Atmospheric Environment (v.39, #14)

A burning question. Can recent growth rate anomalies in the greenhouse gases be attributed to large-scale biomass burning events? by P.G. Simmonds; A.J. Manning; R.G. Derwent; P. Ciais; M. Ramonet; V. Kazan; D. Ryall (2513-2517).
Simultaneous in situ measurements of carbon dioxide (CO2) and the principal gases linked to biomass burning at the Mace Head Observatory, Ireland, reveal a strong correlation in 1998–99 and 2002–03, both periods with intense global fires. CO2, carbon monoxide (CO), methane (CH4), hydrogen (H2), ozone (O3) and methyl chloride (CH3Cl), all have similar rates of accumulation during these time frames. These perturbations imply a causal relationship between large-scale biomass burning events and the interannual variability of these gases.
Keywords: Carbon dioxide; Biomass burning; Greenhouse gases;

A new chemical mechanism analysis tool known as multi-parent assignment (MPA) is used to explore reactant contributions to ozone formation in the SAPRC-99 atmospheric chemistry mechanism. Mathematical details of MPA, which extends an earlier method by accounting for multiple reactants, are presented. MPA uses reaction rate information and mechanism stoichiometry to trace reaction pathways within a mechanism from products back to parent reactants. The net contribution of different reactants to products, such as O3 or OH, is then determined. Three formulas for assigning products among multiple reactants in a reaction are defined and compared. MPA analysis of an urban ozone formation scenario at three different NO x levels shows that all individual reactants contribute in some degree to ozone formation. NO and NO2 contributions vary greatly depending on VOC/NO x ratio and on how parent reactants are weighted in individual reactions. The most productive hydrocarbons on a ppm O3 per ppmC basis are generally aldehydes, followed by alkenes and higher aromatics, and then alkanes and lower aromatics. Reactant contributions to ozone are shown to vary with time, and shifts in limiting reactant behavior are also observed.
Keywords: Chemical mechanism analysis; Ozone formation; Product assignment; Ozone precursors; Reactivity;

Performances of the Radiello® diffusive sampler for BTEX measurements: Influence of environmental conditions and determination of modelled sampling rates by Anne Pennequin-Cardinal; Hervé Plaisance; Nadine Locoge; Olivier Ramalho; Séverine Kirchner; Jean-Claude Galloo (2535-2544).
Radiello® diffusive samplers filled with a thermally desorbable adsorbent (graphitised carbon Carbograph 4) have been evaluated for the monitoring of BTEX according to the European standard EN 13528-2. Blank values and analytical recovery rates were in agreement with the requirements of this protocol. The sampling rates have been estimated under various controlled atmospheres in order to evaluate the effects of some environmental factors on the performances of the Radiello® sampler: concentration levels, temperature, exposure time, humidity and wind velocity. The effects of back diffusion and a mixture of 37 VOC have been determined. According to the whole of these results, modelled sampling rates have been set up. These experiments in exposure chamber showed that, for a medium level of concentration in air (5 μg m−3 for benzene), the expanded uncertainties were between 20% for benzene and 27% for m/p-xylene under environmental indoor conditions and between 19% for benzene and 31% for m/p-xylene under environmental outdoor conditions. The result for benzene is conform to the requirements of the future European Directive for benzene which define the maximum of uncertainty to 25% for annual concentrations near 5 μg m−3.
Keywords: Diffusive sampling; BTEX; Exposure chamber; Meteorological and dose factors effects; Uncertainty;

Investigation of urban atmospheric visibility by high-frequency extraction: Model development and field test by Chin-Hsiang Luo; Che-Yen Wen; Chung-Shin Yuan; Jiun-Jian Liaw; Cho-Ching Lo; Shih-Hsuan Chiu (2545-2552).
This work investigates atmospheric visibility by employing two statistical processes for high-frequency extraction: Sobel operator and fast Fourier transform (FFT). In replacing the traditional measurement methods for atmospheric visibility, the new approaches can provide accurate digital data urban visibility by establishing the numerical indices. The procedure is illustrated as follows. Digital images of urban areas in Kaohsiung, a city at the south of Taiwan, are analyzed according to brightness. High-frequency components of the image are extracted to calculate the index values by employing the Sobel operator and FFT. Finally, the correlation between each index and the visual range estimated by trained investigators are evaluated. A good correlation between two indices and the values obtained by visual investigation is affirmed by correlation coefficients ( R 2 ), 0.8139 and 0.7797, respectively. Furthermore, both indices are highly correlated with each other ( R 2 = 0.9173 ). Convenient transmission and the exchangeability of digital images of the real-time landscape facilitate the publication of results on the world wide web (WWW).
Keywords: Visibility; Frequency extraction; Image processing; Air quality;

By comparison with the Northern Hemisphere, the history of atmospheric lead pollution in the Southern Hemisphere is still poorly understood. Until recently, the main source of atmospheric lead fallout in the Southern Hemisphere was tetraethyl lead from motor fuel and for most of the 20th century the most important single source of this pollutant was Australia. Yet there is little agreement over when leaded fuel made its first appearance in Australia. Reported dates range from the early 1920s to the late 1940s. A study of oil company advertisements and reports in motoring and oil company journals shows that leaded petrol first became available in Australia in August 1932. This date is important both for the reconstruction of lead pollution histories and in the use of lead stratigraphies to determine chronology.
Keywords: Australia; Southern Hemisphere; Lead pollution; Tetraethyl lead; Dating methods;

An analysis of CO2 (carbon dioxide) concentrations (monthly values and their 12-month running means) at various locations during 1970–2001 indicated a general increase of ∼10% in 2–3 decades. It was not uniform and was smaller (only ∼1.5% in 5 years) during 1990–1995. When the long-term (3 years or more) variation was estimated by calculating 3-year running means and was subtracted from the 12-month running means, small oscillations (range less than 0.2%) were noticed with peak spacings in the QBO, QTO (quasi-biennial and quasi-triennial oscillations, 2–3 and 3–4 year) ranges. In latitudes north of ∼30°N, the peaks resembled the QBO of stratospheric low latitude winds (peak spacings of ∼28 months). For latitudes south of 30°N, CO2 changes seemed to be associated with ENSO phenomenon, though the major El Niños of 1982–1983 and 1997–1998 seemed to have caused abnormal variations (∼exceeding 0.2%) only in one or two latitude belts.
Keywords: Carbon dioxide; Quasi-biennial oscillation (QBO); Quasi-triennial oscillation (QTO);

Ozone dry deposition above a tropical forest in the dry season in northern Thailand by Kazuhide Matsuda; Ichiro Watanabe; Vitsanu Wingpud; Phunsak Theramongkol; Pojanie Khummongkol; Supat Wangwongwatana; Tsumugu Totsuka (2571-2577).
In order to investigate the ozone dry deposition above a tropical forest in Southeast Asia, the field experiments were performed in a flat deciduous (teak) forest in Mea Moh located in northern Thailand, in the dry season, from January to April 2002. The experimental period included both the leafless period and transitional period between lush and leafless. Ozone fluxes were obtained by coupling a UV photometric ozone monitor with an ultrasonic anemometer on the basis of the gradient method. Ozone concentrations exceeded 60 ppb on average in the afternoons during the experimental period. The ozone fluxes peak around noon. The daytime level of the fluxes in this study is relatively high compared with the fluxes from previous experiments over a tropical forest or a leafless deciduous forest in other regions. This high daytime flux level is mainly caused by the high concentrations in the dry season in Mae Moh. Median deposition velocities of ozone were 0.32 cm s−1 in daytime (6:00–17:00) and 0.04 cm s−1 in nighttime (18:00–5:00), respectively. The deposition velocities as well as the fluxes peaks around noon. Observed surface resistances decreased in daytime. The surface resistances were found to be affected by aerodynamic process rather than stomatal process during the time from 10:00 to 2:00. Wesely's parameterization to infer surface resistance was examined to consider its applicability in the region. The observed surface resistance in the dry season is closer to the inferred surface resistance using the input resistances of transitional spring than that using the input resistances of leafless seasons. This indicates that the parameterization of non-stomatal resistances needs modification above the teak forest in the dry season taking into account the influence of aerodynamic process and the specific conditions in northern Thailand.
Keywords: Ozone dry deposition; Tropics; Southeast asia; Measurement; Surface resistance;

Hereafter, a modification of the traditional Palmes diffusion tube by fitting a membrane at the open end of the tube is presented. The membrane is placed to avoid the effect of turbulence due to wind speed. Further optimisations of the volume of absorbent and number of meshes retaining the absorbent are also described. Finally, the sampler is placed in an air proof container and is ready to use in order to improve the quality of measurement.In order to evaluate the performance of the membrane-closed Palmes diffusion tube to monitor nitrogen dioxide (NO2), experiments were carried out in an exposure chamber. The relative effect of NO2, temperature, humidity, averaging time and wind speed on the uptake rate of the sampler were then studied. Among the uncontrolled variables, temperature and humidity are found to be the most important ones leading to variability of the uptake rate. Two equations, used to estimate the uptake rate are established. These equations were then applied on some field data and laboratory inter-comparison tests. The agreement between the chemiluminescence method and diffusive samplers changes from 20% of mean bias with the traditional Palmes diffusion tubes to 5% of mean bias with the membrane-closed Palmes tube (MCPT) at the same monitoring site. In the laboratory inter-comparison, the MCPT has shown to be able to correctly measure NO2 under two extreme exposure conditions in contrast with other diffusive samplers. The uncertainty of the sampler is evaluated. It fulfils the European Directive data quality objective of 25% for accuracy and therefore the sampler qualifies as an indicative method for NO2 monitoring.
Keywords: Diffusive samplers; Factorial design of experiments; Uncertainty; Validation; Membrane; Palmes diffusion tube;

The Asian dust aerosol model (ADAM) and the aerosol dynamic model with the output of the fifth generation of mesoscale model (MM5) in a grid of 30×30 km2 have been employed to simulate the temporal and spatial distribution of the Asian dust aerosol and the anthropogenic aerosol concentrations in East Asia for the period of 19–23 March 2002 when a severe Asian dust (Hwangsa) event was observed in Korea. The simulated aerosols are implemented to estimate radiative forcing at the surface and the top of atmosphere (TOA) with the use of the National Center for Atmospheric Research (NCAR) column radiation model (CRM) of community climate model 3 (CCM3). The results indicate that the ADAM model simulates quite well the spectral-mass concentration distribution with the R 2 value of 0.7 whereas the aerosol dynamic model underestimates the observed anthropogenic aerosol by a factor of 4 over Korea. The estimated mean total aerosol mass in the analysis domain for the period of 19–20 March 2002 is found to be about 880 mg m−2, of which 98% and 2% are, respectively contributed by the Asian dust aerosol and the anthropogenic aerosol. However, the direct radiative forcing contributed by the anthropogenic aerosol are about 40% of the mean radiative forcing at the surface (−11 W m−2) and 45% of the mean radiative forcing at TOA (−6 W m−2), implying the importance of the anthropogenic aerosol on the direct radiative forcings at both the surface and TOA. The difference between the radiative forcing at TOA and the surface that indicates the atmospheric absorption is found to be 5 W m−2, of which 3 and 2 W m−2 are, respectively contributed by the Asian dust aerosol and the anthropogenic aerosol, suggesting the importance of the Asian dust aerosol on the regional radiative energy balance especially in the high occurrence frequency season of spring.
Keywords: Aerosol dynamic model; Anthropogenic aerosol; Asian dust aerosol; Direct radiative forcing; Surface radiative forcing; Radiative forcing at the top of atmosphere;

Black crusts have been known for decades to be one of the major damage features affecting the built heritage in urban areas worldwide. Their patterns, surface distribution and composition have evidenced the key role played by carbonaceous particles of atmospheric origin, which have been studied on the basis of single particle analyses with the aim of identifying the sources. The paper intends to fill the existing gap on the quantification of the carbonaceous fraction within damage layers. Organic and elemental carbon (OC and EC) in damage layers on historic buildings were measured at different European urban sites. The data reported show how OC and EC concentrations and OC/EC ratio are typical of each site and provide essential in-put for an exhaustive investigation of black crust formation. The organic carbon concentration is found to predominate over the EC concentration at almost all the target sites. In view of foreseeable future trends of multipollutant deposition on the built heritage, the OC and EC concentrations become the most important components to be quantified within black crust. The paper is pioneering in presenting data directly correlated with the blackening encountered on European cultural heritage.
Keywords: Carbonaceous particles; Built heritage; Damage; Carbon measurement; Pollution change; Traffic effects;

Measurements of carbon dioxide (CO2) concentration carried out in the city of Rome showed an increase from 1995 (367±29 ppm mean yearly value) to 2004 (477±30 ppm, mean yearly value). The annual trend showed a peak in winter, 18% greater than the summer one correlated to traffic density (35±4 and 29±3 cars min−1 mean winter and summer value, respectively). The weekly trend had the lowest values (414±19 ppm) during the weekends when traffic density was 72% reduced. The daily trend had a peak in the early morning when traffic was the highest and the atmosphere was more stable. The critical zones of the city (B zones) had 3.5% CO2 concentration higher than the park (D zone) and 18% more than the control zones (E zones). An increase of air temperatures from the surrounding zones (20.0±4.1 °C) to the centre of the city (28.9±1.2 °C, mean between A and B zones) was observed.
Keywords: Carbon dioxide; Traffic levels; Urban area; Urbanistic characteristics;

With the burgeoning vehicle ownership in China, the emissions of certain trace pollutants are becoming more widespread and of more concern. We present results from the first measurements of platinum in airborne total suspended particulate matter (TSP) at a suburban (CityU) and a roadside (MK) sampling site in southern China at Hong Kong. TSP samples were taken with high volume air samplers at these sites with low and high traffic density, respectively, on a 2-day basis and were analyzed by inductively coupled plasma—dynamic reaction cell—mass spectrometry (ICP-DRC-MS). The results are similar from the use of two different isotopes: 194 and 195. The 48-h average Pt concentrations were 8.8 pg m−3 at CityU and 24.1 pg m−3 at MK, being higher at the site with greater traffic density, and were in the range from 6 to 38 pg m−3. The airborne Pt was found to be significantly correlated with vehicle tracer species (Zr and Ce) as well as with NO and NO x . The ratio Ce/Zr was the same at both sites whereas the ratios Pt/Zr and Pt/Ce were about 20% greater at the MK site, showing the different mobility of Pt, attributed to chemical and/or particle size effects.
Keywords: Platinum; Particulate matter; Catalytic converter; Vehicle emissions;

The carbonate content and the carbon and oxygen isotopic composition of carbonate were determined for 28 surface soil samples from northern China and 30 dust aerosol samples collected at four sites in northern China: Aksu, Dunhuang, Yulin and XiAn. The carbonate content and stable C isotopic composition show distinctly different values for dust from different sources, both vary inversely with annual mean precipitation and also vary as function of grain size. The δ 13C value in the aerosol is lower and the δ 18O higher than in local bulk surface soils because the particle-size distribution in the aerosol is skew toward smaller particles. At Aksu and Dunhuang, the dust aerosol shows a higher δ 13C value (average-0.148‰) and also a higher carbonate content (average 10.2%) compared with Yulin. The relative contributions of remote and local sources to Yunlin aerosol was estimated by a two component isotopic mixing equation using δ 13C data. At XiAn, the aerosols collected during a dust storm had higher δ 13C value than local fugitive dusts, indicating a significant contribution from long-range transport. Stable C isotopic composition provides a useful index for identifying putative sources for ambient dust aerosol, especially when used in combination with meteorological methods such as back trajectory analysis.
Keywords: Carbonate; Carbon and oxygen isotopes; Asian dust source;

Domestic wood burning and PM2.5 trace elements: Personal exposures, indoor and outdoor levels by Peter Molnár; Pernilla Gustafson; Sandra Johannesson; Johan Boman; Lars Barregård; Gerd Sällsten (2643-2653).
Personal exposures as well as indoor and outdoor levels of PM2.5 were measured with cyclones and impactors simultaneously in the winter of 2003 in a residential area where wood burning for domestic space heating is common. Twenty-four-hour samples from both wood-burning households (“wood burners”) and a reference group were analysed for mass and elemental concentration using energy dispersive X-ray fluorescence (EDXRF) and for black smoke (BS) concentration using an EEL 43 reflectometer. Wood-smoke particles made statistically significant contributions of K, Ca, and Zn for both personal exposure and indoor concentration, the median levels of these elements being 66–80% higher for the wood-burning group. In addition, Cl, Mn, Cu, Rb, and Pb were found to be possible markers of wood smoke, though levels of these were only significantly higher among the wood-burning group for either personal exposure or indoor concentrations. PM2.5 mass and S levels were not significantly elevated in wood burners, probably due to large variations in outdoor concentrations from long-distance transported air pollution. Personal exposure and indoor levels showed high correlations for all species, and the personal exposure levels were usually higher than or equal to the indoor levels. The associations between personal exposure and outdoor levels were generally weak except for outdoor S and PM2.5 levels that were both highly correlated with personal S exposure levels ( r s > 0.8 ) .
Keywords: Black smoke; Exposure assessment; Fine particles; X-ray fluorescence; Wood smoke markers;

Passive sampler for monitoring ambient nitric acid (HNO3) and nitrous acid (HNO2) concentrations by Andrzej Bytnerowicz; Maria Jose Sanz; Michael J. Arbaugh; Pamela E. Padgett; David P. Jones; Antonio Davila (2655-2660).
A passive sampler for collection of gaseous nitric acid (HNO3) and nitrous acid (HNO2) is based on a diffusion of ambient air through Teflon membrane and absorption of the pollutants on Nylasorb nylon filter. The sampler is simple in design, easy to make, inexpensive and resistant to harsh weather conditions. The sampler has been calibrated against honeycomb denuder systems in ambient southern California air and in controlled HNO3 exposures. It is more precise than the old open-face HNO3 sampler. It can measure wide ranges of ambient HNO2 and HNO3 concentrations for extended periods of time and can be used for regional-scale monitoring of the pollutants.
Keywords: Air pollution; Nitrogenous air pollutants; Passive sampler; Monitoring; Remote sites;

Coadsorption at the air/water interface as source of pollutant transfer to the atmosphere: The case study of benzene/cyclohexane traces and lead by Mustapha Sadiki; François Quentel; Catherine Elléouet; Ludovic Stéphan; René Olier; Mireille Privat (2661-2672).
The possible occurrence of polluted aerosols formed by a bubbling mechanism from hydrocarbon-rich aqueous surface layers was investigated in laboratory through the determination of hydrocarbon adsorption from diluted solutions.Benzene and cyclohexane both exhibited positive adsorption. Further to our previous demonstration of lead nitrate coadsorption with benzene near the solubility limit (Sadiki et al., 2003. Atmospheric Environment 37, 3551–3559) the present study revealed a positive coadsorption of lead nitrate with both hydrocarbons, even in diluted solutions.The use of the bubble-column (Wan, Tokunaga, 1998. Environment Science and Technology 32, 3293–3298) as an experimental tool is discussed as well as the physico-chemical mechanisms involved in adsorption and coadsorption processes with their impact on the environment.
Keywords: Benzene; Cyclohexane; Lead; Coadsorption; Bubbling;

Semi-analytical model for pollution dispersion in the planetary boundary layer by D.M. Moreira; U. Rizza; M.T. Vilhena; A. Goulart (2673-2681).
In this paper a time dependent semi-analytical model is discussed which overcomes the limits of the existing analytical ones. This model is compared both with the results of a numerical model and with experimental data in air quality applications. This approach is based on the Laplace transform technique, and can include both advanced eddy diffusivity and wind profiles. The numerical algorithm utilizes a mixed cubic-spline/Crank–Nicholson method within the locally one-dimensional (LOD) technique. The two approaches produce comparable results when considering the most important quantity in air-pollution application, that is the ground-level concentration distribution. These results are quite good for the semi-analytical model as its computer code runs much faster than the computer code for the numerical model. This is promising because this computer-based technique may be used for quantitative and qualitative estimations of pollutant distribution.
Keywords: Atmospheric turbulence; Transport and diffusion; Air-pollution modelling; Analytical and numerical techniques; Planetary boundary layer;

Long-term comparison of filter method and sensitive analyser in monitoring of sulphur dioxide by Sirkka Leppänen; Pia Anttila; Heikki Lättilä; Ulla Makkonen (2683-2693).
Co-located long-term routine measurements of sulphur dioxide with the impregnated filter method and a pulsed fluorescence analyser at four Finnish background stations were compared. The data consist of 9 years of parallel measurements at the Virolahti station and 8, 7 and 2 years in Utö, Oulanka and Ähtäri, respectively, between the years 1993–2001. During the whole study period, the daily SO2 concentrations measured with the analyser and the filter method showed excellent agreement in Virolahti (number of daily data pairs 2748, r 2 = 0.99 ) and Utö ( n = 2328 , r 2 = 0.97 ), and no systematic relative error between the two methods was found. Also in Oulanka ( n = 2131 , r 2 = 0.99 ) and Ähtäri ( n = 643 , r 2 = 0.97 ) the linear model described the data well. However, in Oulanka the analyser produced 16% and in Ähtäri 10% higher results than the filter method. The difference would decrease to 12% in Oulanka and to 8% in Ähtäri if the concentrations were given at the same reference pressure. At all stations also a small constant error (analyser>filter) of the order of 0.03–0.06 μg S m−3 was discerned. The role of nitrogen oxide, volatile organic compounds and water vapour interferences as well as extreme temperatures were studied but no clear systematic influence by them on the daily differences between the two methods was detected.
Keywords: Impregnated filter; Pulsed fluorescence; Field measurements; Interferences; RMA;