Atmospheric Environment (v.36, #8)

Atmospheric turbidity over Kathmandu valley by Balkrishna Sapkota; Rajan Dhaubhadel (1249-1257).
The atmosphere of Kathmandu Valley has been investigated by using Sunphotometer and Nephelometer during the pre-monsoon period of 1999. The atmospheric turbidity parameters (extinction coefficient for 500 nm wavelength τ AG and Angstrom coefficient β) are found high in the morning and show decreasing trends from morning to late afternoon on average. Vertical dispersion of pollutants and increasing pollutant flushing rate by increasing wind speed from morning to late afternoon is the cause for this decreasing trend of turbidity over the valley. Being surrounded by high hills all around the valley, horizontal exit of pollutants without vertical dispersion is not possible. The scattering coefficient b scat of aerosols in ground level troposphere is also found high in the morning, which decreases and becomes minimum during afternoon. During late afternoon, b scat again shows a slightly increasing trend. The reason is the increasing vehicular emission during late afternoon rush period. The average values of Angstrom exponent α, β, τ AG and b scat are found to be 0.624±0.023, 0.299±0.009, 0.602±0.022 and 0.353±0.014 km−1, respectively. About 76.8% of the observed values of β lie above 0.2 indicating heavy particulate pollution in the valley. A comparison of observed values of turbidity parameters with other major cities of the world shows that Kathmandu is as polluted as cities like Jakarta, Kansas, Beijing, Vienna, etc.
Keywords: Atmospheric turbidity; Scattering coefficient; Extinction coefficient; Angstrom exponent; Angstrom coefficient;

Seasonal variation of carbonyl compound concentrations in urban area of Hong Kong by K.F. Ho; S.C. Lee; Peter K.K. Louie; S.C. Zou (1259-1265).
Ambient levels of carbonyls were determined at the roadside urban station of the Hong Kong Polytechnic University (HKPU) campus and it was the first systematic investigation of carbonyls at a roadside station in Hong Kong. A 12-month monitoring program for carbonyl compounds was carried out during April 1999–April 2000. Ten carbonyl compounds were quantified in this study. The most abundant carbonyl compound was formaldehyde, followed by acetaldehyde and acetone. The 24-hour average concentrations of formaldehyde and acetaldehyde were 4.13 and 2.01 μg/m3. Most carbonyls have higher average concentrations at Tsuen Wan (TW) Toxic Air Pollutants (TAPs) monitoring station during summertime due to the addition of industrial emission from the nearby industrial area. Characterization of the roadside concentrations of carbonyl compounds was compared with the long-term ambient air quality monitoring data acquired by Hong Kong Environmental Protection Department (HKEPD) under TAP Monitoring Programme. Seasonal variations and winter/summer ratios at the monitoring station are discussed. Correlations and statistical analysis of the carbonyls were performed and comparison of carbonyl compounds concentrations at roadside and TAP monitoring stations determined.
Keywords: Carbonyl compounds; Seasonal variation; Correlation; Hong Kong;

Long-term characterization of carbonaceous aerosol in Uji, Japan by Robert Höller; Susumu Tohno; Mikio Kasahara; Regina Hitzenberger (1267-1275).
Measurements of carbonaceous aerosols in eastern Asia are still scarce, and existing data are in most cases short-termed and limited to only a few places. Concentrations of organic carbon, elemental carbon (EC), and total aerosol (PM-10) were measured continuously in Uji (Kyoto prefecture), Japan in the period of June 1998 to November 1999. Carbonaceous material was measured by an Ambient Carbon Particulate Monitor (R&P, Series 5400), PM-10 was observed with a β-gauge system, and all data are available on a 1 h basis. Since the carbon monitor underestimates fine particle concentrations, we correct EC concentrations using measured EC size distributions. Additional measurements of EC size-distributions at two urban locations (Uji and Nagoya) and a site on the Pacific coast of Japan (Shirahama) were performed during spring 2000. The near-continuous long-term data and measured size-distributions allow a discussion of the background EC concentration in Japan. Our measurements show that EC contributes on average 25% of the PM-10 concentration and the annual average EC/TC ratio is about 70% at Uji. This shows that the Japanese aerosol has a high fraction of EC, which can have serious implications for climate, the hydrological cycle and human health.
Keywords: Carbonaceous aerosol; Elemental carbon; Organic carbon; PM-10; Size distribution;

Atmospheric trace gases such as oxidants, nitrogen oxides (NO X ) and non-methane hydrocarbons (NMHC) measured by the local Japanese government authorities were analyzed to elucidate the relationship between O3 and its precursors (NO X and NMHC) in metropolitan Nagoya and its coastal outskirts in Japan. Hourly data on oxidants, NO X and NMHC concentrations from 1991 to 2001 were used in order to clarify the seasonal variations, diurnal variations and photochemical potentials. Seasonal variation of O3 shows a general trend at mid-latitude in the northern hemisphere such as a maximum from late spring to summer and minimum in winter. However, coastal O3 concentrations are higher than urban ones even though the NO X and NMHC concentrations in the coastal areas are much lower than those in the urban areas.The data on NO X and NMHC concentrations are also used to describe O3 isopleth diagrams to elucidate the photochemical contributions to O3 production in these two areas. From the diagrams, O3 was found to be produced most effectively when the NO X /NMHC ratio is around 0.1 in both the urban and coastal areas. This value roughly corresponds to the numerical simulation results. Photochemical O3 production in the urban areas tends to be suppressed by the excess NO X concentrations. Photochemical O3 production in the coastal areas, on the other hand, is likely to be more active because the NO X /NMHC ratio has the most effective role in producing O3. This NO X /NMHC ratio shows a seasonal variation, which is close to the optimum ratio of O3 production from late spring to summer.
Keywords: Tropospheric O3; NO X ; Non-methane hydrocarbons; Urban air pollution; Coastal O3;

PM2.5 carbon measurements in two urban areas: Seoul and Kwangju, Korea by Seung S. Park; Young J. Kim; Kochy Fung (1287-1297).
24-h PM2.5 carbonaceous samples were collected between 27 November and 9 December 1999 in Seoul, and between 7 and 20 June 2000 in Kwangju to investigate characteristics of carbonaceous species, and the relationship between elemental carbon (EC) and Aethalometer-based black carbon (BC) measurements. 5-min PM2.5 BC and criteria air pollutant data were also measured using the Aethalometer and ambient air monitoring system. The PM2.5 samples were analyzed for EC and OC using a selective thermal manganese dioxide oxidation (TMO) method. The daily average EC and OC concentrations in Seoul were higher in the winter than in the summer (Atmos. Environ. 35 (2001a) 657). It was found that difference between ambient BC levels in the two cities was not directly proportional to the population ratio (∼8) or diesel traffic ratio (∼5.9) since particulate matter or BC concentration is strongly influenced by a result of varying traffic and meteorological conditions at the site. Using the primary OC/EC ratio approach, the results suggest that most of the measured OC in Kwangju is of primary origin during the summer. In Seoul, the observed OC includes additional secondary organic aerosol during the wintertime conditions. The relationship between the 24-h TMO-EC and Aethalometer BC measurements in PM2.5 reflected very good agreement for the two urban sites, with correlation coefficients of R 2=0.99 and 0.92, and BC/EC slopes of 0.93 and 1.07, respectively. It was found that comparing TMO-EC to BC at a different location in Korea, a different scaling factor was needed.
Keywords: TMO method; Aethalometer; Air pollutants; OC/EC method; Secondary organic aerosol;

Characterization of water-soluble species of PM10 and PM2.5 aerosols in urban area in Nanjing, China by Gehui Wang; Liming Huang; Shixiang Gao; Songting Gao; Liansheng Wang (1299-1307).
The characterization for water-soluble species of PM10 (particle matter with aerodynamical diameter <10 μm) and PM2.5 (particle matter with aerodynamical diameter <2.5 μm) in five sites of Nanjing, China was carried out during February–May 2001.The pH and conductivity K of water-soluble matters of PM10 and PM2.5 were determined, and the water-soluble fraction of the sample was followed to identify the total carbon (TC), total organic carbon (TOC), inorganic carbon (IC), elements, NO3 , SO4 2− and NH3-N.The experimental results show that water-soluble matters of PM10 and PM2.5 in Nanjing are acidic, and the pH of PM2.5 is lower than PM10. Conductivity of water-soluble species of PM10 and PM2.5 aerosols varied over a wide range from 1087 to 225 μs/cm. Conductivity between PM10 and PM2.5 has a linear correlationship, and the equation is Y=0.8459X+44.74, r 2=0.9376 (Y: conductivity of PM2.5, X: conductivity of PM10). TOC make up the majority of TC and accounts for 3.17–14.13% of PM10 and/or PM2.5 loadings, while IC only accounts for 0.12–0.47% of PM10 and/or PM2.5 mass. Al, As, Ba, Ca, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, Pb, Ti, V and Zn, 17 elements were detected in water-soluble matters of PM10 and/or PM2.5. Ca, K and Na are the most abundant chemical components, which account for more than 95% of total water-soluble elements (TWSE). Of all the five sites, TWSE accounts for 1.80–6.13% of the particle mass and 61.28–72.73% of TWSE of PM10 is enriched in fine particles (<2.5 μm in diameter). Nitrate (NO3 ), sulfate (SO4 2−), ammonia and ammonium (NH3-N) were determined. The highest level of nitrate was 15.49 μg/m3 for PM10 and 12.66 μg/m3 for PM2.5 at site FZ. As was the case for nitrate, the highest level of sulfate was also presented at the same site, which was 28.22 μg/m3 for PM10 and 21.48 μg/m3 for PM2.5. However, a higher level of ammonia and ammonium was presented at site ZS, which was 36.05 μg/m3 for PM10 and 22.06 μg/m3 for PM2.5.
Keywords: PM10 and PM2.5 aerosols; Water-soluble matters; pH; Conductivity; TOC; IC; Elements and ions;

Anthropogenic emissions of non-methane volatile organic compounds in China by Zbigniew Klimont; David G. Streets; Shalini Gupta; Janusz Cofala; Fu Lixin; Yoichi Ichikawa (1309-1322).
Inventories of emissions of non-methane volatile organic compounds (NMVOC) in China are reported for the years 1990, 1995, 2000, 2010, and 2020. For 1990 and 1995, historical activity data were assembled for more than 70 processes that lead to the release of NMVOC. Appropriate emission factors were developed, based on Western, Asian and Chinese experience. It is estimated that emissions were 11.1 Tg in 1990 and 13.1 Tg in 1995, principally from the combustion of biofuels and coal in small combustors. All emissions are presented at provincial level. Using appropriate growth factors derived from anticipated economic, population, and lifestyle changes, and factoring in regulatory changes and technology improvements, we estimate that emissions could grow to 15.6 Tg in 2000, 17.2 Tg in 2010, and 18.2 Tg in 2020. Though activity growth rates are much higher than these increases would imply, technology improvements mediate the increases. Emissions from solvent use, paint use, and transport become increasingly important as time goes on. The sectoral distribution and per capita level of China's emissions are compared with those of other countries. Finally, gridded NMVOC emission fields are presented at 1°×1° resolution, and speciation of the emissions into 16 chemical types is reported.
Keywords: Air pollution; Non-methane volatile organic compounds (NMVOC); Emission inventory; Emission scenarios; China provinces;

We report on the construction of the aerosol nitrate concentration field in Europe from an interpolation of data. The first step was an active search for and a subsequent quality assessment of the (long term) data for this semi-volatile component, which is subject to a range of artefacts during sampling. Therefore first an overview of (filter) sampling methods in use in Europe and the associated sampling artefacts are presented. Denuder filter pack combinations have very minor artefacts and data obtained with this technique are therefore used as the starting point. Because of the paucity of data from these devices, values obtained with simple filter sampling were also considered after a critical analysis. We found that the largest artefact associated with inert filters (IF) (Teflon and Quartz) is evaporation of ammonium nitrate. Hence, concentrations obtained with the use of IF are lower values. Next, data from “total nitrate” filters were evaluated. Such filters collect both aerosol nitrate and nitric acid gas and the contribution of the gaseous compound was corrected for. The distances over which nitrate concentrations correlate was then analysed and it was found that in the winter half-year the correlation length was sufficiently long to warrant interpolation of the point data. The nitrate concentration field as obtained from interpolation of nitrate data in the period 1994–1997 was validated with intermediate point data from shorter lasting campaigns. The field has a large area of high nitrate concentrations ranging from southern England over continental western Europe into Poland, with concentrations of nitrate exceeding 5 μg m−3. Strong arguments are provided that the nitrate is predominantly present in the fine aerosol fraction (PM2.5). To the north nitrate concentrations range from 2.5 μg m−3 in southern Sweden to <0.5 μg m−3 in mid-Scandinavia. To the east and west of the central European maximum the nitrate concentration trails off in a more gradual way. It was inferred that the concentration of nitrate in winter in Europe north of the Alps, with the exception of France from which country no data could be found, is 60% or more of that of sulphate. It should further be mentioned that in the Po-Valley ammonium nitrate levels are as high as those in western Europe.
Keywords: Nitrate field; Sampling artefacts; Critical evaluation;

Formaldehyde (HCHO) concentrations have been measured in 66 rain samples during the rainy season (September 1999–May 2000) at Heraklion (25°07′E, 35°20′N; Crete) a coastal urban location in the eastern Mediterranean. HCHO concentrations vary between 0.42 and 11.14 μM, in the range of HCHO levels reported at other locations worldwide. The annual volume-weighted mean (VWM) rainwater HCHO concentration is 3.05 μM and comprised ∼3% of the dissolved organic carbon. Formaldehyde levels in rainwater depend on the air mass origin. The per event deposition of HCHO when air masses originate from NW Europe, Balkans or Turkey is 2–4 times higher than that from Africa or from marine sectors indicating strong influence from anthropogenic sources. The significant correlation of formaldehyde with non-sea-salt sulfate, nitrate and ammonium also indicates a significant anthropogenic component in HCHO levels. Formaldehyde is found to correlate significantly with formate and acetate with a ratio of formate to formaldehyde close to 1. According to our measurements rainwater HCHO and TOC could significantly contribute to the productivity of the eastern Mediterranean seawater. In particular, the rainwater can be an important supplier of the HCHO reservoir in the seawater. In addition the rainwater TOC levels can provide to phytoplankton species up to 32% of the organic carbon needed for new production.
Keywords: Formaldehyde; Rainwater; Organic carbon; Formate; Non-sea-salt sulfate; Eastern Mediterranean; Productivity of seawater;

Regional transport of pollutants over the Bay of Biscay: analysis of an ozone episode under a blocking anticyclone in west-central Europe by Gotzon Gangoiti; Lucio Alonso; Marino Navazo; Amaia Albizuri; Gorka Perez-Landa; Monica Matabuena; Veronica Valdenebro; Mercedes Maruri; José Antonio Garcı́a; Millán M. Millán (1349-1361).
This paper analyses an ozone episode recorded at the regional monitoring network of the Basque Country, located in northern Iberia. The synoptic weather pattern was characterized by the presence of a blocking anticyclone over the British Isles and its subsequent evolution eastwards. The blocking situation lasted for 4 days, and ozone concentrations throughout the whole network rose up to 100–160 μg m−3. The main objective is to investigate the origin of the polluted air masses in the area and search for the transport/dispersion mechanisms that gave rise to such a severe O3 episode. A mesoscale model, operating with three nested grids down to a resolution of 3 km×3 km, was used to simulate the mesoscale processes. The model results were validated against the output of a wind profiler radar and the meteorological data recorded at the surface meteorological stations operated by the local and regional authorities. Both the single-particle Lagrangian back-trajectories and the results of a multiple-particle dispersion model suggest that during the peak pollution episode there were contributions from local sources as well as regional and long-range transport from foreign sources. The transport mechanisms depend on the position-evolution of the high-pressure system over Europe: during the last phase of the episode (15–16 June 1996), concurrent with the highest concentrations, we detected both a contribution of pollutants from southern France, which arrived at the Bay of Biscay with the north-easterly winds forced by the European anticyclone, as well as a contribution from night-time discharges of aged pollutants located in the residual layer over the Ebro valley. This layer accumulates pollutants from local sources located inside the Ebro valley (daytime convection and mixing during the previous day) and can also be a reservoir of pollutants transported from the western Mediterranean following the sea breeze regime.
Keywords: Ozone; Dispersion; Modelling; Mesoscale; Air quality network; Wind profiler radar;

The origin of high particulate concentrations over the United Kingdom, March 2000 by D.B Ryall; R.G Derwent; A.J Manning; A.L Redington; J Corden; W Millington; P.G Simmonds; S O’Doherty; N Carslaw; G.W Fuller (1363-1378).
An episode of exceptionally high PM10 and PM2.5 levels was observed during the night of the 2–3 March 2000 throughout England and Wales. The weather was characterised by strong westerly winds and widespread rainfall associated with a low pressure system to the north of Scotland, conditions usually associated with relatively clean, unpolluted air. Possible sources included volcanic ash from an eruption on 26 February 2000 in Iceland, or dust from large sandstorms over the Sahara. A combination of atmospheric transport modelling using the Lagrangian dispersion model NAME, an analyses of satellite imagery and observational data from Mace Head has shown that the most likely origin of the episode was long range transport of dust from the Sahara region of North Africa. Further modelling studies have revealed a number of previously unidentified dust episodes, and indicate that transport of dust from the Sahara can occur several times a year. Dust episodes are of interest for a number of reasons, particulate levels can be elevated over a wide area and in some instances can significantly exceeded current air quality standards. If a natural source is identified over which there can be no control, there are implications for the setting of air quality standards.
Keywords: Saharan dust; PM10; PM2.5; Long range transport; Air quality standards;

The chemical composition of pollutant species in precipitation sampled daily or weekly at 10 sites in Ireland for the five-year period, 1994–1998, is presented. Sea salts accounted for 81% of the total ionic concentration. Approximately 50% of the SO4 2− in precipitation was from sea-salt sources. The proportion of sea salts in precipitation decreased sharply eastwards. In contrast, the concentration of NO3 and the proportion of non-sea-salt SO4 2− increased eastwards reflecting the closer proximity to major emission sources. The mean (molc) ratio of SO4 2−:NO3 was 1.6 for all sites, indicating that SO4 2− was the major acid anion.The spatial correlation between SO4 2−, NO3 and NH4 + concentrations in precipitation was statistically significant. The regional trend in NO3 concentration was best described by linear regression against easting. SO4 2− concentration followed a similar pattern. However, the regression was improved by inclusion of elevation. Inclusion of northing in the regression did not significantly improve any of the relationships except for NH4 +, indicating a significant increase in concentrations from northwest to southeast.The spatial distribution of deposition fluxes showed similar gradients increasing from west and southwest to east and northeast. However, the pattern of deposition shows the influence of precipitation volume in determining the overall input. Mean depositions of sulphur and nitrogen in precipitation were ≈30 ktonnes S yr−1 and 48 ktonnes N yr−1 over the five-year period, 1994–1998, for Ireland.Least-squares linear regression analysis indicated a slight decreasing trend in precipitation concentrations for SO4 2− (20%), NO3 (13%) and H+ (24%) and a slight increasing trend for NH4 + (15%), over the period 1991–1998.
Keywords: Acid deposition; Sulphate; Nitrate; Ammonium;

A four and a half year study of ozone concentrations in the Central Mediterranean was carried out between January 1997 and August 2001 on a background monitoring station located on the island of Gozo midway between Southern Europe and North Africa.Seasonal and diurnal variations of background ozone are documented. They show the existence of seasonal cycles with a primary maximum in spring followed by a secondary, more variable maximum in summer which indicates that photochemically produced ozone is being transported over the Mediterranean to the rural island of Gozo. Although peak ozone concentrations seldom exceeded 100 ppbv during summer, the background ozone-mixing ratios (as monthly averages) are some of the highest values which can be found at low latitude sites throughout the world. An increasing trend in the annual background ozone concentration from 48.2 ppbv in 1997 to 52.2 ppbv in 2000 is observed. During wintertime the average ozone mixing-ratio (as monthly averages) of 44 ppbv in December is approximately twice as high as on the European continent. This may imply that on Malta, due to higher average ozone concentrations between autumn and spring (the main growing season), crop damage of high economic value may occur.
Keywords: Ozone; Malta; Island of Gozo; Mediterranean;

The paper considers selected persistent organic pollutants (POPs) atmospheric emission evaluation on the territory of Belarus for main source categories. The procedure applied was based on the UNECE EMEP methodology. Data of industrial statistics, production processes analysis and relevant emission factors were used. For a number of sources, only quality and semi-quality emission evaluation was conducted, due to the lack of information for the selection of emission factors or statistical data relevant.In the paper, emissions of the following groups of pollutants are discussed: dioxins/furans (PCDD/PCDF) and polychlorinated biphenyls (PCB) as requested for EMEP database (Protocol on Persistent Organic Pollutants to the convention of 1979 on Long-range Transboundary Air Pollution in Europe and Annexes I, II, or III to the Protocol, 1998). PAH emission and selected chlorinated pesticides input also requested by EMEP will be described in other issues.Estimations have showed that Belarus as a whole is not a large emission source of such POPs as dioxins. Its share in European emissions is significantly below 1%. This can be explained by the fact that in Belarus there are no such large dioxin emission sources like sintering, waste incineration, non-ferrous industry. But some important sources of dioxins/furans for instance, open burning are not included in quantitative estimation now.The main contribution to dioxin emissions is by firewood and peat combustion. Only electric steel smelting plant can be considered as a large emission point source.Leakage from transformers and damaged capacitors was estimated as the main source of polychlorinated biphenyls (PCB) discharged into the environment: dielectric fluids with PCB are still in use in electrical equipment.
Keywords: Emission; Inventory; Persistent organic pollutants; Dioxins/furans; Polychlorinated biphenyls;

Lead isotope tracking of atmospheric response to post-industrial conditions in Yerevan, Armenia by Robert Kurkjian; Charles Dunlap; A.Russell Flegal (1421-1429).
Temporal gradients in environmental lead concentrations and isotopic compositions trace the rapidly shifting transition from high to low industrial emissions in Yerevan, Armenia following the dissolution of the Soviet Union in the early 1990s. Shortly after the breakup, in 1995 and 1996, atmospheric lead concentrations averaged ∼0.4 μg m−3 and the combustion of leaded gasoline was the primary source of industrial lead emissions in Yerevan. But by 1998, unleaded gasoline was predominant and atmospheric lead concentrations had decreased by two orders of magnitude to ⩽0.003 μg m−3 because industrial lead emissions from stationary sources had also been radically curtailed. The increased proportion of unleaded gasoline use is clearly seen in comparisons of the isotopic compositions of lead in air and gasoline. In 1998 and 1999, the isotopic composition of atmospheric lead (1.1605⩽206Pb/207Pb⩽1.1641) was comparable to that in soil (1.1357⩽206Pb/207Pb⩽1.1649); and it was markedly different from the average isotopic value of gasoline (206Pb/207Pb=1.1407 in 1998 and 1.1555 in 1999). Binary mixing calculations suggest that 75% of the atmospheric lead in 1998 was derived from re-suspended soil that retains lead from past emissions and 25% was derived from a mixture of present industrial emissions and uncontaminated soil. Anthropogenic lead persists in urban air, albeit at relatively low levels, despite leaded gasoline phase out and stationary emissions curtailment.
Keywords: Lead isotopes; Air sampling; Soil contamination; Leaded gasoline; Armenia;