Atmospheric Environment (v.35, #18)
Forthcoming Papers (I-II).
Atmospheric alcohols and aldehydes concentrations measured in Osaka, Japan and in Sao Paulo, Brazil by Ha Thi-Hoang Nguyen; Norimichi Takenaka; Hiroshi Bandow; Yasuaki Maeda; Sergio T. de Oliva; Maria M.f. Botelho; Tania M. Tavares (3075-3083).
The use of alcohol fuel has received much attention since 1980s. In Brazil, ethanol-fueled vehicles have been currently used on a large scale. This paper reports the atmospheric methanol, ethanol and isopropanol concentrations which were measured from May to December 1997, in Osaka, Japan, where alcohol fuel was not used, and from 3 to 9 February 1998, in Sao Paulo, Brazil, where ethanol fuel was used. The alcohols were determined by the alkyl nitrite formation reaction using gas chromatography (GC-ECD) analysis. The concentration of atmospheric alcohols, especially ethanol, measured in Sao Paulo were significantly higher than those in Osaka. In Osaka, the average concentrations of atmospheric methanol, ethanol, and isopropanol were 5.8±3.8, 8.2±4.6, and 7.2±5.9 ppbv, respectively. The average ambient levels of methanol, ethanol, and isopropanol measured in Sao Paulo were 34.1±9.2, 176.3.±38.1, and 44.2±13.7 ppbv, respectively. The ambient levels of aldehydes, which were expected to be high due to the use of alcohol fuel, were also measured at these sampling sites. The atmospheric formaldehyde average concentration measured in Osaka was 1.9±0.9 ppbv, and the average acetaldehyde concentration was 1.5±0.8 ppbv. The atmospheric formaldehyde and acetaldehyde average concentrations measured in Sao Paulo were 5.0±2.8 and 5.4±2.8 ppbv, respectively. The C2H5OH/CH3OH and CH3CHO/HCHO were compared between the two measurement sites and elsewhere in the world, which have already been reported in the literature. Due to the use of ethanol-fueled vehicles, these ratios, especially C2H5OH/CH3OH, are much higher in Brazil than these measured elsewhere in the world.
Keywords: Methanol; Ethanol; Formaldehyde; Acetaldehyde; Brazil; Osaka; Alternative fuel;
Biomass and combustion characteristics of secondary mixed deciduous forests in Eastern Ghats of India by V.Krishna Prasad; Yogesh Kant; Prabhat K Gupta; C Sharma; A.P Mitra; K.V.S Badarinath (3085-3095).
Biomass quantities at three different sites in tropical moist mixed secondary deciduous forests before and after burning have been quantified in the forest patches cleared for shifting cultivation purposes. The main objective of the experiments was to study the spatial variability in the amount of biomass burnt and the contribution of different components viz., bole, branch, and mixed leaf litter in the burning process affecting the combustion factors. Species composition at the three sites varied with respect to each other. The total density of species before burning at the three sites for more than 10 cm diameter were found to be 3192 (site 1), 1194 (site 2) and 1444 (site 3) stems/area, respectively. Analysis of the results from girth-class and density relationships suggests that nearly 80% of the stems occurred in the range from 10–40 cm girth for site one, 64.2% in 10–55 cm girth class for the site two and more than 80% of stems in 10–40 cm girth class for the site three, indicating very poor and secondary nature of the forest. The fire intensity is found to be high for site one with 60 847 kJ s−1 m−1, when compared to 31 086 and 42 789 kJ s−1 m−1 for second and third sites, respectively. The values are comparatively higher than the mean value of 2566 kJ s−1 m−1 reported for savanna fires. The individual combustion completeness suggested that among the different components of biomass, branch material with less than 10 cm and upto 5 cm dbh contributed to more than 60% of combustion. Mixed leaf litter contributed to about more than 50% of individual combustion completeness at all the sites, with third site having the highest (84%). The contribution of dry biomass material having more than 70 cm diameter is found to be very low indicating that most of the trunks were burnt superficially. The overall combustion completeness suggested that mixed leaf litter and branch material contributed to most of the combustion. Of all the three sites, site three had been found to be having highest combustion completeness of about 30.04% when compared to 20.18% and 16.1% for first and second sites, respectively. In the study, comparison of combustion factors for different vegetation types has also been made.
Keywords: Biomass burning; Combustion factors; Tropical secondary mixed deciduous forests;
Variation of nitric oxide concentration before the Kobe earthquake, Japan by Tokiyoshi Matsuda; Motoji Ikeya (3097-3102).
The variation and spatial distribution of the atmospheric concentration of nitric oxide (NO) near the epicenter of the Kobe earthquake at local time 5:46, 17 January 1995 have been studied using data at monitoring stations of the local environmental protection agencies. The concentration of NO 8 days before the earthquake was 199 ppb, about ten times larger than the average peak level of 19 ppb, accompanying the retrospectively reported precursory earthquake lightning, increase of radon concentration in well water and of the counts of electromagnetic (EM) signals. The reported thunderstorm over the Japan Sea about 150 km away was too far for the thunder-generated NO to reach the epicenter area. The concentration of NO was also found to have increased before other major earthquakes (Magnitude>5.0) in Japan. Atmospheric discharges by electric charges or EM waves before earthquakes may have generated NO. However, the generation of NO by human activities of fuel combustion soon after holidays is enormously high every year, which makes it difficult to clearly link the increase with the earthquakes. The increase soon after the earthquake due to traffic jams is clear. The concentration of NO should be monitored at a several sites away from human activities as background data of natural variation and to study its generation at a seismic area before a large earthquake.
Keywords: Nitrogen oxides; Seismic electromagnetic signals (SEMS); Lightning; Radon; Environment;
Numerical study of atmospheric dispersion of a substance released from an industrial complex in the southern coast of Korea by Hyun Sun Oh; Young Sung Ghim (3103-3111).
Diurnal variations of wind field and pollutant dispersion in a complex terrain with a shoreline were investigated under the insolation conditions of summer and winter. The area is located in the south of the Korean Peninsula and includes a large petrochemical industrial complex. The Regional Atmospheric Modeling System (RAMS) was used in the simulation study. Initially, horizontally homogeneous wind fields were assumed on the basis of sounding data at the nearby upper-air station for days with morning wind speeds below 2 m s−1. On these days, the sea breeze prevailed in summer while the land breeze lasted for a few hours in the morning; the effect of synoptic winds was strong in winter with some inclusion of wind variations owing to the interaction between sea and land. The predicted wind direction at the location of the weather station captured an important change of the sea/land breeze of the observed one. In the morning, both in summer and winter, complicated wind fields with low wind speeds resulted in high pollutant concentrations almost all over the area. On the other hand, in the afternoon, the wind field was rather uniform and the terrain effects were not significant even in the mountainous area with the development of a mixing layer.
Keywords: Sea/land breeze; Complex terrain; Pollutant dispersion; Low wind speed; Mixing layer;
Leaves of Bauhinia blakeana as indicators of atmospheric pollution in Hong Kong by O.W Lau; S.F Luk (3113-3120).
Bauhinia blakeana was used as a biomonitor to monitor the air quality in Hong Kong. Equations were set up to relate the ambient iron, copper, zinc and lead concentrations with those in leaves of the biomonitor and good correlations were observed. The concentration of sulphate in the leaves of Bauhinia blakeana was found to be directly related to ambient sulphur dioxide and total suspended particulates. Using these equations the ambient pollutant levels in different districts of Hong Kong were determined quantitatively according to the concentrations of pollutants in leaves. As many residential buildings are close to congested roads, the ambient pollutant concentrations at selected roads were evaluated. Many temples are known to be heavily polluted with air particulates, and thus the air quality inside are suspected to be poor. The air quality inside temples may be reflected by the air quality outside these buildings, which were also assessed using the proposed method of biomonitoring. The levels of ambient lead and copper outside these temples were higher than their respective background levels while the levels of pollutants at the kerbsides were reported to be 10–300% higher than those of the background.
Keywords: Biomonitor; Bauhinia blakeana; Ambient pollutant concentrations; Heavy metals; Sulphur dioxide; Particulates; Hong Kong; Roads; Temples;
Flow patterns influencing the seasonal behavior of surface ozone and carbon monoxide at a coastal site near Hong Kong by K.S Lam; T.J Wang; L.Y Chan; T Wang; J Harris (3121-3135).
Surface O3 and CO were measured at Cape D’Aguilar, Hong Kong during the period of January 1994 to December1996 in order to understand the temporal variations of surface O3 and CO in East Asia–West Pacific region. The isentropic backward trajectories were used to isolate different air masses reaching the site and to analyze the long-range transport and photochemical buildup of O3 on a regional scale. The results show that the diurnal variation of surface O3 was significant in all seasons with daily O3 production being about 20 ppbv in fall and 10 ppbv in winter, indicating more active photochemical processes in the subtropical region. The distinct seasonal cycles of O3 and CO were found with a summer minimum (16 ppbv)–fall maximum (41 ppbv) for O3 and a summer minimum (116 ppbv)–winter maximum (489 ppbv) for CO. The isentropic backward trajectory cluster analyses suggest that the air masses (associated with regional characteristics) to the site can be categorized into five groups, which are governed by the movement of synoptic weather systems under the influence of the Asian monsoon. For marine-originated air masses (M-SW, M-SE and M-E, standing for marine-southwest, marine-southeast and marine-east, respectively) which always appear in summer and spring, the surface O3 and CO have relatively lower mixing ratios (18, 16 and 30 ppbv for O3, 127, 134 and 213 ppbv for CO), while the continental air masses (C-E and C-N, standing for continent-east and continent-north, respectively) usually arrive at the site in winter and fall seasons with higher O3 (43 and 48 ppbv) and CO (286 and 329 ppbv). The 43 ppbv O3 and 286 ppbv CO are representative of the regionally polluted continental outflow air mass due to the anthropogenic activity in East Asia, while 17 ppbv O3 and 131 ppbv CO can be considered as the signature of the approximately clean marine background of South China Sea. The very high CO values (461–508 ppbv) during winter indicate that the long-range transport of air pollutants from China continent is important at the monitoring site. The fall maximum (35–46 ppbv) of surface O3 was believed to be caused by the effects of the weak slowly moving high-pressure systems which underlie favorable photochemical production conditions and the long-range transport of aged air masses with higher O3 and its precursors.
Keywords: Trajectory; Ozone; Carbon monoxide; Transport; Photochemistry;
Spatial and temporal characteristics of urban atmospheric methane in Nagoya City, Japan: by A. Ito; I. Takahashi; Y. Nagata; K. Chiba; H. Haraguchi (3137-3144).
The spatial and temporal behavior of atmospheric methane (CH4) in the Nagoya metropolitan area was investigated in relation to the regional meteorological and topographical characteristics. It was found that the daily maximum CH4 concentrations in the central city area were observed when the northeast wind blew from the foothill of the northeastern mountainous area down into the central city areas, under stable atmospheric conditions. The large and active landfills are the major anthropogenic CH4 sources and are located at the hill sites in the northeast. Therefore, it was considered that the air mass with the high concentration of CH4 flowed from the landfill sites into the urban area, and exerted substantial influences on the spatial and temporal variations of atmospheric CH4 concentrations in the central city area.
Keywords: Environmental monitoring; Greenhouse gas; Urban area; Inversion layer; Wind sector analysis;
The composition of individual aerosol particle in the troposphere and stratosphere over Xianghe (39.45°N, 117.0°E), China by Li Xu; Kikuo Okada; Yasunobu Iwasaka; Keiichiro Hara; Yasuhiko Okuhara; Yukitomo Tsutsumi; Guangyu Shi (3145-3153).
A balloon observation was carried out on 22 August in 1993 from Xianghe Scientific Balloon Base (39.75°N, 117.0°E) near Beijing in China. Individual aerosol particles in the five samples collected in the troposphere and lower stratosphere were analyzed by using a transmission electron microscope equipped with an energy-dispersive X-ray (EDX) analyzer. Types of particles were classified by the quantitative EDX analysis and particle morphology. Following results were obtained by the analyses of aerosol particles in the radius range of 0.1–0.5 μm: (1) Sulfate particles were dominant (80%) in aerosol particles collected between 4 and 6 km altitude. (2) Sulfuric acid particles were present in 74% of particles at ∼8 km altitude, 91% at 11 km, 95% at 17 km and 88% at 21.2 km. (3) “S-rich” particles with K were collected both in the troposphere and lower stratosphere. It was considered that the particles containing K found at ∼5, ∼8 km altitude could originate from burning processes in the continent including the Tibetan plateau and be transported to the middle troposphere. (4) Sulfuric acid particles with Fe were present in 20–30% of sulfuric acid particles in the lower stratosphere. (5) Particles mainly composed of minerals were present in 6, 11% of particles at ∼5, ∼8 km, indicating the vertical transport to the upper troposphere. (6) Mineral particles which contain sulfuric acid and sulfate suggest the formation of sulfuric acid and sulfate on mineral particles by heterogeneous processes in the troposphere. (7) Sea-salt particles with and without minerals were collected in the troposphere and lower stratosphere, suggesting the vertical transport by convective clouds.
Keywords: Aerosol particle composition; Troposphere and stratosphere; Electron microscopy; EDX analysis;
Delineation of air-quality basins utilizing multivariate statistical methods in Taiwan by Tai-Yi Yu; Len-Fu W. Chang (3155-3166).
This study analyzed time-series data of air pollutants, O3 and PM10, to determine the division of air-quality basins in Taiwan by employing multivariate statistical methods, Varimax rotational method and cluster analysis. The databases of air pollutants, daily maximum 1-h O3 and daily mean PM10 concentrations, were obtained from the ROC Environmental Protection Administration (ROC EPA) for the period from 1 July 1993 to 30 June 1998. The Varimax rotational method allowed us to delineate five homogenous PM10 subregions that cumulatively accounted for 85.6% of the total variance. The time-series analysis of rotated component scores associated with the PM10 subregions revealed that all divided subregions presented a strong seasonal cycle. Four of five subregions had higher component scores and PM10 concentrations from November to January. One subregion experienced higher values from March to May. The use of Varimax approach and cluster analysis on the O3 and PM10 confirmed that O3 was more demonstrative of the air-quality basins in Taiwan. Both the Varimax rotational method and the cluster analysis have specific advantages for the division of air-quality basins. This study also proposes a delineation of five air-quality basins having homogenous O3 features as an alternative assignment of atmospheric carrying capacity control regions.
Keywords: Air-quality basins; Varimax rotational method; Cluster analysis; O3; PM10;
Spatial variation of mass concentration of roadside suspended particulate matter in metropolitan Hong Kong by L.Y Chan; W.S Kwok; S.C Lee; C.Y Chan (3167-3176).
This study conducted roadside particulate sampling to measure the total suspended particulate (TSP), PM10 (particles <10 μm in aerodynamic diameter) and PM2.5 (particles <2.5 μm in aerodynamic diameter) mass concentration in 11 urbanized and densely populated districts in Hong Kong. One hundred and thirty-three samples were obtained to measure the mass concentrations of TSP, PM10 and PM2.5. According to these results, the TSP, PM10 and PM2.5 mass concentrations varied from 94.85 to 301.63 μg m−3, 67.67 to 142.68 μg m−3 and 50.01 to 125.12 μg m−3, respectively. The PM2.5/PM10 ratio of all samples was 0.82 which ranged from 0.62 to 0.95. The PM levels and PM ratios in metropolitan Hong Kong significantly fluctuated from site-to-site and over time. The PM2.5 mass concentration in different districts corresponding to urban industrial, new town, urban residential and urban commercial were 77.64, 87.50, 106.96 and 88.54 μg m−3, respectively. The PM2.5 level is high in Hong Kong, and for individual sampling, more than 60% daily measurements exceeded the NAAQS. The mass fraction of PM2.5 in PM10 and TSP is relatively high when compared with overseas studies.
Keywords: TSP; PM10 and PM2.5; Spatial variation; Metropolitan; Hong Kong;
Roadside suspended particulates at heavily trafficked urban sites of Hong Kong – Seasonal variation and dependence on meteorological conditions by L.Y Chan; W.S Kwok (3177-3182).
In this study, the seasonal variation of different types of particulates was investigated in a fixed roadside station in heavily trafficked urban area of Hong Kong. Aerosol samples for total suspended particles (TSP), PM10 and PM2.5 were collected from June 1998 to May 1999 at a roadside site. Meteorological conditions such as relative humidity (RH), rainfall and prevailing wind direction were found to affect the mass concentration of TSP, PM10 and coarse particulates at roadside level. Large size particles had an apparent seasonal variation, with higher concentration level in winter and lower in summer. The dry continental winter monsoon and the wet oceanic summer monsoon are the dominating factors. On the other hand, annual variation of PM2.5 is relatively insignificant, suggesting that they are mainly from local traffic emission. PM10 accounted for 62% of the TSP, while PM2.5 accounted for 46%. The annual PM2.5/PM10 is high with PM2.5 responsible for 74% of PM10. In our heavily trafficked roadside fixed site, TSP exceeded the annual average of the Hong Kong Air Quality Objective by a factor of 1.53 while PM10 exceeded by 1.39. The annual average concentration of PM2.5 exceeded the National Ambient Air Quality Standard (NAAQS) annual average of 15 μg m−3 by a factor of 3.8 and is a cause of concern. A total of the 24 h average PM2.5 exceeded NAAQS by 33%. According to our data reported, fine particulate pollution is serious in Hong Kong.
Keywords: TSP; PM10; PM2.5; Seasonal; Metropolitan; Hong Kong;
Chemical composition of freshsnow samples from the southern slope of Mt. Everest region (Khumbu-Himal region, Nepal) by A. Marinoni; S. Polesello; C. Smiraglia; S. Valsecchi (3183-3190).
In 1998 fresh surface snow samples were collected, no more than 2 days after the snowfall, along the Khumbu valley, and its lateral valleys (Kongmala and Changri Nup), at the end of the summer monsoon period. Samples from the Island Peak and Pumori slopes were also collected by climbers during pre- and post-monsoon season at altitudes ranging from 5300 to 6100 m a.s.l. Conductivity, pH and major inorganic ions were measured in samples and relative field blanks. Chemical results were subjected to principal component analysis (PCA) in order to distinguish different sources of ions and study spatial and temporal distribution of ion concentrations. Two main factors, accounting for more than 80% of the total variance, were found. The two factors were correlated to two different sources, one representing local transport and background contribution, and the other related to monsoon circulation. Concentrations of the main ions were compared to those measured in other remote areas, with particular regard to elevated areas in Central Asia.
Keywords: Khumbu valley; Nepal; Freshsnow; Monsoon air mass; Inorganic ions; Ion Chromatography;
Transport and evolution of a winter-time Yellow sand observed in Korea by Byung-Gon Kim; Soon-Ung Park (3191-3201).
Long-range transport of mineral dust such as Yellow sand (YS) is not restricted to the springtime periods in Northeast Asia. A YS phenomenon was observed during 25–27 January 1999, which was a remarkably distinctive episode in the occurrence time and intensity that had ever observed in the wintertime in Korea. This YS event was traced to be originated from the arid region of central and eastern Asia; the Gobi desert and Loess plateau. The traveling speed of the dust storm was found to be about 70 km h−1 with it's horizontal size of larger than the whole Korean peninsula during this episode. Aerosol mass loadings changed by an order of magnitude within a few hours. The dominant ion components were SO4 2−, NO3 −, Ca2+ and Na+ during the passage of YS. The mode diameter of these compounds of YS was around 4 μm, compared to 0.4–0.9 μm after the passage of YS. SO4 2− and NO3 − concentrations were found to be well correlated with Ca2+ concentration in the coarse mode during the YS event, whereas they were well correlated with NH4 + concentration during the non-YS period, indicating a significant amount of SO4 2− and NO3 − formations on the Ca2+-rich coarse aerosol during the long-range transport of YS.
Keywords: Yellow sand; Long-range transport; SO4 2− and NO3 − formations;
A study of surface ozone and the relation to complex wind flow in Hong Kong by T. Wang; Y.Y. Wu; T.F. Cheung; K.S. Lam (3203-3215).
Ozone measurements made from 5 sites in Hong Kong have been analyzed, including those from one upwind, one downwind, and three urban locales. The data are analyzed in terms of the seasonal and diurnal trends. A subset of data in autumn is further analyzed to study the relationship between the ozone spatial pattern and wind flow as well as other meteorological parameters. The results show that averaged ozone levels at most sites exhibit maxima in autumn, which appears to be a unique feature for eastern Asia. On average the daily maximum 1-h concentrations are found to be higher in the western (normally downwind) site than those on the eastern side and in urban areas. Examination of surface wind patterns and other meteorological parameters suggest that elevated ozone concentrations on the western side occur during the days with intense solar radiation, light winds, and in the presence of a unique wind circulation. The wind reversal in the western parts under the “convergence” flow is believed to be an important cause of the high-ozone events observed there. Such wind flow may re-circulate/transport nearby urban plumes (in this case the Hong Kong–Shenzhen urban complex). Examination of chemical data from the western site has shown that averaged afternoon SO2 to NO x ratios on days with wind reversal are larger than those of typical urban Hong Kong and that a significant SO2 enhancement was clearly indicated on several occasions. The SO2 enhancement may be interpreted as being the evidence to suggest the contribution of regional sources and/or Hong Kong’s power plants (both containing high SO2). A case study has shown that when moderately strong northwesterly wind prevails, elevated ozone and SO2 can be transported to western Hong Kong from the inner Pearl Delta region. This study has also indicated that under the impact of ENE winds the eastern side of Hong Kong is not frequently affected by the re-circulating ozone plumes present in the western side.
Keywords: Ozone pollution; Seasonal trend; Surface wind; Land/sea breezes; Pearl River Delta;