Recent Advances in Photochemical Air Quality Modeling Using the CAMx Model: Current Update and Ozone Modeling of Point Source Impacts

摘要

The Comprehensive Air-quality Model with extensions (CAMx) is a publicly available photochemical grid model originally developed in the late 1990s to treat urban and regional ozone issues. With its first applications as part of the Ozone Transport Assessment Group (OTAG) process, it has undergone continuous development and refinements. Because it consists of all new computer coding in a modular framework, it is ideally suited for extension to other air quality issues. Recent advances in CAMx include: Implementation of "Probing Tools": A series of probing tools have been implemented in CAMx to obtain information on ozone source-receptor relationships, VOC versus NOx sensitivities, source apportionment, and to extract information on ozone formation processes. The probing tools implemented in CAMx include: Ozone Source Apportionment Technology (OSAT); Decoupled Direct Method (DDM); and Process Analysis (PA). Treatment of Particulate Matter: State of the Science aerosol modules have been implemented in CAMx to treat particulate matter (PM) and visibility issues, including aerosol thermodynamics, aqueous-phase chemistry, secondary organic aerosol, and a sectional approach to treat PM size distributions. Treatment of Air Toxics: Air toxics modules have been implemented in CAMx to treat both chemically reactive (e.g., benzene, 1,3-butadiene, formaldehyde, and acetaldehyde) and inert (e.g., chromium and diesel particulate) air toxics. A subgrid-scale plume module has also been implemented to treat the near source (fence line) impacts of air toxics from point sources. Advanced Treatment of Point Source Ozone Impacts: CAMx has an all new fiexi-nesting feature that allows the specification of nested fine grids with or without providing the fine grid inputs. This treatment is ideal for resolving the ozone impacts of point sources.