Ground-level Pollutant Concentrations Research Articles

Dispersion of gas flaring emissions in the Niger delta: Impact of prevailing meteorological conditions and flare characteristics

An understanding of the dispersion and level of emissions source of atmospheric pollutants; whether point, area or volume sources, is required to inform policies on air pollution and day-to-day predictions of pollution level. Very few studies have carried out simulations of the dispersion pattern and ground-level concentration of pollutants emitted from real-world gas flares. The limited availability of official data on gas flares from the oil and gas industries makes accurate dispersion calculations difficult. Using ADMS 5 and AERMOD, this study assessed the sensitivity of dispersion and ground-level concentration of pollutants from gas flares in the Niger Delta to prevailing meteorological condition; fuel composition; and flare size. Although, during the non-WAM (West African Monsoon) months (November and March), the simulated ground-level concentrations of pollutants from a single flare are lower, the dispersion of pollutants is towards both the inland and coastal communities. In the WAM months, the ground-level concentrations are higher and are dispersed predominantly over the inland communities. Less buoyant plumes from smaller flares (lower volume flow rates) and/or flaring of fuel with lower heat content results in higher ground-level concentrations in areas closer to the flare. Considering the huge number of flares scattered around the region, a mitigation of the acute local pollution level would be to combine short stacks flaring at lower volume flow rates to enhance the volume flow rate of a single exhaust, and hence, the buoyancy of the plume exiting the stack.

An Evaluation of MODIS-Retrieved Aerosol Optical Depth over AERONET Sites in Alaska

The air quality monitoring network in Alaska is currently limited to ground-based observations in urban areas and national parks, leaving a large proportion of the state unmonitored. The use of Moderate Resolution Imaging Spectroradiometer MODIS aerosol optical depth (AOD) to estimate ground-level particulate pollution concentrations has been successfully demonstrated around the world and could potentially be used in Alaska. In this work, MODIS AOD measurements at 550 nm were validated against AOD derived from two ground-based Aerosol Robotic Network (AERONET) sunphotometers in Alaska, located at Utqiagvik (previously known as Barrow) and Bonanza Creek, to determine if MODIS AOD from the Terra and Aqua satellites could be used to estimate ground-level particulate pollution concentrations. The MODIS AOD was obtained from MODIS collection 6 using the dark target Land and Ocean algorithms from years 2000 to 2014. MODIS data could only be obtained between the months of April and October; therefore, it was only evaluated for those months. Individual and combined Terra and Aqua MODIS data were considered. The results showed that MODIS collection 6 products at 10-km resolution for Terra and Aqua combined are not valid over land but are valid over the ocean. Note that the individual Terra and Aqua MODIS collection 6 AOD products at 10-km resolution are valid over land individually but not when combined. Results also suggest the MODIS collection 6 AOD products at 3-km resolution are valid over land and ocean and perform better over land than the 10-km product. These findings indicate that MODIS collection 6 AOD products can be used quantitatively in air quality applications in Alaska during the summer months.

Modelling traffic-induced multicomponent ultrafine particles in urban street canyon compartments: Factors that inhibit mixing

This study implements a two-box model coupled with ultrafine particle (UFP) multicomponent microphysics for a compartmentalised street canyon. Canyon compartmentalisation can be described parsimoniously by three parameters relating to the features of the canyon and the atmospheric state outside the canyon, i.e. the heterogeneity coefficient, the vortex-to-vortex exchange velocity, and the box height ratio. The quasi-steady solutions for the two compartments represent a balance among emissions, microphysical aerosol dynamics (i.e. evaporation/condensation of semi-volatiles, SVOCs), and exchange processes, none of which is negligible. This coupled two-box model can capture significant contrasts in UFP number concentrations and a measure of the volatility of the multi-SVOC-particles in the lower and upper canyon. Modelled ground-level UFP number concentrations vary across nucleation, Aitken, and accumulation particle modes as well-defined monotonic functions of canyon compartmentalisation parameters. Compared with the two-box model, a classic one-box model (without canyon compartmentalisation) leads to underestimation of UFP number concentrations by several tens of percent typically. By quantifying the effects of canyon compartmentalisation, this study provides a framework for understanding how canyon geometry and the presence of street trees, street furniture, and architectural features interact with the large-scale atmospheric flow to determine ground-level pollutant concentrations.

Wind tunnel measurements of pollutant plume dispersion over hypothetical urban areas

Non-computational-fluid-dynamics (Non-CFD) solutions, such as Gaussian plume models, are commonly employed to predict ground-level pollutant concentrations because of their cost-effectiveness. Whilst, they should be applied with caution for pollutant plume dispersion over complicated urban morphology in view of their implicit limitation of empirically determined dispersion coefficients σz. Skin-friction coefficient cf, which is a measure of aerodynamic resistance induced by rough surfaces, is proposed to parameterize the dispersion coefficient over urban areas in isothermal conditions. Analytical derivation shows that σz is proportional to the newly proposed friction length scale Lf (= x1/2δ1/2cf1/4 where x and δ are the distance after pollutant source and the turbulent boundary layer thickness, respectively). Its functional form is verified by wind tunnel experiments for flows and tracer plume dispersion over hypothetical urban areas in the form of idealized street canyons of different building-height-to-street-width (aspect) ratios (ARs = 1/2, 1/4, 1/8 and 1/12). A ground-level, pollutant line source in crossflows is modeled by atomizing water vapor using ultrasonic. Ranges of turbulent boundary layer thickness (240 mm ≤ δ ≤ 285 mm) and skin-friction coefficient (8 × 10−3 ≤ cf ≤ 13 × 10−3) are tested. The tracer concentrations over rough surfaces exhibit the Gaussian distribution. A close correlation between σz and Lf is revealed (coefficient of determination R2 = 0.93), demonstrating the influence of drag on the transport processes. The analytical solution and wind tunnel results collectively suggest an improved parameterization of pollutant plume dispersion coefficient over rough surfaces, refining the practice of the air quality forecast in urban areas.

The influence of roadside solid and vegetation barriers on near-road air quality

The current study evaluates the influence of roadside solid and vegetation barriers on the near-road air quality. Reynolds Averaged Navier-Stokes (RANS) technique coupled with the k−ε realizable turbulence model is utilized to investigate the flow pattern and pollutant concentration. A scalar transport equation is solved for a tracer gas to represent the roadway pollutant emissions. In addition, a broad range of turbulent Schmidt numbers are tested to calibrate the scalar transport equation. Three main scenarios including flat terrain, solid barrier, and vegetative barrier are studied. To validate numerical methodology, predicted pollutant concentration is compared with published wind tunnel data. Results show that the solid barrier induces an updraft motion and lofts the vehicle emission plume. Therefore, the ground-level pollutant concentration decreases compared to the flat terrain. For the vegetation barrier, different sub-scenarios with different vegetation densities ranging from approximately flat terrain to nearly solid barrier are examined. Dense canopies act in a similar manner as a solid barrier and mitigate the pollutant concentration through vertical mixing. On the other hand, the high porosity vegetation barriers reduce the wind speed and lead to a higher pollutant concentration. As the vegetation density increases, i.e. the barrier porosity decreases, the recirculation zone behind the canopy becomes larger and moves toward the canopy. The dense plant canopy with LAD=3.33m−2m3 can improve the near-road air quality by 10% and high porosity canopy with LAD=1m−2m3 deteriorates near-road air quality by 15%. The results of this study can be implemented as green infrastructure design strategies by urban planners and forestry organizations.

Impacts of trace gaseous emission from fuelwood species on ground level air quality

ABSTRACTNigeria’s energy supply in the form of electricity has been erratic and unreliable in recent time that people now depend on their own power generation in order to meet demands. Thus majority of the populace have to depend on traditional fuelwood for cooking without knowing the impacts of air emissions from it. This study estimated the ground-level concentrations of the air pollutants emitted from the fuelwoods using the American Meteorological Society-Environmental Protection Agency Regulatory Model (AERMOD). The maximum 24 h averaging ground-level concentrations were 6.378–87.319, 1.546–75.164, 0.079–2.759, and 0–0.164 µg/m3, respectively for CO, HC, NO, and SO2. With this all stakeholders will be properly guided on the usage of fuelwood with minimal negative impact.

Managing Ambient Air Quality Using Ornamental Plants-An Alternative Approach

Air quality management involves the determination of the relative contribution of current or future source emissions at receptor sites to ground level pollutant concentrations coupled with implementation of effective management plan to reduce emission level. From the last few decades, urban air pollution has become an inevitable issue for its possible consequences on public health. In order to manage the ambient air quality, there are several methodologies with each having some specific advantages and constrains. Improvement of ambient air quality involves the basic approaches like emission reduction at source level, conversion of pollutants to a less damaging compounds and sequestration of pollutants. However, in order to manage the air quality, application of ornamental plants may be considered a well alternative approach. Although, it may not be imperative to consider plants as a sole alternative for urban ambient air quality management, but certainly it may useful to manage air quality for a small confined area, especially in case of indoor air. This paper reviews the possible application of ornamental plants, which may be trees, shrubs or herbs for its possible applications to regulate air quality. Some selective plant species has also been recommended based on its air pollution tolerance index.

Ground level concentration of some air pollutants from Nigeria thermal power plants

ABSTRACT Power sector in Nigeria is undergoing structural reforms aimed at improving and expanding the current generation capacity, using thermal power plants. Ground level concentrations of air pollutants emitted from natural gas-powered thermal power plants were estimated using the American Meteorological Society-Environmental Protection Agency Regulatory Model (AERMOD). The average 24-h ground level concentrations of CO, NO x , SO2, particulate matter (PM), and volatile organic compounds (VOCs) were 31.88–72.79; 61.33–104; 0.61–3.91; 0.21–1.52; and 0.19–1.09 µg/m3, respectively. There is need for continuous monitoring of ground level concentration of pollutants around the thermal power plants to guarantee the safety of the environment in the host communities.

Environmental Performance of Hypothetical Canadian Pre-Combustion Carbon Dioxide Capture Processes Using Life-Cycle Techniques

The methodology of life-cycle assessment was applied in order to evaluate the environmental performance of a hypothetical Saskatchewan lignite-fueled Integrated Gasification Combined Cycle (IGCC) electricity generation, with and without pre-combustion carbon dioxide (CO2) capture from a full life-cycle perspective. The emphasis here is placed on environmental performance associated with air contaminants of the comparison between IGCC systems (with and without CO2 capture) and a competing lignite pulverized coal-fired electricity generating station in order to reveal which technology offers the most positive environmental effects. Moreover, ambient air pollutant modeling was also conducted by using American Meteorological Society/Environmental Protection Agency Regulatory Model (AERMOD) air dispersion modeling to determine the ground-level concentration of pollutants emitted from four different electricity generating stations. This study assumes that all stations are located close to Estevan. The results showed a significant reduction in greenhouse gas (GHG) emissions and acidification potential by applying both post-combustion and pre-combustion CO2 capture processes. The GHG emissions were found to have reduced by 27%–86%, and IGCC systems were found to compare favorably to pulverized coal systems. However, in other environmental impact categories, there are multiple environmental trade-offs depending on the capture technology used. In the case of post-combustion capture, it was observed that the environmental impact category of eutrophication potential, summer smog, and ozone depletion increased due to the application of the CO2 capture process and the surface mining coal operation. IGCC systems, on the other hand, showed the same tendency as the conventional coal-fired electricity generation systems, but to a lesser degree. This is because the IGCC system is a cleaner technology that produces lower pollutant emission levels than the electricity generating station; thus, the benefits of capture are reduced on a comparative basis. The results from air dispersion analysis showed that the maximum ground-level concentrations of pollutants from all electricity generating stations are in compliance with all air quality standards, except for Co, Pb and Ni. The IGCC with capture revealed the lowest nitrogen dioxide (NO2) ground-level concentration compared to all other scenarios. Moreover, IGCC systems both with and without pre-combustion CO2 capture revealed no ground-level concentration of trace elements. This is because the IGCC system operates with an acid gas cleaning process that removes most of the trace contaminants from the syngas.

Decision analysis of multi-pollutant control strategy for coal-fired power plant in Malaysia

The promulgation of Environmental Quality (Clean Air) Regulations 2014 on emissions from coal-fired power plants in Malaysia has prompted power plant operators to adopt emission control strategy that complies with the new emission limits. Currently, various emission control strategies are available to achieve the desired emission level. Each strategy offers unique advantages and disadvantages, depending on the objective of emissions control, process nature, and constraints on the resources incurred. To address this challenge, a proper decision-making analysis needs to be performed. In this paper, a systematic decision analysis methodology is proposed to select the most effective multi-pollutant control strategy that is compatible for coal-fired power plants in Malaysia. The methodology includes: (1) identification of pollutant emission from the plant under study and comparison with the stipulated emission limits, (2) establishment of emission factors, (3) selection of multi-pollutant control strategy, (4) identification of emission reduction factor for the pollutants and control technologies of interest, (5) determination of emission level from the selected multi-pollutant control strategy, and (6) prediction of ground-level concentration of pollutants. The decision analysis methodology is applied to a real case study of coal-fired power plant in Malaysia, which also currently faces a dilemma to comply with the additional and more stringent emission limits stipulated in the Environmental Quality (Clean Air) Regulations 2014. The proposed method is applicable for both the process concept under the design phase as well as the existing process plant.

The Ecological Situation in the Russian Arctic Permafrost Zone

The paper describes innovative approaches to ensure environmental safety in the production of hydrocarbon material in a permafrost zone. Studies the anthropogenic environmental factors, climatic and geographical and geological conditions of Purovskiy district of Yamalo-Nenets Autonomous Area (YaNAO). We consider the chemical characteristics of wastewater discharged into surface water objects, polluting emissions into the atmosphere. The conclusions of the environmental situation in Purovskiy and Ustpurovsk-Tazovskiy permafrost areas. Calculate the concentration of pollutants in the control section of the water object and the maximum ground-level concentrations of pollutants in the atmospheric air. The conclusions about the exceeding the maximum permissible concentration (MPC) in the atmospheric air for solids, carbon monoxide, nitrogen dioxide. Was examined the climatic conditions of the Far North. Correlational analysis was performed between human factors and temperature conditions of the northern territories, as well as between the climate and natural features cryological and disturbed permafrost soils.

A Conceptual Approach on Downwind Optimization of Processes for Air Pollution Control

Control of air pollutant emissions is a mean to protect air quality. In most cases, this is realized by the imposition of specific emission standards, which usually are based on national and international experience. However, in areas with intense and dense polluting activities (e.g. industrial sites, trafficked roads) these horizontal measures will most probably fail to sustain local air quality. This is mainly because they do not consider the local transport mechanisms of pollutants from the source to the receptor. High local concentration levels might be the result of specific meteorological conditions, amplification owe to neighbour sources and deficient design of the air pollution control (APC) systems. Present work describes a conceptual and holistic approach based on the downwind optimisation, which takes into consideration also the transfer mechanisms that induce the ground level concentration of pollutants. This method can be used to design efficiently and dynamically control both the APC systems and the plant processes. Thus, local air quality can be sustained and protected in all cases and also achieve a significant reduction in capital and operational costs. Nevertheless, no cost-benefit analysis has been conducted here. The approach is also demonstrated in a comprehensive case study.

Spatially-varying surface roughness and ground-level air quality in an operational dispersion model

Urban form controls the overall aerodynamic roughness of a city, and hence plays a significant role in how air flow interacts with the urban landscape. This paper reports improved model performance resulting from the introduction of variable surface roughness in the operational air-quality model ADMS-Urban (v3.1). We then assess to what extent pollutant concentrations can be reduced solely through local reductions in roughness. The model results suggest that reducing surface roughness in a city centre can increase ground-level pollutant concentrations, both locally in the area of reduced roughness and downwind of that area. The unexpected simulation of increased ground-level pollutant concentrations implies that this type of modelling should be used with caution for urban planning and design studies looking at ventilation of pollution. We expect the results from this study to be relevant for all atmospheric dispersion models with urban-surface parameterisations based on roughness.

Estimating Exposure by Loose-Coupling an Air Dispersion Model and a Geospatial Information System

The regulation of air quality is important for ensuring the health of a population. Current air quality decision support systems are very useful if the user possesses sufficient data to operate them and the necessary expertise to interpret their results. In general, these systems suffer as a result of their excessive complexity. The present study describes the development of a scalable air quality decision support system using the CALPUFF air dispersion model and a Geospatial Information System (GIS). This system uses receptor level exposure modeling and outputs from CALPUFF to estimate the relative impacts on human populations from multiple air pollution sources by calculating intake, defined as the amount of pollution that is inhaled by a population and intake fraction, defined as the fraction of pollutant emitted by a pollution source that is inhaled by a population. Unlike ground level pollution concentration, intake and intake fraction consider receptors and offer a more valuable estimate of pollution exposure, especially when faced with limited input data. The system also leverages the inherent strength of GIS to improve accessibility of geospatial data by generating maps of ground level pollutant concentration, intake, and intake fraction using graduated color schemes. This enables any user to identify potentially hazardous pollution sources and prioritize decisions such as development, maintenance, and decommission.

Influence of building insulation on outdoor concentrations of regional air-pollutants

Abstract The effects of building insulation on ground-level concentration levels of air pollutants are considered. We have estimated regionally averaged reductions in energy consumption between 2005 and 2020 by comparing a business as usual with a very low energy building scenario for the EU-25. The corresponding reductions in air pollutant emissions were calculated using emission factors. Annual simulations with an air-quality model, where only the emission reductions due to insulation was accounted for, were compared for the scenarios, and statistically significant changes in ground-level mass concentration of main air pollutants were found. Emission reductions of up to 9% in particulate matter and 6.3% for sulphur dioxide were found in north-western Europe. Emission changes were negligible for volatile organic compounds, and carbon monoxide decreased by 0.6% over southern Europe while nitrogen oxides changed by up to 2.5% in the Baltic region. Seasonally and regionally averaged changes in ground-level mass concentrations showed that sulphur dioxide decreased by up to 6.2% and particulate matter by up to 3.6% in north-western Europe. Nitrogen oxide concentrations decreased by 1.7% in Poland and increases of up to 0.6% were found for ozone. Carbon monoxide changes were negligible throughout the modelling domain.

MATHEMATICAL MODEL FOR THE STUDY EFFECTS OF METEOROLOGICAL CONDITIONS ON DISPERSION OF POLLUTANTS IN AIR

The purpose of the present work was to investigate air quality that contained pollutant gases (SO2 , NO2 , CO) released from the thermal power plant as case study. Gaussian Plume Model and the computer program (visual basic 6) is used to calculate concentrations dispersion of gas pollutants at different meteorological conditions (wind speed, ambient temperature); maximum concentration values, downwind distance and required effective stack height estimation.
 A typical theoretical investigation of a case study concerning existing air pollution problems at an industrial area (4Km) downwind distance by using the computer program. The results showed that the concentration of SO2 (890 µg/m3) released from stack may is higher than the EPA standard. Also the optimum point of the ground level concentration of pollutants decreases with increasing effective stack height.

Mixed deterministic statistical modelling of regional ozone air pollution

We develop a physically motivated statistical model for regional ozone air pollution by separating the ground-level pollutant concentration field into three components, namely: transport, local production, and large-scale mean trend mostly dominated by emission rates. The model is novel in the field of environmental spatial statistics in that it is a combined deterministic-statistical model, which gives novel perspectives on the modeling of air pollution. The model is presented in a Bayesian hierarchical formalism, and explicitly accounts for advection of pollutants, using the advection equation. We apply the model to a specific case of regional ozone pollution – the Lower Fraser Valley of British Columbia, Canada. As a predictive tool, we demonstrate that the model outperforms existing, simpler statistical modelling approaches. Our study highlights the importance of simultaneously considering different aspects of air pollution as well as taking into account the physical bases that govern the processes of interest.

Modélisation de l’atténuation au sol de la concentration des émissions d’une centrale thermique diesel

A ground level diesel power plant pollutants mitigation modelA three steps environmental mitigation model is investigated as a way of controlling the emission rates of a 44 MW diesel electric power plant located in downtown Ouagadougou. First of all, an environmental audit finds it necessary to rehabilitate the plant in order to improve its performances. To be effective however, the upper limit of the plant fuel consumption should not exceed 229 g/kWh. Finally, dispersion diagrams are obtained from a simplified dispersion-advection submodel, capable of predicting the plant stack high for which, the ground level pollutant concentrations must compley with the ambient air quality standards. Thus, the results of this model may be utilized to control and regulate air pollution.

Modelling pollutants dispersion and plume rise from large hydrocarbon tank fires in neutrally stratified atmosphere

Petrochemical industries normally use storage tanks containing large amounts of flammable and hazardous substances. Therefore, the occurrence of a tank fire, such as the large industrial accident on 11th December 2005 at Buncefield Oil Storage Depots, is possible and usually leads to fire and explosions. Experience has shown that the continuous production of black smoke from these fires due to the toxic gases from the combustion process, presents a potential environmental and health problem that is difficult to assess. The goals of the present effort are to estimate the height of the smoke plume, the ground-level concentrations of the toxic pollutants (smoke, SO 2, CO, PAHs, VOCs) and to characterize risk zones by comparing the ground-level concentrations with existing safety limits. For the application of the numerical procedure developed, an external floating-roof tank has been selected with dimensions of 85 m diameter and 20 m height. Results are presented and discussed. It is concluded that for all scenarios considered, the ground-level concentrations of smoke, SO 2, CO, PAHs and VOCs do not exceed the safety limit of IDLH and there are no “death zones” due to the pollutant concentrations.

POLLUTANTS EMISSION AND DISPERSION FROM FLARES: A GAUSSIAN CASE – STUDY IN IRAQ

The aim of this research is to study the emission and dispersion of pollutants (HC, CO, NOx, SPM) from the elevated flares in three situations of South Gas Company for Liquefied Petroleum Gas (LPG) production in Al-Basrah Governorate in Iraq. These three situations are Khor Al-Zubair plant, North Al-Rumaila Plant, and Storage Complex. The number of flares in the situations are 5, 3, and 2 flares respectively. A mathematical model formulated in a computer program written in visual basic language was utilized in finding the ground level concentrations of pollutants HC, CO, NOx, and SPM emitted from the elevated flares of the three situations; the concentrations were found at selected sites inside and outside of each situation at different distances. The programmed model takes into consideration all the meteorological conditions (wind speed, wind direction, ambient temperature, and atmospheric stability) which may take place at the study region. The emission rates of the pollutants which are emitted from the elevated flares are found depending on the laboratory analysis of gas compositions send to the flares , also by utilizing the modern EPA methods for determination the emission rates. The results of research illustrate the meteorological cases which are more effect in causing the maximum ground level concentrations of pollutants especially the unstable atmospheric conditions and wind speed. On the other hand, the programmed model is utilized to find the concentrations of hydrocarbons (HC), propane (C3H8) , and butane (C4H10) which are released from flare column to the atmosphere in case of combustion failure of these gases, at areas adjacent to the situations of flares.