United States
Environmental Protection
Agency
Air and Energy Engineering Y
Research Laboratory
Research Triangle Park NC 27711^ ,j
Research and Development
EPA/600/S7-89/010a Jan. 1990
SEPA Project Summary
The 1985 NAPAP Emissions
Inventory: Overview of Allocation
Factors
Robert A. Walters, Lysa G. Modica, and David B. Fratt
This report documents the
development of temporal, spatial, and
species allocation factors for the
1985 NAPAP anthropogenic point and
area source emissions inventories.
These allocation factors are used to
apportion annual emissions totals
into grldded, hourly, speciated
emissions estimates suitable for use
as input to atmospheric transport
models such as the Regional Acid
Deposition Model (RADM).
Allocation factors are statistical
representations of the spatial and
temporal distribution of annual
emissions, or representative
speciatlon profiles for particular
source types. Factors are generally
applied to NAPAP annual emissions
records on the basis of point source
SCO or NAPAP area source category.
The temporal, spatial, and species
allocation factors are discussed in
detail in separate report sections.
Each section contains a description
of the methodology for application of
the factors, a discussion of data
sources, and documentation of the
activities undertaken to create the
allocation factor data sets used in the
1985 NAPAP resolved modeling In-
ventories.
This Project Summary was
developed by EPA's Air and Energy
Engineering Research Laboratory,
Research Triangle Park, NC, to
announce key findings of the research
protect that is fully documented in a
separate report of the same title (see
Project Report ordering Information at
back).
Temporal Allocation Factors
In support of modeling applications, the
annual emissions totals must be resolved
temporally into 24 hourly totals for a
typical weekday, Saturday or Sunday in
each of the four seasons of the year. To
accomplish this resolution, the NAPAP
temporal allocation factors were
developed.
Temporal factors were created for U. S.
point and area source emissions
categories in the NAPAP inventories.
Factors for the 1985 NAPAP inventory
were derived primarily from temporal
factors developed for the 1980 NAPAP
effort. They reflect data from a variety of
sources, which include previous modeling
studies, as well as enhancements
deemed necessary as part of the ongoing
development of the NAPAP inventories.
Factors were developed for each of the
102 area source categories reported in
the 1985 inventories. In most cases,
temporal allocation of point source data is
accomplished using operating schedule
information provided with the emissions
records. However, given the magnitude of
emissions from electric utilities, process-
level (fuel and state specific) factors were
developed to more accurately charac-
terize these sources.
Efforts to enhance the accuracy of
temporal allocation are ongoing. Factor
normalization has eliminated summation
errors which previously resulted when
temporally apportioned emissions were
reaggregated. Other modifications
included the incorporation of data
sources which enhance the accuracy of
temporal allocation.
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Spatial Allocation Factors
Spatial allocation factors were
developed to apportion area source
emissions from counties to individual grid
cells as required for modeling
applications. The actual spatial
distribution of emissions is estimated
according to the distribution of surrogate
indicators. Fourteen such indicators were
developed for use with the NAPAP
inventory based on housing, population,
and land-use data. For the 1985 NAPAP
application, 6 of the 14 surrogates are
used for spatial allocation.
To ensure the quality and repre-
sentativeness of the spatially resolved
1985 area source inventory, extensive
quality control (QC) checks were
performed on the existing spatial factors.
QC procedures were both data and
software intensive. Data analysis focused
on evaluating spatial factors at the
countylevel and ensuring the quality of
national-, state-, and SCC-level gridded
emissions totals. Software-intensive eval-
uations included reviewing computer
code and implementing modifications to
the spatial factor software for other
applications. Based on the results of the
QC procedures, the spatial factors and
computer programs were adjusted. Once
the adjustments were made, QC checks
were performed to assure the quality of
the modified spatial factors.
Speciation Factors
Several of the pollutants in the 1985
NAPAP annual inventory represent
composites of various individual species.
To accommodate RADM requirements,
annual hydrocarbon emissions estimates
are split into 32 chemical species
classes, annual NOX estimates are
divided into N02 and NO, and TSP
emissions are resolved into 15 classes
based on alkalinity and size fraction.
An updated EPA air emissions species
manual served as the basis for the 1985
NAPAP speciation files for total
hydrocarbons and particulate matter.
Specific species-class assignments were
developed by the National Center for
Atmospheric Research (NCAR), while
percentage splits for NO and NO2 were
taken from the 1980 NAPAP inventory
without significant modification.
Hydrocarbon species data were also
used to create files for the preprocessing
of VOC and THC to account for the lack
of formaldehyde and methane in some
NEDS emissions estimates.
R. Walters, L Modica, and D. Fratt are with Alliance Technologies Corp., Bedford,
MA 01730.
Robert C. Lagemann is the EPA Project Officer (see below).
The complete report, entitled "The 1985 NAPAP Emissions Inventory: Overview of
Allocation Factors," (Order No. PB 90-126 012/AS; Cost: $23.00, subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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