Motor Vehicle Emissions and Chemical Transport Modelling

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Motor Vehicle Emissions and Chemical Transport
Modelling()

• Human Health Impacts of Motor Vehicle Emissions
• Direct impact of emissions
• Indirect impact through ground level ozone and
  secondary PM formation in the lower atmosphere
• Chemical Transport Modelling Models-3/CMAQ
  application to Lower Fraser River Valley
• Nested grid
• Meteorology
• Emissions
• Temporal allocation
• Spatial allocation
• Chemical speciation
• Model validation
• Model application
• () With slides fromDr. Jiangs presentations
  from previous years

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Figure 1.2 de Nevers

• NO, NO2, O3, and CO concentrations
• as a function of time of day in Los Angeles

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Chemistry of ground level ozone formation
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Common terminology

• VOC Volatile organic compounds, physically
  (volatility) based definition
• ROG reactive organic gases, VOCs which react
  to a significant extent in the atmosphere
• NMOG Non-methane organic gases
• NMHC Non-methane hydrocarbons

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GROUND-LEVEL OZONE

• In the absence of VOCs

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GROUND-LEVEL OZONE

• VOCs represent an alternative path for NO
  oxidation
• The OH radical plays an important role in this
  overall reaction
• NO2 can also react directly with OH
• Thus, adding NO2 can interfere with the first
  reaction above

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OXIDATION OF NO BY VOCs
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VOC - NOx competition for reaction with OH

• OH - NO2 generally faster than OH - VOC for an
  average urban air mix
• reaction rates become equal when VOC/NO2
  5.5

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VOC - NOx competition for reaction with OH

• If VOC/NO2 lt 5.5 reaction with NO2
  dominates
• Reaction with NO2 is a termination reaction
• removes OH radicals from the reaction pool,
  retarding O3 production
• Thus, decreasing NO2 leads to higher O3

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Figure D.1 de Nevers

• Calculated maximum afternoon O3 concentrations
  as a function of the morning NOx and VOC
  concentratiuons for the same air mass

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M. Walsh, FQS Workshop
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VOC/NOx ratio

• Low VOC/NOx can occur
• in city centers, e.g.
• O3 Slater street lt O3 Wurtemburg street
• in plumes downstream of strong NO sources
• Rural environments characterized by high
  VOC/NOx ratios, ozone production is NOx
  limited

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GROUND-LEVEL OZONE

• The EKMA results show
• At low NOx, high VOC, increasing NOx increases
  O3
• At low VOC, high NOx, increasing NOx decreases O3
• At constant NOx value, VOC reductions always help
• At constant VOC value, NOx reductions may
  increase or decrease O3

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Incremental Ozone reactivity

• Individual species have different reactivity.
• Function of ambient VOC/NOx ratio, hence
  different in different environments

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Maximum Incremental reactivity (MIR)

• Carters MIR a scenario derived by adjusting the
  NOx emissions in a base case scenario to yield
  the highest incremental reactivity of the base
  ROG (VOC) mixture

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SPECIATION OF VOC EMISSIONS

• VOC profiles of emissions from specific sources
  (activities) Mass fraction of each VOC in the
  total emissions from that source
• SPECIATE database has a compilation of profiles
• Useful in quantifying total ozone reactivities,
  human health risk

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Atmospheric chemistry in 3-D modelling

• Large number of chemical compounds and chemical
  reactions
• Not practical/useful to keep track of all
  individual compounds and reactions
• Idea
• Keep track of similar compounds lumped
  together, i.e. pseudo compounds
• Consider primarily the fastest reactions

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Atmospheric aerosolprocessessecondary PM
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Models-3/CMAQ Air Quality Modelling System
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CMAQ modelling domain
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3-D Grid
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MM5 wind field (m/s) at 1700 August 5
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MM5 temperature field (K),1700 August 5
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EMISSION FACTORS

• Amount of pollutant emitted per unit activity
• (mg HC) / (mile driven) (e.g.. From MOBILE6)
• (g NOx) / (kg coal fired)
• (g NOx) / (kJ heat released)
• Empirical, applicable for the specific activity
  i.e. heat released by burning a specific fuel
  with specific type of burners in a specific type
  of furnace.
• AP-42 has comprehensive compilation for many
  sources

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Emissions Processing

• SMOKE Sparse Matrix Operator Kernel Emissions
  modelling system
• BEIS Biogenic Emissions Inventory System
• Temporal allocation
• Spatial allocation
• Speciation

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1995 NET Point Source File Start Field Type Le
ngth Description ---------------------------------
------------------ 1 STID Int 2 State
Code 3 CYID Int 3 County Code 6 PLANTID Char 15
Plant Identification Code 21 POINTID Char 15 Poin
t Identification Code 36 STACKID Char 12 Stack
Identification Code 48 ORISID Char 6 DOE Plant
ID 54 BLRID Char 5 Boiler Identification
Code 59 SEGMENT Char 2 DOE ID 61 PLANT Char 40 P
lant Name 101 SCC Char 10 Source Classification
Code 111 STKHGT Real 4.0 Stack Height
(ft) 115 STKDIAM Real 6.2 Stack Diameter
(ft) 121 STKTEMP Real 4.0 Stack Gas Exit
Temperature (deg F) 125 STKFLOW Real 10.2 Stack
Gas Flow Rate (ft3/min) 135 STKVEL Real 9.2 Stack
Gas Exit Velocity (ft/sec) 144 BOILCAP Real 8.2
Design Capacity (mmBtu/hr) 152 CAPUNITS Char 1 Ca
pacity Unit Code 153 WINTHRU Real 2.0 Winter
throughput ( of Annual) 155 SPRTHRU Real 2.0 Spr
ing throughput ( of Annual) 157 SUMTHRU Real 2.0
Summer throughput ( of Annual) 159 FALTHRU Real
2.0 Fall throughput ( of Annual) 161 HOURS Int
2 Normal Operating Time (hours/day) 163 START Int
2 Normal Operation Start Time 165 DAYS Int 1 Nor
mal Operating Time (days/week) 166 WEEKS Int 2 No
rmal Operating Time (weeks/year)
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. . . 218 SIC Int 4 Standard
Industrial Classification Code 222 LATC Real 9.4
Latitude (decimal degrees) 231 LONC Real 9.4 Long
itude (decimal degrees)
. . . 401 VOC_ANN Real 13.4 VOC
Annual Emissions (short tons) 414 NOX_ANN Real 13
.4 NOX Annual Emissions (short tons) 427 CO_ANN R
eal 13.4 CO Annual Emissions (short
tons) 440 SO2_ANN Real 13.4 SO2 Annual Emissions
(short tons) 453 PM10_ANN Real 13.4 PM10 Annual
Emissions (short tons) 466 PM25_ANN Real 13.4 PM2
.5 Annual Emissions (short tons) 479 NH3_ANN Real
13.4 NH3 Annual Emissions (short
tons) 492 VOC_OSD Real 13.4 VOC Ozone Season
Emissions (tons/day) 505 NOX_OSD Real 13.4 NOX
Ozone Season Emissions (tons/day) 518 CO_OSD Real
13.4 CO Ozone Season Emissions
(tons/day) 531 SO2_OSD Real 13.4 SO2 Ozone
Season Emissions (tons/day) 544 PM10_OSD Real 13.
4 PM10 Ozone Season Emissions (tons/day) 557 PM25_
OSD Real 13.4 PM2.5 Ozone Season Emissions
(tons/day) 570 NH3_OSD Real 13.4 NH3 Ozone
Season Emissions (tons/day) . . .
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1995 NET Area Source File Start Field Type Len
gth Description ----------------------------------
----------------- 1 STID Int 2 State
Code 3 CYID Int 3 County Code 6 SCC
Char 10 Source Classification
Code 16 VOC_ANN Real 10.4 VOC Annual Emissions
(short tons) 26 NOX_ANN Real 10.4 NOX Annual
Emissions (short tons) 36 CO_ANN Real 10.4 CO
Annual Emissions (short tons) 46 SO2_ANN Real 10.
4 SO2 Annual Emissions (short tons) 56 PM10_ANN R
eal 10.4 PM10 Annual Emissions (short
tons) 66 PM25_ANN Real 10.4 PM2.5 Annual
Emissions (short tons) 76 NH3_ANN Real 10.4 NH3
Annual Emissions (short tons) 86 VOC_OSD Real 10.
4 VOC Ozone Season Emissions (tons/day) 96 NOX_OSD
Real 10.4 NOX Ozone Season Emissions
(tons/day) 106 CO_OSD Real 10.4 CO Ozone Season
Emissions (tons/day) 116 SO2_OSD Real 10.4 SO2
Ozone Season Emissions (tons/day) 126 PM10_OSD Re
al 10.4 PM10 Ozone Season Emissions
(tons/day) 136 PM25_OSD Real 10.4 PM2.5 Ozone
Season Emissions (tons/day) 146 NH3_OSD Real 10.4
NH3 Ozone Season Emissions (tons/day) .
. .
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Motor Vehicle VMT File This format used for
both NET and MIDPRO format Mobile Source
files ASCII fixed-format Record Length 40
Characters Start Field Type Length Description --
----------------------------------------- 1 STID I
nt 2 State Code 3 CYID Int 3 County
Code 6 1 Not Used 7 SCC Char 10 AMS Source
Classification Code 17 1 Not Used 18 VMT Real 14
Vehicle Miles Travelled (106 mi/yr) 32 1 Not
Used 33 VTYPE Char 5 Vehicle Type 38 1 Not
Used 39 Int 2 Speed (mi/hr) Valid Vehicle
Types LDGV LDGT1 LDGT2 HDGV LDDV LDDT HDDV MC
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VOC emissions, July 1985
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CMAQ results O3 and PM2.5
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Model evaluation O3 (7/31 - 8/7/93)
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Model evaluation PM2.5
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Model application what if scenarios
What if gasoline is replaced by E10, M85, etc?
What if electrical vehicles are used?
What if a regulation is developed and/or
implemented ?
What if a highway is built or widened ?
What if a new power plant is built in location A?
What if NOx emissions are reduced by 50?
. . .
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Model application impact of alternative
fuels The Sparse Matrix Operator Kernel
Emissions (SMOKE) Modeling System integrates
emissions data processing with high-performance
computing (HPC) sparse-matrix algorithms.