2.0 EMISSION CHARACTERIZATION
Atmospheric releases of
pollutants may occur by a number of mechanisms such as volatilization,
suspension, leakage, and direct emission. These releases may be characterized
as being from either area sources (e.g., surface contamination, landfills,
lagoons) or point sources (e.g., stacks, vents).
The emission formulations
in this document refer to MEPAS Version 3.1 which limits the total emissions
to the air based on a contaminant mass budget for the air emissions. This
report does not specifically address the MEPAS multimedia source term component.(a)
The MEPAS atmospheric component
supports several methods for defining atmospheric release rates:
· For both point sources and area sources the investigator may input the release rate of contaminants.
· For area sources, the investigator may input site characteristics and have MEPAS compute the pollutant release
rates associated with the suspension of particulates and emission of gases
(volatilization).
· For both point and area sources, the investigator may use long-term environmental monitoring data to back-calculate
an apparent pollutant release rate.
The release of contaminants
into the atmosphere is often a function of local conditions. Important
factors can be temperature, moisture, wind speed, surface characteristics
(e.g., crust formation, roughness, vegetation cover), the physical state
and chemical form of the contaminant (e.g., gas or particulate, reactive
or nonreactive), and location of the contaminant (i.e., on the surface,
buried under a soil layer, in a tank). The formulations for computing pollutant
release rates from site characteristics are described in this chapter.
(a) The multimedia source term component is
being developed at the time of pre-paration of this report. This
new component combines source compu-ta-tions of emissions to water, soil,
and air to compute an integrated time-dependent mass budget. A separate
document will be issued with the multimedia source term component formulations.