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Atmospheric Environment (v.45, #16)
A review of commuter exposure to ultrafine particles and its health effects by Luke D. Knibbs; Tom Cole-Hunter; Lidia Morawska (pp. 2611-2622).
Ultrafine particles (UFPs, <100nm) are produced in large quantities by vehicular combustion and are implicated in causing several adverse human health effects. Recent work has suggested that a large proportion of daily UFP exposure may occur during commuting. However, the determinants, variability and transport mode-dependence of such exposure are not well-understood. The aim of this review was to address these knowledge gaps by distilling the results of ‘in-transit’ UFP exposure studies performed to-date, including studies of health effects.We identified 47 exposure studies performed across 6 transport modes: automobile, bicycle, bus, ferry, rail and walking. These encompassed approximately 3000 individual trips where UFP concentrations were measured. After weighting mean UFP concentrations by the number of trips in which they were collected, we found overall mean UFP concentrations of 3.4, 4.2, 4.5, 4.7, 4.9 and 5.7×104particlescm−3 for the bicycle, bus, automobile, rail, walking and ferry modes, respectively. The mean concentration inside automobiles travelling through tunnels was 3.0×105particlescm−3.While the mean concentrations were indicative of general trends, we found that the determinants of exposure (meteorology, traffic parameters, route, fuel type, exhaust treatment technologies, cabin ventilation, filtration, deposition, UFP penetration) exhibited marked variability and mode-dependence, such that it is not necessarily appropriate to rank modes in order of exposure without detailed consideration of these factors. Ten in-transit health effects studies have been conducted and their results indicate that UFP exposure during commuting can elicit acute effects in both healthy and health-compromised individuals. We suggest that future work should focus on further defining the contribution of in-transit UFP exposure to total UFP exposure, exploring its specific health effects and investigating exposures in the developing world.► Ultrafine particles (UFPs) can cause negative acute health effects in humans. ► Commuting can account for a significant proportion of daily exposure. ► Exposure depends on transport mode used and a range of determinant factors. ► This paper explores these factors and makes recommendations for future research.
Keywords: Air pollution; Transport modes; Acute health effects; Travel; Public transport
Evaluating the efficiency of Diesel Particulate Filters in high-duty vehicles: Field operational testing in Portugal by H. Tente; P. Gomes; F. Ferreira; J.H. Amorim; P. Cascão; A.I. Miranda; L. Nogueira; S. Sousa (pp. 2623-2629).
The higher fuel economy allowed by diesel engines in comparison with Otto cycle based engines drove them to a progressive lead in vehicle fleet shares, especially within high-duty fleets, during last years. However, diesel engines have also other less welcome properties such as considerable tailpipe Particulate Matter (PM) emissions that contribute to adverse health effects and also to ecosystems and built heritage degradation. This burden requires straightforward mitigation measures and one of the most frequent in Europe has been the operational use of particle traps in a great diversity of fleets, in particular captive ones. These captive fleets account for an important percentage of annual mileage in urban areas. Nevertheless there’s a lack of information on filters efficiency under real operational conditions as also of an affordable and easily accessible method for doing this evaluation, since the typical methodology for testing particle traps is used only for homologation purposes.Aiming to operationally test Diesel Particulate Filters (DPF) performances using different engine types and emission technologies (EURO standards) tests were implemented in a total of 12 vehicles equipped with 4 different commercially available wall-flow DPF. These tests were done in the two largest Portuguese metropolitan areas, Lisbon and Oporto. Several opacity measurements using the free acceleration test were performed with and without the filter installed for at least 200 running hours per vehicle. Other relevant data (such as fuel consumption) were recorded for evaluating also other possible secondary effects on the vehicle performance.Results indicate an average reduction of 92% in opacity, while no significant changes in fuel consumption and engine power were registered. Conclusions highlight not only the adequacy of the filters tested for PM reduction as well as an inexpensive methodology with potential for ensuring its efficiency in high-duty vehicle fleets real-world operation.► Diesel Particulate Filters (DPF) were tested in real operational conditions. ► DPF implementation in High-Duty Vehicles significantly reduced PM emissions. ► Opacity is a good and inexpensive indicator for evaluating DPF efficiency. ► Opacity is also a straightforward way for enforcing DPF installation.
Keywords: Diesel Particulate Filters; PM emissions; PM reduction measures; Tailpipe emissions; Opacity; Free acceleration test; Ambient air quality management
Monitoring the long-range transport effects on urban PM10 levels using 3D clusters of backward trajectories by László Makra; István Matyasovszky; Zoltán Guba; Kostas Karatzas; Pia Anttila (pp. 2630-2641).
The purpose of the study is to identify long-range transport patterns that may have an important influence on PM10 levels in three European cities at different latitudes, namely Thessaloniki, Szeged and Helsinki. A further aim is to separate medium- and long-range PM10 transport for these cities. 4-day, 6-hourly three-dimensional (3D) backward trajectories arriving at these locations at 1200 GMT were computed using the HYSPLIT model over a 5-year period from 2001 to 2005. A k-means clustering algorithm using the Mahalanobis metric was applied in order to develop trajectory types. The 3D delimination of the clusters by the function “convhull” is a novel approach. Two statistical indices were used to evaluate and compare critical daily PM10 exceedances corresponding to the trajectory clusters. For Thessaloniki, the major PM10 transport can be clearly associated with air masses arriving from Central and Southern Europe. Occasional North African dust intrusions over Greece are also found. The transport of particulate matter from North-western Europe to Thessaloniki is of limited importance. For Szeged, Central Europe, Southern Europe and Mid-eastern Europe are the most important sources of PM10. The occasional appearance of North African-origin dust over Hungary is also detected. Local PM10 levels tend to be diluted when air masses arrive at the Carpathian Basin from North-western Europe, the Mid-Atlantic – Western Europe and Northern Europe. For Helsinki, high PM10 concentrations are due to air masses coming from Northern and Eastern Europe including North-western Russia. An occasional Caspian Sea desert influence on particulate levels can also be identified. However, air currents coming from the Northern Atlantics, Northern and North-western Europe tend to dilute PM10 levels. A simple approach is developed in order to separate medium- and long-range PM10 transport for each city.► The major PM10 transport to Thessaloniki comes from Central and Southern Europe. ► Principal sources of PM10 for Szeged are Central, Southern and Mid-eastern Europe. ► Occasional North African dust intrusions are found over Thessaloniki and Szeged. ► Major PM10 transport arrives in Helsinki from Northern and Eastern Europe. ► For Helsinki an occasional Caspian Sea desert influence on PM10 levels is identified.
Keywords: Long-range PM10 transport; Backward trajectories; Cluster analysis; Mahalanobis metric
PM10-bound polycyclic aromatic hydrocarbons: Concentrations, source characterization and estimating their risk in urban, suburban and rural areas in Kandy, Sri Lanka by A.P. Wickramasinghe; D.G.G.P. Karunaratne; R. Sivakanesan (pp. 2642-2650).
Kandy, a world heritage city, is a rapidly urbanized area in Sri Lanka, with a high population density of ∼6000habkm−2. As it is centrally located in a small valley of 26km2 surrounded by high mountains, emissions from the daily flow of >100,000 vehicles, most are old and poorly maintained, get stagnant over the study area with an increased emphasis on the associated health impacts. Particulate matter (PM) and polycyclic aromatic hydrocarbons (PAHs) are considered to be major pollutants in vehicular emissions; while PAHs account for the majority of mutagenic potency of PM. The purpose of the current study is to determine the 8h average concentrations of ambient PM10 PAHs at twenty sites distributed in the urban, suburban and rural Kandy. Samples on glass micro fibre filters were collected with a high volume air sampler from July/2008 to March/2009, prepared through standard procedures and analyzed for PAHs by high performance liquid chromatography with ultraviolet visible detection. Further, the type and strength of possible anthropogenic emission sources that cause major perturbations to the atmosphere were assessed by traffic volume (24h) counts and firewood mass burnt/d at each sampling site, with the subsequent societal impact through quantitative cancer risk assessment.The results can serve as a base set to assess the PAH sources, pollution levels and human exposure. Mean total concentrations of 16 prioritized PAHs (∑PAHs) ranged from 57.43 to 1246.12ngm−3 with 695.94ngm−3 in urban heavy traffic locations (U/HT), 105.55ngm−3 in urban light traffic locations, 337.45ngm−3 in suburban heavy traffic stations, 154.36ngm−3 in suburban light traffic stations, 192.48ngm−3 in rural high firewood burning area and 100.31ngm−3 in rural low firewood burning area. The mean PM10 concentration was 129μgm−3 (55–221μgm−3); which is beyond the WHO air quality standards. Polycyclic aromatic hydrocarbon signature and the spatial variation of ∑PAHs concentration with the type and strength of sources were applied to identify the sources of emission. A very similar and consistent source apportionment was obtained, which revealed that in the urban and suburban areas automobile emissions are the predominant daytime source of PAHs, but in suburbs with a low regression co-efficient between ∑PAHs and traffic volume indicating the impact of factors other than traffic volume. While domestic firewood burning is the major in rural areas, its commercial use has played a significant role in U/HT sites, with strong correlation to ∑PAHs. Current human exposure to PAHs can give rise to an increased cancer risk in Kandy in the coming decades, as denoted by the excess lifetime lung cancer risk of 3.31×10−3.► We study PM10 PAH concentrations and relations to their sources in Kandy, Sri Lanka. ► Particulate PAHs in Kandy is higher than those in many other reported cities. ► The particulate PAH concentration and total PM10 correlates well ( r=0.9). ► PAH compositions depend on their sources. ► Vehicular emissions and firewood burning are the main sources of PAHs in Kandy.
Keywords: Polycyclic aromatic hydrocarbons (PAHs); Particulate matter (PM); Source apportionment; Vehicular emissions; Urban air quality; Cancer risk
Spatial and temporal variation of chemical composition and mass closure of ambient coarse particulate matter (PM10–2.5) in the Los Angeles area by Kalam Cheung; Nancy Daher; Winnie Kam; Martin M. Shafer; Zhi Ning; James J. Schauer; Constantinos Sioutas (pp. 2651-2662).
To study the seasonal and spatial characteristics, as well as chemical composition of coarse (2.5–10 μm) particulate matter (PM), 10 sampling sites were set up in different areas (urban, semi-rural, desert, near-freeway, community-based, etc) of the Los Angeles Basin. Ambient coarse PM was collected over a year long in 24-hour periods once per week during weekdays, and was analyzed for elemental carbon and organic carbon (EC–OC), water soluble inorganic ions, and total metals and elements. Five categories were used to reconstruct PM mass: 1) crustal materials and other trace elements 2) organic matter 3) elemental carbon 4) sea salt and 5) secondary ions. Overall, crustal materials and other trace elements were the most abundant category, accounting for an average of 47.5 ± 12% of the total reconstructed mass. Secondary ions (sulfate, nitrate and ammonium) and organic matter also contributed significantly at mass fractions of around 22.6% and 19.7%, respectively. Elemental carbon was a less significant component, accounting for less than 2% of total mass across sites. Sea salt particles were more prevalent in spring and summer (12.7%) due to the strong prevailing onshore southwesterly wind in that period. Mass fractions of organic matter, as well as crustal materials and other trace elements were higher in fall and winter, indicating that their contributions were not affected by the lower wind speed and change in wind direction during that period. PM concentrations of sea salt particles decreased from coast to inland along the trajectory of LA Basin, while crustal materials and other trace elements became dominant in inland sites. On the other hand, organic carbon was found to be well-correlated with tracers of soil dust ( R = 0.74 and 0.72 for Ti and Fe respectively), suggesting that humic substances might be the major constituent of organic matter in coarse mode in the Los Angeles Basin.► Crustal materials and other trace elements comprise a major fraction of coarse PM mass. ► Particulate nitrate was the most abundant species in coarse mode aerosols. ► Humic substances might be a major component of organic material in coarse PM.
Keywords: Coarse particle; Particulate matter; Los Angeles Basin; Mass closure; Chemical composition
Evaluating the calculated dry deposition velocities of reactive nitrogen oxides and ozone from two community models over a temperate deciduous forest by Zhiyong Wu; Xuemei Wang; Fei Chen; Andrew A. Turnipseed; Alex B. Guenther; Dev Niyogi; Umarporn Charusombat; Beicheng Xia; J. William Munger; Kiran Alapaty (pp. 2663-2674).
Hourly measurements of O3, NO, NO2, PAN, HNO3 and NO y concentrations, and eddy-covariance fluxes of O3 and NO y over a temperate deciduous forest from June to November, 2000 were used to evaluate the dry deposition velocities ( Vd) estimated by the WRF-Chem dry deposition module (WDDM), which adopted scheme for surface resistance ( Rc), and the Noah land surface model coupled with a photosynthesis-based Gas-exchange Evapotranspiration Model (Noah-GEM). Noah-GEM produced better Vd(O3) variations due to its more realistically simulated stomatal resistance ( Rs) than WDDM. Vd(O3) is very sensitive to the minimum canopy stomatal resistance ( Ri) which is specified for each seasonal category assigned in WDDM. Treating Sep-Oct as autumn in WDDM for this deciduous forest site caused a large underprediction of Vd(O3) due to the leafless assumption in ‘autumn’ seasonal category for which an infinite Ri was assigned. Reducing Ri to a value of 70sm−1, the same as the default value for the summer season category, the modeled and measured Vd(O3) agreed reasonably well. HNO3 was found to dominate the NO y flux during the measurement period; thus the modeled Vd(NO y) was mainly controlled by the aerodynamic and quasi-laminar sublayer resistances ( Ra and Rb), both being sensitive to the surface roughness length ( z0). Using an appropriate value for z0 (10% of canopy height), WDDM and Noah-GEM agreed well with the observed daytime Vd(NO y). The differences in Vd(HNO3) between WDDM and Noah-GEM were small due to the small differences in the calculated Ra and Rb between the two models; however, the differences in Rc of NO2 and PAN between the two models reached a factor of 1.1–1.5, which in turn caused a factor of 1.1–1.3 differences for Vd. Combining the measured concentrations and modeled Vd, NO x, PAN and HNO3 accounted for 19%, 4%, and 70% of the measured NO y fluxes, respectively.► The first study on evaluating Vd(NO y) in the dry deposition models. ► Compared the performance of two models with different canopy treatments. ► Assessed the sensitivity of key parameters to simulate Vd(O3) and Vd(NO y). ► Improved the models by comparing with the field observations. ► Further developed the GEM model.
Keywords: Reactive nitrogen oxides; Ozone; Dry deposition velocity; WRF-Chem dry deposition module; Noah-GEM; 1-D model
Formaldehyde removal by common indoor plant species and various growing media by Ahu Aydogan; Lupita D. Montoya (pp. 2675-2682).
Three porous materials (growstone, expanded clay and activated carbon) were evaluated as hydroponic growing media and for their individual ability to remove the indoor volatile organic compound formaldehyde under three conditions: growing medium alone, dry medium in a pot, and wet medium in a pot. The total percent-reduction of formaldehyde by each growing media was evaluated over a 10-h period. In all cases, activated carbon achieved the highest removal under the three conditions studied with average percent reductions measured at about 98%. Four common interior plants: Hedera helix (English ivy), Chrysanthemum morifolium (pot mum), Dieffenbachia compacta (dump cane) and Epipremnum aureum (golden pathos) growing in growstone were then tested for their ability to remove formaldehyde. The removal capacity of the aerial plant parts (AP), the root zone (RZ) and the entire plant (EP) growing in growstone were determined by exposing the relevant parts to gaseous formaldehyde (∼2000 μg m−3) in a closed chamber over a 24-h period. The removal efficiency between species and plant parts were compared by determining the time interval required to decrease about 2/3 of the total formaldehyde concentration reduction, T2/3. The T2/3 measured were 23, 30, 34 and 56 min for EP of C. morifolium, E. aureum, D. compacta and H. helix, respectively. The formaldehyde removal by the root zone was found to be more rapid than the removal by the aerial plant parts.► The four plant species demonstrated similar abilities to remove formaldehyde. ► The T2/3 determined for each species was significantly different. ► Activated carbon showed highest formaldehyde removal under all conditions studied. ► All plant species showed faster uptake of formaldehyde under dark cycle conditions.
Keywords: Volatile organic compounds; Formaldehyde; Indoor air quality; Interior plants; Growing media
Air pollution and climate change co-benefit opportunities in the road transportation sector in Durban, South Africa by Tirusha Thambiran; Roseanne D. Diab (pp. 2683-2689).
The contribution of the road transportation sector to emissions of air pollutants and greenhouse gases is a growing concern in developing countries. Emission control measures implemented within this sector can have varying counteracting influences. In the city of Durban, South Africa, the growing dependence on privately-owned motor vehicles and increasing usage of roads for freight transport have all resulted in significant air pollution and greenhouse gas emissions. In this study, an emissions inventory was developed for the road transport sector and was used as a basis to explore intervention opportunities that are likely to reduce simultaneously, air pollution and greenhouse gas emissions in this sector. It was found that reducing the vehicle kilometres travelled by privately-owned motor vehicles and improving the efficiency of road freight transport offered the greatest potential for achieving co-benefits.► Road transport is responsible for significant atmospheric emissions in Durban. ► Private motor vehicle fleet is old & road freight dominates over the use of rail. ► Presently no interventions are taken to tackle pollution from this sector. ► Policies should focus on reducing vehicle kilometres travelled and fleet renewal.
Keywords: Road transport; Air quality; Greenhouse gas emissions; South Africa
Determination of aldehydes and ketones with high atmospheric reactivity on diesel exhaust using a biofuel from animal fats by R. Ballesteros; E. Monedero; J. Guillén-Flores (pp. 2690-2698).
Biodiesel from animal fats appears as an alternative for conventional diesel in automotive consumption. Animal fats are classified into three categories, although only one of them can be used for biodiesel production, according to regulation. Due to its novelty, researchers testing animal-fat biodiesel on diesel engines focus only on regulated emissions. In this paper, the experiments carried out analyze carbonyl compounds emissions, due to its highly atmospheric reactivity, to complete the characterization of the total emissions in this kind of biofuel. Two fuels, a reference petro-diesel and a pure animal-fat biodiesel, were tested in a 4-cylinder, direct injection, diesel engine Nissan Euro 5 M1D-Bk. Samples were collected in 4 different operating modes and 3 points along the exhaust line. The analyses of samples were made in a high performance liquid chromatography, following the method recommended by the CARB to analyze air quality. Results show, on the one hand, a significant rise in carbonyl emissions, almost three times at the mode with highest hydrocarbon emissions, when biodiesel is used. On the other hand, on average, a reduction of 90% of carbonyl emissions when exhaust gases go through the different post-treatment systems installed. Despite this reduction, specific reactivity does not decrease substantially.► Speciation of 13 carbonyl compounds of the exhaust of a Euro 5 diesel engine. ► Engine tested with conventional diesel fuel and biodiesel fuel from animal fats. ► The post-treatment systems change the exhaust specific reactivity. ► This biofuel can be considered as an alternative fuel despite its oxygen content.
Keywords: Biodiesel; Animal fats; Carbonyl compounds; Diesel emissions; MIR; Specific reactivity
Aged status of soot particles during the passage of a weak cyclone in Beijing by Hongya Niu; Longyi Shao; Daizhou Zhang (pp. 2699-2703).
Atmospheric particles at an urban site in Beijing from Apr. 18 to 21, 2009, when a weak synoptic cyclone passed and the air quality was relatively fine, were investigated by using electron microscopes. Particles collected from different stages of the cyclone were characterized by their shape, size and elemental composition. Soot particles were predominant and concentrated in the size range of 0.2–1.0 μm, and out of this range were rarely detected. Most of the soot particles exhibited aged shape, i.e. shrunk clusters with liquid coating (the so-called core-shell structure), compared to the open spherule’s chain or agglomerate shape of fresh soot particles. Morphologies of the particles in the prefrontal and postfrontal air were compared. The mean equivalent diameter of the particles in the prefrontal air was 0.36–0.38 μm and in the postfrontal air was 0.35–0.41 μm. More than 50% of the particles had aspect ratios between 1.0 and 1.4, and the remains frequently smaller than 2.0. In terms of circularity factor, 57–64% particles in the prefrontal air and 41–51% in the postfrontal air appeared in the range of 0.6–1.0. These results indicate that the aged status of soot particles in the prefrontal and postfrontal air were not very different, although the quality of the postfrontal air was much better than that of the prefrontal air, suggesting that fresh soot particles in chain or aggregate shape could be modified into core-shell structure rapidly even in less polluted air. In addition, a primary estimate showed that aging had caused the decrease of the cross-section areas of soot parts in the particles.► Soot particles during a cyclone passage in Beijing were studied. ► Aged status of soot in prefrontal and postfrontal air was not very different. ► Fresh soot particles could be modified rapidly in less polluted postfrontal air. ► Aging caused the decrease of cross-section areas of soot parts in the particles.
Keywords: Equivalent diameter; Aspect ratio; Circularity factor; Aging; Electron microscope
Are terrestrial mosses good biomonitors of atmospheric deposition of Mn? by M.T. Boquete; J.A. Fernández; J.R. Aboal; A. Carballeira (pp. 2704-2710).
A series of field and laboratory experiments was carried out to determine whether the terrestrial moss Pseudoscleropodium purum is a good biomonitor of the atmospheric deposition of Mn. Samples of the species were collected from sampling sites located in industrial areas and in unpolluted areas in Galicia (NW Spain). The results showed that: i) uptake of Mn by the moss may be reduced under certain conditions (related with the environment, moss ecophysiology and source and type of emission), even though atmospheric inputs and inputs from vegetation remain the same. The concentration of Mn in moss samples from the surroundings of an aluminium smelter was 6 times lower than in samples from an unpolluted site, in which levels were similar to the regional background level. The low concentrations were maintained over time; ii) the decrease in the uptake of Mn was due to differences in the environmental conditions to which the organisms are exposed. Genetic causes for the differences were ruled out as the study of moss samples transplanted within and between unpolluted and contaminated areas showed that the final concentrations in the transplanted moss in each of the scenarios were very similar; iii) the direct relationship between exposure and concentration was altered in the surroundings of the contaminated sampling site, although the causes of the inhibition of uptake could not be established by incubation of moss samples under laboratory conditions, and v) unlike other metals, there are few sources of emission of Mn to the atmosphere. However, when the emissions were in a particulate form, the concentrations of Mn in the moss varied in accordance with the atmospheric deposition. For all of these reasons, we consider that P. purum is not a good biomonitor of the atmospheric deposition of Mn, except under certain circumstances, and we recommend exclusion of the element from regional surveys.► Moss P. purum is examined as biomonitor of the atmospheric deposition of Mn. ► Relationship between Mn exposure and moss Mn levels is altered by some factors. ► With few exceptions, P. purum is not a suitable biomonitor of Mn deposition. ► We recommend the exclusion of this element from regional surveys.
Keywords: Terrestrial bryophytes; Biomonitoring; Atmospheric pollution; Metals
Emission characteristics of nonmethane hydrocarbons from private cars and taxis at different driving speeds in Hong Kong by H. Guo; S.C. Zou; W.Y. Tsai; L.Y. Chan; D.R. Blake (pp. 2711-2721).
Vehicular emissions are the major sources of a number of air pollutants including nonmethane hydrocarbons (NMHCs) in urban area. The emission composition and emission factors of NMHCs from vehicles are currently lacking in Hong Kong. In this study, speciation and emission factors of NMHCs emitted from gasoline-fuelled private cars and liquefied petroleum gas (LPG)-fuelled taxis at different driving speeds were constructed using a chassis dynamometer. Large variations in the contributions of individual NMHC species to total emission were observed for different private cars at different driving speeds. The variations of individual NMHC emissions were relatively smaller for taxis due to their relatively homogeneous year of manufacture and mileages. Incomplete combustion products like ethane, ethene and propene were the major component of both types of vehicles, while unburned fuel component was also abundant in the exhausts of private cars and taxis (i.e. i-pentane and toluene for private car, and propane and butanes for taxi). Emission factors of major NMHCs emitted from private cars and taxis were estimated. High emission factors of ethane, n-butane, i/ n-pentanes, methylpentanes, trimethylpentanes, ethene, propene, i-butene, benzene, toluene and xylenes were found for private cars, whereas propane and i/ n-butanes had the highest values for taxis. By evaluating the effect of vehicular emissions on the ozone formation potential (OFP), it was found that the contributions of olefinic and aromatic hydrocarbons to OFP were higher than that from paraffinic hydrocarbons for private car, whereas the contributions of propane and i/ n-butanes were the highest for taxis. The total OFP value was higher at lower speeds (≤50 km h−1) for private cars while a minimum value at driving speed of 100 km h−1 was found for taxis. At the steady driving speeds, the total contribution of NMHCs emitted from LPG-fuelled taxis to the OFP was much lower than that from gasoline-fuelled private cars. However, at idling state, the contribution of NMHCs from LPG-fuelled vehicles to OFP was comparable to that from gasoline-fuelled vehicles. The findings obtained in this study can be used to mitigate the air pollution caused by vehicles in highly dense urban areas.► The emission composition and emission factors of NMHCs from vehicles currently lack in Hong Kong. ► High emission factors of alkanes, benzene and toluene were found for private cars. ► Propane and i/ n-butanes had the highest values for taxis. ► Aromatics and C3–C4 alkanes were the largest contributor to OFP for cars, and taxis, respectively. ► The findings are helpful to mitigate air pollution caused by vehicles in highly dense urban areas.
Keywords: Nonmethane hydrocarbon; Driving speed; Emission factor; Ozone formation potential
Hygroscopic property of water-soluble organic-enriched aerosols in Ulaanbaatar, Mongolia during the cold winter of 2007 by Jinsang Jung; Young J. Kim; Shankar Gopala Aggarwal; Kimitaka Kawamura (pp. 2722-2729).
The hygroscopic properties of the water-soluble matter extracts of atmospheric aerosols collected at an urban site (47.92° N, 106.90° E, ∼1300m above sea level) in Ulaanbaatar, Mongolia during the cold winter of 2007 were investigated using a hygroscopicity tandem differential mobility analyzer (H-TDMA). Dynamic shape correction factor ( χ), the ratio of the actual drag force on a non-spherical aerosol particle to that on a sphere of equivalent volume, of the laboratory generated water-soluble matter (WSM) was found to be 1.09–1.38 (avg. 1.23±0.10), implying that particles generated from the WSM are highly non-spherical. The reduction in the mobility diameter can cause ∼11% underestimation in a hygroscopic growth factor at 85% RH. The hygroscopic growth factors at 85% RH ( g(85%)), defined as the ratio of the particle diameter at 85% RH to that at RH<10% (initial dry diameter), of the WSM (initial dry particle diameter=100nm) were 1.32–1.50 (avg. 1.40±0.06). The g(RH) of the water-soluble organic matter (WSOM) was retrieved from the measured g(RH) of the WSM and using the ZSR (Zdanovskii–Stokes–Robinson) approach and the thermodynamic aerosol inorganic model (AIM). We found that the g(85%) of the WSOM were in the range of 1.11–1.35 (avg. 1.22±0.08), which are comparable to those of the biomass burning aerosols.Display Omitted► Mobility diameter shows substantial reduction at 20–40% RH. ► Laboratory generated particles are highly non-spherical shape. ► Hygroscopic growth factor of water-soluble organic aerosols is 1.22±0.08 at 85% RH. ► These growth factors are comparable to biomass burning aerosol and aged organics.
Keywords: Water-soluble organic aerosol; Hygroscopicity tandem differential mobility analyzer; Ulaanbaatar; Hygroscopic growth factor
Contribution of long range transport to local fine particulate matter concerns by K.M. Wagstrom; S.N. Pandis (pp. 2730-2735).
We have utilized the Particulate Matter Source Apportionment Technology (PSAT) in PMCAMx (a regional chemical transport model) to quantify the contributions from local emissions and short range (under 100 km), mid range (100–550 km) and long range (over 550 km) pollutant transport to both primary and secondary particulate matter concentrations using the Eastern United States as a test case. We have studied these contributions for two urban (Pittsburgh, Pennsylvania and Atlanta, Georgia) and one rural area (Great Smoky Mountains National Park) during all seasons.The local emissions impacts to elemental carbon (EC) in major urban areas were found to be substantial with approximately 50% of the EC coming from local sources and 80% emitted within 200 km of the receptor. The local sources are even more important during the night contributing around 60% of the EC and then dropping to around 40% during the early afternoon. The EC in the rural Great Smoky Mountains was mainly the result of sources 100–550 km away. The seasonal variation of the EC source area contributions is small. There was also little difference between high and low EC concentration days.The contributions to secondary aerosol species were found to be more regional with more than 50% of the sulfate and secondary organic aerosol (SOA) originating from SO2 and VOC sources that were more than 200 km away from the receptor. The importance of sources further away increased during the winter because of the lower photochemical activity. While mid range transport dominated in the summer the sulfate and SOA levels in all areas, long range transport became the most important sulfate and SOA source during the winter in the colder Northeastern US and of sulfate in the warmer South.► Quantification of the contributions of short, mid and long range pollutant transport. ► Different impacts for primary and secondary PM components. ► Significant seasonal and spatial variation.
Keywords: Pollutant transport; Air quality modeling; Source apportionment
New particle formation and condensational growth in a large indoor space by Jan Hovorka; Martin Braniš (pp. 2736-2749).
Several episodes of new particle formation followed by slow condensational growth were observed in a large construction hall during a routine measurement of air quality in May of 2007. Both nucleation and growth resembled those processes in the outside, open atmosphere. Appearance near midday, relative indoor humidity below 50% and outdoor ozone concentration above 100 μg m−3 were characteristic for nucleation events. Condensational growth rates were about 2.6 nm h−1, close to those recorded at a rooftop station in an urban atmosphere in Prague. In the hall, the growths were frequently interrupted by the activity of personnel during work shifts. Outside of the work shifts, one case of undisturbed growth lasting for 18 h was recorded. Although the penetration of particles from outdoors is a possible explanation for the aerosol nucleation and growth, the low value of the air exchange rate (0.36 h−1), high number concentrations and long residence time of aerosol particles in a large hall allow us to hypothesize the whole process started and evolved indoors. This hypothesis has two important implications. New particle formation and growth can also be considered as a micro-scale phenomenon, and processes of atmospheric aerosol nucleation and growth can be studied under semi-experimental conditions in large indoor spaces.► Atmospheric aerosol formation and growth were recorded in a large construction hall. ► Ozonolysis of indoor generated NMHC may trigger nucleation and sustain condensation. ► Low air exchange rate neglected importance of aerosol penetration from outdoor. ► Large indoor dimensions result in a long aerosol residence times. ► Aerosol formation can be considered as micro-scale phenomenon.
Keywords: Aerosol nucleation; Air exchange rate; Aerosol residence time; Micro-scale
Estimating the climate and air quality benefits of aviation fuel and emissions reductions by Christopher S. Dorbian; Philip J. Wolfe; Ian A. Waitz (pp. 2750-2759).
In this study we consider the implications of our current understanding of aviation climate impacts as it relates to the ratio of non-CO2 to CO2 effects from aviation. We take as inputs recent estimates from the literature of the magnitude of the component aviation impacts and associated uncertainties. We then employ a simplified probabilistic impulse response function model for the climate and a range of damage functions to estimate the ratio of non-CO2 to CO2 impacts of aviation for a range of different metrics, scientific assumptions, future background emissions scenarios, economic growth scenarios, and discount rates. We take cost-benefit analysis as our primary context and thus focus on integral metrics that can be related to damages: the global warming potential, the time-integrated change in surface temperature, and the net present value of damages. We also present results based on an endpoint metric, the global temperature change potential. These latter results would be more appropriate for use in a cost-effectiveness framework (e.g., with a well-defined policy target for the anthropogenic change in surface temperature at a specified time in the future).We find that the parameter that most influences the ratio of non-CO2 to CO2 impacts of aviation is the discount rate, or analogously the time window used for physical metrics; both are expressions of the relative importance of long-lived versus short-lived impacts. Second to this is the influence of the radiative forcing values that are assumed for aviation-induced cloudiness effects. Given the large uncertainties in short-lived effects from aviation, and the dominating influence of discounting or time-windowing, we find that the choice of metric is relatively less influential. We express the ratios of non-CO2 to CO2 impacts on a per unit fuel burn basis so that they can be multiplied by a social cost of carbon to estimate the additional benefits of fuel burn reductions from aviation beyond those associated with CO2 alone (all else being equal). For a non-CO2 to CO2 ratio based on economic damage costs, we find a central value of 1.8 at a 3% discount rate, with a range from 0.6 to 2.5 for the upper and lower bounds of scientific and scenario-based uncertainty. Since estimating the co-benefits in this way is an important requirement for cost-benefit analyses, we also provide estimates of the air quality benefits of aviation fuel burn reduction in a similar format. We find the marginal damage costs of aircraft emissions below 3000 feet to be of similar magnitude to the climate costs on a per unit fuel burn basis, or an order of magnitude smaller on a per flight basis since we take no account of the air quality impacts of emissions above 3000 feet where the majority of fuel is consumed for the fleet.► We consider the climate and air quality co-benefits of aviation fuel burn reductions. ► We do so for a range of metrics and scientific and scenario assumptions. ► At 3% discount rate we find a ratio of non-CO2/CO2 damage costs of 1.8 [0.6–2.5]. ► The ratio is sensitive to discounting and aviation-induced cloudiness assumptions. ► Air quality costs are found to be ∼1/5th of climate costs for our central estimates.
Keywords: Aviation air quality and climate impacts; Non-CO; 2; impacts; Climate metrics
Dry and wet atmospheric deposition of nitrogen and phosphorus in Singapore by Jun He; Rajasekhar Balasubramanian; David F. Burger; Kevin Hicks; Johan C.I. Kuylenstierna; Sundarambal Palani (pp. 2760-2768).
Atmospheric nutrients have recently gained increased attention as significant additional sources of new nitrogen (N) and phosphorus (P) loading to aquatic ecosystems. The levels of nutrients (NO3−–N, NH4+–N, ON, DIP and OP) in aerosols and rainwater were measured and their respective deposition fluxes were estimated in the Marina catchment area, Singapore, from April 2007 to March 2008. During the study period, the mean atmospheric dry particulate fluxes (mgm−2month−1) were 21.64±13.56, 2.95±1.73, 24.21±9.59, 4.48±1.74 and 7.19±2.83 for NO3−–N, NH4+–N, ON, DIP and OP, respectively. In addition, the mean wet deposition fluxes (mgm−2month−1) were 59.60±45.29, 30.39±12.99, 39.03±20.70, 1.79±1.03 and 2.46±1.29 for NO3−–N, NH4+–N, ON, DIP and OP, respectively. Wet deposition made a larger contribution to total fluxes than dry deposition for N species especially NO3− and NH4+, but P species showed the opposite trend. Both TN and TP showed different seasonal variations with peak wet deposition fluxes in Dec 2007 and Jan 2008 as compared to dry deposition fluxes which peaked during the inter-monsoon (IM) period. Other than the local emissions, air mass backward trajectory analysis indicated that the atmospheric nutrient concentration may be affected by transboundary transport of nutrients from regional sources during different monsoon seasons. Statistical correlation analysis showed that the deposition fluxes were associated with meteorological factors. In addition, the N:P ratio in annual total (dry particulate+wet) atmospheric deposition flux in this study was 10.5, implying that the aquatic ecosystems in Singapore, fed principally by atmospheric nutrients, may tend toward N-limitation.► Atmospheric deposition of N and P-bearing species is reported. ► Both rainwater and aerosols showed a similar pattern in the occurrence of nutrients. ► Seasonal variations in wet and dry deposition fluxes were observed. ► Transboundary transport of atmospheric nutrients played an important role.
Keywords: Atmospheric deposition; Nitrogen; Phosphorus; Precipitation
Forecasting urban PM10 and PM2.5 pollution episodes in very stable nocturnal conditions and complex terrain using WRF–Chem CO tracer model by Pablo E. Saide; Gregory R. Carmichael; Scott N. Spak; Laura Gallardo; Axel E. Osses; Marcelo A. Mena-Carrasco; Mariusz Pagowski (pp. 2769-2780).
This study presents a system to predict high pollution events that develop in connection with enhanced subsidence due to coastal lows, particularly in winter over Santiago de Chile. An accurate forecast of these episodes is of interest since the local government is entitled by law to take actions in advance to prevent public exposure to PM10 concentrations in excess of 150 μg m−3 (24 h running averages). The forecasting system is based on accurately simulating carbon monoxide (CO) as a PM10/PM2.5 surrogate, since during episodes and within the city there is a high correlation (over 0.95) among these pollutants. Thus, by accurately forecasting CO, which behaves closely to a tracer on this scale, a PM estimate can be made without involving aerosol-chemistry modeling. Nevertheless, the very stable nocturnal conditions over steep topography associated with maxima in concentrations are hard to represent in models. Here we propose a forecast system based on the WRF–Chem model with optimum settings, determined through extensive testing, that best describe both meteorological and air quality available measurements. Some of the important configurations choices involve the boundary layer (PBL) scheme, model grid resolution (both vertical and horizontal), meteorological initial and boundary conditions and spatial and temporal distribution of the emissions. A forecast for the 2008 winter is performed showing that this forecasting system is able to perform similarly to the authority decision for PM10 and better than persistence when forecasting PM10 and PM2.5 high pollution episodes. Problems regarding false alarm predictions could be related to different uncertainties in the model such as day to day emission variability, inability of the model to completely resolve the complex topography and inaccuracy in meteorological initial and boundary conditions. Finally, according to our simulations, emissions from previous days dominate episode concentrations, which highlights the need for 48 h forecasts that can be achieved by the system presented here. This is in fact the largest advantage of the proposed system.► An urban scale PM10 and PM2.5 forecasting system is presented and evaluated. ► The system tackles the stable nocturnal conditions and steep topography. ► PM10 and PM2.5 events are effectively simulated using CO as a PM surrogate. ► Great sensitivity to PBL scheme, grid resolution, boundary conditions and emissions. ► Pollution episodes seem to be dominated by previous days emissions.
Keywords: PM10 and PM2.5 forecast; WRF–Chem CO tracer; Santiago de Chile; Data assimilation; Deterministic model
Evaluation of ambient SO2 measurement methods at roadside sites by Xiaohong Yao; Colin J. Lee; Greg J. Evans; Amanda Chu; Krystal J. Godri; Maygan L. McGuire; Andy C. Ng; Clarissa Whitelaw (pp. 2781-2788).
Accurate measurements of SO2 at low ambient concentrations are needed in order to investigate the role of SO2 in particle nucleation events and the long-term impact of reductions in sulfur emissions in recent decades. In this study, artifacts in SO2 concentration measurements were investigated using two identical ion chromatography-based instruments (the Gas Particle Ion Chromatograph, GP-IC, Dionex Corporation) and two identical UV fluorescence-based SO2 analyzers (the TECO 43CTL, an industry standard). The SO2 concentration values measured with the GP-IC at roadside sites were compared with simultaneous side-by-side measurements made with the fluorescence analyzers. The SO2 concentration measured with the GP-IC had an ∼30% negative calibration artifact. When the GP-ICs were calibrated using an improved procedure developed in the course of this study, only a ±5% difference from the TECO analyzers remained, except under high NO concentration conditions. The fluorescence analyzers exhibited a positive artifact under elevated NO concentration conditions. Sulfur oxidation ratios were calculated based on the GP-IC-measured SO2 and SO42- concentrations and used to help identify potential emission sources. The SO2 concentrations measured with the GP-IC were also compared to data obtained from a National Air Pollution Surveillance (NAPS) speciation sampler equipped with a Na2CO3-coated denuder. Good correlation between SO2 data from the two methods was seen during five months of measurement, but the GP-IC SO2 data were ∼30% lower than the NAPS data. Deposition of SO2 within an urban street canyon is discussed as a possible explanation for this difference.► The SO2 concentration measured with the GP-IC had a ∼30% negative calibration artifact. ► The GP-ICs were calibrated using an improved procedure developed in the course of this study. ► Only a ±5% difference from TECO analyzers remained, except under high NO concentration conditions. ► Sulfur oxidation ratios were calculated and used to help identify potential emission sources.
Keywords: NOx; SO; 2; GP-IC; Roadside; Artifact
The impact of the pollution control measures for the 2008 Beijing Olympic Games on the chemical composition of aerosols by Tomoaki Okuda; Shinichiro Matsuura; Daisuke Yamaguchi; Tomoaki Umemura; Eriko Hanada; Hiroki Orihara; Shigeru Tanaka; Kebin He; Yongliang Ma; Yuan Cheng; Linlin Liang (pp. 2789-2794).
We investigated the difference in the concentrations of air pollutants between the period of the Beijing 2008 Olympic Games and the same periods in the prior three years (2005–2007, the reference period), in particular, the chemical composition of the particulate matter. PM10, Black carbon (BC), SO2 and NO2 were reduced by 33%, 31%, 32% and 51%, respectively, whereas PM2.5 was not reduced during the Olympic period when compared to the reference period. Many pollution control measures that had been applied to prevent air pollution from contaminating the air quality in Beijing during the Olympic Games significantly reduced the larger particles (PM10), SO2 and NO2 but it did not as effectively reduce the much smaller particles (PM2.5). The sum of the measured water-soluble ions in total suspended particles (TSP) during the Olympic period was reduced by 35% when compared to the reference period. Each ion was reduced significantly by 43%–79% except for nitrogen-containing species. We estimated that CaSO4 reduction by 52% played a significant role in reducing larger particles during the Olympic period. Although many ions in PM2.5 showed a similar decreasing trend as those in TSP, NO3− in PM2.5 increased significantly. During the Olympic period, the atmospheric nitrogen cycle seemed to have been very complicated. Meteorological conditions such as temperature, relative humidity, or regional-scale air mass trajectory did not seem to be a major reason for the nitrate behavior. Instead, it is possible that the increase of ozone and/or oxidants around the center of Beijing may have accelerated the oxidation of nitrogen oxides to form nitrate. We found a trend in the concentration of high-molecular weight PAHs (HMW-PAHs), which had 5–7 rings decreased during the Olympic period. We considered that the reduction of HMW-PAHs that could be associated with the reduction of BC was due to the reduction of traffic flow resulting from traffic control measures implemented during that time period.Display Omitted► PM10 and Black carbon (BC) were reduced by 33% and 31%, respectively. ► PM2.5 was not reduced during the Olympic period when compared to reference period. ► Each water-soluble ion was reduced significantly by 43%–79% except for N-species. ► CaSO4 reduction by 52% played a significant role in reducing larger particles. ► The reduction of HMW-PAHs was due to the traffic control measures during the Olympic.
Keywords: Aerosol; Beijing; Black carbon; Olympic games; PM; 10; PM; 2.5; Polycyclic aromatic hydrocarbons (PAHs); TSP; Water-soluble ions
A novel approach for the characterization of transport and optical properties of aerosol particles near sources – Part I: Measurement of particle backscatter coefficient maps with a scanning UV lidar by Andreas Behrendt; Sandip Pal; Volker Wulfmeyer; Álvaro M. Valdebenito B.; Gerhard Lammel (pp. 2795-2802).
The physical and chemical properties of aerosols emitted from a livestock farm were determined by a novel approach which combines high-resolution lidar measurements (0.33 s, 30 m) with simulations of a microphysics–chemistry–transport model. This first of two companion papers describes the scanning lidar measurements of optical particle properties. The lidar system employed laser radiation at a wavelength of 355 nm with a power of 9 W and a pulse repetition rate of 30 Hz. The laser beam was expanded before transmission to the atmosphere so that it became eye-safe at distances >270 m to the lidar. The elastic backscatter signal was detected with a resolution of 0.033 s and 3 m. A receiving telescope with a primary-mirror diameter of 40 cm was used. For this system, we developed a novel method for two-dimensional retrievals of the particle backscatter coefficient. With this set up and approach, the lidar was able to identify the aerosol plume up to a range of ∼2.5 km from the source, a farm in northern Germany, in daytime. The measurements confirm that the optical particle properties of the emission plume vary largely with distance from the source and that the maximum particle backscatter coefficient is found away from the source. Within a close-to-horizontal scan (elevation angle of 2.3°), we found a mean particle backscatter coefficient of 1.5·10−5 m−1 sr−1 inside the plume between 1.5 and 2.0 km distance from the source. Subtraction of the mean particle backscatter coefficient of the background aerosol present in this case (4.1·10−6 m−1 sr−1) yields a particle backscatter coefficient of the livestock aerosols of 1.1·10−5 m−1 sr−1. The limited extend of the plume is revealed with the scanning lidar: Scans with a slightly higher elevation angle of 4.8° did not pick up the plume.
Keywords: Livestock aerosols; Aerosol–optical properties; Scanning lidar
Impact of traffic flows and wind directions on air pollution concentrations in Seoul, Korea by Youngkook Kim; Jean-Michel Guldmann (pp. 2803-2810).
Vehicle emissions are responsible for a substantial share of urban air pollution concentrations. Various integrated air quality modeling systems have been developed to analyze the consequences of air pollution caused by traffic flows. However, the quantitative relationship between vehicle–kilometers–traveled (VKT) and pollution concentrations while considering wind direction effects has rarely been explored in the context of land-use regression models (LUR). In this research, VKTs occurring within circular buffers around air pollution monitoring stations are simulated, using a traffic assignment model, and weighted by eight wind directions frequencies. The relationships between monitored pollution concentrations and weighted VKTs are estimated using regression analysis. In general, the wind direction weighted VKT variable increases the explanatory power of the models, particularly for nitrogen dioxide and carbon monoxide. The case of ozone is more complex, due to the effects of solar radiation, which appears to overwhelm the effects of wind direction in the afternoon hours. The statistical significance of the weighted VKT variable is high, which makes the models appropriate for impact analysis of traffic flow growth.
Keywords: Vehicle–kilometers–traveled; Wind direction; Pollution concentration; Regression modeling