Atmospheric Environment (v.45, #39)
Editorial board (i).
Air quality progress in North American megacities: A review by David D. Parrish; Hanwant B. Singh; Luisa Molina; Sasha Madronich (7015-7025).
Air quality progress in the North American megacities of Los Angeles, New York, and Mexico City is reviewed, compared, and contrasted. Enormous progress made in North America over the last 5 decades provides a template for other megacities of the world, especially in developing countries, attempting to achieve rapid economic growth without compromising air quality. While the progress to date has been impressive, many challenges remain including the need to improve air quality while simultaneously mitigating climate change. The impact of pollutant emissions from megacities is felt long distances away from the local sources but no policy mechanisms currently exist to mitigate air quality impacts resulting from such pollution transport.► Air quality progress in three North American megacities is reviewed. ► Enormous progress has been made over the last 5 decades. ► Further progress is required to meet health-based standards. ► North American progress can provide a template for developing megacities. ► A remaining challenge is to improve air quality while mitigating climate change.
Keywords: Air quality; Megacities; Ozone; Particulate matter; Pollution;
Meteorological characteristics associated with PM2.5 air pollution in Cleveland, Ohio, during the 2009–2010 Cleveland Multiple Air Pollutants Study by Adam N. Pasch; Clinton P. MacDonald; Robert C. Gilliam; Charley A. Knoderer; Paul T. Roberts (7026-7035).
Cleveland, Akron, and Lorain, Ohio, exceed the National Ambient Air Quality Standards (NAAQS) for particles with a diameter less than 2.5 microns (PM2.5). The 2009–2010 Cleveland Multiple Air Pollutants Study (CMAPS) and analyses were conducted to characterize the sources and processes that contribute to high PM2.5 concentrations in the Cleveland area. The results are being used in high-resolution mesoscale chemical and meteorological modeling to protect public health. This paper summarizes the meteorological measurements collected during CMAPS and describes how three-dimensional meteorological processes influence surface PM2.5 concentrations. Mixing heights were higher, boundary layer winds were stronger, flow was southerly, and ventilation was greater on most episode days compared to non-episode days. While greater ventilation typically results in lower PM2.5 concentrations, in this case the greater ventilation coincided with the transport of regional pollution by southerly winds. Stagnation, or limited transport of air parcels, occurred on the remaining episode days and was associated with limited vertical mixing and light winds. These stagnation/limited dispersion events were associated with a weak lake breeze during the summer and slow-moving, large-scale high-pressure systems with weak surface pressure gradients, resulting in light winds during the winter.► Analyzed boundary-layer meteorology and air quality in Cleveland. ► Focused on data collected by a radar wind profiler and sodar. ► Determined that high PM2.5 conc. often occurred with high mixing heights and southerly transport. ► Determined processes important for modeling, used to design emissions control strategies.
Keywords: Radar wind profiler; Sodar; Pollutant transport; Meteorology;
Carbon dioxide emissions from international air freight by Oliver J.A. Howitt; Michael A. Carruthers; Inga J. Smith; Craig J. Rodger (7036-7045).
Greenhouse gas emissions from international air transport were excluded from reduction targets under the Kyoto Protocol, partly because of difficulties with quantifying and apportioning such emissions. Although there has been a great deal of recent research into calculating emissions from aeroplane operations globally, publicly available emissions factors for air freight emissions are scarce. This paper presents a methodology to calculate the amount of fuel burnt and the resulting CO2 emissions from New Zealand’s internationally air freighted imports and exports in 2007. This methodology could be applied to other nations and/or regions. Using data on fuel uplift, air freight and air craft movements, and assumptions on mean passenger loadings and the mass of passengers and air freight, CO2 emissions factors of 0.82 kg CO2 per t-km and 0.69 kg CO2 per t-km for short-haul and long-haul journeys, respectively, were calculated. The total amount of fuel consumed for the international air transport of New Zealand’s imports and exports was calculated to be 0.21 Mt and 0.17 Mt respectively, with corresponding CO2 emissions of 0.67 Mt and 0.53 Mt.► Methodology to calculate CO2 emissions from international air freight is presented. ► Representative data on fuel uplifts were used in the calculations. ► EFs of 0.82 kg CO2 per t-km and 0.69 kg CO2 per t-km for short- and long-haul journeys. ► Total CO2 emissions from air freighting NZ’s 2007 imports and exports was 1.2 Mt. ► Emissions factors (EFs) derived are likely to be applicable to other nations.
Keywords: International air freight; Carbon dioxide emissions; Greenhouse gas emissions; New Zealand trade; Aeroplane passenger emissions; Aeroplane emission factors;
Non-methane volatile organic compound emission inventories in Beijing during Olympic Games 2008 by Junhua Su; Min Shao; Sihua Lu; Yangyang Xie (7046-7052).
Non-methane volatile organic compounds (NMVOCs) play important roles in ground-level ozone and secondary organic aerosol (SOA) formation. To evaluate the effectiveness of air quality control measures in Beijing in 2008, NMVOC emission inventories were compiled for June, July, August, and September with emission factors and updated activity data. Total NMVOC emissions were 22.6, 20.2, 14.9, and 14.6 Gg in June, July, August, and September, respectively. Anthropogenic NMVOC emissions were 45% lower in August than June; vehicles, solvent utilization, industrial processing, and miscellaneous sources declined by 66, 48, 15, and 75%, respectively. Anthropogenic NMVOC emissions increased in September compared with August. NMVOC emissions from petroleum storage and transport varied little during these months because of the installation of low-fugitive facilities. Reduced emissions from vehicles, industrial processing, and petroleum storage and transport contributed to the total anthropogenic reduction. Inventory uncertainties were evaluated to be [−51%, +126%], [−56%, +146%], [−58%, +161%], and [−52%, +133%] in June, July, August, and September, respectively, at the 95% confidence level.► The variations of NMVOCs emissions during summer 2008 in Beijing city were estimated. ► The yellow-label vehicles were the most important fleet in vehicular emissions. ► The biogenic emissions should not be ignored in the summer. ► The emissions were consistent with ambient concentration based results.
Keywords: NMVOCs; Emission factor; Control measures;
Recent evidence concerning higher NO x emissions from passenger cars and light duty vehicles by David C. Carslaw; Sean D. Beevers; James E. Tate; Emily J. Westmoreland; Martin L. Williams (7053-7063).
Ambient trends in nitrogen oxides (NO x ) and nitrogen dioxide (NO2) for many air pollution monitoring sites in European cities have stabilised in recent years. The lack of a decrease in the concentration of NO x and in particular NO2 is of concern given European air quality standards are set in law. The lack of decrease in the concentration of NO x and NO2 is also in clear disagreement with emission inventory estimates and projections. This work undertakes a comprehensive analysis of recent vehicle emissions remote sensing data from seven urban locations across the UK. The large sample size of 84,269 vehicles was carefully cross-referenced to a detailed and comprehensive database of vehicle information. We find that there are significant discrepancies between current UK/European estimates of NO x emissions and those derived from the remote sensing data for several important classes of vehicle. In the case of light duty diesel vehicles it is found that NO x emissions have changed little over 20 years or so over a period when the proportion of directly emitted NO2 has increased substantially. For diesel cars it is found that absolute emissions of NO x are higher across all legislative classes than suggested by UK and other European emission inventories. Moreover, the analysis shows that more recent technology diesel cars (Euro 3–5) have clear increasing NO x emissions as a function of Vehicle Specific Power, which is absent for older technology vehicles. Under higher engine loads, these newer model diesel cars have a NO x /CO2 ratio twice that of older model cars, which may be related to the increased use of turbo-charging. Current emissions of NO x from early technology catalyst-equipped petrol cars (Euro 1/2) were also found to be higher than emission inventory estimates – and comparable with NO x emissions from diesel cars. For heavy duty vehicles, it is found that NO x emissions were relatively stable until the introduction of Euro IV technology when emissions decreased by about 30%. The more limited data available for urban buses shows that there has been little change in NO x emissions from Euro I to Euro IV. There is general much better consistency across the different estimates of heavy duty vehicle NO x emissions than for light duty vehicles.► Trends in ambient NO x concentrations have tended to stabilise in recent years. ► Little change in light duty vehicle NO x emissions over 20 years or so. ► Increased diesel car power demand leads to increased NO x for newer vehicles. ► Older catalyst-equipped vehicles emit more NO x than previously thought. ► Important implications at a European level for meeting NO2 limits.
Keywords: Vehicle emissions; Remote sensing; Primary NO2; Emissions inventory; Ambient trends;
Residential indoor and outdoor coarse particles and associated endotoxin exposures by Amanda J. Wheeler; Nina A. Dobbin; Ninon Lyrette; Lance Wallace; Mark Foto; Ranjeeta Mallick; Jill Kearney; Keith Van Ryswyk; Nicolas L. Gilbert; Ian Harrison; Kathleen Rispler; Marie-Eve Héroux (7064-7071).
There is a growing body of evidence demonstrating that coarse particles (PM10– 2.5) have detrimental impacts upon health, especially for respiratory effects. There are limited data available for indoor residential exposures. Some data exist regarding the composition of this PM size fraction with emphasis on crustal elements and biological components. This study includes data from 146 homes sampled in Regina, Saskatchewan (SK) where 5-day integrated concurrent monitoring of indoor and outdoor coarse particles was conducted during the winter and summer of 2007. The coarse particle filters were subsequently analysed for endotoxin content to determine the contribution of this compound. Winter indoor geometric mean concentrations of coarse particles exceeded outdoor concentrations (3.73 μg m−3 vs 2.49 μg m−3; paired t-test p < 0.0001); however the reverse was found in summer (4.34 μg m−3 vs 8.82 μg m−3; paired t-test p < 0.0001). Linear regression indicated that winter predictors of indoor coarse particles were outdoor coarse particles, ventilation and presence of at least two or more occupants. During the summer, increased use of central air conditioning was associated with reduced coarse particles, while smoking and the presence of two or more occupants resulted in increased coarse particles. Endotoxin concentrations (EU μg−1) were lower indoors than outdoors in both seasons. Spatial variability of ambient coarse particles was assessed to determine the suitability of using a single monitoring station within a city to estimate exposure. The coefficients of variation between homes sampled simultaneously and the central monitoring station were calculated (median COV in summer = 15% and winter = 24%) and showed significant variability by week, especially during the summer months, suggesting a single site may be insufficient for characterizing exposure. Future studies should consider daily measurements per home to understand shorter term exposures and day to day variability of these pollutants.► Winter indoor concentrations of coarse PM exceeded outdoor concentrations. ► Endotoxin concentrations were lower indoors than outdoors in both seasons. ► Spatial variability of ambient coarse PM is higher in summer than winter.
Keywords: Coarse particles; Endotoxin; Indoor air quality; Spatial variability;
Comparative assessment of GIS-based methods and metrics for estimating long-term exposures to air pollution by John Gulliver; Kees de Hoogh; Daniela Fecht; Danielle Vienneau; David Briggs (7072-7080).
The development of geographical information system techniques has opened up a wide array of methods for air pollution exposure assessment. The extent to which these provide reliable estimates of air pollution concentrations is nevertheless not clearly established. Nor is it clear which methods or metrics should be preferred in epidemiological studies. This paper compares the performance of ten different methods and metrics in terms of their ability to predict mean annual PM10 concentrations across 52 monitoring sites in London, UK. Metrics analysed include indicators (distance to nearest road, traffic volume on nearest road, heavy duty vehicle (HDV) volume on nearest road, road density within 150 m, traffic volume within 150 m and HDV volume within 150 m) and four modelling approaches: based on the nearest monitoring site, kriging, dispersion modelling and land use regression (LUR). Measures were computed in a GIS, and resulting metrics calibrated and validated against monitoring data using a form of grouped jack-knife analysis. The results show that PM10 concentrations across London show little spatial variation. As a consequence, most methods can predict the average without serious bias. Few of the approaches, however, show good correlations with monitored PM10 concentrations, and most predict no better than a simple classification based on site type. Only land use regression reaches acceptable levels of correlation (R 2 = 0.47), though this can be improved by also including information on site type. This might therefore be taken as a recommended approach in many studies, though care is needed in developing meaningful land use regression models, and like any method they need to be validated against local data before their application as part of epidemiological studies.► Performance of ten air pollution metrics/methods for exposure assessment was compared. ► Simple extrapolation of monitoring data from the nearest site was the least reliable approach. ► Most simple indicators based on road density or traffic volumes performed poorly. ► Land use regression models performed significantly better than all other methods. ► Information on site type improves performance of dispersion and land use regression models.
Keywords: Exposure assessment; Air quality; Dispersion modelling; Particles; GIS; Land use regression;
A study of acidity on PM2.5 in Hong Kong using online ionic chemical composition measurements by Jian Xue; Alexis K.H. Lau; Jian Zhen Yu (7081-7088).
Particle in-situ pH (pH IS), defined as pH of the aqueous phase on aerosols, is an important factor in influencing aerosol-phase chemistry and uptake of gaseous species by particles. In this study, a continuous system, Particle-into-Liquid System (PILS) coupled with two ion chromatographs, was used to obtain PM2.5 ionic chemical composition at a time resolution of 30 min at a suburban site in Hong Kong under three different synoptic conditions. The chemical composition data and meteorological parameters (e.g., temperature, relative humidity (RH)) are input into Aerosol Inorganic Model (AIM-III) for estimation of in-situ pH through calculation of H+ amount and aerosol liquid water content (LWC). The particle pH IS ranged from −1.87 to 3.12, with an average at −0.03, indicating the PM2.5 particles in Hong Kong are highly acidic. Unlike particle strong acidity, which was dominated by sulfate concentration, the amount of aerosol liquid water content could significantly influence in-situ particle acidity. Principal factor analysis has identified the equivalent concentration ratio between cations and anions (i.e., R +/−) and RH to be the two most important factors influencing the particle pH IS. pH IS under different synoptic conditions in this study could be well approximated by a single linear regression equation (slope: 0.95, R 2: 0.93), i.e., pH IS = 4.94 R +/− + 3.11 RH − 5.70. Such an empirical equation provides a convenient mean in estimating particle in-situ acidity for assessing the role of acid-catalyzed aerosol reactions.► Particle in-situ pH could be estimated by a single linear regression equation of two parameters. ► In-situ pH estimation indicates fine particles are highly acidic in Hong Kong. ► The diurnal variation in relative humidity could drive particle acidity to be higher during the day.
Keywords: Particle acidity; Ionic chemical composition; Acid-catalyzed reactions; PILS-IC;
The effect of water presence on the photocatalytic oxidation of benzene, toluene, ethylbenzene and m-xylene in the gas-phase by Christos A. Korologos; Constantine J. Philippopoulos; Stavros G. Poulopoulos (7089-7095).
In the present work, the gas–solid heterogeneous photocatalytic oxidation of benzene, toluene, ethylbenzene and m-xylene (BTEX) over UV-irradiated titanium dioxide was studied in an annular reactor operated in the CSTR (continuous stirred-tank reactor) mode. GC-FID and GC-MS were used for analysing reactor inlet and outlet streams. Initial BTEX concentrations were in the low parts per million (ppmv) range, whereas the water concentration was in the range of 0–35,230 ppmv and the residence time varied from 50 to 210 s. The effect of water addition on the photocatalytic process showed strong dependence on the type of the BTEX and the water vapour concentration. The increase in residence time resulted in a considerable increase in the conversion achieved for all compounds and experimental conditions. There was a clear interaction between residence time and water presence regarding the effect on conversions achieved. It was established that conversions over 95% could be achieved by adjusting appropriately the experimental conditions and especially the water concentration in the reactor. In all cases, no by-products were detected above the detection limit and carbon dioxide was the only compound detected. Finally, various Langmuir-Hinshelwood kinetic models have been tested in the analysis of the experimental data obtained. The kinetic data obtained confirmed that water had an active participation in the photocatalytic reactions of benzene, toluene, ethylbenzene and m-xylene since the model involving reaction of BTEX and water adsorbed on different active sites yielded the most successful fitting to the experimental results for the first three compounds, whereas the kinetic model based on the assumption that reaction between VOC and water dissociatively adsorbed on the photocatalyst takes place was the most appropriate in the case of m-xylene.► Photo-oxidation of BTEX over UV-irradiated TiO2 in annular reactor and CSTR mode. ► The effect of water vapour depended on pollutant type and water concentration. ► Increasing residence time resulted in significant increase in conversions achieved. ► No by-products were detected and carbon dioxide was the only compound formed. ► Kinetic analysis was conducted applying five Langmuir-Hinshelwood models.
Keywords: Titanium dioxide; BTEX; Langmuir-Hinshelwood kinetics;
Characterization of trace elements and ions in PM10 and PM2.5 emitted from animal confinement buildings by Xufei Yang; Xinlei Wang; Yuanhui Zhang; Jongmin Lee; Jingwei Su; Richard S. Gates (7096-7104).
Chemical characterization of PM emanating from animal confinement buildings can provide essential information for receptor modeling-based PM source apportionment as well as health effects assessment. In this study, PM10 and PM2.5 samples were collected from twelve swine (farrowing, gestation, weaning, and finishing) and six poultry (layer hen and tom turkey) confinement buildings in the U.S. Midwest and their inorganic composition, in terms of trace elements and ions, was investigated. A total of 23 species were identified and quantified, including Al, B, Ba, Ca, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, S, Si, Sr, Ti, Zn, Cl−, NO3 −, SO4 2− and NH4 +. The total mass fraction of identified species was typically less than 16%. NH4 + was detected in low contents (<1% wt.) in collected PM samples, suggesting that the majority of NH3–N emissions were in gas form and the formation of NH4 +-containing secondary aerosols is insignificant in animal confinement buildings. Several multivariate analysis tools prevalent in ecology research were implemented for examining variability in PM inorganic compositions. Results showed that PM inorganic composition varied significantly with animal building type. Seasons had no significant effect on PM10 and a significant but weak effect on PM2.5 inorganic compositions. Compared to PM10 samples, PM2.5 samples from different types of animal confinement buildings were more similar in inorganic composition.► Ammonium ions were present in low content (<1% wt.) in collected PM. ► PM inorganic composition varied significantly with animal building type. ► Seasons had no significant effect on PM10 inorganic composition. ► Seasons had a significant but weak effect on PM2.5 inorganic composition. ► PM2.5 from different building types had more similar composition than PM10.
Keywords: PM10; PM2.5; Inorganic composition; Elements; Ions; Animal confinement building; Multivariate analysis;
Seasonal variation in the biogenic secondary organic aerosol tracer cis-pinonic acid: Enhancement due to emissions from regional and local biomass burning by Yu Cheng; Jeffrey R. Brook; Shao-Meng Li; Amy Leithead (7105-7112).
Studies have demonstrated that cis-pinonic acid (CPA) is an important product from the oxidation of pinenes with ozone. CPA has been measured on aerosols and is used as an aging indicator for secondary organic aerosols (SOA). CPA levels and formation in urban aerosols and its annual variability, however, are still poorly understood. Here, we present monthly CPA average concentrations on aerosols in Toronto, Ontario, Canada based on a two-year-period: 2000–2001. They displayed a seasonal pattern associated with temperature and ozone (O3) plus nitrogen dioxide (NO2) reflecting the influence these have on emissions of pinenes from forests and their atmospheric oxidation, respectively. However, in Toronto some months with higher CPA concentrations, especially in the winter, were inconsistent with the seasonality of temperature or/and O3 + NO2 levels. Instead these deviations were associated with increases in wood burning tracers such as dehydroabietic acid (DHAA) and sugars. Similar features were observed during a two-week-period comparing day and nighttime CPA concentrations in the Lower Fraser Valley (LFV) of British Columbia, Canada, in that the CPA concentrations clearly varied diurnally with temperature and O3 + NO2 on some days, but also showed a significant correspondence with variations in the wood burning tracer concentrations, such as levoglucosan. These findings demonstrate that CPA formation is strongly impacted by wood burning activity.► Monthly and daily variation of cis-pinonic acid (CPA) in aerosols was examined. ► CPA displayed a seasonal and diurnal pattern. ► CPA concentrations were associated with temperature and O3 plus NO2. ► Enhanced CPA levels were associated with biomass burning tracers. ► CPA enhancement due to emissions from regional and local biomass burning.
Keywords: cis-pinonic acid; Sugars; Aerosols; Biogenic SOA tracer; Biomass burning;
Digital photographic method to quantify black carbon in ambient aerosols by Ke Du; Yang Wang; Bing Chen; Kai Wang; Jinsheng Chen; Fuwang Zhang (7113-7120).
A digital photography based method, Digital Optical Method for Black Carbon (DOM-BC), was developed to quantify the concentration of aerosol black carbon (BC). In this method, a measured volume of ambient air passed through an aerosol sampler, and the aerosol particles were collected onto a quartz fiber filter. Digital pictures of the filter were taken, and then analyzed to determine the optical attenuation (ATN) of the particle layer on the filter. The ATN was related to the mass loading of BC, in μg BC per cm2 of filter area, by performing calibration against thermal–optical analysis (TOA). The average aerosol BC concentration was then calculated with known BC loading, sampling time, and filter area.Method calibration was carried out using one set of samples collected in Xiamen. The results showed that the BC loading was linearly related to the ATN of the particle layer when the ATN was lower than 150. When the ATN increased beyond 200, an exponential correlation was observed. This method was validated by analyzing the samples collected in Xiamen from 06/2009 to 01/2011. For all the samples taken in Xiamen, the average relative error was <10.7% when comparing with the TOA measurements. DOM-BC was further evaluated by conducting statistical tests. Uncertainty analysis indicated an overall uncertainty of 7% for this method.► A new method was developed to quantify black carbon (BC) concentration using a commercial-off-the-shelf digital camera. ► Transparency based attenuation (ATN) was quantified with the digital photos of particle filter and blank filter. ► The relationship between ATN and BC loading was found to be linear for ATN < 150 and exponential for ATN > 200. ► This method is easy-to-operate, fast through-put, and cost efficient comparing to traditional thermal or optical methods.
Keywords: Black carbon; Digital photography; Aerosol; Light attenuation;
Air pollutants and morbidity of cardiopulmonary diseases in a semi-urban Greek peninsula by Eirini G. Kalantzi; Demosthenes Makris; Marie Noelle Duquenne; Stamatina Kaklamani; Herricos Stapountzis; Konstantinos I. Gourgoulianis (7121-7126).
To access the relationship between the frequency of hospitalizations due to respiratory and cardiovascular diseases and air pollution.Time series study during a seven year period (2001–2007) in a semi-urban tourist Greek peninsula. Data were collected from the computerized database of Volos General Hospital and included on a daily basis all emergency admissions of adults (>14 years old) which required hospitalization due to respiratory or cardiovascular problems. Daily concentrations of ambient pollutants [particulate matter with aerodynamic diameter less than 10 mm (PM10), carbon monoxide (CO), sulfur dioxide (SO2), nitrogen oxides (NO, NO2, NOX) and ozone (O3)] were obtained from three monitoring stations. The impact of air pollutants on morbidity was studied through time series analysis. The effects of time trend, season, and other cyclical factors, temperature, and humidity were accounted for. Autocorrelation and overdispersion were corrected.There were significant associations between hospitalizations and all indicators of air pollution. Daily elevations in the concentrations of PM10, NO, CO and O3 increased significantly the number of hospitalizations for respiratory/cardiovascular causes both on the same day and at the next day (p < 0.05). Combined increase of CO and O3 and of PM10 and CO was associated with even higher hospitalization rates.Our findings suggest a significant relationship between morbidity burden of respiratory and cardiovascular diseases and the levels of air pollution; these results underline that reinforcement of measures which target to control ambient pollution, is necessary.► Environmental study in a Greek semi-urban peninsula with tourist activity. ► Elevations in PM10, NO and CO increased respiratory and cardiovascular morbidity. ► Combined increase in levels of CO and O3 causes the greatest impact in admissions.
Keywords: Air pollution; Greece; Atmospheric; PM10; CO; SO2; NO; NO2; NOX; O3; Morbidity;
The heterogeneous ozonation of pesticides adsorbed on mineral particles: Validation of the experimental setup with trifluralin by Maryline Pflieger; Irena Grgić; Zoran Kitanovski; Laura Nieto; Henri Wortham (7127-7134).
In this study, an experimental device adapted for the investigation of organic compounds with both low and high reactivity towards gaseous ozone is presented. The heterogeneous reactions were performed in a round-bottom flask connected to a rotary evaporator specially adapted to this purpose. The extract of the remaining compound on silica particles was filtered and analysed using High Pressure Liquid Chromatography with a UV detector. The kinetic was determined by following the consumption of the organic (dark, T = 26 °C, RH < 1%). The herbicide trifluralin was chosen as a test compound since its heterogeneous ozonation has already been studied in a previous work (). The obtained kinetic data was fitted by both the modified Langmuir–Hinshelwood ( k max ′ = 4.6 (±7.4) × 10−4 s−1 and K O3 = 2.4 (±4.2) × 10−16 cm3) and Eley–Rideal (k O3/ER = 1.05 (±0.06) × 10−19 cm3 molecule−1 s−1) patterns, even though this latter seems to be the most consistent model. These results confirmed that the heterogeneous reactivity of trifluralin with O3 is very slow in the atmosphere and lead to the formation of adsorbed degradation products. Moreover, our kinetic constants are in reasonable agreement (factor 3) to the one obtained in the previous study using flow tubes. Finally, our simple alternative device offers the possibility of increasing the number of heterogeneous process investigations, which constitutes an absolute necessity for issues of the environmental fate of pesticides.► Little is known about the atmospheric heterogeneous processes of pesticides. ► A simple alternative experimental setup for studying heterogeneous kinetics is presented. ► Our device yielded comparable results to those obtained in flow tubes. ► The Langmuir–Rideal pattern seems appropriate to describe numerous atmospheric heterogeneous reactions. ► Trifluralin is slowly degraded by atmospheric heterogeneous ozonation.
Keywords: Atmosphere; Heterogeneous reactivity; Ozone; Pesticides; Semi-volatile organic compounds; Silica;
Methane emission estimation from landfills in Delhi: A comparative assessment of different methodologies by Monojit Chakraborty; Chhemendra Sharma; Jitendra Pandey; Nahar Singh; Prabhat K. Gupta (7135-7142).
Landfills are important anthropogenic sources of methane (CH4) emission especially in fast urbanizing countries. This paper presents the CH4 emission estimations carried out using the in-situ CH4 measurements, IPCC 1996 Default methodology (DM), Modified Triangular Method (MTM) and First Order Decay (FOD) method for the three landfills currently operational in the capital city Delhi of India. The in-situ methodology has yielded the landfills specific methane emission factors (EFs). The annual average methane emission rates from three landfills namely, Ghazipur (GL), Bhalswa (BL) and Okhla (OL) are 14.6, 23.6 & 7.5 Gg y−1 by DM; 13.3, 10.6 & 7.2 Gg y−1 by the FOD; 17.0, 13.7 and 10.7 Gg y−1 by the MTM; and 4.6, 4.2 and 1.4 Gg y−1 by the in-situ measurement method respectively. The CH4 EFs have been found to be 9.7 ± 2.6, 5.5 ± 1.6 and 5.5 ± 1.7 g kg−1 of waste respectively for the GL, BL and OL landfills in Delhi. The study reveals that in-situ methodology seems to provide better representative emission estimation compared to other methods. The FOD method also yields comparable results with that of in-situ methodology in cases where good waste composition data is available.► Methane emission from landfill sites show large spatial and temporal variability. ► Development of landfill specific methane emission factor reduces uncertainties in estimation. ► Different methodologies for emission estimation result in different values. ► Usefulness of FOD method depends upon the quality of waste composition data.
Keywords: Greenhouse gases; Municipal solid waste; Waste management; Emission factors; Inventories;
Ozone air quality measurement requirements for a geostationary satellite mission by Peter Zoogman; Daniel J. Jacob; Kelly Chance; Lin Zhang; Philippe Le Sager; Arlene M. Fiore; Annmarie Eldering; Xiong Liu; Vijay Natraj; Susan S. Kulawik (7143-7150).
We conduct an Observing System Simulation Experiment (OSSE) to test the ability of geostationary satellite measurements of ozone in different spectral regions to constrain surface ozone concentrations through data assimilation. Our purpose is to define instrument requirements for the NASA GEO-CAPE geostationary air quality mission over North America. We consider instruments using different spectral combinations of UV (290–340 nm), Vis (560–620 nm), and thermal IR (TIR, 9.6 μm). Hourly ozone data from the MOZART global 3-D chemical transport model (CTM) are taken as the “true” atmosphere to be sampled by the instruments for July 2001. The resulting synthetic data are assimilated in the GEOS-Chem CTM using a Kalman filter. The MOZART and GEOS-Chem CTMs have independent heritages and use different assimilated meteorological data sets for the same period, making for an objective OSSE. We show that hourly observations of ozone from geostationary orbit improve the assimilation considerably relative to daily observation from low earth orbit, and that broad observation over the ocean is unnecessary if the objective is to constrain surface ozone distribution over land. We also show that there is little propagation of ozone information from the free troposphere to the surface, so that instrument sensitivity in the boundary layer is essential. UV + Vis and UV + TIR spectral combinations improve greatly the information on surface ozone relative to UV alone. UV + TIR is preferable under high-sensitivity conditions with strong thermal contrast at the surface, but UV + Vis is preferable under low-sensitivity conditions. Assimilation of data from a UV + Vis + TIR instrument reduces the GEOS-Chem error for surface ozone by a factor of two. Observation in the TIR is critical to obtain ozone information in the upper troposphere relevant to climate forcing.► We simulate satellite instrument configurations observing ozone air quality. ► Most of ozone pollution is produced within the boundary layer. ► Geostationary observations are much more effective than low earth orbit observations. ► A multispectral instrument is necessary for required vertical sensitivity. ► Thermal infrared channel is critical to quantify climate forcing.
Keywords: Air quality; Ozone; Kalman filter; Assimilation; Remote sensing;
Multi-spectral sensitivity studies for the retrieval of tropospheric and lowermost tropospheric ozone from simulated clear-sky GEO-CAPE measurements by Vijay Natraj; Xiong Liu; Susan Kulawik; Kelly Chance; Robert Chatfield; David P. Edwards; Annmarie Eldering; Gene Francis; Thomas Kurosu; Kenneth Pickering; Robert Spurr; Helen Worden (7151-7165).
One of the important science requirements of the Geostationary Coastal and Air Pollution Events (GEO-CAPE) mission is to be able to measure ozone with two degrees of freedom in the troposphere and sensitivity in the lowest 2 km (lowermost troposphere, LMT), in order to characterize air quality and boundary layer transport of pollution. Currently available remote sensing techniques utilize backscattered solar ultraviolet (UV) radiances or thermal infrared (TIR) emissions to perform ozone retrievals. However, in the TIR, measurement sensitivity to the LMT requires high thermal contrast between the Earth’s surface and the near-surface (tens to hundreds of meters above surface) atmosphere, while in the UV, the measurement sensitivity to the LMT is low because of Rayleigh scattering. In this paper, we explore the feasibility of using multi-spectral intensity measurements in the UV, visible (VIS), mid infrared (MIR) and TIR, and polarization measurements in the UV/VIS, to improve tropospheric and lowermost tropospheric ozone retrievals.Simulations for 16 cloud and aerosol free atmospheric profiles spanning a range of ozone mixing ratios indicate that adding VIS measurements to UV measurements significantly enhances the sensitivity to lowermost tropospheric ozone, but only makes a slight improvement to the total degrees of freedom for signal (DFS). On the other hand, the combination of UV and TIR significantly improves the total DFS as well as the lowermost tropospheric DFS.The analysis presented here is a necessary and important first step for defining spectral regions that can meet the GEO-CAPE measurement requirements, and subsequently, the requirements for instrumentation. In this work, the principle of multi-spectral retrievals has been extended from previously published literature and we show that the UV + VIS, UV + TIR and UV + VIS + TIR combinations have the potential to meet the GEO-CAPE measurement requirements for tropospheric ozone. Our analysis includes errors from water and surface properties; further analysis is needed to include temperature, additional gas interferents, clouds, aerosols and more realistic surface properties. These simulations must be run on a much larger dataset, followed by OSSEs (Observing System Simulation Experiments), where simulated retrievals are assimilated into chemical-transport models, to quantitatively assess the impact of the proposed measurements for constraining the spatiotemporal distribution of ozone in the LMT for basic science studies and applications such as air quality forecasts.► We use multi-spectral retrievals to retrieve lowermost tropospheric ozone. ► Simulations are performed for 16 cloud- and aerosol free atmospheric profiles. ► Combination of visible (VIS) and ultraviolet (UV) measurements has good sensitivity to lowermost tropospheric ozone. ► Combination of UV and thermal infrared (TIR) measurements significantly improves total and lowermost tropospheric degrees of freedom for signal (DFS).
Keywords: Multi-spectral; Ozone; Retrieval; Sensitivity; Troposphere; Geostationary platform; GEO-CAPE;
Quantification of ebullitive and diffusive methane release to atmosphere from a water storage by Alistair Grinham; Matthew Dunbabin; Deborah Gale; James Udy (7166-7173).
Accurately quantifying total freshwater storage methane release to atmosphere requires the spatial–temporal measurement of both diffusive and ebullitive emissions. Existing floating chamber techniques provide localised assessment of methane flux, however, significant errors can arise when weighting and extrapolation to the entire storage, particularly when ebullition is significant. An improved technique has been developed that compliments traditional chamber based experiments to quantify the storage-scale release of methane gas to atmosphere through ebullition using the measurements from an Optical Methane Detector (OMD) and a robotic boat. This provides a conservative estimate of the methane emission rate from ebullition along with the bubble volume distribution. It also georeferences the area of ebullition activity across entire storages at short temporal scales. An assessment on Little Nerang Dam in Queensland, Australia, demonstrated whole storage methane release significantly differed spatially and throughout the day. Total methane emission estimates showed a potential 32-fold variation in whole-of-dam rates depending on the measurement and extrapolation method and time of day used. The combined chamber and OMD technique showed that 1.8–7.0% of the surface area of Little Nerang Dam is accounting for up to 97% of total methane release to atmosphere throughout the day. Additionally, over 95% of detectable ebullition occurred in depths less than 12 m during the day and 6 m at night. This difference in spatial and temporal methane release rate distribution highlights the need to monitor significant regions of, if not the entire, water storage in order to provide an accurate estimate of ebullition rates and their contribution to annual methane emissions.► Novel technique to quantify ebullitive methane release across water storages. ► Approach operates in real-time and is scalable to any size monitoring zone. ► 1.8–7.0% of the water storage accounted for up to 97% of total methane release. ► Detected methane emissions greater than 22 000 mg m−2 d−1 in areas of ebullition. ► Failure to quantify ebullition can lead to erroneous methane release estimates.
Keywords: Methane; Ebullition; Australia; Sub-tropical; Freshwater; Storage;
Atmospheric dispersion of an elevated release in a rural environment: Comparison between field SF6 tracer measurements and computations of Briggs and ADMS models by O. Connan; C. Leroy; F. Derkx; D. Maro; D. Hébert; P. Roupsard; M. Rozet (7174-7183).
The French Institute for Radiological Protection and Nuclear Safety (IRSN), in collaboration with VEOLIA (French environmental services company), conducted experimental campaigns to study atmospheric dispersion around an Energy Recycling Unit (EUR). The objectives were to study dispersion for an elevated release in a rural environment and to compare results with those of models. The atmospheric dispersion was studied by SF6 tracer injection into a 40 m high stack. Maximum values of experimental Atmospheric Transfer Coefficients (ATCmax) and horizontal dispersion standard deviations (σ h) were compared to predictions from a first generation Briggs gaussian model as well as results from the latest generation ADMS 4.1 gaussian model.In neutral atmospheric conditions, the Briggs and ADMS models are in good agreement with experimental data in terms of ATC and σ h. In unstable condition, for σ h, both ADMS and Briggs models slightly overestimate the data for winter and summer conditions. In unstable conditions, ADMS and Briggs models overestimated ATCmax. The statistical evaluation of the models versus experimental data shows neither models ever meets all of the criteria for good performance. However, statistical evaluation indicates that the ADMS model is more suitable for neutral condition, and that the Briggs model is more reliable for summer unstable conditions.► 30 SF6 tracer experiment in rural environment with hot and high release. ► Comparison of experimental results with Briggs and ADMS models. ► In neutral atmospheric conditions, results of models are acceptable. ► In unstable conditions, results of models are more different from experimental data.
Keywords: Atmospheric dispersion; Elevated release; SF6 tracer release; Models; Briggs; ADMS;
Roadside and rooftop measurements of polycyclic aromatic hydrocarbons in PM2.5 in urban Guangzhou: Evaluation of vehicular and regional combustion source contributions by Bo Gao; Jian-Zhen Yu; Shu-Xian Li; Xiang Ding; Quan-Fu He; Xin-Ming Wang (7184-7191).
Concurrent sampling of PM2.5 aerosol at a roadside of heavy traffic (1.2 m above ground) and on a nearby rooftop (50 m above ground) was conducted at a same location in urban Guangzhou in September, October 2006 and January 2007. The samples were analyzed for eighteen polycyclic aromatic hydrocarbons (PAHs), together with major aerosol constituents and certain organic tracers for vehicular emissions (hopanes) and biomass burning (levoglucosan). Elemental carbon (EC) and hopanes were observed to be lower by 21–38% and 28–84%, respectively, at the rooftop than the roadside, confirming vehicular emissions as a significant local PM source. On the other hand, sulfate showed little vertical gradient, consistent with its secondary origin and its regional characteristics. The roadside-rooftop sample pairs have provided an opportunity in evaluating relative contributions of vehicular emissions and regional sources to ambient PAHs in this urban location. Concentrations of the total PAHs were ∼43% lower at rooftop in the September 2006 samples while they were at similar levels between rooftop and roadside in the October 2006 and January 2007 samples. Sources of PAHs were investigated through comparing ambient data of PAH isomer pairs and PAH/EC ratios with relevant source profiles including those of Guangzhou roadway tunnel emissions, rice straw/sugarcane leave combustion, and industrial coal combustion. The 4-ring PAHs such as pyrene and fluoranthene had a shift in their dominating source from vehicular emissions in September and October to regional combustion source in January. A few major 5- and 6-ring PAHs such as benzo[ghi]perylene and indeno[1,2,3-cd]pyrene were likely heavily influenced by regional biomass burning emissions in all three sampling months.Benzo(a)pyrene-equivalent carcinogenic potency (BaPeq) was calculated to evaluate the cancer risk of carcinogenic PAHs on the public. BaPeq levels in PM2.5 were significantly higher at the roadside than those at the rooftop in September; however, levels of BaPeq at the rooftop were drastically elevated and became comparable to those at the roadside in October and January due to regional sources dominating the carcinogenic PAHs. This suggests that it is important to control regional combustion sources to reduce air pollution-related health risk in urban Guangzhou.► Roadside and rooftop aerosol sample pairs were collected in urban Guangzhou. ► Source contributions of local traffic vs. regional pollution were evaluated. ► Biomass burning could be dominating regional carcinogenic PAH source. ► Controlling regional combustion sources lowers air pollution-related health risk.
Keywords: PAHs; Vehicular emissions; Regional; Elemental carbon; Guangzhou;
The effects of accumulated refractory particles and the peak inert mode temperature on semi-continuous organic carbon and elemental carbon measurements during the CAREBeijing 2006 campaign by Jinsang Jung; Young J. Kim; Kwang Yul Lee; Kimitaka Kawamura; Min Hu; Yutaka Kondo (7192-7200).
Two semi-continuous Sunset carbon analyzers, with different peak inert mode temperatures (615 and 740 °C), were simultaneously operated to measure fine particulate organic carbon (OC) and elemental carbon (EC) using a thermal–optical transmittance method at an urban site in Beijing, China, from 16 August to 3 September 2006 during the CAREBeijing 2006 campaign. Excellent agreements were obtained between the collocated semi-continuous carbon analyzers, with slopes of 1.02 (R 2 = 0.91) for OC and 1.06 (R 2 = 0.93) for EC, resulting in very similar average EC/total carbon (TC) ratios of ∼0.36. These results imply that the different peak inert mode (100% helium) temperatures did not cause significant biases on the semi-continuous OC and EC measurements. However, it was found that the EC/TC ratio was greatly influenced by the accumulated refractory particles remaining on a quartz filter (PM refractory). Fresh quartz filters, with low PM refractory loadings, which is defined as a laser correction factor ≥0.94, gave ∼8–10% lower EC/TC ratios than aged quartz filters with high PM refractory loadings. The linear regression slope between EC and optically measured EC (OPT-EC) was much higher with fresh quartz filters (slope = 1.03, R 2 = 0.96) than aged quartz filters (slope = 0.89, R 2 = 0.95), suggesting the underestimation of EC on fresh quartz filters by ∼15% compared to those measured on aged quartz filters. Authentic standard humic-like substances (HULIS) on the clean quartz filter showed the highest extent of pyrolyzed organic carbon (POC) formation (47.4% in total detected carbon mass), followed by those on the Asian dust loaded quartz filter (37%) and the refractory urban pollutant loaded quartz filter (34.1%), indicating that the Asian dust and refractory urban pollutant reduced the POC formation from the HULIS. Thus, this study suggested that the PM refractory loading plays an important role in the semi-continuous OC and EC measurements by altering the degree of POC formation in the inert atmosphere.Display Omitted► Peak inert temperatures did not cause biases on semi-continuous carbon measurements. ► Refractory particles on a filter reduced the formation of pyrolyzed organic carbon. ► Fresh quartz filters gave ∼8–10% lower EC/TC ratios than aged quartz filters.
Keywords: Organic carbon; Elemental carbon; Refractory particle; Pyrolyzed organic carbon; Thermal–optical transmittance;
Below-cloud scavenging by rain of atmospheric gases and particulates by Nora Duhanyan; Yelva Roustan (7201-7217).
Below-cloud scavenging (BCS) by rain is one of the phenomena that control the removal of atmospheric pollutants from air. The present work introduces a detailed review of the most literature referred theories and parameterisations to describe the below-cloud scavenging by rain in air quality modelling. The theories and parameterisations in question concern the raindrop size distribution (RSD), the terminal velocity of raindrops, and the below-cloud scavenging coefficient for gaseous and particulate pollutants. 0D computations are run to calculate the latter coefficient with the help of the current theories and parameterisations thus extracted from the literature. As a result to improve the atmospheric modelling studies, it can be mentioned that the choice of the raindrop terminal velocity among the available parameterisations does not matter much and therefore, the practice of the most simple formulae is advised. On the other hand, a great dispersion on the scavenging coefficient (several orders of magnitude) is observed related to the variations of the RSD. Therefore, a great care is recommended in the choice of the RSD with respect to the type of rain and sampling duration involved (e.g. thunderstorm, widespread, shower, etc.; long or instantaneous sampling duration). Many uncertainties do remain due to the lack of precision in the experimental records after which the RSD parameterisations are established or to the poor level of accuracy of the theoretical models.► Review on the below-cloud scavenging by rain of gaseous and particulate pollutants. ► Sensitivity of the scavenging coefficient to the raindrop size distributions. ► The RSDs are sorted out by rain type and sampling duration. ► Comparison of the parameterisations of the literature extracted SCs.
Keywords: Scavenging coefficient; Model; Below-cloud scavenging by rain; Raindrop size distributions; Raindrop terminal velocities; Gas; Particulate matter;
Combined measurements of a UV mini MAX-DOAS system and a TX for retrieval of ambient trace gas mixing ratio: Comparisons with combined RTM and MAX-DOAS methods by Hanlim Lee; Jaeyong Ryu; Jhoon Kim; Youngmin Noh; Younghun Yoon (7218-7226).
A measurement method combining multi-axis differential optical absorption spectroscopy (MAX-DOAS) and a transmissometer (TX) is introduced as a means of retrieving surface trace gas mixing ratios in ambient air. The combined measurement method was utilized to derive surface NO2 mixing ratios from 27 March to 11 May 2007 in Seoul, Korea. To convert the differential slant column density (DSCD) to the volume mixing ratio (VMR), the light path length (LPL) along the MAX-DOAS line of sight was derived using the light extinction coefficient and Ångstrom exponent data obtained by a TX and sunphotometer, respectively. Temporal variations of the NO2 VMRs at the 0–1 km layer obtained from radiative transfer model (RTM) simulations coupled with MAX-DOAS data show similar patterns, but with reduced magnitudes, to the ground level data and those of the combined MAX-DOAS and TX measurements at 0.08 km. The NO2 VMRs retrieved by the combined measurement were in agreement with those obtained from the RTM simulations coupled with MAX-DOAS data and the in-situ measurements within 40 and 50%, respectively. The coefficient of determination (R 2) of 0.75 was obtained between the combined measurement data sets and those of the RTM simulations coupled with MAX-DOAS data whereas that between the combined measurement data sets and those of the in-situ measurements was 0.53. The coefficient of determination (R 2) between the data sets derived from the RTM simulations coupled with MAX-DOAS data and those of the in-situ measurements was 0.67 with the scatter of the correlation within the 50% range.► Detectable ranges of MAX-DOAS were estimated from TX measurements. ► Ambient NO2 VMRs were obtained from combined MAX-DOAS and TX measurements. ► The retrieved NO2 VMRs were comparable to those of RTM simulations coupled with MAX-DOAS data. ► They show a small discrepancy with surface NO2 data due to geometrical differences.
Keywords: Nitrogen dioxide; Light path length; MAX-DOAS; TX; Radiative transfer model;
Predicting wetland contamination from atmospheric deposition measurements of pesticides in the Canadian Prairie Pothole region by Paul G. Messing; Annemieke Farenhorst; Don T. Waite; D.A. Ross McQueen; James F. Sproull; David A. Humphries; Laura L. Thompson (7227-7234).
Although it has been suggested that atmospheric deposition alone can result in detectable levels of pesticides in wetlands of the Pairie Pothole Region of Canada, this is the first field study to compare the masses of pesticides entering wetlands by atmospheric deposition with those concentrations of pesticides detected in the water-column of prairie wetlands. Weekly air and bulk deposition samples were collected from May 26th to Sept. 15th, 2008 at the Manitoba Zero Tillage Research Association (MZTRA) Farm, Brandon, Manitoba, with four on-site wetlands (approximate sizes 0.15–0.45 ha) monitored every second week. Twelve pesticides were detected in the air, with MCPA (one of the three pesticides applied on the farm in 2008 in addition to clopyralid and glyphosate), triallate, and γ-HCH being detected every week. Calculations were performed to predict wetland pesticide concentrations based on bulk deposits alone for those pesticides that had detectable concentrations in the bulk deposition samples (in order of the highest total seasonal deposition mass to the lowest): MCPA, glyphosate, 2,4-D, clopyralid, bromoxynil, atrazine, dicamba, metolachlor, and mecoprop. The estimated concentrations were closest to actual concentrations for MCPA (Pearson correlation coefficient’s = 0.91 to 0.98; p-values < 0.001) and predictions were also reasonable for a range of other herbicides, but a source other than atmospheric deposition was clearly relevant to detections of clopyralid in the wetland water-column. Although the types and levels of pesticides detected in the wetlands of the current study suggest that regional pesticide applications can contribute to pesticide surface water contamination following atmospheric transport and deposition, the greater frequency and concentrations of clopyralid, MCPA, and glyphosate detections in wetlands confirm that on-farm pesticide applications have a greater impact on on-site water quality. Beneficial management practices that reduce application drift, as well as rainfall or snowmelt runoff, will be important measures in reducing pesticide loading into wetlands situated in agricultural fields of the Prairie Pothole Region of North America.► Pesticide residues detected in prairie atmosphere and wetlands. ► Both regional and on-farm pesticide applications are contaminant sources. ► Wetland pesticide concentrations were predicted based on bulk deposits alone. ► Predictions were reasonable for the majority of herbicides.
Keywords: Pesticides; Agriculture; Prairie Pothole Region; Wetlands; Air; Bulk deposition;
Modeling indoor odor–odorant concentrations and the relative humidity effect on odor perception at a water reclamation plant by Tingting Wang; Chakkrid Sattayatewa; Dhesikan Venkatesan; Kenneth E. Noll; Krishna R. Pagilla; Demetrios J. Moschandreas (7235-7239).
Models formulated to associate odors and odorants in many industrial and agricultural fields ignore the potential effect of relative humidity on odor perception, and are not validated. This study addresses literature limitations by formulating a model that includes relative humidity and by validating the model. The model employs measured paired values, n = 102, of indoor odors and odorants from freshly dewatered biosolids in a post-digestion dewatering building of a Water Reclamation Plant (WRP). A random sub-sample of n = 32 is used to validate the model by associating predicted vs. measured values (R 2 = 0.90). The model is validated again with a smaller independent database from a second WRP (R 2 = 0.85). Moreover this study asserts that reduction of hydrogen sulfide concentrations, conventionally used as a surrogate of sewage odors, to acceptable levels does not assure acceptable odor levels. It is concluded that: (1) The addition of relative humidity results in a stronger association between odors and odorants than the use of H2S alone; (2) the two step model validation indicates that the model is not simply site-specific but can be applied to similar facilities; and (3) the model is a promising tool for designing odor and odorant control strategies, the ultimate goal of engineering studies.► An odor–odorant model is formulated for freshly dewatered biosolids indoors. ► Adding relative humidity increases the association between odors and odorants. ► The model is validated with data from the studied WRP and a different WRP. ► The model is not simply site-specific but can be applied to similar facilities. ► The model is a promising tool for designing odor and odorant control strategies.
Keywords: Model formulation; Validation; Indoor odors; Odorants; Relative humidity; Biosolids;
High-PM10 concentration episodes in Seoul, Korea: Background sources and related meteorological conditions by Seungmin Lee; Chang-Hoi Ho; Yong-Sang Choi (7240-7247).
This study examines the origin of and favorable meteorological conditions for high concentrations of particulate matter with a diameter <10 μm (PM10) in Seoul, Korea, in conjunction with systematic PM10 pathways. High-PM10 episodes, defined as days in which the 24-h mean PM10 exceeds 100 μg m−3, occurred 254 times during the period 2001–2008. Based on back trajectory and clustering analyses, the background sources of the high-PM10 in Seoul are categorized as external (176 episodes) and internal sources (78 episodes). The primary external sources include the industrial areas in inland China and the Gobi desert. The ratio of external to internal sources varies strongly according to the season, with highs in winter and spring and lows in summer. A composite analysis of meteorological factors for high-PM10 episodes with respect to the two sources (i.e., external and internal) suggests that an anomalous high pressure over Korea accompanied by an anomalous low pressure over the source regions favors both upper-level transport from the external source regions and the local accumulation of atmospheric PM10 in Seoul. The origins of high-PM10 episodes and their associated meteorological conditions found in this study can provide theoretical underpinnings for dust control strategies.► We examine the origin and the meteorologies of high-PM10 episodes in Seoul, Korea. ► The episodes by external sources are more frequent than those by internal sources. ► Wind and pressure fields determine both the occurrence and the type of episodes.
Keywords: PM10; Background source; Meteorology; Long-range transport;
Temporal variability of trace metal mobility of urban particulate matter from Beijing – A contribution to health impact assessments of aerosols by Nina J. Schleicher; Stefan Norra; Fahe Chai; Yizhen Chen; Shulan Wang; Kuang Cen; Yang Yu; Doris Stüben (7248-7265).
The total element concentration and the chemical fractionation of 18 elements (Al, As, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Ni, Pb, Rb, Sr, Ti, V, Zn) in total suspended particulate matter (TSP) from Beijing, China, were studied for a period of three years (July 2005–May 2008, n = 35). Additionally, particulate matter smaller than 2.5 μm (PM2.5) was included in the study (February 2005–September 2007, n = 32). A chemical sequential extraction scheme according to was applied to assess the speciation and potential mobility of the elements. Four different fractions were distinguished, which can be classified as: (f1) water-extractable, (f2) bound to carbonates, oxides and reducible metals, (f3) bound to organic matter, oxidisable and sulfidic metals, and (f4) residual fraction.The chemical speciation results illustrated that potential toxic metals like Zn (41%), Cd (40%), Mn (32%), and As (29%) were detectable to a high percentage in the water-soluble fraction (f1) of TSP samples and consequently are especially harmful to the environment and exposed people. Lead and Cu in TSP samples showed highest extractability in fraction f2 (53% and 23%, respectively) and can also be considered as mobile with a negative impact on the environment and the human health. Fine particles (PM2.5) showed comparable results with sometimes higher percentages in the highly mobile fraction f1, for example for As (52%).Anthropogenic sources, such as industry and traffic, played an important role for overall atmospheric pollution throughout the year. Additionally, these more or less constant emissions were superimposed by seasonal sources, especially coal combustion in winter and geogenic dust in spring. Coal combustion proved to be a source especially relevant for the toxic and mobile elements Cd, As and Pb. The study illustrated that special attention has to be taken to the mentioned elements and their related sources for health impact assessments and when planning mitigation measures for urban atmospheric pollution and for providing a sustainable development of cities and megacities.► The chemical fractionation of metals in TSP and PM2.5 samples from Beijing was studied. ► Sequential extractions were applied in order to determine the mobility of elements. ► A high bioavailability of toxic metals like Zn, Cd, Mn, As, Cu and Pb was observed. ► Concentrations and the share in the mobile fraction varied over the annual course. ► Coal combustion was a major source for bioavailable toxic metals in atmospheric particles.
Keywords: Aerosol; Heavy metals; Chemical speciation; Sequential extraction; Megacity;
Sources for PM air pollution in the Po Plain, Italy: I. Critical comparison of methods for estimating biomass burning contributions to benzo(a)pyrene by C.A. Belis; J. Cancelinha; M. Duane; V. Forcina; V. Pedroni; R. Passarella; G. Tanet; K. Douglas; A. Piazzalunga; E. Bolzacchini; G. Sangiorgi; M.-G. Perrone; L. Ferrero; P. Fermo; B.R. Larsen (7266-7275).
Particle-bound benzo(a)pyrene (B(a)P) constitutes an air pollution problem in many areas of Europe and has been linked to biomass burning (BB). The present study, conducted in 2007 and 2009 at ten stations in the North Italian Po Plain and Valtelline Valley, examines four methods for the quantification of BB contributions to particle-bound B(a)P using data for 61 predictor compounds in more than 700 ambient PM10 and PM2.5 samples. The study was carried out during the heating season – a period of the year with minimal volatilization and atmospheric degradation of B(a)P, which favour source apportionment by receptor modelling.The lowest estimates of the source contribution (SCE) from BB were obtained with the levoglucosan tracer method and multi-linear regression analysis of daily variations in B(a)P concentrations using levoglucosan as the main predictor in combination with a few other predictors including gaseous pollutants and meteorological data. The standard uncertainty of these methods was driven by the uncertainty in the BB emission factor for levoglucosan and mounted to 90% (1 σ).Positive matrix factorization (PMF), using only PAH congeners as predictors, did not produce factors interpretable as emission sources. However, PMF utilizing a broad range of predictor compounds afforded five factors with compositions similar to emission sources. The yielded B(a)P SCEs for BB agreed well with results of chemical mass balance modelling (CMB). Both receptor models gave good predictions (p) of the observed (o) B(a)P concentrations (PMF: p/o = 89 ± 9%, CMB: p/o = 114 ± 17%) with lower uncertainties than the tracer methods (CMB 60%; PMF 54%; 1 σ). The average BB SCEs (mean ± 95% confidence interval) from these models were: 1.0 ± 0.4 ng m−3 at a kerbside in Milan, 1.0 ± 0.2 ng m−3 at six urban background stations in the Po Plain, 0.7 ± 0.3 ng m−3 at two rural background stations in the Po Plain, and 2.1 ± 1.1 ng m−3 at an urban background station in the Valtelline Valley representing 74 ± 32%, 79 ± 18%, 85 ± 33%, and 84 ± 46% of all modelled B(a)P sources, respectively.► Source apportionment methods for ambient PM-bound B(a)P were compared in North Italy. ► Uncertainties on the results ranged from 54% PMF; 60% CMB to 90% tracer methods. ► Winter biomass burning contributed on average 1–2 ng m−3 B(a)P. ► Biomass burning makes up 74–85% of all B(a)P sources; traffic most of the rest. ► Similar results for other 5–6 ring PAHs and for the sum of 4–6 ring PAHs.
Keywords: Levoglucosan; PAH; CMB; PMF; MLR;
Identifying the factors influencing PM2.5 in southern Taiwan using dynamic factor analysis by Yi-Ming Kuo; Sheng-Wei Wang; Cheng-Shin Jang; Naichia Yeh; Hwa-Lung Yu (7276-7285).
Several heavily polluted industrial parks are located in the coastal area of Kaohsiung city, which the Taiwan EPA has declared to be the worst air quality region in Taiwan. This research used dynamic factor analysis (DFA) to investigate the source contributions of PM2.5 by monitoring data collected at the four aerosol supersites in Southern Taiwan throughout 2009. Dynamic factor analysis is a technique used to reduce or summarize the dimensions being studied, and is a proven useful technique for this type of study, which handles complex gaseous pollutant conditions. The results of the optimal DFA model showed that PM2.5 concentrations in the Kaohsiung metropolis were primarily influenced by explanatory variables that included sulfate ( SO 4 2 − ), nitrate ( NO 3 − ), carbonaceous aerosols, carbon monoxide (CO), sulfate oxides (SO2), nitrate oxides (NO2), and relative humidity (RH). The concentrations were also slightly affected by two common trends representing unexplained variables. Particulate sulfate was the primary variable among the identified explanatory variables. The optimal DFA model satisfactorily accounted for the fluctuations in PM2.5 for the four aerosol supersites (coefficient of efficiency = 0.93). That is, the extreme concentrations of PM2.5 could be successfully described by considering the selected explanatory variables. We used this DFA model successfully to research PM2.5, and future studies concerned with Kaohsiung air quality should consider gaseous pollutants and human activities that our model has identified.► PM2.5 process investigated by DFA to reveal underlying space-time patterns. ► S/T PM2.5 associated with various aerosol and meteorological data are investigated. ► The most significant contributors to PM2.5 temporal process are identified. ► Two common trends characterize space-time PM2.5 variation are identified. ► DFA can successfully characterize the PM2.5 process in this case study.
Keywords: Dynamic factor analysis; PM2.5; Aerosol supersite; Sulfate; Kaohsiung;
Diffuse PM10 emission factors associated with dust abatement technologies in the ceramic industry by E. Monfort; V. Sanfélix; I. Celades; S. Gomar; F. Martín; B. Aceña; A. Pascual (7286-7292).
In this paper, an analytical methodology is proposed for estimating diffuse dust emissions from bulk solids managing (storage, handling, and transport) activities in the ceramic industry. The methodology is based on analytical methods drawn from the AP-42, US Environmental Protection Agency reports and the Emission Estimation Technique (EET) Manual for Mining from Environment Australia. The analytical methods were evaluated by means of experimental campaigns in open and closed bulk solids storage and managing facilities in ceramic plants.Dust concentrations and meteorological variables were recorded in experimental field studies in order to implement the experimental models: a method based on Reverse Dispersion Modelling (RDM) was applied in open facilities, and the Roof Monitor Method (RMM) was used to estimate diffuse dust emissions in closed facilities.The proposed methodology was applied to 13 ceramic plants with different technological scenarios. The methodology enabled the diffuse PM10 emission factors associated with different dust abatement technologies to be determined. This methodology thus allows the Best Available Techniques (BATs) to be selected for reducing these emissions in ceramic and similar facilities.► In this study we evaluate and apply a methodology for estimating diffuse dust emissions from bulk solids managing areas. ► The methodology was applied to 13 facilities with different technological scenarios. ► We quantify the overall abatement efficiencies and PM10 emissions factors. ► It shows that if the appropriate measures are applied, high efficiencies can be achieved. ► It allows selection of the Best Available Techniques for reducing diffuse dust emissions.
Keywords: Diffuse PM10 emissions; Emission factors estimation; Abatement technologies; Ceramic industry;
Identification of sources and processes affecting particulate pollution in Thessaloniki, Greece by P.A. Kassomenos; A. Kelessis; A.K. Paschalidou; M. Petrakakis (7293-7300).
The identification of local and remote particulate pollution sources, as well as the understanding of the factors determining the spatial and temporal variability of the particulate matter in urban areas is an issue of increasing public concern, since the above actions are absolutely essential for the design of effective particulate pollution control strategies. In the present study, the sources and the factors affecting the particulate pollution were studied in Thessaloniki, the second largest Greek city, in order to develop the necessary scientific framework for the subsequent development of integrated mitigation and control strategies and the design and implementation of effective environmental policies. Hourly PM10, PM2.5 and PMc concentrations from two monitoring sites (the Egnatia-Dimarchio and the Eptapyrgio stations) were therefore correlated to gaseous pollutant concentrations (CO, NO, NO2, NO x , SO2 and O3) and meteorological parameters (temperature, wind speed and relative humidity) during the 2-year period between June 2006 and May 2008. The analysis revealed that both sites experienced poor air quality, while a large number of exceedances of the daily and annual EC objectives were observed, especially during the cold season. Positive correlation between particles and NO x in DHM, provided evidence about higher combustion-related emissions during the cold season, whereas increased contribution of secondary particles was suggested during the warm season. In addition, Principal Component Analysis was used to identify the main particulate pollution sources, while the quantification of the combustion and the non-combustion-related fraction of particles was performed through Regression Analysis. Specifically, the non-combustion-related fraction ranged between 25.1 and 72.7%, depending on the site and the season. Finally, concentration roses were constructed in order to gain insight into the distribution of local emission sources around the monitoring sites.► Both sites experienced poor air quality with a significant number of exceedances. ► Strong correlation between PM and NO x in DHM suggested combustion-related emissions. ► Weak correlation between PM and CO suggested the big number of diesel taxis and buses. ► The non-combustion-related fraction of particles was calculated between 25.1 and 72.7%. ► The synergy among local emissions and sea breezes was detected in both sites.
Keywords: Particulate pollution; Urban background; Source identification; Source apportionment; Non-combustion sources;
Sources, distribution, and acidity of sulfate–ammonium aerosol in the Arctic in winter–spring by Jenny A. Fisher; Daniel J. Jacob; Qiaoqiao Wang; Roya Bahreini; Claire C. Carouge; Michael J. Cubison; Jack E. Dibb; Thomas Diehl; Jose L. Jimenez; Eric M. Leibensperger; Zifeng Lu; Marcel B.J. Meinders; Havala O.T. Pye; Patricia K. Quinn; Sangeeta Sharma; David G. Streets; Aaron van Donkelaar; Robert M. Yantosca (7301-7318).
We use GEOS-Chem chemical transport model simulations of sulfate–ammonium aerosol data from the NASA ARCTAS and NOAA ARCPAC aircraft campaigns in the North American Arctic in April 2008, together with longer-term data from surface sites, to better understand aerosol sources in the Arctic in winter–spring and the implications for aerosol acidity. Arctic pollution is dominated by transport from mid-latitudes, and we test the relevant ammonia and sulfur dioxide emission inventories in the model by comparison with wet deposition flux data over the source continents. We find that a complicated mix of natural and anthropogenic sources with different vertical signatures is responsible for sulfate concentrations in the Arctic. East Asian pollution influence is weak in winter but becomes important in spring through transport in the free troposphere. European influence is important at all altitudes but never dominant. West Asia (non-Arctic Russia and Kazakhstan) is the largest contributor to Arctic sulfate in surface air in winter, reflecting a southward extension of the Arctic front over that region. Ammonium in Arctic spring mostly originates from anthropogenic sources in East Asia and Europe, with added contribution from boreal fires, resulting in a more neutralized aerosol in the free troposphere than at the surface. The ARCTAS and ARCPAC data indicate a median aerosol neutralization fraction [NH4 +]/(2[SO4 2−] + [NO3 −]) of 0.5 mol mol−1 below 2 km and 0.7 mol mol−1 above. We find that East Asian and European aerosol transported to the Arctic is mostly neutralized, whereas West Asian and North American aerosol is highly acidic. Growth of sulfur emissions in West Asia may be responsible for the observed increase in aerosol acidity at Barrow over the past decade. As global sulfur emissions decline over the next decades, increasing aerosol neutralization in the Arctic is expected, potentially accelerating Arctic warming through indirect radiative forcing and feedbacks.► We interpret Arctic sulfate–ammonium aerosol data using a chemical transport model. ► A mix of natural and anthropogenic sources contribute to Arctic sulfate burdens. ► West Asia is the largest source of sulfate to Arctic surface air in winter. ► Arctic ammonium is dominated by agricultural and open burning emissions. ► Spring aerosol is acidic throughout the troposphere and most acidic at the surface.
Keywords: Arctic; Aerosol acidity; Sulfate; Ammonium; Pollution sources;
Characterization of water-soluble organic aerosol in coastal New England: Implications of variations in size distribution by L.D. Ziemba; R.J. Griffin; S. Whitlow; R.W. Talbot (7319-7329).
Size distributions up to 10-micron aerosol diameter (D P) of organic carbon (OC) and water-soluble organic carbon (WSOC) were measured at two sites in coastal New England, slightly inland at Thompson Farm (TF) and offshore at Isles of Shoals (IOS). Significant OC concentrations were measured across the full size distribution at TF and IOS, respectively. The WSOC fraction (WSOC/OC) was largest in the accumulation mode with values of 0.86 and 0.93 and smallest in the coarse mode with values of 0.61 and 0.79 at TF and IOS, respectively. Dicarboxylic acids containing up to five carbon atoms (C5) were concentrated in droplet and accumulation mode aerosol with only minor contributions in the coarse mode. C1–C3 monocarboxylic acids were generally near or below detection limits. Results from proton nuclear magnetic resonance (H+-NMR) spectroscopy analyses showed that the organic functional group characterized by protons in the alpha position to an unsaturated carbon atoms ([H–C–C＝]) was the dominant WSOC functionality at both TF and IOS, constituting 34 and 43% of carbon-weighted H+-NMR signal, respectively. Size distributions of each H+-NMR-resolved organic functionality are presented. Source apportionment using H+-NMR fingerprints is also presented, and results indicate that nearly all of the WSOC at TF and IOS spectroscopically resembled secondary organic aerosol, regardless of D P.► Aerosol size distributions were measured at two sites in coastal New England. ► Organic aerosol was highly water-soluble at both sites, even in the coarse mode. ► Dicarboxylic acids were concentrated in droplet and accumulation mode aerosol. ► Size-resolved organic functionality by H+-NMR suggests a dominant secondary source. ► Coarse mode aerosol at the inland site likely had a primary biological source.
Keywords: Particle size distribution; Water-soluble organic carbon; AIRMAP; Nuclear magnetic resonance spectroscopy; Carboxylic acid;
Impact of dedicated E85 vehicle use on ozone and particulate matter in the US by Uarporn Nopmongcol; W. Michael Griffin; Greg Yarwood; Alan M. Dunker; Heather L. MacLean; Gerard Mansell; John Grant (7330-7340).
Increased use of ethanol as a vehicle fuel worldwide warrants the need to understand air quality impacts of replacing gasoline with ethanol. This study evaluates the impacts of dedicated E85 (85% ethanol/15% gasoline) light-duty vehicles on emissions, ozone and particulate matter (PM) concentrations in the United States for a future year (2022) using a 3-D photochemical model, detailed emissions inventories that account for changes in all sectors studied, and winter and summer meteorology that occurred in 2002. Use of E85 introduces new emissions from ethanol production and distribution, reduces petrochemical industry emissions due to lower gasoline consumption, changes on-road vehicle emissions and alters biogenic emissions due to land use changes. Three scenarios with increased ethanol production for dedicated E85 light-duty vehicles were compared to a base case without increased ethanol production. Increased use of E85 caused both increases and decreases in ozone and PM, driven mainly by changes in NO x emissions related to biogenic and upstream petrochemical industry sources. In all states modeled, adoption of dedicated E85 vehicles caused negligible change in average higher ozone and PM concentrations of importance for air quality management strategies. Ozone and PM changes are relatively insensitive to how land area is allocated for switchgrass production. The findings are subject to various uncertainties, especially those in vehicle technology and emissions from cellulosic ethanol production.► Simulations of E85 use in dedicated vehicles in the US. ► Scenarios for 36 and 51 billion gallons of ethanol in year 2022. ► Estimated emissions from ethanol production and distribution and land use. ► Small changes, relative to conventional gasoline vehicles, in higher ozone and PM.
Keywords: Ethanol fuel; Ethanol production; Air quality modeling; Ozone; Particulate matter;
Investigation into approaches to reduce excessive vertical transport over complex terrain in a regional photochemical grid model by Christopher Emery; Ed Tai; Greg Yarwood; Ralph Morris (7341-7351).
Past photochemical modeling of the western United States (US) using the Comprehensive Air quality Model with extensions (CAMx) and the Community Multiscale Air Quality (CMAQ) model has resulted in large springtime ozone over predictions in the complex high-elevation terrain of the western United States (US). Comparisons against rural measurement data have shown that both models over predicted ozone levels by 20 ppb or more. A systematic investigation using CAMx revealed that excessive vertical transport in mountainous terrain draws down upper tropospheric ozone introduced by the lateral boundary conditions (developed by a global chemistry model), which can routinely exceed 1 ppm near the tropopause. This is not an unreasonable concentration at such altitudes during the spring, and there is observational evidence that stratospheric ozone intrusions result in occasional large ground-level concentrations in the western US, but not at the frequency and intensity simulated by the CAMx and CMAQ models. Past versions of CAMx and CMAQ possess similar algorithms to diagnose vertical velocity, and similar first-order accurate vertical advection algorithms. These similarities, in conjunction with poor vertical resolution of the upper troposphere, have resulted in similar ozone performance issues. Numerous approaches were explored with CAMx in an attempt to externally reduce the rates of vertical transport over complex terrain. Ultimately, we formulated and tested a new vertical advection methodology that included improvements to how vertical velocities are determined and introduced a second-order accurate advection solver technique. Together these improvements proved to yield the most successful results in reducing upper tropospheric ozone transport to the surface. CAMx was then run to simulate ozone throughout the western US for a full year to evaluate the effects of the new vertical transport algorithm on model performance. Ozone performance improvements exceeded those achieved through the application of arbitrary reductions in the upper tropospheric/stratospheric lateral boundary conditions.► CAMx and CMAQ have over predicted ozone in the inter-mountain western US. ► Primarily caused by treating vertical circulations with simple advection schemes. ► This is important for modeling background ozone and lower ozone standard. ► Several approaches were tested in CAMx to resolve this problem. ► Higher resolution and a higher-order vertical advection scheme were most effective.
Keywords: CAMx; CMAQ; Ozone transport; Vertical advection;
Atmospheric concentrations of polycyclic aromatic hydrocarbons and selected nitrated derivatives in Greater Cairo, Egypt by Hossam F. Nassar; Ning Tang; Takayuki Kameda; Akira Toriba; Mamdouh I. Khoder; Kazuichi Hayakawa (7352-7359).
Polycyclic aromatic hydrocarbons (PAHs) and selected nitrated derivatives (NPAHs) in air were determined at two sites, El Dokki (a traffic site) and El Teppen (an industrial site) in Greater Cairo, Egypt, during the winter and summer seasons. The sites were selected to represent areas with different activities of Greater Cairo. The concentrations of fifteen PAHs having two to six rings were determined by using HPLC with florescence detection, while the concentrations of two NPAHs, 1-nitropyrene (1-NP) and 6-nitrocrysene (6-NC), were determined using HPLC with chemilumencence detection. Both the PAH and NPAH concentrations in El Teppen were higher than those in El Dokki. The total average concentrations of the fifteen PAHs over the investigated sites were 45.98 pmol m−3 in El Dokki and 77.01 pmol m−3 in El Teppen. All PAH and NPAH concentrations were higher in winter than in summer. The total average concentration of PAHs ranged from 21.9 pmol m−3 in summer to 63.74 pmol m−3 in winter. PAHs having four to six rings were the predominant compounds in particulate matters. The total average concentrations of the two NPAHs (1-NP and 6-NC) were 30.2 and 12.4 fmol m−3, respectively, in El Dokki, and 39.5 and 15.6 fmol m−3 respectively, in El Teppen. The total average concentrations of 1-NP and 6-NC were 36.99 and 15.43 fmol m−3, respectively, in winter, and 29.76 and 10.56 fmol m−3, respectively, in summer. These concentrations were compared with those of several cities in Asia that have been undergoing rapid economic and industrial development. The major sources and secondary reactions of PAHs and NPAHs were estimated based on the [NPAH]/[PAH] and [PAH]/SPM ratios. ► In this report, PAHs and selected NPAHs were sampled from two sites in Egypt. ► The seasonal concentration differences at both sites were investigated. ► The measured concentrations were compared with other different sites in Asia. ► Major sources and secondary reactions of PAHs and NPAHs were identified.
Keywords: Polycyclic aromatic hydrocarbon; Nitrated polycyclic aromatic hydrocarbon; Greater Cairo; Solid phase matter; Atmosphere;
Use of light-extinction method and inverse modeling to study aerosols in the Paso del Norte Airshed by Angel E. Esparza; Rosa M. Fitzgerald; Thomas E. Gill; Javier Polanco (7360-7369).
A light-extinction technique for monitoring aerosols was used in conjunction with a robust inverse reconstruction model to retrieve aerosol size distribution. Results for the columnar aerosol size distribution for the Paso del Norte Airshed for two different pollution scenarios and at two different seasons were presented. These are well correlated with experimental surface aerosol data for this region. It was observed that, for the clean day scenario, the summer case showed a greater columnar concentration of smaller size aerosols than the winter case. Results for the columnar aerosol size distribution in the polluted day scenario demonstrated that the concentration of aerosols were greater in the summer than in the winter. In addition, HYSPLIT backward trajectories were used to identify pollution sources.► A method using MFRSR and a robust model to retrieve aerosol size is presented. ► The method was applied to a complex interface region, the Paso del Norte. ► This research will permit an evaluation of air pollution control measures. ► The aerosol size selected for this research is known to be harmful to health.
Keywords: Aerosols; Particulate matter; Inverse reconstruction; Air pollution; Aerosol optical depth; Aerosol optical characterization;
Baseline continental aerosol over the central Tibetan plateau and a case study of aerosol transport from South Asia by Xiangao Xia; Xumei Zong; Zhiyuan Cong; Hongbin Chen; Shichang Kang; Pucai Wang (7370-7378).
Using 22 months of sunphotometer observations at Nam Co, an Aerosol Robotic Network (AERONET) site located in the central Tibetan Plateau, the background level of aerosol in this remote continental site was analyzed for the first time. An extraordinary pollution episode with an aerosol optical depth at 500 nm (τ) of an order of magnitude higher than the baseline was further studied using ground-based and satellite remote-sensing data. The annual aerosol baseline at Nam Co is τ = 0.029, which is about half of that over the Pacific Ocean and the Atlantic Ocean. Sunphotometer observations at Nam Co recorded an intense spring atmospheric pollution episode, with the maximum τ of 0.42 on 16 March 2009. The episode was characterized by dominant fine particles with strong absorption. A large τ value with similar size and absorption also occurred in the Indo-Gangetic plains and South Asia, suggesting the transportation of aerosols to the Tibetan Plateau from surrounding regions. The passive satellite data showed dense plumes associated with active fires in the Himalayan foothills, the Indo-Gangetic plains, and South Asia and a thick, widespread haze piling up against the Himalayan ridges and impinging upon adjacent valleys. A pollution pool with a thick layer rich with aerosol over the Ganges Plain in Northern India, as revealed by the active satellite data, extended up to 3–5 km during this period, making it possible for the transportation of aerosols to the central Tibetan Plateau by the southwesterly wind prevailing at that level. Further studies are urgently required to identify the transport mechanism and to reveal the potential climatic impacts of aerosol transportation to the Tibetan Plateau.► The background level of aerosol at a Tibetan site is revealed. ► A spring atmospheric pollution episode over the central TP is shown. ► Aerosol transportation from South Asia to the central TP is revealed.
Keywords: Aerosol; Tibetan plateau; Baseline; Transportation;
The model SIRANE for atmospheric urban pollutant dispersion; part I, presentation of the model by Lionel Soulhac; Pietro Salizzoni; F.-X. Cierco; Richard Perkins (7379-7395).
In order to control and manage urban air quality, public authorities require an integrated approach that incorporates direct measurements and modelling of mean pollutant concentrations. These have to be performed by means of operational modelling tools, that simulate the transport of pollutants within and above the urban canopy over a large number of streets. The operational models must be able to assess rapidly a large variety of situations and with limited computing resources.SIRANE is an operational urban dispersion model based on a simplified description of the urban geometry that adopts parametric relations for the pollutant transfer phenomena within and out of the urban canopy.The streets in a city district are modelled as a network of connected street segments. The flow within each street is driven by the component of the external wind parallel to the street, and the pollutant is assumed to be uniformly mixed within the street. The model contains three main mechanisms for transport in and out of a street: advection along the street axis, diffusion across the interface between the street and the overlying air flow and exchanges with other streets at street intersections.The dispersion of pollutants advected or diffused out of the streets is taken into account using a Gaussian plume model, with the standard deviations σy and σz parameterised by the similarity theory. The input data for the final model are the urban geometry, the meteorological parameters, the background concentration of pollutants advected into the model domain by the wind and the emissions within each street in the network.► SIRANE simulates pollutant dispersion in urban atmosphere at the district scale. ► Flow and dispersion within the urban canopy are modelled by means of a street network approach. ► The dispersion in the external atmosphere is modelled by a Gaussian model.
Keywords: Numerical model; Pollutant dispersion; Street network; Urban canopy;
The determination of a “regional” atmospheric background mixing ratio for anthropogenic greenhouse gases: A comparison of two independent methods by U. Giostra; F. Furlani; J. Arduini; D. Cava; A.J. Manning; S.J. O’Doherty; S. Reimann; M. Maione (7396-7405).
Halocarbons are powerful greenhouse gases capable of significantly influencing the radiative forcing of the Earth’s atmosphere. Halocarbons are monitored in several stations which are globally distributed in order to assess long term atmospheric trends and to identify source regions. However, to achieve these aims the definition of background mixing ratios, i.e. the mixing ratio in a given air mass when the recent contribution of local sources is absent, is necessary. This task can be accomplished using different methods. This paper presents a statistical methodology that has been devised specifically for a mountain site located in Continental Europe (Monte Cimone, Italy), characterised by the vicinity of strong sources. The method involves the decomposition of the observed data distribution into a Gaussian distribution, representative of background values, and a Gamma distribution, ascribable to contribution from stronger sources. The method has been applied to a time series from a European marine remote station (Mace Head, Ireland) as well as to time series from Monte Cimone. A comparison of the methodology described in this paper with a well-established meteorological filtering procedure at Mace Head has shown an excellent agreement. A comparison of the baselines at Mace Head, Mt. Cimone and the Swiss alpine station of the Jungfraujoch highlighted the occurrence of a specific background concentration. Although this paper presents the application of the method to three hydrofluorocarbons, the proposed methodology can be extended to any long lived atmospheric component for which a long term time series is available and at any location even if affected by strong source regions.► We present a method for evaluating the baseline for halocarbons at a European site. ► A correct baseline is crucial for assessing trends and identifying source areas. ► We compare the method with a well-established meteorological filtering procedure. ► The method gives the atmospheric trends and seasonality of the halocarbon data. ► An assessment is given of the global representativity of the site.
Keywords: Halocarbons; Baseline; Continuous observations; Long term trends; Sources;
Comparison of aerosol optical properties from Beijing and Kanpur by Shupeng Wang; Li Fang; Xingfa Gu; Tao Yu; Jun Gao (7406-7414).
Aerosol Robotic Network (AERONET) aerosol optical depth (AOD) and almucantar retrievals (single scattering albedo (SSA) and aerosol size distribution) from 2005–2009 in Beijing and Kanpur are used to analyze differences and similarities in aerosol optical properties over these two regions. The examination of monthly mean AOD (440 nm) shows that maximum and minimum values occurred in summer and winter, respectively, for Beijing, while the range in AOD in Kanpur was lower. Precipitation in both Beijing and Kanpur peaked in summer; however, the columnar water vapor (CWV) exhibited a high correlation with AOD in Beijing (R 2 = 0.79) but had a weak relationship with AOD in Kanpur (R 2 = 0.13). The Angstrom exponent (α, 440–870 nm) generally increased linearly as the fine mode fraction (FMF) of AOD (500 nm) increased for FMF < 90% in both regions, with a high correlation of R 2 > 0.96. However a clear decrease in α for FMF > 90% found in Beijing is not shown distinctly in Kanpur, and is mainly due to the higher aerosol loading in this FMF bin at Beijing (AOD at 440 nm > 2.2) which results in a stronger coagulation of fine mode particles. Bimodal seasonally-averaged size distributions reveals similar aerosol mixtures composed of fine pollution particles and coarse dust particles in both regions. The analysis of spectral SSA as a function of α is emphasized in this paper. The average SSA at 440 nm in both regions shows a similar low dynamic range of ∼0.03 for α < 1.4. The obvious increase in SSA at 440 nm for α > 1.4 in both regions can be attributed to a higher FMF leading to fine mode coagulation. However, the distinctly smaller increase in Kanpur suggests that fine mode aerosols at Beijing are less absorbing than those at Kanpur. The visibly lower SSA at 675 nm at Kanpur compared to that at Beijing for α > 0.4 is due to a larger find-coarse mode separation radius of ∼0.76 μm in Beijing versus a value lower than ∼0.58 μm in Kanpur. Another reason lies in the weaker absorption by fine mode aerosols in Beijing. The distinctly lower near-infrared SSA in Kanpur when α < 1.4, compared to Beijing, may be attributed to lower aerosol concentrations in all α bins, resulting in less aggregation of absorbing black carbon particles on coarse particles in Kanpur. The classification of aerosol properties shows that the AOD accumulation mode in all seasons, even including spring, in Beijing and in post-monsoon and winter seasons in Kanpur can be attributed to fine particle coagulation or hygroscopic growth; during pre-monsoon and monsoon seasons in Kanpur, it is due to coarse mode particle accumulation or cloud contamination.► Higher aerosol loading at Beijing results in stronger coagulation of fine particles. ► Fine mode aerosols at Beijing are less absorbing than those at Kanpur. ► Less BC aggregated on dust leads to weaker absorption at NIR bands in Kanpur. ► AOD growth in Kanpur arises from coarse mode particle accumulation in two seasons.
Keywords: Aerosol; Optical property; Single scattering albedo; Aerosol classification; Beijing; Kanpur;
Aerosol radiative effects over an urban location and a remote site in western India: Seasonal variability by S. Ramachandran; Sumita Kedia (7415-7422).
Seasonal variability in radiative effects due to aerosols in the shortwave and longwave regions is studied utilizing measured aerosol optical properties and models over two distinct environments, namely, Ahmedabad (urban, industrialised location) and Gurushikhar (high altitude remote site) in western India. Top of the atmosphere (TOA) forcing in shortwave varies from positive to negative over Ahmedabad, while over Gurushikhar it is negative throughout the year because of lower surface reflectance and higher single scattering albedo (SSA). Aerosol radiative forcing at the surface (SFC) is >−30 Wm−2 over Ahmedabad. In Gurushikhar SFC forcing increases from winter (−7 Wm−2) to premonsoon (−14 Wm−2), which is attributed to the increase in the amount of dust aerosol loading. Aerosol radiative forcing in the atmosphere (ATM) peaks during postmonsoon with a value of 54 Wm−2 over Ahmedabad, while ATM warming over Gurushikhar peaks during premonsoon (9 Wm−2). Shortwave heating rate is >0.9 K d−1 over Ahmedabad while it is an order of magnitude lower over Gurushikhar.Aerosols produce a positive TOA and SFC forcing in the longwave and cool the atmosphere. Anthropogenic influence is evident from the aerosol radiative effects obtained over Ahmedabad and Gurushikhar. The abundance of fine (coarse) mode aerosols over Ahmedabad (Gurushikhar) results in higher (lower) aerosol optical depth, lower (higher) SSA, and higher (lower) aerosol radiative forcing. Owing to the dissimilar nature of shortwave and longwave radiative effects of aerosols, when coarse mode aerosols are abundant over a region, longwave radiative effects can balance shortwave atmospheric warming produced by aerosols.► Top of the atmosphere forcing varies from positive to negative over Ahmedabad while it is negative over Gurushikhar. ► Abundance of fine mode absorbing aerosols give rise to higher atmospheric warming in Ahmedabad. ► Shortwave heating rate is an order of magnitude lower over Gurushikhar than Ahmedabad. ► Longwave cooling balances the shortwave atmospheric warming when coarse mode aerosols are abundant.
Keywords: Aerosol radiative forcing; Shortwave and longwave forcing; Implications; Seasonal variation; Urban and remote locations;
Evaluation of the operational atmospheric model used in emergency response system at Kalpakkam on the east coast of India by C.V. Srinivas; R. Venkatesan; V. Yesubabu; C. Nagaraju; B. Venkatraman; P. Chellapandi (7423-7442).
The performance of a triple-nested mesoscale atmospheric model (MM5) implemented in the Online Nuclear Emergency Response System (ONERS) at Kalpakkam on southeast coast of India is evaluated. Real-time atmospheric model predictions are used to compute radiological plume dispersion in the mesoscale ranges using Lagrangian particle models. About 280 days falling in dry and wet weather and distributed in 2006, 2007, 2008 and 2009 years are considered. About 25 upper air, 100 surface station data including radiosonde, GPS sonde, micrometeorological tower and automated weather stations are used for model evaluation. Results indicate that model could reproduce the synoptic pressure, geopotential heights, winds and precipitation patterns in the coarse domain as well as the fine scale features of the atmospheric circulation in the inner fine domain. Model diagnosis with observations shows correlation (r), mean absolute error (MAE) and bias as (0.685, 1.87 C, 1.28 C) for temperature, (0.93, 1.55 hPa, 0.113 hpa) for pressure, (0.56,15 m, 0.53 m) for geopotential, (0.55, 12%, −10.5%) for humidity and (0.45, 2.3 m s−1, 1.70 m s−1) for wind speed indicating appreciable performance in the lower atmosphere for both dry and wet weather events. Model error in wind speed/direction reduced with height and slightly increased for temperature and humidity. Model performance is relatively better for dry weather cases than for the rainfall events. Also simulations from high resolution domain-3 are found to be better with relatively lower error metrics than those over coarse domains 1 and 2.► Atmospheric model of emergency response system at Kalpakkam is evaluated. ► Forecasts compared with observations over different seasons. ► Observational comparison indicates mesoscale flows are consistently reproduced. ► Correlations are 0.685, 0.93, 0.56, 0.55, 0.45 for temperature, pressure, gpm, RH, wind. ► Simulations are better for dry weather cases than for rainfall events.
Keywords: Atmospheric dispersion; MM5; Real-time predictions; Model performance;
Particulate and gaseous emissions from manually and automatically fired small scale combustion systems by Christoph Schmidl; Markus Luisser; Emmanuel Padouvas; Leopold Lasselsberger; Magdalena Rzaca; Carlos Ramirez-Santa Cruz; Markus Handler; Ge Peng; Heidi Bauer; Hans Puxbaum (7443-7454).
In an extensive wood combustion source test series 2 automatically and 2 manually fired appliances, and 8 fuel types were investigated with respect to their particulate (PM10) and gaseous emissions. Softwood briquettes, beech, oak and spruce logs, wood pellets as well as further biogenic fuels: wood chips, miscanthus (elephant grass) pellets and triticale (“energy crop”) pellets were tested. Gaseous emissions were measured continuously while PM10 was sampled with a dilution system and averaged over standard test cycles. Manually fired stoves exhibited highly variable emissions resulting in an uncertainty of 30% for most measured compounds, determined in a series of replicate experiments. Average PM10 emissions from manually fired appliances were around 130 mg m−3 (standard conditions for temperature and pressure (STP), 13%O2, dry gas), equivalent to 90 mg MJ−1. Wood pellets and chips combustion under full load operation with automatically fired appliances emit almost one order of magnitude less PM10, respectively: 12–21 mg m−3 (STP, 13%O2, dry gas), or 8–14 mg MJ−1.Around 30% of total particle mass from manually fired systems account for elemental carbon and 30–40% for organic carbon, resulting in carbonaceous fraction content of around 90%. On average around 5% of PM10 emitted by manually fired stoves consisted of levoglucosan while this anhydrous sugar was below detection limit in full- and part load operation of automatically fired systems. Generally, emissions from automated systems were relatively constant for the same fuel type predominantly consisting of inorganic constituents. Emissions are mainly influenced by the mode of operation, start-up, full load or part load for a given fuel type.Surprisingly high emissions were observed for triticale pellets: 184 mg m−3 (125 mg MJ−1,) PM10 and 466 mg m−3 (395 mg MJ−1) NOx, (under full load operation, STP, 13%O2, dry gas), originating from high chlorine and nitrogen contents of the fuel.► Emissions were tested for combustion of briquettes, logs and pellets in modern stoves. ► Automatically fired systems emit an order of magnitude less PM10, mainly inorganics. ► Levoglucosan accounts for 5% of PM10 emitted by manually fired stoves. ► Levoglucosan was mostly below detection limit in automatically fired systems. ► Levoglucosan/mannosan ratios were of 2–4 for softwood and >10 for hardwood.
Keywords: Wood combustion; Levoglucosan; EC/OC; Biomass fuel; PM10 emissions;
Laboratory evaluation of Amazon forest biomass burning emissions by T.G. Soares Neto; J.A. Carvalho; E.V. Cortez; R.G. Azevedo; R.A. Oliveira; W.R.R. Fidalgo; J.C. Santos (7455-7461).
Biomass samples representing Amazon forest native species were burned in laboratory experiments. These species were obtained in the deforestation arc, near the town of Alta Floresta, state of Mato Grosso, Brazil. Moisture content values obtained for twigs and pieces of sticks and leaves of the same species ranged from 9 to 11%, in terms of mass of moisture per total mass. Gas concentrations were measured for carbon dioxide, carbon monoxide, nitrogen oxides, and unburned hydrocarbons. Temperatures, instantaneous burn rates, instantaneous combustion efficiencies and instantaneous emission factors for carbon dioxide and carbon monoxide were evaluated. Burning stages (flaming and smoldering) were identified by visual observation and correlation with the combustion efficiency. The average emission factors were 1565 ± 128, 50.3 ± 17.1, 2.74 ± 0.75, and 14.2 ± 5.9 grams per kg of burned dry biomass, for carbon dioxide, carbon monoxide, nitrogen oxides and unburned hydrocarbons, respectively. These results were compared to average emission factors of carbon dioxide, carbon monoxide, nitrogen oxides and methane determined in field experiments performed in the Amazon region. Agreement with results of field experiments was observed, especially for the flaming stage.► CO2, CO, NO x and UHC emission factors determined for Amazon biomass combustion. ► Laboratory results agreed with data for biomass combustion in field experiments. ► Combustion behavior under flaming and smoldering was analyzed.
Keywords: Biomass burning; Emission factors; Amazon forest; Experimental fires; CO2; CO; NO x ; Hydrocarbons;
Effect of organic compounds on cloud condensation nuclei (CCN) activity of sea spray aerosol produced by bubble bursting by Meagan J.K. Moore; Hiroshi Furutani; Gregory C. Roberts; Ryan C. Moffet; Mary K. Gilles; Brian Palenik; Kimberly A. Prather (7462-7469).
The ocean comprises over 70% of the surface of the earth and thus sea spray aerosols generated by wave processes represent a critical component of our climate system. The manner in which different complex oceanic mixtures of organic species and inorganic salts are distributed between individual particles in sea spray directly determines which particles will effectively form cloud nuclei. Controlled laboratory experiments were undertaken to better understand the full range of particle properties produced by bubbling solutions composed of simplistic model organic species, oleic acid and sodium dodecyl sulfate (SDS), mixed with NaCl to more complex artificial seawater mixed with complex organic mixtures produced by common oceanic microorganisms. Simple mixtures of NaCl and oleic acid or SDS had a significant effect on CCN activity, even in relatively small amounts. However, an artificial seawater (ASW) solution containing microorganisms, the common cyanobacteria (Synechococcus) and DMS-producing green algae (Ostreococcus), produced particles containing ∼34 times more carbon than the particles produced from pure ASW, yet no significant change was observed in the overall CCN activity. We hypothesize that these microorganisms produce diverse mixtures of organic species with a wide range of properties that produced offsetting effects, leading to no net change in the overall average measured hygroscopicity of the collection of sea spray particles. Based on these observations, changes in CCN activity due to “bloom” conditions would be predicted to lead to small changes in the average CCN activity, and thus have a negligible impact on cloud formation. However, each sea spray particle will contain a broad spectrum of different species, and thus further studies are needed of the CCN activity of individual sea spray particles and biological processes under a wide range of controllable conditions.► Simplistic NaCl and oleic acid/SDS particles had significant effect on CCN activity. ► Artificial seawater (ASW) with microorganisms particles contained 34× more carbon. ► ASW particles with microorganisms had with no significant effect on CCN activity. ► Likely organic surface tension reduction of microorganisms offset displaced salt. ► Average CCN activity changes due to “bloom” conditions predicted to be small.
Keywords: Sea salt; Marine aerosol; CCN activity; Air bubble bursting; Marine microorganisms;
Composition of fine and coarse particles in a coastal site of the central Mediterranean: Carbonaceous species contributions by M.R. Perrone; A. Piazzalunga; M. Prato; I. Carofalo (7470-7477).
Total Suspended Particulate (TSP) and PM2.5 samples simultaneously collected at a coastal site (40.4°N; 18.1°E) in the central Mediterranean are analyzed to investigate the relative role of ions (Cl−, NO 3 − , SO 4 2 − , Na+, NH 4 + , K+, Mg2+, Ca2+) and carbonaceous species in the fine (PM2.5) and coarse (TSP–PM2.5) sampled mass. A methodology is described to determine carbonate carbon (CC), organic carbon (OC), and elemental carbon (EC) levels from Thermal Optical Transmittance (TOT) measurements since carbonate particles may significantly contribute to the Mediterranean particulate. We have found that CC levels vary up to 1.7 μg m−3 and 0.8 μg m−3 in the coarse and fine fraction, respectively. OC and EC levels vary up to 3.0 μg m−3 and 1.5 μg m−3, respectively in the coarse fraction, and vary within the 2.2–10 μg m−3 and 0.5–5 μg m−3 range, respectively in the fine fraction. Hence, OC levels may be overestimated mainly in the coarse fraction, if the CC contribution is not accounted for. CO 3 2 − levels (calculated from CC concentrations) account on average for 6% and 10% of the fine and coarse mass, respectively and allow balancing the anion deficit resulting from the ionic balance of ions detected by ion chromatography (IC). Total carbon TC = (OC + EC) accounts on average for 29% and 6% of the fine and coarse mass, respectively. IC ions account for 38% and 17% of the fine and coarse mass, respectively. OC, EC, SO 4 2 − , NH 4 + , and K+ are the major components in the fine fraction, accounting on average for 84% of the analyzed PM2.5 mass. Marine- and crust-originated ions (Cl−, Mg2+, Na+, Ca2+, CO 3 2 − ) and NO 3 − are mainly in the coarse fraction and represent on average 83% of the analyzed coarse mass.► Methodology to monitor carbonate carbon by the Thermal Optical Transmittance technique. ► Elemental, organic, and carbonate carbon in fine and coarse particulate matter. ► Characterization of ions and carbonaceous species in the central Mediterranean PM. ► Role of CO 3 2 − to balance the anion deficit in the TSP and PM2.5 samples. ► Ammonium loss in coarse particulate.
Keywords: Organic carbon; Elemental carbon; Carbonate carbon; Total suspended particulate; PM2.5; Mediterranean particulate composition;
Validating a nondestructive optical method for apportioning colored particulate matter into black carbon and additional components by Beizhan Yan; Daniel Kennedy; Rachel L. Miller; James P. Cowin; Kyung-hwa Jung; Matt Perzanowski; Marco Balletta; Federica P. Perera; Patrick L. Kinney; Steven N. Chillrud (7478-7486).
Exposure of black carbon (BC) is associated with a variety of adverse health outcomes. A number of optical methods for estimating BC on Teflon filters have been adopted but most assume all light absorption is due to BC while other sources of colored particulate matter exist. Recently, a four-wavelength-optical reflectance measurement for distinguishing second hand cigarette smoke (SHS) from soot-BC was developed (Brook et al., 2010; Lawless et al., 2004). However, the method has not been validated for soot-BC nor SHS and little work has been done to look at the methodological issues of the optical reflectance measurements for samples that could have SHS, BC, and other colored particles. We refined this method using a lab-modified integrating sphere with absorption measured continuously from 350 nm to 1000 nm. Furthermore, we characterized the absorption spectrum of additional components of particulate matter (PM) on PM2.5 filters including ammonium sulfate, hematite, goethite, and magnetite. Finally, we validate this method for BC by comparison to other standard methods. Use of synthesized data indicates that it is important to optimize the choice of wavelengths to minimize computational errors as additional components (more than 2) are added to the apportionment model of colored components. We found that substantial errors are introduced when using 4 wavelengths suggested by Lawless et al. to quantify four substances, while an optimized choice of wavelengths can reduce model-derived error from over 10% to less than 2%. For environmental samples, the method was sensitive for estimating airborne levels of BC and SHS, but not mass loadings of iron oxides and sulfate. Duplicate samples collected in NYC show high reproducibility (points consistent with a 1:1 line, R 2 = 0.95). BC data measured by this method were consistent with those measured by other optical methods, including Aethalometer and Smoke-stain Reflectometer (SSR); although the SSR looses sensitivity at filter loadings above 90 ng/mm2. Furthermore, positive correlations (R 2 = 0.7) were observed between EC measured by NIOSH Method 5040 on quartz filters and BC measured in co-located Teflon filter samples collected from both heating and non-heating seasons. Overall, the validation data demonstrates the usefulness of this method to evaluate BC from archived Teflon filters while potentially providing additional component information.► An optical filter method for black carbon is refined and validated for the first time. ► The method can distinguish black carbon from other sources including environmental tobacco smoke and iron oxides. ► This inexpensive method is useful for studies with new or archived particulate matter filters.
Keywords: Black carbon; Integrating sphere; Optical absorbance; Teflon filter; Source apportionment; Cohort study; Method validation;
Aerosol content survey by mini N2-Raman lidar: Application to local and long-range transport aerosols by Philippe Royer; Patrick Chazette; Melody Lardier; Laurent Sauvage (7487-7495).
This study shows an aerosol content survey in the low and middle troposphere over Paris with a compact and light Nitrogen-Raman lidar which has been recently developed by the Commissariat à l’Energie Atomique (CEA) and LEOSPHERE company. This eye-safe and wide field-of-view system (full overlap between 150 and 200 m) is particularly well-adapted to air pollution survey in the vicinity of Megalopolis. Extinction-to-backscatter coefficient (so-called Lidar Ratio LR) profiles obtained with a Tikhonov regularization scheme are presented for long-range transport events of aerosols (volcanic ash plume LR = 48 ± 10 sr, and desert dust, LR = 45 ± 8 sr) which may contribute to the local load of aerosols emitted by traffic and industries in Megalopolis. Due to an insufficient signal to noise ratio (SNR < 30), a new dichotomous algorithm has been developed to perform daytime inversions every hour which is in accordance with the typical time evolution of aerosols within the planetary boundary layer. This inversion scheme is based on the constraint of the elastic channel with the aerosol optical depth (between typically 0.2 and 0.7 km) determined with the N2-Raman channel and thus only gives access to an equivalent LR between 0.2 and 0.7 km with a relative uncertainty lower than 15%. This approach has been applied to retrieve diurnal cycle of LR for polluted continental aerosols over Paris and is compared with Tikhonov regularization applied during the night. We found a mean value of 85 ± 18 sr for polluted continental aerosols which is in agreement with other studies performed around the Paris urban area. Results for aerosol optical properties are presented and the error sources are discussed for each approach.► A compact nitrogen Raman lidar is used to survey aerosol content over Paris. ► Nighttime lidar measurements are inverted with a Thikonov regularization scheme. ► Dichotomous algorithm developed to perform daytime inversions every hour. ► Monte Carlo simulations performed to assessed uncertainties on LR with each method. ► Lidar ratios of 48, 45 and 85 sr found for volcanic, dust and pollution aerosols.
Keywords: UV N2-Raman lidar; Lidar ratio; Iterative approach; Aerosol; Volcanic ash; Optical properties;
Residual levels and identify possible sources of organochlorine pesticides in Korea atmosphere by Jin Soo Park; Sun Kyoung Shin; Woo Il Kim; Byung Hoon Kim (7496-7502).
The nationwide monitoring program was established in 2008 to monitor of persistent organic pollutants (POPs) in Korea. Under this program, it was observed air concentrations of organochlorine pesticides (OCPs) at 37 sites from January to October of 2008, to determine the residue levels and identify possible sources in Korea atmosphere. Samples of OCPs including HCB, aldrin, dieldrin, endrin, p,p′-DDT, o,p′-DDT, p,p′-DDE, o,p′-DDE, p,p′-DDD, o,p′-DDD, trans-chlordane, cis-chlordane, trans-nonachlor, cis-nonachlor, oxychlordane, heptachlor, heptachlor epoxide were collected with high volume air sampler and analyzed by HRGC/HRMS. The concentrations were in the range of 41.2–344.3 pg m−3 for HCB, ND–47.55 pg m−3 for DDTs (sum of p,p′-DDT, o,p′-DDT, p,p′-DDE, o,p′-DDE, p,p′-DDD, o,p′-DDD), ND–38.97 pg m−3 for chlordanes (sum of trans-chlordane, cis-chlordane, trans-nonachlor, cis-nonachlor, oxychlordane), ND–9.19 pg m−3 for heptachlors (sum of heptachlor and heptachlor epoxide) and ND–4.32 pg m−3 for dieldrin. The predominant compound in air was HCB. However, HCB itself has not ever been registered and used as a pesticide in Korea. The elevated concentration of HCB in Korea might be contributed to geographical location and long range transport. For DDTs, it was found that no more fresh input occurred recently and technical type DDTs was prevailing in Korea. Higher concentration of chlordane was observed in winter, which was contributed to the fresh input technical chlordane and long range transport. Relatively lower levels of heptachlor and dieldrin despite much more consumption than other pesticides were resulted from shorter half-lives in environment.
Keywords: Organochlorine pesticides; Air; Concentration; Source; Korea;
Comparison and trend study on acidity and acidic buffering capacity of particulate matter in China by Lihong Ren; Wei Wang; Qingyue Wang; XiaoYang Yang; Dagang Tang (7503-7519).
The acidity of about 2000 particulate matter samples from aircraft and ground-based monitoring is analyzed by the method similar to soil acidity determination. The ground-based samples were collected at about 50 urban or background sites in northern and southern China. Moreover, the acidic buffering capacity of those samples is also analyzed by the method of micro acid-base titration. Results indicate that the acidity level is lower in most northern areas than those in the south, and the acidic buffering capacity showed inverse tendency, correspondingly. This is the most important reason why the pollution of acidic-precipitation is much more serious in Southern China than that in Northern China. The acidity increases and the acidic buffering capacity drops with the decreasing of the particle sizes, indicating that fine particle is the main influencing factor of the acidification. The ionic results show that Ca salt is the main alkaline substance in particulate matter, whereas the acidification of particulate matter is due to the SO2 and NOx emitted from the fossil fuel burning. And among of them, coal burning is the main contributor of SO2, however the contribution of NOx that emitted from fuel burning of motor vehicles has increased in recent years. By comparison of the experimental results during the past 20 years, it can be concluded that the acid precipitation of particulate matter has not been well controlled, and it even shows an increasing tendency in China lately. The acid precipitation of particulate matter has begun to frequently attack in part of the northern areas. Multiple regression analysis indicates that coefficient value of the ions is the lowest at the urban sites and the highest at the regional sites, whereas the aircraft measurement results are intermediate between those two kinds of sites.► The acidity of about 2000 particulate matter samplers from aircraft and ground-based monitoring is analyzed. ► The ground-based samples were collected at about 50 urban or background sites in northern and southern China. ► The acidity increases and the acidic buffering capacity drops with the decreasing of the particle sizes. ► The acid precipitation has not been well controlled, and it even shows an increasing tendency in China lately.
Keywords: Particulate matter; TSP; PM10; PM2.5; Acidity; Buffering capacity; Acid precipitation; China;
Emissions of H2 and CO from leaf litter of Sequoiadendron giganteum, and their dependence on UV radiation and temperature by L. Derendorp; J.B. Quist; R. Holzinger; T. Röckmann (7520-7524).
Senescent and dead plant material releases carbon monoxide (CO), methane and higher hydrocarbons upon heating or irradiation with UV, but emissions of hydrogen (H2) have not been reported. This study investigated whether leaf litter is able to emit H2 and which factors control the possible emissions. In addition, the emission of CO from leaf litter was measured and compared to previous studies. H2 was released from leaf litter of sequoia (Sequoiadendron giganteum) in detectable amounts at temperatures above 45 °C, whereas CO was also emitted at ambient temperature. The emission rates of both H2 and CO increased with temperature according to the Arrhenius relation. UV radiation can induce emissions of both H2 and CO. However, UV induced H2 was only emitted under anoxic conditions, while CO emissions were higher in synthetic air, but strongly reduced in absence of oxygen.
Keywords: Hydrogen (H2); Carbon monoxide; Leaf litter;
A tracer experiment study to evaluate the CALPUFF real time application in a near-field complex terrain setting by Huiling cui; Rentai Yao; Xiangjun Xu; Cuntian Xin; jinming Yang (7525-7532).
CALPUFF is an atmospheric source-receptor model recommended by the US Environmental Protection Agency (EPA) for use on a case-by-case basis in complex terrain and wind condition. As the bulk of validation of CALPUFF has focused on long-range or short-range but long-term dispersion, we can not gauge the reliability of the model for predicting the short-term emission in near-field especially complex terrain, and sometimes this situation is important for emergency emission. To validate the CALPUFF’s application in such condition, we carried out a tracer experiment in a near-field complex terrain setting and used CALPUFF atmospheric dispersion model to simulate the tracer experiment in real condition. From the centroid trajectory comparison of predictions and measures, we can see that the model can correctly predict the centroid trajectory and shape of tracer cloud, and the results also indicate that sufficient observed weather data only can develop a good wind field for near-field. From the concentration comparison in each arc, we can see the model underestimate horizontal extent of tracer puff and can not reflect the irregular characters showed in measurements. The result of global analysis is FOEX of −25.91%, FA2 of 27.06%, FA5 of 61.41%. The simulations shows that the CALPUFF can simulate the position and direction of tracer cloud in near-field complex terrain but underestimate over measurements especially in peak concentrations.
Keywords: CALPUFF; Tracer experiment; Complex terrain; Near-field dispersion;
Reply to “Comment on estimating historical landfill quantities to predict methane emissions” by Sean Lyons; Liam Murphy; Richard S.J. Tol (7533-7534).
Corrigendum to “Investigation on the potential generation of ultrafine particles from the tire–road interface” [Atmos. Environ. 45 (2011) 6172–6179] by Marcel Mathissen; Volker Scheer; Rainer Vogt; Thorsten Benter (7535).
“A cellphone based system for large-scale monitoring of black carbon” Atmos. Environ. 45(26) pp. 4481–4487 (2011) by N. Ramanathan; M. Lukac; T. Ahmed; A. Kar; P.S. Praveen; T. Honles; I. Leong; I.H. Rehman; J.J. Schauer; V. Ramanathan (7536).