Atmospheric Environment (v.38, #8)

Air pollution related deaths during the 2003 heat wave in the Netherlands by Paul H. Fischer; Bert Brunekreef; Erik Lebret (1083-1085).
In the Netherlands an excess of 1000–1400 deaths was estimated due to the hot temperatures that occurred during the 2003 summer period. We estimated the number of deaths attributable to the ozone and Particular Matter (PM10) concentrations in the summer period June–August 2003. Our calculations show that an excess of around 400–600 air pollution-related deaths may have occurred compared to an ‘average’ summer.These calculations suggest that in the Netherlands, a significant proportion of the deaths now being attributed to the hot summer weather can reasonably be expected to have been caused by air pollution.
Keywords: Air pollution; Heat wave; Deaths; Summer; Climate changes;

There was a major heatwave across much of Europe in the first two weeks of August 2003, during which temperatures peaked at a new record of 38.5° C in the UK. The UK Office for National Statistics have reported an excess of 2045 deaths in England and Wales for period from 4 to 13 August 2003 above the 1998–2002 average for this time of year. Here we estimate, using previously established dose–response functions, that there were between 423 and 769 excess deaths in England and Wales during the first two weeks of August 2003 associated with the elevated ambient ozone and PM10 concentrations. This represents 21–38% of the total excess deaths. This has implications for the mitigation of the health effects of heatwave conditions. It reinforces the advice to the public on keeping cool, reducing exposure to outdoor air pollutants and indeed possible measures to reduce atmospheric pollution. The predictions presented here could be verified by conducting a specific epidemiological study of deaths during this heatwave.
Keywords: Photochemical ozone episode; Health impact assessment; PM10;

Spatial and temporal variations of PM2.5 concentration and composition throughout an urban area with high freeway density—the Greater Cincinnati study by Dainius Martuzevicius; Sergey A Grinshpun; Tiina Reponen; Rafał L Górny; Rakesh Shukla; James Lockey; Shaohua Hu; Rafael McDonald; Pratim Biswas; Linas Kliucininkas; Grace LeMasters (1091-1105).
The PM2.5 concentration and its elemental composition were measured in the Cincinnati metropolitan area, which is characterized by intense highway traffic. The spatial and temporal variations were investigated for various chemical elements that contributed to the PM2.5 fraction during a 1-year-long measurement campaign (December 2001–November 2002). The ambient aerosol monitoring was performed in 11 locations around the city during nine measurement cycles. During each cycle, four Harvard-type impactors were operating in parallel in specific locations to explore various factors affecting the PM2.5 elemental concentrations. The sampling was performed during business days, thus assuring traffic uniformity. The 24-h PM2.5 samples were collected on Teflon and quartz filters. Teflon filters were analyzed by X-ray fluorescence (XRF) analysis while quartz filters were analyzed by thermal-optical transmittance (TOT) analysis. In addition to PM2.5 measurements, particle size-selective sampling was performed in two cycles using micro-orifice uniform deposit impactor; the collected fractionated deposits were analyzed by XRF. It was found that PM2.5 concentration ranged from 6.70 to 48.3 μg m−3 and had low spatial variation (median coefficient of variation, CV=11.3%). The elemental concentrations demonstrated high spatial variation, with the median CV ranged from 38.2% for Fe to 68.7% for Ni. For traffic-related trace metals, the highest concentration was detected in the city center site, which was close to a major highway. The particle size selective measurement revealed that mass concentration of the trace metals, such as Zn, Pb, Ni, as well as that of sulfur reach their peak values in the particle size range of 0.32–1.0 μm. Meteorological parameters and traffic intensity were not found to have a significant influence on the PM2.5 elemental concentrations.
Keywords: Air pollution; PM2.5; Elemental composition; Traffic;

The purpose of this research is to study a single droplet scavenging mechanisms upon atmospheric ammonia by using the two-phase simulation method (TPSM). In the developed method, the continuity, Navier–Stoke, and species conservation equations of the gas phase and the liquid phase are fully solved numerically. The predicted results indicate that the gaseous ammonia is scavenged outward rapidly from the interface initially, on grounds of intrinsic solute-sink characterized by the droplet. When the exposure time is long to a certain extent, by virtue of increasing the solute concentration at the interface, the region affected by the uptake progressively moves back to the droplet. Transient variations of scavenging distances ahead of and behind the droplet are examined to recognize the extension and shrinkage characteristics of the scavenging process. Under the impact of the convective flow, the scavenging distance behind the droplet is always farther than that in front of the droplet. Considering the droplet internal motion, on account of drastic interaction between the primary vortex and the secondary vortex inside the droplet, the vortex bifurcation is exhibited. This further results in that the maximum value of the interfacial concentration tends to shift from the front stagnation point of the droplet to the aft one. In contrast, over the entire absorption process the mass flux is mainly contributed from the front portion of the droplet, resulting from the effect of the momentum boundary layer in the gas phase. Eventually, the predicted difference in absorption period between the TPSM and the rapid diffusion model (RDM) is evaluated. It reveals that the latter substantially underestimates the absorption time when a solute with larger mass diffusion number is regarded.
Keywords: Droplet; Scavenging mechanisms; Two-phase simulation method; Mass diffusion number; Ammonia;

Lindane is one of the organochlorine pesticides, a major portion of persistent organic pollutants. Major use of lindane in Canada was on canola and corn. In this paper, temporal and spatial use trends of this pesticide in Canada between 1970 and 2000 have been presented Use of lindane on canola and corn in Canada between 1970 and 2000 has been estimated to be 9 kt, with highest value (558 t) in 1994. The intensive use of this pesticide has been in the Prairie Region of Canada, the provinces of Alberta, Saskatchewan and Manitoba, as high as 8.5 kt, 94% of total usage. Inventories of gridded usage of lindane in Canada with 1/6° by 1/4° latitude/longitude resolution have been created by gridded canola and corn data sets with the same resolution as surrogate data. The highest application of lindane is around 15 t per grid cell, located in the Prairie Region.
Keywords: Pesticides; Organochlorine; POPs; Lindane; Canada; Canola; Corn;

A study on mechanisms of nitrous oxide formation in post-combustion flue gases by Fernando Preto; Jinsheng Wang; Lufei Jia; Edward J. Anthony (1123-1131).
N2O formation in low-concentration NO and SO2 mixtures was examined and the promotional effects of O2 and water vapor on the formation were studied. At 25°C N2O formed in dry gas mixtures with NO and SO2 concentrations as low as 10 ppm. With the addition of water vapor N2O formation rate increased significantly. The effect of water vapor was more pronounced when O2 was also present. The results suggest that SO2 participates in the gas phase reaction that forms N2O, and forms H2SO4 which enhances N2O formation rate. The temperature dependence of N2O formation appears to be weak and at −25°C N2O still forms in appreciable quantities, suggesting that N2O could form in severe winter conditions in power plant plumes. Such formation can be attributed to gas phase and surface reactions but not liquid phase reactions. A study of the effects of solid materials on the rate of surface reaction indicated that carbon steel enhanced N2O formation whereas lime particles inhibited the formation. Possible mechanisms are discussed along with the implication of the results in predicting N2O formation levels in post-combustion flue gases from large combustion units.
Keywords: N2O; Formation rate; NO; SO2; Flue gas;

Properties of individual Asian dust storm particles collected at Kosan, Korea during ACE-Asia by Chang-Jin Ma; Susumu Tohno; Mikio Kasahara; Shinjiro Hayakawa (1133-1143).
For the purpose of studying the properties of individual Asian dust storm particles, an intensive field measurement took place at the Kosan ground-based station located on the west coast of Cheju Island, Korea during ACE-Asia campaign. A 2-stage filter pack sampler was employed in the size-resolved (coarse and fine fractions) particle sampling. The trace elements of individual coarse particles (>1.2 μm) were analyzed by the X-ray microprobe analysis system equipped at SPring-8. The result of statistical analysis suggested that individual particles collected in Asian dust storm event could be classified into four groups: sea-salt-rich particles, crustal-rich particles, crustal/sea-salt/sulfur-rich particles, and crustal/sea-salt-rich particles. Moreover, according to the XRF elemental maps and elemental masks replayed corresponding to individual particles, particles could be categorized into two groups, namely internally mixed particles and externally mixed particles. A small part of the CaCO3 in Asian dust storm particles would be converted to CaSO4 through the chemical reaction between CaCO3 and H2SO4 during long-range transport. By means of XANES method, the major chemical state of Fe in Fe-rich particles was found to be Fe3+. Several minor trace heavy metals were probably affected by the air masses passed directly over the industrial areas of China.
Keywords: Asian dust storm; Individual particles; X-ray microprobe system; Elemental mass; ACE-Asia;

Trends in methane and sulfur hexafluoride at a tropical coastal site, Thumba (8.6°N, 77.°E), in India by S. Lal; D. Chand; S. Venkataramani; K.S. Appu; M. Naja; P.K. Patra (1145-1151).
Measurements of methane (CH4) and sulfur hexafluoride (SF6) have been made using gas chromatographic technique at a coastal site, Thumba (8.6°N, 77°E), India from the flask air samples collected during 1996–2000. The growth rates of CH4 and SF6 are observed to be 30 and 0.25 pptv yr−1 respectively. The growth rate of CH4 at Thumba is found to be much higher than its average growth rate of about 7 ppbv yr−1 at other tropical monitoring sites. The observed growth rate of SF6 at Thumba is similar to that found at other tropical stations. Seasonal amplitudes in CH4 and SF6 are higher at Thumba when compared to the other sites. The large growth rate of CH4 at Thumba could be attributed to the increase in regional sources, and the greater seasonal amplitude is shown to be caused by the change in dynamical structure from Northern Hemisphere summer to winter.
Keywords: Trace gases; Gas chromatography; Tropical region; Time series; Growth rates;

We have studied oxidant photoformation in aqueous extracts of aerosol particles collected from Alert, Nunavut, Canada during springtime. Absorption spectra of the extracts reveal that Alert particles have tremendous light absorption coefficients (e.g., α 300∼100 cm−1) as a result of unidentified, pH-dependent, water-soluble chromophores. Illumination of the extracts leads to the rapid formation of both hydroxyl radical (OH) and hydrogen peroxide (HOOH). Based on our laboratory results, the calculated rate of OH photoformation in Alert particles is very rapid, ∼1 mM h−1 (midday, 1 April, 248 K), with nitrate photolysis contributing only ∼10% of the total rate. Deposition of these aerosol particles, in conjunction with smaller contributions from gaseous chromophores, leads to estimated rates of OH photoformation in the quasi-liquid layer of surface snow of 20–40 μM h−1; approximately a third of this reactivity is from nitrate photolysis. The estimated 24-h-average rate of HOOH photoformation in Alert particles (∼9 mM h−1 on 1 April) is large enough to be a major source of HOOH to both the particles and the gas phase. In contrast, particle-derived reactions in the snow appear to be a minor source of HOOH to the surface snowpack. The effects of OH and HOOH photoformation in particles and snowpack likely include the oxidation of organic carbon, halides, and S(IV) species to yield products such as volatile aldehydes and carboxylic acids, photoactive halogens, and sulfuric acid. In addition, OH and HOOH photoformation within the snowpack might significantly alter snow and ice core records of HOOH and other trace gases.
Keywords: Snow chemistry; Nitrate chemistry; Ice cores; OH; HOOH; H2O2;

Wind-dependent sea salt aerosol in a Western Pacific coastal area by Ka-Ming Wai; Peter A Tanner (1167-1171).
Five-year PM10 data sets from three monitoring stations at a coastal city of China have been employed, together with surface pressure maps, wind data and backward trajectory analyses to investigate the relationship between sea salt concentration (C) and wind speed (U). A log-linear variation of sodium ion concentration with wind speed has been obtained (i.e. ln  C=aU+b), only under the influence of the Asian summer monsoon, where U is the synoptic wind speed rather than the local wind speed. The values a and b fall into the range of values from previous studies, although the background loading b is relatively small, since the previous studies were carried out on ships or very near to the coastal line rather than in an urban area. The sea salt concentrations are mainly influenced by the production mechanism rather than the transport process.
Keywords: Wind speed; Sodium; Chloride; Particulate matter;

An analytical model for VOCs emission from dry building materials by Baoqing Deng; Chang Nyung Kim (1173-1180).
A new analytical model for VOCs emission is presented in this paper. This model considers both the diffusion in the materials and the mass transfer through the air boundary layer. Compared to other models capable of accounting for those two mechanisms, this model is fully analytical. A general characteristic equation is developed, which would reduce to that of Little et al. (Atmos. Environ. 28 (1994) 227) when the gas-phase mass transfer coefficient becomes infinite. Thus, with the current model the concentration in the air can be solved conveniently without iteration. Results of the present model show a good agreement with the experimental data while the model of Little et al., overestimated the concentration in the air. Also, further analysis on this model shows that the concentration in the air increases with the increase of the gas-phase mass transfer coefficient in the early stage. And the normalization of the concentrations in the materials and in the air shows that five dimensionless numbers are needed to determine the characteristics of VOCs transport from the building materials to the air.
Keywords: VOCs emission; Analytical model; Gas-phase mass transfer coefficient; Diffusion;

Seasonal cycle of indoor-VOCs: comparison of apartments and cities by U Schlink; M Rehwagen; M Damm; M Richter; M Borte; O Herbarth (1181-1190).
On the basis of 2103 measurements of volatile organic compounds (VOCs) in indoor air we study the intensity of a seasonal pattern. The data are representative for the German population and were gathered in different cities (Leipzig, München, Köln), in rooms of different type (children's, living, sleeping rooms, and other rooms), and in households of smokers and non-smokers. In addition to the randomly selected different apartments that were sampled each month, we repeatedly measured in a fixed set of 10 apartments. The analysis comprised concentrations of 30 VOCs belonging to the groups of alkanes, cycloalkanes, aromatics, volatile halogenated hydrocarbons, and terpenes.The annual cycle for total VOC concentrations was observed at every site. Seasonality proved to be the most dominant pattern, but it may be modified by further factors, such as the city, the considered VOC component, and the type of the considered room. Highest concentrations occurred during the winter months and amount to approximately three to four times the summer burden. As seasonality may bias the results of health effect studies we fit a seasonal model to our measurements and develop a procedure for seasonal adjustment, which enables to roughly estimate the annual peak concentration utilizing one monthly observation. The seasonal pattern proved to be a general feature of indoor VOC concentrations and, therefore, this adjustment procedure may be generally applicable. For Leipzig, München, and Köln we present site-specific adjustment factors for indoor concentrations of aromatics, terpenes, and alkanes.
Keywords: VOC; TVOC; Indoor air; Seasonal variation; Seasonal adjustment;

Characteristics of lead isotope ratios and elemental concentrations in PM10 fraction of airborne particulate matter in Shanghai after the phase-out of leaded gasoline by Jian Zheng; Mingguang Tan; Yasuyuki Shibata; Atsushi Tanaka; Yan Li; Guilin Zhang; Yuanmao Zhang; Zuci Shan (1191-1200).
The stable lead (Pb) isotope ratios and the concentrations of 23 elements, including heavy metals and toxic elements, were measured in the PM10 airborne particle samples collected at seven monitoring sites in Shanghai, China, to evaluate the current elemental compositions and local airborne Pb isotope ratio characteristics. Some source-related samples, such as cement, coal and oil combustion dust, metallurgic dust, vehicle exhaust particles derived from leaded gasoline and unleaded gasoline, and polluted soils were analyzed for their Pb content and isotope ratio and compared to those observed in PM10 samples. Airborne Pb concentration ranged from 167 to 854 ng/m3 in the seven monitored sites with an average of 515 ng/m3 in Shanghai, indicating that a high concentration of Pb remains in the air after the phasing out of leaded gasoline. Lead isotopic compositions in airborne particles (207Pb/206Pb, 0.8608±0.0018; 208Pb/206Pb, 2.105±0.005) are clearly distinct from the vehicle exhaust particles (207Pb/206Pb, 0.8854±0.0075; 208Pb/206Pb, 2.145±0.006), suggesting that the automotive lead is not currently the major component of Pb in the air. By using a binary mixing equation, a source apportionment based on 207Pb/206Pb ratios, indicates that the contribution from automotive emission to the airborne Pb is around 20%. The Pb isotope ratios obtained in the source-related samples confirmed that the major emission sources are metallurgic dust, coal combustion, and cement.
Keywords: Lead isotopes; Airborne particles; ICP-MS; Shanghai; Leaded gasoline;

EPR investigation of iron in size segregated atmospheric aerosols collected at Dunkerque, Northern France by Frédéric Ledoux; Elena A Zhilinskaya; Dominique Courcot; Antoine Aboukaı̈s; Emile Puskaric (1201-1210).
Electron paramagnetic resonance (EPR) spectroscopy was used to study atmospheric aerosols at Dunkerque, a French sea-side city located on the southern coast of the North Sea. Particles were collected in June–July 2001 and January–February 2002 periods using global filtration and cascade impaction. EPR spectra obtained for these particles were attributed to Fe3+ ions, mainly in the form of hematite (α-Fe2O3) in interaction with other paramagnetic species (Fe3+, Mn2+, Cu2+, etc.). From the EPR spectra intensities measured at 77 and 293 K, Fe3+ ions were evidenced in the form of clusters and agglomerated species. Fe3+ agglomerated species were observed mainly for winds blowing from the industrial park. Cascade impactor samples study evidenced that clusters are rather detected in the small size particles whereas agglomerated Fe3+ ions species are rather present in the large ones. The small size particles are richer in iron than the large ones, thus such particles play an important role in the value of EPR parameters.
Keywords: Aerosols; Fe3+; EPR; Size-fractionated samples;

Quantification of iron oxides in desert aerosol by Sandra Lafon; Jean-Louis Rajot; Stéphane C. Alfaro; Annie Gaudichet (1211-1218).
For assessing the impact of desert aerosols on climate, it is necessary to quantify their content in iron oxides minerals. These minerals are well known for their light absorbing properties. Iron contained in them—the so-called “free-iron” by soil scientists—represents only a part of the total-iron content. Indeed, the latter also includes the iron trapped in the crystal lattice of several desert aerosol mineralogical species. In this paper we propose an adapted technique to quantify the free-iron in desert aerosol based on a selective extraction method classically used in soil science. Adaptations are made necessary because of the low aerosol load collected on filter samples under field conditions (masses typically lower than 0.5 mg). Validation is obtained by comparing results of the adapted and classical methods when applied to the same geostandards.We analysed natural samples from three main desert source areas : Sahel (Niger during local erosion events), Sahara (Niger during Harmattan events) and Gobi desert (China). For these samples, the free-to-total iron ratio varied between 0.4 and 0.7. This natural variability indicates that the free-iron in aeolian dust is not directly proportional to the total-iron. As a consequence, total iron cannot be used directly to calculate dust light absorbing properties. The percentages of free-iron relative to the total estimated aerosol mass is 2.8%, 3.7%, and 5.0% in Saharan, Chinese, and Sahelian samples respectively.
Keywords: Mineral dust; Iron status; Mineralogy; Chemical extraction method;

Commuters’ exposure to PM2.5, CO, and benzene in public transport in the metropolitan area of Mexico City by J.E Gómez-Perales; R.N Colvile; M.J Nieuwenhuijsen; A Fernández-Bremauntz; V.J Gutiérrez-Avedoy; V.H Páramo-Figueroa; S Blanco-Jiménez; E Bueno-López; F Mandujano; R Bernabé-Cabanillas; E Ortiz-Segovia (1219-1229).
A survey was carried out to measure commuters’ exposure to PM2.5, CO, benzene, and the chemical composition of PM2.5 on different routes and modes of transport in Mexico City. PM2.5 (n=62), CO (n=54) and benzene (n=22) are presented from morning (6:30–9:30 a.m.) and evening (17:30–20:30) rush hours on minibuses, buses and Metro (underground or subway system). Three routes were selected from a previous commuters’ exposure study covering some of the most important thoroughfares of the valley. For PM2.5, mass concentration was determined for all the samples. Nitrates, sulphates, inorganic elements and carbon fraction were analysed. CO was sampled using electrochemical sensors and 6-l canisters with flow controller devices were used to collect integrated samples for benzene. Minibuses had a slightly higher geometric mean PM2.5 concentration in the morning than other modes of transport, but the ranking of geometric mean PM2.5 by mode of transport is opposite in the evening and the variability within modes is approximately double the difference between modes. The highest single measurement was a concentration of 137 μg m−3 on a bus during an evening rush hour. The main component identified in PM2.5 was carbon. Carbon monoxide levels in this study were approximately 3 times lower than those found in a commuter exposure study conducted in 1991. A strong association was shown between wind speed and PM2.5 exposure in minibuses (r 2=0.50) and buses (r 2=0.54). The relationship between wind speed and CO exposure was strong only in minibuses (r 2=0.52).
Keywords: Mexico city; Public transport; Commuters’ exposure; PM2.5; CO; Benzene;