4.3 Temporal Allocation of Emission Data

Emission data that are based on annual, seasonal, weekly, or

daily values may be temporally allocated to hourly data used

in the air quality model. Generally, this procedure is applied

to regional inventories of point- and area-source emission

data. Biogenic- and mobile-source emissions may be

directly modeled as hourly data for the time period of

interest, rather than extracted from an inventory. Allocation

of emission data from time periods greater than hourly down

to hourly data is accomplished by use of source categoryspecific

seasonal, monthly, weekly, and daily temporal

allocation factors. SMOKE allocates emissions to

successively more highly resolved periods (annual to

seasonal, seasonal to weekly, weekly to daily). The daily

values are then transformed into emission values for each

hour of a typical day by using user-supplied or default

temporal allocation profiles. Temporal profiles developed

for the National Acid Precipitation Assessment Program

(NAPAP) (Fratt et al. [42]), with some more recent

supplements (Moody et al. [43]), are used currently. These

are available from EPA at

http://www.epa.gov/ttn/chief/emch/temporal/.

4.4 Chemical Speciation of Emission Data

Chemical transport models, including the CCTM, require

that emission data be provided for either individual species

or lumped species. However, an initial processing step is

required because emission data are usually reported for

16

pollutants that are aggregates of many species, such as

volatile organic compounds (VOCs) or fine particles having

diameters less than 2.5 μm (PM2.5). These aggregate

pollutants must be split into their component species, or

speciated. The speciation takes two forms, discrete and

lumped-model. In discrete speciation, a pollutant is split

into the individual chemical components. The discrete

components in an emission stream are determined by a

number of methods including source testing, surrogate

application, and engineering knowledge of the process. In

lumped speciation, individual organic species are assigned

to one or more model species (groups of species) according

 

 

 

n1001 - n1002 - n1003 - n1004 - n1005 - n1006 - n1007 - n1008 - n1009 - n1010 - n1011 - n1012 - n1013 - n1014 - n1015 - n1016 - n1017 - n1018 - n1019 - n1020 - n1021 - n1022 - n1023 - n1024 - n1025 - n1026 - n1027 - n1028 - n1029 - n1030 - n1031 - n1032 - n1033 - n1034 - n1035 - n1036 - n1037 - n1038 - n1039 - n1040 - n1041 - n1042 - n1043 - n1044 - n1045 - n1046 - n1047 - n1048 - n1049 - n1050

 

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