Chemical Mass Balance Receptor Modelling

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Chemical Mass Balance Receptor Modelling
Source 1xi1 i1,n
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Receptoryi i1,n
1
Source 3xi3 i1,n
2
Source 2xi2 i1,n
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Chemical Mass Balance Receptor Modelling

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Chemical Mass Balance Receptor Modelling

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Components

• PM
• metals
• ions
• PAH
• OC/EC
• etc.
• Gas phase
• various organic cpds
• VOCs
• etc.

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Chemical Mass Balance Receptor Modelling Simple
Spreadsheet Implementation

• Electronic spreadsheets like Excel make it easy
  to implement the model in the above form.
• The Solver function in Excel enables the
  minimization operation.
• Graphical tools in Excel enable qualitative
  assessment of model fit and the inputs.

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Chemical Mass Balance Receptor Modelling U.S.
EPAs CMB Model

• There are uncertainties associated with both the
  receptor and source profiles. The measured
  quantities are thus
• The model results then also have uncertainties
  associated with them

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U.S. EPAs CMB Model The effective variance
method

• The CMB model uses an effective variance which
  looks at variances in both the receptor, and
  source profiles weighted by the source
  contributions

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U.S. EPAs CMB8

• The CMB model incorporates the statistics to
  improve our estimate of the source contributions
  by weighting the source and receptor profiles
  according to the uncertainties associated with
  them.
• It also reports the uncertainties associated with
  the source contribution estimates and goodness
  of fit parameters.
• Version 8 is windows based, more user friendly.
• Example Source apportionment for motor vehicle
  related VOCs in micro-environments

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VOC's Associated with Motor Vehicles
Exhaust EmissionsEvaporative Emissions
C1 - C10 RangeAlkanesAlkenesAlkynesCycloalkane
sAromatics
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Chemical Mass Balance Receptor Modelling
Source profile characterization
Fuel
Whole gasoline
Headspace vapor
Individual vehicles
Exhaust emissions - UDDS
Evaporative emissions - SHED
Fleet emission characteristics
Tunnel studies Roadside measurements
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Source Profiles
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ERMD Source Profiles with 17 species
0.45
0.4
0.35
0.3
0.25
Fraction of total
0.2
0.15
0.1
6 GA
0.05
5 LPG
4 CNG
0
3 HOTST
2 COLDST
1 FUEL
Ethylene
Ethane
Propane
n-butane
n-pentane
benzene
3m-pentane
e-benzene
o-xylene
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Modelled Species Profile
3m-pentane m-cyclopentanebenzene
cyclohexane iso-octanen-heptane toluene
n-octane e-benzenemp-xylenen-nonane1,2,4-t
m-benzene
ethylene acetylene ethane propane
isobutane isobutylenen-butane 2m-butane
n-pentane 2,3-dm-butane 2m-pentane
Fitting species
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Nose-level Ambient Sampling Schedules
Slater Street Curbside 20 Weekdays in
August-September
2 Stations, 3 Sampling Sessions Morning
730-930Noon 1130-1330Afternoon
1530-1730 (Evening 2200 - 2400)

• 3 Underground Garages
• 12 Weekdays in December-January
• 2 Stations, 2 Sampling sessions in each garage
• A.M. 730 - 930
• P.M. 1500 - 1700

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