Atmospheric Environment (v.37, #27)

Localization of source and sink regions of carbon dioxide through the method of the synoptic air trajectory statistics by F. Apadula; A. Gotti; A. Pigini; A. Longhetto; F. Rocchetti; C. Cassardo; S. Ferrarese; R. Forza (3757-3770).
The main purpose of this paper is to contribute to the improvement of the present knowledge concerning the transient components of the global carbon cycle, superimposed to the periodic seasonal oscillation and to the yearly trend. This purpose has been achieved through the comparison among the calculated concentration fields of atmospheric CO2 and its comparison with the sea-surface temperature patterns, forestation maps, forest fires, and the anthropogenic emissions extracted from Edgar V.2.0 database. In order to identify with high spatial resolution the most relevant areas of CO2 sources and sinks, we have applied a methodology based on a statistical analysis of simulated back-trajectories related to atmospheric concentration values measured at some receptor sites where the back-trajectories originate.In particular, we have used a 2-year time series (1996 and 1997) of CO2 concentration data observed in three receptor sites located in high mountain areas, in order to reduce significantly the effects due to local influences (such as emissions from industries and urban areas or the absorption processes due to the vegetation). The back-trajectories were computed by means of the wind fields provided by the ECMWF analysis (T213/L31 model) on a regular grid. The area investigated was from 11°W to 36°E in longitude and from 30°N to 57°N in latitude. The final concentration field was computed by means of a statistical source–receptor model, based on a methodology developed by Stohl (Atmos. Environ. 30 (1996) 579) and adapted here with some modifications in the pre- and post-processing phases.Before applying the model, a careful evaluation of its sensitivity to the input data has been performed, followed by an analysis to identify the optimal configuration of the model.The results have shown a satisfactory accuracy in the identification of the major sources and sinks considered.
Keywords: Long-range transport; Backward trajectories; Carbon dioxide; Seasonal cycle; Source-oriented relationship;

A biogenic volatile organic compounds emission inventory for Beijing by Wang Zhihui; Bai Yuhua; Zhang Shuyu (3771-3782).
The present study presents us the first detailed inventory for volatile organic compounds (VOC) emissions from vegetation over Beijing, China. The spatially and temporally resolved inventory was developed based on a Geographic Information system (GIS), Remote sensing (RS) data and field measurement data, such as digitized land-use data, normalized difference vegetation index (NDVI) and temperature and photosynthetic active radiation (PAR) data from direct real-time measurement. The inventory has a spatial resolution of 1×1  km 2 and a time resolution of 1  h . Urban, agriculture, and natural land-use distributions in Beijing were combined with biomass factors for each land-use category to produce a spatially resolved biomass inventory. A biogenic emission inventory was developed by combining the biomass inventory with hourly emission rates for tree, shrub, and ground cover species of the study area. Twenty-three kinds of the emission rate data of the 39 vegetation types in Beijing were identified using a bag-enclosure sampling method followed by GC-FID analysis in our field measurement. Other emission rate data were quoted from previous study or assigned with the taxonomic method. Correcting for environmental factors, including light intensity and temperature, we arrive a value of 1.6×1010   g C for total annual biogenic VOC emissions from Beijing, including 7.9×109   g C for isoprene, 3.5×109   g C for monoterpenes, and 4.8×109   g C for OVOC. Some uncertainties are also discussed in this study.
Keywords: Biogenic VOC; Isoprene; Monoterpene; Emissions inventory; Beijing;

Estimation of the average molecular weight of humic-like substances isolated from fine atmospheric aerosol by Gyula Kiss; Etelka Tombácz; Bálint Varga; Tomas Alsberg; Linn Persson (3783-3794).
Rural fine aerosol collected in Hungary was analysed with different techniques to estimate the average molecular weight (AMW) of humic-like substances (HULIS). First, ultrafiltration was applied to the total water-soluble organic fraction. Virtually all the water-soluble organic matter passed through the ultrafiltration membrane having a 500 Da nominal molecular weight (MW) cut-off. Then a significant portion (more than half) of the water-soluble organic matter was isolated in pure form and further analysed by liquid chromatography coupled to mass spectrometry. These analyses confirmed that the isolated organic matter was mostly composed of HULIS, which had been suggested on the basis of elemental analysis and different spectroscopic studies earlier. Furthermore, mass spectrometry indicated that the AMW of these substances could be expected in the 200–300 Da range. As detailed in the paper, this estimate may be negatively biased to some extent as a consequence of unwanted processes in the mass spectrometer. In order to reduce uncertainties in the MW estimates another independent technique—vapour pressure osmometry—was also applied and resulted in number AMW estimates in the range of 215–345 Da.
Keywords: Organic aerosol; Water-soluble organic compounds; Mass spectrometry; Vapour pressure osmometry; Ultrafiltration;

Nitrogen oxides and carbon monoxide concentration were measured inside and outside of a light-goods-vehicle at different locations and driving conditions for a 6-month period. To investigate the exposure of the vehicle passenger to the specified outdoor pollutant, the indoor–outdoor air quality (IO) relationships under various driving conditions, namely traffic density, ventilation modes and type of roadway were studied. Four main types of driving environments were selected: highway, countryside, urban street and tunnel. The vehicle was driven under the three main types of ventilation conditions: air-conditioning with air-recirculation, air-conditioning with fresh air intake and natural ventilation.It is found that the IO ratio is not specific only to the mode of ventilation but also depends on the driving environment. The IO value can vary drastically even using the same ventilation mode when the vehicle is travelling in a different environment. It is found that using fresh-air ventilation mode, the IO can change from approximately 0.5–3 as it commutes from a highway to the countryside. The results also indicate that indoor NO level increased as the traffic density increases. The fluctuation of indoor NO level of naturally ventilated vehicle followed the variation of outdoor NO concentration with the IO value varying from 0.5 to 5. The results also show that even in an air-conditioned van, the indoor NO and CO concentration is significantly affected by that outdoor. It suggests the use of different ventilation mode when commuting in different environment.
Keywords: Indoor–outdoor air quality relationship; Vehicles; Air-conditioning; Nitrogen oxides; Carbon monoxide;

The exposure of bus commuters to carbon monoxide (CO) and carbon dioxide (CO2) in various bus routes in Hong Kong has been studied. The buses under investigation travel in the city of Hong Kong and involve both air-conditioned and older buses without air-conditioning. The in- and out-vehicle concentrations of both pollutants were measured simultaneously using portable samplers. It is found that the exposure level of CO2 inside the air-conditioned vehicle is strongly dependent on the number of passengers but not on the driving environment. During the measurement, it is found that the CO2 level can reach up to a dangerous 10 times that out-vehicle when the air-conditioned bus is full. On the other hand, it was found that the CO and CO2 levels for a non-air-conditioned bus remain low due to better air exchange between in- and out-vehicle.
Keywords: Indoor–outdoor relationships; Commuting; Exposure; Carbon monoxide; Carbon dioxide;

Exhaust emissions from ships at berth by D.A. Cooper (3817-3830).
Emission measurements have been carried out on board six ships at berth during normal real-world operation (hotelling, unloading and loading activities). The study included three passenger ferries, one transoceanic container/ro-ro, one transoceanic car/truck carrier, and one chemical tanker. Emissions were measured from 22 auxiliary engines (AEs, medium and high-speed marine diesels) covering seven engine models and ranging in size from 720 to 2675  kW maximum output. The fuels varied from low sulphur gasoils (2.91  cst viscosity) through to residual oils (411  cst viscosity). Both specific emission factors (g kWh −1) at a given engine load and total emissions (kg) of nitrogen oxides (NO x ), sulphur dioxide, carbon monoxide, hydrocarbons, carbon dioxide, particulate matter (PM) and polyaromatic hydrocarbons during actual harbour stops were determined. In addition, some preliminary measurements to investigate PM size distributions were undertaken.The specific emissions showed significant variations between the different engine models and also within the same engine model on board the same ship. For example NO x emissions varied between 9.6 and 20.2  g kWh corr −1 between all engines and 14.2–18.6  g kWh corr −1 between engines of the same model and fuel. Other emissions from boiler use and possible main engine warm-up prior to departure were in general expected to be considerably less than those from the AEs. The results obtained for the three passenger ferries demonstrate that empirically derived, emission formulae using dead weight tonnage can prove to be a cost-effective and accurate tool for harbour emission inventories.
Keywords: Ship emissions; Diesel exhaust; Auxiliary engine; Harbour;

Polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) concentrations were measured every other week from July 1999 to February 2000 in the rural air of Ansung, Kyonggi-do in South Korea.The average contribution of PCB homologs were tri-(44.5%), tetra-(23.6%), penta-(21.6%), hexa-(3.6%), hepta-(5.5%) and deca-CB (1.6%) therefore identifying tri-CBs as the main component of PCB homologs. Endosulfan is the most prevalent OCP because of its continuous usage as a pesticide in South Korea.The correlation coefficient between OCPs and temperature was significantly high (p<0.05) which is partly due to the fact that major sources are re-volatilization from soil, vegetation and so on.The Clausius–Clapeyron equation was applied to atmospheric total PCBs and OCPs (α-HCH and γ-HCH), relating partial pressure (ln  P) to inverse temperature (1/T). The partial pressure of total PCBs and OCPs were all significantly correlated with inverse temperature (p<0.01) and the slopes of resulting plots of total PCBs and OCPs ranged from −2950 (total PCBs) to −6629 (α-HCH), −8106 (γ-HCH). The strong temperature effect and steep slopes of OCPs indicate the predominant impact of local surroundings to these concentrations in the rural atmosphere.
Keywords: PCBs; OCPs; Gas/particle phase partition; Clausius–Clapeyron equation; Temperature effect;

Diverging long-term trends in ambient urban particle mass and number concentrations associated with emission changes caused by the German unification by Wolfgang G Kreyling; Thomas Tuch; Annette Peters; Mike Pitz; Joachim Heinrich; Matthias Stölzel; Josef Cyrys; Joachim Heyder; H.Erich Wichmann (3841-3848).
Air quality in urban areas has considerably changed over time. Recent changes of particle emissions in Eastern Germany during the last 10 years provide a quick motion picture of a development which lasted several decades in Western countries. Size distributions of fine particles (<2.5 μm aerodynamic diameter) were measured during winters 1991/1992 through 2000/2001. Within these 10 years particle size distributions shifted strongly towards smaller sizes. This was mainly due to a twofold increase of the number concentration of 0.01–0.03 μm sized particles. In parallel, fine particle mass concentration decreased by 75%.Since the mass concentration of fine particles is considered most relevant for human health today, the observed substantially decreasing trend in Eastern Germany is a desirable development. It is, however, accompanied by an increase of the number concentration of ultrafine particles in the 0.01–0.03 μm size range for which most recently associations with health effects have been found. This development associated with rapid emission changes caused by the German unification may be considered as a time-lapsed development representing partially unrecorded temporal alterations of emissions in a large entity of Western industrialized urban environments over the last five decades. Thus, the worldwide policy to reduce only the mass concentration of ambient aerosols without controlling for the number concentration may not be sufficient to assess health effects associated with urban particles.
Keywords: Airborne particulate matter; Ambient urban aerosol; Germany; Particle concentration: number, mass, fine particles, ultrafine particles, winter trends;

Formaldehyde record from Lys glacier firn core, Monte Rosa massif (Italy) by O. Largiuni; R. Udisti; S. Becagli; R. Traversi; V. Maggi; E. Bolzacchini; P. Casati; C. Uglietti; S. Borghi (3849-3860).
Formaldehyde content within the first 16 m of Lys Glacier firn core (Monte Rosa massif, Italy) was determined by a sensitive spectrofluorimetric method in flow injection analysis.The formaldehyde concentration range of all analysed samples was 3.8–24.8 μg l−1, with 11.1 μg l−1 mean concentration and 10.7 μg l−1 median concentration. These values were found to be in agreement with other measurements carried out in high- and mid-latitude glaciers.Due to the exceptionally high annual snow accumulation rate at Lys Glacier sampling site (3.79 m w.e.), most formaldehyde is preserved, at least for the earlier metres of deposition.The general agreement between the formaldehyde profile and other parameters typically used as seasonal markers suggested a similar seasonal behaviour for formaldehyde in high snow accumulation alpine sites.
Keywords: Formaldehyde; Flow analysis; Snow; European glaciers; Alps;

Measurement of hydroperoxides and ozone in Oku-Nikko area by Akinori Takami; Nami Shiratori; Hiroto Yonekura; Shiro Hatakeyama (3861-3872).
Hydroperoxides were measured at the Oku-Nikko observation station, which is situated at the foot of mountains where severe forest decline was observed. Hydrogen peroxides (H2O2) showed a diurnal variation with the maximum mixing ratio of 1.6 ppbv. The concentration of H2O2 was high in the daytime and low at night. The diurnal variation is caused by photochemical processes. Methylhydroperoxide (CH3OOH, MHP) was observed with an average mixing ratio of 0.1 ppbv. A strong correlation was observed between H2O2 and O3. High concentrations of H2O2 and O3 were observed in the late afternoon, which is considered to be due to the transport of polluted air masses from urban areas. The total amount of H2O2 to which the forest around the observation station was exposed was estimated to be 275 ppbv h between 18 July and 14 August, 2000.
Keywords: Hydrogen peroxide; Methylhydroperoxide; HPLC; Forest decline; Long-range transport;

Evaluation and improvement of ammonia emissions inventories by William Battye; Viney P Aneja; Paul A Roelle (3873-3883).
Two case studies are performed to improve ammonia emissions inputs used to model fine particulate matter (PM2.5 is the portion of particulate matter smaller than 2.5 μm aerodynamic diameter) formation of ammonium sulfate and ammonium nitrate. Ammonia emissions are analyzed in detail for North Carolina and the San Joaquin Valley (SJV) of California, with a focus on the Charlotte, NC, and Fresno, California metropolitan areas. A new gridded ammonia emissions inventories suitable for atmospheric modeling for the two case study cities was also developed.Agricultural sources accounted for the bulk of ammonia emissions in both case studies. Livestock waste contributed about 80% in North Carolina and 64% in the SJV, while fertilizer application contributed about 6–7% in both domains. Forests and non-agricultural vegetation contributed 5% in North Carolina and 12% in the SJV. Motor vehicles accounted for about 6% of ammonia emissions in North Carolina and 14% in the SJV. In the Charlotte and Fresno urban areas, the distribution of emissions is less heavily weighted toward agricultural sources and more heavily weighted toward highway vehicles (highway vehicles account for an estimated 64% of emissions in Charlotte and 51% of emissions in Fresno). The emissions estimates for agricultural sources (livestock and fertilizer application) decline to approximately 14% in the winter for both the Charlotte and Fresno urban areas. Emissions estimates for soils and vegetation also decline to approximately 0 during the winter for both the Fresno and Charlotte area. As a result, motor vehicles account for a larger fraction (approximately 73% and 70% for Charlotte and Fresno, respectively) of winter ammonia emissions, particularly in the Charlotte urban area.
Keywords: Ammonia; Emissions; Inventory; Agriculture; Particulate matter;

Short-range vertical dispersion from a ground level source in a turbulent boundary layer by R.E. Britter; S.R. Hanna; G.A. Briggs; A. Robins (3885-3894).
The short-range vertical dispersion of a passive containment in a neutrally stratified turbulent boundary layer can be usefully characterised by a number of approaches, such as a vertical diffusivity, K z , a vertical Gaussian dispersion parameter, σ z , and an entrainment velocity, w e . σ z and w e are approximately related by w e∝dσ z /dt. While the Gaussian model is widely used in most air quality applications, the entrainment velocity is widely used in wind tunnel studies and models for the dispersion of hazardous gases. This paper summarises experiments in three simulated rough-wall atmospheric boundary layers (two in the US and one in the UK), which lead to the conclusion that for passive releases the entrainment coefficient α in the formula w e =αu∗ is α=0.65±0.05. This value is consistent with a recent analysis of the Prairie Grass data (out to x=100 m, where vertical profiles were obtained) that gave α=0.63±0.05. Somewhat surprisingly we were not able to locate a theoretical analysis that could reproduce these results without recourse to some empirical input.
Keywords: Pollutant dispersion; Vertical entrainment; Vertical dispersion;