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Human Health Risk Assessment Protocol
Chapter 3: Air Dispersion and Deposition Modeling
September 2005
The following is an example of the particle liquid (rain) and frozen (sleet or snow) scavenging
coefficients input in the SOurce pathway for 9 mean particle size diameters, assuming particles are
scavenged by frozen precipitation at 1/3 the rate of liquid precipitation:
SO PARTSLIQ STACK1 7E-5 5E-5 6E-5 1.3E-4 2.6E-4 3.9E-4 5.2E-4 6.7E-4 6.7E-4
SO PARTSICE STACK1 2E-5 2E-5 2E-5
4E-5
9E-5 1.3E-4 1.7E-4 2.2E-4 2.2E-4
The complete SOurce pathway for the example particle phase input file is as follows:
SO
SO
SO
SO
SO
SO
SO
SO
SO
SO
SO
SO
SO
SO
SO
SO
SO
SO
SO
SO
STARTING
LOCATION
SRCPARAM
BUILDHGT
BUILDHGT
BUILDHGT
BUILDHGT
BUILDHGT
BUILDWID
BUILDWID
BUILDWID
BUILDWID
BUILDWID
PARTDIAM
MASSFRAX
PARTDENS
PARTSLIQ
PARTSICE
SRCGROUP
FINISHED
STACK1
STACK1
STACK1
STACK1
STACK1
STACK1
STACK1
STACK1
STACK1
STACK1
STACK1
STACK1
STACK1
STACK1
STACK1
STACK1
STACK1
ALL
POINT 637524. 4567789. 347.
1.0 23.0 447.0 14.7 1.9
18.29 18.29 18.29 18.29 18.29 18.29 18.29 18.29
18.29 18.29 18.29 18.29 18.29 18.29 18.29 18.29
18.29 18.29 18.29 18.29 18.29 18.29 18.29 18.29
18.29 18.29 18.29 18.29 18.29 18.29 18.29 18.29
18.29 18.29 18.29 18.29
14.02 15.51 16.53 17.05 17.05 16.53 15.51 14.03
12.10 14.02 15.51 16.53 17.05 17.05 16.53 15.51
14.02 12.10 14.02 15.51 16.53 17.05 17.05 16.53
15.51 14.02 12.10 14.02 15.51 16.53 17.05 17.05
16.53 15.51 14.02 12.10
0.35 0.70 1.10 2.00 3.60 5.50 8.10 12.5 15.0
0.22 0.08 0.08 0.11 0.10 0.07 0.10 0.11 0.13
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
7E-5 5E-5 6E-5 1.3E-4 2.6E-4 3.9E-4 5.2E-4 6.7E-4 6.7E-4
2E-5 2E-5 2E-5
4E-5
9E-5 1.3E-4 1.7E-4 2.2E-4 2.2E-4
When modeling air vapors using ISCST3, the following is an example of the SOurce pathway input for
wet vapor scavenging coefficients that replaces the PARTDIAM, MASSFRAX, PARTDENS,
PARTSLIQ and PARTSICE lines in the above example:
SO GAS-SCAV STACK1 LIQ 1.7E-4
SO GAS-SCAV STACK1 ICE 0.6E-4
3.6.3
REceptor Pathway
The REceptor pathway identifies sets or arrays of receptor grid nodes (identified by UTM coordinates)
for which ISCST3 generates estimates of air parameters including:
•
air concentration,
•
dry and wet deposition, and
•
total deposition.
U.S. EPA Region 6
Multimedia Planning and Permitting Division
Center for Combustion Science and Engineering
U.S. EPA
Office of Solid Waste
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