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Atmospheric Environment (v.45, #29)
Intra-urban and street scale variability of BTEX, NO2 and O3 in Birmingham, UK: Implications for exposure assessment by Sotiris Vardoulakis; Efisio Solazzo; Julio Lumbreras (pp. 5069-5078).
Automatic monitoring networks have the ability of capturing air pollution episodes, as well as short- and long-term air quality trends in urban areas that can be used in epidemiological studies. However, due to practical constraints (e.g. cost and bulk of equipment), the use of automatic analysers is restricted to a limited number of roadside and background locations within a city. As a result, certain localised air pollution hotspots may be overlooked or overemphasised, especially near heavily trafficked street canyons and intersections. This has implications for compliance with regulatory standards and may cause exposure misclassification in epidemiological studies. Apart from automatic analysers, low cost passive diffusion tubes can be used to characterise the spatial variability of air pollution in urban areas.In this study, BTEX, NO2 and O3 data from a one-year passive sampling survey were used to characterise the intra-urban and street scale spatial variability of traffic-related pollutants in Birmingham (UK). In addition, continuous monitoring of NO2, NOx, O3, CO, SO2, PM10 and PM2.5 from three permanent monitoring sites was used to identify seasonal and annual pollution patterns. The passive sampling measurements allowed us to evaluate the representativeness of a permanent roadside monitoring site that has recorded some of the highest NO2 and PM10 concentrations in Birmingham in recent years. Dispersion modelling was also used to gain further insight into pollutant sources and dispersion characteristics at this location. The strong spatial concentration gradients observed in busy streets, as well as the differences between roadside and urban background levels highlight the importance of appropriate positioning of air quality monitoring equipment in cities.► We use passive diffusion tubes to measure BTEX, NO2 and O3 concentrations in three urban locations. ► We apply the Operational Street Pollution Model (WinOSPM) to characterise pollutant dispersion in a busy street. ► Street scale spatial variability of traffic-related pollutants is very high in urban areas. ► Passive diffusion tube measurements on building façades underestimate roadside exposure. ► Area misclassification may occur in exposure studies relying on sparse air quality measurements.
Keywords: Urban air quality; Benzene; Nitrogen dioxide; Ozone; Traffic emissions; Spatial variability; Exposure
Development of an emission processing system for the Pearl River Delta Regional air quality modeling using the SMOKE model: Methodology and evaluation by Shuisheng Wang; Junyu Zheng; Fei Fu; Shasha Yin; Liuju Zhong (pp. 5079-5089).
An emission pre-processing tool is generally needed to transform a bulk annual emission inventory into gridded, temporal (monthly, weekly, and hourly), and speciated emissions in order to use complex air quality models such as the Community Multi-scale Air Quality (CMAQ) model to assess control strategies, forecast air quality, and investigate pollution formation and transport processes. To support the regional air quality modeling in the Pearl River Delta (PRD), we developed an emission pre-processing system, Sparse Matrix Operator Kernel Emissions-PRD (SMOKE-PRD), based on the U.S. Environmental Protection Agency (USEPA)/SMOKE model. This paper introduces the methods and procedures for adapting the SMOKE model to the PRD regional bulk emissions. These include the compilation of the PRD local source-class clarification codes, the incorporation of the PRD local emission inventory, and the updating of spatial, temporal, and chemical speciation information. The SMOKE-PRD system was evaluated, and a case study on ozone simulation was conducted to demonstrate the applicability of the SMOKE-PRD system. Results show that the model can properly simulate temporal variations, spatial patterns, and peak values of O3 concentrations in the PRD region, suggesting the SMOKE-PRD system was successfully localized and can be used to provide model-ready emissions for regional air quality modeling in the PRD region. This work can be extended for adapting the SMOKE model to process emissions for modeling use in other regions of China.► The methods for developing and validating SMOKE-PRD system were introduced. ► The SMOKE-PRD was updated with local emissions, temporal and spatial information. ► The MEGAN model was integrated to SMOKE-PRD system for estimating biogenic emissions. ► The SMOKE-PRD was evaluated with an ozone modeling case study. ► The SMOKE-PRD was shown to be capable of supporting PRD regional air quality modeling.
Keywords: Emission processing; SMOKE model; SMOKE-PRD; CMAQ model; Ozone
Contribution of the road traffic to air pollution in the Prague city (busy speedway and suburban crossroads) by J. Ondráček; J. Schwarz; V. Ždímal; L. Andělová; P. Vodička; V. Bízek; C.-J. Tsai; S.-C. Chen; J. Smolík (pp. 5090-5100).
Two measurement campaigns near busy freeway and suburban crossroad (different traffic intensity) were carried out in Prague city. Both of the two traffic related campaigns were supported with simultaneous measurements at suburban background site to compare measured values with corresponding city background. Extensive set of aerosol instrumentation was used during both campaigns at both measurement sites. Two aerosol spectrometer sets (SMPS and APS) were used to monitor aerosol particle number size distribution. Two BLPI provided information about mass size distribution and chemical composition of collected size resolved aerosol samples. The crossroad campaign was also supported by two EC/OC field analysers providing information about elemental and organic carbon concentrations. Consequent chemical analysis of collected size resolved samples comprised of ion chromatography (water soluble ions), PIXE (elements) and RBS (carbon). Results obtained from spectrometers and BLPIs showed that the main contribution of traffic in ultrafine size range can be attributed to direct exhaust emissions, while the coarse fraction was dominated mainly by regional background aerosol with small traces of brake and tyre abrasion as well as the resuspension of the road dust. Chemical analysis demonstrated that most of the water soluble ions can be found in fine fraction of mass distribution and mostly comes from regional background and long range transport. Most of major elements were found in coarse fraction of mass size distribution and it can be attributed to three different sources: abrasion of different vehicle parts (Fe, Cu, Mn and Zn), resuspension of the road dust (Si, Al, Ca) and long range transport or regional background (Ca and K). Elemental carbon concentration (diesel engine emissions) was found to be proportional to traffic intensity.► Aerosol measurements near busy freeway, suburban crossroad and suburban background. ► Measurements of number and mass size distribution, chemical analysis and EC/OC. ► Water soluble ions in fine fraction (regional backround and long range transport). ► Major elements in coarse fraction (abrasion, resuspension and regional backround).
Keywords: Road traffic aerosol; Number and mass size distribution; Chemical composition
A seven-year study of oxygen isotopes in daily precipitation at a site close to the Arctic Circle, Tustervatn, Norway: Trajectory analysis and links with the North Atlantic Oscillation by Wilfred H. Theakstone (pp. 5101-5109).
Daily precipitation δ18O values were recorded through a 7-year period at Tustervatn, Norway, close to the Arctic Circle. Seasonal variations were superimposed on an overall rising trend. Cluster analysis of air mass trajectories revealed five principal moisture source areas and transport routes to Tustervatn. Both daily precipitation amounts and δ18O values differed between the trajectory clusters. Seasonal differences of the frequency of trajectory clusters were reflected in the relationship of precipitation δ18O values to regional temperatures, which was strongest in winter (DJF). Monthly precipitation totals varied with the North Atlantic Oscillation (NAO) index. The relationship of DJF precipitation to the NAO index was particularly strong, but varied between air mass trajectory clusters. The relationship of DJF precipitation and NAO index at Tustervatn differs from that at Tasiilaq, southeast Greenland, which is at around the same latitude. DJF precipitation totals at Tustervatn tend to be higher when the NAO index is higher; at Tasiilaq, the trend is for lower DJF precipitation at higher NAO index values. The contrasting NAO/climate relations reflect the location of the two sites with respect to that of the Icelandic low.► 7-year record of oxygen isotopic composition of daily precipitation close to the Arctic Circle. ► Cluster analysis of air mass trajectories identified five major moisture transport patterns. ► Monthly precipitation was higher when the NAO index was positive than when it was negative. ► Marked disparity of DJF precipitation/NAO index relation at Tustervatn and Tasiilaq Greenland.
Keywords: Oxygen isotopes; Precipitation; Trajectories; Cluster analysis; North Atlantic Oscillation; Arctic
The dynamics of ammonia release from animal wastewater as influenced by the release of dissolved carbon dioxide and gas bubbles by V. Blanes-Vidal; E.S. Nadimi (pp. 5110-5118).
The largest global source of atmospheric ammonia is animal wastewater. Previous models to predict the release of ammonia from animal wastewater have focused on undisturbed conditions. However in animal facilities the surface of wastewater is constantly disturbed due to liquid addition and wastewater management. This paper presents a gas emission-pH-film model (GE-pH-film model) that describes the dynamics of ammonia release from swine wastewater after surface liquid disturbances, considering volatilization of dissolved carbon dioxide, surface pH changes, bubble-enhanced ammonia volatilization and surface film formation. The GE-pH-film model improved the accuracy of estimated ammonia release during the first 10 h after liquid disturbance, from an averaged error of 82% (gas emission model) to 25% (GE-pH-film model). Neglecting the bubble-enhanced NH3 volatilization and the surface film formation (i.e. GE-pH model), led to an averaged error on NH3 release of 43%.► Animal slurry in farms is frequently disturbed. ► The release of NH3 immediately after disturbances is minimum. ► Then NH3 release increases until it reaches a steady condition. ► This pattern is related to the release of dissolved CO2 and surface film formation. ► A model describing this process is presented.
Keywords: NH; 3; Emission; CO; 2; Slurry; Crust
Diagnosis of an underestimation of summertime sulfate using the Community Multiscale Air Quality model by Chao Luo; Yuhang Wang; Stephen Mueller; Eladio Knipping (pp. 5119-5130).
We evaluate the simulations of SO2 and sulfate using the Community Multiscale Air Quality model (CMAQ) version 4.6 with the observations over the United States in 2002. MM5 was used for meteorological simulations. While the general seasonal cycles of SO2 and sulfate are simulated well by the model, we find significant systematic biases in the summer. The model low bias in sulfate is considerably more severe than the model bias in SO2. Both ACM and RADM schemes are used in the model to test the sensitivities of simulated sulfate to cloud processing. We carry out detailed modeling analysis and diagnostics for July 2002. Compared to satellite observations of cloud liquid water path, CMAQ cloud modules greatly overestimates convective (sub-grid) precipitating clouds, leading to large overestimation of sulfate wet scavenging. Limiting convective precipitating cloud fraction in the cloud modules to <10% and hence significantly reducing wet scavenging lead to much improved agreement between simulated and observed sulfate. The average lifetime of sulfate in the model increases from 1–2 days to 3–4 days for July. We show that a potential model problem of excessive wet scavenging of sulfate does not necessarily lead to apparent problems in model simulations of sulfate wet deposition rate compared to surface observations. In general, there is still a lack of direct observational constraints from air quality monitoring measurements on model simulated cloud processing of SO2 and sulfate.► We evaluate the simulations of SO2 and sulfate using CMAQ4.6 over the USA in 2002. ► We find systematic low biases for sulfate in the summer. ► We find module greatly overestimates (sub-grid) convective clouds. ► We find to limit convective cloud fraction and hence to improve model performance.
Keywords: Community Multiscale Air Quality; Model; Sulfate; Cloud processing; Model evaluation
Insights into summertime haze pollution events over Shanghai based on online water-soluble ionic composition of aerosols by Huanhuan Du; Lingdong Kong; Tiantao Cheng; Jianmin Chen; Jianfei Du; Ling Li; Xiangao Xia; Chunpeng Leng; Guanghan Huang (pp. 5131-5137).
An online analyzer for Monitoring for AeRosols and Gases (MARGA) was employed to measure major water-soluble (WS) inorganic ions in PM10 at 1-h time resolution in Shanghai from May 27 to June 16, 2009. During the field campaign, hazy days were encountered over which atmospheric visibility was commonly less than 10 km, and hourly average PM10 reached peaks of exceeding 150 μg m−3. Based on WS ions and pollution gases, the haze events were classified as biomass burning induced, complicated and secondary aerosol pollutions depending on their distinct formation schemes. During the biomass burning induced pollution, which was aroused from biomass burning plume, the concentration of K+ was increasing up to maximum about 19 times higher than the average of clear days, and K+ behaved a strong positive linear correlation with Cl−. Because of sulfate and nitrate significantly enhanced by secondary production, in which precursor gases of SO2 and NO2 were converted into SO42− and NO3− on the surface of pre-existing KCl particles, the complicated pollution was responsible for a combining contribution of aerosols directly transported from biomass burning sources and known secondary aerosols linked to local emission. Under high atmospheric oxidation ability and steady atmosphere condition, the secondary pollution resulted from a significant increase of sulfate and nitrate aerosols which were oxidized from large amounts of anthropogenic gases of SO2 and NO2 in the urban atmosphere.► The data at 1-h resolution is help to characterizing haze pollution more details. ► The haze events were classified as biomass burning, complicated and secondary pollutions. ► Biomass burning plumes could cause complicated pollution over downwind regions.
Keywords: Aerosol; Haze; Water-soluble ion; Biomass burning
Size distribution of atmospheric aerosols at Maitri, Antarctica by Vimlesh Pant; Devendraa Siingh; A.K. Kamra (pp. 5138-5149).
Measurements of the concentration and size distribution of the atmospheric aerosol particles in the size range of 0.003–20 μm diameter have been made at Maitri (70°45′52″S, 11°44′03″E) during January–February, 2005. The measured particle size ranges extended from 0.5 to 20 μm throughout the period, from 0.016 to 0.7 μm in January and 0.01 to 0.4 μm in February. For short intervals of time, comprising a total period of 210 h, the measurements were made for particles in the size range of 0.003–0.16 μm. Total particle number concentrations of coarse and fine particles vary from 0.1 to 0.8 and from 100 to 2000 particles cm−3, respectively. The fine particle concentration undergoes a diurnal variation with values remaining low (300–400 cm−3) during low sun periods and increasing up to ∼750 cm−3 at noontime. The monthly-averaged number size distributions show maxima in accumulation mode at 0.772 ± 0.023 μm, in Aitken mode at 0.089 ± 0.005 μm in January which shifts to 0.03 ± 0.003 μm in February, and in nucleation mode at 0.018 ± 0.002 μm. The hourly-averaged curves can have one mode each in coarse, accumulation, and nucleation size ranges, and two modes in Aitken size range of particles. Total number concentration of particles in coarse mode is higher in oceanic than in continental air masses. Further, while the oceanic air masses have nucleation mode at 0.01 μm and Aitken mode at 0.024 μm, continental air masses have nucleation mode at 0.017 μm. Intermixing of the two air masses at coastal site results in multi-modal size distributions. It is inferred that while in continental air masses the nucleation mode particles are aged, in oceanic air masses these are likely to be transported from the upper troposphere under subsidence of cyclonic storms revolving around the continent of Antarctica.► Fine particles dominate total aerosol number concentrations at Maitri. ► Hourly-averaged aerosol size distributions at Maitri are multi-modal. ► Size distributions of Aitken particles at Maitri may be bimodal also. ► Higher coarse particle concentrations in oceanic than in continental air – masses. ► Nucleation mode appears at 0.01 μm in oceanic and at 0.017 μm in continental air-masses.
Keywords: Antarctic aerosols; Aerosol size distribution; Nucleation mode particles; Marine aerosols
Effect of stack height and exhaust velocity on pollutant dispersion in the wake of a building by M. Lateb; C. Masson; T. Stathopoulos; C. Bédard (pp. 5150-5163).
The dispersion of pollutants exhausted from a building roof stack located in the wake of a tower is investigated by means of the realizable k– ɛ turbulence model. Variations in stack height and pollutant exhaust velocity are considered to assess their influence on the distribution of pollutant concentrations in the neighbourhood of the emitting building. In order to determine optimum locations for fresh-air intakes, the worst case is considered, namely when the wind originates directly upstream of the tower and places the emitting building in its wake. Special attention is given to the evolution of the plume and distribution of pollutant concentrations on the roof and windward wall of the emitting building, as well as on the leeward wall of the upwind tower. Simulation results are compared to wind tunnel experiments conducted in a boundary layer wind tunnel. For this particular configuration, the paper shows that increasing the stack height has an effect similar to that obtained by increasing the momentum ratio, but with some differences, depending upon which wall of the two buildings is considered. On the emitting building, the leeward wall has the lowest concentration values for all stack heights and momentum ratios considered; thus this is the best location for fresh-air intakes. However, for the tower, fresh-air intakes should not be located on the leeward wall due to high pollutant concentrations. The results show completely different pollutant dispersion patterns from those for an isolated building. This highlights the importance of accounting for structures that lie in close proximity to the emitting building.► This paper has investigated the dispersion of a pollutant emitted from a roof stack in a two-building configuration. ► The effect of stack height and pollutant exhaust velocity on the fresh-air-intake locations has been examined. ► It was found that omitting the upstream building can lead to major design errors regarding the fresh-air-intake locations. ► Increasing the stack height has an effect that is similar to increasing the pollutant exhaust velocity. ► The nature of this effect depends upon the wall of the building under consideration.
Keywords: Computational fluid dynamics (CFD); Atmospheric boundary layer (ABL); Pollutant dispersion; Pollutant exhaust velocity; Stack height; Turbulence model
Leaf saturation isothermal remanent magnetization (SIRM) as a proxy for particulate matter monitoring: Inter-species differences and in-season variation by F. Kardel; K. Wuyts; B.A. Maher; R. Hansard; R. Samson (pp. 5164-5171).
In recent studies, the saturation isothermal remanent magnetization (SIRM) of leaves has been used for monitoring of atmospheric particulate matter. This study examined leaf SIRM of tree species with different leaf surface characteristics in the urban environment of Gent (Belgium). Leaf SIRM was measured from co-located trees of Carpinus betulus (with ‘hairy’ leaves) and Tilia sp. (‘non-hairy’ leaves) at locations with contrasting traffic density (and particulate pollution level). The measurements were conducted twice during the growing season (June and September 2009). The highest SIRM values were observed for C. betulus, and the lowest for the non-hairy Tilia sp. leaves. The SIRM was significantly higher in locations with high traffic density and in September. Differences between species were independent of pollution level and sampling time, except between hairy and non-hairy Tilia sp. Monthly measurements of leaf SIRM on Tilia platyphyllos and C. betulus trees revealed high in-season variation, which may be due to a combination of short and long-term leaf surface processes. It is concluded that the leaf SIRM, a proxy for particulate matter deposition, depends on leaf surface structure, leaf maturity, and particulate pollution level.► Leaf saturation isothermal remanent magnetization (SIRM) of urban co-located tree species were assessed. ► High correlation was observed between leaf SIRM values of co-located species. ► All species considered were able to indicate differences in urban habitat quality. ► Moreover, leaf SIRM showed large variation throughout the entire in-leaf season. ► We conclude that inter-species calibration is allowed in spatial sampling of SIRM.
Keywords: Biomonitoring; Habitat quality; Magnetic properties; SIRM; Particulate matter; Urban trees
Measurement of trace gases and organic compounds in the smoke plume from a wildfire in Penedono (central Portugal) by Ana Vicente; Célia Alves; Cristina Monteiro; Teresa Nunes; Fátima Mirante; Margarita Evtyugina; Mário Cerqueira; Casimiro Pio (pp. 5172-5182).
Gas and particulate fractions were measured simultaneously from a wildfire in Penedono, central Portugal, which occurred in summer 2009. The total volatile hydrocarbons (THC) and carbon oxides (CO2 and CO) collected in Tedlar bags were measured using automatic analysers with flame ionisation and non-dispersive infrared detectors, respectively. Carbonyls (formaldehyde and acetaldehyde) were sampled from the Tedlar bags in DNHP cartridges and analysed by high-performance liquid chromatography. Fine (PM2.5) and coarse (PM2.5-10) smoke particles were collected sequentially, on pre-fired quartz fibre filters, with a portable high-volume sampler. The detailed speciation of organic compounds in smoke samples was carried out by gas chromatography-mass spectrometry. The organic and elemental carbon content of particulate matter was analysed by a thermal-optical transmission technique. Average emission factors of 1.86 ± 0.80 and 0.063 ± 0.066 g kg−1 (dry basis) were obtained for acetaldehyde and formaldehyde, respectively. The THC, CO, CO2, PM2.5, PM10, OC and EC emission factors (g kg−1 fuel burned, dry basis) were 260 ± 88, 268 ± 92, 1200 ± 172, 37 ± 12.2, 40 ± 12.6, 21 ± 6.7 and 0.44 ± 0.21, respectively. The chromatographically resolved organics included n-alkanes, n-alkenes, n-alkanoic acids, n-di-acids, unsaturated fatty acids, phenolic compounds, ketones, steroids, di- and triterpenoids, PAHs, with retene as the major compound, oxygenated PAH and anhydrosugars.► OC/EC ratios increased with the intensity of the smouldering phase. ► A strong inverse correlation between acetaldehyde and MCE was obtained. ► Retene was the major PAH present in both fine and coarse particles. ► Among diterpenoids, abietic and pimaric acids were dominant compounds. ► Vanillin(phenolic) and levoglucosan(anhydrosugar) are major constituents of smoke.
Keywords: Wildfire; Organic compounds; PM; 2.5; PM; 2.5-10; Emission factors
Evaluation of C1–C13 carbonyl compounds by RRLC-UV in the atmosphere of Niterói City, Brazil by Soraya de M. Ochs; Flávio C. Albuquerque; M. Cecília G. Pontes Massa; Annibal D. Pereira Netto (pp. 5183-5190).
In this present work, the concentration of 31 carbonyl compounds (CC) were determined in the atmosphere of Niterói City, RJ, Brazil, between January 9th and 14th, 2010, in 7 periods of two hours in each day. Rapid Resolution Liquid Chromatography with UV detection of the corresponding hydrazones was employed. Formaldehyde, acetaldehyde and acetone were found to be the most abundant CC in all the 42 samples. Experimental data showed one period of maximum concentration of CC that occurred between 10:00 and 12:00 h, regardless of the day, with concentrations varying between 16.20 and 52.30 μg m−3. The ratios of the concentrations of acetaldehyde and formaldehyde were ≥1 in all periods and the mean ratio was 2.0. The results obtained were lower than those previously found in Rio de Janeiro City, indicating that Niterói is a less polluted area in terms of this criterion. This is a novel work related to the aspects that concern the determination of most CC in the atmosphere of Niterói City and medium size Brazilian cities.Display Omitted► Carbonyl compound as atmospheric contaminants. ► Concentrations depend on day period and emission. ► Evaluation showed variation of concentration in different time intervals and along the week. ► Predominance of formaldehyde and acetaldehyde related to Brazilian automotive fuels.
Keywords: Carbonyl compounds; Carbonyl-DNPH derivatives; Air pollution; Vehicular emission; Rapid resolution liquid chromatography
Development of driving cycles for motorcycles and light-duty vehicles in Vietnam by H.Y. Tong; H.D. Tung; W.T. Hung; H.V. Nguyen (pp. 5191-5199).
The Centre for Environmental Monitoring of the Vietnam Environment Administration in Hanoi launched a 2-year emissions monitoring program which aimed at determining the emission factors and emission inventories for two typical types of vehicle in Hanoi. To achieve these objectives, developing driving cycles representative of the local driving conditions are of essential tasks before any emission testing can be conducted. Therefore, this paper presents the results of the development of two driving cycles for a motorcycle and a light-duty vehicle (LDV) in Hanoi. On-road speed–time data were collected by two test vehicles along 10 routes in the urban areas of Hanoi. The collected data were analysed to characterise the typical driving patterns and characteristics. A unique driving cycle was therefore developed for each of the two types of vehicle for Hanoi (i.e. CEMDC and CECDC). The cycles were developed by a random selection process to match the overall summary statistics. The CEMDC and CECDC cycles are the first set of driving cycles developed for Hanoi which can be applied to the next stage of the program for emission testing to determine the emission factors for Hanoi as well as for government’s emission control testing.► Two driving cycles were developed for motorcycle and LDV in Hanoi. ► On-road speed–time data were collected along 10 routes in the urban areas of Hanoi. ► The developed cycles showed significant differences with other international cycles. ► The cycles can be applied to the next stage for determining Hanoi emission factors. ► The cycles can also be used as for government’s emissions control testing.
Keywords: Driving cycles; Vehicle driving patterns; Vehicle emissions; Fuel consumption; On-road data
Comparison of Lagrangian Process Analysis tools for Eulerian air quality models by Barron H. Henderson; Yosuke Kimura; Elena McDonald-Buller; David T. Allen; William Vizuete (pp. 5200-5211).
Air quality models (AQM) are used to understand the complex relationships between sources of air pollutants and ambient concentrations. Two new AQM diagnostic tools, the Lagrangian Process Analysis (LPA) tool and the Python-based Process Analysis (pyPA), have recently been created that allow users to track a plume within the AQM, and then calculate the chemical and physical process rates that occur within it. These two new process analysis tools perform their functions differently. The LPA in-model algorithm operates at the computational timestep of the AQM, and pyPA is a post-processor tool dependent on the temporal resolution of the AQM output, typically 1 h. This work compares process rates calculated by these tools, using as a case study the simulation of a rapidly evolving plume that resulted from an industrial hydrocarbon release. Releases from industrial sources are of regulatory significance in Houston and their accurate simulation of great importance. Results show that the largest differences in the outputs of the tools occur early in the life of the plume when it is rapidly expanding. During this time, the plume encounters NOx sources that significantly impact chemical and physical process rates that are not seen in the pyPA post-processing of hourly AQM output.► Two process analysis tools that track plumes within a grid model were compared. ► Both tools tracked a rapidly evolving plume resulting from an industrial release. ► Largest differences in results occur when plume is rapidly expanding. ► As the plume grew larger differences in results became indistinguishable. ► When air quality model output was reduced to 5 min results were nearly identical.
Keywords: Ozone; Environmental chemistry; Air quality model; Process analysis; Volatile organic carbon; Industrial release
Evaluation of vessel emissions in a lagoon area with ground based Multi axis DOAS measurements by Margherita Premuda; Samuele Masieri; Daniele Bortoli; Ivan Kostadinov; Andrea Petritoli; Giorgio Giovanelli (pp. 5212-5219).
The environmental impact of large vessel exhaust gases on port and coastal areas is a subject of great interest due both to increasing maritime traffic and the vicinity to highly populated urban zones. In lagoon cities the pollution from maritime traffic is greater than in other coastal areas. Therefore monitoring and evaluation of pollutants produced by ships navigating through the principal transport channels become necessary. In the case of Venice, the Giudecca Channel, crossing the city centre, is used both by urban maritime traffic and by large vessels docking in the port.In this work, the FRE–DOAS (Flow Rate Emission with Differential Optical Absorption Spectroscopy) methodology developed to evaluate gaseous pollutant flow rates from moving sources is presented. This methodology is applied to a set of spectral measurements performed with a Multi axis DOAS remote sensing system, allowing a determination of vessel emissions and evaluation of their impact on pollution in Venice.Two one-month measurement campaigns were carried out: from June 12 2007 to July 12 2007 and from September 12 2007 to October 12 2007. The individual flow rates released by large and medium-sized vessels and the total flow rate emissions due to the total traffic along the Giudecca Channel for every day with appropriate meteo conditions during the campaigns are estimated.The average daily mass of gas emitted by large and medium-sized ships during their passage through the Channel was evaluated as about 205 kg for SO2 and 284 kg for NO2. These values make up only about 30% of total daily traffic emission. These results are extremely interesting, because they demonstrate inequivocably the effectiveness of the proposed system for remote measurements, opening a new frontier in maritime traffic emission control in harbour areas or in those coastal zones subject to heavy maritime traffic. Moreover, the low values obtained for some large modern cruise ships indicate the use of Low Sulphur Fuels, even though these are not yet required by local regulations.► FRE–DOAS remote sensing method to measure gas flow rate with MAX-DOAS is proposed. ► The mathematical formulation of FRE–DOAS is widely explained. ► The method provided a measure of large ships impact along the main Venice artery. ► Its value was compared to the total traffic impact along the Giudecca Channel. ► The method, being an automatic one, can be used for control and inspective aims.
Keywords: Ship gas flux measurements; Marine pollution; Giudecca Channel gaseous pollution; MAX-DOASAbbreviations; BAT; Best Available Technology; CGT; Compensated Gross Tonnage; ECU; Electronic Control Unit; DOAS; Differential Optical Absorption Spectroscopy; FRE; Flow Rate Emission; HSF; High Sulphur Fuel; LSF; Low Sulphur Fuel; SODCAL; Scanning Optical Device Collecting Atmospheric Light; VPA; Venice Port Authority
Impact of height and shape of building roof on air quality in urban street canyons by Mohamed F. Yassin (pp. 5220-5229).
A building’s roof shape and roof height play an important role in determining pollutant concentrations from vehicle emissions and its complex flow patterns within urban street canyons. The impact of the roof shape and height on wind flow and dispersion of gaseous pollutants from vehicle exhaust within urban canyons were investigated numerically using a Computational Fluid Dynamics (CFD) model. Two-dimensional flow and dispersion of gaseous pollutants were analyzed using standard κ– ɛ turbulence model, which was numerically solved based on Reynolds Averaged Navier–Stokes (RANS) equations. The diffusion fields in the urban canyons were examined with three roof heights (Z H/ H = 0.17, 0.33 and 0.5) and five roof shapes: (1) flat-shaped roof, (2) slanted-shaped roof, (3) downwind wedge-shaped roof, (4) upwind wedge-shaped roof, and (5) trapezoid-shaped roof. The numerical model was validated against the wind tunnels results in order to optimize the turbulence model. The numerical simulations agreed reasonably with the wind tunnel results. The results obtained indicated that the pollutant concentration increased as the roof height decreases. It also decreased with the slanted and trapezoid-shaped roofs but increased with the flat-shaped roof. The pollutant concentration distributions simulated in the present work, indicated that the variability of the roof shapes and roof heights of the buildings are important factors for estimating air quality within urban canyons.► Study the impact of the roof-shape building and its height on dispersion in canyon. ► The wind velocity decreased as the roof height increases. ► The turbulent energy increased as the roof height increased with the four roof shapes. ► The pollutant concentration increased as the roof height decreases. ► The concentration decreased with the slanted and trapezoid-shaped roofs.
Keywords: Atmospheric turbulent; CFD model; Pollutant dispersion; Roof buildings; Roof height; Street canyon
A novel methodology for interpreting air quality measurements from urban streets using CFD modelling by Efisio Solazzo; Sotiris Vardoulakis; Xiaoming Cai (pp. 5230-5239).
In this study, a novel computational fluid dynamics (CFD) based methodology has been developed to interpret long-term averaged measurements of pollutant concentrations collected at roadside locations. The methodology is applied to the analysis of pollutant dispersion in Stratford Road (SR), a busy street canyon in Birmingham (UK), where a one-year sampling campaign was carried out between August 2005 and July 2006. Firstly, a number of dispersion scenarios are defined by combining sets of synoptic wind velocity and direction. Assuming neutral atmospheric stability, CFD simulations are conducted for all the scenarios, by applying the standard k-ɛ turbulence model, with the aim of creating a database of normalised pollutant concentrations at specific locations within the street. Modelled concentration for all wind scenarios were compared with hourly observed NOx data. In order to compare with long-term averaged measurements, a weighted average of the CFD-calculated concentration fields was derived, with the weighting coefficients being proportional to the frequency of each scenario observed during the examined period (either monthly or annually). In summary the methodology consists of (i) identifying the main dispersion scenarios for the street based on wind speed and directions data, (ii) creating a database of CFD-calculated concentration fields for the identified dispersion scenarios, and (iii) combining the CFD results based on the frequency of occurrence of each dispersion scenario during the examined period. The methodology has been applied to calculate monthly and annually averaged benzene concentration at several locations within the street canyon so that a direct comparison with observations could be made. The results of this study indicate that, within the simplifying assumption of non-buoyant flow, CFD modelling can aid understanding of long-term air quality measurements, and help assessing the representativeness of monitoring locations for population exposure studies.► We develop a method for routine use of CFD in street air quality assessment. ► Dispersion scenarios based on wind speed, directions and emission are identified. ► We create a database of CFD-calculated concentration for each dispersion scenarios. ► We combine the CFD concentration based on the frequency of each dispersion scenario. ► Results for Benzene show the advantage of CFD to interpret air quality measurements.
Keywords: Urban street canyons; CFD; Passive diffusion tubes; Roadside monitoring
Outdoor NO2 and benzene exposure in the INMA (Environment and Childhood) Asturias cohort (Spain) by Ana Fernández-Somoano; Marisa Estarlich; Ferran Ballester; Rosalía Fernández-Patier; Amelia Aguirre-Alfaro; Ma Dolores Herce-Garraleta; Adonina Tardón (pp. 5240-5246).
Air pollution exposure during pregnancy has been linked to a wide range of negative health effects. NO2, a traffic pollution marker, and benzene, an industrial pollution indicator, stand out among the types of air pollution linked to these effects. The aim of this work is to show the methodology used to assign exposure levels for both pollutants and preliminary reports in the INMA (Environment and Childhood) Asturias cohort in Spain. This cohort consists of 494 pregnant women and their children, who have been recruited and followed since 2004. Air pollution levels were measured at 67 points by means of passive samplers.The mean NO2 measured value was 21.2 μg m−3 (range 3.5 μg m−3 to 44.5 μg m−3), and the mean benzene value was 2.72 μg m−3 (range 0.18 μg m−3 to 9.17 μg m−3) at urban sampling points and 0.64 μg m−3 (range 0.04 μg m−3 to 2.62 μg m−3) in rural locations. The Pearson correlation coefficient among pollutants was 0.42.Land Use Regression models were built to predict exposure at the homes of pregnant women. Altitude, road distances and land use were part of the models. The percent of explained variance was 52% for NO2 and 73% for benzene in the urban zones. No residual autocorrelation was found.Predictions were corrected based on the Air Quality Network of the Principality of Asturias taking into account pregnancy seasonality. Exposure indicators were determined for each term and for the entire pregnancy for each woman. Values for urban locations were higher than those for rural and benzene estimations for 5% of the cohort women were above the European Union annual limit value. Air pollution exposure for the INMA-Asturias cohort clearly depends on the place of residence. In particular, benzene concentrations are remarkably high if an individual lives in an urban and industrial area, which is an issue of management intervention and regulatory concern. Exposure assessment for different pollutants will allow us to evaluate potential adverse effects in foetal and infant health caused by air pollution.► We assessed air pollution in a non-metropolitan area of the north of Spain. ► We show the methodology used and preliminary reports in a cohort of pregnant women. ► Air pollution estimates for the cohort clearly depended on the place of residence. ► Benzene levels are remarkably high if they lived in an urban and industrial area. ► Exposure assessment will allow us to evaluate possible negative health effects.
Keywords: Air pollution; Pregnancy; Personal exposure; Nitrogen dioxide; BenzeneAbbreviations; NO; 2; Nitrogen dioxide; INMA; Environmental and Childhood; WHO; World Health Organisation; IARC; International Agency for Research on Cancer; GIS; Geographical Information System; LUR; Land Use Regression; μg/m3; Micrograms per cubic meter; MDI; Daily Mean Intensity (number of vehicles per day); EPER; European Pollutant Emission Register; RPD; Relative Percent Differences