Check out our New Publishers' Select for Free Articles

Atmospheric Environment (v.45, #26)

Editorial board (pp. i).

Can commonly-used fan-driven air cleaning technologies improve indoor air quality? A literature review by Yinping Zhang; Jinhan Mo; Yuguo Li; Jan Sundell; Pawel Wargocki; Jensen Zhang; John C. Little; Richard Corsi; Qihong Deng; Michael H.K. Leung; Lei Fang; Wenhao Chen; Jinguang Li; Yuexia Sun (pp. 4329-4343).

Air cleaning techniques have been applied worldwide with the goal of improving indoor air quality. The effectiveness of applying these techniques varies widely, and pollutant removal efficiency is usually determined in controlled laboratory environments which may not be realized in practice. Some air cleaners are largely ineffective, and some produce harmful by-products. To summarize what is known regarding the effectiveness of fan-driven air cleaning technologies, a state-of-the-art review of the scientific literature was undertaken by a multidisciplinary panel of experts from Europe, North America, and Asia with expertise in air cleaning, aerosol science, medicine, chemistry and ventilation. The effects on health were not examined. Over 26,000 articles were identified in major literature databases; 400 were selected as being relevant based on their titles and abstracts by the first two authors, who further reduced the number of articles to 160 based on the full texts. These articles were reviewed by the panel using predefined inclusion criteria during their first meeting. Additions were also made by the panel. Of these, 133 articles were finally selected for detailed review. Each article was assessed independently by two members of the panel and then judged by the entire panel during a consensus meeting. During this process 59 articles were deemed conclusive and their results were used for final reporting at their second meeting. The conclusions are that: (1) None of the reviewed technologies was able to effectively remove all indoor pollutants and many were found to generate undesirable by-products during operation. (2) Particle filtration and sorption of gaseous pollutants were among the most effective air cleaning technologies, but there is insufficient information regarding long-term performance and proper maintenance. (3) The existing data make it difficult to extract information such as Clean Air Delivery Rate (CADR), which represents a common benchmark for comparing the performance of different air cleaning technologies. (4) To compare and select suitable indoor air cleaning devices, a labeling system accounting for characteristics such as CADR, energy consumption, volume, harmful by-products, and life span is necessary. For that purpose, a standard test room and condition should be built and studied. (5) Although there is evidence that some air cleaning technologies improve indoor air quality, further research is needed before any of them can be confidently recommended for use in indoor environments.► Active air cleaning technologies are reviewed by an inter multidisciplinary panel. ► The performances including CADR, efficiency, by-products are summarized and compared. ► The problems such as producing harmful by-products etc. are pointed out and analyzed. ► Benchmarks, standard procedure for labeling air cleaner performance are necessary.

Keywords: Indoor air quality (IAQ); Air cleaner; By-product; High efficiency particulate air (HEPA); Sorption; Ultraviolet germicidal irradiation (UVGI); Photocatalytic oxidation (PCO); Thermal catalytic oxidation (TCO); Plasma; Ozone; Ion generator; Electrostatic precipitator; Clean air delivery rate (CADR)Abbreviations; AC; activated carbon; BTEX; benzene, toluene, ethyl benzene, and xylene; CADR; clean air delivery rate; CFM; cubic feet per minute; DBD; dielectric barrier discharge; EPA; Environmental Protection Agency; ESP; electrostatic precipitator; IAQ; indoor air quality; HEPA; high efficiency particulate air; PCO; photocatalytic oxidation; TCO; thermal catalytic oxidation; VOC; volatile organic compound; SOA; secondary organic aerosol; SP; submicron particles; SVOC; semi-volatile organic compound; TVOC; total volatile organic compound; UV-C; ultraviolet C, wavelength range: 280–100 nm; UVGI; ultraviolet germicidal irradiation; WHO; World Health Organization

Mapping particulate matter in alpine regions with satellite and ground-based measurements: An exploratory study for data assimilation by E. Emili; C. Popp; S. Wunderle; M. Zebisch; M. Petitta (pp. 4344-4353).

The objective of this study is the integration of satellite and in-situ measurements of particulate matter (PM₁₀) to provide PM₁₀ maps in Switzerland and South Tyrol (Italy) on an operational daily basis. Satellite retrieval of PM has been widely investigated in the past years, showing moderate potential (uncertainty of ∼30%) but also a number of severe limitations (e.g., due to cloud and snow cover or unknown aerosol extinction profiles). Its actual effectiveness can only be tested by a comparison with the mapping capability of ground-based measurements from existing air-quality networks. Moreover, the integration of both observational systems (assimilation) can improve PM mapping. Herein, we apply a linear model including aerosol optical depth (AOD) from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) and meteorological boundary layer height (BLH) to estimate spatially homogeneous maps of PM₁₀ over the study region in 2008–2009. AOD from MODIS is used to compare the results with those of similar studies. The validation of the satellite maps reveals higher accuracy in flat areas ( r ∼ 0.6, RMSE ∼ 10 μg m⁻³) than in alpine valleys and elevated sites. In contrast, the inverse distance interpolation of in-situ measurements is able to produce more accurate ( r > 0.8, RMSE < 6 μg m⁻³) PM₁₀ maps. An assimilation schema was developed considering the interpolation of ground measurements as a background field, updating it with satellite observations wherever they are available. The accuracy of the assimilated maps is assessed and compared to the background fields. It is found that satellite data is of limited benefit in the considered region due to the good spatial coverage of the ground networks and the difficulties inherent to the satellite PM retrieval over rugged topography. The results of the assimilation are positive (∼1 μg m⁻³ improvement in RMSE) when a number of ground sites (80%) are excluded. It is concluded that satellite data are of higher interest for regions with a sparser distribution of measurement sites (e.g., distance > 100 km between sites).► We analyse the potential of satellites for mapping PM₁₀ in the European alpine region. ► We compare SEVIRI and MODIS PM₁₀ maps with interpolation of ground measurements. ► Satellite-derived PM₁₀ maps are less accurate than the interpolated ones. ► We merge satellite and ground measurements using a data assimilation approach. ► Satellite data only improve PM₁₀ maps when simulating a much sparser in-situ network.

Keywords: Aerosols; PM; ₁₀; Air-quality maps; Satellite PM retrieval; Data assimilation; Interpolation; SEVIRI; MODIS; Mountain region; AOD; Boundary layer

Evaluation of the polyurethane foam (PUF) disk passive air sampler: Computational modeling and experimental measurements by Andrew A. May; Paul Ashman; Jiaoyan Huang; Suresh Dhaniyala; Thomas M. Holsen (pp. 4354-4359).

Computational fluid dynamics (CFD) simulations coupled with wind tunnel-experiments were used to determine the sampling rate (SR) of the widely used polyurethane foam (PUF) disk passive sampler. In the wind-tunnel experiments, water evaporation rates from a water saturated PUF disk installed in the sampler housing were determined by measuring weight loss over time. In addition, a modified passive sampler designed to collect elemental mercury (Hg⁰) with gold-coated filters was used. Experiments were carried out at different wind speeds and various sampler angles. The SRs obtained from wind-tunnel experiments were compared to those obtained from the field by scaling the values by the ratios of air diffusivities. Three-dimensional (3D) CFD simulations were also used to generate SRs for both polychlorinated biphenyls (PCBs) and Hg⁰. Overall, the modeled and measured SRs agree well and are consistent with the values obtained from field studies. As previously observed, the SRs increased linearly with increasing wind speed. In addition, it was determined that the SR was strongly dependent on the angle of the ambient wind. The SRs increased when the base was tilted up pointing into the wind and when the base was tilted down (i.e., such that the top of the sampler was facing the wind) the SR decreased initially and then increased. The results suggest that there may be significant uncertainty in concentrations obtained from passive sampler measurements without knowledge of wind speed and wind angle relative to the sampler.► A passive air sampler was tested to determine its sampling rate (SR). ► 3D CFD simulations were consistent with experimental results. ► The SR was linearly corrected with the external wind speed. ► Sampler orientation and geometry had significant influence on the SR. ► The SR of PCBs and Hg⁰ at 3 m s⁻¹ were 6.8 and 10.2 m³ day⁻¹, respectively.

Keywords: Passive air sampler; PCBs; Mercury; Sampling rate; Sampler orientation

Characterization of the size-distribution of aerosols and particle-bound content of oxygenated PAHs, PAHs, and n-alkanes in urban environments in Afghanistan by Håkan Wingfors; Lars Hägglund; Roger Magnusson (pp. 4360-4369).

Air pollution is a common problem in mega-cities in Asia, resulting in high levels of particulate matter (PM). In this study, 24 h samples of airborne particulate matter (PM_2.5 and PM₁₀) was collected for two weeks in urban locations in Kabul and Mazar-e Sharif, Afghanistan. The samples were analyzed for twenty n-alkanes, fifteen polycyclic aromatic hydrocarbons (PAHs) and eighteen oxygenated PAHs (oxy-PAHs). The results were compared to a reference location in Umeå, Sweden. The main objectives were: to characterize the organic fraction in PM_2.5, with focus on oxy-PAHs, PAHs and n-alkanes, assess relationships between compound groups, and investigate possible source categories. Mean PM₁₀, levels were 260 μg m⁻³, and 334 μg m⁻³ and mean PM_2.5 levels were 86 μg/m³and 68 μg m⁻³ in Kabul and Mazar-e Sharif, respectively. The higher ratio of PM_2.5 to PM₁₀ in Kabul than Mazar-e Sharif or Umeå was reflected in the high number of small particles, as collected by a particle counter. Kabul and Mazar-e Sharif had high levels of PAHs and oxy-PAHs compared to Umeå and previously reported data from Western countries. Generally, the highest individual levels of oxy-PAHs were found for ketones (0.27–33 ng m⁻³), whereas the quinone levels were lower (0.027–3.1 ng m⁻³). High correlations ( r > 0.96) between PAHs and oxy-PAHs were found at both locations. Diagnostics for n-alkanes, such as the carbon preference index, and the most abundant species, C_max, and the presence of unresolved complex mixture indicated a higher contribution from coal and petroleum sources in Kabul. Models generated by principal component analysis (PCA) and positive matrix factorization (PMF) both suggested separate sources for lower molecular weight n-alkanes and higher molecular weight n-alkanes. The PAHs and the oxy-PAHs were not separated in either the PCA or the PMF models, indicating that they had similar sources and are perhaps relatively unspecific as source markers. Nevertheless, the PAHs and oxy-PAHs were good markers for bad air quality in the urban locations in Afghanistan in comparison to data from Western countries. Based on the models and diagnostic ratios it is suggested that traffic and combustion of coal and biomass were the dominating sources of the high levels of particle-bound organic compounds.► Size-distribution data reveal high number of small particles in Kabul. ► Concentrations of particle-bound PAHs and oxy-PAHs were high in Kabul and Mazar-e Sharif. ► Evaluation by source apportionment tools indicated a high load from traffic, coal and biomass. ► PAHs and oxy-PAHs were highly correlated and inseparable by principal component analysis.

Keywords: Kabul; Mazar-e Sharif; PM; _2.5; Positive matrix factorization; Principal component analysis; Source apportionment; Coal; Biomass; Traffic

Factors influencing the variations of PM10 aerosol dust in Klang Valley, Malaysia during the summer by Liew Juneng; Mohd Talib Latif; Fredolin Tangang (pp. 4370-4378).

The associations between the variations of PM10 concentration during summer monsoon dry seasons over the Klang Valley, Malaysia and the local meteorological factors, synoptic weather conditions as well as the regional hotspots number were examined based on simple multiple linear regression analysis. The regressive relationships established, suggest that the variation of PM10 in Klang Valley was governed significantly by all of the examined factors. Local meteorological conditions are among those factors which governed the largest day-to-day variations of PM10 concentration in the Klang Valley areas during the dry season. When augmented by synoptic meteorological variables and foreign emission sources, a remarkable increase in the explained variance was apparent. On the other hand, domestic burning sources only had a minimal impact on PM10 fluctuations. Important synoptic weather patterns which influence the air pollution variations were also identified. These synoptic conditions include the strengthening of the summer monsoon southwesterly winds over the equatorial area. In addition, the formation of cyclonic circulation, associated with typhoon formation over the north-west Pacific and the South China Sea as well as over the Bay of Bengal, are found to have had a profound impact on PM10 variations over the Malaysian region through the modulation of regional moisture distributions.► We investigated factors that influence PM10 variations over Klang Valley areas. ► PM10 variations are governed by local and synoptic weather and emission sources. ► We identified crucial synoptic weather patterns that influence the air pollution. ► These circulations influence the region via modulation of moisture distribution.

Keywords: Tropical air quality; Klang valley; PM10; Local meteorology; Synoptic circulations; Hotspots

Seasonal variation of fine particulate composition in the centre of a UK city by C.L. Martin; J.D. Allan; J. Crosier; T.W. Choularton; H. Coe; M.W. Gallagher (pp. 4379-4389).

In order to better project the impacts of air quality control measures, it is necessary to study the behaviour of particulates beyond mass-based metrics. To study the long term and seasonal trends of particulate chemical composition in Manchester, UK, seven Aerosol Mass Spectrometer (AMS) datasets obtained from ambient sampling in central Manchester over a seven year period have been combined and compared. The size-resolved submicron nitrate, sulphate, ammonium and organic matter data were examined to assess the relative importance of season, local meteorology and synoptic transport in determining ambient concentrations. Systematic trends were observed that were not previously possible through the analysis of individual datasets in isolation.The results obtained here indicate that prevailing westerly winds tend to bring relatively consistent low levels of pollutants, whereas Easterly and Northerly winds bring much more variable pollutant concentrations, whose chemical compositions are strongly dependent on season. Specifically, continental air in the summer brings with it high levels of sulphates whereas in winter similar synoptic conditions and cold ground temperatures tend to induce strong inversions, trapping local pollution and leading to elevated organic matter. Local temperature was also found to be important, with the very low temperatures in winter and very high temperatures in summer giving the greatest concentrations of all components except ammonium nitrate in summer, which began to evaporate at the higher temperatures. These results will assist in evaluating the chemical nature of air pollution episodes and also provide a phenomenological basis for testing chemical transport and exposure models. While the results focus on Manchester, similar phenomena could be expected of a number of UK cities.► We analysed urban aerosol composition from a series of campaigns over 7 years. ► We showed the role of seasonality may have been previously overestimated. ► High nitrate and organic concentrations were associated with winter inversions. ► Regional transport caused elevated sulphate and organic concentrations in summer. ► Nitrate peaked at 15°C in summer due to evaporation at higher temperatures.

Keywords: Urban; Aerosol composition; Aerosol mass spectrometry; Metaanalysis

Short-term nitrogen additions can shift a coastal wetland from a sink to a source of N₂O by Serena Moseman-Valtierra; Rosalinda Gonzalez; Kevin D. Kroeger; Jianwu Tang; Wei Chun Chao; John Crusius; John Bratton; Adrian Green; James Shelton (pp. 4390-4397).

Coastal salt marshes sequester carbon at high rates relative to other ecosystems and emit relatively little methane particularly compared to freshwater wetlands. However, fluxes of all major greenhouse gases (N₂O, CH₄, and CO₂) need to be quantified for accurate assessment of the climatic roles of these ecosystems. Anthropogenic nitrogen inputs (via run-off, atmospheric deposition, and wastewater) impact coastal marshes. To test the hypothesis that a pulse of nitrogen loading may increase greenhouse gas emissions from salt marsh sediments, we compared N₂O, CH₄ and respiratory CO₂ fluxes from nitrate-enriched plots in a Spartina patens marsh (receiving single additions of NaNO₃ equivalent to 1.4 g N m⁻²) to those from control plots (receiving only artificial seawater solutions) in three short-term experiments (July 2009, April 2010, and June 2010). In July 2009, we also compared N₂O and CH₄ fluxes in both opaque and transparent chambers to test the influence of light on gas flux measurements. Background fluxes of N₂O in July 2009 averaged −33 μmol N₂O m⁻² day⁻¹. However, within 1 h of nutrient additions, N₂O fluxes were significantly greater in plots receiving nitrate additions relative to controls in July 2009. Respiratory rates and CH₄ fluxes were not significantly affected. N₂O fluxes were significantly higher in dark than in transparent chambers, averaging 108 and 42 μmol N₂O m⁻² day⁻¹ respectively. After 2 days, when nutrient concentrations returned to background levels, none of the greenhouse gas fluxes differed from controls. In April 2010, N₂O and CH₄ fluxes were not significantly affected by nitrate, possibly due to higher nitrogen demands by growing S. patens plants, but in June 2010 trends of higher N₂O fluxes were again found among nitrate-enriched plots, indicating that responses to nutrient pulses may be strongest during the summer. In terms of carbon equivalents, the highest average N₂O and CH₄ fluxes observed, exceeded half the magnitude of typical daily net carbon sequestration rates by salt marshes. Thus, anthropogenic additions of nitrate to coasts can substantially alter N₂O fluxes from marshes, although substantial temporal variation in these fluxes was observed. To better assess the climatic roles of salt marshes, greenhouse gas emissions need to be studied in the context of chronic nitrogen loads that impact many coastal ecosystems.► Nitrate additions significantly increased N₂O fluxes in a Spartina patens marsh. ► Responses of N₂O fluxes to nitrate varied over 3 dates (July 2009–June 2010). ► Higher N₂O fluxes were measured in dark chambers than in transparent ones. ► N₂O and CH₄ fluxes after N inputs were large enough to reduce net C sequestration.

Keywords: Greenhouse gases; Marsh; Methane; Eutrophication; Plum Island estuary; Global warming potential

Attribution of aerosol radiative forcing over India during the winter monsoon to emissions from source categories and geographical regions by S. Verma; C. Venkataraman; O. Boucher (pp. 4398-4407).

We examine the aerosol radiative effects due to aerosols emitted from different emission sectors (anthropogenic and natural) and originating from different geographical regions within and outside India during the northeast (NE) Indian winter monsoon (January–March). These studies are carried out through aerosol transport simulations in the general circulation (GCM) model of the Laboratoire de Météorologie Dynamique (LMD). The model estimates of aerosol single scattering albedo (SSA) show lower values (0.86–0.92) over the region north to 10°N comprising of the Indian subcontinent, Bay of Bengal, and parts of the Arabian Sea compared to the region south to 10°N where the estimated SSA values lie in the range 0.94–0.98. The model estimated SSA is consistent with the SSA values inferred through measurements on various platforms. Aerosols of anthropogenic origin reduce the incoming solar radiation at the surface by a factor of 10–20 times the reduction due to natural aerosols. At the top-of-atmosphere (TOA), aerosols from biofuel use cause positive forcing compared to the negative forcing from fossil fuel and natural sources in correspondence with the distribution of SSA which is estimated to be the lowest (0.7–0.78) from biofuel combustion emissions. Aerosols originating from India and Africa-west Asia lead to the reduction in surface radiation (−3 to −8 W m⁻²) by 40–60% of the total reduction in surface radiation due to all aerosols over the Indian subcontinent and adjoining ocean. Aerosols originating from India and Africa-west Asia also lead to positive radiative effects at TOA over the Arabian Sea, central India (CNI), with the highest positive radiative effects over the Bay of Bengal and cause either negative or positive effects over the Indo-Gangetic plain (IGP).► Aerosol SSA was estimated to be low over India and the adjoining oceanic regions. ► Aerosols from biofuel combustion emissions exhibit the lowest SSA. ► FF combustion emissions reduce the surface radiation 6–7 times more than the natural. ► Aerosols from India and Africa-west Asia cause large positive TOA radiative effects. ► BC in layers above the high albedo surface leads to positive TOA radiative effects.

Keywords: Radiative effects; Single scattering albedo; Emission sectors and geographical regions

Formation of p-cymene from OH +γ-terpinene: H-atom abstraction from the cyclohexadiene ring structure by Sara M. Aschmann; Janet Arey; Roger Atkinson (pp. 4408-4411).

γ-Terpinene [1-methyl-4-(1-methylethyl)-1,4-cyclohexadiene] is a C₁₀ monoterpene emitted in relatively small amounts from vegetation. p-Cymene [1-methyl-4-(1-methylethyl)benzene or 4-isopropyltoluene] is formed from the OH + γ-terpinene reaction after H-atom abstraction from the two ring CH₂ groups, and its molar formation yield has been measured to be 13.6 ± 2.5%. This corresponds to a rate constant for H-atom abstraction from the ring CH₂ groups in γ-terpinene of (2.41 ± 0.45) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹, a factor of ∼1.7 higher than the literature rate constants for the corresponding H-atom abstraction pathways in the OH radical-initiated reactions of 1,3- and 1,4-cyclohexadiene but significantly lower than the reported overall H-atom abstraction rate constants in the OH + α-terpinene and α-phellandrene reactions.► p-Cymene is formed after H-atom abstraction from the ring CH₂ groups in γ-terpinene. ► p-Cymene data lead to abstraction rate constant of 2.4 × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹. ► Our rate constant is lower than those reported for α-terpinene and α-phellandrene.

Keywords: p; -Cymene; γ-Terpinene; H-atom abstraction; OH radical

Comparing universal kriging and land-use regression for predicting concentrations of gaseous oxides of nitrogen (NO_x) for the Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air) by Laina D. Mercer; Adam A. Szpiro; Lianne Sheppard; Johan Lindström; Sara D. Adar; Ryan W. Allen; Edward L. Avol; Assaf P. Oron; Timothy Larson; L.-J. Sally Liu; Joel D. Kaufman (pp. 4412-4420).

Epidemiological studies that assess the health effects of long-term exposure to ambient air pollution are used to inform public policy. These studies rely on exposure models that use data collected from pollution monitoring sites to predict exposures at subject locations. Land-use regression (LUR) and universal kriging (UK) have been suggested as potential prediction methods. We evaluate these approaches on a dataset including measurements from three seasons in Los Angeles, CA.The measurements of gaseous oxides of nitrogen (NO_x) used in this study are from a “snapshot” sampling campaign that is part of the Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air). The measurements in Los Angeles were collected during three two-week periods in the summer, autumn, and winter, each with about 150 sites. The design included clusters of monitors on either side of busy roads to capture near-field gradients of traffic-related pollution.LUR and UK prediction models were created using geographic information system (GIS)-based covariates. Selection of covariates was based on 10-fold cross-validated (CV) R² and root mean square error (RMSE). Since UK requires specialized software, a computationally simpler two-step procedure was also employed to approximate fitting the UK model using readily available regression and GIS software.UK models consistently performed as well as or better than the analogous LUR models. The best CV R² values for season-specific UK models predicting log(NO_x) were 0.75, 0.72, and 0.74 (CV RMSE 0.20, 0.17, and 0.15) for summer, autumn, and winter, respectively. The best CV R² values for season-specific LUR models predicting log(NO_x) were 0.74, 0.60, and 0.67 (CV RMSE 0.20, 0.20, and 0.17). The two-stage approximation to UK also performed better than LUR and nearly as well as the full UK model with CV R² values 0.75, 0.70, and 0.70 (CV RMSE 0.20, 0.17, and 0.17) for summer, autumn, and winter, respectively.High quality LUR and UK prediction models for NO_x in Los Angeles were developed for the three seasons based on data collected for MESA Air. In our study, UK consistently outperformed LUR. Similarly, the 2-step approach was more effective than the LUR models, with performance equal to or slightly worse than UK.► Land-use regression (LUR) and universal kriging (UK) predict NO_x in Los Angeles. ► UK with traffic, population, land-use, and geographic covariates outperforms LUR. ► Optimal model choice varies between three seasons. ► Nearly-optimal model performs well in all three seasons.

Keywords: Universal kriging; Land-use regression; Spatial modeling; Air pollution; Exposure assessment; Los AngelesAbbreviations; UK; universal kriging; LUR; land-use regression; CV; cross validated; RMSE; root mean square error

Daytime meteorological structures causing elevated photochemical oxidants concentrations in north Kanto, Japan by Shinri Hosoi; Hiroshi Yoshikado; Kazuhiko Sekiguchi; Qingyue Wang; Kazuhiko Sakamoto (pp. 4421-4428).

The north Kanto area is about 150 km north of the heavily populated and industrialized Tokyo metropolis, and local emissions of photochemical oxidants (Ox) precursors are limited because of little anthropogenic emission. Nevertheless, high Ox concentrations exceeding the warning level for Ox (>120 ppbv, 1-h average) are often observed there. We recently reported that high Ox concentrations in the north Kanto area occur under the coupled conditions of a southerly extended sea breeze transporting Ox from the southern urban area and a subsidence inversion layer restricting vertical dispersion. However, these meteorological conditions do not always lead to high Ox concentrations. To identify other conditions affecting the occurrence of high Ox concentrations in north Kanto, we examined meteorological conditions. Key meteorological structures were two thermal lows occurring on sunny days in districts neighboring the Kanto district on the west and north. When both thermal lows persisted in their morning positions until evening, a southerly sea breeze toward the thermal lows was maintained throughout the afternoon, transporting high levels of Ox formed in south Kanto, including Tokyo, to north Kanto. When a thermal low present only in the western district moved eastward to cover the central Kanto area during the afternoon, isobars in north Kanto acquired an east–west orientation and observed wind direction became consistently northerly, thus restricting transport of high Ox from south Kanto.► Two thermal lows tend to occur on west and north of Kanto in sunny summer days. ► These lows promote southerly sea breeze, which transports high Ox to north Kanto. ► When the low occurs only on west, Ox in north Kanto remain low by northerly wind.

Keywords: High oxidants concentration; Local meteorological conditions; Thermal low; Isobar; North Kanto

Influence of blocking effect of mountain and local front on two Asian-dust events observed at Mt. Haruna and Tsukuba in Kanto, Japan, in 2007 by Yayoi Inomata; Yasuhito Igarashi; Hiroaki Naoe; Hiroshi Takahashi; Atsushi Shimizu; Nobuo Sugimoto; Taichu Y. Tanaka (pp. 4429-4441).

Aerosol number concentrations were continuously measured at sites at Tsukuba and Mt. Haruna on the Kanto region of Japan by using optical particle counters (OPCs) from February to June 2007. Three specific dust events captured at the sites were analyzed by using lidar, backward trajectories, and model simulation in detail. The temporal variations in aerosol concentrations in the two Asian-dust events (K1 event: 31 March–3 April; K2 event: 25–28 May) were similar. Dust particles (≥2.0 μm in diameter) were transported in association with a synoptic-scale cold front, and they arrived at the Tsukuba site about 8 h after they were observed at the Mt. Haruna site, in association with the dissipation of a local front formed ahead of the cold front. However, the inflow patterns of dust particles differed between the K1 and K2 events. The K1 event flowed onto the Kanto Plain, detouring around the mountainous region, whereas the K2 event directly flowed across the mountains. The difference in inflow pattern was probably due to the blocking effects of the mountains and the formation of a stable layer near the surface. Preceding the dust plume arrival, an increase in the number concentration of small-aerosol particles (0.3–1.0 μm in diameter), which are considered to be spherical by lidar, was observed, but only at the Tsukuba site. This increase was possibly due to anthropogenic pollution transported over long distances from the continent and from domestic sources in the Kanto region. The third event was a local dust event, because it was observed only at the Tsukuba site (on 13 and 14 March) under dry conditions (10 m s⁻¹).► The two Asian-dust events were observed behind a synoptic-scale cold front. ► Blocking effects of mountains and formation of stable layer dominated dust inflow. ► The dust was observed at Tsukuba after the dissipation of local front. ► An increase of small-aerosol concentration was observed at only the Tsukuba. ► The occurrence of dust was different between the Asian and the local dust events.

Keywords: Asian dust; Local dust; Blocking effect of mountain; Local front; Froude number

Variation in characteristics of ambient particulate matter at eight locations in the Netherlands – The RAPTES project by Maciej Strak; Maaike Steenhof; Krystal J. Godri; Ilse Gosens; Ian S. Mudway; Flemming R. Cassee; Erik Lebret; Bert Brunekreef; Frank J. Kelly; Roy M. Harrison; Gerard Hoek; Nicole A.H. Janssen (pp. 4442-4453).

Numerous epidemiological studies have shown health effects related to short- and long-term exposure to elevated levels of ambient particulate matter (PM). It is not clear however which specific characteristics (e.g., size, components) or sources of PM are responsible for the observed effects.The aim of RAPTES (Risk of Airborne Particles: a Toxicological–Epidemiological hybrid Study) was to investigate which specific physical, chemical or oxidative characteristics of ambient PM are associated with adverse effects of PM on health. This was done by performing experimental exposure of human volunteers to air pollution at several real-world settings that had high contrast and low correlation between several PM characteristics.For this goal, eight sites in the Netherlands that differed in local PM emission sources were chosen for extensive air pollution characterization. Measurement sites included an underground train station, three different road traffic sites, an animal farm, a sea harbor, a site located in the vicinity of steelworks, and an urban background site. Five- to six-hours average concentration measurements at each site were made between June 2007 and October 2009. We measured PM₁₀, PM_2.5, particle number concentration (PNC), oxidative potential of PM, absorbance, endotoxin content, as well as elemental and chemical composition of PM, and gaseous pollutants concentrations. This paper presents a detailed characterization of particulate air pollution at the sampling sites.We found significant differences in all PM characteristics between the sites. The underground train station, compared to each outdoor location, had substantially higher concentrations of nearly all PM characteristics. The average PM₁₀ and PM_2.5 mass concentrations at the underground train station were 394 μg m⁻³ and 137 μg m⁻³, respectively, which was 14.1 and 7.6 times higher than the urban background. The sum of the concentrations of trace metals in fine and coarse PM was nearly 20 times above the outdoor levels. Elemental carbon (EC) was elevated at the underground site in the fine but also in the coarse mode, in contrast to the traffic sites where EC was predominantly found in fine PM. The highest concentrations and contrasts in PNC were at the traffic sites (between 45,000 and 80,000 particles cm⁻³), which was several times higher than measured at any other site. Correlations of PNC with metals, PM₁₀, PM_2.5 and absorbance were low to moderate, while correlations between PM₁₀, PM_2.5 and the metals Cu and Fe were high. After excluding the underground train station data, correlations between PM10, EC and metals decreased whereas the correlation between PNC and EC increased.We conclude that we were able to successfully identify and characterize real-world situations with very different particle characteristics. High contrast and low correlations between PM characteristics, as well as consistency of these differences across sampling campaigns, provide a good basis for identifying health relevant PM characteristics in the upcoming analysis.► We successfully identified and characterized real-world situations with very different PM characteristics. ► Underground train station had the highest concentrations of almost every PM characteristic. ► Correlations between PM characteristics were low enough to investigate their independent health effects.

Keywords: Air pollution; PM; Monitoring; Particle characteristics; Underground; Harbor

Mercury in cloud water collected on Mt. Bamboo in northern Taiwan during the northeast monsoon season by Guey-Rong Sheu; Neng-Huei Lin (pp. 4454-4462).

Cloud water was sampled on Mt. Bamboo in northern Taiwan in January–March 2009 for total mercury (Hg) analysis. This was the first cloud water Hg measurement reported from the downwind region of East Asia, which is the major Hg emission source region globally. A total of 11 cloud events were encountered, and 129 and 316 cloud water samples were collected for Hg and major ion analyses, respectively. The mean cloud water pH was 4.14. Cl⁻ and Na⁺ were the major ions in cloud water. About 2/3 of the samples had molar ratios of Cl⁻/Na⁺ close to the seawater ratio of 1.12, demonstrating a significant impact of sea salt aerosols on cloud water chemistry. On the other hand, 90% of the measuredSO42− was non-sea-salt-SO42− (nss-SO42−), highlighting the influence of human activities. Concentrations of Hg ranged between 0.5 and 165.5 ng L⁻¹, with a mean of 9.6 ng L⁻¹. Elevated Hg concentrations were usually associated with highly acidic samples. Hg concentrations were well correlated with major ion concentrations, especially withNO3−, K⁺, nss-SO42−, andNH4+. The results of element ratio calculations, correlation analyses and trajectory analyses indicated that, in addition to sea salt aerosols, coal combustion, industrial activities, and biomass/biofuel burning in the East Asian continent could have contributed to the measured Hg in the cloud water. The contribution of below-cloud scavenging to rainwater Hg was evaluated by comparing the cloud water Hg concentrations to the rainwater Hg concentrations sampled at a nearby mountain site and at an urban site. The mean rainwater Hg values at the mountain site (11.6 ng L⁻¹) and at the urban site (19.2 ng L⁻¹) were all higher than the cloud water value, demonstrating the below-cloud scavenging contribution. Nonetheless, the below-cloud scavenging contribution was more significant in the urban area than in the mountain area. About 28% and 91% of the rainwater Hg at the mountain and urban sites could be attributed to the below-cloud scavenging, respectively.► Cloud water was sampled at a high-elevation site for total mercury (Hg) analysis. ► Elevated Hg concentrations were usually associated with highly acidic samples. ► Hg concentrations were well correlated with major ion concentrations. ► The East Asian anthropogenic Hg emissions can contribute to the measured Hg concentrations.

Keywords: Biomass burning; Coal combustion; Long-range transport; Sea salt aerosols

Carbonaceous aerosols in an urban tunnel by Travis Ancelet; Perry K. Davy; William J. Trompetter; Andreas Markwitz; David C. Weatherburn (pp. 4463-4469).

Particulate matter in the Mount Victoria Tunnel, an urban road tunnel 623 m in length with an average traffic volume of 2070–2300 vehicles per hour located in Wellington, New Zealand, was studied to gain an understanding of carbonaceous species emitted from motor vehicles. The average PM_2.5 concentration during peak hours in the tunnel was found to be 67.6 ± 19.4 μg m⁻³. Analysis of carbonaceous species present (OC, EC, TC) was performed by both the NIOSH and IMPROVE thermal/optical protocols and carbonaceous species were found to make up 63–73% of the total PM in the tunnel. Comparison of TC concentrations obtained from each protocol revealed that no significant difference was present between the two protocols. Black carbon (BC), also used as a measure of EC, was determined using light reflection and BC values did not differ significantly from EC concentrations determined using the NIOSH and IMPROVE protocols. TC was also determined using EA/IRMS and it was found that TC concentrations from EA/IRMS directly correlated with TC results obtained using the NIOSH protocol. Stable isotope analysis of the PM_2.5 yielded δ¹³C values from −24.7 to −28.3‰, typical of motor vehicles. Analysis of particle-phase PAHs by thermal desorption GC/MS revealed an average total PAH concentration of 70.0 ± 4.1 ng m⁻³ and PAHs were found to contribute 0.10% of total PM_2.5 in the tunnel. PAH emissions in the tunnel were found to be enriched in low molecular weight PAHs, indicative of emissions from diesel-fueled vehicles. Analysis of individual particle composition and morphology revealed that most particles were carbonaceous species that formed large, amorphous agglomerates made up of smaller spherules.► We studied carbonaceous aerosols in an urban tunnel. ► Carbonaceous species were quantified using various methods. ► EA/IRMS and NIOSH total carbon directly correlated. ► PAH analysis revealed diesel emissions to be dominant. ► PM_2.5 was largely carbonaceous.

Keywords: Tunnel; Aerosol; PAH; SEM; OC; EC; EA/IRMS

Concentrations of fine, ultrafine, and black carbon particles in auto-rickshaws in New Delhi, India by Joshua S. Apte; Thomas W. Kirchstetter; Alexander H. Reich; Shyam J. Deshpande; Geetanjali Kaushik; Arvind Chel; Julian D. Marshall; William W. Nazaroff (pp. 4470-4480).

Concentrations of air pollutants from vehicles are elevated along roadways, indicating that human exposure in transportation microenvironments may not be adequately characterized by centrally located monitors. We report results from ∼180 h of real-time measurements of fine particle and black carbon mass concentration (PM_2.5, BC) and ultrafine particle number concentration (PN) inside a common vehicle, the auto-rickshaw, in New Delhi, India. Measured exposure concentrations are much higher in this study (geometric mean for ∼60 trip-averaged concentrations: 190 μg m⁻³ PM_2.5, 42 μg m⁻³ BC, 280 × 10³ particles cm⁻³; GSD ∼1.3 for all three pollutants) than reported for transportation microenvironments in other megacities. In-vehicle concentrations exceeded simultaneously measured ambient levels by 1.5× for PM_2.5, 3.6× for BC, and 8.4× for PN. Short-duration peak concentrations (averaging time: 10 s), attributable to exhaust plumes of nearby vehicles, were greater than 300 μg m⁻³ for PM_2.5, 85 μg m⁻³ for BC, and 650 × 10³ particles cm⁻³ for PN. The incremental increase of within-vehicle concentration above ambient levels—which we attribute to in- and near-roadway emission sources—accounted for 30%, 68% and 86% of time-averaged in-vehicle PM_2.5, BC and PN concentrations, respectively. Based on these results, we estimate that one’s exposure during a daily commute by auto-rickshaw in Delhi is as least as large as full-day exposures experienced by urban residents of many high-income countries. This study illuminates an environmental health concern that may be common in many populous, low-income cities.Display Omitted► We collected ∼180 h of particle exposure measurements in New Delhi auto-rickshaws. ► In-vehicle particle concentrations high relative to New Delhi background levels. ► Roadway emissions are dominant source of in-vehicle UFP and BC exposure. ► Concentrations among highest reported for a megacity transportation setting.

Keywords: Particulate matter; Megacity; Microenvironment; Urban air quality; Transportation; Exposure

A cellphone based system for large-scale monitoring of black carbon by N. Ramanathan; M. Lukac; T. Ahmed; A. Kar; P.S. Praveen; T. Honles; I. Leong; I.H. Rehman; J.J. Schauer; V. Ramanathan (pp. 4481-4487).

Black carbon aerosols are a major component of soot and are also a major contributor to global and regional climate change. Reliable and cost-effective systems to measure near-surface black carbon (BC) mass concentrations (hereafter denoted as [BC]) globally are necessary to validate air pollution and climate models and to evaluate the effectiveness of BC mitigation actions. Toward this goal we describe a new wireless, low-cost, ultra low-power, BC cellphone based monitoring system (BC_CBM). BC_CBM integrates a Miniaturized Aerosol filter Sampler (MAS) with a cellphone for filter image collection, transmission and image analysis for determining [BC] in real time. The BC aerosols in the air accumulate on the MAS quartz filter, resulting in a coloration of the filter. A photograph of the filter is captured by the cellphone camera and transmitted by the cellphone to the analytics component of BC_CBM. The analytics component compares the image with a calibrated reference scale (also included in the photograph) to estimate [BC]. We demonstrate with field data collected from vastly differing environments, ranging from southern California to rural regions in the Indo-Gangetic plains of Northern India, that the total BC deposited on the filter is directly and uniquely related to the reflectance of the filter in the red wavelength, irrespective of its source or how the particles were deposited. [BC] varied from 0.1 to 1μgm⁻³ in Southern California and from 10 to 200μgm⁻³ in rural India in our field studies. In spite of the 3 orders of magnitude variation in [BC], the BC_CBM system was able to determine the [BC] well within the experimental error of two independent reference instruments for both indoor air and outdoor ambient air.Accurate, global-scale measurements of [BC] in urban and remote rural locations, enabled by the wireless, low-cost, ultra low-power operation of BC_CBM, will make it possible to better capture the large spatial and temporal variations in [BC], informing climate science, health, and policy.► Low-power, low-cost cellphone system for black carbon monitoring (BC_CBM) described. ► Cellphone captures and uploads images of filters exposed to ambient aerosols. ► Field results show filter color is uniquely related to quantity of BC on filter. ► BC_CBM accuracy within experimental error of 2 reference methods. ► Field accuracy demonstrates BC_CBM potential for large-scale BC monitoring.

Keywords: Black carbon monitoring; Cellphone sensing; Soot sensor

A simplified approach for solving coagulation–diffusion equation to estimate atmospheric background particle number loading factors contributed by emissions from localized sources by S. Anand; Y.S. Mayya (pp. 4488-4496).

Coagulation and condensation/evaporation combined with atmospheric dispersion are the main processes responsible for the evolution of aerosol particle size distributions and number concentrations emitted from localized sources. A crucial question is: what fraction of freshly emitted particles survive intra-coagulation effect to persist in the atmosphere and become available for further interaction with background aerosols?. The difficulty in estimating this quantity, designated as the number survival fraction, arises due chiefly to the joint action of atmospheric diffusion with nonlinear coagulation effects which are computationally intensive to handle. We provide a simplified approach to evaluate this quantity in the context of instantaneous (puff) and continuous (plume) releases based on a reduction of the respective coagulation–diffusion equations under the assumption of a constant coagulation kernel ( K). The condensation/evaporation processes, being number conserving, are not included in the study. The approach consists of constructing moment equations for the evolution of number concentration and variance of the spatial extension of puff or plume in terms of either time or downstream distance. The puff model, applicable to instantaneous releases is solved within a 3-D, spherically symmetric framework, under an additional assumption of a constant diffusion coefficient ( D) which renders itself amenable to a closed form solution that provides a benchmark for developing the solution to the plume model. The latter case, corresponding to continuous releases, is discussed within a 2-D framework under the assumptions of constant advection velocity ( U) and space dependent diffusion coefficient expressed in terms of turbulent energy dissipation rate ( ɛ). The study brings out the special effect of the coagulation-induced flattening of the spatial concentration profiles because of which particle sizes will be larger at the centre of a Gaussian puff. For a puff of initial width b₀ consisting of N₀ particles, we obtain a formula for the number survival fraction asψpuff(∞)=(1+5A/4)−4/5 where,A=KN0/{4(2π)3/2Db0}. For plume of initial width σ₀ emitting S₀ particles per unit time, the formula for the survival fraction obtained by fitting the numerical solutions is obtained asψplume(∞)=(1+1.32μ)−0.76 where,μ=KS0/{63Uσ04/3(Cɛ)1/3} and C is a constant (∼0.8). The implication of these results such as robustness with respect to uncertainties in the choice of the initial data and applications for a few practically important problems such as vehicular emissions, forest fires, etc are discussed.Display Omitted► We examine the importance of coagulation process in dispersing aerosol puffs and plumes near emission sources. ► We propose simple formulae for ultimate survival fraction and number loading factors for puff and plume releases. ► The study demonstrates robustness of the ultimate particle loading rates with respect to the initial data, for large scale emissions.

Keywords: Coagulation; Dispersion; Survival fraction; Aerosol emissions

Non-Darwinian evolution for the source detection of atmospheric releases by Guido Cervone; Pasquale Franzese (pp. 4497-4506).

A non-Darwinian evolutionary algorithm is presented as search engine to identify the characteristics of a source of atmospheric pollutants, given a set of concentration measurements. The algorithm drives iteratively a forward dispersion model from tentative sources toward the real source. The solutions of non-Darwinian evolution processes are not generated through pseudo-random operators, unlike traditional evolutionary algorithms, but through a reasoning process based on machine learning rule generation and instantiation. The new algorithm is tested with both a synthetic case and with the Prairie Grass field experiment. To further test the capabilities of the algorithm to work in real-world scenarios, the source identification of all Prairie Grass releases was performed with a decreasing number of sensor measurements, and a relationship is found between the precision of the solution, the number of sensors available, and the levels of concentration measured by the sensors.The proposed methodology can be used for a variety of optimization problems, and is particularly suited for problems where the operations needed for evaluating new candidate solutions are computationally expensive.► A non-Darwinian evolutionary algorithm for the source characterization of atmospheric pollutants. ► The algorithm is tested with a synthetic case and with the Prairie Grass field experiment. ► The source identification is performed with a decreasing number of observations. ► A relationship is found between the error, the number of sensors, and their concentration.

Keywords: Non-Darwinian evolution; Source characterization; Evolutionary algorithms; Dispersion modeling

A new gas-phase condensed mechanism of isoprene-NO_x photooxidation by Haofei Zhang; Weruka Rattanavaraha; Yang Zhou; Jyoti Bapat; Elias P. Rosen; Kenneth G. Sexton; Richard M. Kamens (pp. 4507-4521).

A new condensed gas-phase isoprene mechanism is developed and evaluated, using O₃, nitrogen oxides (NO_x), and volatile organic compounds (VOC) data from over twenty isoprene experiments. Experiments were performed in two UNC dual outdoor smog chambers using natural sunlight, with different NO_x levels, and with or without the presence of an urban hydrocarbon environment. The mechanism uses the Carbon Bond mechanism (CB05) to represent inorganic chemistry and hydrocarbons other than isoprene. It was designed so that the chemistry related to secondary organic aerosol (SOA) formation can be incorporated, and thus it can be further expanded into a gas-aerosol-phase mechanism. A box model framework of this new isoprene mechanism is able to reasonably simulate most experimental data at HC/NO_x ratios that range from 0.3 to 18. An intercomparison was performed between the isoprene kinetics developed in this study and other isoprene chemistry that is included in other kinetic mechanisms, including MCM v3.1, SAPRC99, SAPRC07, MIM2, CB4 and CB05. The results indicate that most current mechanisms tend to under-predict ozone levels to different extents, while the new mechanism simulates the UNC smog chamber O₃ data better than the others in most cases, especially at higher HC/NO_x ratios. Further, the new mechanism performs reasonably well in modeling outdoor smog chamber experiments with isoprene in an urban hydrocarbon mixture. In addition, a HO_x (OH + HO₂) recycling scheme based upon and was implemented in MCM v3.1 and the new UNC mechanism, since it has been recently been suggested to be very important under low-NO_x conditions. Although our experimental data base is very limited for the low-NO_x condition, the isoprene chemistry tended to significantly over-predict observed chamber O₃. This suggests that more low-NO_x experiments and further confirmation of current theoretical studies are needed.► A new condensed isoprene mechanism is developed using most recent study results. ► Was designed to incorporate secondary organic aerosol formation. ► Intercomparison shows better performance than most current mechanisms. ► Simulations of isoprene in an urban hydrocarbon environment were very reasonable.

Keywords: Isoprene; Carbon Bond mechanism; HC/NO; _x; Condensed mechanism

Field evaluation of portable and central site PM samplers emphasizing additive and differential mass concentration estimates by Fu-Lin Chen; Robert Vanderpool; Ronald Williams; Fred Dimmick; Brett D. Grover; Russell Long; Robert Murdoch (pp. 4522-4527).

The US Environmental Protection Agency (EPA) published a National Ambient Air Quality Standard (NAAQS) and the accompanying Federal Reference Method (FRM) for PM₁₀ in 1987. The EPA revised the particle standards and FRM in 1997 to include PM_2.5. In 2005, EPA proposed revisions to this NAAQS to include PM_10–2.5 but only finalized revisions with a PM_2.5 FRM and the development of a national monitoring network in 2006. Presently, no EPA designated reference or equivalent method sampler has the ability to directly measure the mass concentrations of PM₁₀, PM_10–2.5, and PM_2.5 simultaneously. An additive approach has been used for samplers like the dichotomous monitors to calculate PM₁₀ mass concentrations from independent measures of PM_10–2.5 and PM_2.5 (i.e. PM₁₀=PM_10–2.5+PM_2.5). A differential approach has been used to calculate PM_10–2.5 from identical collocated PM₁₀ and PM_2.5 samplers (i.e. PM_10–2.5=PM₁₀–PM_2.5). Since these two approaches have been used widely for PM measurements, it is informative to evaluate their precision and comparability.EPA performed collocated tests of five different particle samplers in the Research Triangle Park area of North Carolina to evaluate the comparability and to characterize the additive and differential approaches used to determine particle mass concentrations. The intra-sampler precision of MiniVol, Omni, and dichotomous samplers was less than 8.4%. The precision of PM₁₀ measurements using the additive approach with dichotomous samplers was less than 3.5%. The poorest precision of the various PM_10–2.5 differential approaches was less than 15.1%. No zero or negative PM_10–2.5 concentrations were calculated using the differential approach. A coefficient of determination of 0.81 or higher was obtained for all paired comparison of PM_10–2.5. The reported test results show that concentrations calculated from both the additive and differential approaches generally agree among the portable samplers, the more established dichotomous sampler and the Federal Reference Methods► The study investigated additive and differential approaches for mass estimation. ► Precision error of direct measurements was less than 8.4% from all samplers. ► Lower PM₁₀ and higher PM_2.5 caused uncertainty in PM_10–2.5 estimates. ► PM_10–2.5 exhibited slightly poorer agreement under various test conditions.

Keywords: PM; ₁₀; PM; _10–2.5; PM; _2.5; Additive and differential approaches

Iron speciation in urban dust by Evert J. Elzinga; Yuan Gao; Jeffrey P. Fitts; Ryan Tappero (pp. 4528-4532).

An improved understanding of anthropogenic impacts on ocean fertility requires knowledge of anthropogenic dust mineralogy and associated Fe speciation as a critical step toward developing Fe solubility models constrained by mineralogical composition. This study explored the utility of micro-focused X-ray absorption spectroscopy (μ-XAS) in characterizing the speciation of Fe in urban dust samples. A micro-focused beam of 10 × 7 μm made possible the measurement of the Fe K edge XAS spectra of individual dust particles in the PM5.6 size fraction collected in Newark, New Jersey, USA. Spectral analysis indicated the presence of mixtures of Fe-containing minerals within individual dust particles; we observed significant magnetite content along with other Fe(III)-(hydr)oxide minerals which could not be conclusively identified. Our data indicate that detailed quantitative determination of Fe speciation requires extended energy scans to constrain the types and relative abundance of Fe species present. We observe heterogeneity in Fe speciation at the dust particle level, which underscores the importance of analyzing a statistically adequate number of particles within each dust sample. Where possible, μ-XAS measurements should be complemented with additional characterization techniques such as μ-XRD and bulk XAS to obtain a comprehensive picture of the Fe speciation in dust materials. X-ray microprobes should be used to complement bulk methods used to determine particle composition, methods that fail to record particle heterogeneity.

Keywords: Urban dust; Iron; Speciation; Micro-focused X-ray absorption spectroscopy

Sections

Personal tools

Atmospheric Environment (v.45, #26)

Sections

Personal tools

Local resources

Atmospheric Environment (v.45, #26)