[PDF] Air Dispersion Modeling Of Particulate Matter From Ground Level Area Sources eBook

Author : Karl B. Schnelle
Publisher : McGraw Hill Professional
Page : 560 pages
File Size : 33,57 MB
Release : 2000
Category : Nature
ISBN : 9780070580596

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CD-ROM includes: Practice problems that reinforces and deepen understanding of modeling principles.

Author : Praneeth Nimmatoori
Publisher :
Page : 141 pages
File Size : 22,5 MB
Release : 2014
Category : Agricultural pollution
ISBN :

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The air quality near agricultural activities such as tilling, plowing, harvesting, and manure application is of main concern because they release fine particulate matter into the atmosphere. These releases are modeled as area-sources in the air quality modeling research. None of the currently available dispersion models relate and incorporate physical characteristics and meteorological conditions for modeling the dispersion and deposition of particulates emitting from such area-sources. This knowledge gap was addressed by developing the advanced analytical and numerical methods for modeling the dispersion of particulate matter. The development, application, and evaluation of new dispersion modeling methods are discussed in detail in this dissertation. In the analytical modeling, a ground-level area source analytical dispersion model known as particulate matter deposition - PMD was developed for predicting the concentrations of different particle sizes. Both the particle dynamics (particle physical characteristics) and meteorological conditions which have significant effect on the dispersion of particulates were related and incorporated in the PMD model using the formulations of particle gravitational settling and dry deposition velocities. The modeled particle size concentrations of the PMD model were evaluated statistically after applying it to particulates released from a biosolid applied agricultural field. The evaluation of the PMD model using the statistical criteria concluded effective and successful inclusion of dry deposition theory for modeling particulate matter concentrations. A comprehensive review of analytical area-source dispersion models, which do not account for dry deposition and treat pollutants as gases, was conducted and determined three models - the Shear, the Parker, and the Smith. A statistical evaluation of these dispersion models was conducted after applying them to two different field data sets and the statistical results concluded that the Shear model performed the best out of the three dispersion models. The algorithms of each dispersion model were analyzed and it was determined that the best performance of the Shear model was due to incorporation of a variation of wind speed and vertical eddy diffusivity (atmospheric turbulence) with the height above ground surface. A new methodology was developed using computational fluid dynamics (CFD) - FLUENT for the numerical dispersion modeling of particulate matter emitting from an area-source (biosolids applied agricultural field). The discrete phase model (Lagrangian -Eulerian approach) was used in combination with each of the four turbulence models: Standard ke (ke), Realizable ke (Rke), Standard k¿ (k¿), and Shear-stress transport k-¿ (SST) to predict particulate matter size concentrations for distances downwind of the agricultural field. In this modeling approach, particulates were simulated as discrete phase and air as continuous phase. The discrete phase model accounted for the effects of atmospheric turbulence and drag force which is dependent on particle physical characteristics (diameter, density, and velocity), gravitational velocity, and air viscosity for predicting the trajectories of particles. The modeled particulate matter concentrations were compared statistically with their corresponding field study observations to evaluate the performance of proposed CFD model using the four turbulence models. The statistical analysis concluded that among four turbulence models, the discrete phase model when used with Rke performed the best in predicting particulate matter concentrations for low (u 2 m/s) and medium (2

Author : Seth Daniel Contreras
Publisher :
Page : 130 pages
File Size : 13,40 MB
Release : 2015
Category :
ISBN : 9781321646078

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A large and growing body of literature associates proximity to major roadways with increased risk of many negative health outcomes and suggests that exposure to fine particulate matter may be a substantial factor. Directly emitted and non-reactive mobile source air pollutants such as directly emitted fine particulate matter can form large spatial concentration gradients along major roadways, in addition to causing significantly large temporal and seasonal variation in air pollutant concentrations within urban areas. Current modeling and regulatory approaches for minimizing exposure have limited spatial resolution and do not fully exploit the available data. The objective is to establish a methodology for quantifying fine particulate matter concentration gradients due to mobile source pollutants and to estimate the resulting population exposure at a regional scale. A novel air dispersion modeling framework is proposed using the Environmental Protection Agency's regulatory model AERMOD with data from a regional travel demand model that can produce a high resolution concentration surface for a considerably large metropolitan area; in our case, Los Angeles County, California. We find that PM2.5 concentrations are highest and most widespread during the morning and evening commutes, particularly during the winter months. This is likely caused by a combination of stable atmospheric conditions during the early morning and after sunset in the evening and higher traffic volumes during the morning and evening commutes. During the midday hours concentrations are at their lowest even though traffic volumes are still much higher than during the evening. This is likely the result of heating during the day time which leads to unstable atmospheric conditions that cause more vertical mixing and lateral dispersion, reducing ground level PM2.5 concentrations by transport and dilution. With respect to roadway centerlines, PM2.5 concentrations drop off quickly, reaching relatively low concentrations between 150m to 200m from the center line of high volume roads. However, during stable atmospheric conditions (e.g., nighttime & winter season) concentrations remain elevated at distances up to 1,000m from roadway centerlines. We will demonstrate the feasibility of our methodology and how integrating the dispersion modeling framework into the travel demand modeling process routinely performed when developing and analyzing regional transportation improvement initiatives can lead to more environmentally and financially sustainable transportation plans. Regional strategies that minimize exposure, rather than inventories, could be established, environmental justice concerns are easily identified, and projects likely to cause local pollution "hotspots" can be proactively screened out, saving time and money for the transportation agency.