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Atmospheric Environment (v.40, #40)

Editorial board (pp. i).

Verification of energy consumption in China during 1996–2003 by using satellite observational data by Hajime Akimoto; Toshimasa Ohara; Jun-ichi Kurokawa; Nobuhiro Horii (pp. 7663-7667).
There is substantial difference in the coal consumption data in China during 1996–2003 among the three official energy statistics; the province-by-province data in the China Energy Statistics Yearbook (PBP-CESY), the energy balance tables by International Energy Agency (IEA2004) [2004, Energy Statistics of Non-OECD Countries. IEA, Paris], and the country-total data in the China Energy Statistics Yearbook (CT-CESY). Verification of these data was made by GOME satellite observational data for tropospheric NO2 column density in Northern China Plain reported by Irie et al. [2005, Evaluation of long-termtropospheric NO2 data obtained by GOME over East Asia in 1996–2002. Geophysical Research Letter 32(11), L11810, doi: 10.1029/2005GL022770] and Richter et al. [2005, Increase in tropospheric nitrogen dioxide over China observed from space. Nature 437, 129–130]. The NO2 column increase from 1996 to 2002 averaged for the two reports is about 50%, whereas the NO x emission increases based on the PBP-CESY and IEA2004 are 25% and 15%, respectively, and that for CT-CESY is even lower. The discrepancy of the increasing trends between the satellite data and the PBP-CESY emission inventory could be within the uncertainty level with a reservation that the increase in total fuel consumption in PBP-CESY may still be underestimated particularly after the year of 1999. The increasing rates of NO x emissions during 1996–2002 calculated by using the IEA2004 and CT-CESY statistics are apparently underestimated beyond the uncertainty level of the satellite observation, and they are recommended not to be used for emission inventory studies in China during the period.

Keywords: Emission inventory; NO; Tropospheric NO; 2; Greenhouse gas; Air pollutant; China


Estimating fugitive dust emission rates using an environmental boundary layer wind tunnel by Jason A. Roney; Bruce R. White (pp. 7668-7685).
Emissions from fugitive dust due to erosion of “natural� wind-blown surfaces are an increasingly important part of PM10 (particulate matter with sizes of 10μm aerodynamic diameter) emission inventories. These inventories are particularly important to State Implementation Plans (SIP), the plan required for each state to file with the Federal government indicating how they will comply with the Federal Clean Air Act (FCAA). However, techniques for determining the fugitive dust contribution to over all PM10 emissions are still in their developmental stages. In the past, the methods have included field monitoring stations, specialized field studies and field wind-tunnel studies. The measurements made in this paper allow for systematic determination of PM10 emission rates through the use of an environmental boundary layer wind tunnel in the laboratory. Near surface steady-state concentration profiles and velocity profiles are obtained in order to use a control volume approach to estimate emission rates. This methodology is applied to soils retrieved from the nation's single largest PM10 source, Owens (dry) Lake in California, to estimate emission rates during active storm periods. The estimated emission rates are comparable to those obtained from field studies and lend to the validity of this method for determining fugitive dust emission rates.

Keywords: Particulate matter; Fugitive dust; Emission rates; Wind tunnel; Aerosols


Field evaluation of two diffusive samplers and two adsorbent media to determine 1,3-butadiene and benzene levels in air by Bo Strandberg; Anna-Lena Sunesson; Margit Sundgren; Jan-Olof Levin; Gerd Sällsten; Lars Barregard (pp. 7686-7695).
Two types of diffusive samplers, both of which are compatible with thermal desorption, but differ in their geometry—SKC-Ultra (badge-type) and Radiello (radial symmetry-type)—were evaluated indoors and outdoors under varying temperature, humidity and wind speed conditions, using the graphitized adsorbents Carbopack X or Carbograph 5 to measure 1,3-butadiene and benzene in ambient air. The results obtained by diffusive sampling were compared with results obtained using a conventional active sampling method over both long (1 week) and shorter periods (6–24h). Analysis and detection were performed using an automatic thermal desorber (ATD) connected to a gas chromatograph-flame ionization detector (GC/FID). Results from each sampler and adsorbent combination were examined using ordinary or multiple linear regression analysis. The overall uncertainty (OU) was also determined. In general, the results obtained with both samplers showed good agreement with those obtained by active sampling. Carbopack X appeared to be a more efficient adsorbent than Carbograph 5 for 1,3-butadiene, but the two adsorbents were equivalent for benzene. No effects of either humidity or air velocity were observed. Minor temperature effects were observed for both samplers for 1,3-butadiene. In summary, the results confirmed the accuracy of sampling rates previously determined for the two samplers and adsorbents. We consider the two samplers to be suitable for stationary and personal monitoring for the general population of 1,3-butadiene and benzene in various environments, indoors and outdoors. They are almost independent of meteorological conditions and may be suitable for monitoring industrial atmospheres.

Keywords: VOCs; Air contaminants; Diffusive samplers; Monitoring; Exposure


Simulation of aerosol radiative properties with the ORISAM-RAD model during a pollution event (ESCOMPTE 2001) by M. Mallet; V. Pont; C. Liousse; J.C. Roger; P. Dubuisson (pp. 7696-7705).
The aim of this study is to present the organic and inorganic spectral aerosol module-radiative (ORISAM-RAD) module, allowing the 3D distribution of aerosol radiative properties (aerosol optical depth, single scattering albedo and asymmetry parameter) from the ORISAM module. In this work, we test ORISAM-RAD for one selected day (24th June) during the ESCOMPTE (expérience sur site pour contraindre les modèles de pollution atmosphérique et de transport d’emissions) experiment for an urban/industrial aerosol type. The particle radiative properties obtained from in situ and AERONET observations are used to validate our simulations. In a first time, simulations obtained from ORISAM-RAD indicate high aerosol optical depth (AOD)∼0.50–0.70±0.02 (at 440nm) in the aerosol pollution plume, slightly lower (∼10–20%) than AERONET retrievals. In a second time, simulations of the single scattering albedo ( ωo) have been found to well reproduce the high spatial heterogeneities observed over this domain. Concerning the asymmetry parameter ( g), ORISAM-RAD simulations reveal quite uniform values over the whole ESCOMPTE domain, comprised between 0.61±0.01 and 0.65±0.01 (at 440nm), in excellent agreement with ground based in situ measurements and AERONET retrievals. Finally, the outputs of ORISAM-RAD have been used in a radiative transfer model in order to simulate the diurnal direct radiative forcing at different locations (urban, industrial and rural). We show that anthropogenic aerosols strongly decrease surface solar radiation, with diurnal mean surface forcings comprised between −29.0±2.9 and −38.6±3.9Wm−2, depending on the sites. This decrease is due to the reflection of solar radiations back to space (−7.3±0.8<Δ FTOA<−12.3±1.2Wm−2) and to its absorption into the aerosol layer (21.1±2.1<Δ FATM<26.3±2.6Wm−2). These values are found to be consistent with those measured at local scale.

Keywords: Aerosol model; Aerosol radiative properties; Direct radiative forcing


Ambient halocarbon mixing ratios in 45 Chinese cities by Barbara Barletta; Simone Meinardi; Isobel J. Simpson; F. Sherwood Rowland; C.-Y. Chuen-Yu Chan; Xinming Wang; Shichun Zou; Lo Yin Chan; Donald R. Blake (pp. 7706-7719).
During this study 158 whole air samples were collected in 45 Chinese cities in January and February 2001. The spatial distribution of different classes of halocarbons in the Chinese urban atmosphere, including chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), Halon-1211, and other chlorinated compounds is presented and discussed. Most of these compounds were enhanced compared to background levels. However, the mean enhancement of CFCs was relatively small, with CFC-12 and CFC-11 increases of 6% (range 1–31%) and 10% (range 2–89%), respectively, with respect to the global background. On the contrary, strongly enhanced levels of CFC replacement compounds and halogenated compounds used as solvents were measured. The average Halon-1211 concentration exceeded the background of 4.3pptv by 75% and was higher than 10pptv in several cities. Methyl chloride mixing ratios were also strongly elevated (78% higher than background levels), which is likely related to the widespread use of coal and biofuel in China.

Keywords: Urban air quality; Halocarbons; Montreal Protocol; Gas chromatography; China


Analyses of platinum group elements in mosses as indicators of road traffic emissions in Austria by Harald G. Zechmeister; Harald Hagendorfer; Daniela Hohenwallner; Andrea Hanus-Illnar; Alarich Riss (pp. 7720-7732).
The concentrations of platinum group elements (PGE; platinum, palladium, rhodium) and 17 other elements in mosses growing at 32 sampling sites along 12 roads in Austria were analysed. The study included passive monitoring of naturally growing mosses with an experimental design using mosses samples exposed in a tunnel experiment. PGEs (Pt, Pd, Rh) were analysed by ICP-MS (ELAN DRC II, Perkin Elmer SCIEX) according to EN ISO 17294-2 Tl.29. Mean concentrations of PGEs in five moss species were: Pt 7.07±9.97, Pd 2.8±5.2 und Rh 0.6±0.8ngg−1 dry weight. This is comparable to data derived from measurements of gasoline autocatalyst emissions or airborne particles (<10μm). Compared to soils and road dust along highways, concentrations in mosses were lower by a factor of ten, compared to grasses they were comparable or somewhat higher. The ratios between the various PGEs were calculated as follows (mean values): Pt/Pd 7.9±10.2, Pt/Rh 12.6±8.3 and Pd/Rh 3.7±2.2. The number of light duty vehicles (<3.5t) and the distance from the road were the main influential factors for PGE concentrations. Especially strong correlations could be found between Pt and Sb, Cu, Zn, and Cd (in decreasing order), which are all elements derived mainly from road traffic emissions. Cluster analysis (Partioning Around Medoids Method) separated elements derived mainly from soil dust (Ca, Al). An analysis of spatial deposition patterns of PGEs showed a reciprocal decrease of concentrations with increasing distance from the road, reaching background values at distances between 10 and 200m, sometimes even more, but outside the spatial range of our investigation.

Keywords: Biomonitoring; Bryophytes; Platinum; Road traffic emissions; Spatial distribution patterns


Assessment of natural components of PM10 at UK urban and rural sites by Alan M. Jones; Roy M. Harrison (pp. 7733-7741).
Proposals from the European Commission have raised the possibility that Member States may be able to subtract the concentrations of natural components of airborne particulate matter from measured concentrations when evaluating compliance with EU Limit Values. By applying the pragmatic mass closure model [. A pragmatic mass closure model for airborne particulate matter at urban background and roadside sites. Atmospheric Environment 37, 4927–4933] to chemical composition data for PM10, it has been possible to estimate the concentrations of natural sea salt, strongly bound water and secondary organic carbon (which is assumed wholly biogenic) to the measured mass of PM10. Because of the difficulty in distinguishing between natural and anthropogenic crustal dusts, the contribution of natural windblown dust and soil has not been accounted for. When the natural components are estimated for two urban and one rural site in the UK, the long-term mean PM10 concentration is reduced by between 5.2 and 7.3μgm−3. The number of exceedences of the 50μgm−3 24-h limit value falls dramatically from 54 to 21 (from a total of 291 days) at an urban street canyon site, 7 to 3 (n=292 days) at an urban background site and from 8 to 0 (n=241 days) at a rural site when using gravimetric PM10 concentrations. The calculations have also been performed using PM10 concentrations measured by TEOM increased by a factor of 1.3 as recommended by the European Commission as an interim means of estimating gravimetric equivalency, and the number of exceedences of the 24-h limit value fell from 92 to 47 (from a total of 291 days) at the urban street canyon site, from 11 to 3 (n=292 days) at the urban background site and from 6 to 3 (n=241) at the rural site. Clearly, therefore, application of this proposed measure would make a very major difference to the likelihood of compliance or otherwise with the 24-h limit value for PM10.

Keywords: PM; 10; Natural components; Limit value; Mass closure


Isomer distribution of nitrotriphenylenes in airborne particles, diesel exhaust particles, and the products of gas-phase radical-initiated nitration of triphenylene by Takayuki Kameda; Koji Inazu; Yoshiharu Hisamatsu; Norimichi Takenaka; Hiroshi Bandow (pp. 7742-7751).
The formation of mutagenic nitro-polycyclic aromatic hydrocarbons (NPAHs) 1- and 2-nitrotriphenylene (1- and 2-NTP) via gas-phase OH or NO3 radical-initiated reactions of triphenylene was demonstrated for the first time using a flow reaction system. In contrast with the results of conventional electrophilic nitration, 2-NTP was formed in larger yield than 1-NTP, but this is consistent with the mechanism proposed for gas-phase radical-initiated nitration of PAH. In diesel exhaust particle (DEP) samples, both 1- and 2-NTP were identified and their concentrations determined, as well as 1-nitropyrene (1-NP), which is a representative combustion-derived NPAH: the mean concentrations of 1-NTP, 2-NTP, and 1-NP were 4.7, 1.9, and 32pmolmgDEP–1, respectively. The mean 2-NTP/1-NTP, 1-NTP/1-NP, and 2-NTP/1-NP ratios in samples of airborne particles collected in a residential area in Osaka, Japan, were>1.55,<0.25, and 0.37, respectively; these values are much higher than those of the DEP samples. This finding indicates that there is another source for airborne NTPs, especially 2-NTP, apart from diesel exhaust. These results strongly suggest that airborne NTPs originate from atmospheric processes such as radical-initiated reactions of triphenylene, and this has a significant influence on the atmospheric occurrence of NTPs.

Keywords: Nitroarene; PAH; OH radical; NO; 3; radical; Diesel exhaust particles; Airborne particles


Daily, weekly, and seasonal time courses of VOC concentrations in a semi-urban area near Barcelona by I. Filella; Penuelas J. Peñuelas (pp. 7752-7769).
In order to study the daily, weekly, and seasonal patterns and possible origins of air concentrations of volatile organic compounds (VOCs), measurements were taken on a minute-by-minute basis with a PTR-MS in the vicinity of a highway in a semi-urban site near Barcelona. Four periods of the year were chosen and samples were taken under different meteorological conditions and at different phenological stages of the surrounding vegetation. None of the measured VOCs concentrations exceeded air-quality guidelines. The results showed that diurnal, weekly, and seasonal fluctuations in measured VOC concentrations depended on variations in the strength of sources, as well as on photochemical activity and meteorological conditions. There was a decrease in concentrations in most VOCs when mixing depth, photochemical destruction, and wind speed increased at midday. On the other hand, high values of some VOCs occurred at night when the strength of their sinks and the mixing layer decreased. Interestingly, in June, night emissions and concentration peaks of methanol and acetone occurred in periods with dew formation and no wind. VOCs related to anthropogenic emissions presented a weekly pattern of variation with a clear distinction being found between working days and the weekend. The seasonal variation showed higher levels in December for all VOCs, except for isoprene. The thinning of the mixing layer leading to greater concentrations of volatiles and lower wind speeds in winter could account for those higher VOC levels. Benzene and toluene originated mainly from anthropogenic emissions. The sources of acetaldehyde, methanol, and acetone appeared to be mainly biogenic and these compounds were the most abundant of all the measured VOCs. Isoprene concentration patterns suggest a predominantly anthropogenic origin in December and March and a mainly biogenic origin in June and October. All these data provide useful information on the dynamics of VOCs in an area where ozone levels in summer exceed quite often the standard protection thresholds for O3.

Keywords: Traffic; Mediterranean region; Biogenic VOCs; Anthropogenic VOCs; Semi-urban area


Testing kernel density reconstruction for Lagrangian photochemical modelling by Fabio Monforti; Lina Vitali; Gianni Pagnini; Rita Lorenzini; Luca Delle Monache; Gabriele Zanini (pp. 7770-7785).
In recent years, a number of pioneering works have shown as Lagrangian models can be of great interest when dealing with photochemistry, provided that special care is given in the reconstruction of chemicals concentration in the atmosphere. Density reconstruction can be performed through the so-called “box counting� method: an Eulerian grid for chemistry is introduced and density is computed counting particles in each box. In this way one of the main advantages of the Lagrangian approach, the grid independence, is lost. In this paper, a new approach to Lagrangian photochemical modelling is investigated and the chemical module of the Photochemical Lagrangian Particle Model (PLPM) is described and fully tested for stability, reliability and computational weight. Photochemical reactions are treated in PLPM by means of the complex chemical mechanism SAPRC90 and four density reconstruction methods have been developed, based on the kernel density estimator approach, in order to obtain grid-free accurate concentrations.

Keywords: Photochemical pollution; Lagrangian chemical transport model; Grid-free model; Complex chemical mechanism; Kernel density estimator


Nitric oxide and nitrous oxide emission from Hungarian forest soils; linked with atmospheric N-deposition by L. Horvath László Horváth; E. Fuhrer Ernő Führer; Kate Lajtha (pp. 7786-7795).
Studies of forest nitrogen (N) budgets generally measure inputs from the atmosphere in wet and dry deposition and outputs via hydrologic export. Although denitrification has been shown to be important in many wetland ecosystems, emission of N oxides from forest soils is an important, and often overlooked, component of an ecosystem N budget. During 1 year (2002–03), emissions of nitric oxide (NO) and nitrous oxide (N2O) were measured from Sessile oak and Norway spruce forest soils in northeast Hungary. Accumulation in small static chambers followed by gas chromatography-mass spectrometry detection was used for the estimation of N2O emission flux. Because there are rapid chemical reactions of NO and ozone, small dynamic chambers were used for in situ NO flux measurements. Average soil emissions of NO were 1.2 and 2.1μgNm−2h−1, and for N2O were 15 and 20μgNm−2h−1, for spruce and oak soils, respectively. Due to the relatively high soil water content, and low C/N ratio in soil, denitrification processes dominate, resulting in an order of magnitude greater N2O emission rate compared to NO. The previously determined N balance between the atmosphere and the forest ecosystem was re-calculated using these soil emission figures. The total (dry+wet) atmospheric N-deposition to the soil was 1.42 and 1.59gNm−2yr−1 for spruce and oak, respectively, while the soil emissions are 0.14 and 0.20gNm−2yr−1. Thus, about 10–13% of N compounds deposited to the soil, mostly asNH3/NH4+ andHNO3/NO3-, were transformed in the soil and emitted back to the atmosphere, mostly as greenhouse gas (N2O).

Keywords: Forest soil emission; Nitric oxide; Nitrous oxide; N saturation; Denitrification; Atmospheric deposition


Chemical compositions and radiative properties of dust and anthropogenic air masses study in Taipei Basin, Taiwan, during spring of 2004 by S.-Y. Shih-Yu Chang; G.-C. Guor-Cheng Fang; Charles C.-K. Chou; W.-N Wei-Nai Chen (pp. 7796-7809).
Asia is one of the major sources of not only mineral dust but also anthropogenic aerosols. Continental air masses associated with the East Asian winter monsoon always contain high contents of mineral dust and anthropogenic species and transported southeastward to Taiwan, which have significant influences on global atmospheric radiation transfer directly by scattering and absorbing solar radiation in each spring. However, few measurements for the long-range transported aerosol and its optical properties were announced in this area, between the Western Pacific and the southeastern coast of Mainland China. The overall objective of this work is to quantify the optical characteristics of different aerosol types in the Eastern Asian. In order to achieve this objective, meteorological parameters, concentrations of PM10 and its soluble species, and optical property of atmospheric scattering coefficients were measured continuously with 1h time-resolved from 11 February to 7 April 2004 in Taipei Basin (25°00′N, 121°32′E). In this work, the dramatic changes of meteorological parameters such as temperature and winds were used to determine the influenced period of each air mass. Continental, strong continental, marine, and stagnant air masses defined by the back-trajectory analysis and local meteorology were further characterized as long-range transport pollution, dust, clean marine, and local pollution aerosols, respectively, according to the diagnostic ratios. The aerosol mass scattering efficiency of continental pollution, dust, clean marine, and local pollution aerosols were ranged from 1.3 to 1.6, 0.7 to 1.0, 1.4 and 1.4 to 2.3m2g−1, respectively. Overall, there are two distinct populations of aerosol mass scattering efficiencies, one for an aerosol chemical composition dominated by dust (<1.0m2g−1) and the other for an aerosol chemical composition dominated by anthropogenic pollutants (1.3–2.3m2g−1), which were similar to the previous measurements with high degree of temporal resolution.

Keywords: Chemical composition; Mass scattering efficiency; Asian dust; Local pollution; Long-range transport


Concentration, size distribution, and dry deposition rate of particle-associated metals in the Los Angeles region by J.-H. Jeong-Hee Lim; Lisa D. Sabin; Kenneth C. Schiff; Keith D. Stolzenbach (pp. 7810-7823).
Daily averaged atmospheric concentrations and dry deposition fluxes of particulate metals were measured seasonally at six urban sites and one non-urban coastal site in the Los Angeles region using a conventional total suspended particulate matter (TSP) filter, surrogate surface deposition plates, and a Noll Rotary Impactor (NRI), which provides information about particle size distribution in four size ranges above 6μm. With the exception of the non-urban site, particulate metal concentrations and deposition fluxes were remarkably uniform spatially and temporally. At all sites there were significant metal concentrations on particles greater than 10μm, a commonly used upper limit for many air quality monitoring studies, and these large particles were estimated to be responsible for most of the deposited mass of metals. Annual averaged values of deposition rates measured with a surrogate surface were in good agreement with values estimated using theoretical deposition velocities in conjunction with measured size-segregated particle concentrations. Image analysis of particles deposited on NRI stage A, which collects all particles greater than 6μm, indicated nighttime metal concentrations and deposition at the non-urban coastal site was higher than in the day time due to offshore advection of urban air associated with the diurnal land breeze. Measured enrichments of crustal elements and metals were correlated, indicating efficient mixing of natural and anthropogenic material from different sources, hypothesized to be the result of cyclical resuspension and deposition of dust by moving vehicles and wind.

Keywords: NRI; Dry deposition velocity; Resuspension; Image analysis; Enrichment factor


In situ monitoring of urban air in Córdoba, Argentina using the Tradescantia-micronucleus (Trad-MCN) bioassay by H.A. Carreras; M.L. Pignata; P.H.N. Saldiva (pp. 7824-7830).
During the last decades, a significant deterioration of ambient air quality has been observed in Argentina. However, the availability of air pollution monitoring stations is still limited to only few cities. In this study, we investigated the genotoxicity of ambient levels of air pollution in Córdoba using the Tradescantia micronucleus assay. The experiment was performed from October, 2004 to April 2005. Pots with Tradescantia pallida were placed in three sites: Córdoba city center, characterized by important avenues with high traffic activity (cars, taxis, and public transport vehicles); the university campus, along a side road with heavy traffic of gasoline and diesel powered vehicles, buses and trucks; and a residential area, with no significant local sources of air pollution. Twenty young T. pallida inflorescences were collected from each sampling site in November, February and April. Micronuclei frequencies were determined in early tetrads of pollen mother cells and expressed as MCN/100 tetrads. Simultaneously, the environmental levels of total suspended particles (24h mean) were determined for each site. A significant difference in micronuclei frequency was observed among sites ( p=0.036). Post-hoc analysis revealed that the residential area exhibited a lower micronuclei frequency than the university and city center areas. In conclusion, we found that the gradients of ambient air pollution of Córdoba are associated with changes in the spontaneous micronuclei frequency of Tradescantia pollen mother cells. These results indicate that in situ biomonitoring with higher plants may be useful for characterizing air pollution in areas without instrumental monitoring techniques, or for exploring the distribution of air contaminants at a microscale.

Keywords: Bioassay; Particulate matter; In situ; biomonitoring; Clastogenicity; Argentina


Particle emissions of a railway line determined by detailed single particle analysis by R. Lorenzo; R. Kaegi; R. Gehrig; Grobety B. Grobéty (pp. 7831-7841).
The goal of this study was to identify and quantify particles emitted from railway traffic. For that purpose PM10 samples were collected near a busy railway line using a wind direction and speed controlled sampling equipment consisting of five devices. Measurements taken perpendicular to the railway lines at 10, 36 and 120m distance enable an identification and separation of particles caused by the railway traffic from background particles. Morphology and chemistry of more than 11,000 particles were analysed by computer controlled scanning electron microscopy (CCSEM). Based on chemical composition five particle classes are defined and assigned to their sources. The mass of the individual particles is determined by multiplying their volumes, calculated based on their morphology with a density assigned specifically to each particle class. The density of the particle classes is derived from their chemical composition. To estimate the PM10 contributions of the railway lines, the mass of PM10 at 120m (background, not influenced by the railway lines) is subtracted from the mass of PM10 at 10m. The emissions of the railway lines are dominated by ‘iron’ particles, which contribute 2.9μgm−3 or 67% to the railway related PM10. In addition, ‘aluminium’ and ‘calcium’ particles contribute also to the railway related PM10 (1.0μgm−3 or 23% for the ‘aluminium’ and 0.4μgm−3 or 10% for the ‘calcium’ particles). These particles are assigned to abrasion of the gravel bed and re-suspension of mineral dust.Long-term gravimetric results of the contribution of iron to the mass of railway related PM10 from a study performed earlier at the same site are in good agreement with the data presented in this study.

Keywords: SEM/EDX; Particle analysis; Morphology; Railway; PM10


Concentration field and turbulent fluxes during the mixing of two buoyant plumes by Daniele Contini; Paul Hayden; Alan Robins (pp. 7842-7857).
In this work an experimental study of mixing of two identical plumes, carried out in a turbulent neutral boundary layer generated in a wind tunnel, is presented. Measurements have been performed with fast flame ionisation detectors (FFIDs) and a two-component Laser-Doppler Anemometer system. Results allow the study of both the average and the fluctuating concentration field, including the turbulent vertical and longitudinal mass fluxes, in single plumes and during the interaction of two identical plumes. This information gives insight into the details of the mixing phase of the two plumes. Results of trajectories and additional rise (due to plume interactions) have been compared with previous measurements carried out in laminar cross-flows, showing similar behaviour. Concentration distributions in plume cross-sections in turbulent cross-flows differ from those measured in laminar cross-flows. Average vertical and longitudinal velocity measurements into the plume core show the strength of the shielding effect of the upwind plume and some details of interaction between the counter-rotating vortex pairs (CVPs). For large values of the alignment angle φ, between the line joining the stacks and the cross-flow, an average negative vertical velocity is measured in the middle of the plume even if its centre of mass is rising. This downward velocity is induced by the slow interaction of the CVPs and generates a vertical stretching of the plume and negative rise enhancement. Vertical turbulent fluxes change sign on the plume centreline and are of opposite sign with respect to the longitudinal turbulent fluxes. Results indicate a good linearity between vertical turbulent fluxes and concentration gradients, with different proportionality for the top and bottom parts of the plume (especially in the near field) indicating that dispersion could be described by a gradient-transfer model.

Keywords: Plume interaction; Wind tunnel; Fast FID; Turbulent fluxes; LDA


Chemical composition of fine particles from incense burning in a large environmental chamber by B. Wang; S.C. Lee; K.F. Ho (pp. 7858-7868).
This study is aimed to characterize the major chemical compositions of PM2.5 from incense burning in a large environmental chamber. Chemical analyses, including X-ray fluorescence for elemental species, ion chromatography for water soluble inorganic species (chloride, nitrate, sulfate, sodium, potassium, ammonium) and thermal/optical reflectance analysis for carbon species were carried out for combustion of three incense categories (traditional, aromatic and church incense). The average concentrations from incense burning ranged from 139.8 to 4414.7μgm−3 for organic carbon (OC), and from 22.8 to 74.0μgm−3 for elemental carbon (EC), respectively. The average OC and EC concentrations in PM2.5 of three incense categories were in the order of church incense>traditional incense>aromatic incense. OC/EC ratios ranged from 7.0 to 39.1 for the traditional incense, with an average of 21.7; from 3.2 to 11.9 for the aromatic incense, with an average of 7.7. The concentrations of Cl−, SO42−, Na+ and K+ were highly variable. On average, the inorganic ion concentration sequence was traditional incense>church incense>aromatic incense. The profiles for elements were dominated by Na, Cl and K. In general, the major components in PM2.5 fraction from incense burning are OC (especially OC2, OC3 and OC4), EC and K.

Keywords: PM; 2.5; Chamber; Incense; Chemical composition; Carbon fractions


Measurement of total OH reactivity by laser-induced pump and probe technique—comprehensive observations in the urban atmosphere of Tokyo by Ayako Yoshino; Yasuhiro Sadanaga; Keisuke Watanabe; Shungo Kato; Yuko Miyakawa; Jun Matsumoto; Yoshizumi Kajii (pp. 7869-7881).
Total OH reactivity was observed by use of the laser-induced pump and probe technique, and the urban air quality in Tokyo was diagnosed comprehensively. The concentrations of NO x, CO, O3, non-methane hydrocarbons (NMHCs) and oxygenated volatile organic compounds (OVOCs) were observed simultaneously. The observations were conducted in July and August 2003, and in January, February, May, and November 2004. Generally, the observed OH reactivity was higher than the calculated values derived using the observed concentrations of the trace species. The differences between the observed and calculated values in summer, spring, and autumn were approximately 30%. However, the difference in winter was smaller than those in the other seasons. In addition, while the differences observed in summer, spring, and autumn correlated with the total reactivity of the OVOCs (Σi kOVOC i[OVOC i](s−1),k i is rate constant of its compounds with OH), the correlations were not confirmed in the case of winter because atmospheric oxidation was less active and OVOCs levels were low in winter. These results suggest that the secondary products of the photochemical reactions in the atmosphere would be a missing sink for the OH loss process in the urban area.

Keywords: Total OH reactivity; Laser-induced pump and probe technique; Urban air quality


Formation and growth of indoor air aerosol particles as a result ofd-limonene oxidation by E. Vartiainen; M. Kulmala; T.M. Ruuskanen; R. Taipale; J. Rinne; H. Vehkamäki (pp. 7882-7892).
Oxidation ofd-limonene, which is a common monoterpene, can lead to new aerosol particle formation in indoor environments. Thus, products containingd-limonene, such as citrus fruits, air refresheners, household cleaning agents, and waxes, can act as indoor air aerosol particle sources. We releasedd-limonene into the room air by peeling oranges and measured the concentration of aerosol particles of three different size ranges. In addition, we measured the concentration ofd-limonene, the oxidant, and the concentration of ozone, the oxidizing gas. Based on the measurements we calculated the growth rate of the small aerosol particles, which were 3–10nm in diameter, to be about6300nmh-1, and the losses of the aerosol particles that were due to the coagulation and condensation processes. From these, we further approximated the concentration of the condensable vapour and its source rate and then calculated the formation rate of the small aerosol particles. For the final result, we calculated the nucleation rate and the maximum number of molecules in a critical cluster. The nucleation rate was in the order of105cm-3s-1 and the number of molecules in a critical-sized cluster became 1.2. The results were in agreement with the activation theory.

Keywords: Nucleation; Particle growth; Activation; Monoterpene oxidation; Indoor air particle sources


Assessment of 2010 air quality in two Alpine valleys from modelling: Weather type and emission scenarios by G. Brulfert; C. Chemel; E. Chaxel; J.-P. Chollet; B. Jouve; H. Villard (pp. 7893-7907).
Alpine valleys are sensitive to anthropogenic emissions. Local atmospheric dynamics are a key factor that may lead to an accumulation of pollutants in the bottom of the Chamonix and Maurienne valleys. Assessment of 2010 pollutant concentrations variability needs to take these specificities into account. A meteorological data classification is combined with different emission scenarios in order to run an air quality model. Using simulations of representative scenarios rather than complete years allows for a fine spatial and temporal representation of local atmospheric dynamics and gives access to detailed chemical breakdowns. Results demonstrate the variability of primary and secondary species due to emissions and the predominance of local effects on pollutant concentrations.

Keywords: Air quality modelling; Air pollution; Alpine valleys; Emission scenarios; Meteorological classification


Two-stage chemical fractionation method for the analysis of elements and non-volatile inorganic ions in PM10 samples: Application to ambient samples collected in Rome (Italy) by Silvia Canepari; Enrico Cardarelli; Cinzia Perrino; Maria Catrambone; Adriana Pietrodangelo; Marco Strincone (pp. 7908-7923).
A two-stage micro-analytical scheme for the determination of metals and ions in atmospheric particulate matter collected on only one Teflon filter was developed. In the first stage the collected particles are chemically fractionated for their solubility in a pH-buffered extracting solution; in the second stage the residue is mineralised. The major non-volatile inorganic ions (Cl−, NO3−, SO42−, Na+, NH4+, Ca2+, Mg2+) are determined in the first fraction by ion-chromatography (IC), while metals and metalloids (Al, As, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Pb, S, Sb, Se, Si, Ti, V, Zn) are determined in both the acetate extractable and the mineralised residual fractions by inductively coupled plasma optical emission spectroscopy (ICP-OES).The procedure was applied to ambient 24-h PM10 samples collected on Teflon filters during two field campaigns carried out at two sites in the area of Rome (Italy). The variations in the chemical composition of the collected particles during the two periods were interpreted in the light of the dilution properties of the lower atmosphere and of the back-trajectories of the air masses. The difference in the results between the two locations was interpreted in the light of their proximity to the emission sources. It was found that the acetate extractable and the mineralised residual fraction of some metals exhibit a different temporal pattern, suggesting the existence of different emission sources of the two fractions.

Keywords: Urban pollution; Particulate matter; Non-volatile water-soluble ions; Element solubility; Source apportionment


Development and calibration of real-time PCR for quantification of airborne microorganisms in air samples by Hey Reoun An; Gediminas Mainelis; Lori White (pp. 7924-7939).
This manuscript describes the coupling of bioaerosol collection and the use of real-time PCR (RT-PCR) to quantify the airborne bacteria. The quantity of collected bacteria determined by RT-PCR is compared with conventional quantification techniques, such as culturing, microscopy and airborne microorganism counting by using optical particle counter (OPC). Our data show that an experimental approach used to develop standard curves for use with RT-PCR is critical for accurate sample quantification. Using universal primers we generated 12 different standard curves which were used to quantify model organism Escherichia coli (Migula) Catellani from air samples. Standard curves prepared using a traditional approach, where serially diluted genomic DNA extracted from pure cultured bacteria were used in PCR reaction as a template DNA yielded significant underestimation of sample quantities compared to airborne microorganism concentration as measured by an OPC. The underestimation was especially pronounced when standard curves were built using colony forming units (CFUs). In contrast, the estimate of cell concentration in an air sample by RT-PCR was more accurate (∼60% compared to the airborne microorganism concentration) when the standard curve was built using aerosolized E. coli. The accuracy improved even further (∼100%) when air samples used to build the standard curves were diluted first, then the DNA extracted from each dilution was amplified by the RT-PCR—to mimic the handling of air samples with unknown and possibly low concentration. Therefore, our data show that standard curves used for quantification by RT-PCR needs to be prepared using the same environmental matrix and procedures as handling of the environmental sample in question. Reliance on the standard curves generated with cultured bacterial suspension (a traditional approach) may lead to substantial underestimation of microorganism quantities in environmental samples.

Keywords: Bioaerosol quantification; Real-time PCR; Standard curves; Air sampling; Bioaerosols


Measurement and modeling of urban atmospheric PCB concentrations on a small (8km) spatial scale by Lisa A. Totten; Georgiy Stenchikov; Cari L. Gigliotti; Nilesh Lahoti; Steven J. Eisenreich (pp. 7940-7952).
Atmospheric transport and deposition of polychlorinated biphenyls (PCBs) is an important problem for ecosystems around the world. Data from several monitoring networks demonstrate that atmospheric PCB concentrations are dramatically elevated in urban areas compared to rural or background regions, such that these urban emissions of PCBs support the regional and global transport and deposition of PCBs to more remote areas. Identifying and controlling the sources of urban atmospheric PCBs is thus essential in minimizing the regional and global transport and deposition of these compounds. From December 1999 to November 2000, gas-phase PCB concentrations were measured at two monitoring locations, ∼8km apart, within the New York City metropolitan area, at Jersey City and Bayonne, NJ. Concentrations, congener patterns, and temporal patterns of PCBs differ dramatically at the two sites, suggesting that a significant source of atmospheric PCBs exists within 8km of the Bayonne site, resulting in spikes in gas-phase PCB concentration at Bayonne that are not observed at Jersey City. The Regional Atmospheric Model System (RAMS) coupled with the Hybrid Particle and Concentration Transport model (HYPACT) was used to estimate that the PCB source near Bayonne emits a flux of ΣPCBs on the order of 100gd−1. Extrapolation of this source magnitude to the area of New York City suggests that this urban area emits at least 300kgyr−1 ΣPCBs to the regional atmosphere, similar in magnitude to the flow of ΣPCB out of the Upper Hudson River into the New York/New Jersey Harbor.

Keywords: RAMS; HYPACT; Transport modeling; Persistent organic pollutants; New York; New Jersey; Harbor


Sulfate aerosols forcing: An estimate using a three-dimensional interactive chemistry scheme by Sunita Verma; O. Boucher; H.C. Upadhyaya; O.P. Sharma (pp. 7953-7962).
The tropospheric sulfate radiative forcing has been calculated using an interactive chemistry scheme in LMD-GCM. To estimate the radiative forcing of sulfate aerosol on climate, a consistent interaction between atmospheric circulation and radiation computation has been allowed in LMD-GCM. The model results indicate that the change in the sulfate aerosols number concentration is negatively correlated to the indirect radiative forcing. The model simulated annual mean direct radiative forcing ranges from −0.1 to −1.2Wm−2, and indirect forcing ranges from −0.4 to −1.6Wm−2. The global annual mean direct effect estimated by the model is −0.48Wm−2, and that of indirect is −0.68Wm−2.

Keywords: Sulfate aerosols; Radiative forcing; Cloud droplet number concentration; Direct forcing; Indirect forcing


Ozone pollution and ozone biomonitoring in European cities. Part I: Ozone concentrations and cumulative exposure indices at urban and suburban sites by Andreas Klumpp; Wolfgang Ansel; Gabriele Klumpp; Vicent Calatayud; Jean Pierre Garrec; Shang He; Penuelas Josep Peñuelas; A. Àngela Ribas; Ro-Poulsen Helge Ro-Poulsen; Stine Rasmussen; M.J. María José Sanz; Phillippe Vergne (pp. 7963-7974).
In the frame of a European research project on air quality in urban agglomerations, data on ozone concentrations from 23 automated urban and suburban monitoring stations in 11 cities from seven countries were analysed and evaluated. Daily and summer mean and maximum concentrations were computed based on hourly mean values, and cumulative ozone exposure indices ( Accumulated exposure Over a Threshold of 40ppb (AOT40), AOT20) were calculated. The diurnal profiles showed a characteristic pattern in most city centres, with minimum values in the early morning hours, a strong rise during the morning, peak concentrations in the afternoon, and a decline during the night. The widest amplitudes between minimum and maximum values were found in central and southern European cities such as Düsseldorf, Verona, Klagenfurt, Lyon or Barcelona. In the northern European cities of Edinburgh and Copenhagen, by contrast, maximum values were lower and diurnal variation was much smaller. Based on ozone concentrations as well as on cumulative exposure indices, a clear north–south gradient in ozone pollution, with increasing levels from northern and northwestern sites to central and southern European sites, was observed. Only the Spanish cities did not fit this pattern; there, ozone levels were again lower than in central European cities, probably due to the direct influence of strong car traffic emissions. In general, ozone concentrations and cumulative exposure were significantly higher at suburban sites than at urban and traffic-exposed sites. When applying the newly established European Union (EU) Directive on ozone pollution in ambient air, it was demonstrated that the target value for the protection of human health was regularly surpassed at urban as well as suburban sites, particularly in cities in Austria, France, northern Italy and southern Germany. European target values and long-term objectives for the protection of vegetation expressed as AOT40 were also exceeded at many monitoring sites.

Keywords: Air quality; AOT40; Thresholds; EU Directive; Urban air pollution


The impacts of different kinds of dust events on PM10 pollution in northern China by Shigong Wang; Wei Yuan; Kezheng Shang (pp. 7975-7982).
In this study the frequencies of PM10 (as key urban pollutant) in 14 key environmental protection cities in northern China were analyzed. It follows that the PM10 concentration in the high-frequency period is higher with an extent 0.009–0.066mgm−3 than in the low-frequency period of 2001–2002. Further the impacts of three kinds of dust events on the PM10 concentration in four cities (Beijing, Hohhot, Xi’an and Lanzhou) were explored. The results showed that different kinds of dust events have different influences on variation of PM10 concentration in these four cities. In Lanzhou and Hohhot, which are near the source areas of dust events, the contribution degree of these three dust events to the PM10 is: floating dust>dust storm>blowing dust. Whereas, in Beijing and Xi’an situated in dust event passing areas, the mean value of PM10 concentration is higher in blowing dust than in floating dust (no dust storm). In addition, the influences of dust events on PM10 concentration are different in the cities on different dust event paths. In Beijing and Hohhot (on the northern path), the high PM10 concentration is usually caused by blowing dust. But in both Lanzhou and Xi’an (on the western/northwestern path) the high PM10 pollution concentration is usually caused by floating dust.

Keywords: Dust events; Air pollution index; PM; 10; Northern China


Impact of two chemistry mechanisms fully coupled with mesoscale model on the atmospheric pollutants distribution by J. Arteta; S. Cautenet; M. Taghavi; N. Audiffren (pp. 7983-8001).
Air quality models (AQM) consist of many modules (meteorology, emission, chemistry, deposition), and in some conditions such as: vicinity of clouds or aerosols plumes, complex local circulations (mountains, sea breezes), fully coupled models (online method) are necessary. In order to study the impact of lumped chemical mechanisms in AQM simulations, we examine the ability of both different chemical mechanisms: (i) simplified: Condensed Version of the MOdèle de Chimie Atmosphérique 2.2 (CV-MOCA2.2), and (ii) reference: Regional Atmospheric Chemistry Model (RACM), which are coupled online with the Regional Atmospheric Modeling Systems (RAMS) model, on the distribution of pollutants. During the ESCOMPTE experiment (Expérience sur Site pour COntraindre les Modèles de Pollution et de Transport d’Emissions) conducted over Southern France (including urban and industrial zones), Intensive observation periods (IOP) characterized by various meteorological and mixed chemical conditions are simulated. For both configurations of modeling, numerical results are compared with surface measurements (75 stations) for primary (NO x) and secondary (O3) species. We point out the impact of the two different chemical mechanisms on the production of species involved in the oxidizing capacity such as ozone and radicals within urban and industrial areas. We highlight that both chemical mechanisms produce very similar results for the main pollutants (NO x and O3) in three-dimensional (3D) distribution, despite large discrepancies in 0D modeling. For ozone concentration, we found sometimes small differences (5–10ppb) between the mechanisms under study according to the cases (polluted or not). The relative difference between the two mechanisms over the whole domain is only −7% for ozone from CV-MOCA 2.2 versus RACM. When the order of magnitude is needed rather than an accurate estimate, a reduced mechanism is satisfactory. It has the advantage of running faster (four times less than CPU time on SGI 3800 with 30 processors). Simplified mechanisms are really important to study cases for which an online coupling is necessary between meso-scale and chemistry models (clouds or aerosols plumes impacts, highly variable meteorology).

Keywords: Meso-scale modeling; Chemical mechanisms; Air pollution; Online coupled modeling; Gas-phase


Contribution of motor vehicle emissions to organic carbon and fine particle mass in Pittsburgh, Pennsylvania: Effects of varying source profiles and seasonal trends in ambient marker concentrations by R. Subramanian; Neil M. Donahue; Anna Bernardo-Bricker; Wolfgang F. Rogge; Allen L. Robinson (pp. 8002-8019).
We present estimates of the vehicular contribution to ambient organic carbon (OC) and fine particle mass (PM) in Pittsburgh, PA using the chemical mass balance (CMB) model and a large dataset of ambient molecular marker concentrations. Source profiles for CMB analysis are selected using a method of comparing the ambient ratios of marker species with published profiles for gasoline and diesel vehicle emissions. The ambient wintertime data cluster on a hopanes/EC ratio–ratio plot, and therefore can be explained by a large number of different source profile combinations. In contrast, the widely varying summer ambient ratios can be explained by a more limited number of source profile combinations. We present results for a number of different CMB scenarios, all of which perform well on the different statistical tests used to establish the quality of a CMB solution. The results illustrate how CMB estimates depend critically on the marker-to-OC and marker-to-PM ratios of the source profiles. The vehicular contribution in the winter is bounded between 13% and 20% of the ambient OC (274±56–416±72ng-Cm−3). However, variability in the diesel profiles creates uncertainty in the gasoline–diesel split. On an OC basis, one set of scenarios suggests gasoline dominance, while a second set indicates a more even split. On a PM basis, all solutions indicate a diesel-dominated split. The summer CMB solutions do not present a consistent picture given the seasonal shift and wide variation in the ambient hopanes-to-EC ratios relative to the source profiles. If one set of source profiles is applied to the entire dataset, gasoline vehicles dominate vehicular OC in the winter but diesel dominates in the summer. The seasonal pattern in the ambient hopanes-to-EC ratios may be caused by photochemical decay of hopanes in the summer or by seasonal changes in vehicle emission profiles.

Keywords: Chemical mass balance (CMB); Molecular markers; Organic carbon; Motor vehicle contribution; Gasoline–diesel split


Validation of a Lagrangian dispersion model implementing different kernel methods for density reconstruction by Lina Vitali; Fabio Monforti; Roberto Bellasio; Roberto Bianconi; Valentina Sachero; Sonia Mosca; Gabriele Zanini (pp. 8020-8033).
In this paper the inert version of a Lagrangian particle model named photochemical Lagrangian particle model (PLPM) is described and validated. PLPM implements four density reconstruction algorithms based on the kernel density estimator. All these methods are fully grid-free but they differ each other in considering local or global features of the particles distribution, in treating the Cartesian directions separately or together and in being based on receptors or particles positions in space. Each kernel has been shown to have both advantages and disadvantages, but the overall good performances of the model when compared with the well known Copenhagen and Kincaid data sets are very encouraging in view of its extension to fully chemically active simulations, currently under development.

Keywords: Photochemical pollution; Lagrangian chemical transport model; Grid-free model; Complex chemical mechanism; Kernel density estimator


The change of gaseous carbon fluxes following the switch of dominant producers from macrophytes to algae in a shallow subtropical lake of China by Yangping Xing; Ping Xie; Hong Yang; Aiping Wu; Leyi Ni (pp. 8034-8043).
Successions of lake ecosystems from clear-water, macrophyte-rich conditions into turbid states with abundant phytoplankton have taken place in many shallow lakes in China. However, little is know about the change of carbon fluxes in lakes during such processes. We conducted a case study in Lake Biandantang to investigate the change of carbon fluxes during such a regime shift. Dissolved aquatic carbon and gaseous carbon (methane (CH4) and carbon dioxide (CO2)) across air–water interface in three sites with different vegetation covers and compositions were studied and compared. CH4 emissions from three sites were 0.62±0.36, 0.70±0.36, and 1.31±0.57mgm−2h−1, respectively. Correlation analysis showed that macrophytes, rather than phytoplankton, directly positively affected CH4 emission. CO2 fluxes of three sites in Lake Biandantang were significantly different, and the average values were 77.8±20.4, 52.2±14.1 and 3.6±26.8mgm−2h−1, respectively. There were an evident trend that the larger macrophyte biomass, the lower CO2 emissions. Correlation analysis showed that in different sites, dominant plant controlled CO2 flux across air–water interface. In a year cycle, the percents of gaseous carbon release from lake accounting for net primary production were significantly different (from 39.3% to 2.8%), indicating that with the decline of macrophytes and regime shift, the lake will be a larger carbon source to the atmosphere.

Keywords: Methane; Carbon dioxide; Macrophyte; Phytoplankton


Historical alteration in the nitrogen concentration and15N natural abundance of mosses in Germany: Indication for regionally varying changes in atmospheric nitrogen deposition within the last 140 years by A. Solga; T. Eichert; J.-P. Frahm (pp. 8044-8055).
Historical alterations of nitrogen deposition in the western part of Germany were investigated by comparing nitrogen concentrations and15N natural abundance of historical and recent samples of the two pleurocarpous mosses Pleurozium schreberi and Scleropodium purum. Pooling of the data revealed only slight tissue N increases over the past 140 years which were significant nevertheless. At closer examination on the single site level historical increases of N concentrations were found particularly for some sites in regions where agricultural activities were considerably intensified during the second half of the 20th century. The comparison of δ15N values showed a strong depletion of15N natural abundance in areas currently heavily influenced by livestock management. This indicates an increased impact of NH y compounds. However, the almost unchanged δ15N values in some low mountain range areas with only moderate intensification of agriculture point to a more or less constant ratio of NH y/NO x input over time. Significant correlations of both tissue N concentrations and15N natural abundance between the two species justify the assumption that they use the same nitrogen source, probably atmospheric deposition.

Keywords: Pleurozium schreberi; Scleropodium purum; Historical variation; Regional variation; Stable isotope; 15; N; Tissue nitrogen


Integrating lidar and satellite optical depth with ambient monitoring for 3-dimensional particulate characterization by Jill A. Engel-Cox; Raymond M. Hoff; Raymond Rogers; Fred Dimmick; Alan C. Rush; James J. Szykman; Jassim Al-Saadi; D. Allen Chu; Erica R. Zell (pp. 8056-8067).
A combination of in-situ PM2.5, sunphotometers, upward pointing lidar and satellite aerosol optical depth (AOD) instruments have been employed to better understand variability in the correlation between AOD and PM2.5 at the surface. Previous studies have shown good correlation between these measures, especially in the US east, and encouraged the use of satellite data for spatially interpolating between ground sensors. This work shows that cases of weak correlation can be better understood with knowledge of whether the aerosol is confined to the surface planetary boundary layer (PBL) or aloft. Lidar apportionment of the fraction of aerosol optical depth that is within the PBL can be scaled to give better agreement with surface PM2.5 than does the total column amount. The study has shown that lidar combined with surface and remotely sensed data might be strategically used to improve our understanding of long-range or regionally transported pollutants in multiple dimensions.

Keywords: Air quality; Satellite; MODIS; Lidar; Particulate matter; Policy


Shifted power-law relationship between NO2 concentration and the distance from a highway: A new dispersion model based on the wind profile model by Xiaodong Zou; Zhemin Shen; Tao Yuan; Shan Yin; Jingping Cai; Liping Chen; W.H. Wenhua Wang (pp. 8068-8073).
In this paper, a shifted power-law model, based on the wind profile model, had been supposed to simulate concentration gradient of nitrogen dioxide (NO2) with distance from a highway. Field experiments were performed for NO2 gradients from a highway in Shanghai by using passive samplers. The shifted power-law model was fitted well with experimental results of field experiments both in this study and in the literature. The results not only verified the validity of shifted power-law relationship between NO2 concentration and the distance from a highway, but also partially demonstrated that there were some significant similarities between wind profile and air pollutants concentration profile near highway. With known concentration of chosen reference point and appropriate value of the parameter k, the model could be practically applied for predicting the NO2 distributions near a highway. The methods of determining the parameter k were also discussed for further detailed studies.

Keywords: Nitrogen dioxide; Model; Traffic; Highway; Passive monitoring; Wind profile


Temporal variability of airborne bacterial community structure in an urban area by Pierre A. Maron; Christophe Mougel; David P. H. Lejon; Esmeralda Carvalho; Karine Bizet; G. Géraldine Marck; N. Nadège Cubito; Philippe Lemanceau; Lionel Ranjard (pp. 8074-8080).
Temporal airborne bacterial genetic community structure and meteorological factors were analysed above an urban area in the northwest of France from December 2003 to April 2004 with a sampling strategy considering different time intervals (from an hour to a month). Principal component analysis (PCA) of B-ARISA (Bacterial-Automated Ribosomal Intergenic Spacer Analysis) profiles revealed a hierarchy in the temporal variability of bacterial community: daily

Keywords: Bacterial community; Air; Diversity; Temporal variability


Ground level ozone concentrations and its association with NO x and meteorological parameters in Kathmandu valley, Nepal by Deepak Pudasainee; Balkrishna Sapkota; Manohar Lal Shrestha; Akikazu Kaga; Akira Kondo; Yoshio Inoue (pp. 8081-8087).
This paper summarizes the results of a yearlong continuous measurements of gaseous pollutants, NO, NO2, NO x and O3 in the ambient air at Kathmandu valley. Measured concentration of the pollutants in study area is a function of time. NO, NO2 and O3 peak occurred in succession in presence of sunlight. At the time of maximum O3 concentration most of the NO x are utilized. The diurnal cycle of ground level ozone concentrations, revealed mid-day peak with lower nocturnal concentrations and inverse relationship exists between O3 and NO x, which are evidences of photochemical O3 formation. The observed ground level ozone during monsoon is slight lower than the pre-monsoon value. Further, lack of rainfall and higher temperature, solar radiation in the pre-monsoon have given rise to the gradual build up of ozone and it is lowest during winter. Ground level ozone concentrations measured during bandha (general strike) and weekend are 19% and 13% higher than those measured during weekdays. The most effective ozone abatement strategy for Kathmandu Valley may be control of NO x emissions.

Keywords: Photochemical ozone; Ozone precursors; Weekend effect; Seasonal variation; Inversion layer


An on-line instrument for mobile measurements of the spatial variability of hexavalent and trivalent chromium in urban air by Andrey Khlystov; Yilin Ma (pp. 8088-8093).
The Steam-Jet Aerosol Collector-long Pathlength Absorbance Spectroscopy (SJAC-LPAS), an on-line continuous instrument for mobile measurements of spatial distribution of water-soluble hexavalent and trivalent chromium in ambient aerosols, has been developed and is presented here. The system collects particles with the SJAC and analyzes the collected sample on-line using the diphenycarbazide (DPC) colorimetric method. By using a Teflon AF (Amorphous Fluoropolymer) liquid core wave guide, the limit of detection has been significantly improved, allowing on-line measurements at ambient concentrations. The limit of detection for Cr(VI) is 0.2ngm−3. Water-soluble Cr(III) can also be measured by oxidizing it to Cr(VI) in a parallel line using hydrogen peroxide before the detection with the DPC method. The concentration of Cr(III) is then determined as the difference between the two lines (Cr(VI) and Cr(VI) plus Cr(III)). The instrument was specifically designed to be used on a mobile platform to study spatial distribution of the pollutant within a city on a scale of 100m. Special attention was given to the time resolution and the stability of the instrument performance under driving conditions. The time resolution of the instrument is 15s. At a typical driving speed of 30kmh−1 the instrument can detect variations in chromium concentration (“hot spots�) on the scale of about 150m. The instrument has proven to operate reliably and capture temporal and spatial variability of Cr(VI) concentration during four mobile measurement campaigns in Wilmington, DE.

Keywords: Hexavalent chromium; Trivalent chromium; Mobile measurements; Spatial distribution
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