys. The summer size distribution of NPAHs was centred at D p=2.75 μm. PAH, OPAH and NPAH super micrometre fractions were significantly larger in summer for most sites suggesting the existence of a second mode in that particle size range. A possible reason to explain this phenomenon is that aerosol was locally polluted and characterised by fine particles in winter whereas in summer, aerosol was more mixed and older with possibilities of adsorption of gaseous organic compounds at the surface of the pre-exiting particles. In summer, NPAHs were associated to a greater degree with the super micrometre fraction of the aerosol than the other categories of compounds.
Keywords: Polycyclic aromatic hydrocarbons; Nitrated polycyclic aromatic hydrocarbons; Oxygenated polycyclic aromatic hydrocarbons; Size distribution; Atmospheric pollution; POVA (Pollution des Vallées Alpines); Alpine valleys;

In this paper, the OSPM model is employed for the calculation of the PM10 concentration levels in the historical centre of the city of Thessaloniki (Greece). Although measurements of the background concentration are available at a suburban station, and a few measurements of PM10 concentrations do exist at particular areas inside the historical city centre, further assumptions had to be made (e.g., for the traffic load) in order to implement OSPM. To validate this approach, NO x and NO2 measurements were employed in addition to data for PM10. The good agreement observed allowed the prediction of PM10 concentrations in all streets in the historical city centre. The very high PM10 concentration levels obtained in almost all streets are indicative of the city's situation today. Finally, developments in vehicle's technology are invoked to model possible future scenarios.
Keywords: OSPM; PM10; Pollution; Traffic;

In- and outdoor sources of polybrominated diphenyl ethers and their human inhalation exposure in Guangzhou, China by Laiguo Chen; Bixian Mai; Zhencheng Xu; Xiaochun Peng; Jinglei Han; Yong Ran; Guoying Sheng; Jiamo Fu (78-86).
The indoor (home and workplace) and outdoor concentrations of the sum of 10 polybrominated diphenyl ethers (PBDEs), designated Σ10PBDEs (-28, -47, -66, -100, -99, -85, -154, -153, -138, -183), and BDE-209 were measured using high-volume air samplers in Guangzhou from October 2004 to April 2005. The Σ10PBDEs and BDE-209 concentration ranges were 125.1–2877 and 39–11,468 pg m−3, respectively for home air, 181.3–8315 and 80.1–13,732 pg m−3 for office air, 322.1–2437 and 73.1–8194 pg m−3 for air in other workplaces, and 203.2–2426 and 1082–49,937 pg m−3 for outdoor air. The levels of PBDEs in domestic and workplace environments are similar to those reported in others studies. However, the open-air values reported here are significantly higher than those found elsewhere. The dominant congeners observed in indoor air samples were those associated with penta-BDE and deca-BDE commercial mixtures. Our study also indicates that the primary indoor emission sources for PBDEs in Guangzhou are originated from the relatively old electronic/electrical appliances, especially computers, but not the PUF-containing furniture. The median daily human exposures to Σ10PBDEs and BDE-209 via inhalation in Guangzhou are 12.4 and 15.1 ng day−1  person−1, respectively. The human inhalation exposure to Σ10PBDEs is higher than reported in two other studies (6.9 and 2.0 ng day−1  person−1) presumably due to the larger number of compounds considered in this study as well as the higher outdoor concentrations of PBDEs.
Keywords: Polybrominated diphenyl ethers (PBDEs); Indoor air; Inhalation exposure;

This study investigates the effects of reductions in nitrogen oxide (NO x ) emissions from major point sources on daily maximum 8-h ozone concentrations in the eastern United States. The Community Multiscale Air Quality (CMAQ) model was utilized in photochemical simulations on a matrix of modeling scenarios permitting an examination of the separate effects of emission changes and meteorological influences on maximum ozone levels over a 3-month period during the summers of 2002 and 2004. Two modeling scenarios involved base case 2002 emissions and post-control emissions, reflecting the point source NO x emission reductions implemented before the ozone season of 2004, using summer 2002 meteorological conditions. Results revealed that point source NO x emission reductions caused decreases in daily maximum 8-h ozone concentrations over the eastern United States. At the 50th and 95th percentiles of the cumulative frequency distribution, daily maximum 8-h ozone values in the emission reduction scenario were lower than corresponding base case values over 70% and 90% of the modeling domain, respectively. During southwesterly wind flows across the Ohio River Valley, morning ozone concentrations aloft were lower over northeastern states downwind of the emissions-rich region in the NO x reduction scenario results. Another notable feature of the NO x emission reduction scenario results is that greater decreases in daily maximum 8-h ozone occurred at higher concentrations. Results from other modeling scenarios revealed strong differences in meteorological conditions between these two summer periods greatly impacted the daily 8-h maximum ozone concentrations with the meteorological effects on ozone being greater than those from emission changes over the northern part of the modeling domain. Using backtrajectory analysis, greater percentage decreases in daily maximum 8-h ozone occurred at monitoring sites when they were downwind of the Ohio River Valley, which is a notable emission source region, as compared to cases when the sites were not downwind of it.
Keywords: Photochemical ozone; NO x emission reductions; CMAQ; HYSPLIT; Trajectory analysis;

A study of wood burning and traffic aerosols in an Alpine valley using a multi-wavelength Aethalometer by J. Sandradewi; A.S.H. Prévôt; E. Weingartner; R. Schmidhauser; M. Gysel; U. Baltensperger (101-112).
We present a study of aerosol light absorption using a multi-wavelength Aethalometer (λ=370–950 nm) in an Alpine valley where the major local emissions of aerosols in winter are from domestic wood burning and traffic. The measurements were done in winter and summer periods in 2004 and 2005. Much stronger diurnal trends in CO, NO x and aerosol light absorption parameters were observed in winter than in summer. The average (±1 S.D.) PM10 concentrations measured at this site were 31.5±21.7 μg m−3 in winter and 15.8±10.0 μg m−3 in summer. The highest PM10 concentrations were observed between 18:00 and 22:00 h CET in both campaigns, with 45.4±21.0 μg m−3 for winter and 21.0±9.5 μg m−3 for summer. The average (±1 S.D.) power law exponents of the absorption coefficients (also called absorption exponent) with λ=370–950 nm, α 370–950 nm were 1.6±0.25 in winter and 1.1±0.05 in summer. The calculation of α separately for lower and higher wavelengths (i.e., α 370–520 nm and α 660–950 nm) provided a better description of the wavelength dependence from the UV- to the near-IR region. The highest mean values of α 370–520 nm and α 660–950 nm were observed between 22:00 and 02:00 h CET in winter with 2.7±0.4 and 1.3±0.1, respectively. Comparison of α 370–520 nm with CO and NO x data indicated that the relative contribution of wood burning versus traffic was responsible for the seasonal and diurnal variability of α. The seasonal and diurnal trends of α were not attributed to changes in the particle size since the aerosol volume size distributions (dV/d log  D) were found to be similar in both campaigns.
Keywords: Aethalometer; Absorption coefficients; Absorption exponent; Wood burning; Emission;

To evaluate the influence of vehicle exhaust particles on the urban atmosphere, atmospheric aerosols collected in the general environment and at a trunk road sampling site in the Tokyo metropolitan area were analyzed for carbonaceous and ionic components. Samples were collected as fine (<2.1 μm) and coarse particle (2.1–7.0 μm) from April 2003 to March 2004 using low-volume Andersen sampler. The carbonaceous components were analyzed by a thermal method and a thermal/optical method. Elemental carbon (EC) determined by thermal method was higher than those by thermal/optical method, and slope of linear regression of the thermal method versus the thermal/optical method differed at both sampling points. These results suggested possible analytical artifacts, a difference in the composition of the carbonaceous components of the aerosols, or both. The EC concentrations in fine particles in the roadside were higher than in the general environment by 5 μg m−3, and it was accounted for 68% of the difference of the mass concentration. The mass concentration reconstructed by the mass closure model using element analysis results corresponded more closely to the observed mass concentration in the general environment samples than in the roadside samples. It is suggested that the contribution of the organic compounds in the roadside particles was underestimated. Diesel vehicle emission control regulations implemented in October 2003 seem to have had an effect because there was a significant difference in the average concentration of suspended particulate matter and NO x before and after implementation of the regulations. Moreover, the EC/TC ratio has been decreasing over time.
Keywords: Elemental carbon; Organic carbon; Thermal/optical method; Diesel vehicle emission control regulations;

Chemical characterisation of fine particle emissions from wood stove combustion of common woods growing in mid-European Alpine regions by Christoph Schmidl; Iain L. Marr; Alexandre Caseiro; Petra Kotianová; Axel Berner; Heidi Bauer; Anne Kasper-Giebl; Hans Puxbaum (126-141).
Woodsmoke samples derived from the combustion of beech, oak, spruce, larch and softwood briquettes in a closed stove have been collected and analysed so as to derive chemical profiles for ambient particulate matter (PM) source apportionment studies, for example, by CMB modelling. Trace metals, soluble ions, carbon species total carbon (TC), elemental carbon (EC) and organic carbon (OC), anhydrosugars, polar and non-polar trace organics, cellulose and humic-like substances (HULIS) have been measured. The inorganic and most organic components were not significantly different for the different woods, so that one profile could be derived for CMB modelling. The anhydrosugar levoglucosan was present in high concentrations, 4–15% w/w, and for the mix of woods important for Austria, one conversion factor can be used to derive the mass of woodsmoke from the levoglucosan concentration in ambient air. Mannosan is also a major component, 0.3–4% w/w, which, taken together with the levoglucosan content, permits estimates to be made of the proportion of hard- and softwood smoke to ambient PM.
Keywords: Woodsmoke; Levoglucosan; Mannosan; Particulate matter emission; Wood stove;

Environmental fate of gaseous elemental mercury at an urban monitoring site based on long-term measurements in Korea (1997–2005) by Zang-Ho Shon; Ki-Hyun Kim; Sang-Keun Song; Min-Young Kim; Jeong Soon Lee (142-155).
In this study, long-term monitoring of gaseous elemental mercury (Hg(0), GEM) was carried out at an urban site in Seoul, Korea from September 1997 to January 2005. There was no discernible long-term trend to predict the future direction of Hg(0) concentration shift across a 9-year study period. In contrast, seasonal trend analysis indicated that maximum Hg(0) concentrations occurred in the winter, while the minimum occurred in the fall. In addition, Hg(0) concentrations varied diurnally with the nighttime dominance, especially in the winter. It was suggested that the distribution of Hg(0) was controlled mainly by anthropogenic sources and in part by interplay of photochemical oxidation (through OH and O3), meteorological conditions (e.g., precipitation), and dry deposition during the study period. The contribution of the O3-dependent photochemical oxidation leading to Hg(0) loss was significantly larger than its OH counterpart. The photochemical lifetime of Hg(0), when induced based on the oxidation by O3 and OH, was estimated to vary from 1.1 to 2.4 years.
Keywords: Urban; Gaseous elemental mercury; Lifetime; Photochemical oxidation; Hg;

Indoor–outdoor relationships of particle number and mass in four European cities by Gerard Hoek; Gerard Kos; Roy Harrison; Jeroen de Hartog; Kees Meliefste; Harry ten Brink; Klea Katsouyanni; Anna Karakatsani; Maria Lianou; Anastasia Kotronarou; Ilias Kavouras; Juha Pekkanen; Marko Vallius; Markku Kulmala; Arto Puustinen; Steve Thomas; Claire Meddings; Jon Ayres; Joop van Wijnen; Kaarle Hameri (156-169).
The number of ultrafine particles in urban air may be more health relevant than the usually measured mass of particles smaller than 2.5 or 10 μm. Epidemiological studies typically assess exposure by measurements at a central site. Limited information is available about how well measurements at a central site reflect exposure to ultrafine particles.The goals of this paper are to assess the relationships between particle number (PN) and mass concentrations measured outdoors at a central site, right outside and inside the study homes. The study was conducted in four European cities: Amsterdam, Athens, Birmingham and Helsinki. Particle mass (PM10 and PM2.5), PN, soot and sulfate concentrations were measured at these sites. Measurements of indoors and outdoors near the home were made during 1 week in 152, mostly non-smoking, homes. In each city continuous measurements were also performed at a central site during the entire study period.The correlation between 24-h average central site outdoor and indoor concentrations was lower for PN (correlation among cities ranged from 0.18 to 0.45) than for PM2.5 (0.40–0.80), soot (0.64–0.92) and sulfate (0.91–0.99). In Athens, the indoor–central site correlation was similar for PN and PM2.5. Infiltration factors for PN and PM2.5 were lower than for sulfate and soot. Night-time hourly average PN concentrations showed higher correlations between indoor and central site, implying that indoor sources explained part of the low correlation found for 24-h average concentrations.Measurements at a central site may characterize indoor exposure to ambient particles less well for ultrafine particles than for fine particle mass, soot and sulfate.
Keywords: Particle number concentration; PM2.5; PM10; Indoor–outdoor relationships;

Measurements of nonmethane hydrocarbons in 28 United States cities by Angela K. Baker; Andreas J. Beyersdorf; Lambert A. Doezema; Aaron Katzenstein; Simone Meinardi; Isobel J. Simpson; Donald R. Blake; F. Sherwood Rowland (170-182).
Between 1999 and 2005 a sampling campaign was conducted to identify and quantify the major species of atmospheric nonmethane hydrocarbons (NMHCs) in United States cities. Whole air canister samples were collected in 28 cities and analyzed for methane, carbon monoxide (CO) and NMHCs. Ambient mixing ratios exhibited high inter- and intra-city variability, often having standard deviations in excess of 50% of the mean value. For this reason, ratios of individual NMHC to CO, a combustion tracer, were examined to facilitate comparison between cities. Ratios were taken from correlation plots between the species of interest and CO, and most NMHCs were found to have correlation coefficients (r 2) greater than 0.6, particularly ethene, ethyne and benzene, highlighting the influence of vehicular emissions on NMHC mixing ratios. Notable exceptions were the short-chain alkanes, which generally had poor correlations with CO. Ratios of NMHC vs. CO were also used to identify those cities with unique NMHC sources.
Keywords: NMHCs; Carbon monoxide; Vehicular emissions; Urban air pollution; Ozone precursors;

Investigation of particles emitted from modern 2-stroke scooters by D. Etissa; M. Mohr; D. Schreiber; P.A. Buffat (183-195).
Transmission electron microscopy (TEM), combined with X-ray energy dispersive spectroscopy (EDS)—both single and tandem differential mobility analyzer (TDMA)—have been used to investigate particles emitted by two modern 2-stroke scooters with different mixture preparation systems (direct injection and carburetor). In this study, we focused on investigating the influence of engine type and catalytic converter on morphology, volatility, and structure of the particles. The experiments showed an almost complete removal of the enormous number of exhaust particles when the temperature of an evaporation tube along the sampling line is increased from ambient to 400 °C. These results suggest that the exhaust particles emitted by 2-stroke scooters are volatile and no indication on the occurrence of layer structure was found, regardless of the mixture preparation system of the engine. Exhaust particles scanned before the catalytic converter were higher in number and lost a larger fraction of their volume in the evaporation tube compared to those scanned downstream of it. The presence of three major particle groups was identified by TEM analyzes, namely particles that are dominant in number but unstable under vacuum at room temperature, soot-like agglomerates and calcium-rich particles. The size of the unstable particles obtained by TEM agrees fairly with the result measured by differential mobility analyzer (DMA). We conclude that number concentration and size distribution of the particles emitted by 2-stroke scooters, are roughly in the range of 4-stroke diesel engines; however, the nature of the particles is quite different.
Keywords: 2-Stroke scooters; Tandem DMA; TEM analysis; Volatile particles;

The objective of this study is to estimate the atmospheric emissions by international merchant shipping of carbon dioxide (CO2), sulphur dioxide (SO2) and nitrogen oxides (NO X ) during 1 year in the Belgian part of the North Sea, including the four Belgian seaports: Antwerp, Ghent, Ostend and Zeebrugge. The estimated emissions are based on a bottom-up, activity-based methodology (Group 1), covering more than 90% of shipping activity, complemented with a top-down fuel consumption methodology for the remaining activities. In total, an estimate of 1880 kton CO2, 31 kton SO2 and 39 kton NO X is emitted over the period April 2003 until March 2004. Compared to national inventories (2003 data) this accounts to 1.5% for CO2, 30% for SO2 and 22% for NO X of total emissions of these gases in Belgium. When the CO2 figure is compared with the current estimate of CO2 emissions from international shipping, based on sold bunker fuels (22 754 kton CO2), the relevance of a detailed and precise emission inventory becomes clear. In the end, the Belgian estimates are validated by comparing them with Dutch, EU and international emission estimates.
Keywords: International shipping; Atmospheric emissions; Belgium; Carbon dioxide; Sulphur dioxide; Nitrogen oxides;