Transcript ISCModel6
Introduction to the ISC Model
Marti Blad
NAU College of Engineering
Model Overview
The Industrial Source Complex (ISC)
model version 3--key regulatory model
developed by EPA
Gaussian plume model appropriate for
complex mixture of sources
Chemical reactions can only be treated in
rudimentary way, thus…
Model best applied to non-reactive pollutants
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Model Overview
Short-term and long-term versions of ISC3 model
Differ in averaging times available for data output
Short-term model also has more sophisticated capabilities for
estimating effects of terrain and deposition
ISC-PRIME
ISC-AERMOD
Plume Rise Model Enhancements
Based on more-sophisticated treatment of boundary layer
dynamics than possible with Gaussian plume model
GUI Courtesy of Lakes Environmental
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Applications
ISCST3 Model widely used by EPA, state and
local environmental agencies
Models effects of various pollution sources
Model can calculate average concentrations over time
periods of an hour to a year
Appropriate modeling uses include
Demonstrating sufficiency of proposed State Implementation
Plans (SIPs) for criteria air pollutants
Predicting air quality impact of new regulated sources
Supporting assessment of health impacts of air toxics
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History
Several revisions to model, each adding
new capabilities (without changing
Gaussian plume assumptions at heart of
model)
ISCST3 has new
Algorithms for wet and dry deposition
Way of simulating area sources
Method for simulating complex terrain
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How To Get the Model
Primary source for most up-to-date model
is EPA’s Support Center for Regulatory Air
Quality Models (SCRAM) website
www.epa.gov/ttn/scram
Site includes compiled, executable version
of model for running on Microsoft
Windows operating system
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How to Get the Model (cont.)
EPA version not particularly user-friendly
No graphical interface--everything done
with input/output files
More user-friendly interfaces designed by
several private vendors
To locate, Web search “ISCST3”
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ISC Model outline
Screens with multiple tabs for multiple inputs
Control Pathway
Source Pathway
Receptor Pathway
Meteorology Pathway
Terrain Grid Pathway
Output Pathway
See each piece now in detail
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Pathways in detail
Control Pathway
Dispersion options, specify pollutant,
averaging times, terrain height options
Source characteristics
Source type: point, volume, open pit
source release parameters
Variable emission rate: season, month, hour
Variables for deposition, settling & removal
Variable source groups: single, combined
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Pathways in detail (cont.)
Receptor Pathway
Network of gridded receptors
Cartesian & polar
Where to calculate concentrations
Specify discrete receptor location
Flagpole
Elevated receptors: terrain above stack base
Plant boundary distances
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Pathways in detail (cont.)
Meteorology
Specify met data input files
Station location and other indicators
Anemometer height
Wind speed categories
Wind profile exponents
Vertical temperature gradients
Data time period to process
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Pathways in detail (cont.)
Terrain Grid
Used to calculate dry depletion in elevated or
complex terrain
Output Pathway
Summary of high values by receptor
For each averaging period and source group
Overall maximum values
Find all occurrences over threshold value
Plot files
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Site Maps for Modeling
One degree DEMs
http://edcwww.cr.usgs.gov/glis/hyper/guide/1_dgr_
dem
7.5 degree DEMs
http://edcwww.cr.usgs.gov
Format notation
DXF. = autoCAD
DLG. = USGS digital line graph
LULC.= USGS land use and land coverage
BMP.= Bitmap images
SHP. = ArcView shapefiles
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Dispersion Coefficients
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Met Data Needed for the ISCST3
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Surface Roughness
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Noontime Albedo
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Albedo Values for Model Inputs
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Daytime Bowen Ratios by Land Use
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Parameters not Frequently Seen
Anthropogenic heat flux
Surface heating caused by humans
Rural = 0.0 Watts/m2
Urban (large) = 20 Watts/m2
Rammet View has many inside program
Fraction of net radiation absorbed @ ground
Rural = 0.15
Urban = 0.27
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Other Dispersion Models
Models-3 CMAQ
Will provide more advanced chemistry for reactive
pollutants
Plume within grid to more realistically simulate
dispersion at multiple scales
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