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Atmospheric Environment (v.45, #30)

Editorial board (pp. i).

Impact of the installation scenario of porous fences on wind-blown particle emission in open coal yards by X.C. Cong; S.Q. Cao; Z.L. Chen; S.T. Peng; S.L. Yang (pp. 5247-5253).

As a common solution, porous fences are used to reduce the fugitive particulate emission from store piles aggregated in the open storage yards of harbor areas. The dust dispersion has caused heavy ecological pollution and economic losses. In this paper, taking the open coal yard in Caofeidian Port as an example, CFD technology was employed and the flow characteristics over the surfaces of stockpiles were simulated using the k − ɛ RNG turbulence closure model. To validate the boundary conditions defined in the simulation, a field measurement campaign was carried out and the experimental results verified the predicted ones. A more detailed formulation for dust emission compared to the EPA mode was developed afterward to evaluate dust emissions by the CFD approach. The results confirmed the role of porous fences in reducing the dust emissions by comparing the average emission coefficients of four possible installation scenarios proposed from the local wind flow characteristics. It was found that, for variable wind conditions tested during a whole year, dust emissions reduction was approximately 85% in all enclosure along the yard, and the value was 55% and 65% respectively when installing two-side and three-side protection scenarios against the windward of dominant wind direction. This study may suggest some meaningful implications to understand the shelter effect differences among the installation scenarios of porous fences from the technical view.► CFD can predict particle diffusion. ► Porous fences can limit aeolian erosion. ► Fence shelter is evaluated.

Keywords: Porous fence; Numerical simulation; Diffuse dust emissions; Industrial site

Clear link between drought stress, photosynthesis and biogenic volatile organic compounds in Fagus sylvatica L. by M. Šimpraga; H. Verbeeck; M. Demarcke; É. Joó; O. Pokorska; C. Amelynck; N. Schoon; J. Dewulf; H. Van Langenhove; B. Heinesch; M. Aubinet; Q. Laffineur; J.-F. Müller; K. Steppe (pp. 5254-5259).

Direct plant stress sensing is the key for a quantitative understanding of drought stress effects on biogenic volatile organic compound (BVOC) emissions. A given level of drought stress might have a fundamentally different effect on the BVOC emissions of different plants. For the first time, we continuously quantified the level of drought stress in a young potted beech ( Fagus sylvatica L.) with a linear variable displacement transducer (LVDT) installed at stem level in combination with simultaneous measurements of BVOC emissions and photosynthesis rates at leaf level. This continuous set of measurements allowed us to examine how beech alters its pattern of photosynthesis and carbon allocation to BVOC emissions (mainly monoterpenes, MTs) and radial stem growth during the development of drought stress. We observed an increasing-decreasing trend in the MT emissions as well as in the fraction of assimilated carbon re-emitted back into the atmosphere (ranging between 0.14 and 0.01%). We were able to link these dynamics to pronounced changes in radial stem growth, which served as a direct plant stress indicator. Interestingly, we detected a sudden burst in emission of a non-identified, non-MT BVOC species when drought stress was acute (i.e. pronounced negative stem growth). This burst might have been caused by a certain stress-related green leaf volatile, which disappeared immediately upon re-watering and thus the alleviation of drought stress. These results highlight that direct plant stress sensing creates opportunities to understand the overall complexity of stress-related BVOC emissions.Display Omitted► Direct plant stress sensing is key for understanding of drought stress on BVOC. ► Linear variable displacement transducers are suitable for plant stress detection. ► An increasing-decreasing trend in monoterpenes was observed during drought stress. ► During acute drought stress other than monoterpene species contributed to m/ z 81.

Keywords: Radial stem growth; Biogenic volatile organic compounds; Photosynthesis; Drought stress; European beech

Wet deposition of major ions in a rural area impacted by biomass burning emissions by Cidelmara H. Coelho; Andrew G. Allen; Adalgiza Fornaro; Eduardo A. Orlando; Tahuana L.B. Grigoletto; M. Lucia A.M. Campos (pp. 5260-5265).

This work concerns the influence of industrialized agriculture in the tropics on precipitation chemistry. A total of 264 rain events were sampled using a wet-only collector in central São Paulo State, Brazil, between January 2003 and July 2007. Electroneutrality balance calculations (considering H⁺, K⁺, Na⁺,NH4+, Ca²⁺, Mg²⁺, Cl⁻,NO3−,SO42−, F⁻,PO43−, H₃CCOO⁻, HCOO⁻,C2O42− andHCO3−) showed that there was an excess of cations (∼15%), which was attributed to the presence of unmeasured organic anion species originating from biomass burning and biogenic emissions. On average, the three ionsNH4+, NO₃⁻ and H⁺ were responsible for >55% of the total ion concentrations in the rainwater samples. Concentrations (except of H⁺) were significantly higher ( t-test; P = 0.05), by between two to six-fold depending on species, during the winter sugar cane harvest period, due to the practice of pre-harvest burning of the crop. Principal component analysis showed that three components could explain 88% of the variance for measurements made throughout the year: PC1 (52%, biomass burning and soil dust resuspension); PC2 (26%, secondary aerosols); PC3 (10%, road transport emissions). Differences between harvest and non-harvest periods appeared to be mainly due to an increased relative importance of road transport/industrial emissions during the summer (non-harvest) period.The volume-weighted mean (VWM) concentrations of ammonium (23.4 μmol L⁻¹) and nitrate (17.5 μmol L⁻¹) in rainwater samples collected during the harvest period were similar to those found in rainwater from São Paulo city, which emphasizes the importance of including rural agro-industrial emissions in regional-scale atmospheric chemistry and transport models. Since there was evidence of a biomass burning source throughout the year, it appears that rainwater composition will continue to be affected by vegetation fires, even after sugar cane burning is phased out as envisaged by recent São Paulo State legislation.► Biomass burning (BB) strongly affects rainwater ionic composition in our study site (agro-industrial). ► Our rainwater chemistry was similar in several ways to that of São Paulo city. ► The ionic balance showed a 15% anion deficit which was attributed to emissions due to BB. ► Emissions from agro-industrial areas must be accounted for when building transport models in a regional-scale.

Keywords: Rainwater; Sugar cane; Biofuels; São Paulo State; Brazil

Enhanced concentrations of citric acid in spring aerosols collected at the Gosan background site in East Asia by Jinsang Jung; Kimitaka Kawamura (pp. 5266-5272).

In order to investigate water-soluble dicarboxylic acids and related compounds in the aerosol samples under the Asian continent outflow, total suspended particle (TSP) samples ( n = 32) were collected at the Gosan site in Jeju Island over 2–5 days integration during 23 March–1 June 2007 and 16–24 April 2008. The samples were analyzed for water-soluble dicarboxylic acids, ketocarboxylic acids, and α-dicarbonyls using a capillary gas chromatography technique. We found elevated concentrations of atmospheric citric acid (range: 20–320 ng m⁻³) in the TSP samples during mid- to late April of 2007 and 2008. To specify the sources of citric acid, dicarboxylic acids and related compounds were measured in the pollen sample collected at the Gosan site (Pollen_Gosan), authentic pollen samples from Japanese cedar ( Cryptomeria) (Pollen_cedar) and Japanese cypress ( Chamaecyparis obtusa) (Pollen_cypress), and tangerine fruit produced from Jeju Island. Citric acid (2790 ng in unit mg of pollen mass) was found as most abundant species in the Pollen_Gosan, followed by oxalic acid (2390 ng mg⁻¹). Although citric acid was not detected in the Pollen_cedar and Pollen_cypress as major species, it was found as a dominant species in the tangerine juice while malic acid was detected as major species in the tangerine peel, followed by oxalic and citric acids. Since Japanese cedar trees are planted around tangerine farms to prevent strong winds from the Pacific Ocean, citric acid that may be directly emitted from tangerine is likely adsorbed on pollens emitted from Japanese cedar and then transported to the Gosan site. Much lower malic/citric acid ratios obtained under cloudy condition than clear condition suggest that malic acid may rapidly decompose to lower molecular weight compounds such as oxalic and malonic acids (

Keywords: Pollen; Bioaerosol; Citric acid; Malic acid; Dicarboxylic acid; East Asian aerosols

Emissions of particulate-bound elements from stationary diesel engine: Characterization and risk assessment by Raghu Betha; Rajasekhar Balasubramanian (pp. 5273-5281).

There has been an increasing concern about the emissions of airborne particulate matter (PM) from diesel engines because of their close association with adverse health and environmental impacts. Among the alternative fuels being considered, biodiesel made by the transesterification of waste cooking oil has received wide attention in recent years because of its low cost and the added advantage of reducing waste oil disposal. This study was conducted to make a comparative evaluation of the particulate-bound elements emitted from ultra low sulphur diesel (ULSD) and waste cooking oil-derived biodiesel (B100) and a blend of both the fuels (B50). It was observed that the PM mass concentrations were reduced by about 36% when B100 was used. Crustal elements such as Mg, K and Al were found to be in higher concentrations compared to other elements emitted from both B100 and ULSD. Zn, Cr, Cu, Fe, Ni, Mg, Ba, K were found to be higher in the biodiesel exhaust while Co, Pb, Mn, Cd, Sr, and As were found to be higher in the ULSD exhaust. To evaluate the potential health risk due to inhalation of PM emitted from diesel engines running on ULSD and B100, health risk estimates based on exposure and dose–response assessments of particulate-bound elements were calculated assuming exposure for 24 h. The findings indicate that the exposure to PM of the B100 exhaust is relatively more hazardous and may pose adverse health effects compared to ULSD.► Particulate emissions from diesel, biodiesel and their blends were studied. ► The concentrations of 15 elements are reported. ► Health risk due to inhalation exposure is quantified.

Keywords: Waste cooking oil biodiesel; Health risk; Particulate matter; Ultra low sulphur diesel; Stationary engine

Peculiarities in atmospheric particle number and size-resolved speciation in an urban area in the western Mediterranean: Results from the DAURE campaign by C. Reche; M. Viana; T. Moreno; X. Querol; A. Alastuey; J. Pey; M. Pandolfi; A. Prévôt; C. Mohr; A. Richard; B. Artiñano; F.J. Gomez-Moreno; N. Cots (pp. 5282-5293).

Air quality degradation problems in urban environments are mainly due to road traffic emissions. In northern and central European cities extensive investigations have been carried out on the variability of number of ultrafine particles and black carbon, whereas studies in southern-Europe have traditionally focused on chemical speciation, resulting in insufficient information to characterise urban aerosol processes. Accordingly, sources and processes controlling atmospheric pollutants were evaluated during the international DAURE campaign in Barcelona (Spain), a typical urban environment in the western Mediterranean, by means of continuous measurements of particle number, black carbon, PMx, particulate nitrate and particulate sulphate concentrations. Results provided evidence of the influence of three PM sources of interest: road traffic, construction-demolition works and shipping emissions. Road traffic governs the daily cycle of black carbon, a number of gaseous pollutants and the finer fraction of PM. Evaluation of the coarse aerosol (PM_2.5-10) daily cycle furnished evidence of the influence of construction-demolition works. These activities could increase hourly PM_2.5-10 levels by up to 8 μg m⁻³ on an annual hourly mean basis. Finally, shipping emissions were traced by means of SO₂ concentrations, which peak at a time different from that of other gaseous pollutants owing to the regular daytime onshore breeze bringing harbour emissions at midday. Moreover, a major local contribution of secondary aerosols was detected with elevated particle number levels at midday when nucleation processes are favoured by photochemistry and lower pollution levels. Particle number data were also analysed in search for the primary emission of vehicle exhaust (N1) and the secondary parts from gaseous precursors, primary parts from non-traffic sources, and/or particles inherited in the air mass (N2). N2 fraction accounted for 40% of number concentrations, ranging from 37% during the morning rush hour to 61% at midday. Results proved that the combination of PM₁₀ and BC monitoring in urban areas may constitute a good approach to evaluate the traffic impact on air quality (BC), considering also the influence of other primary and secondary sources (PM₁₀).► We described the PM sources influencing a typical urban environment in the Mediterranean. ► Road traffic governs the daily cycle of black carbon, CO, NO_x and the finer fraction of PM. ► Construction-demolition works increased hourly PM_2.5-10 levels to 8 g m⁻³ on an hourly basis. ► Shipping emissions were traced by means of the daily cycle of SO₂. ► We detected a major local contribution of secondary particles, very significant at midday.

Keywords: City-works; Demolition; Urban; Nucleation; Coagulation; Shipping emissions

Air quality and health impact of PM₁₀ and EC in the city of Rotterdam, the Netherlands in 1985–2008 by Menno Keuken; Peter Zandveld; Sef van den Elshout; Nicole A.H. Janssen; Gerard Hoek (pp. 5294-5301).

A health impact assessment (HIA) of PM₁₀ and elemental carbon (EC) was performed for the period 1985–2008 in the city of Rotterdam. The spatial distribution of the concentrations was modeled by the URBIS model. The modeling results for 2008 were validated by PM₁₀ and EC measurements at various locations in Rotterdam. This paper describes the HIA related to improved air quality in the period 1985–2008: at urban background locations 18 μg m⁻³ PM₁₀ and 2 μg m⁻³ EC. The gain in life years saved due to long-term exposure to PM₁₀ and EC in this period was, respectively 13 and 12 month per person. The similar health impacts for PM₁₀ and EC suggests that reduction of combustion aerosol was important for the reduction in health impact of PM₁₀.► Health impact assessment of PM₁₀ and EC in Rotterdam (NL) in 1985–2008. ► Life years saved for PM₁₀ and EC was respectively 13 and 12 month per person. ► Reduction of combustion aerosol important cause for improved air quality.

Keywords: Health impact assessment; PM; ₁₀; EC; Historical trend

Causes of high O₃ in the lower free troposphere over the Pacific Northwest as observed at the Mt. Bachelor Observatory by J.L. Ambrose; D.R. Reidmiller; D.A. Jaffe (pp. 5302-5315).

We measured O₃, CO, Hg, sub-micron particle scattering of mid-visible light ( σ_sp), and water vapor (WV) at the Mt. Bachelor Observatory (MBO) in central Oregon, USA since 2004. The data were used to identify sources of large ozone enhancements in the lower free troposphere (FT). A total of 25 high-ozone events, defined as time periods when the 8-h averaged O₃ mixing ratio was >70.0ppbv, were recorded. The events occurred between early March and late September. For 18 of the 25 event days we were able to identify sources based on (1) relative enhancements of O₃, CO, Hg and WV compared with the corresponding monthly distributions and (2) supporting data from the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model, the Navy Aerosol Analysis and Prediction System (NAAPS) global aerosol model, and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite-derived active fire counts from the Fire Information for Resource Management System (FIRMS). Our analysis suggests that enhanced O₃ levels during all the identified events were transported to MBO in the FT and were driven mostly by subsidence of O₃-rich air masses from the upper troposphere/lower stratosphere (UT/LS), Asian long range transport (ALRT) and mixed ALRT+UT/LS influences. The UT/LS events were depleted in CO and total atmospheric mercury (TAM) compared to monthly median values. Levels of O₃ and CO tended to be anti-correlated during UT/LS events, consistent with transport from clean regions in the UT. Conversely, the ALRT events were characterized by concomitant enhancements in CO and TAM with mean values during each event that were >70th percentile values for the months during which the events occurred. Unlike for UT/LS events, levels of O₃ and CO during ALRT events tended to be correlated, consistent with photochemical O₃ production in polluted air masses transported across the Pacific. The mixed ALRT+UT/LS events exhibited characteristics that were intermediate between those of the ALRT and UT/LS events. For the classifiable cases the fractional distribution of each event type was: UT/LS, ∼44% ( n=8); ALRT+UT/LS, ∼33% ( n=6); ALRT, ∼22% ( n=4). In terms of the total number of classifiable high-ozone event hours UT/LS, ALRT+UT/LS and ALRT events accounted for ∼52% ( t=85), ∼36% ( t=59) and ∼13% ( t=21), respectively. The results indicate that downward mixing of O₃-rich air masses from the UT/LS together with trans-Pacific transport of urban/industrial and biomass burning emissions from the Asian continent are the most important mechanisms for delivering high O₃ levels (i.e., 8-h averages >70.0ppbv) to the lower FT in the Pacific Northwest.► In this study we determine causes of high ozone at the Mt. Bachelor Observatory. ► High-ozone events occur during spring, summer and fall. ► High ozone is mostly transported from the upper troposphere/lower stratosphere. ► High ozone is also traced to Asian anthropogenic and biomass burning emissions.

Keywords: Ozone; Pacific Northwest; Upper troposphere; Lower stratosphere; Asian long-range transport; Total atmospheric mercuryAbbreviations; ALRT; Asian long range transport; BB; biomass burning; BL; boundary layer; ER; enhancement ratio; FT; free troposphere; GEM; gaseous elemental mercury; LS; lower stratosphere; MBO; Mt. Bachelor Observatory; MFR; Medford, Oregon; NABB; North American biomass burning; NAI; North American industry; PHg; particulate mercury; PNW; Pacific Northwest; RGM; reactive gaseous mercury; SLE; Salem, Oregon; STE; stratosphere–troposphere exchange; TAM; total atmospheric mercury; TF; tropopause folding; TPP; tropopause pressure; UT; upper troposphere; WV; water vapor

A model-driven approach to estimate atmospheric visibility with ordinary cameras by Raouf Babari; Nicolas Hautière; Éric Dumont; Roland Brémond; Nicolas Paparoditis (pp. 5316-5324).

Atmospheric visibility is an important input for road and air transportation safety, as well as a good proxy to estimate the air quality. A model-driven approach is presented to monitor the meteorological visibility distance through use of ordinary outdoor cameras. Unlike in previous data-driven approaches, a physics-based model is proposed which describes the mapping function between the contrast distribution in the image and the atmospheric visibility. The model is non-linear, which allows encompassing a large spectrum of applications. The model assumes a continuous distribution of objects with respect to the distance in the scene and is estimated by a novel process. It is more robust to illumination variations by selecting the Lambertian surfaces in the scene. To evaluate the relevance of the approach, a publicly available database is used. When the model is fitted to short range data, the proposed method is shown to be effective and to improve on existing methods. In particular, it allows envisioning an easier deployment of these camera-based techniques on multiple observation sites.► A model-driven approach to monitor atmospheric visibility distance by camera. ► A method robust to illumination variations by selecting the Lambertian surfaces. ► A physics-based model which maps the contrast and the atmospheric visibility. ► A novel data fitting process limited to a reliable subset of the data.

Keywords: Atmospheric visibility; Air quality; Image processing; Transportation safety

Kinetic study of the OH-initiated photo-oxidation of four unsaturated (allyl and vinyl) ethers under simulated atmospheric conditions by Silvina A. Peirone; Juan P. Aranguren Abrate; Raúl A. Taccone; Pablo M. Cometto; Silvia I. Lane (pp. 5325-5331).

Using the relative rate technique, rate constants for the gas-phase reactions of hydroxyl radicals with n-propyl vinyl ether ( k₁), 2-chloroethyl vinyl ether ( k₂), allyl ether ( k₃) and allyl ethyl ether ( k₄) have been measured. Experiments were carried out at (298±2)K and atmospheric pressure using N₂ and ultra pure air as bath gas. Using isoprene, 1-methyl-1-cyclohexene, 2-methyl-2-butene, 3-buten-1-ol and 2-methyl-2-propen-1-ol as reference compounds, the following rate constants were derived: k₁=(11.0±0.4)×10⁻¹¹, k₂=(9±1)×10⁻¹¹, k₃=(6.8±0.7)×10⁻¹¹ and k₄=(4.2±0.7)×10⁻¹¹, in units of cm³molecule⁻¹s⁻¹. This is the first experimental detcermination of k₂– k₄. The rate constants obtained are compared with the previous literature data for corresponding alkenes reactions with OH and the observed reactivity trends are discussed. The atmospheric implications of the results are considered.► We provide the rate constants of OH radicals with four unsaturated ethers reactions. ► A relative technique at 298K and a pressure of 1atm was used. ► The atmospheric implications of the results are considered.

Keywords: Hydroxyl radicals; Vinyl ethers; Allyl ethers; Rate constants; Tropospheric chemistry

Determination of hexavalent chromium in ambient air: A story of method induced Cr(III) oxidation by Kristof Tirez; Geert Silversmit; Nico Bleux; Elke Adriaensens; Edward Roekens; Kelly Servaes; Chris Vanhoof; Laszlo Vincze; Patrick Berghmans (pp. 5332-5341).

The accuracy of the determination of Cr(VI) in ambient particulate matter remains a challenge from the point of view of minimal Cr species interconversion. Knowledge of this method induced oxidation and reduction is particularly relevant for the determination of Cr(VI) in ambient particulate matter, as the level of observed Cr(III) oxidation (average of 1.7% in this study) can contribute significantly to the monitored range of measured Cr(VI) in PM₁₀. For Cr concentrations in PM₁₀ > 10 ng Cr m⁻³, this method induced oxidation could lead to false positive exceeding of an air quality guideline value of 0.2 ng Cr(VI) m⁻³ in PM₁₀. The median daily Cr(VI) concentration in PM₁₀ measured over a monitoring period of more than 2 months at two locations close to a stainless steel factory amounted to 0.9 ng Cr(VI) m⁻³ and 0.27 ng Cr(VI) m⁻³. Average daily Cr(VI)/Cr ratios in PM₁₀ of 3.5% and 2.6% were measured at these locations. The described monitoring for the determination of Cr(VI) in ambient air via alkaline impregnated filters is sensitive (method detection limit of 0.015 ng Cr(VI) m⁻³) and reproducible (precision of the method ∼25%). The average Cr(VI) recovery of 75% strongly indicates the effects of ambient sampling conditions and ambient particles on the Cr(VI) recoveries. The stability of the Cr(VI) and the Cr(III) spike on 0.12 M NaHCO₃ impregnated filters observed with XANES, indicates that the alkaline extraction of the filter in combination with the sampled air matrix is likely to induce the Cr conversions. The XANES spectra shows further that a Cr-spinel is the predominant component of Cr in ambient air PM₁₀ at the monitored locations.► Monitoring methods for Cr(VI) in PM₁₀ using extraction may induce Cr(III) oxidation. ► The literature with respect to Cr species interconversion is critically reviewed. ► Monitoring data were acquired on Cr(VI), Cr(III) and Cr species stability in PM₁₀. ► XANES stability measurement of Cr(III) and Cr(VI) on alkaline impregnated filters. ► Prolonged X-ray irradiation (XANES) induces reduction of Cr(VI) on filter.

Keywords: Hexavalent chromium; Trivalent chromium; Interconversion; Stability; XANES; Particulate matter; Monitoring method

New specific indicators for qPCR monitoring of airborne microorganisms emitted by composting plants by Olivier Le Goff; Jean-Jacques Godon; Jean-Philippe Steyer; Nathalie Wéry (pp. 5342-5350).

Bioaerosols emitted from composting plants are an issue because of their potential harmful impact on public or workers’ health. There is a major lack of knowledge concerning the dispersal of airborne microorganisms emitted by composting plants and the consequent potential exposure of nearby residents. This inadequate knowledge is partly due to the fact that there is currently no method for specifically tracing these microorganisms in the air. The objective of this study was to validate the use of microbial groups as indicators of composting bioaerosols by comparing their concentration in air samples, whether impacted by composting activity or not. Three potential microbial indicators were chosen among the core species of composting bioaerosols. They belong to the genus Saccharopolyspora, to the Thermoactinomycetaceae and to the fungus Thermomyces. Quantitative PCR systems using TaqMan probes were designed to quantify each of the three phylotypes in air samples collected outdoors in natural environments and at composting plants. Compost-turning operations at industrial plants resulted in an increase in the concentration of the three phylotypes of at least 2 orders of magnitude when compared to the concentration measured in control samples collected upwind, and of at least 1 order of magnitude compared to the background concentration measured in natural environments unaffected by industrial activity. In conclusion, these three thermophilic phylotypes can be used as indicators of airborne microorganisms emitted by industrial composting plants. They may be particularly relevant in studying the dispersal of bioaerosols around composting plants and the exposure of nearby residents. This is the first time that indicators of compost bioaerosols have been validated by comparing their concentrations in impacted samples to their background levels in natural environments.► Three novel microbial indicators of composting bioaerosols were identified. ► Specific qPCR systems were designed for each of them. ► Their background concentration in the air from natural environments was determined. ► An increase in concentrations during the turning of composting piles was demonstrated. ► These thermophilic microorganisms can be used to monitor composting bioaerosols.

Keywords: Compost; Bioaerosol; Indicator; Thermophiles; qPCR; SSU rDNA

Characterization of PM₁₀ source profiles for fugitive dust in Fushun-a city famous for coal by Shaofei Kong; Yaqin Ji; Bing Lu; Li Chen; Bin Han; Zhiyong Li; Zhipeng Bai (pp. 5351-5365).

A total of 120 fugitive dust samples were collected to acquire chemical source profiles of PM₁₀ in Fushun including 27 soil dust samples, 32 road dust samples, 19 construction dust samples, 13 coal storage pile samples, 2 cement production samples, 13 coal-fired power plant fly ash samples, 5 fly ash samples from iron smelt plant and 9 samples from industrial raw material and production piles. The samples were classified as 20 subtypes. The dust samples were dried, sieved, resuspended and sampled through a PM₁₀ inlet onto filters, and then chemically analyzed. Inductively coupled plasma-atomic emission spectrometry, ion chromatograph and thermal/optical reflectance methods were adopted for analyzing twenty elements including Na, Mg, Al, Si, S, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, Pb and Hg and nine ions including Na⁺, NH₄⁺, K⁺, Mg²⁺, Ca²⁺, F⁻, Cl⁻, NO₃⁻ and SO₄²⁻ as well as OC and EC, respectively.The chemical compositions were compared for 20 subtypes. Si and Ca were the most abundant elements in all the fugitive dust profiles. Enrichment factors of elements in fly ashes compared to raw coal were calculated with Fe as reference element. The highest enriched elements were Ni, Cu, Zn and Pb. Significant difference existed among PM₁₀ profiles with the coefficient of divergence values ranging from 0.28 to 0.78. Profiles were compared with others. Si exhibited lower content in this study for soil and road dust while EC and Cr showed much higher content compared to others indicating the influence of coal mining and industries activities in Fushun. This was validated by source signatures analysis which indicated almost all the fugitive dust were relative to coal and may also be influenced by metallurgy. The ratios of Mn/V, V/Ni, Zn/Pb and Zn/Cd were calculated for source identification. Elemental ratios may vary widely even for the same source types with different processing courses. Chemical profiles of fugitive dust should be established based on characteristic sources for a specific region and updated timely.► 20 subtypes of fugitive dust profiles were established. ► Ni, Cu, Zn and Pb were enriched in fly ashes compared to raw coal. ► Almost all the fugitive dust were relative to coal and metallurgy in Fushun. ► Mn/V, V/Ni, Zn/Pb and Zn/Cd were calculated for source identification. ► Elemental ratios may vary widely for different subtypes of the same source.

Keywords: PM; ₁₀; Fugitive dust; Profile; Source signiture; Elemental ratio; Fushun

Do pressure changes have an influence on ambient air chemiluminescence NO_x measurements? by Marta Doval Miñarro; Enrique González Ferradás; Cristina Romero Trigueros; Jonathan Barberá Rico (pp. 5366-5375).

Users of automatic air pollution monitors are largely unaware of how certain parameters, like pressure, can affect readings. The present work examines the influence of inlet pressure changes on chemiluminescence NO_x measurements. These changes have been grouped into two categories: (i) those due to changes in atmospheric pressure and (ii) those produced by any other reason (e.g., clogs in the inlet sampling line). Atmospheric pressure changes were simulated varying both the inlet and the outlet sample line pressures in the same way, whereas sample pressure changes were produced modifying only the inlet sample line pressure. Analyzer calibration was performed with zero air and 200 nmol mol⁻¹ of NO at 101.3 kPa. The test pressures ranged from −10 to +10 kPa with respect to the calibration pressure. ANOVA and Dunnett's tests were performed to look for significant differences between measurements obtained under calibration conditions and those obtained under different pressure conditions. The differences in measurements were practically negligible for fixed analyzers subjected to usual changes in atmospheric pressure (<±5 kPa); however, differences could be as high as 7% if ±10 kPa pressure changes took place in the inlet sample line for causes included in the second group.► Pressure changes on NO_x chemiluminescence measurements have been studied. ► Deviations in measurements are negligible for fixed analyzers subjected to usual changes in atmospheric pressure (<±5 kPa). ► If pressure changes are due to different causes, deviations can be as high as 7% for ±10 kPa pressure changes. ► Operational procedures are given in order to minimise these deviations.

Keywords: Air monitoring; Pressure changes; Data quality; NO; _x; measurements

Determination of particle deposition in enclosed spaces by Detached Eddy Simulation with the Lagrangian method by Miao Wang; Chao-Hsin Lin; Qingyan Chen (pp. 5376-5384).

Accurate prediction of particle deposition in airliner cabins is important for estimating the exposure risk of passengers to infectious diseases. This study developed a Detached Eddy Simulation (DES) model with a modified Lagrangian method. The computer model was validated with experimental data for particle deposition in a cavity with natural convection and with air velocity, air temperature, and particle concentration data from a four-row, twin-aisle cabin mockup. The validation showed that the model performed well for the two cases. Then the model was further used to study particle deposition in the cabin mockup with seven sizes of particles. The particles were assumed to be released from an index passenger due to breathing or talking at zero velocity and due to coughing at a suitable jet velocity. This study can provide quantitative particle deposition distributions for different surfaces and particles removed by cabin ventilation.► We developed a Lagrangian particle deposition model with Detached Eddy Simulation. ► This deposition model was validated by experimental measurements. ► This model was applied to simulate particle deposition in an airplane cabin mockup. ► Quantitative particle deposition distribution for different surfaces was simulated. ► The particle deposition depends on particle size, release mode and airflow field.

Keywords: CFD; Experiment; Particle; Deposition; Indoor

The June 2007 Saharan dust event in the central Mediterranean: Observations and radiative effects in marine, urban, and sub-urban environments by J.L. Gómez-Amo; V. Pinti; T. Di Iorio; A. di Sarra; D. Meloni; S. Becagli; V. Bellantone; M. Cacciani; D. Fuà; M.R. Perrone (pp. 5385-5393).

A desert dust episode in June 2007 and its radiative effects on the energy budget have been studied at three Italian stations (Rome, Lecce and Lampedusa) with the aim of investigating the interactions with different conditions and aerosol types over the Mediterranean. The three sites are representative for urban (Rome), sub-urban/rural (Lecce), and marine (Lampedusa) environment, respectively in the central Mediterranean region. Measured ground-based column-averaged aerosol optical properties and aerosol extinction profiles were used to initialize the MODTRAN4 radiative transfer model. The radiative transfer model was used to estimate the shortwave aerosol radiative forcing ( ARF) and its forcing efficiency ( FE) at two different solar zenith angles (20° and 60°) in the 280–2800 nm spectral range.The goal was to investigate the role of different aerosol types in the atmospheric boundary layer on the radiative budget during a dust event. During the event the aerosol optical depth was moderately high and similar at the three stations, with a maximum value of about 0.6. The Ångström exponent was found to increase with the distance from the source (0.21, 0.36, and 0.43 at Lampedusa, Rome, and Lecce, respectively). Differences in the aerosol optical properties were observed, also depending on the aerosol type assumed in the boundary layer. The estimated direct aerosol forcing appears to depend on the changes in aerosol properties and to the surface albedo. The results show that the desert dust produces a cooling effect at both surface (largest ARF of −224 W m⁻² at 20° solar zenith angle at Rome) and top of the atmosphere (largest ARF of −19 W m⁻² at 20° solar zenith angle at Lecce). The cooling is largest in the rural and smallest in the marine environment. The surface forcing efficiency appears to be strongly affected by the aerosol absorption in the BL. Large differences exist between our results and the FE determinations by AERONET, derived considering a single layer with homogeneous optical properties and prescribed vertical distribution. The FE deviations are around 20, 60, and 40% at the surface, TOA, and in the atmosphere, respectively. These results suggest that the detailed description of the vertical distribution of the aerosol properties is needed for an accurate determination of its radiative effects.► We describe an intense Saharan Dust event in the Central Mediterranean. ► We combine ground-based aerosol measurements and radiative transfer modelling. ► We study the desert dust optical properties and its radiative forcing. ► We investigate the dust interactions with different boundary layer aerosol and surface conditions over the Mediterranean. ► We introduce the vertical distribution of the aerosol optical properties in the radiative transfer simulations.

Keywords: Aerosol optical properties; Vertical distribution; Radiative forcing; Desert dust event

Analysis of unregulated emissions from an off-road diesel engine during realistic work operations by Magnus Lindgren; Karine Arrhenius; Gunnar Larsson; Linda Bäfver; Hans Arvidsson; Christian Wetterberg; Per-Anders Hansson; Lars Rosell (pp. 5394-5398).

Emissions from vehicle diesel engines constitute a considerable share of anthropogenic emissions of pollutants, including many non-regulated compounds such as aromatic hydrocarbons and alkenes. One way to reduce these emissions might be to use fuels with low concentrations of aromatic hydrocarbons, such as Fischer–Tropsch (F–T) diesels. Therefore this study compared Swedish Environmental Class 1 diesel (EC1) with the F–T diesel fuel Ecopar™ in terms of emissions under varied conditions (steady state, controlled transients and realistic work operations) in order to identify factors influencing emissions in actual operation.Using F–T diesel reduced emissions of aromatic hydrocarbons, but not alkenes. Emissions were equally dependent on work operation character (load, engine speed, occurrence of transients) for both fuels. There were indications that the emissions originated from unburnt fuel, rather than from combustion products.► Investigated unregulated emissions from standard diesel and Fischer–Tropsch fuel. ► Observed at steady state and during transients and work operations. ► Aromatics lowest with Fischer–Tropsch. ► Transients had a similar impact with both fuels. ► Emission trends during transients similar to hydrocarbon emission trends.

Keywords: Fischer–Tropsch; Diesel; Steady state; Transient; Unregulated emissions; Benzene; Alkenes

Atmospheric cloud water contains a diverse bacterial community by Peter S. Kourtev; Kimberly A. Hill; Paul B. Shepson; Allan Konopka (pp. 5399-5405).

Atmospheric cloud water contains an active microbial community which can impact climate, human health and ecosystem processes in terrestrial and aquatic systems. Most studies on the composition of microbial communities in clouds have been performed with orographic clouds that are typically in direct contact with the ground. We collected water samples from cumulus clouds above the upper U.S. Midwest. The cloud water was analyzed for the diversity of bacterial phylotypes by denaturing gradient gel electrophoresis (DGGE) and sequencing of 16S rRNA gene amplicons. DGGE analyses of bacterial communities detected 17–21 bands per sample. Sequencing confirmed the presence of a diverse bacterial community; sequences from seven bacterial phyla were retrieved. Cloud water bacterial communities appeared to be dominated by members of the cyanobacteria, proteobacteria, actinobacteria and firmicutes.► We collected samples from warm, cumulus clouds over forested areas in Michigan. ► We determined bacterial diversity in cloud water using DGGE and DNA Sequencing. ► Cloud water contains a diverse bacterial community. ► We identified bacteria that can potentially act as condensation and ice nuclei.

Keywords: Cloud water; Bacteria; PCR–DGGE; 16S rDNA

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Atmospheric Environment (v.45, #30)