Atmospheric Environment (v.36, #21)

Glaciochemical records from a Mt. Everest ice core: relationship to atmospheric circulation over Asia by S. Kang; P.A. Mayewski; D. Qin; Y. Yan; S. Hou; D. Zhang; J. Ren; K. Kruetz (3351-3361).
Glaciochemical records recovered from an 80.4 m ice core in the East Rongbuk (ER) Glacier (elevation: 6450 m) on the northern slope of Mt. Everest provide a reconstructing of past climate for the period AD 1846–1997. Empirical orthogonal function (EOF) analysis on the eight major ion (SO4 2−, Mg2+, Ca2+, Na+, Cl, NH4 +, K+, and NO3 ) time-series reveals inter-species relations and common structure within the ER glaciochemical data. The first two EOF series (EOF1-ions and EOF2-ions) are compared with instrumental data of sea level pressure (SLP) to demonstrate that the EOF-ions series display strong connections to winter (January) and summer (July) SLP over the Mongolian region. The positive relationship between EOF1-ions and the Mongolian High (MongHi) series suggests that enhanced winter MongHi strengthens the transport of dust aerosols southward from arid regions over central Asia to Mt. Everest. The close correspondence between EOF2-ions and the summer Mongolian Low (MongLow) indicates that the deeper MongLow, which is related to the stronger Indian Monsoon, contributes to a decrease in summer dust aerosols. Therefore, the ER ice core record comprises two assemblages of crustal species, each transported from different source regions during different seasons. EOF1-ions represents the majority of the crustal species and is related to winter atmospheric circulation patterns. These species are mainly transported from arid regions of central Asia during the winter dry season. EOF2-ions represents crustal species transported by summer atmospheric circulation from local/regional sources in the northern and southern Himalayas.
Keywords: Major ions; Ice core; Dust aerosols; Sea level pressure; Mt. Everest;

This study examined commuter’s exposure to respirable suspended particulate matters while commuting in public transportation modes. The survey was conducted between October 1999 and January 2000 in Hong Kong. A total of eight public transportation modes, that are bus, tram, public light bus, taxi, ferry, Kowloon–Canton Railway, Mass Transit Railway and Light Rail Transit, were selected in the study. They were grouped into four categories: (T1) railway transport; (T2) non-air-conditioned roadway transport; (T3) air-conditioned roadway transport and (T4) marine transport. Both PM10 and PM2.5 levels were investigated. The results indicate that the particulate level is greatly affected by the mode of transport as well as the ventilation system of the transport. The overall average PM10 concentration level in T2 (147 μg m−3) is the highest and is followed by T4 (81 μg m−3) and T3 (65 μg m−3). The PM10 level in T1 (50 μg m−3) is the lowest. Notably, the commuter exposure in tram (175 μg m−3) is the highest among all the monitored commuting modes. Commuting modes such as railway and air-conditioned vehicle are recommended as a substitute for non-air-conditioned vehicle. The PM2.5 to PM10 ratio in transports ranged from 63% to 78%. Higher PM2.5 to PM10 ratio is found in vehicles with air-conditioning system. For the double deck vehicle, higher PM10 level has resulted in the lower deck. The average upper-deck to lower-deck PM10 ratio is 0.836, 0.751 and 0.738 in air-conditioned bus, non-air-conditioned bus and non-air-conditioned tram, respectively. Typical concentration profiles in different transports are also presented.
Keywords: Public transportation modes; PM10; PM2.5; Commuter exposure; Vehicle exhaust;

Air pollution in the Krusne Hory region, Czech Republic during the 1990s by H.A Bridgman; T.D Davies; T Jickells; I Hunova; K Tovey; K Bridges; V Surapipith (3375-3389).
Emissions from the Black Triangle Region were considered to be the major source of air pollution problems in Europe during the 1990s. This discussion reviews the changes in emissions and pollution concentrations in the Krusne Hory Region (Czech Republic) in the winter half of the year during most of the past decade, and describes the relationships with meteorology. Sulfur dioxide (SO2) is used as the example pollutant. The results show a decrease in pollution concentrations since 1996, as air pollution control and management strategies for important point sources take effect. The winter of 1995–1996 was especially harsh in the number of pollution episodes. Correlations between SO2 and meteorological parameters are inconsistent. Wind direction provides the best relationship at monitoring stations along the Krusne Hory Plateau, with wind speed and temperature more variable depending on month and location. For the valley stations, higher SO2 concentrations are strongly related to colder temperatures, higher relative humidities, and lower wind speeds. A case study during the winter of 1995–1996 (November 9–15) illustrated the importance of synoptic high pressure and a low-level inversion in minimizing plume dispersion from point sources. Specific sources of SO2 affecting each station could thus be identified.
Keywords: Krusne Hory; Meteorology; Sulfur dioxide; Plume dispersion; Episodes;

Monoterpene fluxes measured above a Japanese red pine forest at Oshiba plateau, Japan by A. Tani; S. Nozoe; M. Aoki; C.N. Hewitt (3391-3402).
Monoterpene fluxes above a Japanese red pine (Pinus densiflora) forest in Japan were measured with a heat balance method from May to November 2000. The most abundant monoterpenes were α-pinene and limonene+β-phellandrene. Degradation losses of the major monoterpenes by the reactions with ozone and OH during transfer between the two sampling heights were estimated to be negligibly small. The highest values of average fluxes were observed in June measurement period, with values for α-pinene and limonene+β-phellandrene of 0.6 and 0.5 nmol m−2  s−1. Their average fluxes in September, October and November measurement periods were almost the same and lowest. Vertical profiles of monoterpene concentrations inside the forest suggest that large amounts of monoterpenes are accumulated in the aerial space in the forest and transferred to the atmosphere above. The difference between logarithms of measured and calculated total monoterpene fluxes, ln  F mea –ln  F cal , had positive values in many morning measurements and negative values in most late afternoon measurements, indicating that monoterpenes accumulated during the night were transported to the upper atmosphere the next morning and they began to accumulate again in the late afternoon, following a decrease of turbulent mixing. Leaf wetness effect was also considered and, finally, a simple model was proposed to explain controlling parameters for monoterpene flux above the forest.

Hourly data of PM10 concentration collected from an air quality-monitoring network has been analyzed over Taiwan from 1994 to 1999. Fourteen sites from 72 monitoring stations were selected to evaluate the spatial and seasonal variations in the regions of north, southwest, south, east and National Park. The selected monitoring sites are located in a suburban environment, except Nantz and Linyuan that are located in industrial areas. Moreover, Yangming and Hengchuen are located in National Park. Spatial and seasonal variations of PM10 concentrations are rather large over Taiwan. Annual average in south is approximately six times higher than in National parks. In northern sites, the highest concentration occurs in March–May, which is attributed to the occurrence of dust storms in arid regions of central Asia and the transport of dust by northeasterly monsoon. A marked seasonal variation of PM10 concentrations can be observed both in southwestern and southern regions. The pattern is characterized by high concentrations in winter and low in summer. Appearance of the highest monthly PM10 concentration in winter of south may be in part due to the lowest number of monthly precipitation days and low temperature, both of which occurred in winter. The frequency of PM10 daily mean concentration for exceeded 150 μg m−3 is 15% during winter in south, which reflects the serious pollution problem there. Monitoring sites in National Park are representatives of remote environments, but the PM10 concentrations are still affected by the dust storms and human activities.
Keywords: PM10; Air quality-monitoring network; Taiwan; Dust storms; Precipitation days;

Factors affecting the distribution and exchange of total gaseous mercury (Hg) were investigated over a bare paddy field at Hari, a relatively clean district at Kang Hwa Island, Korea in late March 2001. The Hg concentrations were quantified at two heights (1 and 5 m above the ground), and then combined with micrometeorological measurements of turbulent exchange coefficients for flux computation. During the 8-day period of measurements, mean concentrations of Hg (3.72 ng m−3, N=164) were lower than those reported from urbanized/industrialized areas but higher than the background concentration (i.e., 1–2 ng m−3). The Hg fluxes, however, were comparable to those reported in the literature for polluted environments and showed clear diurnal pattern with maximum (∼600 ng m−2  h−1) during midday and the minimum (∼100 ng m−2  h−1) at nighttime. Occasionally, at nighttime when the turbulent mixing was weak under stable conditions, a deposition of Hg was observed at much lower rates (about −32.3 ng m−2  h−1). The rate of Hg emission tended to increase with increasing air/soil temperatures and pollutant levels under enhanced turbulent mixing. By contrast, dry deposition of Hg seemed to be related to the increase of certain pollutants such as fine particles (PM 2.5) and CO. Overall, the bare paddy field was a strong source of Hg with the daily net Hg emission of 4.4 μg m−2 during the measurement period.
Keywords: Total gaseous mercury; Flux; Mobilization; Distribution; Background; Source; Asian dust;

Mixing ratios of volatile organic compounds (VOCs) in the atmosphere of Karachi, Pakistan by Barbara Barletta; Simone Meinardi; Isobel J Simpson; Haider A Khwaja; Donald R Blake; F.Sherwood Rowland (3429-3443).
Mixing ratios of carbon monoxide (CO), methane (CH4), non-methane hydrocarbons, halocarbons and alkyl nitrates (a total of 72 species) were determined for 78 whole air samples collected during the winter of 1998–1999 in Karachi, Pakistan. This is the first time that volatile organic compound (VOC) levels in Karachi have been extensively characterized. The overall air quality of the urban environment was determined using air samples collected at six locations throughout Karachi. Methane (6.3 ppmv) and ethane (93 ppbv) levels in Karachi were found to be much higher than in other cities that have been studied. The very high CH4 levels highlight the importance of natural gas leakage in Karachi. The leakage of liquefied petroleum gas contributes to elevated propane and butane levels in Karachi, although the propane and butane burdens were lower than in other cities (e.g., Mexico City, Santiago). High levels of benzene (0.3–19 ppbv) also appear to be of concern in the Karachi urban area. Vehicular emissions were characterized using air samples collected along the busiest thoroughfare of the city (M.A. Jinnah Road). Emissions from vehicular exhaust were found to be the main source of many of the hydrocarbons reported here. Significant levels of isoprene (1.2 ppbv) were detected at the roadside, and vehicular exhaust is estimated to account for about 20% of the isoprene observed in Karachi. 1,2-Dichloroethane, a lead scavenger added to leaded fuel, was also emitted by cars. The photochemical production of ozone (O3) was calculated for CO and the various VOCs using the Maximum Incremental Reactivity (MIR) scale. Based on the MIR scale, the leading contributors to O3 production in Karachi are ethene, CO, propene, m-xylene and toluene.
Keywords: VOCs; Urban air quality; Vehicular emission; Tropospheric ozone; Gas chromatography;

Sea-breeze circulation influences ozone concentration differently for two types of synoptic winds across the westcentral coastal plain of Taiwan. During summer months, when the synoptic flow is southerly, a strong westerly sea-breeze confined to the lower 700–800 m produces a northeastward flow. Ozone concentration is low, with a core centered at about 100 m, leading to moderate ozone concentrations in the low population density northeastern foothills. In autumn (and spring), northerly synoptic winds of about the same strength combine with less energetic westerly sea breeze to produce a southeastward flow that carries higher ozone levels into the heavily populated Taichung basin. Ozone levels are high from 80 to 400 m, with a core up to 120 ppb from about 150 to 300 m, contributing to serious ozone episodes at the southern (downwind) end of the basin. Analyzing the backward trajectories and ozone concentration showed that the weak southeastward breeze is the dominant factor affecting the occurrence of high ozone events in the region.The horizontal distribution is based on 3 yr data obtained from a network of air-pollution monitoring sites in the study area, while the vertical data comes from two 2-day tethersonde experiments, measuring wind-speed, direction, temperature and humidity, NO, NO2, NMHC and O3, conducted during August and November 1999.
Keywords: Ozone concentration; Sea-breeze circulation; Tethersonde experiment; Ozone spatial distribution; Backward trajectory;

In this study the micro-meteorological parameters have been analyzed and the assimilative capacity of Manali is estimated on the basis of ventilation coefficient for the four seasons of the year 1998. Among the various seasons, summer has the lowest pollution potential. The industrial source complex short-term model has been used to predict the spatial distribution of three pollutants namely sulfur dioxide, oxides of nitrogen and suspended particulate matter. The model has been validated using the data measured at site. Statistical evaluation of the model indicates satisfactory performance. Using the model predictions, isopleths have been drawn. The northeastern part of Manali has been identified as vulnerable to high levels of pollution necessitating mitigation measures to be initiated in the region.
Keywords: Mixing height; Ventilation coefficient; Atmospheric stability; ISCST3 model; Pollutant concentration;

Twenty-four hour samples of air particulate matter with aerodynamic diameters from 2 to 10 μm (PM10) and <2.5 μm (PM2.5) were collected in Hanoi throughout 1 year since August 1998. The air sampler was located in a meteorological garden where routine surface observations and upper air radiosoundings were conducted. Very high PM2.5 and PM2.5−10 concentrations were observed in conjunction with the occurrence of nocturnal radiation inversions from October to December and subsidence temperature inversions (STI) from January to March. In the first case, the PM2.5−10 fraction was much enhanced and particulate pollution was significantly higher at night than in daytime. During the occurence of STIs particulate mass was almost evenly distributed among the two fractions and no significant diurnal variations in concentrations were observed. In summer (May–September) particulate pollution was much lower than in winter.The multiple regression of 24-h particulate concentrations against meteorological parameters for both the winter and summer monsoon periods shows that the most important determinants of PM2.5 are wind speed and air temperature, while rainfall and relative humidity largely control the daily variations of PM2.5−10, indicating the high abundance of soil dust in this fraction. As to turbulence parameters, among the determinants of 24-h particulate concentrations are the vertical gradients of potential temperature and wind speed recorded at 06.30 and 18.30, respectively. Meteorological parameters could explain from 60% to 74% of the day-to-day variations of particulate concentrations.
Keywords: Coarse and fine particulate matter; Temperature inversions; Meteorology; Diurnal variations; Regression analysis;

Atmospheric nitrogen and sulfur containing compounds for three sites of South Korea by Young-Min Hong; Bo-Kyoung Lee; Ki-Jun Park; Mi-Hee Kang; Young-Rim Jung; Dong-Soo Lee; Man-Goo Kim (3485-3494).
Atmospheric concentrations of gaseous HNO3, NH3 and particulates NO3 and SO4 2− were analyzed at three sites, Chunchon, Seoul and Anmyon-do, on the Korean peninsula by filter pack method. The samples were collected over a period of 24 h every Wednesday. At one of the sites, Chunchon, atmospheric SO2 was measured by using a four-stage filter pack. The annual mean concentrations of HNO3 and NH3 in 1998 ranged from 1.67 to 2.94 and from 2.00 to 3.95 μg m−3, respectively. The annual average of SO2 at Chunchon was 7.32 μg m−3. The annual averages of particulate NO3 and SO4 2− were 4.83–6.10 and 4.88–7.25 μg m−3, respectively. Particulate SO4 2− showed no distinct seasonal variation while its primary pollutant, SO2 displayed concentration peak in winter and bottomed out during summer. Consequently, the S(VI)/[S(IV)+S(VI)] ratio increased in a warm and light intensive summer and decreased in the cold and dark winter. This result suggests oxidation reactions were more efficient during the summer than in the winter. HNO3 showed a summer maximum which resulted from the temperature dependence of vapor pressure and oxidation reaction rates of its related compounds. Atmospheric NH3 was elevated in the warmer season, which related to an increase in source strength and vapor pressure. On the other hand, particulate NO3 and NH4 + showed either winter peaks or no seasonal variation. These seasonal trends in nitrogen related compounds can primarily be explained by the gas–particle conversion reaction of NH4NO3 to NH3 and HNO3. This fact is supported by an increase in the ratio of gaseous nitrogen to particulate nitrogen as the ambient temperature rose.
Keywords: Seasonal variation; Nitric acid; Ammonia; Sulfur dioxide; Particulates;

Emission rates of benzene, toluene, m-xylene, formaldehyde and acetaldehyde were measured in a fleet of 16 in-use vehicles. The test was performed on a chassis dynamometer incorporated with Bangkok Driving Cycle test mode. Three different test fuels: unleaded gasoline, gasoline blended with 10% ethanol (E10) and gasoline blended with 15% ethanol (E15) were used to determine the different compositions of exhaust emissions from various vehicles. The effects of ethanol content fuels on emissions were tested by three types of vehicles: cars with no catalytic converter installation, cars with three-way catalytic converter and cars with dual-bed catalytic converter.The test result showed wide variations in the average emission rates with different mileages, fuel types and catalytic converters (benzene: 3.33–56.48 mg/km, toluene: 8.62–124.66 mg/km, m-xylene: 2.97–51.65 mg/km, formaldehyde: 20.82–477.57 mg/km and acetaldehyde: 9.46–219.86 mg/km). There was a modest reduction in emission rate of benzene, toluene and m-xylene in cars using E10 and E15 fuels. Use of ethanol fuels, however, leads to increased formaldehyde and acetaldehyde emission rates. Our analysis revealed that alternative fuels and technologies give significant reduction in toxic VOC pollutants from automobile emission—particularly car with dual-bed catalytic converter using E10 fuel.
Keywords: Acetaldehyde; Benzene; Catalytic converter; Driving cycle; Ethanol blended fuel; Formaldehyde; Thailand; Toluene; m-Xylene;

Annual and seasonal trends in chemical composition of precipitation in Japan during 1989–1998 by Sinya Seto; Akira Nakamura; Izumi Noguchi; Tsuyoshi Ohizumi; Norio Fukuzaki; Syuji Toyama; Masahito Maeda; Kazuhiko Hayashi; Hiroshi Hara (3505-3517).
Annual and seasonal trends were discussed for precipitation chemistry in Japan on the basis of a nationwide monitoring network by Japan Environment Agency. For this analysis, 17 sites, selected from the 23 network sites after evaluation of data completeness for the present purpose, were grouped into four areas in terms of the sea which could characterize each area: the Pacific Ocean, the Japan Sea, the Seto Inland Sea and the East China Sea areas. Major ion concentrations at each site were subjected to least-squares multiple regression analysis, and discussion was principally focused on the area-groups. Each area showed significant (p<0.05) decreasing trends in non-sea-salt sulfate (nss-SO4 2−) concentrations with the annual mean change rate of −3.0% yr−1, whereas no significant trends were detected for NO3 at 59% of the sites. Ammonium (NH4 +) showed significant increasing trends for 35%, and decreasing trends for 18% of the sites; and, the maximum change rate of 3.8% yr−1 was recorded in the Pacific Ocean area. Non-sea-salt calcium (nss-Ca2+) concentrations significantly decreased in northern and some industrialized areas. Both the annual cycle-amplitudes and effects of precipitation amounts were significant for the four ions at almost all sites. The maximum concentrations of nss-SO4 2− and -Ca2+ occurred from winter to spring at most sites. The seasons when the maximum concentrations of NO3 and NH4 + occurred, were found to differ from area to area. Furthermore, the trends in precipitation nss-SO4 2−, and NO3 were qualitatively consistent with those of anthropogenic emissions of SO2, and NO x in Japan, respectively.
Keywords: Trend analysis; Acidic precipitation; Multiple regression; Sulfate; Nitrate;

The water-soluble ions in fine (PM<2.5) and coarse (PM2.5−10) atmospheric aerosols collected in Christchurch during winter 2001, spring 2000 and summer 2001, and in Auckland during winter 2001 have been studied in terms of coarse–fine and day–night differences. Although the chemical characteristics of the coarse particles were similar in both cities, those of the fine particles collected in the Christchurch winter were significantly different, as manifested by higher concentrations of nss-K+, nss-Cl, nss-Ca2+, nss-SO4 2−, NO3 and NH4 +. It was found that nighttime PM10 and nss-K+ concentrations were much higher than their daytime concentrations in the Christchurch winter but a clear day–night difference was not apparent in the Auckland winter. Moreover, in the winter, sea-salt ions did not show a day–night difference; however, nss-SO4 2− had opposite day–night variation in the two cities. An ion balance calculation has shown that in most samples, coarse particles can be neutral or alkaline, however, fine particles can be neutral or acidic. The possibility of ammonium salts existing in the fine particles collected in the Christchurch winter is discussed and it is concluded that a variety of ammonium salts were present. Equivalent ratios suggest that the fine particles may be significantly aged in the Christchurch winter.The evidence from our soluble ion study strongly suggests that wood and coal burning and secondary aerosols make a significant contribution to fine particulate mass in the Christchurch atmosphere. Thus, home-heating, a sheltered geographic location and relatively calm atmospheric condition are thought to be the major causes for the serious atmospheric particulate pollution in the Christchurch winter.
Keywords: Wood burning; Coal burning; Sea salt; Ion balance; PM10;

This paper examines the inter-suburb dispersion of particulate air pollution in Christchurch, New Zealand, during a wintertime particulate pollution episode. The dispersion is simulated using the RAMS/CALMET/CALPUFF modelling system, with data from a detailed emissions inventory of home heating, motor vehicles and industry. During the period 27 July–1 August 1995, peak 1 h and 24 h PM10 concentrations of 368 and 107 μg m−3, respectively, were observed. Peak concentrations occurred at night, when particulate emissions from wood- and coal-burning domestic heating appliances were at a maximum and emitted into a stable boundary layer. The model is generally able to reproduce the observed PM10 time series recorded at surface monitors located throughout the urban area. For this simulation, the fractional gross error ranges between 0.69 and 0.99, and the fractional bias ranges between −0.17 and 0.30. Strong horizontal concentration gradients of 100 μg m−3  km−1, both in the observational record and model predictions, are apparent. Three emission reduction options, designed to reduce the severity of particulate pollution episodes in Christchurch, are simulated. When both domestic open-hearth fires and all coal burning are removed, the 24 h average peak concentration is reduced by 55%. The number of guideline exceedences of PM10 in the modelled period is reduced from five to one. Removing open-hearth fires results in 42% reduction in PM10 concentration, resulting in three exceedences of the guideline, and removing coal-burning fires yields a 32% reduction in PM10, resulting in four exceedences of the guideline.
Keywords: PM10; RAMS; CALMET; CALPUFF; Emissions inventory;

Spread of air pollution sources and non-uniform mixing conditions in urban or regional air sheds often result in spatial variation of pollutant concentrations over different parts of the air sheds. A comprehensive understanding of this variation of concentrations is imperative for informed planning, monitoring and assessment in a range of critical areas including assessment of monitoring network efficiency or assessment of population exposure variation as a function of the location in the city. The aims of this work were to study the citywide variability of pollutants as measured by “urban background” type monitoring stations and to interpret the results in relation to the applicability of the data to population exposure assessments and the network efficiency. A comparison between ambient concentrations of NO x , ozone and PM10 was made for three stations in the Brisbane air shed network. The best correlated between the three stations were ozone concentrations followed by NO x concentration, with the worst correlations observed for PM10. With a few exceptions correlations of all pollutants between the stations were statistically significant. Marginally better were the correlations for the lower concentrations of pollutants that represent urban background, over the correlations for higher concentrations, representing peak values. Implications of these findings on application of the monitoring data to air-quality management, as well as the need for further investigations has been discussed.
Keywords: Nitrogen oxides; Ozone; PM10; Spatial distribution of pollutants; Monitoring network efficiency;

Dissolved organic carbon and organic acids in coastal New Zealand rainwater by Robert J Kieber; Barrie Peake; Joan D Willey; G.Brooks Avery (3557-3563).
Dissolved organic carbon (DOC), formate, acetate, oxalate and a variety of inorganic ions were measured in 54 rain events collected on the southern portion of the South Island of New Zealand. Concentrations of DOC ranged from a low of 10 μM to a high of 401 μM with a volume weighted average concentration of 58 μM which is in the range of concentrations measured at coastal locations in the Northern Hemisphere. The concentration of DOC varied by season with warm season rain (October–March) having somewhat higher concentrations relative to winter rain events (April–September). DOC levels in rain were also influenced by storm origin with maritime events having significantly lower levels relative to terrestrially influenced storms. Formic and acetic acids comprised a relatively small fraction of the DOC pool in New Zealand rain with volume weighted average concentrations of 1.5 μM which was not influenced by storm origin or season. There was a significant correlation between formic and acetic acid concentrations in these rain events suggesting they have similar sources or have different sources of approximately the same strength. This DOC and organic acids data will allow for a better understanding of the global tropospheric transport of carbon compounds and will aid in quantification of atmospheric carbon removal via wet deposition in the Southern Hemisphere.
Keywords: DOC; Organic acids; Rainwater composition; New Zealand;