The ISC (Industrial Source Complex) Model
We have implemented two gaussian models derived from the USEPA (US Environmental Protection Agency). These are a short-term model for specific episode analysis and a long-term model for the analysis of several months periods, represented by frequency distributions of wind direction for classes of wind velocity and atmospheric stability. The model only runs if at least one areal or point source have been found in the actual site. The surrounding area is shown, as well as the sources, depending on their size of emission of the selected substance. A histogram is also shown with the distribution of the different pollutant concentration.
The ISC is a multiple point sources model developed by the USEPA. This is a gaussian plume model that can describe individual episodes of a few hours or long-term distribution, for example in average annual conditions. A basic assumption of the gaussian model is that of stable conditions ; i.e., the emissions as atmospheric conditions in terms of wind speed and direction, air temperature, stability class, mixing height and precipitation are assumed constant.
The Industrial Source Complex (ISC) Short Term model provides options to model emissions from a wide range of sources that might be present at a typical industrial source complex. The basis of the model is the straight-line, steady-state Gaussian plume equation, which is used with some modifications to model simple point source emissions from stacks, emissions from stacks that experience the effects of aerodynamic downwash due to nearby buildings, isolated vents, multiple vents, storage piles, conveyor belts, and the like. Emission sources are categorized into four basic types of sources, i.e., point sources, volume sources, area sources, and open pit sources. The volume source option and the area source option may also be used to simulate line sources. This model can be applied to plain terrains. With some modifications, it can be applied to complex terrains.
The ISC Short Term model accepts hourly meteorological data records
to define the conditions for plume rise, transport, diffusion, and deposition.
The model estimates the concentration or deposition value for each source
and receptor combination for each hour of input meteorology, and calculates
user-selected short-term averages. For deposition values, either
the dry deposition flux, the wet deposition flux, or the total deposition
flux may be estimated. The total deposition flux is simply the sum
of the dry and wet deposition fluxes at a particular receptor location.
The user also has the option of selecting averages for the entire period
of input meteorology.