Atmospheric Environment (v.40, #21)

Source identification of ambient PM2.5 during summer inhalation exposure studies in Detroit, MI by Masako Morishita; Gerald J. Keeler; James G. Wagner; Jack R. Harkema (3823-3834).
Particulate air pollution is associated with cardiopulmonary morbidity and mortality in heavily populated urban centers of the United States. Because ambient fine particulate matter (aerodynamic diameter ⩽2.5 μm; PM2.5) is a complex mixture resulting from multiple sources and variable atmospheric conditions, it is difficult to identify specific components of PM2.5 that are responsible for adverse health effects. During four consecutive summers from 2000 to 2003 we characterized the ambient gaseous and PM2.5 air quality in an urban southwest Detroit community where childhood asthma hospitalization rates are more than twice the statewide average. Both integrated and continuous PM measurements together with gaseous air pollution measurements were performed using a mobile air research facility, AirCARE1, in which concurrent toxicological studies were being conducted.Chemical and physical characterizations of PM2.5 as well as receptor modeling using positive matrix factorization (PMF) were completed. Results from PMF indicated that six major sources contributed to the observed ambient PM2.5 mass during the summer months. Primary sources included (1) coal combustion/secondary sulfate aerosol, (2) motor vehicle/urban road dust, (3) municipal waste incinerators, (4) oil combustion/refineries, (5) sewage sludge incinerators, and (6) iron/steel manufacturing. Although the contribution of the coal/secondary sulfate aerosol source was greater than other factors, increased levels of urban PM2.5 from local combustion sources were also observed. In addition to characterization of ambient PM2.5 and their sources in southwest Detroit, this paper discusses possible associations of ambient PM2.5 from local combustion sources, specifically incinerator and refinery emissions and the observed adverse health effects during the inhalation exposure campaigns.
Keywords: PM2.5; Positive matrix factorization (PMF); Detroit; Trace elements; Receptor modeling;

Trace metal concentrations in street dusts of Dhaka city, Bangladesh by Faruque Ahmed; Hiroaki Ishiga (3835-3844).
Street dust samples were collected from differing areas (industrial—medium traffic density, commercial—high traffic density, and residential 1 and 2—low traffic density) in Dhaka City, Bangladesh, and their major oxide and trace element compositions were determined. The results show significant concentrations of Pb, Zn, Cu, Ni, and Cr in the Dhaka dusts, and some variations among the four sample groups. The samples in the commercial area had Pb concentrations two- to seven-fold those of the industrial and residential areas. Contents of Zn, Cu, Ni, and Cr in the industrial areas were greater than those in the commercial and residential areas. Levels of Pb, Cu, Ni, and Cr exceeded the maximum permissible limits for common soil. Increases in these anthropogenic trace metals in the surface environment can most likely be attributed to rapid urbanization and industrialization and increased vehicle emissions to the atmosphere. Elevated Zn concentrations in an industrial area can be ascribed to discharges of industrial activities, while elevated Zn abundances in commercial areas probably originate from traffic sources. The street dusts contaminated with Cu, Ni, and Cr occur mainly in industrial areas. However, Pb contamination in the Dhaka dusts is probably caused by Pb particles from vehicle emissions.
Keywords: Trace metal; Air pollution; Geochemistry; Dhaka dust;

Temperature-dependence study of the gas-phase reactions of atmospheric Cl atoms with a series of aliphatic aldehydes by Carlos A. Cuevas; Alberto Notario; Ernesto Martínez; José Albaladejo (3845-3854).
The reactions of Cl with a series of linear aldehydes: propanal (k 1), n-butanal (k 2), n-pentanal (k 3), n-hexanal (k 4) and n-heptanal (k 5), were investigated for the first time as a function of temperature in the range 265–381 K, by laser photolysis-resonance fluorescence. The obtained kinetic data were used to derive the Arrhenius expressions: k 1=(2.41±0.23) × 10−11 exp[(453 ± 54)/T], k 2=(3.09 ± 0.40) × 10−11 exp[(446 ± 77)/T], k 3=(4.17 ± 0.54) × 10−11 exp[(450 ± 80)/T], k 4=(7.91 ± 0.66) × 10−11 exp[(349 ± 51)/T] and k 5=(1.06 ± 0.20) × 10−10 exp[(306 ± 115)/T] (in units of cm3  molecule−1 s−1). To our knowledge, these are also the first absolute kinetic data reported for each of the reactions studied. The obtained rate coefficients are compared with previous studies carried out by relative techniques at room temperature, and also with the reactivity towards the OH radicals. The results are also discussed in terms of the structure–reactivity relationship. In addition, the atmospheric implications are discussed.
Keywords: Atmospheric chemistry; Chlorine atoms; Gas-phase reactions; Laser photolysis; Aldehydes;

Distribution of 7Be in surface air of Europe by A. Kulan; A. Aldahan; G. Possnert; I. Vintersved (3855-3868).
This study deals with long-term (span over three decades, 1972–2003) distribution of the cosmogenic isotope 7Be in surface air at 5 stations in Europe, extending from latitude 47°N to 68°N. The results suggest annual variability in all the data sets as well as a decrease in average 7Be activity with increasing latitude. Furthermore, a 9–10-year cyclical pattern is observed in the 7Be distribution, which is anticorrelated with the solar activity cycle. Our data also indicate a dynamic range of 7Be activity for each solar cycle and phase (maximum or minimum) which is higher at the middle compared to high-latitude regions. Additionally, about 10–20% relative deviation is observed in 7Be activity during solar maxima and minima compared to the total average 7Be. This feature indicates that some deviation in the worldwide 7Be activity data may relate to their acquisition, with respect to which part of a solar cycle they have been collected in (time span) and at which latitudinal spread. Estimate of 7Be flux onto European surface boundary layer vary from 0.4 to 0.9 × 1 0 10 atoms m - 2 yr - 1 which is strongly latitude dependent and our average value is comparable to the ∼ 0.7 – 0.8 × 1 0 10 atoms m - 2 yr - 1 across ocean and land.
Keywords: Atmosphere; Cosmogenic 7Be; Europe; Solar activity; Sweden;

In the present work, it is demonstrated that a single particle analytical technique, named low-Z particle electron probe X-ray microanalysis, is a practically useful tool for the study of heterogeneous reactions of mineral dust and sea-salts when this analytical technique was applied to a sample collected during an Asian Dust storm event. The technique does not require a special treatment of sample to identify particles reacted in the air. Also, quantitative chemical speciation of reacted particles can provide concrete information on what chemical reaction, if any, occurred for individual particles. Among overall 178 analyzed particles, the number of reacted particles is 81 and heterogeneous chemical reactions mostly occurred on CaCO3 mineral dust (54 particles) and sea-salts (26 particles). Several observations made for the Asian Dust sample in the present work are: (1) CaCO3 species almost completely reacted to produce mostly Ca(NO3)2 species, and CaSO4 to a much lesser extent. (2) When reacted particles contain CaSO4, almost all of them are internally mixed with nitrate. (3) Reacted CaCO3 particles seem to contain moisture when they were collected. (4) Some reacted CaCO3 particles have unreacted mineral species, such as aluminosilicates, iron oxide, SiO2, etc., in the core region. (5) All sea-salt particles are observed to have reacted in the air. Some of them were recrystallized in the air before being collected and they are observed as crystalline NaNO3 particles. (6) Many sea-salts were collected as water drops, and some of them were fractionally recrystallized on Ag collecting substrate. When sea-salts were not recrystallized on the substrate, they are found as particles internally mixed with NaNO3 and Mg(NO3)2, and in some cases SO4 and Cl species as additional anions.
Keywords: Mineral dust; Sea-salts; Heterogeneous reaction; Asian Dust; Single particle analysis; Low-Z particle EPMA;

Field measurements of desert dust deposition in Libya by Sarah L. O’Hara; Michèle L. Clarke; Mokhtar S. Elatrash (3881-3897).
North Africa is the largest global source of atmospherically transported desert dust. Advances in satellite technology allow dust plumes to be spatially and temporally monitored, but little is known of near-surface dust deposition, as field-based studies are rare. This paper presents results from a year-long field-based dust monitoring study of three zones across Libya, ranging from the Mediterranean coast to the Sahara desert. Monthly deposition rates are compared with meteorological data, particle size distribution and mineralogy to establish potential source areas. Comparison of annual dust deposition rates with previous studies in North Africa shows that areas of Libya have the highest dust deposition rates on record.
Keywords: Aeolian dust; Trapping; Libya; Sahara desert;

The trend of surface ozone in Taipei, Taiwan, and its causes: Implications for ozone control strategies by Charles C.-K. Chou; Shaw C. Liu; Chuan-Yao Lin; Chein-Jung Shiu; Ken-Hui Chang (3898-3908).
In recent years, the high levels of surface ozone have become a major air pollutant in Taiwan. Over the western plain of Taiwan, where most of the 23 million inhabitants live, the concentration of ozone increased substantially during the last ten years (1994–2003). This increase is puzzling as the emissions of ozone precursors, oxides of nitrogen (NO x ) and volatile organic compounds (VOCs) or non-methane hydrocarbon (NMHC) decreased significantly in the same period. An in-depth analysis focusing on “total oxidant” (estimated by O3+NO2) showed that its concentration remained essentially constant in Taipei, Taiwan, during that same ten year time period. Given that the regional tropospheric ozone is increasing, the constant oxidant level suggests that the oxidant production from photochemical reactions in Taipei should have been reduced to some extent, due to the reduction in emissions of ozone precursors. Consequently, the increasing trend in ozone was a result of the reduced titration by NO. These results are important to the formulation of ozone control strategies, especially for newly developed countries like Taiwan.
Keywords: Atmospheric oxidants; Titration effect; Surface ozone trend; Ozone control strategies;

Numerical study of single and two interacting turbulent plumes in atmospheric cross flow by M.R. Mokhtarzadeh-Dehghan; C.S. König; A.G. Robins (3909-3923).
The paper presents a numerical study of two interacting full-scale dry plumes issued into neutral boundary layer cross flow. The study simulates plumes from a mechanical draught cooling tower. The plumes are placed in tandem or side-by-side. Results are first presented for plumes with a density ratio of 0.74 and plume-to-crosswind speed ratio of 2.33, for which data from a small-scale wind tunnel experiment were available and were used to assess the accuracy of the numerical results. Further results are then presented for the more physically realistic density ratio of 0.95, maintaining the same speed ratio. The sensitivity of the results with respect to three turbulence models, namely, the standard kε model, the RNG kε model and the Differential Flux Model (DFM) is presented. Comparisons are also made between the predicted rise height and the values obtained from existing integral models.The formation of two counter-rotating vortices is well predicted. The results show good agreement for the rise height predicted by different turbulence models, but the DFM predicts temperature profiles more accurately. The values of predicted rise height are also in general agreement. However, discrepancies between the present results for the rise height for single and multiple plumes and the values obtained from known analytical relations are apparent and possible reasons for these are discussed.
Keywords: Buoyant plume; Multiple plumes; Cooling tower; CFD;

Rapid detection of airborne viruses by personal bioaerosol sampler combined with the PCR device by I.E. Agranovski; A.S. Safatov; A.A. Sergeev; O.V. Pyankov; V.A. Petrishchenko; M.V. Mikheev; A.N. Sergeev (3924-3929).
A new personal sampler had been previously developed and verified for monitoring of viable airborne viruses. The aims of this project were to investigate a possibility of the utilization of the polymerase chain reaction (PCR) method to speed up the time consuming analytical procedures and to evaluate a lower detection limit of the combined (sampler-PCR) device. Tenfold serial dilutions of the initial suspension of the Vaccinia virus were aerosolized in the chamber and airborne viruses were monitored by two simultaneously operating samplers. The results of monitoring were successfully obtained by a standard plaque assay (live microbes) and by the PCR method (total DNA). The corresponding calculations to identify the minimal detectable concentration in the ambient air were then performed. It was found that the minimal detectable concentration of airborne viruses in the ambient air depends on the sampling time. As demonstrated, such concentration should be at least 125×103  PFU m−3 for a sampling time of as short as 1 min. The detectable concentration decreases with the increase of the sampling time and reaches 25×103 and 10×103  PFU m−3 for 5 and 12.5 min of sampling respectively.
Keywords: Bioaerosol; Personal sampling; Airborne virus; PCR; Detection limits;

PAH emissions and energy efficiency of palm-biodiesel blends fueled on diesel generator by Yuan-Chung Lin; Wen-Jhy Lee; Hsiao-Chung Hou (3930-3940).
This study investigated the emissions of polycyclic aromatic hydrocarbons (PAHs), carcinogenic potencies (BaPeq) and particulate matter (PM), fuel consumption and energy efficiency from the generator under steady state for seven test fuels: P0 (Premium Diesel Fuel), P10 (10% palm biodiesel+90% P0), P20, P30, P50, P75 and P100. Experimental results indicated that PAH emission decreased with increasing palm-biodiesel blends due to small PAH content in biodiesel. The mean reduction fraction of total PAHs emission factor (P0=1110 μg L−1) from the exhaust of diesel generator were 13.2%, 28.0%, 40.6%, 54.4%, 61.89% and 98.8% for P10, P20, P30, P50, P75 and P100, respectively, compared with P0. The mean reduction fraction of total BaPeq (P0=1.65 μg L−1) from the exhaust of diesel generator were 15.2%, 29.1%, 43.3%, 56.4%, 58.2% and 97.6% for P10, P20, P30, P50, P75 and P100, respectively, compared with P0. PM emission decreased as the palm-biodiesel blends increased from 0% to 10%, and increased as the palm-biodiesel blends increased from 10% to 100% because the soluble organic fraction of PM emission was high in blends with high palm-biodiesel content. The brake specific fuel consumption rose with rising palm-biodiesel blends due to the low gross heat value of palm-biodiesel. The increasing fraction of BSFC of palm-biodiesel was lower than those of soy-, soapstock-, brassica-carinate and rapeseed-biodiesel. Palm-biodiesel seems to be the most feasible biodiesel. The best energy efficiency occurred between P10 and P20, close to P15. The curve dropped as the palm-biodiesel content rose above P20. Above results revealed that palm-biodiesel was an oxygenated fuel appropriate for use in diesel engines to promote combustion efficiency and decrease PAH emission. However, adding an excess of palm-biodiesel to P0 leaded to incomplete combustion in the diesel-engine generator and inhibited the release of energy in the fuel.
Keywords: Toxic; Carcinogenic potencies; Biofuel; Generator; Exhaust;

The quantity, identity, and distribution of biomass in indoor and outdoor aerosols are poorly described. This is not consistent with the current understanding of atmospheric chemistry or the microbiological characterization of aquatic and terrestrial environments. This knowledge gap is due to both difficulties in applying contemporary microbiological techniques to the low biomass concentrations present in aerosols, and the traditional reliance of aerosol researchers on culture-based techniques—the quantitative limitations and ecological biases of which have been well-documented and are now avoided in other environmental matrices. This article reviews the emergence of the polymerase chain reaction (PCR) as a nonculture-based method to determine the identity, distribution, and abundance of airborne microorganisms. To encourage the use of PCR-based techniques by a broad spectrum of aerosol researchers, emphasis is given to the critical, aerosol specific method issues of sample processing, DNA extraction, and PCR inhibition removal. These methods are synthesized into a generalized procedure for the PCR-based study of microbial aerosols—equally applicable to both indoor and outdoor aerosol environments.
Keywords: PCR; Bioaerosol; DNA; Methods; Aerosol;

Predicting mercury wet deposition in Florida: A simple approach by Mark Fulkerson; Fidelia N. Nnadi (3962-3968).
Atmospheric mercury deposition is currently simulated using complex models that incorporate known transport and transformation processes. Though comprehensive, significant errors still exist between simulated and measured Mercury Deposition Network (MDN) data. The goal of this work was to develop a simpler approach to predict mercury deposition. Weekly precipitation sampling in Orlando, FL was conducted from September 2003 and presently continues. Rainfall and mercury deposition data were gathered from this site and 7 others located in and around Florida, to investigate spatial and seasonal patterns. Approximately 80% of Florida's rainfall and mercury deposition occur during the wet season. Regional wet and dry season equations were developed to predict mercury deposition from rainfall depth. A positive linear relationship was observed between rainfall depth and mercury deposition ( R 2 = 0.80 ). Model results were validated with MDN measurements at the Orlando site. This tool can be applied to predict mercury deposition at any location in Florida using local rainfall data.
Keywords: Atmospheric deposition; Mercury; Precipitation; Regression; MDN;

Influence of topography and land use on pollutants dispersion in the Atlantic coast of Iberian Peninsula by A.C. Carvalho; A. Carvalho; I. Gelpi; M. Barreiro; C. Borrego; A.I. Miranda; V. Pérez-Muñuzuri (3969-3982).
The west coast of Iberian Peninsula, surrounded by the Atlantic Ocean, is characterised by complex topography and specific synoptical situations that imply mesoscale circulations development. The main purpose of this work is to analyse how mesoscale circulations induced by topography and/or land use control pollutants dispersion in a coastal region. A numerical system combining the MM5 meteorological model and the air-quality model MARS was applied to the north western part of Portugal mainland. This system of models simulated the dispersion of pollutants in the atmosphere during two consecutive summer days under the influence of a thermal low-pressure system located over the Iberian Peninsula. To analyse the photo-chemical production inside the domain of interest an interface between MM5 and the photo-chemical model MARS was built up, constituting the first attempt to integrate these two models. MM5 and MARS sensitivity tests were performed for different conditions starting with null topography and homogeneous land use. The achieved results revealed that the mesoscale circulations that are developed in the west coast of Iberian Peninsula are mainly related to topographic effects instead of land–sea thermal-induced ones. Topography represented the main driving force mechanism on air pollutants injection in higher tropospheric levels.
Keywords: Physiographical aspects; Thermal-induced circulations; Ozone patterns;

A comparative study of the organic matter in PM2.5 from three Chinese megacities in three different climatic zones by Jialiang Feng; Min Hu; Chak K. Chan; P.S. Lau; Ming Fang; Lingyan He; Xiaoyan Tang (3983-3994).
Organic matter in PM2.5 collected in 2002 and 2003 from three megacities in different climatic zones in China, Beijing (40°N), Shanghai (31°N) and Guangzhou (23°N), was characterized. The focus was on solvent-extractable organic compounds (SEOC), which were used to identify the influences of geography, variation of the season, sources and transport on the concentration and distribution of these homologues. Organic carbon, elemental carbon, and water-soluble organic carbon concentrations were analyzed only for the substantiation of the SEOC findings. Analysis of the fossil fuel residues and the plant wax components in n-alkanes, PAHs, fatty acids and n-alkanols allowed the identification of anthropogenic (coal and petroleum combustion processes, and kitchen emissions) and biogenic (vegetation and microbial) sources. The influence of temperature on the distribution of the SEOC was exemplified by the negative correlation between the relative concentrations of the semivolatile homologues (alkanes and PAHs) and ambient temperature. This is attributable to gas–particle partitioning. Indirectly, ambient temperature dictates the type of vegetation that can grow in a geographical zone. This would influence the distribution of the plant waxes, and finally, it plays a role in the aerosol loading due to energy usage.
Keywords: PM2.5; SEOC; OC/EC; WSOC; Climatic zone; Guangzhou; Beijing; Shanghai; China;

Ambient air pollution by aromatic hydrocarbons in Algiers by Rabah Kerbachi; Ménouèr Boughedaoui; Lahouari Bounoua; Malika Keddam (3995-4003).
The analysis of the C6–C16 semi-volatile organic compounds reveals the presence of numerous aromatic hydrocarbons in the ambient air of Algiers. Three representative sites were chosen for sample collection at roadside, urban background and semi-rural areas. The following major monocyclic aromatic hydrocarbons were found: benzene, toluene, ethylbenzene, (m,  p)- and o-xylene, also referred to as BTEX. Near the road traffic, benzene and toluene mean concentrations were 27 and 39 μg m−3, respectively, with benzene concentration values higher than 40 μg m−3 often observed. At the urban site, the benzene concentration often exceeds the European regulatory limit of 10 μg m−3 while the compositional ratios of toluene to benzene and (mp) xylene to ethylbenzene are within the typical range of values observed in urban atmospheres worldwide. The seasonal variation indicates a decrease in concentration during summer of the reactive o-xylene compound. It is suggested that Algiers’ source of high-level air pollution by aromatic hydrocarbons is related to car traffic emissions.
Keywords: Air pollution; Road traffic; BTEX compounds; VOC; Algeria;

The fraction of days on which ozone concentrations exceeded the ambient air quality standard increased from 2.9% in 2000 to 4.6% in 2004 in southern Taiwan. Mobile sources attributed for 44.7% and 17.6% of the ozone precursors, NO x and NMHC, respectively, based on the emission inventory of the Taiwan EPA. However, a new second north–south highway was recently constructed in Taiwan. This study evaluates how emissions from the first and second highways affect the ambient air quality, especially ozone concentration by using CMAQ between 14 and 17 December 2002. Two emissions scenarios were examined. The first involved emissions from only the first highway and the second involved emissions from only the second highway. The mean errors of the unpaired peak ozone concentration were generally less than 17%; and those of the paired ozone concentrations were less than 25%. Correspondingly, the results simulated by the model were highly consistent with observed data. Simulation results indicated that most ambient O3 concentrations increased by more than 2 ppb with hourly increments of up to 6 ppb, in both scenarios. Although the total emissions were the same, the differences among emission locations were responsible for substantial differences in ozone concentrations. The ozone concentrations decreased along the highway as the emissions increased, because of NO titration. However, the ozone concentrations were greater at sites that were further downwind. Therefore, the ozone concentrations changed significantly with the highway network, given the same total emission. The differences in ozone concentrations were caused by the changes in the emission locations of NO x .
Keywords: CMAQ; Mobile source; Model performance; Emission; NO titration;

Atmospheric gaseous elemental mercury in downtown Toronto by Monique St. Denis; Xinjie Song; Julia Y. Lu; Xinbin Feng (4016-4024).
Continuous measurements of gaseous elemental mercury (GEM) in downtown Toronto were conducted from June 2001–February 2002. Ambient air was sampled at 3.5 and 7 m above ground in a canopy over a sidewalk. The quarter hourly mean concentrations were found at 2.39±2.05 ng m−3 (N=10,658) for the lower sampling level, and 2.57±2.39 ng m−3 (N=10,628) for the upper sampling level. The average of both sampling levels (2.48 ng m−3) was 60% higher than the average of Canadian background emission (1.55 ng m−3, Alert). Seasonal concentrations showed the effects of the temperature on the volatilization of Hg0. Higher GEM was found in the summer time (20 June–19 September) at 3.03±2.13 ng m−3 (lower level) and 3.31±2.56 ng m−3 (upper level) while lower values were observed in the fall (20 September–19 December) at 1.84±0.87 ng m−3 (lower level) and 1.97±1.38 ng m−3 (upper level). Log normal probability distribution of the GEM concentration was verified and the double peak hourly average diurnal distribution of GEM concentration was observed in our study.
Keywords: Mercury; Atmosphere; Gaseous elemental mercury (GEM); Urban environment;