Atmospheric Environment (v.37, #1)

Particulate matter in the underground of Stockholm by Christer Johansson; Per-Åke Johansson (3-9).
The concentrations of PM10 and PM2.5 were measured during 2 weeks at an underground station in central Stockholm. The instrument, an automatic TEOM monitor (Tapered Element Oscillating Microbalance), was placed on the platform in the centre of the station. During weekdays between 7 a.m. and 7 p.m. the average PM10 and PM2.5 concentrations were 470 and 260  μg/m 3 , respectively. These levels are a factor 5 and 10 times higher than the corresponding values measured in one of the busiest streets in central Stockholm.The concentrations in the underground followed closely the train traffic intensity. The levels were very similar from one day to the next. During Saturdays and Sundays the levels decreased slightly due to less frequent train passages. Additional measurements were performed right after the tunnel had been washed. Tunnel walls and railway tracks between the platforms of the underground system were washed using water. Only a slight reduction of the PM10 levels (approximately 13%) could be observed during a few days after the water treatment. For PM2.5 the reduction was even less, about 10% lower levels could be seen. This might indicate that particles from tunnel walls and tracks make only a minor contribution to the observed levels.These results confirm earlier unpublished measurements showing high levels of PM in the underground of Stockholm. Substantially, elevated particle exposure levels have also been reported in several earlier studies in the underground of London, UK.
Keywords: PM10; PM2.5; Population exposure; Underground rail; TSP; Indoor levels; Transport microenvironment;

The contribution of megacities to regional sulfur pollution in Asia by Sarath K Guttikunda; Gregory R Carmichael; Giuseppe Calori; Christina Eck; Jung-Hun Woo (11-22).
Asia is undergoing rapid urbanization resulting in increasing air pollution threats in its cities. The contribution of megacities to sulfur emissions and pollution in Asia is studied over a 25-year period (1975–2000) using a multi-layer Lagrangian puff transport model. Asian megacities cover <2% of the land area but emit ∼16% of the total anthropogenic sulfur emissions of Asia. It is shown that urban sulfur emissions contribute over 30% to the regional pollution levels in large parts of Asia. The average contribution of megacities over the western Pacific increased from <5% in 1975 to >10% in 2000. Two future emission scenarios are evaluated for 2020—“business as usual (BAU)” and “maximum feasible controls (MAXF)” to establish the range of reductions possible for these cities. The MAXF scenario would result in 2020 S-emissions that are ∼80% lower than those in 2000, at an estimated control cost of US $87 billion per year (1995 US$) for all of Asia. An urban scale analysis of sulfur pollution for four megacities—Shanghai, and Chongqing in China; Seoul in South Korea; and Mumbai (formerly Bombay) in India is presented. If pollution levels were allowed to increase under BAU, over 30 million people in these cities alone would be exposed to levels in excess of the WHO guidelines.
Keywords: Sulfur pollution; Urban pollution; Population exposure;

Formaldehyde and acetaldehyde in a high traffic street of Rio de Janeiro, Brazil by Sérgio M Corrêa; Eduardo M Martins; Graciela Arbilla (23-29).
The data for formaldehyde and acetaldehyde levels in ambient air of the city of Rio de Janeiro, obtained in the period from 4 December 1998 to 17 January 2001 is presented. A total of 28 samples were collected at a downtown area, where emissions may be mainly attributed to the vehicular fleet. Values between 1.52 and 54.31 ppb for formaldehyde and between 2.36 and 45.60 ppb for acetaldehyde were obtained. The high acetaldehyde/formaldehyde ratios (0.76 to 1.61) are a consequence of the use of oxygenated fuels. Brazilian cities are unique in that the vehicles use hydrated ethanol (over 4 million of light duty vehicles), gasohol (a mixture with gasoline and 24% v/v of ethanol) and diesel fuels. The analysis of vehicle exhaust and model simulations of the air quality in August and December 1999, confirmed that the high levels of acetaldehyde could be attributed to direct emissions of the vehicular fleet and to the photochemical initiated oxidation of organic compounds.
Keywords: Formaldehyde; Acetaldehyde; Vehicular emissions; Ethanol; Air quality simulation;

Characterization of chemical species in PM2.5 and PM10 aerosols in Hong Kong by K.F Ho; S.C Lee; Chak K Chan; Jimmy C Yu; Judith C Chow; X.H Yao (31-39).
Aerosol samples for PM10 and PM2.5 were collected in wintertime from November 2000 to February 2001 at three different sampling locations in Hong Kong. PM10 and PM2.5 were collected by high-volume (hi-vol.) samplers and the concentrations of major elements, ions, organic and elemental carbons were quantified. The ratios of PM2.5/PM10 were 0.61 and 0.78 at the PolyU campus and Kwun Tong (KT), respectively. These results indicated that the concentrations of PM2.5 contribute the majority of the PM10 fraction. The concentrations of anthropogenic species (e.g. Pb and Cu) in PM10 and PM2.5measured at urban areas were generally higher than at an urban background site (Hok Tsui, HT). The major fractions of sulfate at three monitoring sites are non-sea-salts (nss) sulfates. Although HT is located in coastal areas, the contribution of sea salts to sulfate in fine particles was small, indicating a substantial anthropogenic origin. The OC/EC ratios were less than 2 in PolyU and KT monitoring stations for PM10 and PM2.5. However, the OC/EC ratios were over 3 at HT for both PM10 and PM2.5. This indicates the presence of secondary organic aerosols. Correlations between OC and EC as well as OC and sulfate in HT during both seasons were used to prove that atmospheric transport and transformation of anthropogenic organic species from northeastern area was the dominant source in winter. The chemical composition of the samples was reconstructed from the observed elemental composition. The contribution of the seven components, namely crustal matter, sea salt, ammonium, sulfate, nitrate, elemental carbon and organic matter accounted for 77–84% of the PM10 and PM2.5 mass in the urban area (PolyU and KT) and 74% for Hok Tsui (HT). Sulfate, organic matter and elemental carbon are the major constituents in particles especially in PM2.5 collected at PolyU and KT. The major constituents of PM10 in HT are sea salt and sulfate.
Keywords: Chemical composition; Urban PM10 and PM2.5; Organic carbon; Elemental carbon; Reconstruction of chemical composition;

Chemical mass balance source apportionment of PM10 in an industrialized urban area of Northern Greece by C Samara; Th Kouimtzis; R Tsitouridou; G Kanias; V Simeonov (41-54).
Ambient PM10 were sampled at three sites in an industrialized urban area of Northern Greece during June 1997–June 1998 and analyzed for 17 chemical elements, 5 water-soluble ions and 13 polycyclic aromatic hydrocarbons. In addition, chemical source profiles consisting of the same particulate components were obtained for a number of industrial activities (cement, fertilizer and asphalt production, quarry operations, metal electroplating, metal welding and tempering, steel manufacture, lead and bronze smelters, metal scrap incineration), residential oil burning, non-catalyst and catalyst-equipped passenger cars, diesel fuelled taxis and buses, as well as for geological fugitive sources (paved road dust and soil from open lands). Ambient and source data were used in a chemical mass balance (CMB) receptor model for source identification and apportionment. Results of CMB modeling showed that major source of ambient PM10 at all three sites was diesel vehicle exhaust. Significant contribution from industrial oil burning was also evidenced at the site located closest to the industrial area.
Keywords: Source profiles; Road dust; Soil; Vehicle exhaust; Industrial emissions; Metals; Ionic components; PAHs;

A new inventory of ammonia emissions from Irish agriculture by B.P Hyde; O.T Carton; P O’Toole; T.H Misselbrook (55-62).
Agriculture plays a vital role in the Irish economy, accounting for 3.5% of the gross domestic product (GDP) in 2000. Grassland farming and, in particular, cattle rearing and dairying accounts for more than 90% of farming activity. In addition, there have been significant increases in the number of sheep, pigs and poultry over the last twenty years. As a consequence, gaseous nitrogen (N) emissions have shown a clear upward trend. Following the adoption of the United Nations Economic Commission for Europe (UNECE) Gothenburg protocol (Protocol to the 1979 convention on long-range transboundary air pollution to abate acidification, eutrophication and ground-level ozone. United Nations Economic Commissions for Europe (UNECE), Geneva.), Ireland has to achieve a 9% reduction in national ammonia (NH3) emissions between 1990 and 2010. The agricultural sector accounts for virtually all NH3 emissions in Ireland. It is on this basis that a new inventory of NH3 emissions from agriculture has been produced. This paper describes the adoption of the UK national inventory model to Irish agricultural systems, the results of model calculations and the measures available to enable compliance with national targets and areas within the inventory, which require further investigation. Estimated total emissions from Irish agriculture were 89.9 and 91.8 kt NH3-N for 1991 and 2010, respectively. Cattle farming accounts for more than 75% of total emissions. The largest emission factors found included 46.9 g NH3-N lu−1  d−1 for cattle housing, 29.5 g NH3-N lu−1  d−1 for pig housing and 150 g NH3-N lu−1  d−1 for housed broilers (lu being equivalent to 500 kg live weight). In addition, model predictions for the year 2010 showed that without any abatement strategies being implemented, NH3 emissions would exceed the agreed national emission reduction target by 12%. It was also found that strategies for reducing emissions from the land spreading of manure offer the greatest potential to achieve target levels.
Keywords: Ammonia emission; Inventory; Emission factor; Housing; Land spreading; Storage;

The ozone (O3) phytotoxicity in rural areas of Catalonia (NE Spain) and the biomonitoring capacity of Bel-W3 tobacco (Nicotiana tabacum) cultivars were assessed by determining the percentage of leaf area injured by ozone in plants of this cultivar exposed from spring to autumn since 1995–1999. The study was conducted simultaneously on nine field sites where ground level ozone concentrations and meteorological parameters were continuously monitored. Geographical, seasonal and annual variations of ozone damage rate and their links with meteorological conditions were studied. Ozone concentrations and leaf damage increased at the end of spring and the beginning of summer. Coastal sites generally presented higher O3 concentrations than inland and mountain sites. These mountain sites were the most sensitive ones to ozone toxicity. The ozone concentrations correlated well with ozone injury. However, at this local scale the ozone levels did not fully account for all the observed injury (only 11%). The response of tobacco plants to ozone concentrations and therefore its biomonitoring capacity depended also on different environmental conditions, mainly those linked to stomatal behaviour such as vapour pressure deficit. The categorization of leaf damage in 10% intervals and its averaging throughout the whole study period and the whole region, strongly improved (99% of variance accounted) the relationship with ozone concentrations expressed as AOT20 (accumulated over a cut-off of 20 ppbv). N. tabacum cultivar Bel-W3 is thus a very good biomonitor of ozone concentrations in the long term at the regional scale. Taking into account the phytotoxical response of this sensitive tobacco cultivar, we propose the 1.28 ppmv  h biweekly AOT40 (with a solar radiation threshold of 50 W m−2) as a damage threshold level for sensitive species.
Keywords: Damage levels; Mediterranean conditions; Nicotiana tabacum Bel-W3; Ozone; VPD;

Levels of benzene, toluene, ethylbenzene and the xylenes (BTEX) in different indoor microenvironments such as offices, homes, schools, shopping malls and restaurants were investigated in Hong Kong. Different indoor environments including six offices, six homes, six air-conditioned classrooms, six shopping malls and four restaurants were selected in Hong Kong for indoor and outdoor BTEX measurement. This study is aimed to determine qualitatively or semi-quantitatively sources of BTEX. Source identification is possible by determining the indoor/outdoor (I/O) concentration ratio. An I/O ratio>1 was considered as an indicator for indoor sources. For BTEX in different indoor environments except for schools, some of the pollutants were dominated by outdoor sources while others mainly originated from indoor sources. In schools, however, the BTEX predominantly originated from outdoor sources. The potential sources of BTEX in indoor environments were also identified by using principal component analysis and nonparametric Kruskal–Wallis test. The number of variables was reduced to two and one new factors for indoor and outdoor data, respectively. These factors were related to certain source characteristics. It is shown that the type of land use, the use of printers, the traffic condition, the cooking style, the type of gas stove, smoking and internal decoration strongly influence the indoor concentrations of BTEX (p<0.05). Significant difference of BTEX concentrations in the five types of indoor environments were also observed (p<0.05).
Keywords: Indoor air pollution; BTEX; I/O ratios; Statistical analysis; Principal component analysis;

Twenty-four-hour concentrations of PM10 and black smoke (BS) were measured during two winter and one summer periods in a small village in the central part of the Czech Republic. Both the PM10 and BS were highly correlated during the two heating seasons (0.740 in the first and 0.768 in the second winter campaign, respectively). The correlation dropped to 0.567 during the summer period. Negative correlation between winter BS and wind velocity (−0.543 and −0.486) showed a close association between air pollution from combustion and low air mass movement in the locality during heating seasons. No correlation between BS and wind velocity was found during summer (0.057). Both PM10 and BS were negatively correlated with minimum daily temperature during both winter seasons as well as during the summer season. Comparison of PM10 data from the village with those from Prague, the Czech capital, showed that average particulate matter concentrations in the rural site were higher during all the three seasons studied. Recommended 24-h limit for PM10 in the European Union (50 μg m−3) was exceeded in 26% and 33% of days measured in the small village while only in 17% and 15% of days measured in Prague, for the first and second winter, respectively. Good association between data from the village with those from Prague suggests, on the one hand, that some effect of particulate matter transport from the city to the rural site cannot be excluded but, on the other hand, that good accord may be caused by similar climatic conditions of the two settlements. The results of the study support the idea that traditional heating in villages may represent an important air pollution problem.
Keywords: Particulate matter; Rural air quality; Solid fuel combustion; Harvard impactor;

PM10 was sampled on weekdays and at weekends in Dundee, a coastal urban area in the UK, for 1 year. The chemical compositions of 59 PM10 samples were analysed by using wet chemical analysis methods. An atomic absorption spectrophotometer was used to analyse metal elements (Ca, Mg, Zn, Cu, Ni and Pb) while a high-performance liquid chromatography was used to analyse ions (SO4 2−, NO3 , Cl, NH4 +, Na+ and K+). The meteorological factors which may affect the concentration and chemical composition of PM10 have been discussed. The possible sources for PM10 were analysed by comparing contributions of wind aspects with wind direction frequencies. The concentration of PM10 in Dundee is low in comparison with other known sites around the world. There are no obvious differences between concentrations and chemical composition of weekday and weekend samples. The impact of meteorological factors on PM10 concentrations and chemical composition is not immediately apparent. The European continent is to be a major source of SO4 2−, NO3 and NH4 +. However, Ca and K+ originate from different sources. The loss reaction of particulate Cl is stronger for marine aerosol from the North Sea than that from the Atlantic Ocean. The trace elements with complex sources originate mainly from local emissions.
Keywords: PM10; Chemical composition; Temporal trends; Sources; Wind aspect;

The metropolitan region of São Paulo (17.8 million inhabitants) presents serious air quality problems. An official network monitors key air pollutants, however, there is no regular program of evaluation of the wet deposition and data about rainwater composition is scarce. Opening a series of articles on this subject, capillary zone electrophoresis with contactless conductivity detection (CZE-CCD) is proposed and applied as a quick and inexpensive alternative to ion chromatography for the determination of the ionic composition of rainwater. Excellent resolution of the peaks and sufficient sensitivity were obtained for major ions. Switching from anion to cation determination is fast (30 min) and as simple as inverting the polarity of the voltage supply and changing the modifier added to the buffer solution. CZE-CCD was applied to the study of wet-only deposition collected in São Paulo during the period from May l997 to March 1998. The volume weighted means of the anions, sulfate, nitrate and chloride, were, respectively, 17, 22 and 29 μmol l−1. Among the cations, ammonium was the dominating one, with 28 μmol l−1, followed by calcium, 23 μmol l−1, sodium, 12 μmol l−1, and potassium, 5.8 μmol l−1. The wet flux of these anions and cations were, respectively, 2.5, 2.2, 1.6, 0.78, 1.4, 0.43 and 0.35 g m−2  yr−1. By attributing all sodium to marine origin, half of the chloride and more than 90% of all other ions are ascribable to continental/anthropogenic sources. Literature data for rainwater from inland regions (∼200 km apart from São Paulo) reveals lower deposition of all ions but H+. Absorption of NH3 and incorporation of calcium carbonate, mainly in the metropolitan region itself, accounts for decreased acidity. The enrichment in all other ions during the studied period indicates the prevalence of the anthropogenic emissions from the metropolis over continental sources and explains the high correlation between the ions NO3 , SO4 2−, and NH4 +; the same ions responsible for a factor that, alone, explains 42% of the variability in the PCA.
Keywords: Wet-only deposition; Rainwater; Acid rain; Ion analysis; Capillary electrophoresis;

Wet-only deposition samples were collected at a site in the urban area of the São Paulo metropolis between February (end of the rainy summer) and October (beginning of spring) 2000, an atypical period due to rainfall 40% below the 30-year average. The majority ions in rainwater were measured by capillary zone electrophoresis with contactless conductivity detection, CZE–CCD, applied for the first time to the organic anions acetate and formate. The volume weight mean (VWM) concentrations of the majority anions NO3 , SO4 2− and Cl were, respectively, 15.6, 9.5 and 4.7  μmol l −1 . The VWM concentration of HCOO t, (HCOO+HCOOH) was 17.0  μmol l −1 , about twice the 8.9  μmol l −1 of CH3COO t. The VWM concentration of free H+ was low (16.9  μmol l −1 ), corresponding to pH 4.77. This denotes the relevance of species like ammonia, analyzed as NH 4 +  (VWM=27.9  μmol l −1 ), and calcium carbonate ( VWM=5.3  μmol l −1   Ca 2+ ) as partial neutralizers of the acidity. By hypothetically assuming that H+ is the only counterion of the non-sea-salt fraction of the dissociated anions, their contribution to the total potential acidity would decrease in the following order: sulfate (29%), formate (29%), nitrate (26%), acetate (15%) and chloride (1%). The 44% potential participation of the carboxylic acids reveals their importance to the acidity of São Paulo's rainwater during the study period. Direct vehicular emission of lower carboxylic acids and aldehydes (in particular, acetic acid and acetaldehyde) is singularly high in the metropolis due to the extensive use of ethanol and gasohol (containing ∼20% of ethanol) as fuels of the light fleet of 5.5 million cars; in addition, regional atmospheric conditions favor the photochemical formation of the acids, since concentrations of ozone and aldehydes are high and solar irradiation is intense at the 23°34′S latitude. The presence of higher concentrations of HCOOH than CH3COOH indicates a prevalence of its photochemical production by H2CO oxidation in the atmosphere.
Keywords: Carboxylic acids; Acid rain; Rainwater; Electrophoresis; Acetate; Formate;

Authors response by Mari Ito; Myron J. Mitchell; Charles T. Driscoll (135-138).

Size distribution of fine atmospheric aerosol was measured at K-puszta, Hungary during summer and winter of 2000 and spring and autumn of 2001. The sampling was carried out by an electrical low pressure impactor which fractionated fine particles (d<1.7 μm) in eight size ranges. In this paper diurnal and seasonal variations of the concentration and size distribution of fine sulfate, total carbon (TC) and water soluble organic compounds (WSOC) are presented. The results indicate that the concentrations of sulfate, TC and WSOC are different in different seasons. Potential sources of these variations are briefly discussed.
Keywords: Diurnal and seasonal variation; Size distribution of sulfate; Total carbon and water soluble organic compounds (WSOC); Fine aerosol particles; Rural air; Hungary;

Methane emissions from natural peatlands in the northern boreal zone in Finland, Fennoscandia by Jari T Huttunen; Hannu Nykänen; Jukka Turunen; Pertti J Martikainen (147-151).
Methane (CH4) emissions were measured over two snow-free seasons from ten natural minerotrophic peatlands in the northern boreal zone of Finland using a static chamber technique. The daily CH4 fluxes at the sites ranged from −2.9 to 790 mg m−2  d−1. At nine wet fens, representing three ecological peatland classes, the seasonal mean CH4 emissions were 8.1–250 mg m−2  d−1 during a dry summer, and 15–330 mg m−2  d−1 during a wet summer. At these sites, the mean CH4 emission correlated positively with the mean water table level (r 2=0.64). The driest site (herb-grass spruce mire) showed the lowest CH4 emissions, with the seasonal averages being below 1 mg m−2  d−1. The CH4 emissions from these natural northern boreal peatlands in the main aapa-mire zone were similar or higher than those reported from other boreal peatlands in Finland and elsewhere, probably attributable to the high fertility and moisture of the northern boreal sites, characteristics typical of peatlands in the aapa-mire zone. Thus, the aapa mires in the boreal zone in Fennoscandia, Canada and Russia should be a larger natural source for atmospheric CH4 than estimated in the global inventories for wetland CH4 emissions.
Keywords: Aapa mires; CH4 budget; Field measurements; Greenhouse gas emissions; Natural sources; Natural wetlands;