Atmospheric Environment (v.34, #3)

Editorial (351).

Behaviors of volatile inorganic components in urban aerosols by Hiromasa Ueda; Taroh Takemoto; Young Pyo Kim; Weiming Sha (353-361).
A multicomponent gas–aerosol equilibrium model (Kim et al., 1993a,b; Kim and Seinfeld, 1995) was used to explain the behaviors of water content and other volatile species in the aerosols observed in polluted air mass in Central Japan. It was found that gas–aerosol equilibrium was attained after long-range transport of polluted air mass (e.g., 50 km) from emission source area, while it was not completed in large emission source areas. The present model predicted with high accuracy the gas–aerosol equilibrium of ammonium, nitrate and chloride at remote sites. The correlation coefficient was R=0.98 for ammonia and more than R=0.86 for gaseous nitric acid. It was R=0.94 for gaseous hydrochloric acid, which meant significant chlorine deficit under high-temperature and low humidity conditions was also predicted accurately. The predicted water content was consistent with that calculated by the semi-theoretical Winkler's formula (Aerosol Sceince, 13, 1973, 373–387). At RH=90% the water content attained almost the same weight as that of dry aerosol, while at about RH=60% it was less than 10%. In contrast, temperature dependency of the water content was weak except for very high air temperature conditions in summer. Finally, it emphasized the superiority of the multicomponent approach for gas–aerosol equilibrium, compared with the binary-component approach.
Keywords: Aerosol; Equilibrium; Nitrate; Sulfate; Chlorine deficit;

Present and future emissions of air pollutants in China: by D.G Streets; S.T Waldhoff (363-374).
As part of the CHINA-MAP program, sponsored by the US National Aeronautics and Space Administration, regional inventories of air pollutants emitted in China are being characterized, in order that the atmospheric chemistry over China can be more fully understood and the resulting ambient concentrations in Chinese cities and the deposition levels to Chinese ecosystems be determined with better confidence. This paper presents estimates of emissions of three of the major air pollutants in China: sulfur dioxide (SO2), nitrogen oxides (NO x ), and carbon monoxide (CO). Emissions are estimated for each of the 29 regions of China covered by the RAINS-ASIA simulation model, including Hong Kong and Taiwan. All sectors of the Chinese economy are considered, including the combustion of biofuels in rural homes. Data for 1990 and 1995 are presented, as well as two projections for the year 2020 under alternative assumptions about levels of environmental control. Sulfur dioxide emissions are projected to increase from 25.2 mt in 1995 to 30.6 mt in 2020, provided emission controls are implemented on major power plants; if this does not happen, emissions could increase to as much as 60.7 mt by 2020. Emissions of nitrogen oxides are projected to increase from 12.0 mt in 1995 to somewhere in the range of 26.6–29.7 mt by 2020, with little in the way of pollution controls or other emission reduction measures in place. Emissions of carbon monoxide are projected to decline from 115 mt in 1995 to 96.8 mt in 2020, due to more efficient combustion techniques, especially in the transportation sector; if these measures are not realized, carbon monoxide emissions could increase to 130 mt by 2020. Emissions of all three species are concentrated in the populated and industrialized areas of China: the Northeastern Plain, the East Central and Southeastern provinces, and the Sichuan Basin.
Keywords: Sulfur dioxide; Nitrogen oxides; Carbon monoxide; Emissions; China;

This paper examines the nature and extent of uncertainties associated with spatially resolved emission estimates with particular reference to an examination of alternative emissions data. Evidence is taken from recent research into the development of generic methodologies for the estimation of emissions of key urban pollutants from anthropogenic sources in the North West region of England. The inventory results, which are available in terms of a regional 5×5 km grid, a sub-regional 1×1 km grid and at the scale of the original activity data, are useful for a number of air quality management tasks. However, the requirements of producing a generic methodology which uses readily available data sources has been found to limit the degree of detail with which it is possible to develop estimation procedures and this has implications for the level of confidence associated with the results and their further application. One of the principal limitations is the availability of equivalent activity data for a number of administrative units. A further assessment of the results of the North West inventory has been made through a comparative study of the inventory data with other emissions data covering a sub-set of the study area. These investigations indicate that there are a number of variations between inventory results in terms of overall emission magnitudes and their spatial distribution. Observed differences between the estimates are attributable to different sources of activity data and emission factors and also as a result of the geographical data used to represent sources.
Keywords: Emissions inventory; Spatial emissions; Verification methods; UK;

A three-dimensional (1° latitude×1° longitude×1 km altitude) inventory of aircraft NO x emissions over China for a calendar year of 1997–1998 has been developed using the detailed schedule database of the Civil Aviation Administration of China (CAAC). The fuel burned and emissions are calculated according to fuel burn rates and NO x emission indices of different airplane types along each flight path. The calculated total fuel burned and NO x emissions are 9.557×106 kg day−1 and 1.220×105  kg day−1, respectively. Nearly 78% of these emissions occur at an altitude band of 9–12 km. The high emission rates are found in the regions of Beijing, Guangzhou and Shanghai as well as the corridors connecting these three cities. The highest NO x emission rate in these regions can be 3.7×103  kg day−1 in a column-integrated grid. The seasonal dependence as well as diurnal circle of NO x emission rates is presented. The time resolution of the inventory is as high as 1 h.
Keywords: NO x emissions; Aircraft; Regional inventory; China;

This paper describes the use of urban emission inventory data and an urban scale dispersion model (ADMS-Urban) to calculate concentrations of NO x and NO2 in London. The dispersion model used in this study is a second generation Gaussian dispersion model which is characterised by the use of boundary layer similarity profiles to parameterise the variation of turbulence with height within the boundary layer. The model has an integral chemistry model which is used to predict concentrations of nitrogen dioxide and ozone. The paper examines the performance of the integrated modelling system to predict concentrations from emission sources in Greater London. Predictions have been compared with observed data at four locations, two locations in Central London and two in East London. Predicted concentrations for a summer and winter period have been calculated and modelled and measured times series data have been compared. Statistical analyses have been carried out to assist in the comparison of model predictions with monitored data. Although no absolute significance can be attached to the numerical values of these measures, taken cumulatively, some conclusions regarding the emissions inventory data and the models’ performance can be made. The applicability of the model of atmospheric chemistry used in this study to calculate the concentrations of nitrogen dioxide is appraised and a comparison has been made with concentrations of nitrogen dioxide predicted from oxides of nitrogen using empirical relationships.
Keywords: Dispersion modelling; Urban emissions inventory; Semi-empirical photochemical model; Nitrogen dioxide; Local air quality management;

Following the experiences after the Chernobyl accident in 1986, Norwegian Authorities regard the effects from accidental releases at nuclear installations in neighboring countries to be among the greatest environmental threats in the coming years. One of these nuclear installations is the Kola Nuclear Power Plant (Kola NPP). The unsatisfactory safety at the Kola NPP has been of major concern and a `Norwegian Plan of Action for Nuclear Safety’ has been worked out (. Plan of action for follow-up activities to Report no. 34 to Norwegian parliament (1993–1994)). As a response to this plan, DNMI has been involved in a project called: `Consequence Analysis of Potential Accidents at the Kola Nuclear Power Plant'. DNMI's part of the project consisted of analyzing the atmospheric transport and deposition pattern resulting from potential accidents at the Kola NPP. Results based on two different methodologies are presented in this paper. (1) Trajectory analysis as a tool for describing the air pollution transport pattern and screening of a large set of meteorological data for the selection of weather situations suitable for episode studies. (2) Episode studies using DNMI's dispersion model `Severe Nuclear Accident Program’ (SNAP) for the selected episodes.
Keywords: Trajectory analysis; Travel time statistics; Criteria for worst case; Episode studies; Dispersion model; Simulations; Nuclear accidents; Radioactive deposition;

Toxicity and health effects of vehicle emissions in Shanghai by Shun-Hua Ye; Wei Zhou; Jian Song; Bao-Cheng Peng; Dong Yuan; Yuan-Ming Lu; Ping-Ping Qi (419-429).
In China, the number of vehicles is increasing rapidly with the continuous development of economy, and vehicle emission pollution in major cities is more serious than ever. In this article, we summarized the results of a series of short-term assays, animal experiments and epidemiology investigations on the genotoxicity, immunotoxicity, respiratory toxicity and health effects of vehicle emissions in Shanghai, including gasoline exhausts (gas condensate and particles), diesel exhaust particles (DEP) and scooter exhaust particles (SEP). The results showed that: (1) Both gases and particulate phases of the exhausts of different kinds of vehicles showed strong mutagenicity in Ames test (TA98 and TA100 strains), rat hepatocyte unscheduled DNA synthesis (UDS) assay, and mouse micronucleus assay, and vehicle emissions could induce the transformation of Syrian hamster embryo (SHE) cells. DEP and SEP could induce the transformation of human diploid cell strain (KMB-13) cells, immunohistochemistry assay showed that c-myc and p21 proteins were highly expressed in the transformed cells. DEP and SEP could also inhibit the gap junctional intercellular communication (GJIC) of BALB/C3T3 cells (2) Vehicle emissions could decrease the number of macrophages in the lung (bronchial alveolar lavage fluid) (BALF) of male SD rats. Vehicle emissions could also increase the proportion of polymorphonuclear leukocytes (PMN), the content of cetyneuraminic acid (NA), the activity of lactate dehydrogenase (LDH), alkali phosphate (AKP), acid phosphate (ACP) in the lung BALF of the animals. (3) In epidemiology investigation, the proportion of those who have respiratory symptoms and chronic obstructive pulmonary diseases (COPD) in the workers who were exposed to DEP (n=806) were much higher than those of the controls (n=413). The OR (odd ratio) values of angina, nasal obstruction, phlegm, short of breath and COPD were 2.27, 3.08, 3.00, 3.19 and 2.32, respectively, and the proportion of those who have indisposed sensation of nose or laryngopharynx, cough, phlegm and pharyngitis in the workers who were occupationally exposed to gasoline exhausts (n=157) were also higher than those of controls (n=121), the OR values were 2.43, 3.76, 2.58, and 3.70, respectively, and in the 40 gasoline exhausts exposed workers, the frequencies of 6-TG (thioguanine), sister chromatid exchanges (SCEs) and micronuclei in peripheral blood were markedly higher (P<0.05) than those of controls. The SI (T lymphocytes transformation) activity, total E rosette, E active rosette, content of immunoglobulin A (IgA) and fibrin (FN) of the exposed group were significantly (P<0.05) decreased compared with those of the control. All the results showed that vehicle emissions could not only induce adverse effects on respiratory and immune system of occupationally exposed people, but also have potential carcinogenicity to human beings.
Keywords: Vehicle emissions; Gasoline exhaust; Diesel exhaust particles; Scooter exhaust particles; Toxicity; Health effects;

Vertical profiles of free tropospheric humidity, aerosol backscattering and the depolarization ratio (particle nonsphericity) were measured with a Raman lidar at Nagoya (35.1°N, 137.0°E) from March 1994 to February 1997 to study the seasonal and altitude characteristics of the aerosol optical properties. We analyzed the relation of these characteristics to relative humidity (RH) and the transport pathways from the source areas. The vertically integrated aerosol backscattering coefficients (IBC) in the altitude ranges of 2–4 and 4–8 km showed an annual maximum in the spring (March–May). A second maximum of IBC was found in 2–4 km in mid-late summer (July–August). Aerosol depolarization ratios as high as 25% were observed frequently in the 2–8 km region in the spring and occasionally in the 4–8 km region in the autumn (September–November) and winter (December–February). In the 4–8 km regions these high values were observed over a wide range of RH values. Depolarization ratios less than 5% with RH values less than 20% were predominantly observed in the winter. The air parcels in these regions had mainly passed over the Asian Continent. Depolarization ratios less than 5% over a wide range of RH and high depolarization ratios (>10%) with relatively low RH values (<50%) were predominantly observed in the 2–8 km region in the summer and in the 2–4 km region in the autumn; most of the air parcels had passed over the Pacific Ocean. Our results suggest that transport pathways from the source areas (the Asian Continent and the Pacific Ocean) and the ambient relative humidity critically control the aerosol depolarization ratio in the free troposphere over Nagoya.
Keywords: Aerosols; Particles; Particle nonsphericity; Particle transport; Vertical particle distribution;

Nanoparticle air pollution in major cities and its origin by Qian Zhiqiang; Konstantin Siegmann; Alejandro Keller; Ulrich Matter; Leo Scherrer; H.C Siegmann (443-451).
Suspended particles with a diameter below 1 μm act as vehicles transporting toxic chemicals into the human respiratory system. It is therefore of interest to record the intensity of these particles and to determine the source from which they were emitted. It is shown that this can be done by simultaneously measuring the light scattering (LS), the photoelectric charging (PC), and the diffusion charging (DC). Particles carrying polycyclic aromatic hydrocarbons (PPAH) are detected by their large PC and are generated in combustion of organic materials whereas particles from other sources only exhibit LS and DC. The fraction of particle mass due to PPAH is independent of location and weather conditions. As an example of an application, we study the nanoscale particles found on motorways in or near various large cities. The sources of the majority of these particles are Diesel motors or cars with defect catalysts. Promising strategies for improving the air quality emerge from these observations.
Keywords: Soot; Diesel; PAH; Particle; Combustion engine; Photoelectric charging; Diffusion charging;

A method was developed in this paper to estimate the spatial and temporal distribution of vehicle emissions and concentrations in Beijing based on the limited database. The vehicle sources were treated as both line sources and area sources to make full use of the available data. For line sources, substantial counting of vehicles on site had been conducted to determine the traffic flow and vehicle type mixture; for area sources, the total non-line-source vehicle-traveled mileage was distributed to different grids based on population density and road area in the grids. A mathematical dispersion model, Industrial Sources Complex Short Term Version 3 (ISCST3), was used to simulate the pollutant concentration distribution in urban areas based on the meteorological data and the emissions distribution mentioned above. The verification data show that method is accurate in the Beijing urban area, and the results show that the vehicle emissions in Beijing contributed significantly to the simulated pollutant impact, and the polluted areas correlate with population.
Keywords: Air quality; Emission factor; Emission intensity; ISCST3; Distribution;

The aim of this modelling study is to understand and quantify the influence of biogenic volatile organic compound (BVOC) emissions on the formation of tropospheric ozone in the Burriana area (north of Valencia) on the east coast of Spain. The mesoscale modelling system used consists of the meteorology/transport module TVM and the chemical reaction mechanism RACM. The results of the model simulations are validated and compared with the data collected during the biogenic emissions in the mediterranean area (BEMA) field campaign that took place in June 1997. Anthropogenic and biogenic emission inventories have been constructed with an hourly resolution. Averaged (over the land area and over 24 h) emission fluxes for AVOC, anthropogenic NO x , BVOC and biogenic NO x are given by 16.0, 9.9, 6.2, and 0.7 kg km−2  day−1, respectively. The impact of biogenic emissions is investigated on peak ozone values by performing simulations with and without biogenic emissions, while keeping anthropogenic emissions constant. The impact on ozone formation is also studied in combination with some anthropogenic emissions reduction strategies, i.e. when anthropogenic VOC emissions and/or NO x emissions are reduced. A factor separation technique is applied to isolate the impact due to biogenic emissions from the overall impact due to biogenic and anthropogenic emissions together. The results indicate that the maximum impact of biogenic emissions on ozone formation represents at the most 10 ppb, while maximum ozone values are of the order of 100 ppb. At different locations the maximum impact is reached at different times of the day depending on the arrival time of the sea breeze. It is also shown that this impact does not coincide in time with the maximum simulated ozone concentrations that are reached over the day. By performing different emission reduction scenarios, BVOC impacts are found to be sensitive mainly to NO x , and not to AVOC. Finally, it is shown that amongst the various BVOCs emitted by the citrus plantations in Burriana, the carbonyl species contribute the most to ozone formation.
Keywords: Mesoscale modelling; Biogenic emissions; Emission scenarios; Factor analysis;

A 3-D numerical investigation is carried out to assess the impact of a forest fire in northeastern China on the photochemical oxidant cycle of east Asia. Two simulations, without and with the emissions from the fire, are carried out during springtime in May 1987. The fire, located more towards the north, impacted the northern parts of Japan and the model domain, where an increase in ozone (5–10 ppb) is predicted for most of the second half of the month. A monthly averaged increase of ∼30% in the boundary layer ozone is predicted close to the fire source area. Our results indicate the influence of the fire on the tropospheric trace gas cycle over most of China, Japan and the Korean peninsula to be minimal, although an increase (∼40%) is predicted over Japan towards the end of the month. Favorable comparisons over the source region are obtained for the predicted column loadings due to the black carbon from the fire and the aerosol index from satellite measurements. On a monthly average basis, high values of the aerosol index (>1) and black carbon column loading (>20 mg m−2) are observed over the source regions.
Keywords: Numerical modeling; Emission estimates; Tropospheric ozone; Black carbon; Aerosol index;

Urban air pollution is a major environmental problem in several developing countries in the world. This phenomenon seems to be related to the growth of both the urban population in large cities and the number of old and poorly maintained car fleets. The expected rise of population in the next century in countries which suffer from lack of capital for air pollution control, means that there is a great potential for the worsening of the air quality. The worldwide promoted policy to phase out lead in gasolines has not proved to be an adequate option in improving the environmental quality. Mexico City Metropolitan Area (MCMA) represents a case in which the introduction of reformulated gasolines in an old car fleet has given as a result the reduction of the airborne lead levels but has worsened the ozone concentration of its urban atmosphere. This paper critically analyzes the chronological evolution of the ozone air pollution problem in MCMA after the successive occurrence of several changes in the formulation of low leaded and unleaded gasolines. It also presents evidences of the usefulness potential of air quality monitoring activities and air quality impact studies on the definition of realistic fuel reformulation policies of developing countries.
Keywords: Ozone urban air pollution; Reformulated gasoline; Mexico City;

Data from both 27 sites in the Atlanta mesonet surface meteorological network and eight National Weather Service sites were analyzed for the period from 26 July to 3 August 1996. Analysis of the six precipitation events over the city during the period (each on a different day) showed that its urban heat island (UHI) induced a convergence zone that initiated three of the storms at different times of the day, i.e., 0630, 0845, and 1445 EDT. Previous analysis has shown that New York City (NYC) effects summer daytime thunderstorm formation and/or movement. That study found that during nearly calm regional flow conditions, the NYC UHI initiates convective activity. Moving thunderstorms, however, tended to bifurcate and to move around the city, due to its building barrier effect. The current Atlanta results thus agree with the NYC results with respect to thunderstorm initiation.
Keywords: Urban precipitation; Urban heat islands; Urban convergence zones;