Atmospheric Environment (v.42, #22)
Editorial board (i).
Comparison of wet-only and bulk deposition at Chiang Mai (Thailand) based on rainwater chemical composition by Somporn Chantara; Nawarut Chunsuk (5511-5518).
The chemical composition of 122 rainwater samples collected daily from bulk and wet-only collectors in a sub-urban area of Chiang Mai (Thailand) during August 2005–July 2006 has been analyzed and compared to assess usability of a cheaper and less complex bulk collector over a sophisticated wet-only collector. Statistical analysis was performed on log-transformed daily rain amount and depositions of major ions for each collector type. The analysis of variance (ANOVA) test revealed that the amount of rainfall collected from a rain gauge, bulk collector and wet-only collector showed no significant difference (∝=0.05). The volume weight mean electro-conductivity (EC) values of bulk and wet-only samples were 0.69 and 0.65 mS/m, respectively. The average pH of the samples from both types of collectors was 5.5. Scatter plots between log-transformed depositions of specific ions obtained from bulk and wet-only samples showed high correlation (r>0.91). Means of log-transformed bulk deposition were 14% (Na+ and K+), 13% (Mg2+), 7% (Ca2+), 4% (NO3 −), 3% (SO4 2− and Cl−) and 2% (NH4 +) higher than that of wet-only deposition. However, multivariate analysis of variance (MANOVA) revealed that ion depositions obtained from bulk and wet-only collectors were not significantly different (∝=0.05). Therefore, it was concluded that a bulk collector can be used instead of a wet-only collector in a sub-urban area.
Keywords: Acid precipitation; Wet deposition; Bulk deposition; Chemical composition;
Modeling spatial variability of airborne levoglucosan in Seattle, Washington by J.G. Su; M. Buzzelli; M. Brauer; T. Gould; T.V. Larson (5519-5525).
In many urban areas residential wood burning is a significant source of wintertime fine particles and has an important influence on spatial variability of particle concentrations. Although woodsmoke fine particles are usually within the size range thought to be most damaging to human health, their chemical composition is different from those derived from fossil fuel combustion, on which most health-effects studies have focused. Development of an exposure assessment tool for identification of the spatial distribution of woodsmoke will improve future epidemiological studies that rely on such intra-urban variability. For land-use regression (LUR) models, uniform buffers (i.e., circular areas or grids) are often applied to model spatial variability of pollutant concentrations. However, when winter woodsmoke levels are expected to be at a maximum, the surface wind is influenced by drainage flow and a given receptor location is systematically downwind of uphill sources. This research extends our previously developed GIS-based catchment air flow modeling approach of wintertime average woodsmoke levels to Seattle, WA, with emphasis on the use of levoglucosan as a marker of wood combustion. We further compare our regression model to a historical data set of mobile light-scattering measurements taken 15–20 years ago. Although fine particle levels have decreased significantly over this period, the spatial models for current levoglucosan (R 2=0.57) and historical light scattering (R 2=0.49) predict similar spatial patterns. This research demonstrates the usefulness of using both light scattering and levoglucosan to model ambient woodsmoke concentrations and further demonstrates the usefulness of the concept of drainage catchments to identify elevated, persistent nighttime levels of fine particles.
Keywords: Land use regression; Woodsmoke; Levoglucosan; Light scattering; Catchment;
Assessment of the atmospheric fungal prevalence through field ergosterol measurement I—Determination of the specific ergosterol content in common ambient fungal spores and yeast cells by Jessica Y.W. Cheng; Arhur P.S. Lau; Ming Fang (5526-5533).
This and a companion paper report a means to assess fungal prevalence in ambient air by measuring the ergosterol concentration. The results are highly reproducible. Twelve species and strains of fungal spores and yeast cells commonly found in ambient air in the subtropics were cultured in the laboratory. Gas chromatography–mass spectrometry (GC–MS) was used to determine their ergosterol content. (1) The specific ergosterol content of the 12 species ranged from 0.047 to 9.919 pg (spore or yeast cell)−1. (2) It was found that the larger the surface area of the spore/yeast cell, the higher the specific ergosterol content. (3) The specific ergosterol content of the spores or cells increased during vegetative growth of the parent cells, but became steady once the parent had matured. (4) Ergosterol was found to decompose in autoclaved spores or yeast cells, but a substantial amount of the ergosterol remained. Therefore, ergosterol can be used to reflect both the viable and the non-viable fungal mass. In a companion paper, an empirical general conversion factor for determining fungal concentration from field ergosterol measurements is proposed.
Keywords: Specific ergosterol content; Fungal spores; Yeast cells; Ambient fungal species;
Assessment of the atmospheric fungal prevalence through field ergosterol measurement II: Establishing the conversion factor by Jessica Y.W. Cheng; Arthur P.S. Lau; Ming Fang (5534-5541).
A general empirical conversion factor for estimating ambient fungal prevalence from filter ergosterol concentration data is proposed. The derivation was based on 28 high-volume filter samples, each with six viable samples collected simultaneously, over a period of 6 months, and specific ergosterol content data previously determined for 12 common airborne fungal species. A number of simplifying assumptions were made to arrive at the weighted-average ergosterol content based on the specific ergosterol content and the corresponding fraction in the viable sample. The filter ergosterol concentrations and the viable counts varied by one order of magnitude, but the general empirical conversion factor derived from the weighted-average ergosterol content data was relatively constant at 0.191±0.040 pg spore−1 (mean±s.d., n=28). Using this factor to calculate the total spore number concentrations for the 28 filter samples gave a mean value of 1211 spores m−3, which was not significantly different from the mean calculated from the individual weighted-average ergosterol values (1236 spores m−3). Comparison with literature reports confirmed that such conversion factors are experiment and environment specific.
Keywords: Ergosterol; Conversion factors; Fungal prevalence; Culturability;
Significant contributions of fungal spores to the organic carbon and to the aerosol mass balance of the urban atmospheric aerosol by Heidi Bauer; Elisabeth Schueller; Gert Weinke; Anna Berger; Regina Hitzenberger; Iain L. Marr; Hans Puxbaum (5542-5549).
Fungal spores are ubiquitous components of atmospheric aerosols and are therefore also contributors to the organic carbon (OC) component and to the mass of PM10 (PM—particulate matter) aerosols. In this study we use spore counts and an experimentally derived factor of 13 pg C and of 33 pg fresh weight per spore for assessing quantitatively the contribution to OC and PM10. The concentrations of airborne fungal spores were determined at a suburban (Schafberg) and a traffic-dominated urban site (Rinnböckstrasse) in Vienna, Austria, during spring and summer. Fungal spores OC ranged from 22 to 677 ng m−3 with a summer mean value of around 350 ng m−3 at the suburban site and 300 ng m−3 at the urban traffic site. At the suburban site fungal spores contributed on average 6% in spring and 14% in summer to aerosol OC mass concentration. At the traffic-dominated site fungal spores accounted for 2% of OC in spring and for 8% in summer. The fungal contribution to PM10 was also notable and amounted to 3% and 7% at the suburban and to 1% and 4% at the urban site in spring and summer, respectively. Impactor measurements of OC at the suburban site showed that in summer fungal spores were predominant contributors to the coarse aerosol OC, and accounted on average for 60% of the OC in the PM2−10 fraction. Fungal spores thus can be regarded as main components to PM10, total OC and, most importantly, coarse OC even in urban areas.
Keywords: Fungal spores; Organic carbon; Bioaerosol; PM10;
PAHs in Stockholm window films: Evaluation of the utility of window film content as indicator of PAHs in urban air by Maria Unger; Örjan Gustafsson (5550-5557).
The thin organic film that builds up on the exterior surface of windows has been proposed as a ubiquitously available passive sampler for semi-volatile organic contaminants (SOCs) in urban air. Readily available school windows were sampled in Stockholm city centre and suburban locations in both winter and summer season to evaluate the putative usefulness of this matrix for assessing the integrated load of urban air pollution by polycyclic aromatic hydrocarbons (PAHs). The window-area normalised concentrations indicated more PAH contamination in the winter than in the summer in both the city centre and suburban locations, with highest concentrations in the city centre in the winter (∑PAH43 451–467 ng m−2). However, normalising the PAH load to the amount of fatty window film, as measured by extractable organic matter (EOM), gave a more homogeneous picture with the EOM-normalised PAH load being inseparable both between summer and winter and between city centre and suburban locations.To evaluate the possibility of quantitatively employing urban window films as a means to provide predicted environmental concentrations of PAHs in air (PECair), window film–air partition coefficients of PAHs were estimated using a set of coupled linear free energy relationships and physico-chemical properties of PAHs. Assuming dynamic equilibria between PAHs in air and dissolved in the window film, the obtained PECair from the window films were consistently overestimating the urban vapour-phase PAH concentrations by factors 4–135. This discrepancy is quantitatively consistent with a strong and overwhelming association with black carbon aerosol particles accumulated in the window film. For SOCs that have a lower tendency to associate with black carbon, bulk window film concentrations may work better than for PAHs to estimate their vapour-phase concentrations in urban air.
Keywords: Organic window film; Polycyclic aromatic hydrocarbon; Linear free energy relationship; Lipid–air partitioning; Black carbon;
Production of potentially hazardous respirable silica airborne particulate from the burning of sugarcane by Jennifer S. Le Blond; Ben J. Williamson; Claire J. Horwell; Alex K. Monro; Caroline A. Kirk; Clive Oppenheimer (5558-5568).
In some areas of the world where agricultural burning is practised, the airborne particles produced have been linked to respiratory disease in humans. Here, we investigate the abundance and form of silica (SiO2) minerals found within ash and aerosol produced by the experimental burning of sugarcane. Samples of sugarcane leaf were incinerated over a range of temperatures, time scales and airflow conditions, the latter to investigate the effects of wind and updrafts during natural fires. The silica content of the residual ash (from still air simulations) was measured using an improved wet chemical methodology, described here. This indicated that the release of silica from the plant material into the atmosphere increases with increasing temperature of combustion. Airborne particulate, sampled using air-pump-filter apparatus, was characterised using scanning electron microscopy (SEM) with automated image and elemental analysis. For airborne particulate formed at 1100 °C (with airflow), 17% of the particles are in the respirable size fraction (<4 μm in diameter) and contain silica. From X-ray diffraction (XRD) analysis, a component of this silica is present as the potentially toxic polymorph cristobalite. For the residual ash, samples produced with no additional airflow were found to contain cristobalite, however none could be identified in ash formed with an airflow. It is considered likely that this is due to release of cristobalite to the atmosphere (as sampled on filters). This pilot study shows that potentially toxic particles could be released during sugarcane burning and reinforces the need for further study into the emissions and re-suspension of ash from the burning of biomass.
Keywords: Biomass burning; Cristobalite; Respirable particles; Silica; Sugarcane;
Evidence for large-scale transport of biomass burning aerosols from sunphotometry at a remote South African site by H. Winkler; P. Formenti; D.J. Esterhuyse; R.J. Swap; G. Helas; H.J. Annegarn; M.O. Andreae (5569-5578).
We present the results of sunphotometry measurements at De Aar, a remote site on the central South African plateau, during and after the intensive dry season field campaign of SAFARI 2000. We determine a 6-month-long time series of aerosol optical depths over the site. Twelve haze events are identified, for which we derive Angström exponents and their derivatives, and, through cross-plots of these parameters, typical aerosol sizes and levels of hydration. These results, in conjunction with meteorological data and air trajectory calculations, show biomass burning to be the main aerosol generating source for 8 of the 12 events, and responsible for the 5 cases with the highest turbidity. While the bulk of the biomass emission is clearly of African origin, we identify several possible South Atlantic crossings of aged smoke from fires in the Amazon basin. We define the southern edge of the main aerosol transport route over southern Africa during the austral winter. We estimate that, for the half-year investigated, 84% of the losses of visible solar irradiation over our experimental location are caused by biomass burning haze, and conclude that these types of aerosols have the most critical impact on solar irradiation and atmospheric albedo over the entire southern Africa.
Keywords: Aerosol properties; Sun photometry; Angström parameter; Africa;
Methane emissions from MSW landfill with sandy soil covers under leachate recirculation and subsurface irrigation by Houhu Zhang; Pinjing He; Liming Shao (5579-5588).
CH4 emissions and leachate disposal are recognized as the two major concerns in municipal solid waste (MSW) landfills. Recently, leachate recirculation was attempted to accelerate land-filled waste biodegradation and thus enhanced landfill gas generation. Leachate irrigation was also conducted for volume reduction effectively. Nevertheless, the impacts of leachate recirculation and irrigation on landfill CH4 emissions have not been previously reported. A field investigation of landfill CH4 emissions was conducted on selected sandy soil cover with leachate recirculation and subsurface irrigation based on whole year around measurement. The average CH4 fluxes were 311±903, 207±516, and 565±1460 CH4 m−2 h−1 from site A without leachate recirculation and subsurface irrigation, lift B2 with leachate subsurface irrigation, and lift B1 with both leachate recirculation and subsurface irrigation, respectively. Both gas recovery and cover soil oxidation minimized CH4 emissions efficiently, while the later might be more pronounced when the location was more than 5 m away from gas recovery well. After covered by additional clay soil layer, CH4 fluxes dropped by approximately 35 times in the following three seasons compared to the previous three seasons in lift B2. The diurnal peaks of CH4 fluxes occurred mostly followed with air or soil temperature in the daytimes. The measured CH4 fluxes were much lower than those of documented data from the landfills, indicating that the influences of leachate recirculation and subsurface irrigation on landfill CH4 emissions might be minimized with the help of a well-designed sandy soil cover. Landfill cover composed of two soil layers (clay soil underneath and sandy soil above) is suggested as a low-cost and effective alternative to minimize CH4 emissions.
Keywords: Municipal solid waste landfill; CH4 emissions; Leachate recirculation; Subsurface irrigation; Microbial CH4 oxidation;
Constant volume balloons measurements in the urban Marseille and Fos–Berre industrial ozone plumes during ESCOMPTE experiment by Bruno Bénech; Agustin Ezcurra; Marie Lothon; Frédérique Saïd; Bernard Campistron; Fabienne Lohou; Pierre Durand (5589-5601).
ESCOMPTE programme aims at studying the emissions of primary pollutants in industrial and urban areas, their transport, diffusion and transformation in the atmosphere. This experiment, carried out in southeast France, can be used to validate and to improve meteorological and chemical mesoscale models. One major goal of this experiment was to follow the pollutant plumes, and to investigate its thermodynamic and physico-chemical time evolution. This was realized by means of constant volume balloons, located by global position satellite (GPS) and equipped with thermodynamic and ozone sensors, flying at constant density levels. During the two ESCOMPTE campaigns that took place in June and July 2000 and 2001, 40 balloons were launched, 17 of them equipped with ozone sensors during the day from 0800 to 1800 UTC. Balloons’ altitudes flight levels ranged between 400 and 1200 m altitude with Mistral (northerly synoptic flow) and Sea Breeze (southerly breeze) conditions. The atmospheric boundary layer (ABL) topography of the experimental domain is complex and varies strongly from day to day. Its depth presents a large gradient from the sea coast to the north part of the ESCOMPTE domain, and also more complex variability within the domain. The balloons’ trajectories describe the evolution of the pollutant plume emitted from the industrial area of Fos-Berre or from the Marseille urban area. Constant volume balloons give a good description of the trajectories of these two plumes. The balloons, which fly at an isopicnic level, cross different atmospheric layers chiefly depending on the ABL height in relation with the constant volume balloons flight level. Thus, each balloon flight is decomposed into different segments that correspond to the same atmospheric layer. In each segment, the ozone content variation is analyzed in relation to other thermodynamical parameters measured by the balloon and mainly to the vapor mixing ratio content. During ESCOMPTE campaign, the mean linear rate of chemical net ozone production at the top of the atmospheric boundary layer was found to be around 6 ppb h−1.
Keywords: Constant volume balloons; Urban ozone; Ozone production; ESCOMPTE;
Modeling hydrogen sulfide emissions across the gas–liquid interface of an anaerobic swine waste treatment storage system by Jessica Blunden; Viney P. Aneja; John H. Overton (5602-5611).
Hydrogen sulfide (H2S) is a colorless gas emitted during decomposition of hog manure that produces an offensive “rotten egg” smell and is considered a toxic manure gas. In the southeastern United States, anaerobic waste treatment lagoons are widely used to store and treat hog excreta at commercial hog farms. Hydrogen sulfide is produced as manure decomposes anaerobically, resulting from the mineralization of organic sulfur compounds as well as the reduction of oxidized inorganic sulfur compounds by sulfur-reducing bacteria. The process of H2S emissions from anaerobic waste treatment lagoons are investigated utilizing a two-film model with three different modeling approaches: Coupled Mass Transfer with Chemical Reactions Model with the assumption (1) pH remains constant in the liquid film (MTCR Model I) and (2) pH may change throughout the liquid film due to diffusion processes that occur within the film (MTCR Model II); and (3) a Mass Transfer Model which neglects chemical reactions (MTNCR Model) in the gas and liquid films.Results of model predictions are consistent with previous works, which show that flux is largely dependent on the physicochemical lagoon properties including sulfide concentration, pH, and lagoon temperature. Air temperature and low wind velocities (e.g., <3.25 m s−1) have negligible impact on flux. Results also indicate that flux values decrease with increased film thickness. The flux was primarily influenced by variations in the liquid film thickness, signifying that the H2S flux is driven by liquid-phase parameters. Model results were compared with H2S flux measurements made at a swine waste treatment storage lagoon in North Carolina using a dynamic emission flux chamber system in order to evaluate model accuracy in calculating lagoon H2S emissions. The MTCR Model II predicted the highest increase in emission rates as aqueous sulfide concentration was increased. The MTNCR Model showed the highest dependence on pH. All three models showed good agreement in diurnal comparison with flux measurements; however, each model significantly over predicted the measured flux rates. The MTNCR Model estimates were closest to experimental values, predicting 3–35 times the actual measured values.
Keywords: Two-film theory; Hydrogen sulfide; Process-based model; Lagoon flux; Mass transfer;
Atmospheric water-soluble organic carbon measurements at Summit, Greenland by Casey H. Anderson; Jack E. Dibb; Robert J. Griffin; Gayle S.W. Hagler; Michael H. Bergin (5612-5621).
The recently discovered active photochemistry in the surface layers of polar snow may complicate the interpretation of organic compounds found in ice cores. In order to better understand the transformation and cycling of organic species in Arctic surface snow, measurements of water-soluble organic carbon (WSOC) in the gas (WSOCG) and particle (WSOCP) phases were made during the 2006 summer season at Summit, Greenland. These samples represent the first direct, simultaneous measurements of both WSOCG and WSOCP at Summit. From early June to early July, WSOCG and WSOCP concentrations at 150 cm above the snow averaged 667 and 194 ng C m−3, respectively. This value for WSOCG is very similar in magnitude to the sum of acetic and formic acid gas concentrations measured during previous summers at Summit, suggesting that these two monocarboxylic acids constitute a significant fraction of the mass of measured WSOCG. Firn air measurements of WSOCG revealed concentrations within the snowpack nearly an order of magnitude greater than those in the air just above the snow. During one period, four out of five consecutive nights showed concurrent decreases in WSOCG and increases in WSOCP, likely resulting from temperature-dependent gas-to-particle partitioning, as these episodes occurred during the coldest part of the early morning.
Keywords: Greenland ice sheet; Water-soluble organic carbon; Gas–particle partitioning;
Physical properties of particulate matter (PM) from late model heavy-duty diesel vehicles operating with advanced PM and NO x emission control technologies by Subhasis Biswas; Shaohua Hu; Vishal Verma; Jorn D. Herner; William H. Robertson; Alberto Ayala; Constantinos Sioutas (5622-5634).
Emission control technologies designed to meet the 2007 and 2010 emission standards for heavy-duty diesel vehicles (HDDV) remove effectively the non-volatile fraction of particles, but are comparatively less efficient at controlling the semi-volatile components. A collaborative study between the California Air Resources Board (CARB) and the University of Southern California was initiated to investigate the physicochemical and toxicological characteristics of the semi-volatile and non-volatile particulate matter (PM) fractions from HDDV emissions. This paper reports the physical properties, including size distribution, volatility (in terms of number and mass), surface diameter, and agglomeration of particles emitted from HDDV retrofitted with advanced emission control devices. Four vehicles in combination with six after-treatment devices (V-SCRT®, Z-SCRT®, CRT®, DPX, Hybrid-CCRT®, EPF) were tested under three driving cycles: steady state (cruise), transient (urban dynamometer driving schedule, UDDS), and idle. An HDDV without any control device is served as the baseline vehicle.Substantial reduction of PM mass emissions (>90%) was accomplished for the HDDV operating with advanced emission control technologies. This reduction was not observed for particle number concentrations under cruise conditions, with the exceptions of the Hybrid-CCRT® and EPF vehicles, which were efficient in controlling both—mass and number emissions. In general, significant nucleation mode particles (<50 nm) were formed during cruise cycles in comparison with the UDDS cycles, which emit higher PM mass in the accumulation mode. The nucleation mode particles (<50 nm) were mainly internally mixed, and evaporated considerably between 150 and 230 °C. Compared to the baseline vehicle, particles from vehicles with controls (except of the Hybrid-CCRT®) had a higher mass specific surface area.
Keywords: HDDV; Particulate; Control; Nucleation; Agglomeration; Volatility;
Urban heat island effect and its impact on boundary layer development and land–sea circulation over northern Taiwan by Chuan-Yao Lin; Fei Chen; J.C. Huang; W.-C. Chen; Y.-A. Liou; W.-N. Chen; Shaw-C. Liu (5635-5649).
The impact of the urban heat island (UHI) effect on environmental and regional climate has been receiving wide attention in recent decades. Taiwan, especially Taipei (located in northern Taiwan), is experiencing a significant UHI effect due to its high population density and the uniqueness of the geographic structure. In order to evaluate the impacts of urbanization and UHI effect over northern Taiwan, a next generation mesoscale model, Weather Research and Forecasting (WRF) model coupled with the Noah land surface model and Urban Canopy model (UCM), was used to study this issue.By using the WRF–Noah–UCM model, it has significantly improved our simulation results for the prediction of the UHI effect, boundary layer development, and land sea breeze. Observations of weather stations and Lidar showed that the near surface air temperature was nearly 34–35 °C and the boundary layer height was nearly 1500 m around noon in Taipei on 17 June 2006. Around midnight, the air temperature ranged from 26 to 28 °C. Our model can predict well for boundary layer development during the daytime and the UHI effect in northern Taiwan. Sensitivity tests indicate that the anthropogenic heat (AH) plays an important role for the boundary layer development and UHI intensity in the Taipei area, especially during nighttime and early morning. When we increase AH by 100 W m−2 in the model, the average surface temperature could increase nearly 0.3 °C in Taipei. Furthermore, we found the UHI effect also has a significant impact on land sea circulation. It could enhance the sea breeze in the daytime and weaken the land breeze during the nighttime and hence had a significant impact on the air pollution diffusion in northern Taiwan.
Keywords: Urban heat island; WRF/Noah/UCM model; Boundary layer; Taiwan;
Development and application of a computationally efficient particulate matter apportionment algorithm in a three-dimensional chemical transport model by Kristina M. Wagstrom; Spyros N. Pandis; Greg Yarwood; Gary M. Wilson; Ralph E. Morris (5650-5659).
An on-line and an off-line version of a computationally efficient particulate matter source apportionment algorithm have been developed and compared using the three-dimensional chemical transport model PMCAMx. Both versions of the algorithm use source specific-species that track the contributions of source locations or source classes. The two versions showed a good agreement with each other and with more accurate, computationally demanding methods. The off-line algorithm (Particulate Source Apportionment Technology, PSAT) is simpler to implement, has a lower computational cost and is suitable for a range of source apportionment studies. As a first application, PSAT was used to investigate the contribution of power plant SO2 emissions to particulate sulfate concentrations in the Eastern United States. The impact of the transport of SO2 emissions from the Chicago, IL area and the impact of these emissions on particulate sulfate concentration in surrounding areas were also studied as a second application. The implementation of PSAT for the SO2/particulate sulfate system only resulted in a 1% increase in computation time over the base simulation. The algorithm provides a computationally efficient platform for the study of pollutant transport and source contributions on regional scales.
Keywords: Source apportionment; Atmospheric aerosol modeling; Regional air quality;
Factors affecting the indoor concentrations of carbonaceous aerosols of outdoor origin by Melissa M. Lunden; Thomas W. Kirchstetter; Tracy L. Thatcher; Susanne V. Hering; Nancy J. Brown (5660-5671).
A field study was conducted in an unoccupied single-story residence in Clovis, California, to provide data to address issues important to assess the indoor exposure to particles of outdoor origin. Measurements of black and organic carbonaceous aerosols were performed using a variety of methods, resulting in both near real-time measurements as well as integrated filter-based measurements. Comparisons of the different measurement methods show that it is crucial to account for gas phase adsorption artifacts when measuring organic carbon (OC). Measured concentrations affected by the emissions of organic compounds sorbed to indoor surfaces imply a higher degree of infiltration of outdoor organic carbon aerosols into the indoor environment for our unoccupied house. Analysis of the indoor and outdoor data for black carbon (BC) aerosols show that, on average, the indoor concentration of black carbon aerosols behaves in a similar manner to sulfate aerosols. In contrast, organic carbon aerosols are subject to chemical transformations indoors that for our unoccupied home, resulted in lower indoor OC concentrations than would be expected by physical loss mechanisms alone. These results show that gas to particle partitioning of organic compounds, as well as gas to surface interactions within the residence, are an important process governing the indoor concentration to OC aerosols of outdoor origin.
Keywords: Indoor air quality; Aerosols; Carbon; Adsorption artifact; Gas-to-particle partitioning;
Water adsorption and cloud condensation nuclei activity of calcite and calcite coated with model humic and fulvic acids by Courtney D. Hatch; Kelly M. Gierlus; Jennifer D. Schuttlefield; Vicki H. Grassian (5672-5684).
Recent studies have shown that organics can alter the water adsorption and cloud condensation nuclei (CCN) activity of common deliquescent species in the Earth's atmosphere. However, very little is known about the effect of organics on water adsorption and CCN activity of insoluble nuclei, such as mineral dust aerosol. A large fraction of unidentified organic material in aerosol particles is composed of poly-acidic compounds resembling humic substances. The presence of these humic-like substances (HULIS) can alter the water adsorption and CCN activity of mineral dust aerosol. We have measured the CCN activity of model humic and fulvic acids and of mineral dust particles coated with these substances in the laboratory. We find that coatings of humic and fulvic acids on calcite particles significantly increases water adsorption compared to uncoated particles. CCN measurements indicate that humic- or fulvic acid-coated calcite particles are more CCN active than uncoated calcite particles. Additionally, thicker coatings of humic or fulvic acids appear to result in more efficient CCN activity. Thus, mineral dust particles coated with high molecular weight organic materials will take up more water and become more efficient CCN in the atmosphere than uncoated mineral dust particles, potentially altering the effect of mineral dust on the Earth's climate. In addition to the experimental results, we have explored a newly modified Köhler theory for predicting the CCN activity of insoluble, wettable particles based on multi layer water adsorption measurements of calcite.
Keywords: Humic acid; Fulvic acid; HULIS; Mineral dust; CCN and water adsorption;
Investigation of VOC emissions from indoor and outdoor painting processes in shipyards by Ugur Bugra Celebi; Nurten Vardar (5685-5695).
Volatile organic compounds (VOCs) from painting solvents are one of the most important sources of pollutant outputs for the shipbuilding and ship repair industry. Two ships of equal tonnage with the same painted area as each other, which were built in Turkish shipyards, are compared in terms of VOCs produced during painting and coating. Total area of all painted surfaces and total paint consumption of a 3500 deadweight tonne (DWT) oil/chemical tanker and a general cargo ship are calculated. An improved model for calculating the surface emissions of VOCs from painting and coating processes is utilized. Material balance emission estimation approach is employed to calculate the amount of VOCs, since it is used most often where a relatively large amount of material is emitted during use, and/or all air emissions are uncaptured. For both ships calculated VOCs are presented in figures. For the years 2005 and 2006 the total deadweight tonnage of ships delivered in Tuzla region, where 42 shipyards are located, is known. Therefore, a linear estimation is made to guess the total annual VOC emissions caused by painting operations. Finally, this information is used to project the total amount of VOCs emitted to the atmosphere for the year 2010.
Keywords: Pollution sources; Volatile organic compounds (VOCs); Shipbuilding and ship repair industry; Indoor and outdoor painting; Turkey;
Partitioning characteristics of PCBs in urban surface films by Rosa W. Wu; Tom Harner; Miriam L. Diamond; Bryony Wilford (5696-5705).
Urban areas are characterized by impervious surfaces on which a thin surface film layer forms. The film is an environmental compartment whereby semi-volatile organic compounds partition between the organic phase of the film and the ambient air. This study investigates the partitioning of polychlorinated biphenyls (PCBs) between surface films and ambient air. The film–air partition coefficient (K fa) was calculated through laboratory experiments using ambient film samples, and then plotted against the log of the octanol–air partition coefficient (K oa). The resultant log–log relationship is analogous to that between K oa and K p (gas–particle partition coefficient) where the latter has been measured for many compound classes, and thus, K fa can be used in models that consider the impact of the surface film on chemical dynamics. Ethylene vinyl acetate (EVA) was investigated as a surrogate film and EVA–air partition coefficients (K EVA–air) values were measured. The relationship between log K fa and log K EVA–air is stronger than that between log K fa and log K oa, which leads to the preliminary conclusion that EVA may be a more suitable surrogate for ambient surface films than octanol. Film–air partition quotients (Q fa) were derived based on field measurements of PCBs in the ambient air and concentrations in surface films. Q fa depends not only on the characteristics of the organic phase, but also on external factors, including but not limited to, temperature and ambient air concentrations. Finally, differences in PCB partitioning between film collected at a rural site versus an urban site highlights the importance of the composition of the organic bulk phase in determining chemical sorption into and subsequent volatilization out of the surface films.
Keywords: Surface film; PCBs; Partitioning;
Lightning-produced NO x budget over the Highveld region of South Africa by Matthew E. Ojelede; Harold J. Annegarn; Colin Price; Melanie A. Kneen; Philip Goyns (5706-5714).
Measurements of lightning events recorded by a lightning position and tracking system (LPATS) were used to estimate the contribution of lightning to the nitrogen oxide (NO x ) burden over the Highveld region (taken as the 4° area, Lat. 25–29°, Lon. 27–31°) of South Africa. Lightning data collected in the year 2002, comprising a total of 2 417 074 cloud-to-ground (CG) strokes, were analyzed. Lightning strokes were grouped into flashes by considering strokes occurring within radii of 10 km and time intervals of 1 s apart as belonging to the same lightning flash. Making use of a production rate of 10×1016 molecules of NO J−1 and an energy dissipation of 6.7×109 J flash−1, an emission factor of 51.2 kg NO2 flash−1 was derived. This emission factor was employed to calculate the lightning-produced NO x (LNO x ) budget of 65 (2.8–200) kt NO2 yr−1 over the Highveld region. Our calculated LNO x is about 9% of reported NO x emissions from coal-fired power plants over the Highveld during 2002. An annual contour plot of LNO x showed that the distribution of NO x production over the Highveld is highly non-uniform, with high concentrations of LNO x over the central Highveld. These results indicate that in evaluating NO x and tropospheric ozone chemistry over the South African Highveld both natural lightning and industrial sources of NO x need to be taken into account.
Keywords: Lightning; LNO x ; LPATS; Nitrogen oxides;
Aircraft measurements of vertical ultrafine particles profiles over Northern China coastal areas during dust storms in 2006 by Wei Wang; Jianzhong Ma; Shiro Hatakeyama; Xiaoyu Liu; Yue Chen; Akinori Takami; Lihong Ren; Chunmei Geng (5715-5720).
The vertical distribution of ultrafine particles over Northern China coastal areas was measured by aircraft equipped with a high space–time resolution instrument during dust storms in spring of 2006. Three different types of conditions were observed, i.e. dust storm, weak dust storm and non-dust storm. Results indicate that the number concentration of ultrafine particles can reach up to 1.2×105 cm−3 during weak dust storm. It is found that the peak of newly formed particle by nucleation appeared around 10 nm diameter. During the dust storms, the concentration of ultrafine particles was lower than those when no dust storms occurred, and the number concentration showed multiple-peak distribution, which needs further research. Our observational results may provide valuable information for recognizing the process and mechanism of air pollution in the Northern China area, and basic parameters for model calculation.
Keywords: Aircraft measurement; Vertical distribution; Ultrafine particles; Northern China;
Size-segregated analysis of PM10 at two sites, urban and rural, in Münster (Germany) using five-stage Berner type impactors by Johanna K. Gietl; Torsten Tritscher; Otto Klemm (5721-5727).
Airborne particulate matter was collected at two sites, using five-stage Berner type impactors. Their different exposures to the emission sources in Münster, Germany, was examined during a campaign in January 2006. The scope of this project was to identify the sources of particulate material with the help of size- and time-resolved chemical characterisation of the particle components. The major ions such as Ca2+, Cl−, Mg2+, Na+, NH4 +, NO3 −, SO4 2−, and carbon were analysed. The mean mass concentration of particulate matter was higher at the urban roadside than at the regional background (rural site). The main difference exists for the carbon concentration, which is in the city 1.8 times higher than in the surrounding area. The ion concentrations showed identical concentration levels at both sites, with slightly higher concentrations at the roadside, due to Na+, Cl−, and Ca2+. The mass concentrations of particulate matter vary both between the sites and with time. At daytime, clearly higher amounts of particulate matter can be found at the roadside. Slightly enhanced concentrations of the secondary ions NH4+ and NO3− were found at night, but the difference is smaller than the daily increase of the particle mass due to carbon.
Keywords: Aerosol chemistry; Berner type impactor; Daytime/nighttime concentration; Size-segregated analysis;
New Directions: The impact of oceanic iron fertilisation on cloud condensation nuclei by Matthew T. Woodhouse; Graham W. Mann; Kenneth S. Carslaw; Olivier Boucher (5728-5730).