Air Dispersion Model Research Articles

An uncertainty analysis of air pollution externalities from road transport in Belgium in 2010

Although stricter standards for vehicles will reduce emissions to air significantly by 2010, a number of problems will remain, especially related to particulate concentrations in cities, ground-level ozone, and CO 2. To evaluate the impacts of new policy measures, tools need to be available that assess the potential benefits of these measures in terms of the vehicle fleet, fuel choice, modal choice, kilometers driven, emissions, and the impacts on public health and related external costs. The ExternE accounting framework offers the most up to date and comprehensive methodology to assess marginal external costs of energy-related pollutants. It combines emission models, air dispersion models at local and regional scales with dose–response functions and valuation rules. Vito has extended this accounting framework with data and models related to the future composition of the vehicle fleet and transportation demand to evaluate the impact of new policy proposals on air quality and aggregated (total) external costs by 2010. Special attention was given to uncertainty analysis. The uncertainty for more than 100 different parameters was combined in Monte Carlo simulations to assess the range of possible outcomes and the main drivers of these results. Although the impacts from emission standards and total fleet mileage look dominant at first, a number of other factors were found to be important as well. This includes the number of diesel vehicles, inspection and maintenance (high-emitter cars), use of air conditioning, and heavy duty transit traffic.

Health risk assessment of PCDD/F emissions from a hazardous and medical waste incinerator in Turkey

A multimedia risk assessment procedure was conducted to determine the fate and transport of polychlorinated dibenzo- p-dioxin and polychlorinated dibenzofuran (PCDD/F) emissions from the Izmit Hazardous and Medical Waste Incinerator (IZAYDAS) in Turkey and their potential health risks. Congener concentrations in ambient air and their deposition rates were determined by an air dispersion model (ISCST3). Their transfer to some plant groups and animal tissues was predicted by food chain modeling. Exposure scenarios were produced based on three receptor groups (urban, semiurban, and rural) and five subgroups determined according to ages. Daily intakes of PCDD/Fs via exposure pathways were determined based on three different emission scenarios for each group and subgroup. Estimated incremental PCDD/F doses caused by the incinerator emissions in central-tendency scenario were computed as between 2.31×10 −6 and 0.008 pg TEQ kg −1 bodyweight (bw) day −1 on average for all the receptors other than infants in all the settings, while the range was 3.01×10 −5–0.081 pg TEQ kg −1 bw day −1 for infants. Sensitivity analysis showed that the consumption of vegetal products and their locally grown fractions are the most significant parameters in the exposure to PCDD/Fs in the area.

COMMUNITY ASBESTOS EXPOSURE FROM A VERMICULITE PROCESSING FACILITY

ISEE-424 Purpose: From the 1930s until the 1980s, vermiculite ore contaminated with amphibole asbestos was shipped from Libby, Montana to over 60 locations across the U.S. and Canada for processing into finished vermiculite products. Asbestos exposure in Libby has been associated with adverse health effects among workers and community members. The purpose of this investigation is to determine the extent to which similar exposures and health effects have occurred in a dense urban community centered on a vermiculite processing facility that received and processed Libby ore for over 50 years. Methods: In the first phase of the investigation, all individuals who lived in the study area, or reported direct contact with the processing waste from 1938 through 2001 were eligible to participate. Residential property owners were identified through city property records. Current and former residents were identified during household visits and interviews, including deceased former residents interviewed by proxy. Interviews with over 6,000 participants were conducted to characterize frequency and duration of individual exposures via ambient air, non-occupational contact with waste materials, occupational exposure and family contact with workers. Ambient air exposure was estimated using residential history in proximity to the source, and air dispersion modeling. Smoking history and occupational history with asbestos were also collected. All properties were offered a visual inspection for processing waste contamination in surface soils during household visits. Results: Processing waste was transported and used widely by the community in driveways and gardens. Playing on piles of processing waste at the facility exposed neighborhood children. Study staff and EPA inspectors discovered visible asbestos contamination on over 260 residential properties. The number and proportion of participants exposed through each exposure pathway and other descriptive characteristics of the population will be presented. Conclusion: Amphibole asbestos exposures among certain subgroups of an urban population living near a vermiculite processing facility were found to be similar to non-occupational exposures that occurred in Libby, Montana. Linkages with state and national morbidity and mortality data are planned to examine the occurrence of asbestos-related disease in the second phase of this investigation.

Case study of a potency‐weighted emission screen

AbstractAccording to the U.S. Environmental Protection Agency (USEPA) document entitled Risk Assessment Guidance for Superfund (RAGS) (EPA/540/1–89/002, U.S. Environmental Protection Agency, Office of Emergency and Remedial Response, Washington, DC, 1989), a concentration‐toxicity screen is one of the chemicals of potential concern (COPCs) selection processes that may be employed to reduce the number of chemicals carried through a human health risk assessment. COPCs are those constituents for which carcinogenic risks and noncarcinogenic hazards are estimated. This paper describes the results of an analogous approach to rank chemicals at a facility according to their emission rates and potency. The objective of our proposed COPC selection methodology was to consider the comprehensive list of chemicals used in normal operations at a facility with a large chemical inventory and to identify those chemicals that have the potential to contribute at least 90 to 95% of the estimated risk for the facility (i.e., the main risk drivers). By focusing our efforts on this shorter list of chemicals, we increased the accuracy of information obtained from facility personnel and improved the level of confidence in the emission estimation, air dispersion modeling, and risk assessment results. While this approach does not consider constituent transport from multiple facility sources or proximity of receptors to those sources, these effects were evaluated in the subsequent air dispersion modeling and risk assessment of facility emissions. An evaluation of the subsequent risk assessment analyses demonstrated that the potency‐weighted emissions screen was successful in determining the list of chemicals responsible for 90 to 95% of the estimated carcinogenic risks and noncarcinogenic hazards. © 2004 American Institute of Chemical Engineers Environ Prog, 23: 168–177, 2004

Modeling of methyl isothiocyanate air concentrations associated with community illnesses following a metam-sodium sprinkler application.

A series of illnesses occurred in Earlimart, CA on November 13, 1999 following a metam-sodium sprinkler application to a potato field on the southern edge of the town. Case information was obtained from direct interviews, from illness complaints filed with state or county agencies, or from illness reports filed by community physicians for 173 subjects. Air concentrations of the by-product methyl isothiocyanate (MITC) during the episode were estimated based upon the Industrial Source Complex Short-Term (ISC3) air dispersion model, estimates from prior metam-sodium monitoring studies, and data from weather stations in two adjoining communities. Weather station data indicated that the November 13th incident corresponded with a temperature inversion at approximately 5:00 p.m. and a shift in the direction of prevailing wind from northwest to southeast. On the edge of Earlimart, 1-hr time weighted average (TWA) MITC concentration estimates ranged from 0.5 to 1 ppm. Of the 173 subjects, 170 had MITC-compatible symptoms, including eye or upper respiratory irritation (77.6%), non-specific systemic symptoms (64.7%), and lower respiratory symptoms (20.0%). 78.2% were exposed within 0.5 miles of the northern edge of the treated field where average 1 hr MITC concentrations exceeded the 800 ppb ocular irritation threshold. ISC3 modeling is a useful means of evaluating MITC concentrations for illness episodes when industrial hygiene assessment is not possible.

Case study: Environmental monitoring using remote optical sensing (OP‐FTIR) technology at the Oklahoma City Air Logistics Center industrial wastewater treatment facility

AbstractDuring production and maintenance operations at Tinker Air Force Base in Oklahoma City, Oklahoma, industrial wastewater streams are generated that contain organic and heavy metal compounds. These waste streams result from chemical depainting operations, chemical cleaning processes, and electroplating operations. Processes discharging wastewater are treated at the on‐site industrial wastewater treatment facility (IWTF). Regulatory reporting mandates require identifying volatile organic compound emission sources, estimating emissions from the IWTF, quantifying ambient air concentrations surrounding the facility via air dispersion modeling, and evaluating computer‐generated numerical concentration estimates with respect to discontinuous field data and an open‐path optical remote monitoring system. The objective of this article is to compare three strategies for meeting air‐quality management requirements: (1) the use of a coupled model (air emission model and air dispersion model); (2) the use of air quality–monitoring data collected via discontinuous air sampling and analysis (i.e., periodic canister monitoring); and (3) the use of air‐quality data generated by open‐path optical remote monitoring using Fourier Transform Infrared Spectroscopy (OP‐FTIR). Validation of the predictive accuracy of the three strategies will be made based on (a) comparisons and statistical testing of receptor location predictions with air‐quality data from periodic canister monitoring; (b) comparisons and statistical testing of predictions along the open‐path optical remote monitoring boundary line with measured concentrations based on OP‐FTIR; and (c) comparisons and statistical testing of pertinent field canister monitoring data with open‐path monitoring results. © 2004 Wiley Periodicals, Inc.

Comparing Air Dispersion Model Predictions with Measured Concentrations of VOCs in Urban Communities

Air concentrations of nine volatile organic compounds were measured over 48-h periods at 23 locations in three communities in the Minneapolis-St. Paul metropolitan area. Concentrations at the same times and locations were modeled using a standard regulatory air dispersion model (ISCST3). The goal of the study was to evaluate model performance by comparing predictions with measurements using linear regression and estimates of bias. The modeling, done with mobile and area source emissions resolved to the census tract level and characterized as model area sources, represents an improvement over large-scale airtoxics modeling analyses done to date. Despite the resolved spatial scale, the model did not fully capture the spatial resolution in concentrations in an area with a sharp gradient in emissions. In a census tract with a major highway at one end of the tract (i.e., uneven distribution of emissions within the tract), model predictions atthe opposite end of the tract overestimated measured concentrations. This shortcoming was seen for pollutants emitted mainly by mobile sources (benzene, ethylbenzene, toluene, and xylenes). We suggest that major highways would be better characterized as line sources. The model also failed to fully capture the temporal variability in concentrations, which was expected since the emissions inventory comprised annual average values. Based on our evaluation metrics, model performance was best for pollutants emitted mainly from mobile sources and poorest for pollutants emitted mainlyfrom area sources. Important sources of error appeared to be the source characterization (especially location) and emissions quantification. We expect that enhancements in the emissions inventory would give the greatest improvement in results. As anticipated for a Gaussian plume model, performance was dramatically better when compared to measurements that were not matched in space or time. Despite the limitations of our analysis, we found thatthe regulatory air dispersion model was generally able to predict space and time matched 48-h average ambient concentrations of VOC species within a factor of 2 on average, results that meet regulatory model acceptance criteria.

Urban scale integrated assessment of options to reduce PM10 in London towards attainment of air quality objectives

Epidemiological studies have indicated that the fine fraction of airborne particulate matter (PM10) is harmful to human health. In order to explore what can be done to attain air quality objectives (AQO) in the London metropolitan area it is necessary to analyse and compare a range of options for reducing emissions from different environmental and economic perspectives. The dominant sources of PM10 in the urban environment today are from traffic; hence abatement strategies must include reduction of traffic emissions. The USIAM model has been developed and used to examine and rank a large number of different kinds of road source emission reduction strategies, and explore their resulting projected concentrations for 2005. Such analysis can aid in deciding which strategy is most cost efficient from both the perspective of attaining present and future AQOs, and of reducing population exposure to harmful PM10 concentrations. The model base case scenario for 1996 has been compared with measured PM10 concentrations in locations throughout the area of study, resulting in error estimates well within the typical ±10% to 50% error often quoted for this kind of air dispersion modelling. This work indicates that the most cost effective strategies from both perspectives analysed are those involving the use of alternative fuels, particularly switching diesel vehicles to LPG and/or CNG. The model also implies that measures involving road user charging appear to be less effective.

미세 격자 대기 확산 모델링을 통한 안산지역 PM10 고농도 사례 분석

미세 격자 대기 확산 모델링을 통한 안산지역 PM10 고농도 사례 분석

A Methodology to Estimate Odors around Landfill Sites: The Use of Methane as an Odor Index and Its Utility in Landfill Siting

The estimation of odor production and dispersion from landfill sites is a very complicated task because of the different chemical species that exist in biogas. To site a new landfill, it is necessary to know the distance that odors can travel around the landfill under atmospheric conditions that increase the concentration of pollutants. Although CH4 is an odorless gas, it can be used as an index to determine the dispersion of low-reactivity odorous species around a landfill site. Methane production rates, estimated by biogas production models, were used by an air dispersion model to determine the spatial distribution of CH4 around landfill sites. By utilizing dispersion models under extreme atmospheric conditions, a maximum CH4 concentration around the landfills was determined. Based on the ratio between CH4 and odorous chemical species, the spatial distribution of the concentration of an odorous species was determined for those species with low reactivity in the atmosphere. For odorous species with high reactivity in the atmosphere, a dispersion-reaction model must be used. In this way, the acceptable distance between new landfills and residential areas can be determined. The proposed methodology could be used as a design tool for those who are interested in landfill siting.

Long‐term SO2 dispersion modeling over a coastal region

Air dispersion modeling over coastal regions has proven to be a remarkable challenge in the field of air quality. Many conventional plume dispersion models, such as ISC2 and HYSPLIT, are unable to model such dispersion with the precision that is necessary to accurately predict ground‐level concentrations in coastal areas. Considering this, the present work was carried out with two primary objectives: i) to evaluate the effectiveness of currently available mathematical models in predicting plume dispersion over a coastal region and ii) to study the impact of sulfur dioxide emissions from a petroleum refinery over a different community located in the adjacent area. This study demonstrates that CALPUFF predictions are more reliable compared to those of the other models studied, however the operation of CALPUFF is highly data intensive and in many instances, it is difficult to obtain all required input data. This is a particular problem for regions outside of the United States of America where sufficient data is difficult to obtain. In addition, the study concluded that the predicted annual average SO2 concentrations in the nearby communities are well within regulatory limits

Air dispersion modeling: A tool for environmental evaluation and improvement

Air dispersion modeling: A tool for environmental evaluation and improvement

Interactions of Pathogens and Irritant Chemicals in Land-Applied Sewage Sludges (Biosolids)

Fertilization of land with processed sewage sludges, which often contain low levels of pathogens, endotoxins, and trace amounts of industrial and household chemicals, has become common practice in Western Europe, the United States, and Canada. Local governments, however, are increasingly restricting or banning the practice in response to residents reporting adverse health effects. These self-reported illnesses have not been studied and methods for assessing exposures of residential communities to contaminants from processed sewage sludges need to be developed. To describe and document adverse effects reported by residents, 48 individuals at ten sites in the United States and Canada were questioned about their environmental exposures and symptoms. Information was obtained on five additional cases where an outbreak of staphylococcal infections occurred near a land application site in Robesonia, Pennsylvania. Medical records were reviewed in cases involving hospitalization or other medical treatment. Since most complaints were associated with airborne contaminants, an air dispersion model was used as a means for potentially ruling out exposure to sludge as the cause of adverse effects. Affected residents lived within approximately 1 km of land-application sites and generally complained of irritation (e.g., skin rashes and burning of the eyes, throat, and lungs) after exposure to winds blowing from treated fields. A prevalence of Staphylococcus aureus infections of the skin and respiratory tract was found. Approximately one in four of 54 individuals were infected, including two mortalities (septicemia, pneumonia). This result was consistent with the prevalence of S. aureus infections accompanying diaper rashes in which the organism, which is occasionally found in the lower human colon, tends to invade irritated or inflamed tissue. When assessing public health risks from applying sewage sludges in residential areas, potential interactions of chemical contaminants with low levels of pathogens should be considered. An increased risk of infection may occur when allergic and non-allergic reactions to endotoxins and other chemical components irritate skin and mucous membranes and thereby compromise normal barriers to infection.

Atmospheric methane transport near landfill sites.

Methane production rates that have been estimated by a biogas production model (MICROGEN) are combined with an air dispersion model in order to determine the spatial distribution of methane around landfill sites. By utilising dispersion models under extreme atmospheric conditions, a maximum methane concentration around the landfills can be determined. The factors that enhance the maximum methane concentrations, using the meteorological model CALMET in conjunction with the dispersion model CALPUFF, are found to be the wind speed and the percentage of cloud cover. The rates of temperature and pressure variation, as well as the land use category seem to have no effect on the maximum methane concentrations. A rapid reduction of methane concentration is observed a few metres away from the landfill centre while a slower reduction is observed at distances greater than 300 m from it. The performance of this methodology is evaluated by comparing measured concentrations with model predictions.

Interactions of pathogens and irritant chemicals in land-applied sewage sludges (biosolids).

BackgroundFertilisation of land with processed sewage sludges, which often contain low levels of pathogens, endotoxins, and trace amounts of industrial and household chemicals, has become common practice in Western Europe, the US, and Canada. Local governments, however, are increasingly restricting or banning the practice in response to residents reporting adverse health effects. These self-reported illnesses have not been studied and methods for assessing exposures of residential communities to contaminants from processed sewage sludges need to be developed.MethodsTo describe and document adverse effects reported by residents, 48 individuals at ten sites in the US and Canada were questioned about their environmental exposures and symptoms. Information was obtained on five additional cases where an outbreak of staphylococcal infections occurred near a land application site in Robesonia, PA. Medical records were reviewed in cases involving hospitalisation or other medical treatment. Since most complaints were associated with airborne contaminants, an air dispersion model was used as a means for potentially ruling out exposure to sludge as the cause of adverse effects.ResultsAffected residents lived within approximately 1 km of land application sites and generally complained of irritation (e.g., skin rashes and burning of the eyes, throat, and lungs) after exposure to winds blowing from treated fields. A prevalence of Staphylococcus aureus infections of the skin and respiratory tract was found. Approximately 1 in 4 of 54 individuals were infected, including 2 mortalities (septicaemia, pneumonia). This result was consistent with the prevalence of S. aureus infections accompanying diaper rashes in which the organism, which is commonly found in the lower human colon, tends to invade irritated or inflamed tissue.ConclusionsWhen assessing public health risks from applying sewage sludges in residential areas, potential interactions of chemical contaminants with low levels of pathogens should be considered. An increased risk of infection may occur when allergic and non-allergic reactions to endotoxins and other chemical components irritate skin and mucus membranes and thereby compromise normal barriers to infection.

Reformulated and alternative fuels: modeled impacts on regional air quality with special emphasis on surface ozone concentration.

The comprehensive European Air Pollution and Dispersion model system was used to estimate the impacts of the usage of reformulated and alternative fuels on regional air quality with special emphasis on surface ozone concentrations. A severe western European summer smog episode in July 1994 has been used as a reference, and the model predictions have been evaluated for this episode. A forecast simulation for the year 2005 (TREND) has been performed, including the future emission development based on the current legislation and technologies available. The results of the scenario TREND are used as a baseline for the other 2005 fuel scenarios, including fuel reformulation, fuel sulfur content, and compressed natural gas (CNG) as an alternative fuel. Compared to the year 1994, significant reductions in episode peak ozone concentrations and ozone grid hours are predicted for the TREND scenario. These reductions are even more pronounced within the investigated alternative and reformulated fuel scenarios. Especially, low sulfur fuels are appropriate for an immediate improvement in air quality, because they effect the emissions of the whole fleet. Furthermore, the simulation results indicate that the introduction of CNG vehicles would also enhance air quality with respect to ozone.

Uncertainty analysis in air dispersion modeling

The Taylor series approach for uncertainty analyses is advanced as an efficient method of producing a probabilistic output from air dispersion models. A probabilistic estimate helps in making better-informed decisions when compared to results of deterministic models. In this work, the Industrial Source Complex Short Term (ISCST) model is used as an analytical model to predict pollutant transport from a point source. First- and second-order Taylor series approximations are used to calculate the uncertainty in ground level concentrations of ISCST calculations. The results of the combined ISCST and uncertainty calculations are then validated with traditional Monte Carlo (MC) simulations. The Taylor series uncertainty estimates are a function of the variance in input parameters (wind speed and temperature) and the model sensitivities to input parameters. While the input variance is spatially invariant, sensitivity is spatially variable; hence the uncertainty in modeled output varies spatially. A comparison with the MC approach shows that uncertainty estimated by first-order Taylor series is found to be appropriate for ambient temperature, while second-order Taylor series is observed to be more accurate for wind speed. Since the Taylor series approach is simple and time-efficient compared to the MC method, it provides an attractive alternative.

Five epidemiological studies on transport and asthma: objectives, design and descriptive results.

A case-control study was conducted in five French metropolitan areas in order to assess the role of traffic-related air pollution in the occurrence of childhood asthma. This paper presents the study design and describes the distribution of key exposure variables. A set of 217 pairs of matched 4- to 14-year-old cases and controls were investigated (matching criteria: city, age, and gender). Current and past environmental smoke exposures, indoor allergens or air pollution sources, and personal and family atopy were assessed by standard questionnaires. When possible, direct measurements were done to check the validity of this information, on current data: skin prick tests, urine cotinine, house dust mites densities, personal exposures to, and home indoor concentrations of NO(x) and PM(2.5). Cumulative exposure to traffic-related pollutants was estimated through two indices: "traffic density" refers to a time-weighted average of the traffic density-to-road distance ratio for all home and school addresses of each child's life; "air pollution" index combines lifelong time-activity patterns and ambient air concentration estimates of NO(x), using an air dispersion model of traffic exhausts. Average current PM(2.5) personal exposure is 23.8 microg/m3 (SD=17.4), and average indoor concentrations=22.5 microg/m3 (18.2); corresponding values for NO(2) are 31.4 (13.9) and 36.1 (21.4) microg/m3. Average lifelong calculated exposures to traffic-related NO(x) emissions are 62.6 microg/m3 (43.1). The five cities show important contrasts of exposure to traffic pollutants. These data will allow comparison of lifelong exposures to indicators of traffic exhausts between cases and controls, including during early ages, while controlling for a host of known enhancers or precipitators of airway chronic inflammation and for possible confounders.

ASSOCIATIONS OF POLYCYCLIC ORGANIC MATTER IN OUTDOOR AIR WITH DECREASED BIRTH WEIGHT: A PILOT CROSS-SECTIONAL ANALYSIS

The association between births that are small for gestational age and outdoor airborne polycyclic organic matter (POM) was examined in New Jersey, a highly urban state. This pilot study utilizes a cross-sectional investigation combining maternal and pregnancy outcome information from birth certificates with air toxics data from the U.S. Environmental Protection Agency Cumulative Exposure Project and census data at the census tract level. The exposure categories were based on tertiles of modeled average POM concentrations for each census tract in New Jersey. High POM exposure was positively associated with delivery of "small for gestational age" (SGA) births. After adjustment for potential individual-level confounding factors, the odds ratios for term, preterm, and all SGA were 1.22 (1.16-1.27), 1.26 (1.07-1.49), and 1.22 (1.17-1.27), respectively, for the highest exposure tertile in the urban population of the state (89% of the state's birth population). For group-level variables, the corresponding ORs were 1.12 (1.07-1.18), 1.23 (1.02-1.47), and 1.13 (1.07-1.18). The results of this study suggest that residential exposure to airborne polycyclic organic matter (POM) is associated with increased prevalence of "small for gestational age" births among urban population. Cross-sectional investigations combining air dispersion models with routinely collected population-based health and census data could be a useful approach for identifying the hazardous air pollutants of greatest public health concern.

What are the areas for further research?

The introduction of a national standard on odour measurement presents a new challenge for Australian olfactometry laboratories to meet tough new instrumental performance and panellist performance criteria. It also raises issues for end users of olfactometry results. For examples regulatory authorities may need to review the current status of odour regulations and guidelines. The paper reviews major issues pertaining to four components in odour impact assessment: measurement of odour, sampling techniques, air dispersion modelling, and the development of assessment criteria. The paper identifies and discusses the resolution of issues that could have a significant effect on the outcomes of odour impact assessment. It is hoped that the paper will provide a useful guide for industry and environmental protection authorities in the further development of an odour impact assessment procedure.