Air : air
The FRAMES atmospheric component for air media includes models for emission from a source to the air, initial plume rise and dispersion, airborne pollutant transport and dispersion, and deposition to soils and crops.
The atmospheric component uses a series of climatological models for modeling the releases from point and area sources. In FRAMES, emission estimation models are provided as an alternative method for cases where the emission rates are unknown or cannot be back-calculated from environmental monitoring data. FRAMES has seven volatilization models for estimating gaseous vapor emissions from various types of sources and a particle suspension model for estimating soil-bound pollutant emissions. Plume rise models are included for stack releases. A sector-average Gaussian model using standard dispersion rates is used for the atmospheric transport. Both wet and dry deposition are computed. An important enhancement is that the wind speed, dispersion, and deposition models account for the influence of local surface roughness. This feature allows the model to account for local roughness influences along a wind trajectory ranging from smooth over-water to rough forest cover. A complex-terrain nocturnal flow option allows for the near-source channeling of airborne releases. The major products from these atmospheric component models include 1) constituent emission rates, 2) regional patterns of long-term air concentrations and deposition rates normalized by emission rates, 3) near-release short-term acute air concentrations normalized by emission rates, 4) long-term deposition rates for selected types of surfaces, and 5) regional patterns of ambient pollutant concentrations. These output products from the atmospheric component are linked as input to other components as part of the integrated exposure and impact evaluation software.
The atmospheric pathway component estimates the pollutant exposures from atmospheric emissions to a regional human population. Long-term, average constituent levels are computed using standard computation techniques for locations defined in terms of a direction and distance from the site. Using these methods, estimates of constituent levels for exposure assessment can be made for both population centers and less populated rural areas. Short-term normalized air concentrations are provided for evaluation of acute exposures at nearby locations.
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