Atmospheric Environment (v.43, #40)
Editorial board (i).
Descriptive mathematical techniques to study historical data: An application to sulfur dioxide pollution in the city of Talcahuano – Chile by Pedro Pedrero; Carmen Tardón; Enrique López (6279-6286).
This paper proposes three mathematical approaches that can be used to study chemical atmospheric data related to air quality: a) Descriptive statistical analysis, b) Fourier analysis and c) Wavelet analysis. These techniques are used to improve understanding of SO2 pollution in the city of Talcahuano (Chile).The results show high SO2 dispersion values, an annual average standard deviation of 63.5 μg m−3 and a Pearson coefficient of variation of 1.59. The asymmetry and kurtosis coefficients (3.1 and 14.3, respectively) confirm the “non-Gaussianity” of the SO2 concentrations. The main fluctuations of the data studied are due to seasonal and daily cyclical components. Important annual irregularities are detected by the wavelet analysis of daily cycles, especially in winter. This cyclical component is fundamentally due to meteorological factors (because the zonal industrial emissions, mainly emitted by Oil Refining Plant, are roughly constant). Non-negligible correlations, between SO2 concentration and several meteorological variables (vertical wind, temperature, solar radiation, horizontal wind), were also verified (0.49, 0.40, 0.36 and 0.34, respectively).
Keywords: Descriptive statistics; Fourier transform; Wavelet analysis; Sulfur dioxide (SO2); Air quality; Correlation analysis;
Mass conservative, positive definite integrator for atmospheric chemical dynamics by Khoi Nguyen; Alexandre Caboussat; Donald Dabdub (6287-6295).
Air quality models compute the transformation of species in the atmosphere undergoing chemical and physical changes. The numerical algorithms used to predict these transformations should obey mass conservation and positive definiteness properties. Among all physical phenomena, the chemical kinetics solver provides the greatest challenge to attain these two properties. In general, most chemical kinetics solvers are mass conservative but not positive definite. In this article, a new numerical algorithm for the computation of chemical kinetics is presented. The integrator is called Split Single Reaction Integrator (SSRI). It is both mass conservative and positive definite. It solves each chemical reaction exactly and uses operator splitting techniques (symmetric split) to combine them into the entire system.The method can be used within a host integrator to fix the negative concentrations while preserving the mass, or it can be used as a standalone integrator that guarantees positive definiteness and mass conservation. Numerical results show that the new integrator, used as a standalone integrator, is second order accurate and stable under large fixed time steps when other conventional integrators are unstable.
Keywords: Chemical integrator; Mass conservation; Positive definiteness; Operator splitting; Chemical kinetics;
An evaluation of the PM2.5 trace elemental composition in the Venice Lagoon area and an analysis of the possible sources by A.M. Stortini; A. Freda; D. Cesari; W.R.L. Cairns; D. Contini; C. Barbante; F. Prodi; P. Cescon; A. Gambaro (6296-6304).
Global emissions reported by many authors have shown as natural and anthropic sources can contribute to the principal aerosol classes, but values change according the local scenario. The Venice Lagoon is exposed to different anthropic source emissions like vehicular traffic, industrial thermoelectric power plant, petrochemical plant, incinerator plant, domestic heating, ship traffic, glass factories and airport. Samplings of PM2.5 were daily performed between March and November 2007 in Sacca San Biagio island (Venice), and values of PM2.5 concentration and element concentration were obtained. Monthly average concentrations (μg m−3) during this period show higher values during the spring and the autumn. A good relationship between data obtained and concentration values from environmental local agencies is evidenced, both for PM2.5 from urban area (Venezia Mestre), and for PM10 sampled in the same area, as well as the influence of some meteorological parameters on PM2.5 concentration sampled. Trace elements samples were measured by an Inductively Coupled Plasma-Quadrupole Mass Spectrometry (ICP-QMS), and values (ng m−3 and μg g−1) for elements regulated by European directives (As, Cd, Ni, Pb), as well as, other elements (Na, Al, K, Ti, V, Mn, Fe, Co, Zn, Se, Ag) are also reported. Data analysis by mean of Principal Component Analysis (PCA) and Positive Matrix Factorization (PMF) pointed out four principal groups of elements like Mn–Fe–K, As–Se–Cd, V–Co, and Pb that could be assigned to specific sources of the Venetian wetland basin.
Keywords: Trace elements; Venice lagoon; PM2.5; PCA; PMF;
Measurement of black carbon (BC) by an optical method and a thermal-optical method: Intercomparison for four sites by Tanveer Ahmed; Vincent A. Dutkiewicz; Akhtar Shareef; Gurdal Tuncel; Semra Tuncel; Liaquat Husain (6305-6311).
Comparison of black carbon (BC) measurements obtained by two methods was performed for aerosols samples collected on Whatman 41 (W-41) filters, using an optical method (Magee Scientific Optical Transmissometer Model OT-21) and a thermal-optical method (Sunset Laboratory Thermal-optical analyzer). Samples were collected from four sites: Albany (a small urban site, NY), Antalya (coastal site, Turkey), Whiteface Mountain (remote site, NY) and Mayville (rural site, NY). At Albany, comparison between the two methods showed excellent agreement; a least-squares regression line yielded a slope of 1.02, and r 2 = 0.88. Similar comparisons at Antalya (slope of 1.02, r 2 = 0.5) and Whiteface Mountain (slope of 0.92 and r 2 = 0.58) also gave very good relationship. At Mayville, the relationship between the two methods yielded somewhat lower regression: a slope of 0.75, and r 2 = 0.44. The data from the four locations, when plotted together, yielded an excellent agreement: a slope of 0.91, and r 2 of 0.84. Based on our measurements, it appears that optical measurement using the OT-21 can be successfully applied to determination of BC in W-41 filters. However, because of the variability in the chemical composition of BC aerosol at different locations, it is suggested that the calibration of OT-21 when using W-41 filters should be performed with a statistically significant numbers of samples for specific sites.
Keywords: Black carbon; Whatman 41; Transmissometer; Light absorption;
Targeting of observations for accidental atmospheric release monitoring by Rachid Abida; Marc Bocquet (6312-6327).
In the event of an accidental atmospheric release of radionuclides from a nuclear power plant, accurate real-time forecasting of the activity concentrations of radionuclides is acutely required by the decision makers for the preparation of adequate countermeasures. Yet, the accuracy of the forecasted plume is highly dependent on the source term estimation. Inverse modelling and data assimilation techniques should help in that respect. However the plume can locally be thin and could avoid a significant part of the radiological monitoring network surrounding the plant. Deploying mobile measuring stations following the accident could help to improve the source term estimation. In this paper, a method is proposed for the sequential reconstruction of the plume, by coupling a sequential data assimilation algorithm based on inverse modelling with an observation targeting strategy. The targeting design strategy consists in seeking the optimal locations of the mobile monitors at time t + 1 based on all available observations up to time t.The performance of the sequential assimilation with and without targeting of observations has been assessed in a realistic framework. It focuses on the Bugey nuclear power plant (France) and its surroundings within 50 km from the plant. The existing surveillance network is used and realistic observational errors are assumed. The targeting scheme leads to a better estimation of the source term as well as the activity concentrations in the domain. The mobile stations tend to be deployed along plume contours, where activity concentration gradients are important. It is shown that the information carried by the targeted observations is very significant, as compared to the information content of fixed observations. A simple test on the impact of model error from meteorology shows that the targeting strategy is still very useful in a more uncertain context.
Keywords: Radionuclides dispersion; Accidental release modelling; Data assimilation; Inverse modelling; Network design;
Revised estimates of construction activity and emissions: Effects on ozone and elemental carbon concentrations in southern California by Dev E. Millstein; Robert A. Harley (6328-6335).
Emissions from diesel-powered construction equipment are an important source of nitrogen oxides (NOx) and particulate matter (PM). A new emission inventory for construction equipment emissions is developed based on surveys of diesel fuel use; the revised inventory is compared to current emission inventories. California's OFFROAD model estimates are 4.5 and 3.1 times greater, for NOx and PM respectively, than the fuel-based estimates developed here. The most relevant uncertainties are the overall amount of construction activity/diesel fuel use, exhaust emission factors for PM and NOx, and the spatial allocation of emissions to county level and finer spatial scales. Construction permit data were used in this study to estimate spatial distributions of emissions; the resulting distribution is well correlated with population growth. An air quality model was used to assess the impacts of revised emission estimates. Increases of up to 15 ppb in predicted peak ozone concentrations were found in southern California. Elemental carbon and fine particle mass concentrations were in better agreement with observations using revised emission estimates, whereas negative bias in predictions of ambient NOx concentrations increased.
Keywords: Diesel; Construction; Emissions; PM; Ozone;
Prediction of PM10 concentrations at urban traffic intersections using semi-empirical box modelling with instantaneous velocity and acceleration by Hong-di He; Wei-Zhen Lu; Yu Xue (6336-6342).
At urban traffic intersections, vehicles frequently stop with idling engines during the red-light period and speed up rapidly during the green-light period. The changes of driving patterns (i.e., idle, acceleration, deceleration and cruising patterns) generally produce uncertain emission. Additionally, the movement of pedestrians and the influence of wind further result in the random dispersion of pollutants. It is, therefore, too complex to simulate the effects of such dynamics on the resulting emission using conventional deterministic causal models.For this reason, a modified semi-empirical box model for predicting the PM10 concentrations on roadsides is proposed in this paper. The model constitutes three parts, i.e., traffic, emission and dispersion components. The traffic component is developed using a generalized force traffic model to obtain the instantaneous velocity and acceleration when vehicles move through intersections. Hence the distribution of vehicle emission in street canyon during the green-light period is calculated. Then the dispersion component is investigated using a semi-empirical box model combining average wind speed, box height and background concentrations. With these considerations, the proposed model is applied and evaluated using measured data at a busy traffic intersection in Mong Kok, Hong Kong. In order to test the performance of the model, two situations, i.e., the data sets within a sunny day and between two sunny days, were selected to examine the model performance. The predicted values are generally well coincident with the observed data during different time slots except several values are overestimated or underestimated. Moreover, two types of vehicles, i.e., buses and petrol cars, are separately taken into account in the study. Buses are verified to contribute most to the emission in street canyons, which may be useful in evaluating the impact of vehicle emissions on the ambient air quality when there is a significant change in a specific vehicular population.
Keywords: Semi-empirical box model; PM10 concentration; Vehicle emission; Traffic intersection; Roadway;
Emissions of gas- and particle-phase polycyclic aromatic hydrocarbons (PAHs) in the Shing Mun Tunnel, Hong Kong by K.F. Ho; Steven Sai Hang Ho; S.C. Lee; Y. Cheng; Judith C. Chow; John G. Watson; P.K.K. Louie; Linwei Tian (6343-6351).
Real-world vehicle emission factors for seventeen gas and particulate polycyclic aromatic hydrocarbons (PAHs) were quantified in the Shing Mun Tunnel, Hong Kong during summer and winter 2003. Naphthalene, acenaphthylene, and acenaphthene were the most abundant gas PAHs while fluoranthene and pyrene were the most abundant in the particle phase. Most (98%) of the gas PAHs consisted of two- and three-aromatic rings whereas most of the particle-phase PAHs were in four- (∼60%) and five-ring (∼17%) for fresh exhaust emissions. Average emission factors for the gas- and particle PAHs were 950–2564 μg veh−1 km−1 and 22–354 μg veh−1 km−1, respectively. Good correlations were found between diesel markers (fluoranthene and pyrene; 0.85) and gasoline markers (benzo[ghi]perylene and indeno[1,2,3-cd]pyrene; 0.96). Higher PAH emission factors were associated with a higher fraction of diesel-fueled vehicles (DV) passing through the tunnel. Separate emission factors were determined from diesel and non-diesel exhaust by the regression intercept method. The average PAH emission factor (i.e., sum of gas and particle phases) from DV (3085 ± 1058 μg veh−1 km−1) was ∼5 times higher than that from non-diesel-fueled vehicles (NDV, 566 ± 428 μg veh−1 km−1). Ratios of DV to NDV emission factors were high for diesel markers (>24); and low for gasoline markers (<0.4).
Keywords: PAH; Gas- and particle PAHs; Emission factor; Tunnel; Hong Kong;
Comparative study on indoor air quality in Japan and China: Characteristics of residential indoor and outdoor VOCs by Takeshi Ohura; Takashi Amagai; Xueyou Shen; Shuang Li; Ping Zhang; Lizhong Zhu (6352-6359).
We conducted a comparative study on the indoor air quality for Japan and China to investigate aromatic volatile organic compounds (VOCs) in indoor microenvironments (living room, bedroom, and kitchen) and outdoors in summer and winter during 2006–2007. Samples were taken from Shizuoka in Japan and Hangzhou in China, which are urban cities with similar latitudes. Throughout the samplings, the indoor and outdoor concentrations of many of the targeted VOCs (benzene, toluene, ethylbenzene, xylenes, and trimethylbenzenes) in China were significantly higher than those in Japan. The indoor concentrations of VOCs in Japan were somewhat consistent with those outdoors, whereas those in China tended to be higher than those outdoors. Here, we investigated the differences in VOC concentrations between Japan and China. Compositional analysis of indoor and outdoor VOCs showed bilateral differences; the contribution of benzene in China was remarkably higher than that in Japan. Significant correlations (p < 0.05) for benzene were observed among the concentrations in indoor microenvironments and between the outdoors and living rooms or kitchens in Japan. In China, however, significant correlations were observed only between living rooms and bedrooms. These findings suggest differences in strengths of indoor VOC emissions between Japan and China. The source characterizations were also investigated using principal component analysis/absolute principal component scores. It was found that outdoor sources including vehicle emission and industrial sources, and human activity could be significant sources of indoor VOC pollution in Japan and China respectively. In addition, the lifetime cancer risks estimated from unit risks and geometric mean indoor concentrations of carcinogenic VOCs were 2.3 × 10−5 in Japan and 21 × 10−5 in China, indicating that the exposure risks in China were approximately 10 times higher than those in Japan.
Keywords: Volatile organic compounds; Indoor air quality; Emission sources; Source apportionment; Cancer risk;
Redox activity of urban quasi-ultrafine particles from primary and secondary sources by Vishal Verma; Zhi Ning; Arthur K. Cho; James J. Schauer; Martin M. Shafer; Constantinos Sioutas (6360-6368).
To characterize the redox activity profiles of atmospheric aerosols from primary (traffic) and secondary photochemical sources, ambient quasi-ultrafine particles were collected near downtown Los Angeles in two different time periods – morning (6:00–9:00 PDT) and afternoon (11:00–14:00 PDT) in the summer of 2008. Detailed chemical analysis of the collected samples, including water-soluble elements, inorganic ions, organic species and water soluble organic carbon (WSOC) was conducted and redox activity of the samples was measured by two different assays: the dithiothreitol (DTT) and the macrophage reactive oxygen species (ROS) assays. Tracers of secondary photochemical reactions, such as sulfate and organic acids were higher (2.1 ± 0.6 times for sulfate, and up to 3 times for the organic acids) in the afternoon period. WSOC was also elevated by 2.5 ± 0.9 times in the afternoon period due to photo-oxidation of primary particles during atmospheric aging. Redox activity measured by the DTT assay was considerably higher for the samples collected during the afternoon; on the other hand, diurnal trends in the ROS-based activity were not consistent between the morning and afternoon periods. A linear regression between redox activity and various PM chemical constituents showed that the DTT assay was highly correlated with WSOC (R 2 = 0.80), while ROS activity was associated mostly with water soluble transition metals (Vanadium, Nickel and Cadmium; R 2 > 0.70). The DTT and ROS assays, which are based on the generation of different oxidizing species by chemical PM constituents, provide important information for elucidating the health risks related to PM exposure from different sources. Thus, both primary and secondary particles possess high redox activity; however, photochemical transformations of primary emissions with atmospheric aging enhance the toxicological potency of primary particles in terms of generating oxidative stress and leading to subsequent damage in cells.
Keywords: Quasi-ultrafine particles; Redox-active species; Dithiothreitol (DTT); Macrophage ROS; Photochemical processes; Traffic sources;
Ozone recovery as seen in perspective of the Dobson spectrophotometer measurements at Belsk (52°N, 21°E) in the period 1963–2008 by Janusz W. Krzyścin; Bonawentura Rajewska-Więch (6369-6375).
The total ozone monthly means derived from measurements by the Dobson spectrophotometer at Belsk (52°N, 21°E) and satellite observations over central and midlatitudinal Europe are analyzed for the long-term changes between 1995 and 2008. Standard explanatory variables representing physical and chemical processes known to influence the ozone distribution are considered. The potential proxies are: atmospheric loading by the ozone depleting substances characterized by the equivalent effective stratospheric chlorine (EESC) time series, various drivers of ozone dynamical variability including solar cycle, teleconnection patterns, temperature at 50 hPa, and pressure at the tropopause level. The multivariate adaptive regression splines (MARS) methodology is used to find optimal set of the explanatory variables and shape of the anthropogenic trend curve. Following options for the trend curve are examined: proportional to EESC, piecewise linear (with the turning points in 1980 and 1995), and selected from a smooth curve fit to the total ozone time series having “natural variations” removed. Statistical estimates and their uncertainties are calculated using block bootstrapping. The analyses indicate that ozone over Belsk, in central Europe, and in midlatitudinal Europe reaches at least first stage of recovery as defined by the World Meteorological Organization: a statistically significant reduction in the rate of decline. Model using the EESC time series as a proxy for the anthropogenic trend pattern yields even the second stage, i.e., a positive trend in time series that remains after removal dynamical signal from the analyzed data. Substantial seasonal dependent long-term ozone oscillations by the dynamical drivers are revealed causing estimation of the ozone recovery time even more uncertain.
Keywords: Stratospheric ozone; Anthropogenic and dynamics trend; Ozone recovery;
Influence of tobacco smoke on carcinogenic PAH composition in indoor PM10 and PM2.5 by K. Slezakova; D. Castro; M.C. Pereira; S. Morais; C. Delerue-Matos; M.C. Alvim-Ferraz (6376-6382).
Because of the mutagenic and/or carcinogenic properties, Polycyclic Aromatic Hydrocarbons (PAH), have a direct impact on human population. Consequently, there is a widespread interest in analysing and evaluating the exposure to PAH in different indoor environments, influenced by different emission sources. The information on indoor PAH is still limited, mainly in terms of PAH distribution in indoor particles of different sizes; thus, this study evaluated the influence of tobacco smoke on PM10 and PM2.5 characteristics, namely on their PAH compositions, with further aim to understand the negative impact of tobacco smoke on human health. Samples were collected at one site influenced by tobacco smoke and at one reference (non-smoking) site using low-volume samplers; the analyses of 17 PAH were performed by Microwave Assisted Extraction combined with Liquid Chromatography (MAE–LC). At the site influenced by tobacco smoke PM concentrations were higher 650% for PM10, and 720% for PM2.5. When influenced by smoking, 4 ring PAH (fluoranthene, pyrene, and chrysene) were the most abundant PAH, with concentrations 4600–21 000% and 5100–20 800% higher than at the reference site for PM10 and PM2.5, respectively, accounting for 49% of total PAH (ΣPAH). Higher molecular weight PAH (5–6 rings) reached concentrations 300–1300% and 140–1700% higher for PM10 and PM2.5, respectively, at the site influenced by tobacco smoke. Considering 9 carcinogenic PAH this increase was 780% and 760% in PM10 and PM2.5, respectively, indicating the strong potential risk for human health. As different composition profiles of PAH in indoor PM were obtained for reference and smoking sites, those 9 carcinogens represented at the reference site 84% and 86% of ΣPAH in PM10 and PM2.5, respectively, and at the smoking site 56% and 55% of ΣPAH in PM10 and PM2.5, respectively. All PAH (including the carcinogenic ones) were mainly present in fine particles, which corresponds to a strong risk for cardiopulmonary disease and lung cancer; thus, these conclusions are relevant for the development of strategies to protect public health.
Keywords: PM10; PM2.5; PAH; Indoor; Tobacco smoke; MAE–LC;
Examination of the impact of photoexcited NO2 chemistry on regional air quality by Golam Sarwar; Robert W. Pinder; K. Wyat Appel; Rohit Mathur; Annmarie G. Carlton (6383-6387).
Impact of the excited nitrogen dioxide (NO2 ∗) chemistry on air quality in the U.S. is examined using the Community Multiscale Air Quality (CMAQ) model for a summer month. Model simulations were conducted with and without the NO2 ∗ chemistry. The largest impact of the NO2 ∗ chemistry in the eastern U.S. occurred in the northeast and in the western U.S. occurred in Los Angeles. While the single largest daily maximum 8-h ozone (O3) increased by 9 ppbv in eastern U.S. and 6 ppbv in western U.S., increases on most days were much lower. No appreciable change in model performance statistics for surface-level O3 predictions relative to measurements is noted between simulations with and without the NO2 ∗ chemistry. Based on model calculations using current estimates of tropospheric emission burden, the NO2 ∗ chemistry can increase the monthly mean daytime hydroxyl radicals (OH) and nitrous acid (HONO) by a maximum of 28% and 100 pptv, respectively.
Keywords: Excited NO2 chemistry; Ozone; Hydroxyl radical; Nitrous acid; Air quality model;
Estimating trace gas and aerosol emissions over South America: Relationship between fire radiative energy released and aerosol optical depth observations by Gabriel Pereira; Saulo R. Freitas; Elisabete Caria Moraes; Nelson Jesus Ferreira; Yosio Edemir Shimabukuro; Vadlamudi Brahmananda Rao; Karla M. Longo (6388-6397).
Contemporary human activities such as tropical deforestation, land clearing for agriculture, pest control and grassland management lead to biomass burning, which in turn leads to land-cover changes. However, biomass burning emissions are not correctly measured and the methods to assess these emissions form a part of current research area. The traditional methods for estimating aerosols and trace gases released into the atmosphere generally use emission factors associated with fuel loading and moisture characteristics and other parameters that are hard to estimate in near real-time applications. In this paper, fire radiative power (FRP) products were extracted from Moderate Resolution Imaging Spectroradiometer (MODIS) and from the Geostationary Operational Environmental Satellites (GOES) fire products and new South America generic biomes FRE-based smoke aerosol emission coefficients were derived and applied in 2002 South America fire season. The inventory estimated by MODIS and GOES FRP measurements were included in Coupled Aerosol-Tracer Transport model coupled to the Brazilian developments on the Regional Atmospheric Modeling System (CATT-BRAMS) and evaluated with ground truth collected in Large Scale Biosphere–Atmosphere Smoke, Aerosols, Clouds, rainfall, and Climate (SMOCC) and Radiation, Cloud, and Climate Interactions (RaCCI). Although the linear regression showed that GOES FRP overestimates MODIS FRP observations, the use of a common external parameter such as MODIS aerosol optical depth product could minimize the difference between sensors. The relationship between the PM2.5μm (Particulate Matter with diameter less than 2.5 μm) and CO (Carbon Monoxide) model shows a good agreement with SMOCC/RaCCI data in the general pattern of temporal evolution. The results showed high correlations, with values between 0.80 and 0.95 (significant at 0.5 level by student t test), for the CATT-BRAMS simulations with PM2.5μm and CO.
Keywords: Fire radiative power; Smoke aerosol emission coefficient; Aerosol optical depth; Biomass burning;
Summertime photochemical ozone formation in Santiago, Chile by Y.F. Elshorbany; J. Kleffmann; R. Kurtenbach; M. Rubio; E. Lissi; G. Villena; E. Gramsch; A.R. Rickard; M.J. Pilling; P. Wiesen (6398-6407).
The city of Santiago, Chile experiences frequent high pollution episodes and as a consequence very high ozone concentrations, which are associated with health problems including increasing daily mortality and hospital admissions for respiratory illnesses. The development of ozone abatement strategies requires the determination of the potential of each pollutant to produce ozone, taking into account known mechanisms and chemical kinetics in addition to ambient atmospheric conditions. In this study, the photochemical formation of ozone during a summer campaign carried out from March 8–20, 2005 has been investigated using an urban photochemical box model based on the Master Chemical Mechanism (MCMv3.1). The MCM box model has been constrained with 10 min averages of simultaneous measurements of HONO, HCHO, CO, NO, j(O1D), j(NO2), 31 volatile organic compounds (VOCs) and meteorological parameters. The O3–NOx–VOC sensitivities have been determined by simulating ozone formation at different VOC and NOx concentrations. Ozone sensitivity analyses showed that photochemical ozone formation is VOC-limited under average summertime conditions in Santiago. The results of the model simulations have been compared with a set of potential empirical indicator relationships including H2O2/HNO3, HCHO/NOy and O3/NOz. The ozone forming potential of each measured VOC has been determined using the MCM box model. The impacts of the above study on possible summertime ozone control strategies in Santiago are discussed.
Keywords: Tropospheric ozone; Ozone sensitivity; Urban photochemistry; Master chemical mechanism; Santiago de Chile;
Characterisation of single particles from in-port ship emissions by Robert M. Healy; Ian P. O'Connor; Stig Hellebust; Arnaud Allanic; John R. Sodeau; John C. Wenger (6408-6414).
Emissions from shipping traffic may impact severely upon air quality in port cities. In this study, the size and composition of freshly emitted individual ship exhaust particles has been investigated using an aerosol time-of-flight mass spectrometer (ATOFMS) co-located with a suite of real-time instrumentation at a site in the Port of Cork, Ireland. The collected spectra were clustered using the K-means algorithm and a unique ship exhaust class containing internally mixed elemental and organic carbon, sodium, calcium, iron, vanadium, nickel and sulfate was identified. Over twenty sharp emission events were observed for this particle type during the three week measurement period in August 2008. Coincident increases in mass concentrations of sulfate, elemental carbon and particles below 2.5 μm in diameter (PM2.5) were also observed during these events. Simultaneous scanning mobility particle sizer (SMPS) measurements indicate that the vast majority of freshly emitted ship exhaust particles lie in the ultrafine mode (<100 nm diameter). A second particle class consisted of internally mixed organic carbon, elemental carbon, ammonium and sulfate, and is tentatively attributed to aged or regionally transported ship exhaust. The results suggest that ATOFMS single particle mass spectra, when used in conjunction with other air quality monitoring instrumentation, may be useful in determining the contribution of local shipping traffic to air quality in port cities.
Keywords: Ship emissions; Atmospheric particle composition; Air quality; Port cities;
A computational study of particulate emissions from an open pit quarry under neutral atmospheric conditions by S.A. Silvester; I.S. Lowndes; D.M. Hargreaves (6415-6424).
The extraction of minerals from surface mines and quarries can produce significant fugitive dust emissions as a result of site activities such as blasting, road haulage, loading, crushing and stockpiling. If uncontrolled, these emissions can present serious environmental, health, safety and operational issues impacting both site personnel and the wider community.The dispersion of pollutant emissions within the atmosphere is principally determined by the background wind systems characterized by the atmospheric boundary layer (ABL). This paper presents an overview of the construction and solution of a computational fluid dynamics (CFD) model to replicate the development of the internal ventilation regime within a surface quarry excavation due to the presence of a neutral ABL above this excavation. This model was then used to study the dispersion and deposition of fugitive mineral dust particles generated during rock blasting operations. The paths of the mineral particles were modelled using Lagrangian particle tracking. Particles of four size fractions were released from five blast locations for eight different wind directions.The study concluded that dependent on the location of the bench blast within the quarry and the direction of the wind, a mass fraction of between 0.3 and 0.6 of the emitted mineral particles was retained within the quarry. The retention was largest when the distance from the blast location to the downwind pit boundary was greatest.
Keywords: Open pit; Quarry; Dust; Dispersion; Modelling;
Combining deterministic and statistical approaches for PM10 forecasting in Europe by I.B. Konovalov; M. Beekmann; F. Meleux; A. Dutot; G. Foret (6425-6434).
Well documented adverse health effects of airborne particulate matter (PM) stimulate intensive research aimed at understanding and forecasting its behaviour. Forecasting of PM levels is commonly performed with either statistical or deterministic chemistry-transport models (CTM). In this study, we investigate advantages of combining deterministic and statistical approaches for PM10 forecasting over Europe one day ahead. The proposed procedure involves statistical postprocessing of deterministic forecasts by using PM10 monitoring data. A series of experiments is performed using a state-of-the-art CTM (CHIMERE) and statistical models based on linear regressions. It is found that performance of both CTM simulations and “pure” statistical models is inferior to that of the combined models. In particular, the root mean squared error of the deterministic forecasts can be reduced, on the average, by up to 45 percent (specifically, from 12.8 to 6.9 μg/m3 at urban sites in summer) and the coefficient of determination can be almost doubled. Importantly, it is found that the combined models for rural sites in summer and for urban and suburban sites in both summer and winter are representative, on the average, not only for a given monitoring site used for their training, but also of territories of similar type of environment (rural, suburban or urban) within several hundreds of kilometers away.
Keywords: Particulate matter; Air quality; Statistical model; Neural network; Data assimilation; CTM;
Comparison of air pollutant emissions among mega-cities by David D. Parrish; William C. Kuster; Min Shao; Yoko Yokouchi; Yutaka Kondo; Paul D. Goldan; Joost A. de Gouw; Makoto Koike; Tomoko Shirai (6435-6441).
Ambient measurements of hydrocarbons, carbon monoxide and nitrogen oxides from three mega-cities (Beijing, Mexico City, Tokyo) are compared with similar measurements from US cities in the mid-1980s and the early 2000s. The common hydrocarbon pattern seen in all data sets suggests that emissions associated with gasoline-fueled vehicles dominate in all of these cities. This commonality suggests that it will be efficient and, ultimately, cost effective to proceed with vehicular emission controls in most emerging mega-cities, while proceeding with development of more locally appropriate air quality control strategies through emissions inventory development and ambient air monitoring. Over the three decades covered by the US data sets, the hydrocarbon emissions decreased by a significant factor (something like an order of magnitude), which is greater than suggested by emission inventories, particularly the EDGAR international inventory. The ambient hydrocarbon and CO concentrations reported for the three non-US mega-cities are higher than present US ambient concentrations, but lower than those observed in the 1980s in the US. The one exception to the preceding statement is the high concentrations of CO observed in Beijing, which apparently have a large regional contribution.
Keywords: Mega-city; Emissions; Carbon monoxide; Nitrogen oxides; NO x ; Hydrocarbons; VOC;
A biogenic volatile organic compound emission inventory for Hong Kong by Jeanie Kin-Yin Tsui; Alex Guenther; Wing-Kin Yip; Feng Chen (6442-6448).
Biogenic volatile organic compounds (BVOCs) in the atmosphere react to form ozone and secondary organic aerosols, which deteriorate air quality, affect human health, and indirectly influence global climate changes. The present study aims to provide a preliminary assessment of BVOC emissions in Hong Kong (HKSAR). Thriteen local tree species were measured for their isoprene emission potential. Tree distribution was estimated for country park areas based on field survey data. Plant emission data obtained from measurements and the literature, tree distribution estimation data, land use information, and meteorological data were combined to estimate annual BVOC emissions of 8.6×109 g C for Hong Kong. Isoprene, monoterpenes, and other VOCs contributed about 30%, 40%, and 30% of the estimated total annual emissions, respectively. Although hundreds of plant species are found in Hong Kong country parks, the model results indicate that only 10 tree species contribute about 76% of total annual VOC emissions. Prominent seasonal and diurnal variations in emissions were also predicted by the model. The present study lays a solid foundation for future local research, and results can be applied for studying BVOC emissions in nearby southern China and Asian regions that share similar climate and plant distributions.
Keywords: Hong Kong; BVOC; Isoprene; Monoterpenes; Emission modeling;
Inter-comparison of three instruments for measuring regional background carbon monoxide by Chang-Feng Ou Yang; Yu-Chi Lin; Neng-Huei Lin; Chung-Te Lee; Guey-Rong Sheu; Seak-Hong Kam; Jia-Lin Wang (6449-6453).
Three CO instruments, i.e., vacuum ultraviolet resonance fluorescence (VUV-RF), gas chromatography/reduction gas detection (GC/RGD), and non-dispersive infrared (NDIR) spectrometry, were inter-compared at a background site, i.e., Lulin Atmospheric Baseline Station (LABS) in central Taiwan. For a period of 18 days of continuous measurements, highly coherent results were observed between the three instruments. Calibration of the GC/RGD and VUV-RF was based on the same batch of CO standards, producing results that agreed within 4%. Nevertheless, NDIR displayed a significant bias with a large offset compared to the other two instruments (about −63.1 ppb), due mainly to its over-simplified calibration procedure. The NDIR bias was then removed by aligning the NDIR data to those of GC/RGD in a process termed “post-run correction”. Through this practice, the NDIR was linked to the same calibration scale as that of GC/RGD. As a result, by simultaneously exploiting both GC/RGD and NDIR to measure background CO, both time-resolution and accuracy can be secured.
Keywords: Inter-comparison; Gas chromatography/reduction gas detection (GC/RGD); Vacuum ultraviolet resonance fluorescence (VUV-RF); Non-dispersive infrared (NDIR);
Erratum to “Estimating the contribution of industrial facilities to annual PM10 concentrations at industrially influenced sites” [Atmos. Environ. 43 (2009) 4655–4665] by Dieter Gladtke; Wolfgang Volkhausen; Bastian Bach (6454).