Overview of Air Dispersion Modeling in the United States -Uses and Types of Models

摘要

Air pollutants are emitted into the atmosphere from a variety of sources including industrial activities, mobile sources such as automobiles, or accidental releases of hazardous materials. Estimates of the amount of pollutants in the ambient air are important for governments to know so they adequately protect air quality for the benefit of their citizens. As described by the United States Environmental Protection Agency (USEPA), atmospheric dispersion models use "mathematical formulations to characterize the atmospheric processes that disperse a pollutant emitted by a source."1 The USEPA's Air Quality Modeling Group lists four primary groups of dispersion models: 1. Preferred/Recommend Models - Those models listed in United States Code of Federal Regulations Title 40 Appendix W to Part 51 - Guideline on Air Quality Models (Appendix W) and required to be used as part of regulatory requirements such as New Source Review (NSR) and Prevention of Significant Deterioration (PSD). 2. Alternative Models - Those not listed in Appendix W but can be used with prior approval of the reviewing authority. 3. Screening Models - Used to determine whether refined modeling is required. 4. Photochemical Models - Used to simulate impacts of both inert and chemically reactive pollutants over large scales. The paper will take an in-depth look at the current state of air dispersion modeling in the United States. Models such as AERMOD, the preferred dispersion model for estimating near-field pollutant impacts; CALPUFF, another preferred model with an emphasis on long-range transport; mobile models such as CALINE4, CAL3QHC, and CAL3QHCR; alternative models, like SCIPUFF, that are increasing in their use; and more complex models will be reviewed.