906R89104
March 1989
PROCEDURES FOR
ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS
OF AIR TOXICS
WORKING DRAFT
Original
Prepared by:
Versar, Inc. -
6850 Versar Center
Spingfield, VA 22151
EPA Contract No. 68-02-4254
Work Assignment 105
Prepared for
Dallas Safriet
Noncriteria Pollutant Programs Branch
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
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Table of Contents
Page
Preface 1-1
1. INTRODUCTION 1-4
1.1 Background 1-4
1.2 General Methodology 1-5
1.3 Steps In Conductinq An Emission Inventory I"8
1.4 Format of This Manual 1-9
2. SOLVENT USAGE 2-1
2.1 General 2-1
2.2 Surface Coating 2-7
2.3 Dry Cleaning 2-9
2.4 Degreasing (Solvent Cleaning Operations) 2-10
2.5 Rubber and Plastics 2-12
2.6 Graphic Arts (Printing and Publishing) 2-13
2.7 Other Industrial Solvent Usage 2-15
2.8 Commercial/Consumer Solvent Usage 2-16
2.9 Example Calculations 2-17
2.10 Methods to Apportion Countywide Emissions
from Solvent Usage 2-18
3. HEATING (INCLUDING WASTE OIL COMBUSTION) 3-1
3.1 General 3-1
3.2^ Industrial Heating 3-7
3.3 Commercial and Institutional Heating 3-10
3.4 Residential Heating 3-13
3.5 Waste Oil Combustion 3-18
3.6 Example Calculations 3-24
3.7 Methods to Apportion Countywide Emissions
from Heating 3-26
4. ROAD VEHICLES 4-1
4.1 General 4-1
4.2 Factors 4-1
4.3 Methodology Options 4-2
4.4 Example Calculations 4-3
4.5 Methods to Apportion Countywide Emissions
from Road Vehicles 4-13
5. AIRCRAFT 5-1
5.1 General 5-1
5.2 Factors 5-1
5.3 Methodology Options 5-1
5.4 Example Calculation 5-8
5.5 Methods to Apportion Countywide Emissions
from Aircraft 5-10
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Table of Contents
Page
6. COMFORT AND INDUSTRIAL COOLING TOWERS 6-1
6.1 General 6-1
6.2 Factors 6-4
6.3 Methodology Options 6-9
6.4 Example Calculations 6-13
6.5 Methods to Apportion Countywide Emissions
from Cooling Towers 6-16
7. FOREST FIRES AND AGRICULTURAL BURNING 7-1
7.1 General 7-1
7.2 Factors 7-1
7.3 Methodology Options 7-2
7.4 Example Calculations 7-9
7.5 Methods to Apportion Countywide Emissions
from Forest Fires and Agricultural Burning 7-11
8. GASOLINE SERVICE STATIONS (GASOLINE MARKETING) 8-1
8.1 General 8-1
8.2 Factors '. 8-3
8.3 Methodology Options 8-3
8.4 Example Calculations 8-11
8.5 Methods to Apportion Countywide Emissions
from Gasoline Marketing 8-12
9. CHROMIUM ELECTROPLATING -. 9-1
9.1 General 9-1
9.2 Factors 9-2
9.3 Methodology Options 9-3
9.4 Example Calculation 9-5
9.5 Methods to Apportion Countywide Emissions
from Chromium Electroplating 9-5
10. HOSPITAL AND LABORATORY STERILIZERS 10-1
10.1 General 10-1
10.2 Factors 10-2
10.3 Methodology Options 10-4
10.4 Example Calculations 10-5
10.5 Methods to Apportion Countywide Emissions 10-6
11
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Table of Contents
Page
APPENDIX A METHODS TO APPORTION COUNTYWIDE AREA
SOURCE EMISSIONS A-l
A.I Direct Determination of Emissions
within an Area Source Grid A-2
A.2 Spatial Apportionment A-2
A.3 Mobile Source Apportionment A-15
A.4 Temporal Distribution of Countywide Emission
Estimates A-17
A.5 Example Calculations A-18
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List of Tables
1-1 Source Categories Not Covered 1-2
1-2 Standard NEDS Area Source Categories 1-7
2-1 National Solvent Consumption by
User Category 2-3
2-2 SIC Codes Comprising Solvent Use Categories 2-4
2-3 Employee-Based Emission Factors
for Solvent Usage 2-5
2-4 Per Capita Emission Factors for Solvent Usage 2-6
2-5 Spatial and Temporal Resolution of Countywide
Emissions Totals for Solvent Usage 2-20
3-1 Thermal Equivalents for Various Fuels 3-6
3-2 Densities of Selected Fuels 3-6
3-3 Emission Factors for Industrial Area
Source Heating 3-8
3-4 Emission Factors for Commercial/Institutional
Area Source Heating 3-11
3-5 Emission Factors for Residential Area
Source Heating 3-14
3-6 Apportionment of Residential Wood Consumption
Between Fireplaces (FP) and Wood Stoves (WS)
for the Year 1976 3-16
3-7 Waste Oil Consumption by State 3-19
3-8 Waste Oil Characteristics and Combustion
Emission Factors 3-20
3-9 Spatial and Temporal Resolution for Heating
and Waste Oil Combustion 3-28
4-1 Road Vehicle Emission Factors 4-2
4-2 Spatial and Temporal Resolution for Road Vehicles ..4-15
5-1 Military Aircraft : 5-2
5-2 Civil Aircraft 5-4
5-3 Commercial Aircraft 5-6
5-4 Spatial and Temporal Resolution for Aircraft 5-11
6-1 Lower- and Upper-Bound Estimates of Annual
Cr+5 Emissions. Per Person by State 6-7
6-2 Industrial Cooling Tower Emission Factors 6-10
6-3 SIC Codes Included in Industry-Specific
Emission Factors 6-10
6-4 Industrial Cooling Tower hexavalent Chromium
Employee-Based Emission Factors 6-11
6-5 Temporal and Spatial Resolution for Industrial
and Comfort Cooling Towers 6-18
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List of Tables
Page
1-1 Source Categories Not Covered 1-2
7-1 Emission Factors Used to Estimate Emissions From
Wildfires, Managed Burning and Agricultural Burning .. 7-3
7-2 Summary of Hydrocarbon Emission Factors for Forest
Wildfires 7-4
7-3 Volatile Organic Species Profile From Typical Forest
Wildfires 7-5
7-4 Summary of Estimated Fuel Consumed by Forest Fires 7-7
7-5 Spatial and Temporal Resolutions for Agricultural
Burning 7-13
8-1 Selected Air Toxic Emissions From Gasoline Stations .... 8-4
8-2 VOC Speciation Factors for Gasoline Marketing 8-5
8-3 Spatial and Temporal Resolutions for Gasoline
Marketing 8-14
9-1 Uncontrolled Emission Factors Used to Estimate
Emissions from Chromium Electroplating Operations .... 9-4
9-2 Spatial and Temporal Resolution for Chromium
Electroplaters 9-7
10-1 Spatial and Temporal Resolution of Countywide Emission
Totals for Hospital and Laboratory Sterilizers 10-8
A-l Land Use Categories A-8
A-2 Example of Grid Cell/Area Source Grid Matrix A-10
A-3 Example of an Apportionment of Area Source Categories
by Land Use Category (land use/area source matrix) ... A-ll
VI
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List of Figures
Page
1-1- Area Source/Pollutant Matrix 1-10
7-1 Forest Area and U.S. Forest Service Regions 7-8
A-l Land Use Map A-24
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Interim Procedures For Estimating And
Allocating Area Source Emissions of
Ai r Toxics
Preface
Most of the initial draft of this report was prepared under contract
to the Environmental Protection Agency (EPA) Pollution Characterization
Section, Non-Criteria Pollutant Programs Branch (NPPB) in response to the
recognized need to be able to estimate emissions of various toxic air
pollutants to the atmosphere from various area sources. These area
sources are generally individually small but numerous and often scattered
throughout an air basin. Automobiles, for example, are categorized as an
area source, as are residential woodstoves. Small commercial and industrial
operations such as cooling towers may also be small localized sources of
toxic air pollutants which collectively may have a major impact upon
health risk estimates.
As a result of the contractor's effort, and other agency work,
available methodologies and emission factors were examined and incorporated
into this report. The procedures and factors that resulted are better in
some areas than others. Many of the procedures can be traced to procedures
developed for the National Emissions Data System (NEDS) over 15 years
ago. Though age does not necessarily indicate inadequacy, the staff of
the Pollutant Characterization Section has felt that there may be better
ways for estimating emissions that could be developed or perhaps may
already be in use in some State and local agencies. Also, it is felt
that the source coverage may not be complete (see Table 1-1). Consequently,
this document is being distributed as an interim or "Working Draft"
document so that State and local personnel may (1) use it for benefit as
applicable, (2) provide comments and alternate procedures or other
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
TABLE 1-1
Source Categories Not Covered
Structural Fires
Motor-boats
Cutback Asphalt
Cold Cleaning
Construction Equipment
Railroads
Industrial Equipment
Wastewater
On-Site Incineration.
Vessels
Pesticides
Farm Equipment
3/89
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
improvements, (3) use it to stimulate development of new procedures and
factors, and (4) use it as the initiation of a "clearinghouse" of the
agencies' methods and procedures.
Depending upon comments and other feedback, EPA will likely revise
and upgrade this document in the future. The unbound format of this
document is used to facilitate this concept. Users and specialists in
the field are encouraged to provide reactions, ideas and comments directly
to EPA at the following address:
Pollutant Characterization Section
Non-Criteria Pollutant Programs Branch
Office of Air Quality Planning and Standards
U. S. Environmental Protection Agency
MD-15
Research Triangle Park, NC 27711
Any comments and feedback received by August 1989 will facilitate
planning and implementation of the first update/revision. Holders of the
document who wish to be provided with updates to the document should
advise EPA, in writing, at the above address if they were not the original
addressee of the document. It would also be helpful in this case to
provide the name and address of the original addressee who will need to
be dropped from the mail key.
3/89
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
1.0 INTRODUCTION
1.1 Background
This manual is intended to provide methodologies, techniques,
procedures, and emission factors that can be used by state and local
environmental agencies in estimating and allocating area source emissions
of toxic air pollutants in a given area. When applied in combination
with a detailed point source inventory, this handbook can be used as a
guide to develop the area source portion of a comprehensive air toxics
inventory. The emissions data can then be used in combination with air
dispersion modeling and risk assessment to estimate ambient levels of,
and exposures to air toxic^ and the accompanying environmental and health
impacts.
The content of this manual is based on information and data available
at the time of preparation. In a number of cases, emission factors are
based on limited test data of varying quality or may rely on gross
assumptions that were the best possible at that time. It is generally
assumed that emission rates are, on average, uniform throughout the
country. Many of the activity coefficients (i.e., usage rates) that are
used with emission factors to estimate pollutant loadings are also generic
in nature, but are scaled to the local level based on employment by
Standard Industrial Classification (SIC) code, population density, etc.
This document has been designed in a looseleaf format, permitting
periodic updates and revisions as additional or more complete data become
available, or as improved procedures are identified. The EPA's intent
is for this format to facilitate its being a "clearinghouse" of procedures
that exist or may be developed.
3/89
INTRODUCTION
1-4
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
1.2 General Methodology
Area source emissions are estimated by multiplying an emission factor
by some known indicator of collective activity for each source category
within the inventory area. An indicator is any parameter associated with
the activity level of a source, such as production, employment, or
population, that can be correlated with the air pollutant emissions from
that source. For example, emissions of volatile organic compounds (VOC)
from dry cleaning facilities in an area correlate well with population;
thus, it is possible to develop a per capita emission factor that can be
used to estimate emissions. As another example,, the total amount of
gasoline handled by service stations in an area can be used to estimate
collective evaporative losses from gasoline handling.
Estimates can be derived by (1) treating area sources as point
sources, (2) surveying (e.g., telephone or questionnaire) local activity
levels, (3) apportioning national or statewide activity totals to local
inventory areas, (4) using per capita emission factors, (5) using emissions-
per-employee factors, or (6) a combination of these. Each method has
distinct advantages and disadvantages when used for developing area source
emissions estimates. The merits of these alternative methods must be
evaluated on a source-category-specific basis.
One alternate approach for estimating area source emissions is to
assume that either population data or employment data are a good indicator
of emission rates. Assuming that emissions are greatest in high population
density areas is reasonable for many area source categories. Employment
within an area source category, for example dry cleaners, can be used as
an indicator of activity and emissions.
3/89 " INTRODUCTION
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
There are many approaches to estimating air toxics area source
emissions. A simple approach, when practical, is to utilize output
from the (now defunct) NEDS, a computerized data base that is now being
replaced with the Aerometric Information Retrieval System (AIRS). This
system is focused primarily on the five criteria air pollutants (particulates,
SOX, NOX, CO and hydrocarbons). The National Air Data Branch (NADB),
Research Triangle Park, North Carolina, maintains the AIRS Data Base and
NEDS area source data. These data are available as standard publications,
computer printout reports, or magnetic tape files. The activity level
information available may be most useful to the person or agency making a
toxics area source estimate. Also available are data for parti cul ate and
volatile organic compound emissions, fuel use, vehicle miles traveled,
solvent consumption, and gasoline marketed. The NEDS area source categories
are shown in Table 1-2.
Area source emission estimates are calculated for each source
category, utilizing criteria pollutant emission factors contained in the
area source emission factor f-ile. For many categories, the same emission
factors are used for all counties; however, for some source categories,
state- or county-specific emission factors account for local variability
that affect emissions. Locale specific emission factors are used in NEDS
calculations for highway motor vehicle categories, fugitive dust categories
and for selected other categories in a few counties where more detailed
data area available to develop more applicable emission factors than the
national emission factors. Provision is also made to override computer-
calculated emissions for any county source category by hand calculated
emissions, which may allow more judgmental applications than simple
computerized emission-factor calculations.
3/89
INTRODUCTION
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
TABLE 1-2
Standard NEDS Area Source Categories
(Criteria Pollutants)
Residential Fuel
Commercial and Institutional Fuel
Industrial Fuel
Gasoline Fuel
Gasoline Powered Vehicles
Hi ghway
Off Highway
Diesel Powered Vehicles
Highway
Off Highway
Railway Locomotives
Ai rcraft
Vessels
Evaporative Loss
Solid Waste Disposal
Residential
Commercial and Institutional
Industrial
Fugitive Dust
Other
Wildfires
Managed Burning
Orchard Heaters
Structure Fires
3/89
INTRODUCTION
1-7
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
The NEDS-based approach has the advantage of easy access. There are,
however, alternative approaches for estimating activity levels and emission
rates. Sometimes these alternative approaches will be more accurate;
activity or emissions might, for example, be based on a site-specific
survey of sources in the area, or many differ because of local regulation.
Once countywide emissions of area sources are estimated, air dispersion
modeling may be conducted to predict the contribution of area source
emissions on ambient levels and population exposures. It is generally
recommended that county wide area source emissions be distributed within
the study area inio rectangular area source grid cells and that spatial
seasonal and temporal variations of emissions be factored into the
apportionment. Modeling results can then more accurately reflect ongoing
activities in different sections of the county.
1.3 Steps In Conducting An Emission Inventory*
An air toxics area source emission inventory may generally be
conducted in five initial steps:
1. Collecting data on national, state and local area source
activity levels (NEDS reports can be the source of many of
these data);
2. Collecting demographic, economic and other data to be used
to apportion activity levels and emission factor parameters;
3. Apportioning the areawide (typically a State) activity
levels of area sources to the county level using apportionment
factors;
4. Calculating estimated area source emissions by applying
emission factors to the apportioned area source activity
levels, and
5. Converting the source information and emissions to a formal
formatted record and placing this record in a file (manual
or automatic).
Alternatively, however, many agencies chose to use existing inventory
data for VOC arvd particulate and speciate them into their toxic components.2
3/89 INTRODUCTION 1-8
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
It is essential to document data and procedures used in compiling the
inventory. Thorough documentation allows the agency to identify sources
of raw data and data-handling methods used to estimate emissions.
Documented procedures must be followed during quality assurance checks
and when the inventory is being updated with new data.
1.4 Format Of This Manual
The remainder of this manual consists of individual sections organized
by source category. Each of these sections describes the source category
and presents procedures and emission factors to estimate toxic emissions
on an annualized basis. Multiple techniques to predict emission rates
are described. Example calculations have also been provided to demonstrate
how to apply the various factors and algorithms. Spatial apportionment
techniques can be used once countywide annual emission estimates are
determined to distribute emissions throughout the county, concentrating
emissions in those parts (grids) of a county where the emissions are
likely to be greatest. Temporal factors are provided so that emissions
can reflect seasonal, daily or hourly variations of emissions; this input
is especially useful when used in conjunction with air dispersion modeling.
Appendix A elaborates on these apportionment methodologies.
Figure 1-1 is a matrix indicating sources and pollutants covered in
this manual. The absence of an entry for a pollutant does not necessarily
imply that the source does not emit contaminants, but rather that no
emission factor has been identified.
3/89 "• INTRODUCTION 1-9
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
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INTRODUCTION
1-10
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REFERENCES
1. Air Emissions Species Manual, Volume I: Volatile Organic Compound
(VOC) Species Profiles And Volume II: Particulate Matter (PM) Species
Manual. EPA-450/2-88-003a and b, U. S. Environmental Protection
Agency, Research Triangle Park, NC, April 1988.
2. Procedures For Emission Inventory Preparation, Volume III: Area
Sources.EPA-450/4-81-OZ6c, Office of Air Quality Planning and
Standards, Research Triangle Park, NC, September 1981.
3/89 ' INTRODUCTION 1-H
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
2. SOLVENT USAGE
2.1 General
For purposes of toxic inventories, solvents are defined as any liquid
organic compounds (or group of compounds) that are used to dissolve other
materials. These compounds can be used as cleaning agents or in the
application of a product. Some or all of the solvent typically
evaporates into the atmosphere, resulting in potentially significant
emissions of a variety of chlorinated and unchlorinated organic toxic air
pollutants. i
Solvents are used in numerous industrial, commercial, and domestic
applications, thus complicating the development of a solvent emission
inventory. As with other area source categories, major sources should.be
treated as point sources, using methods described in AP-42 and
Procedures for the Preparation of Emission Inventories for Volatile
2
Organic Compounds, Volume 1. However, because of the large number of
small solvent users, it is necessary to develop countywide area source
estimates.
Organic solvent usage can be divided into seven major subcategories:
• Surface coating;
• Dry cleaning;
, Degreasing;
• Graphic arts (printing and publishing);
• Rubber and plastics;
• Other industrial; and
• Commercial/consumer (nonindustrial);
Walden allocated consumption of specific organic solvents by
county according to national solvent consumption of 17 photochemically
3/89 . SOLVENT USAGE 2-1
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
reactive solvents. That technique estimated consumption by major user
category based on county population or user category employment data.
GCA updated Walden's estimates to reflect 1985 consumption patterns.
For this manual, the list of solvents has been further expanded to
include data for two nonreactive organic compounds, 111-trichloroethane
and methylene chloride; this revised table is presented in Table 2-1.
By assuming that all solvent consumed in the study area is emitted
somewhere within the study area (at the user site; during transport; at a
treatment, storage, and disposal facility; or at a sewage or wastewater
treatment plant), 7they can then estimate total emissions from solvent
consumption, by category, can be estimated.
Based on this conservative assumption, two sets of emission
factors--population-based and employment-based--have been derived. These
factors should be used only when area-specific data, usually based on
surveys, are not available. The former set, of these factors assumes
that area source solvent emissions within a study area (e.g., county,
city, state) are directly proportional to the population living within
the study area, as reported in the 1980 U.S. Census. The latter set of
emission factors, generally believed to be more accurate for industrial
user categories, assumes that emissions are directly proportional to
employment in Standard Industrial Classification (SIC) codes (as reported
Q
in County Business Patterns ) of likely solvent users such as dry
cleaners or degreasers. (For commercial/consumer solvent use, population
serves as an indicator of consumption.) Table 2-2 shows which industrial
categories comprise each solvent user category. Table 2-3 presents
employee-based factors, while Table 2-4 contains per capita factors.
In the discussion below, each user category is described along with
methodologies for estimating emissions. Example calculations are
provided in Section 2.8.
6/88 : SOLVENT USAGE 2-2
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
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SOLVENT USAGE
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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Table 2-2 SIC Codes Comprising Solvent Use Categories
Solvent Use Categories
SIC Codes
Surface Coatings
Trade Paints-Auto Refinishing
Auto Refinishing (Trade)
Automotive
Wood Furniture and Fixtures
Metal Furniture and Fixtures
Metal Containers
Sheet Strip and Coil
Appllances
Machinery and Equipment
Paper
Factory-finished Wood
Transportation (Non-Auto)
Electric Insulation
Other, Exterior, Interior
Marine
Decreasing
Dry Cleaning
Rubber and Plastics
Other Industrial
7535 (Paint Shops)
371 (Motor Vehicles)
25 (Furniture and Fixtures)
34 (Fabricated Metal Products)
35 and 36 (Machinery, Electrical)
Equipment and Supplies
26 (Paper and Allied Products)
243, 244 (Millwork, Plywood-
Related Supplies, Wooden Containers)
37 (Transportation Equipment)
Less 371 (Motor Vehicles) and
373 (Shipbuilding Repair)
36 (Electrical Equipment and
Supplies
19-39 (Total Manufacturing)
373 (Shipbuilding and Repair)
34-39 (Metal Products, Machinery,
Transportation Equipment,
Instruments, Miscellaneous)
2 x 7216, Plus 7215 and 7218 (Dry
Cleaning and Combination with Wet
Laundering
264, 265, and 27 (Paper Products,
Containers, Printing and Publishing
30 (Rubber and Plastics)
1/2 of 19-39 Employment -i
County Employment
1/2
6/88
SOLVENT USAGE
2-4
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
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6/88
SOLVENT USAGE
2-6
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
2.2 Surface Coating
The surface coating solvent use subcategory involves the application
of paint, varnish, lacquer, or paint primer for decorative or protective
purposes. This is accomplished by brushing, rolling, spraying, flow
coating, and dipping operations.
Solvents are emitted as the coating material dries. Compounds
released include aliphatic and aromatiac hydrocarbons, alcohols, ketones,
esters, alky! and aryl hydrocarbon solvents, and minteral spirits.. The
trend toward water-based coatings is reducing the magnitude of solvent
emissions.
Surface coatings can be divided into the following categories:
Architectural surface coatings, often called "trade paints," are used
primarily by homeowners and painting contractors to coat the interior or
exterior of houses and buildings and of other structures such as
pavements, curbs, or signs. Painting contractors and homeowners are the
major users of architectural coatings.
Solvents used for thinning architectural surface coatings and for
clean up after application also contribute significantly to volatile
organic compound (VOC) emissions associated with the architectural
coating process.
Automobile refinishing encompasses the repainting of worn or damaged
automobiles, light trucks, and other vehicles. Surface coating during
manufacture is not considered refinishing. In automobile refinishing,
lacquers and enamels are usually spray-applied in paint booths. Since
vehicles contain heat-sensitive plastics and rubber, solvent-borne
6/88 ". SOLVENT USAGE 2-7
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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coatings that can dry in low-temperature ovens are used. Paint booths
may be equipped with paint arresters or water curtains to handle
overspray.
Industrial surface coating includes the coating, during manufacture,
of magnet wire, automobiles, cans, metal coils, paper, fabric, metal and
wood furniture, and miscellaneous products. Materials applied in coating
include adhesives, lacquers, varnishes, paints, and other solvent-borne
coating material. Many surface coating facilities generate sufficient
emissions to be considered major sources, and should be included in the
point source inventory. However, small sources probably will still be
present in any developed inventory area.
There are two generic methods of estimating emissions from the
application of surface coating:
Method 1. Calculate emissions based on employment data in County
n
Business Patterns for industrial categories listed in Table 2-2 that
conduct surface coating. Apply emission factors provided in Table 2-3.
Be certain to subtract emissions accounted for in point source
inventories (or subtract point source employment prior to calculating
area source emissions).
Method 2. Apply per capita emission factors contained in Table 2-4
(a less accurate method requiring fewer resources). Here, too, it is
necessary to subtract any emissions included in the point source
inventories. Countywide population data can be collected from the U.S.
Census Bureau.
6/88 -. SOLVENT USAGE 2'8
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2.3 Dry Cleaning
Dry cleaning operations vary in size, type of service, and type of
solvent used. Industrial, commercial, and self-service facilities clean
not only personal clothing, but also uniforms, linens, drapes, and other
fabric materials. Three basic solvent types are used in dry cleaning:
petroleum (Stoddard), tetrachloroethylene or perchloroethylene ("perc"),
and trichlorotrifluoroethane (Freon® 113). Perchloroethylene is used
in approximately 80 to 90 percent of all dry cleaning establishments and
constitutes about 70 percent of all cleaning solvent consumed. Almost
all other establishments use petroleum solvent. The use of fluorocarbons
as a dry cleaning solvent is decreasing in popularity and is not
considered in this report.
VOC emissions from dry cleaning vary with the type of process and
^ent used. Detailed process descr
and controls can be obtained in AP-42
solvent used. Detailed process descriptions and information on emissions
,1
Virtually all commercial and self-service dry cleaning facilities are
area sources, while industrial dry cleaning facilities may be either
point or area sources. There are several methods of estimating dry
cleaning emissions; three widely applicable methods are given below.
Method 1. Calculate emissions based on employment data provided in
County Business Patterns9 for SICs 7215, 7216, and 7218. Apply
emission factors provided in Table 2-3. Be certain to subtract emissions
accounted for in point source inventories (or subtract point source
employment) prior to calculating area source emissions.
Method 2. Multiply per capita emission factors contained in Table
2-4 by county population data (from the U.S. Census Bureau). (This is a
less accurate method requiring fewer resources). Again it is necessary
to subtract any emissions included in the point source inventories.
6/88 \ SOLVENT USAGE 2-9
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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Method 3. Send survey forms to a representative sample of dry
cleaners taken from the Yellow Pages or a similar telephone directory.
The data to be collected are number of employees, quantity of clothes
cleaned (ton/year), type and amount of solvent used (solvent purchased
minus solvent returned for recycle), and normal operating schedule.
Assume that all of the solvent used is emitted, and check the survey
values with emissions calculated as the product of the AP-42 emission
factors and the quantity of clothes cleaned. Emissions by solvent type
can then be estimated based on the survey results assumed that
alternatively, it can be 70 percent of all emissions are
perch!oroethylene, with the remainder being Stoddard Solvent (petroleum
distillates or special naphthas).
2.4 Deqreasinq (Solvent Cleaning Operations)
There are basically three types of degreasers: small cold cleaners,
open top vapor degreasers, and conveyorized degreasers. According to
recent estimates, there are about 1,300,000 small cold cleaning units
operating in the U.S. Seventy percent of these units are devoted to
maintenance of servicing operations, including service stations, auto
dealerships, and miscellaneous repair stations; the remaining 30 percent
are devoted to manufacturing operations. A typical cold cleaning unit
emits approximately one-third metric ton of VOC per year. In contrast,
typical open-top vapor degreasers and conveyorized degreasing units emit
10 and 27 metric tons of VOC per year, respectively. These larger units
are commonly used in the metalworking industry. The design and operation
of each of these types of degreasers will vary, as will emissions and the
2
types of control measures used. A broad spectrum of organic liquids,
including petroleum distillates (special naphthas), chlorinated
hydrocarbons, ketones, and alcohols is used in solvent cleaning
operations.
6/88 -. SOLVENT USAGE 2-10
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
The development of degreasing emission estimates is complicated by a
number of factors. First, some degreasers are large enough to be
considered point sources, yet a large fraction of all degreasers will
fall below the point source cutoff and should be accounted for as area
sources. Second, degreasing operations are not associated with any
particular industrial activity. Instead, degreasing of some sort may be
carried out in a wide variety of industries including (1) metal working
facilities (e.g., automotive, electronics, appliances, furniture,
jewelry, plumbing, aircraft, refrigeration, business machinery,
fasteners), (2) nonmetalworking facilities (printing, chemicals,
plastics, rubber, textiles, glass, paper, electric power), (3)
maintenance cleaning operations (electric motors, forklift trucks,
printing presses), and (4) repair shops (automobile, railroad, bus,
aircraft, truck, electric tool). Third, the fact that some of the VOC
emissions associated with degreasing occur at the solvent waste disposal
site complicates the location of emissions within the inventory area.
Open top vapor (OTV) cleaners and conveyorized cleaners are larger
operations that should be included in the point source inventory whenever
possible. These types of equipment tend to be associated with industrial
plants that are already included in the point source inventory. Cold
cleaners are smaller and usually are treated as area sources in an
inventory. For all degreasers not included in the point source
inventory, one of the following methods should be used to estimate
emissions for the category.
Method 1. Calculate emissions based on employment data provided in
q
County Business Patterns for SICs 34 through 39. Apply emission
factors provided in Table 2-3. Be certain to subtract emissions
accounted for in point source inventories (or subtract point source
employment prior to calculating area source emissions).
6/88 - SOLVENT USAGE 2-11
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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Method 2. A less accurate method requiring fewer resources is to
multiply per capita emission factors contained in Table 2-4 by U.S.
Census Bureau population data. Here, too, it is necessary to subtract
any emissions included in the point source inventories.
2.5 Rubber and Plastics
The rubber and plastics solvent user category (SIC 30 industries)
includes tire and inner tube manufacturing and the fabrication of other
rubber and plastic products such as footwear and hoses. Solvents are
used by these industrial categories for cleaning, molding, sealing, and
gluing. Special naphthas are the solvents used in greatest volumes;
lesser amounts of propylene glycol, ethyl acetate, and p-dichlorobenzene
are used.
Using emission factors provided on a per capita or per employee
basis, estimate emissions are explained below.
Method 1. Calculate emissions based on employment data provided in
q
County Business Patterns for SIC 30. Apply emission" factors provided
in Table 2-3. Be certain to subtract emissions accounted for in point
source inventories (or subtract point source employment prior to
calculating area source emissions).
Method 2. Multiply U.S. Census Bureau data for the county by per
capita emission factors contained in Table 2-4 (a less accurate method
requiring fewer resources). Again it is necessary to subtract any
emissions included in the point source inventories.
6/88 - SOLVENT USAGE 2-12
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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2.6 Graphic Arts (Printing and Publishing)
Printing of newspapers, books, magazines, fabrics, wall coverings,
and other materials is considered to be a graphic art application.
Inventorying the graphic arts (printing and publishing) industry is
complicated by the fact that the industry consists of approximately
q
50,000 facilities. About half of these establishments are in-house
printing services in nonprinting industries, further complicating
estimating techniques.
While printing inks vary in composition, they consist of three major
components: (1) organic or inorganic pigments that produce the desired
color, (2) the binder or solid components (organic resins, polymers,
oils, or rosins) that lock the pigments to the receiving material or
"substrate," and (3) solvents that dissolve or disperse the pigments and
binders and are usually composed of organic compounds. The solvent
evaporates, typically as heated air is passed across the wet surface, and
is exhausted to the atmosphere.
Solvent emissions vary depending on the type of printing process and
the ink used. Printing techniques used include:
Wet offset lithography, the process used to produce the majority of
books and pamphlets and an increasing number of newspapers, typically
uses inks containing between 5 (newspaper) and 40 percent solvent.
Solvents are usually petroleum derived (naphthas). Isopropanol can be
2
used to dampen the printing plate.
Letterpress is the oldest form of movable type printing. Letterpress
newspaper and sheet-fed printing use oxidative drying inks, which are not
a source of solvent emissions. Publication letter printing, on the other
hand, uses solvent-borne inks that are usually 40 percent petroleum-based
2
solvents; the solvents are driven off with heat.
6/88 -. SOLVENT USAGE 2-13
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PROCEDURES TOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Rotogravure systems are used in publications and advertising, such as
newspaper supplements; mail order catalogues; folding cartons and other
flexible packing materials; and specialty products such as wall and floor
coverings, decorated household paper products, and vinyl upholstering.
The inks typically contain 55 to 95 volume percent low-boiling-point
solvents, such as alcohols, aliphatic naphthas, aromatic hydrocarbons,
2
esters, glycol ethers, ketones, and nitroparaffins.
Flexoqraphy is used in flexible packing and laminates such as
multiwall bags, milk cartons, gift wrap, folding cartons, corrugated
cardboard, paper cups and plates, labels, tapes, and envelopes. It uses
water-based or organic-based solvents depending on the specific product.
Among the solvents used are alcohols or alcohols mixed with aliphatic
hydrocarbons or esters, glycols, ketones, and ethers.
Screen printing is used to print patterns or designs on fabrics.
Organic solvents (predominately mineral spirits) or water-based solvents
are used in the print pastes that are applied in the roller, flat screen,
and rotary screen printers.
Currently graphic arts emissions can be estimated by using one of
three methods:
Method 1. Multiply U.S. Census Bureau data for the county by per
capita emission factors contained in Table 2-4. It is necessary to
subtract any emissions included in the point source inventories.
Method 2. Calculate 'emissions based on employment data provided in
County Business Patterns9 for SICs 264 (Paper Products), 265
(Containers), and 27 (Printing and Publishing). Apply emission factors
provided in Table 2-3. Note that an emissions-per-employee approach may
not be as reliable as a per capita approach in the graphic arts solvent
6/88 '- SOLVENT USAGE 2-14
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
user category because of the uncertainty as to which facilities and
industries have captive graphic art capabilities. It is important to
subtract emissions accounted for in point source inventories (or subtract
point source employment prior to calculating area source emissions.)
Method 3. OAQPS has prepared a new air toxics speciation
manual that contains speciation factors for various printing and
publishing processes. If data are available on VOC emission rates from
printing and publishing processes in the study area, the speciation
factors can be applied to estimate emissions of individual compounds.
2.7 Other Industrial Solvent Usage
This category covers solvent releases from a variety of manufacturing
process and industries including:
• Synthetic organic chemical manufacturing (SOCM);
• Paint formulating;
• Ink formulating;
• Textiles;
• Iron and steel manufacturing (cold rolling mills);
• Pharmaceuticals; and
• Pesticides, herbicides, etc.;
All of these industries used and release solvents to the air.
Nationally, a variety of solvents are used in large quantities. (See
Table 2-2).
The diversified nature of the industries in this category, and the
multiple uses of many of the solvents make it impractical to survey
facilities to estimate emissions. However, emissions can be estimated on
a per capita basis or based on employment in user subcategories. Two
methods for estimating emissions are described below.
6/88 - SOLVENT USAGE 2-15
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Method 1. Calculate emissions based on employment data for
industries conducting surface coating according to County Business
Q
Patterns listed in Table 2-3. Apply emission factors provided in
Table 2-3. Be certain to subtract emissions accounted for in point
source inventories (or subtract point source employment prior to
calculating area source emissions).
Method 2. Multiply U.S. Census Bureau population data for the county
by per capita emission factors contained in Table 2.4. Here, too, it is
necessary to subtract any emissions included in the point source
inventories.
2.8 Commercial/Consumer Solvent Usage
Commercial/consumer uses of products containing solvents are not
easily quantified using questionnaires, surveys, or other inventory
methods that can make emission estimates locale-specific. Among the
commercial/consumer products that often contain solvents are aerosol
products such as (1) insect sprays, (2) paints and finishes,
(3) household products, (4) personal products, (5)- animal products,
(6) automotive and industrial products, (7) food products, and
(8) miscellaneous products, as well as nonaerosol products such as
(1) personal products, (2) household products, and (3) garage
products. Certain subcategories
commercial/consumer VOC emissions:
products. Certain subcategories account for the vast majority of
Paints, primers, and varnishes,
Hair sprays,
All-purpose cleaners,
Insect sprays,
Car polishes and waxes,
Room deodorants and disinfectants,
Adhesives,
Caulking and sealing compounds,
Moth control products,
6/88 -. SOLVENT USAGE 2-16
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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• Window and glass cleaners, and
• Herbicides and fungicides.
These sources account for 75 percent of commercial/consumer VOC
emissions, as reported in ongoing work by EPA.
Commercial/consumer solvent usage can be estimated using per capita
emission factors contained in Table 2-3 or 2-4. Emission factors are
multiplied by county population as listed in the U.S. Census.
2.9 Example Calculations
Examples are provided below to demonstrate the application of per
capita and employee-based factors.
Example Calculation 1
Estimate the annual area source emissions from degreasing in Delaware
County, Pennsylvania.
SIC codes 34-39 are identified in Table 2-1 as conducting
9
degreasing. Based on data in County Business Patterns, the employment
in Delaware County in SICs 34-39 is 12,704. Applying emission factors
from Table 2-3, emissions can be estimated.
Special naphthas = (12,704) x (58 lb/yr/employee) = 736,832 Ib/yr
Perch!oroethylene - (12,704) x (6.3 Ib/yr/employee) = 80,034 lb/yr
Trichloroethylene = (12,704) x (16 Ib/yr/employee) = 203,264 lb/yr
Monochlorobenzene = (12,704) x (58 Ib/yr/employee) - 736,832 lb/yr
1,1,1-Trichloroethylene = (12,704) x 44 lb/yr/employee) = 558,976 lb/yr
Methylene chloride = (12,704) x 7.6 Ib/yr/employee) = 96,550 lb/yr
6/88 - SOLVENT USAGE 2-17
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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Example Calculation 2
What are the total annual trichloroethylene emissions from solvent
usage in DeKalb County, Georgia?
The 1980 U.S. Census reports the population of DeKalb County to be
466,600.
Applying emission factors in Table 2-4, countywide emissions can be
calculated.
Surface Coating (466,600) x 8.8 x 10"6 Ib/capita = 4 Ib/yr
Degreasing (466,600) x 6.0 x 10"1 Ib/capita = 270,960 Ib/yr
Other Industrial (466,600) x 2.4 x 10"2 Ib/capita = 11,198 Ib/yr
Commercial/Consumer (466,600) x 7.9 x 10 Ib/capita = 3.686 Ib/yr
TOTAL = 294,848 Ib/yr
2.10 Methods to Apportion Countvwide Emissions from Solvent Usage
As described in Section 1.0 and Appendix A when performing air
dispersion modeling, it is generally recommended that countywide
emissions be distributed within the study area into rectangular area
source grid cells reflecting spatial variations in activity and
emissions. Similarly temporal in activities can be factored into the
modeling to reflect seasonal or diurnal fluctuations in emissions.
Modeling results would then reflect on-going activities in that portion
of the county, e.g., residential heating in the winter, commercial
solvent usage during working hours on weekdays.
There are three alternative approaches that can be used in spatially
distributing emissions: (1) population, i.e., the magnitude of emissions
6/88 : SOLVENT USAGE 2-18
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
within a grid are directly proportional to the population living in the
grid, (2) land area, i.e., emissions from a countywide distributed based
on the size of the area source cjrid, and (3) landuse patterns, that
assume that certain area source activities, most likely occur in certain
areas of the county, e.g., commercial, residential or industrial.
In apportioning emissions from solvent usage any of these methods may
be appropriate. Land area and population data can be readily obtained,
and applied as described in Appendix A. Land use data, available from
the U.S. Geological survey and other sources can be used in combination
with the spatial resolution for each category of solvent usage, to
•distribute emissions based on the type of activity being performed, as
shown in Table 2-5.
Estimated seasonal, daily, and hourly temporal resolution for each
category of solvent usage are also included in Table 2-5, and can be used
with annual countywide emissions data to estimate temporal variations.
6/88 \ SOLVENT USAGE 2-19
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Table 2-5 Spatial and Temporal Resolution of County Wide
Emissions Totals for Solvent Usage
1. Industrial Surface Coating (Solvent)
Spatial Resolution
Surrogate indicator:
Information source(s):
commercial/industrial areas (Codes
12, 13, and 15)
land use map
Temporal Resolution
Seasonal:
Daily:
Hourly:
uniform through the year
uniform through the week
80 percent from 0700 to 1900, 20
percent from 1900 to 2400, otherwise
zero
Nomndustnal Surface Coating
13
Spatial Resolution
Surrogate indicator:
Information source(s):
urban or builtup land (codes 11
through 17)
land use map
Temporal Resolution
Seasonal:
Daily:
Hourly:
Dry Cleaning13
Spatial Resolution
Surrogate indicator:
Information source(s):
Temporal Resolution
Seasona 1 :
Daily:
Hourly:
uniform through the year
uniform through the week
uniform 0700 to 1900, otherwise zero
commercial areas (codes 12 and 15)
Retail service employment, land use
map
uniform through the year
uniform Monday through Saturday
uniform 0700 to 1900, otherwise zero
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SOLVENT USAGE
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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Table 2-5 (continued)
Degreasing
13
Spatial Resolution
Surrogate indicator:
Information source(s)'
Temporal Resolution
Seasona 1:
Daily:
Hourly:
Rubber and Plastics (Solvent)
Spatial Resolution
Surrogate indicator:
Information source(s)
Temporal Resolution
Seasona 1:
Daily:
Hourly:
industrial area (codes 13 and 15)
land use map and Reference 14
uniform through the year
uniform Monday through Saturday
80 percent from 0700 to 1900, 20
percent from 1900 to 2400
commercial/institutional areas
(codes 12, 13, and 15)
land use map
uniform through the year
uniform through the week
80 percent from 0700 to 1900,
20 percent from 1900 to 2400,
otherwise zero
6. Graphic Arts (Solvent)
Spatial Resolution
Surrogate indicator:
Information source:
Temporal Resolution
Seasona 1:
Daily.
Hourly:
commercial areas (code 12)
land use map
uniform through the year
80 percent Monday through Saturday,
20 percent Sunday
uniform through the day
7. Other Industrial (Solvent)
Spatial Resolution
Surrogate indicator:
Information source:
Temporal Resolution
Seasonal:
Daily:
Hourly:
commercial areas (code 12).
land use map
uniform through the year
uniform through the week
80 percent from 0700 to 1900, 20
percent from 1900 to 2400, otherwise
zero.
6/88
SOLVENT USAGE
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Table 2-5 (continued)
Commercial/Consumer Solvent Use
Spatial Resolution
Surrogate indicator: residential,
commercial/institutional areas
(codes 12, 13, and 15)
Information source(s): land use map
Temporal Resolution
Seasonal: uniform through the year
Daily: uniform through the week
Hourly 80 percent from 0700 to 1900, 20
percent from 1900 to 2400
6/88 '- SOLVENT USAGE 2-22
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1.
2.
3.
4.
5.
PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
REFERENCES
U.S. Environmental Protection Agency. Compilation of Air Pollutant
Emission Factors Volume I: Stationary Point and Area Sources
(AP-42). EPA-460/3-81-005. Office of Air Quality Planning and
Standard. Research Triangle Park, NC. September 1985.
U.S. Environmental Protection Agency. Procedures for the Preparation
of Emission Inventories of Volatile Organic Compounds. Volume 1.
EPA-450/2-27-028. Office of Air Quality Planning and Standards.
Research Triangle Park, NC. September 1980.
Walden Research Division of Abcor. Methodologies for Countvwide
Estimation of Coal, Gas, and Organic Solvent Consumption. U.S.
Environmental Protection Agency, Office of Air Quality Planning and
Standards. Research Triangle Park, NC. December 1975.
GCA Technology Division, Inc. Area Source Documentation for the
1985, National Acid Precipitation Assessment Program Inventory (Draft
Report). U.S. Environmental Protection Agency, Air and Engineering
Research Laboratory. Research Triangle Park, NC. September 1986.
Mannsville Chemical Products Corporation.
Synopsis. Cortland, NY.
Chemical Products
6. Schnell Publishing Company. Chemical Profiles. Chemical Marketing
Reporter (Weekly). New York, NY.
7. U.S. Department of Energy. Petroleum Marketing Monthly. Energy
Information Administration (Monthly). Washington, DC.
8. U.S. International Trade Commission. Synthetic Organic Chemicals,
Washington, DC.
9. U.S. Department of Commerce. County Business Patterns. Bureau of
the Census. Washington, DC. 1982.
10. U.S. Environmental Protection Agency. Emission Inventory Workshop,
Volume II. EPA 450/3-78-042b. Research Triangle Park, NC. 1978.
11• Compilation and Speciation of National Emission Factors for Commercial/
Consumer Solvent Use. EPA-450/2-89-008, U. S. Environmental Protection
Agency, Research Triangle Park, NC, March 1989.
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12. Air Emissions Species Manual, Volume I: Volatile Organic Compound
(VOC) Species Profiles And Volume II: Particulate Matter (PM)
Species ManuanEPA-450/2-88-003a and b, U. S. Environmental
Protection Agency, Research Triangle Park, NC, April 1988.
13. Procedures for the Preparation of Emission Inventories of Volatile
Organic Compounds, Volume II: Emission Inventory Requirements for
Photochemical Air Quality Simulation Models. EPA-450/4-79-018,
Office of Air Quality Planning and Standards, Research Triangle
Park, NC, September 1979.
14. Residential and Commercial Area Source Emission Inventory Methodology
for the Regional Air Pollution Study.EPA-450/3-75-008, EPA Contract
No. 68-02-1003, Environmental Science and Engineering, Inc.,
Gainesville, FL, March 1973.
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3. HEATING (INCLUDING WASTE OIL COMBUSTION)
3.1 General
The combustion of fossil fuels and wood to generate heat produces
emissions of a variety of air toxics including volatile organic
compounds, metals, and polycyclic organic matter (POM). Emissions from
larger sources such as electric utilities and major industrial and
commercial/institutional boilers are typically included in a point source
inventory. Area source emissions from heating occur from fuel combustion
in small stationary sources. Emissions from smaller sources can be
organized into three major area source categories: (1) industrial
(small), (2) commercial/institutional, and (3) residential.
Emissions vary based on the fuel type, burner type, operating
parameters, and pollution controls. It is assumed, unless otherwise
noted, that all area source heating is uncontrolled or at best has
minimal (i.e., mechanical) pollution control equipment. Major fuels used
for area source heating include coal, virgin oil (distillate and resi-
dual), natural gas, wood, and waste oil, which are discussed below.
Coal. Area sources burning coal usually use bituminous and lignite
coal. (Anthracite, bituminous, and lignite coals are all burned in point
source boilers.) Small coal units, common to area sources, are usually
stoker-fired. There are three types of stoker units: (1) spread
stokers, (2) overfeed stokers, and (3) underfeed stokers. Generally
these small boilers have no air pollution controls.
Major toxic pollutants emitted from coal combustion include metals
and organic compounds (including aldehyde and polycyclic organic
matter). Some unburnt combustibles, including numerous organic
compounds, are usually emitted even under proper boiler operating
conditions.
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Virgin Oil. Both distillate and residual virgin oils (hereafter
referred to as distillate and residual oils) are burned in area source
heating units. Distillate oils (fuel oil grade Nos. 1 and 2) are used
mainly in domestic and small commercial applications in which easy fuel
burning is required. Distillates are more volatile and less viscous than
residual oils, having negligible ash and nitrogen contents and usually
containing less than 0.3 weight percent sulfur. Residual oils (grade
Nos. 4, 5, and 6), on the other hand, are used mainly in industrial and
utility boilers and larger commercial applications. Residual oils, which
are produced from the residue left after lighter fractions (gasoline,
kerosene, and distillate oils) have been removed from the crude oil,
usually contain higher quantities of ash, nitrogen, and sulfur. Thus,
burning residual oils generally produces greater concentrations of air
toxics than does burning distillate oils.
Pollutant loadings from fuel oil combustion are also influenced by
the type (tangential, wall, etc.) and size of the boiler, firing and
loading practices, and equipment maintenance . If a boiler unit is
operated improperly or is poorly maintained, the concentrations of toxic
pollutants may increase by several orders of magnitude.
Natural Gas. Natural gas is often used as a fuel in heating units to
produce heat in small industrial boilers and domestic and commercial
space heaters. Because natural gas is a gaseous, homogenous fluid, the
effective operation of the combustion unit is more easily achieved with
its use.
Even though natural gas is a relatively clean fuel, some emissions do
occur from the combustion reaction. For example, improper operating
conditions, including poor mixing and insufficient air, may cause
increased amounts of formaldehyde, polycyclic organic matter, and other
pollutants to be emitted.
6/88 -. HEATING (INCLUDING WASTE OIL COMBUSTION) 3-2
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
It is assumed that no emission controls are used for area sources
burning natural gas.l
Wood. The combustion of wood, primarly in residences, can be a
significant source of air toxics, most notably polycyclic organic matter.
As with other fuel combustion technologies, emissions vary depending on
the characteristics of the fuel burned (e.g., moisture content, wood
type), the operating parameters (most notably the fuel:air ratio),
combustion unit (fireplace, catalytic stove, noncatalytic stove), and
wood load.
Wood stoves are commonly used as space heaters to supplement
conventional heating systems in residences. They are increasingly found
as the primary source of heat, as well.
Because of differences in both the magnitude and the composition of
emissions from wood stoves, four different categories of stoves should be
considered when estimating emissions of the conventional noncatalytic
wood stove, the noncatalytic low emitting wood stove, the pellet fired
noncatalytic wood stove, and the catalytic wood stove.
Among these categories there are many variations in wood stove
design and operation characteristics.
The conventional stove category comprises all stoves without catalytic
combustors not included in the other noncatalytic categories. Stoves of
many different airflow designs, such as updraft, downdraft, crossdraft,
and S-flow, may be in this category.
"Noncatalytic low emitting" wood stoves are those having no catalyst
and meeting EPA certification standards.
Pellet fired stoves are fueled with pellets of sawdust, wood products
and other biomass materials pressed into manageable shape and size. These
3/89 ' HEATING (INCLUDING WASTE OIL COMBUSTION) 3-3
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
stoves have a specially designed or modified grate to accommodate this type
of fuel.
Catalytic stoves are equipped with a ceramic or metal honeycomb
material, called a combustor or converter that is coated with a noble
metal such as platinum or palladium. The catalyst material reduces the
ignition temperature of the unburned hydrocarbons and carbon monoxide in
the exhaust gases, thus augmenting their ignition and combustion at normal
stove operating temperatures. As these comonents of the gases burn, the
temperature inside the catalyst increases to a point where the ignition of
the gases is essentially self-sustaining.
Waste Oil. Approximately 1.1 billion gallons of waste oil are
generated annually in the United States. This used oil is produced by a
range of sources such as repair shops, service stations, airports,
shipyards, and recycling centers. Additionally, spill cleanup and tank
cleaning contribute to waste oil generation. A major portion of this
waste oil, 400 to 660 million gallons, is burned in boilers, kilns,
diesel engines, and waste oil heaters. Ninety-two percent of the oil
that is burned is burned in boilers. Combustion represents the largest
single use of waste oil, with the remainder being re-refined, used as
2
dust suppressants, landfilled, or dumped.
The major concern about using waste oil as fuel is related to
increased emissions of air toxics, as a result of contamination of the
oil. Available literature indicates that air emissions are dependent on
the type of combustion unit, the waste oil composition, operating
parameters, and the type of air pollution controls in place.
Oil-fired boilers consuming waste oil include small residential
boilers, intermediate commercial and institutional boilers, and large
industrial boilers. Typically, industrial boilers are larger in size and
achieve high combustion efficiency at higher burner temperatures; the
factors that affect the quality of combustion are not as carefully
controlled in smaller boilers. These conditions impose a tremendous
3/89 HEATING (INCLUDING WASTE OIL COMBUSTION) 3-4
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
variability in the level of metal emissions from boilers, the average
metal emissions ranging from 31 to 75 percent of the original metal
feed. However, to be on the conservative side, a 100 percent emission
rate for metals could be assumed.
Methods for estimating emissions of air toxics from industrial,
commercial, institutional, and residential area source burning of coal,
virgin oil, wood, and natural gas are discussed in Sections 3.1 through
3.3. An approach for estimating emissions from waste oil combustion is
described in Section 3.4.
A method for estimating the quantities of fuel burned by stationary
area sources (activity levels) has been documented by GCA Technologies,
3
Inc. Portions of that document are incorporated directly into this
manual (with approval from Dale-Pahl, the EPA Project Officer).
Secondary references cited in Reference 3 have been cited in this manual,
as well, so that the reader can obtain additional information if needed.
Emission factors have been compiled for each heating category, along
with example calculations to demonstrate the application of activity
levels .and emission factors to estimate countywide pollutant loads. In
addition, thermal equivalents for various fuels and densities of fuels
are presented in Tables 3-1 and 3-2, respectively, to help in conversions
in estimating emissions.
The EPA has developed a VOC and particulate spectatton manual4 which
contains factors for a number of point and area source categories, including
heating, that can be used to supplement factors provided in this manual.
Many of those factors may be incorporated, with mtnor revisions, into
future versions of this manual.
6/88 "- HEATING (INCLUDING WASTE OIL COMBUSTION) 3-5
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Table 3-1 Thermal Equivalents for Various Fuels
Type of fuel
8TU (gross)
kcal
Solid fuels
Bituminous coal
Anthracite coal
Wood
Liquid fuels
Residual fuel oil
Distillate fuel 011
Gaseous fuels
Natural gas
(21.0 to 28.0) x 10D/ton
25.3 x 10£
21.0 x lOVcord
6.3 x 10D/bbl
5.9 x 106/bbl
1,050/fr
(5.8 to 7.8) x 10D/MT
7 03 x 105/MT
1 47 x 10S/m3
10 x 103/liter
9.35 x 103/liter
9.350/nT
Source: Reference 1.
Table 3-2 Densities of Selected Fuels
Fuel
Fuels
Crude oil
Residual oil
Dlsti Hate 01 1
Gasoline
Natural gas
Wood3
874 kg/m3
944 kg/m3
845 kg/m3
739 kg/m3
673 kg/m3
600 kg/m3
Density
7.30
7.88
7.05
6.17
1.00
38.00
Ib/gal
Ib/gal
Ib/gal
Ib/gal
lb/23.8 ft3
lb/ft3
Average of 10 wood types
Source: Reference 1.
6/88
HEATING (INCLUDING WASTE OIL COMBUSTION)
3-6
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
3.2 Industrial Heating
This category encompasses all industrial stationary combustion
sources that are not typically included as point sources. Traditionally,
boilers larger than 26 GJ/hr are treated in inventories as point
sources. Combustion equipment in this category is used for energy and
steam generation, along with space heating.
Small industrial boilers generally use the following types of fuel:
anthracite coal, bituminous coal, industrial coke, distillate oil and
natural gas.
(1) Activity Levels for Industrial Heating. Walden developed a
procedure for the estimation of state industrial area source consumption
of bituminous coal, distillate oil, residual oil, natural gas, and liquid
petroleum gas (LPG). NEDS' estimates of countywide fuel consumption are
calculated using these procedures and can be used in combination with
emission factors to estimate countywide emissions.
(2) Emission Factors for Industrial Heating. Emission factors to
estimate air toxics emissions from industrial area source heating are
presented in Table 3-3. Emissions can be calculated by multiplying the
activity for each area source by the appropriate emission factor.
Most of the emission factors were taken from Reference 6. It was
conservatively assumed that no controls are in place and that
technologies common to small units typical of area sources (such as coal
stokers) were used. Emissions of ROMs were estimated based on
information provided by ORD, who defined ROMs as the benzene extractable
portion of particulate matter. For each source category e.g. industrial
coal, residential oil, ORD provided a percent of particulate that is
considered to be ROMs for that category.
6/88 \ HEATING (INCLUDING WASTE OIL COMBUSTION) 3-7
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Table 3-3 Emission Factors for Industrial Area Source Heating
Fuel type Pollutant
Anthracite Arsenic
Benzo(a)pyrene
Beryllium
Cadmium
Chromium
Formaldehyde
Lead
Nickel
POMS
Vanadium
Bituminous Coal Arsenic
Benzo(a)pyrene
Beryllium
Cadmium
Chromium
Formaldehyde
Lead
Nickel
POMS
Vanadium
Residual oil Arsenic
Benzo(a)pyrene
Beryllium
Cadmium
Chromium
Formaldehyde
Lead
Nickel
POMS
Emission factor
482 pg/J (2.5 x 10~2 Ib/ton)
0.06 pg/J (3.3 x 10"6 Ib/ton)
0.005 pg/J (9 5 x 10"4 Ib/ton)
17 9 pg/J (9.4 x 104 Ib/ton)
38.3 pg/J (2.1 x 10'3 Ib/ton)
537 pg/J (3 x 10~2 Ib/ton)
4.1 pg/J (2.3 x 10~4 Ib/ton)
68.4 pg/J (3.8 x 103 Ib/ton)
343 pg/J (1.8 x 10~2 Ib/ton)
58.1 pg/J (3.2 x 10"3 Ib/ton)
482 pg/J (2.7 x 10~2 Ib/ton)
0.06 pg/J (3.5 x 10"6 Ib/ton)
18.1 pg/J (1.0 x 10"3 Ib/ton)
17.9 pg/J (1.0 x 10"3 Ib/ton)
38.3 pg/J (2.2 x 10'3 Ib/ton)
537.0 pg/J (3 x 10~2 Ib/ton)
4.1 pg/J (2.4 x 10"4 Ib/ton)
68.4 pg/J (4.0 x 10"3 Ib/ton)
537 pg/J (3.0 x 10~2 Ib/ton)
58.1 pg/J (3.4 x 10"3 Ib/ton)
47.3 pg/J (1.6 x 10"2 lb/1.000 gal)
0.13 pg/J (4.52 x 10"5 lb/1.000 gal)
0.2 pg/J (7.0 x 10"5 lb/1,000 gal)
1.9 pg/J (6.6 x 10~4 lb/1,000 gal)
71.3 pg/J (2.5 x 10"2 lb/1.000 gal)
28.6 pg/J (1.0 x 10"2 lb/1,000 gal)
94.4 gh/J (3.3 x 10"2 lb/1.000 gal)
4.1 pg/J (1.42 x 10"3 lb/1,000 gal)
31.4 pg/J (1.0 x 10"2 lb/1,000 gal)
207 pg/J (7.0 x 10"2 lb/1.000 gal)
Reference
6
6
6
6
6
6
6
7. 1
6
6
6
6
6
6
6
6
6
7. 1
6
6
6
6
6
6
6
6
6
6
7. 1
Comment
Stoker
(uncontrolled)
Stoker
Stoker
Stoker
Stoker
Stoker
Assumed POMS are
0.2% of TSP for
Anthracite stoker
Stoker
(uncontrolled)
Stoker
(uncontrolled)
Stoker
Stoker
Stoker
Stoker
Assumed POMS are
0.2% of TSP for
Bituminous stoker
Tangential, Wall
Tangential
Wall
Tangential, Wall
Tangential, Wall
Tangential, Wall
Tangential, Wall
Tangential, Wall
Assumed POMS are
Vanadium
1000 pg/J (3.5 x 10"1 lb/1.000 gal)
0.7% of TSP
Tangential, Wall
6/88
HEATING (INCLUDING WASTE OIL COMBUSTION)
3-8
-------
PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Table 3-3 (Continued)
Fuel type
Natural Gas
Pollutant
Emission factor
Reference
Comment
Oisti 1 late 01 1 Arsenic
Benzo(a)pyrene
Beryllium
Cadmium
Chromium
Formaldehyde
Lead
Nickel
POMS
Vanadium
47
0.
0.
1.
71
28
94
4.
31
43
.3
13
2
9
.3
.6
.4
1
.4
.3
1000
pg/J
pg/J
pg/J
pg/J
pg/J
pg/J
pg/J
pg/J
pg/J
pg/J
pg/J
(i
(4
(6.
(6.
(2
(9
(3
(1.
(1
(1
(3
.53
.23
5 x
2 x
.3
.3
.3
33
.02
.4
.2
x 10"2
x 10"5
lb/ 1.000
lb/1,000
gal)
gal)
10"5 lb/1,000 gal)
10~4 lb/1,000 gal)
x 10"2
x 10"3
x 10"2
x 10"3
x 10"2
x lO'2
x 10"1
lb/1,000
lb/1,000
lb/1,000
lb/1,000
lb/1.000
lb/1,000
lb/1,000
gal)
gal)
gal)
gal)
gal)
gal)
gal)
6
6
6
6
6
6
6
6
6
7, 1
6
Tangential ,
Tangential
Wall
Tangential ,
Tangent lal ,
Tangential ,
Tangential,
Tangential ,
Assumed POMS
0.7% of TSP
Tangential ,
Wall
Wall
Wall
Wall
Wall
Wall
are
Wall
FormaIdehyde
2.0 x 10°lb/million cubic feet
16
Note: pg/J indicates picograms per joule.
6/88
HEATING (INCLUDING WASTE OIL COMBUSTION)
3-9
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
3.3 Commercial and Institutional Heating
The commercial and institutional heating source category includes all
stationary fuel combustion sources that are not included under residen-
tial sources, industrial sources, power plants, or commercial point
sources. Major commercial/institutional area sources include hospitals,
hotels, laundries, schools, and universities.
Activity levels for commercial/institutional heating. Quantities of
fuels burned by industry are estimated for anthracite coal, bituminous
coal, distillate oil, residual oil, and natural gas using the methodology
described by Wai den.5 The NEDS data base estimates commercial/institutional
fuel consumption by fuel type, using these procedures. These values can
be multiplied by the appropriate emission factor listed in Table 3-4 to
estimate emissions.
A methodology for estimating waste oil consumption in residential,
institutional, and commercial (RIC) and industrial boilers can be found
in Section 3.4. It is estimated that 23 percent of the waste oil that is
burned in the United States is burned in RIC boilers.
Emission factors for commercial/institutional heating. Emission
factors for commercial and institutional heating are presented in Table
3-4. Emissions can be calculated by multiplying the activity for each
area source by the appropriate emission factor.
Most of the emission factors were taken from Reference 6. It was
conservatively assumed that no controls are in place and that
technologies common to small units typical of area sources (such as coal
stokers) were used. Emissions of ROMs were estimated based on
information provided by ORD, who defined ROMs as the benzene extractable
portion of particulate matter. For each source category e.g. industrial
coal, residential oil, ORD provided a percent of particulate that is
considered to be POMs for that category.
6/88 " HEATING (INCLUDING WASTE OIL COMBUSTION) 3-10
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Table 3-4 Emission Factors for Commercial/Institutional Area Source Heating
Fuel type Pollutant
Anthracite coal Arsenic
Benzo(a)pyrene
Beryllium
Cadmium
Chromium
Formaldehyde
Lead
Nickel
POMS
Vanadium
Bituminous coal Arsenic
Benzo(a)pyrene
Beryl 1 lum
Cadmium
Chromium
Formaldehyde
Lead
Nickel
POMS
Vanadium
Residual oil Arsenic
Benzo(a)Pyrene
Beryl 1 lum
Cadmium
Chromium
Formaldehyde
Lead
Nickel
POMS
Emission factor
482 pg/J (2.7 x 1~2 Ib/'ton)
4.7 pg/J (2 6 x 10"4 Ib/ton)
18.1 pg/J (9.5 x 10~4 Ib/ton)
12.9 pg/J (7.1 x 10"3 Ib/ton)
38.3 pg/J (2 1 x 10"3 Ib/ton)
567 pg/J (3 x 10~2 Ib/ton)
4.1 pg/J (2.3 x 10"4Jb/ton)
68.4 pg/J (3.8 x 10"3 Ib/ton)
1486 pg/J (7.8 x 10~2 Ib/ton)
51.8 pg/J (2.8 x 10"3 Ib/ton)
482 pg/J (2.8 x 10~2 Ib/ton)
4.7 pg/J (2.7 x 10~4 Ib/ton)
18.1 pg/J (1.0 x 10~3 Ib/ton)
12.9 pg/J (7.5 x 10"4 Ib/ton)
38.3 pg/J (2.2 x 10"3 Ib/ton)
537.0 pg/J (3.0 x 10~2 Ib/ton)
4.1 pg/J (2.4 x 10"4Jb/ton)
68.4 pg/J (4.0 x 10"3 Ib/ton)
543 pg/J (3 x 10"2 Ib/ton)
51.8 pg/J (3.0 x 10"3 Ib/ton)
47.3 pg/J (1.6 x 10"2 lb/1,000 gal)
0.4 pg/J (1.4 x 10"4 lb/1,000 gal)
0.1 pg/J (3.5 x 10"5 lb/1.000 gal)
71.8 pg/J (2.5 x 10~2 lb/1.000 gal)
50.0 pg/J (1.7 x 10"2 lb/1,000 gal)
94.4 pg/J (3.3 x 10"2 lb/1.000 gal)
4.1 pg/J (1.4 x 10"3 lb/1.000 gal)
804 pg/J (2.7 x 10"1 lb/1,000 gal)
40 pg/J (1 4 x 10"2lb/l,000 gal)
Reference
6
6
6
6
5
6
6
7. 1
6
6
6
6
6
6
6
6
6
7, 1
6
6
6
6
6
6
6
6
6
7, 1
Comment
Stoker
Stoker
Stoker
Stoker
Stoker
Stoker
Stoker
Assumed POMS are
0.2% of TSP
Stoker
Stoker
Stoker
Stoker
Stoker
Stoker
Stoker
Stoker
Assumed POMS
0.2% of TSP
Stoker
Tangential ,
Tangent lal ,
Tangential ,
Tangential ,
. Tangential,
Tangential ,
Tangential,
Assumed POMS
are
Wall
Wall
Wall
Wall
Wall
Wall
Wall
are
Vanadium
3660 pg/J (1.2 lb/1,000 gal)
0.7% of TSP
Tangential, Wall
6/88
HEATING (INCLUDING WASTE OIL COMBUSTION)
3-11
-------
PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Table 3-4 (Continued)
Fuel type
Natural Gas
Pollutant
Emission factor
Reference
Comment
Disti Hate 01 1 Arsenic
Benzo(a)Pyrene
Beryllium
Cadmium
Chromium
Formaldehyde
lead
Nickel
POMS
Vanadium
47.3 pg/J (1.5 x 10~2 lb/1,000 gal)
0 4 pg/J (1.3 x 10"4 lb/1.000 qal)
c
0.1 pg/J (3.3 x 10~J lb/1.000 gal)
71.8 pg/J (2.3 x 10"2 lb/1,000 gal)
50.0 pg/J (1.6 x 10~2 lb/1.000 gal)
94 4 pg/J (3.3 x 10"2 lb/1,000 gal)
4.1 pg/J (1.3 x 10"J lb/1,000 gal)
112 pg/J (3 6 x 10"2 lb/1,000 gal)
44 pg/J (1 4 x 10~2 lb/1,000 gal)
30 pg/J (9.8 x 10~2 lb/1,000 gal)
6
6
6
6
'6
6
6
6
7. 1
6
Tangential ,
Tangential ,
Tangential ,
Tangential ,
Tangential ,
Tangential,
Tangential,
Assumed POMS
0.7% of TSP
Tangential ,
Wall
Wall
Wall
Wall
Wall
Wall
Wall
are
Wall
Formaldehyde
6.3 x 10 Ib/million cubic feet
Note: pg/J indicates picograms per joule
6/88
HEATING (INCLUDING WASTE OIL COMBUSTION)
3-12
-------
PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
3.4 Residential Heating
The residential heating category includes emissions for residential
activities that use fuel for water heating, space heating, and cooking.
Emissions contributed by residential fuel consumption are broken down
into six categories according to the type of fuel. Fuel types included
are anthracite coal, bituminous coal, distillate oil, residual oil,
natural gas, and wood. For each of the listed fuel types, activity
levels measured by fuel quantity consumed in weight or volume units are
multiplied by emission factors listed in Table 3-5 to obtain emissions
estimates. Methodologies for activity levels follow.
Activity levels for residential heating. Total county residential
consumptions of coal, oil, and natural gas are calculated based on
algorithms derived by Walden. It should be noted that residential
Q
residual oil consumption is assumed to be negligible. Residential
wood consumption provided in NEDS also are based on Estimates of U.S.
Wood Energy Consumption. updated annually using regional data from
Q
the Annual Housing Survey. The NEDS data base provides estimates of
consumption based on these procedures.
Emission factors for residential heating. Air toxic emission factors
are presented in Table 3-5. Emissions can be estimated by multiplying
the appropriate factor from Table 3-5 by the activity for the area of
concern.
Most of the emission factors were taken from Reference 6. It was
conservatively assumed that no controls are in place and that
technologies common to small units typical of area sources (such as coal
stokers) were used. Emissions of ROMs were estimated based on
information provided by ORD, who defined ROMs as the benzene extractable
portion of particulate matter. For each source category e.g. industrial
coal, residential oil, ORD provided a percent of particulate that is
considered to be ROMs for that category..
6/88 -. HEATING (INCLUDING WASTE OIL .COMBUSTION) 3-13
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Table 3-5 Emission Factors for Residential Area Source Heating
Fuel type Pollutant
Bituminous coal Arsenic
Benzo(a)pyrene
Beryllium
Cadmium
Chromium
Formaldehyde
Lead
Nickel
POMS
Vanadium
Anthracite coal Arsenic
Benzo(a)pyrene
Beryllium
Cadmium
Chromium
Lead
Nickel
Formaldehyde
POMS
Vanadium
Disti Hate 01 1 Arsenic
Benzo(a)pyrene
Beryl lium
Cadm i urn
Chromium
Formaldehyde
Lead
Nickel
POMS
Vanadium
Emission factor
717 pg/J (4.2 x 10'2 Ib/ton)
108 pg/J (6.0 x 10"3 Ib/ton)
7.2 pg/J (4.2 x 10"4 Ib/ton)
17.9 pg/J (1.0 x 10"3 Ib/ton)
71.3 pg/J (4.1 x 10~3 Ib/ton)
43.0 pg/J (2.4 x 10"3 Ib/ton)
359 pg/J (2.1 x 10"2 Ib/ton)
71.8 pg/J (4.2 x 10"3 Ib/ton)
221,960 pg/J (12.4 Ib/ton)
71.8 pg/J (4.2 x 10"3 Ib/ton)
166 pg/J (9.86 x 10~3 Ib/ton)
106 pg/J (6.2 x ID"3 Ib/ton)
6.6 pg/J (3.9 x 10~4 Ib/ton)
6.6 pg/J (3.9 x 10"4 Ib/ton)
56.2 pg/J (3.3 x 10"3 Ib/ton)
265 pg/J (1.6 x 10'2 Ib/ton)
66.2 pg/J (3.9 x 10"3 Ib/ton)
40.9 pg/J (2.4 x 10"3 Ib/ton)
141,351 pg/J (8.3 Ib/ton)
56.2 pg/J (3.3 x 10'3 Ib/ton)
1.5 pg/J (5.1 x 10~4 lb/1,000 gal)
0.1 pg/J (3.4 x 10"5 lb/1,000 gal)
1.9 pg/J (6.4 x 10"4 lb/1.000 gal)
11 pg/J (3.7 x 10"3 lb/1.000 gal)
1.1 pg/J (3.7 x 10~4 lb/1,000 gal)
94.4 pg/J (3.3 x 10"2 lb/1.000 gal)
9.5 pg/J (3.2 x 10'3 lb/1,000 gal)
103 pg/J (3.5 x 10"2 lb/1,000 gal)
2,451 pg/J (8.2 x 10"1 lb/1.000 gal)
10.1 pg/J (3.4 x 10"3 lb/1,000 gal)
Reference Comment
6
6
6
6
6
6
6
6
7, 1 Assumed POMS are
83% of TSP
6
6
6
6
6
6
6
6
6 Assumed same as
Bituminous
7, 1 Assumed POMS are
83% of TSP
6
6
6
6
6
6
6 Assumed same as
commercial
distillate
6
6
7. 1 Assumed POMS are
33% of TSP
6
6/88
HEATING (INCLUDING WASTE OIL COMBUSTION)
3-14
-------
PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Table 3-5 (Continued)
Fuel type
Wood-woodstoves
Wood-fireplaces
Natural Gas
Pollutant
Acetaldehyde
Acrolein
Arsenic
Benzo(a)pyrene
Beryl 1 lum
Formaldehyde
Nickel
POMS
Acetaldehyde
Acrolein
Arsenic
Benzol a)pyrene
Beryllium
Cadmium
Formaldehyde
Nickel
POMS
Formaldehyde
Emission factor
0.24 Ib/ton
7.3 x 10"2 Ib/ton
3.6 x 10"4 Ib/ton
3.4 x IO"6 Ib/ton
2 9 x 10"7 Ib/ton
'
0.48 Ib/ton
6.0 x IO"5 Ib/ton
3.4 x 101 Ib/ton •
1.4 Ib/ton
7.3 x 10"2 Ib/ton
2.6 x iO"4 Ib/ton
3.0 x IO"6 Ib/ton
2.9 x IO"7 Ib/ton
7.1 x IO"5 Ib/ton
3.0 Ib/ton
3.3 x IO"3 Ib/ton
2.3 x IO1 Ib/ton
6.2 Ib/ton million cubic feet
Reference
10
11
10
11
10
6
11
7. 1
6
11
10
11
10
10
6
10
7. 1
8
Comment
Average catalytic
and noncatalyt ic.
Assumed max cured
pine, noncatalytic
Assumed max cured
oak, noncatalytic
Assumed POMS are
83% of TSP for
conventional non-
catalytic
Assumed same as
woodstoves
Assumed POMs are
83% of TSP
Note: pg/J indicates picograms per joule.
6/88
HEATING (INCLUDING WASTE OIL COMBUSTION)
3-15
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PROCEDURES FOR ESTIMATING -AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Table 3-6 Apportionment of Residential Wood Consumption
Between Fireplaces (FP) and Wood Stoves (WS) for the Year 1976
State
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
District of
Columbia
Florida
Georgia
Hawa i i
Idaho
11 1 i no i s
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
AL
AK
AZ
AR
CA
CO
CT
DE
DC
FL
GA
HI
ID
IL
IN
IA
KS
KY
LA
ME
MD
MA
MI
MN
MS
MO
MT
NE
NV
NH
NJ
NM
NY
NC
NO
OH
OK
OR
PA
FP
.08
14
.57
.17
.57
.40
.26
.28
.29
.30
.17
.57
.39
.32
.33
.32
.32
. .16
.29
.04
.29
.25
.19
.11
.16
.19
.40
.32
.56
.04
.40
.73
.25
.30
.33
.32
.45
.13
.40
WS
.92
.86
.43
.83
.43
.60
.74
.72
.71
.70
.83
.43
.61
.68
.67
.66
.68
.84
.71
.96
.71
.75
.81
.89
.84
.81
.60
.68
.44
.96
.60
.27
.75
.70
.67
.68
.55
.87
.60
6/88 "'HEATING (INCLUDING WASTE OIL COMBUSTION) 3-16
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Table 3-6 (Continued)
State FP WS
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
RI
SC
SD
TN
TX
UT
VT
VA
UA
WV
WI
WY
.40
.30
'.30
.05
.29
.42
.04
.30
.13
.30
.19
.40
.24
.60
.70
.70
.95
.71
.58
.96
.70
.87
.70
.81
60
.76
Source: Reference 10.
6/88 - HEATING (INCLUDING WASTE OIL COMBUSTION) 3-17
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
3.5 Waste Oil Combustion
As mentioned earlier, between 400 million and 660 million gallons of
waste oil is burned in boilers, kilns, diesel engines, and waste oil
heaters. Ninety-two percent of the oil that is burned is burned in
boilers, with 77 percent burned in industrial boilers and 23 percent
burned in RIC units. Table 3-7 presents a rough estimate of
state-by-state waste oil consumption.
A number of studies have been performed to characterize the
12
contaminant concentrations in waste oil. Franklin Associates has
provided .a detailed analysis of the typical contaminant concentrations in
waste oil. Extensive sampling was carried out as a part of the study for
each source of oil and its end-use application. The range of contaminant
concentrations determined in the study varied from virtually zero to very
high for most contaminants. In general, this large variation in
contaminant concentration occurs because of (1) the numerous and varied
processes and mechanism that originally contaminated the oil, (2) the
different types of oil, and (3) the various additives that are used to
enhance the performance characteristics of the oil.
Waste oil is often pretreated prior to burning. The pretreatment
includes (1) reprocessing of the waste oil, (2) re-refining of the waste
oil, and (3) blending of virgin or clean fuel oil with the waste oil. It
has been estimated that approximately 44 percent of the total waste oil
12
generated in 1982 underwent some form of processing.
Median concentrations of metals and organics in waste oil, the
fraction emitted, and emissions factors based on population and fuel
usage are presented in Table 3-8.
6/88 -. HEATING (INCLUDING WASTE OIL COMBUSTION) 3-18
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PRnrrnURES FOR ESTIMATING AND ALLOCATING
ARE!SOURCE EMISSIONS OF AIR TOXICS
Table 3-7 Waste Oil Consumption by State
State
Alabama
Alaska
Arizona
Cal ifornia
Colorado
Connecticut
Delaware
Florida
Georgia
Hawa i i
Idaho
I Ilinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Total - 429.014
Waste 01 1 burned
(gal Ions)
6,678,000
374,000
5,130.000
36,053,000
6,080.000
3,610,000
1,606,000
10,640,000
8,542,000
608,000
570,000
19,419,000
6,707,000
4.151,000
8,220,000
4.075.000
17,233,000
2 , 098 , 000
6,287,000
8,550,000
24,397,000
7,373,000
4,431,000
13,590,000
969,000
,000 gallons
State
Nebraska
Nevada
New Hampshire
New Mexico
New York
North Carolina
North Dakota
Ohio
Ok lahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington, DC
Washington
West Virginia
Wisconsin
Wyoming
Waste 01 1 burned
(gallons)
5,362,000
1,069,000
855.000
2,563,000
16,503,000
9,856,000
665,000
9,405,000
12.806,000
5,653,000
32,797,000
2.166,000
4,367.000
739,000
10,947,000
43,698.000
2.660.000
470,000
7,429,000
556.000
9.063,000
4,932,000
5,013,000
1,461,000
Source: Communication between Hope Pillsbury, IEMD, EPA, and Eric Males, OSW, EPA, cited in
Reference 13.
6/88
HEATING (INCLUDING WASTE OIL COMBUSTION)
3-19
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
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6/88
HEATING (INCLUDING WASTE OIL COMBUSTION)
3-20
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Test data indicate destruction efficiencies for organics ranging from
97 to 99.99 percent. Higher combustion temperatures in industrial
boilers dictate higher destruction efficiencies. Hence, a 99.9 percent
destruction efficiency for organics in industrial boilers is a reasonable
estimate. In residential, institutional and commercial (RIC) boilers,
where the units tend to be less efficient, a 99 percent destruction
efficiency for organics is assumed to be representative.
Because the boilers using waste oil as a fuel vastly differ in their
characteristics, simple quantification of boiler population, fuel
blending, or oil consumption is not practical. OSW has estimated that
about 100 million gallons of waste oil are burned in RIC boilers
(23 percent) and about 330 million gallons are burned in industrial
boilers (77 percent). It has also been indicated that waste oil is more
likely to be burned at facilities that currently burn residual oil than
14
at those that burn distillate oil.
Methodology Options. Toxic emissions that result from the combustion
of waste oil can be estimated when one of the following is known or can
be estimated:
• The quantity of waste oil burned in the study area;
• The population of a particular county, state, or region; or
• The quantity of waste oil burned for a particular state, county,
or region can be estimated.
Method 1: Estimates based on fuel consumption data
This approach is preferred when data on countywide consumption are
available or can be collected by surveying users or distributors. Once
data on the quantity of waste oil burned in the county or state are
known, the estimation of emissions is straightforward. The emission
6/88 - HEATING (INCLUDING WASTE OIL COMBUSTION) 3-21
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
factor (Table 3-8) that relates the quantities of emissions emitted per
1,000 gallons of waste oil burned is multiplied by the quantity of waste
oil burned in the county or state. For example, if the county burns
74,290 gallons of waste oil annually and the emission factor from Table
2.2-8 is 3.6 kg Pb/1,000 gallons of waste oil burned/year, then the
amount of lead emitted can be estimated as follows:
Pb emitted = 74.290 (thousand gallons of waste oil burned) 3.6 kg Pb
1000 gallons waste
oil burned per year
Pb emitted = 267 kg/yr
Method 2: Estimates based on population (per capita estimates).
Population data can be collected from the U.S. Census Bureau. Air
toxic emissions can be estimated by applying the per capita emission
factors from Table 3-8 which relate the quantity emitted per 1,000
persons. For example, to estimate the quantity of arsenic emitted in a
county of 180,375 persons, use the emission factor from Table 3-8 to
estimate the amount of arsenic emitted annually.
As emitted = 180.4 (1,000persons) x 3.5 x 10"2 kg As/1,000 persons/yr
As emitted =6.3 kg/yr.
Method 3: Estimates based on virgin oil consumption
This method assumes that quantities of waste oil burned in a given area
is directly proportional to the quantity of residual oil that is burned.
STEP 1: Determine from NEDS or other sources state and county quantities
of residual oil burned in RIC and industrial boilers.
6/88 - HEATING (INCLUDING WASTE OIL COMBUSTION) 3-22
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
STEP 2: Determine quantity of waste oil burned in each county, assuming
that the quantity of waste oil burned in the county is directly
proportional to the quantity of residual oil burned in the
county.
WOC = (CR + Ci + CCI) x WOS
SR H- ST + SCI
where
WOQ = annual waste oil burned in the county
CR = annual countywide residential residual oil consumption
Cj = annual countywide industrial residual.oil consumption
CQJ = annual countywide commercial/institutional residual oil
consumption
SR = annual state-wide residential residual oil consumption
Sj = annual state-wide industrial residual oil consumption
SQJ = annual state-wide commercial/institutional residual oil
consumption
W0$ = annual.state-wide waste oil consumption (from Table 3-7).
STEP 3: Calculate the quantity of waste oil burned in residential,
commercial and industrial boilers assuming that 23% of the waste
oil that is burned is burned in RIC boilers, and 77% is burned
in industrial boilers.
WOR = WOC x 0.23 x CR
CCI
WOCI = WOC x 0.23 x CCI
where
CCI + CR
WOj = WOC x 0.77
waste oil burned in residential boilers
.._U1 waste oil burned in commercial/institutional boilers
WOj = waste oil burned in industrial boilers
6/88 - HEATING (INCLUDING WASTE OIL COMBUSTION) 3-23
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
STEP 4: Obtain the emission factor from Table 3-8 for the contaminant in
question. (Note: this factor should relate kg/1,000 gallons
waste oil burned.)
STEP 5: Compute metal or organic emission by multiplying the quantity of
waste oil .burned in the county by the emission factor obtained
in Step 4.
Ep (WOj + WOCI + WOR) x EFp
where
Ep = annual emission of pollutant p kg/yr
EFp = emission factor for pollutant p from Table 3-8.
3.6 Example Calculations
Example calculations for estimating toxic emissions from virgin fuel
combustion are shown below. Examples of waste oil emission calculations
are contained in Section 3.4.
Example Calculation 1
The following calculation estimates the area source emission of
formaldehyde from burning distillate oil in commercial/industrial
boilers. The consumption of commercial/institutional distillate oil for
a particular county in one year is reported as 12,270,000 gallons (12,270
thousand gallons/year). The emission factor for formaldehyde for
distillate oil from Table 3-4 is 0.033 lb/1,000 gallons.
6/88 : HEATING (INCLUDING WASTE OIL COMBUSTION) 3-24
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
The calculation is as follows:
12.270 thousand gallons X 0.033 1b Formaldehyde = 405 Ib/year
year thousand gallons
For the county in question, the estimated formaldehyde emission from
commercial/institutional boilers burning distillate oil is 405 Ib/yr.
Other pollutants in Table 3-4 can be estimated in a similar manner
for commercial/institutional boilers. Emissions from the burning of
other fossil fuels in residential, industrial, and commercial/
institutional can be estimated using a similar methodology as well.
Example Calculation 2
This example illustrates the calculation of acetaldehyde emissions
due to burning of wood in woodstoves and fireplaces in a county in
Maryland. The residential wood consumption in this county for one year
is 1,000 tons. The woodstove/fireplace apportionment from Table 3-6 for
Maryland is 0.71 for woodstoves and 0.29 for fireplaces (i.e., 71% of the
wood consumed is burned in woodstoves and 29% in fireplaces). The
acetaldehyde emission factors from'Table 3-5 are 0.24 Ib/ton for
woodstoves and 1.4 Ib/ton for fireplaces.
The calculations are as follows:
Woodstoves
1,000 ton X 0.71 X 0.24 1b = 170 Ib/yr
year ton
6/88 - HEATING (INCLUDING WASTE OIL COMBUSTION) 3-25
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Fireplaces
1.000 ton X 0.29 X 1.4 1b = 406 Ib/yr
year ton
The estimated acetaldehyde emissions for the county in question are
170 Ib/yr from woodstoves and 406 Ib/yr for fireplaces. Other pollutants
in Table 3-5 can be estimated in a similar manner.
3.7 Methods to Apportion Countywide Emissions from Heating
As described in Section 1.0 and Appendix A, when performing air
dispersion modeling, it is generally recommended that countywide
emissions be distributed within the study area into rectangular area
source grid cells reflecting spatial variations in activity and
emissions. Similarly, temporal in activities can be factored into the
modeling to reflect seasonalor diurnal fluctuations in emissions.
Modeling results would then reflect on-going activities in that portion
of the county, e.g., residential heating in the winter, commercial
solvent usage during working hours on weekdays.
There are three alternative approaches that can be used in spatially
distributing emission: (1) population, i.e., the magnitude of emissions
within a grid are directly proportional to the population living in the
grid, (2) land area, i.e., emissions from a countywide area source are
assumed to be uniform throughout the county and are distributed based on
the size of the area source grid, and (3) landuse patterns that assume
that certain area source activities, most likely to occur in certain
areas of the county, e.g., commercial, residential, or industrial.
6/88 HEATING (INCLUDING WASTE OIL COMBUSTION) 3-26
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
In apportioning emissions from heating any of these methods may be
appropriate. Land area and population data can be readily obtained and
applied as described in Appendix A. Land use data, available from the
U.S. Geological survey and other sources can be used in combination with
the spatial resolution for heating to distribute emissions based on the
type of activity being performed, as shown in Table 3-9.
Estimated seasonal, daily, and hourly temporal resolution for heating
are also included in Table 3-9, and can be used with the annual
countywide emissions data to estimate temporal variations.
6/88 - HEATING (INCLUDING WASTE OIL COMBUSTION) 3-27
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Table 3-9 Spatial and Temporal Resolution
for Heating and Waste Oil Combustion
Fuel Combustion, Industrial
15
Spatial Resolution
Surrogate indicator:
Information source(s):
industrial areas (codes 13 and 15)
land use map
Temporal Resolution
Seasona 1 :
Daily:
Hourly:
uniform through the year
Monday through Saturday
80 percent from 0700 to 1800 and 20
percent from 1800 to 2400, otherwise
zero
Fuel Combustion, Commercial/Institutional
15
Spatial Resolution
Surrogate indicator:
Information source(s):
industrial areas (codes 12 and 15)
land use map and Reference 16
Temporal Resolution
Seasona 1:
Daily:
Hourly:
Fuel Combustion, Residential
15
Spatial Resolution
Surrogate indicator:
Information source(s):
25 percent uniform through the year and
75 percent uniform during the months
that have an average temperature of
688°F or less
95 percent Monday through Saturday
90 percent from 0600 to 2400 and 10
percent from 2400 to 0600
residential area (codes 11, 16, and
17); dwelling units
land use map
Temporal Resolution
Seasonal:
Daily:
Hourly:
10 percent uniform through the year and
90 percent uniform during the months
that have an average temperature of
688°F or less
uniform through the week
uniform through the day
6/88
HEATING (INCLUDING WASTE OIL COMBUSTION)
3-28
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Table 3-9 (Continued)
Waste Oil Combustion (Industrial)
Spatial Resolution
Surrogate indicator:
Information source(s):
industrial areas (codes 13 and 15)
land use map
Temporal Resolution
Seasonal:
Daily:
Hourly:
uniform through the year
uniform Monday through Saturday
80 percent from 0700 to 1800, 20
percent from 1800 to 2400, otherwise
zero
Waste Oil Combustion (Residential/Institutional/Commercial)
Spatial Resolution
Surrogate indicator:
residential, institutional, and
commercial areas (land use codes 11,
12, 15, 16, 17)
Information source(s): land use maps
Temporal Resolution
Seasona1:
Daily:
Hourly:
25 percent uniform through the year and
75 percent uniform during the months
that have an average temperature of
688°F or less
95 percent Monday through Saturday
90 percent from 0600 to 2400, 10
percent from 2400 to 0600
6/88
HEATING (INCLUDING WASTE OIL COMBUSTION)
3-29
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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REFERENCES
1. U.S. Environmental Protection Agency. Compilation of Air Pollutant
Emission Factors. Volume 1: Stationary Point and Area Sources
(AP-42). Fourth Edition. Office of Air Quality Planning and
Standards. Research Triangle Park, NC. September 1985.
2. U.S. Environmental Protection Agency. A Risk Assessment of Waste Oil
Burning in Boilers and Space Heaters. Contract No. 68-02-3173.
Office of Solid Waste. Washington, DC. 1984.
3,
GCA Technology Division, Inc. Area Source Documentation for the 1985
National Acid Precipitation Assessment Program Inventory Draft
Report. U.S. Environmental Protection Agency, Air and Energy
Engineering Research Laboratory. Research Triangle Park, NC.
September 1986.
4. Air Emissions Species Manual, Volume I: Volatile Organic Compound
(VOC) Species Profiles And Volume II: Particulate Matter (PM) Species
Manual. EPA-450/2-88-Q03a and b, U. S. Environmental Protection
Agency, Research Triangle Park, NC, April 1988.
5. Walden Research Division of Abcor. Methodologies for Countvwide
Estimation of Coal, Gas, and Organic Solvent Consumption.
EPA-450/3-75/06. U.S. Environmental Protection Agency, Office of Air
Quality Planning and Standards. Research Triangle Park, NC.
December 1975.
6. U.S. Environmental Protection Agency. Preliminary Compilation of Air
Pollutant Emission Factors for Selected Air Toxic Compounds. Office
of Air Quality Planning and Standards. Research Triangle Park, NC.
7. Lewtas, J. Information provided to Versar, Inc. and the Regulatory
Integration Division of EPA's Office of Policy and Resource
Management. U.S. Environmental Protection Agency. Office of
Research and Development. Research Triangle Park, NC. September
1987.
8. JRB, Inc. Materials Balance - Formaldehyde. Revised Draft Report.
U.S. Environmental Protection Agency. Office of Pesticides and Toxic
Substances. Washington, DC. January 1982.
9. Walden Research Corporation. Development of a Methodology to
Allocate Liquid Fossil Fuel Consumption by County. EPA-450/3-74-021.
U.S. Environmental Protection Agency, Office of Air Quality Planning
and Standards. Research Triangle Park, NC. March 1974.
6/88 HEATING (INCLUDING WASTE OIL COMBUSTION) 3-30
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
REFERENCES
10. D.G. De Angelis, D.S. Ruffin, J.A. Peters, and R.B. Reznik. Source
Assessment: Residential Combustion of Wood. EPA-600/2-80-042b. U.S.
Environmental Protection Agency, Office of Research and Development.
Washington, DC 1980.
11. Engineering Sci-ence, Inc. Emission Factor Documentation for AP-42:
Section 1.10. Residential Wood Stoves. (Draft). U.S. Environmental
Protection Agency. Office of Air Quality Planning and Standards.
Research Triangle Park, NC. May 1987.
12. U.S. Environmental Protection Agency. Composition and Management of
Used Oil Generated in the United States. Office of Solid Waste and
Emergency Response. Washington, DC. 1984.
13. GCA Technology. Locating and Estimating Air Emissions from Sources
of Chlorobenzenes. EPA-450/4-84-007m. U.S. Environmental Protection
Agency, Office of Air Quality Planning and Standards. Research
Triangle Park, NC. 1986.
14. Versar Inc. Hazardous Air Pollutants, An Exposure and Preliminary
Risk Appraisal for 35 U.S. Counties. U.S. Environmental Protection
Agency. Washington, DC. 1984.
15. U.S. Environmental Protection Agency. Procedures for the Preparation
of Emission Inventories for Volatile Organic Compounds. Volume II:
Emission Inventory Requirements for Photochemical Air Quality
Simulation Models. EPA-450/4-79-018. Office of Air Quality Planning
and Standards. Research Triangle Park, NC. September 1979.
16. Mineral Industry Surveys. Sales of Fuel Oil and Kerosene.
6/88 '_ HEATING (INCLUDING WASTE OIL COMBUSTION) 3-31
-------
PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
4. ROAD VEHICLES
4.1 General
Road vehicles are a major source of organic and inorganic air toxics
in urban areas. The Six Month Study which estimated cancer risks from
exposure to selected toxic air pollutants identified mobile sources as
contributing a large portion of the national cancer incidence. Specific
pollutants and pollutant categories which are emitted by road vehicles
include diesel particulates, formaldehyde, benzene, gas phase organics,
organics associated with non-diesel particulates, asbestos, and metals.
Sources include exhaust and evaporative emissions tire wear, and (in the
case of asbestos) emissions from the wearing away of brake linings.
The composition of road vehicle emissions varies depending on
numerous factors including the age, model, and condition of the vehicle;
the type of fuel used (i.e., leaded or unleaded gasoline, diesel); the
composition of the gasoline including any additives; driving patterns and
speed; and any pollution controls (catalytic or noncatalytic). Because
of the large number of parameters that can affect emissions, it is
necessary to apply "typical" vehicular emissions rates to predict
pollutant loadings in a geographic area. These typical factors are by
vehicular class (e.g., light duty gas, heavy duty diesel) and reflect the
age, accrued mileage, etc., typical of the fleet.
4.2 Factors
Table 4-1 provides toxic pollutant factors. Factors that can be used
with NEDS data are provided on an average VMT basis and on a percent of
hydrocarbon emissions. Many of the factors in Table 4-1 were taken
4
directly from Carey (1987) ; that report should be accessed for
additional information. POM Emissions were estimated based on
1 o
information provided by ORD and are defined as the benzene
exhaustable portion of particulates emitted in road vehicle exhaust.
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ROAD VEHICLES
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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ROAD VEHICLES
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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6/88
ROAD VEHICLES
-------
PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
4.3 Methodology Options
Emission factors can be based on vehicle miles traveled (VMT) and/or
emissions of criteria pollutants, particularly hydrocarbons. When used
in conjunction with NEDS' VMT data or EPA's MOBILE3 (Mobile Source
Emission Model) both of which predict emissions of criteria pollutants,
apportionment factors can be applied to predict toxic pollutant
emissions.
In NEDS, road vehicles can be disaggregated into five categories on
the basis of use and gross vehicle weight for the purpose of calculating
emissions. Light duty gasoline vehicles are defined as gasoline powered
passenger vehicles weighing 8500 pounds or less; similarly light duty
diesel vehicles. Light duty gasoline Trucks I include gasoline cargo
vehicles weighing 6000 pounds or less. Light duty gasoline Trucks II
include gasoline cargo vehicles weighing 6001 pounds to 8500 pounds.
Heavy duty vehicle categories separate diesel and gasoline powered trucks
and buses weighing more than 8500 pounds. Motorcycles, light duty diesel
vehicles and light duty diesel trucks are assumed to contribute little
emissions relative to the above four categories.
Fuel consumption and average fuel efficiencies are used to determine
vehicle miles traveled (VMT) for four classes of average speed to reflect
road usage, namely, limited access roads (55 mph), rural roads (45 mph),
suburban roads (35 mph), and urban roads (19.6 mph). At the present
time, NEDS calculates criteria pollutant emissions for limited access
roads, rural roads and urban road types. Each speed class includes the
following road types.
Limited Access Roads Rural and Urban Interstate
(55 mph) Rural and Urban Other Principal Arterials
Other Freeways and Expressways
Rural and Urban Minor Arterials
6/88 - ROAD VEHICLES 4-7
-------
PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Rural (45 mph) Rural Major Collector
Rural Minor Collector
Rural Local
Urban (19.6 mph) Urban Collector
Urban Local
For highway vehicles, NEDS contains data on fuel consumption (10
gallons) by fuel type for each vehicle type and speed class specific
annual vehicle miles traveled (VMT), along with estimated emissions of
criteria pollutants.
MOBILES, on the otherhand, is a computer model that calculates
emissions of hydrocarbons (HC), carbon monoxide (CO), and oxides of
nitrogen (NO ) from highway motor vehicles using emission factors
2
contained in AP-42, Volume II. MOBILES estimates depend on various
ambient, vehicle usage, and local conditions such as temperature, speed,
and mileage accumulation, and accrual distributions. 'MOBILES will
estimate emissions for any calendar year between 1970 and 2020,
inclusive. The twenty most recent vehicle model years are considered in
operation during each calendar year. Additional information on MOBILES
can be obtained in Reference 3.
MOBILES differentiates between evaporative and exhaust emissions. A
A
recent EPA study, (Carey 1987) compiled emission factors that can be
used with MOBILES to estimate road vehicle related emissions (as well as
exposure and risk); this report is the basis for many of the road vehicle
emission factors that are listed in this manual.
4.4 Example Calculations
The following examples demonstrate the approach for estimating
emissions from onroad vehicles.
6/88 .. ROAD VEHICLES 4-8
-------
PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Example Calculation 1
This example illustrates the calculation of road vehicle emissions
for heavy duty gasoline vehicles (HDGV) using data contained in the NEDS
area source report. NEDS gives estimated total hydrocarbon emissions in
the three-county study area. Then, using emission factors in terms of
percent of total hydrocarbons, the emissions of each pollutant can be
determined.
HDGV total hydrocarbons (THC)
County (MT/vr)
A 56.21
B 32.85
C • 79.57
Using the emission factors in terms of percent of hydrocarbons from
Table 4-1 the emissions from heavy duty gasoline vehicles in the study
area of concern can be calculated as follows:
County A
Formaldehyde:
Exhaust: 0.031 x 56.21 MT THC = 1.74 MT/yr
Evaporative: Not Applicable
1,3 Butadiene
Exhaust: 0.0094 x 56.21 MT THC =0.53 MT/yr
Evaporative: Not Applicable
Benzene
Exhaust: 0.0348 x 56.21 MT THC =1.96 MT/yr
Evaporative: 0.011 x 56.21 MT THC =0.62 MT/yr
yr
Ethylene dichloride
Exhaust: 0.00051 x 56.21 MT THC = 0.029 MT/yr
yr
Evaporative 0.00015 x 56.21 MT THC = 0.0084 MT/yr
yr
6/88 ROAD VEHICLES 4-9
-------
PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
County B
Formaldehyde
Exhaust: 0.031 x 32.85 MT THC = 1.02 MT/yr
yr
Evaporative: Not Applicable
1,3 Butadiene
Exhaust: 0.0094 x 32.85 MT THC = -0.31 MT/yr
Evaporative: Not Applicable
Benzene
Exhaust: 0.0348 x 32.85 MT THC =1.14 MT/yr
yr
Evaporative: 0.011 x 32.85 MT THC = 0.36 MT/yr
Ethylene dichloride
Exhaust: 0.00051 x 32.85 MT THC = 0.017 MT/yr
yr
Evaporative: 0.00015 x 32.85 MT THC = 0.0049 MT/yr
County C
Formaldehyde
Exhaust: 0.031 x 79.57 MT THC = 2.47 MT/yr
yr
Evaporative: Not Applicable
1,3 Butadiene
Exhaust: 0.0094 x 79.57 MT THC =0.75 MT/yr
yr
Evaporative: Not Applicable
Benzene
Exhaust: 0.0348 x 79.57 MT THC =2.77 MT/yr
yr
Evaporative: 0.011 x 79.57 MT THC = 0.87 MT/yr
yr
6/88 - ROAD VEHICLES 4-10
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Ethylene dichloride
Exhaust: 0.00051 x 79.57 MT THC = 0.041 MT/yr
Evaporative: 0.00015 x 79.57 MT THC = 0.012 MT/yr
yr
For metals and semi-volatiles the emissions must be calculated using
estimates of VMT as in Example Calculation 2. Summing the emission over
all the counties will give the total emissions for the study area.
[In a similar manner, emissions from other classes of vehicles can be
calculated based on NEDS data.]
Example Calculation 2
This example demonstrates the calculation of emissions from light
duty gasoline vehicles (LDGV) using data on vehicle miles traveled (VMT)
and emission factors in terms of VMT.
We will assume the study area consists of one county. The annual VMT
for that county is 356,177,000.
Using the emission factors in terms of VMT from Table 4-1 the
emissions are calculated as follows:
County A
Formaldehyde
Exhaust: 3.32 x 1Q-5 MT x 356,177 (1,000 VMT) = 11.82 MT/yr
1,000 VMT yr
Evaporative: Not Applicable
6/88 '. ROAD VEHICLES 4-11
-------
PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
1,3 Butadiene
Exhaust: 2.4 x 10-5 MT x 356,177 (1,000 VMT) = 8055 MT/yr
1,000 VMT yr
Evaporative: Not Applicable
Tire Wear: 1.0 x 10-8 MT x 356,177 (1,000 VMT) = 0.0036 MT/yr
1,000 VMT yr
Benzene
Exhaust: 1.27 x 10-4 MT x 356,177 (1,000 VMT) = 45.23 MT/yr
1,000 VMT yr
Evaporative : Not Applicable
Benzo(a)pyrene
Exhaust: 4.57 x 10-8 MT x 356,177 (1,000 VMT) = 0.0016 MT/yr
1,000 VMT yr
Evaporative: Not Applicable
Lead
Exhaust: 1.28 x 10-6 MT x 356,177 (1,000 VMT) = 0.46 MT/yr
1,000 VMT yr
Evaporative: Not Applicable
Cadmium
Exhaust: 1.9 x 10-9 MT x 356,177 (1,000 VMT) = 0.00068 MT/yr
1,000 VMT yr
Evaporative: Not Applicable
Tire Wear: 4.85 x 10-9 MT x 356,177 (1,000 VMT) * 0.0017 MT/yr
1,000 VMT. yr
Chromium
Exhaust: 6.1 x 10-4 MT x 356,177 (1,000 VMT) - 217.27 MT/yr
1,000 VMT yr
Evaporative: -Not Applicable
The evaporative emissions factor for benzene is given as a range.
To calculate the emissions in this example, we assumed the emission
factor was the midpoint of the range.
6/88 ' ROAD VEHICLES 4-12
-------
PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Ethylene dichloride
Exhaust: 7.65 x 10-7 MT x 356,177-(1,000 VHT) = 0.27 MT/yr
1,000 VMT yr
Evaporative: 1.53 x 10-7 MT x 356,177 (1,000 VMT) = 0.054 MT/yr
1,000 VMT yr
Acetaldehyde
Exhaust: 4.8 x 1Q-7 MT x 356,177 (1,000 VMT) = 0.17 MT/yr
1,000 VMT yr
Evaporative: Not Applicable
Asbestos
Exhaust: Not Applicable
Evaporative: Not Applicable
Brake Linings: 2.05 x 1Q-9 MT x 356,177 (1,000 VMT) = 0.00073 MT/yr
1,000 VMT yr '
Polycyclic Organic Matter
Exhaust: 3.92 x 10-6 MT x 356,177 (1,000 VMT) = 1.40 MT/yr
1,000 VMT yr
Evaporative: Not Applicable
Summing the type of emission for each pollutant will give the total
emission from LDGV for the study area.
[In a similar manner, emissions from other classes of onroad vehicles
can be calculated.]
4.5 Methods to Apportion Countywide Emissions from Road Vehicles
As described in Section 1.0 and Appendix A when performing air
dispersion modeling, it is generally recommended that countywide
emissions be distributed within the study area into rectangular area
source grid cells reflecting spatial variations in activity and
6/88 '_ ROAD VEHICLES 4-13
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
emissions. Similarly temporal in activities can be factored into the
modeling to reflect seasonal or diurnal fluctuations in emissions.
Modeling results would then reflect ongoing activities in that portion of
the county, e.g., residential heating in the winter, commercial solvent
usage during working hours on weekdays.
There are three alternative approaches that can be used in spatially
distributing emission: (1) population, i.e., the magnitude of emissions
within a grid are directly proportional to the population living in the
grid; (2) land area, i.e., emissions from a countywide area source are
assumed to be uniform throughout the county and.are distributed based on
the size of the area source grid; and (3) land use patterns, that assume
that certain area source activities, most likely occur in certain areas
of the county, e.g., commercial, residential or industrial.
In apportining emissions from onroad vehicles any of these methods
may be appropriate. Land area and population data can'be readily
obtained, and applied as described in Appendix A. Land use data,
available from the U.S. Geological Survey and other sources can be used
in combination with the spatial resolution for onroad vehicles, to
distribute emissions based on the type of activity being performed, as
shown in Table 4-2.
Estimated seasonal, daily and hourly temporal resolution for onroad
vehicles are also included in Table 4-2, and can be used with the annual
countywide emissions data to estimate temporal variations.
6/88 -. ROAD VEHICLES 4-14
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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Table 4-2 Spatial and Temporal Resolution for Road Vehicles
Spatial Resolution
Surrogate Indicator: traffic volume'
Information source(s) zonal traffic statistics
Temporal Resolution
Seasonal: uniform through the year
Daily: uniform through the week
Hourly: 75 percent from 0600 to 1800,
25 percent from 1800 to 0600
6/88
ROAD VEHICLES 4-15
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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REFERENCES
1. Haemisegger, E., Jones, A., Steigerwald, B., and Thomson, V. The Air
Toxics Problem in the United States: An Analyses of Cancer Risks for
Selected Pollutants. U.S. Environmental Protection Agency. Office
of Air and Radiation. May 1985.
2. U.S. Environmental Protection Agency. Compilation of Air Pollutant
Emission Factors. Volume II: Mobile Sources. Motor Vehicle
Emission Laboratory. Ann Arbor, MI. AP-42.
3. U.S. Environmental Protection Agency. Users Guide to MOBIL3 (Mobile
Source Emissions Model). Office of Mobile Sources. Ann Arbor, MI.
4. Carey, Penny M. Air Toxic Emissions from Motor Vehicles. U.S.
Environmental Protection Agency. Office of Mobile Sources. Ann
Arbor, MI. EPA-AA-TSS-PA-86-5.
5. Lewtas, Joellen. Information supplied to Versar, Inc. and the
Regulatory Integration Division of the EPA Office of Policy and
Resource Management. -U.S. Environmental Protection Agency. Office
of Research and Development. September 1987.
6. Smith, L.R., Black, F.M. "Characterization of Exhaust Emissions from
Passenger Cars Equipped with Three-way Catalyst Systems." Society of
Automotive Engineers. Warrendale, PA. 1980.
7. Versar, Inc. Non-Occupational Asbestos Exposure. U.S. Environmental
Protection Agency. Office of Toxic Substances. Washington, DC.
1987.
8. U.S. Environmental Protection Agency. Sources of Atmospheric
Cadmium. EPA-450/5-79-006. U.S. Environmental Protection Agency.
Office of Air Quality Planning and Standards. Research Triangle
Park, NC. 1979.
9. Radian Inc. Compiling Air Toxics Emission Inventories.
EPA-450/4-86-010. U.S. Environmental Protection Agency. Office of
Air Quality Planning and Standards. Research Triangle Park, NC.
July 1986.
10. Versar Inc. Exposure Assessment for 1,3-Butadiene. U.S.
Environmental Protection Agency. Office of Toxic Substances.
Washington, DC. 1984.
6/88 - ROAD VEHICLES 4-16
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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REFERENCES
11. Carey, R.N. Mobile Source Emissions of Formaldehyde and Other
Aldehydes. EPA/AA/CTAB/PA-81-11. U.S. Environmental Protection
Agency. Ann Arbor, MI. 1981.
12. U.S. Environmental Protection Agency. Evaluation of Air Pollution
Regulatory Strategies for Gasoline Marketing Industry. Office of Air
and Radiation. Washington, DC. 1984.
13. Sigsby, Drabkin, Bradaw, and Lank. "Automotive Emissions of Ethylene
Dibromide". Society of Automotive Engines. Warrenton, PA. 1982.
6/88 - ROAD VEHICLES 4-17
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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5. AIRCRAFT
5.1 General
Aircraft exhaust contains an assortment of toxic compounds, including
formaldehyde, benzene, metals, and semivolatiles. Ambient monitoring in
areas adjacent to large municipal and military airports indicate that
these levels may at times be significant. Unfortunately, little data are
available on which to base emission factors, since emissions vary
according to engine type, landing and takeoff patterns, etc. At this
time, VOC speciation factors are the only factors available to predict
aircraft exhaust emissions on an area-wide basis. While data are
available on levels of other pollutants emitted by planes, the information
was inadequate to develop factors representative of all aircraft.
5.2 Factors
Emission factors are available for total hydrocarbons (HC) and
particulates. An approach for estimating criteria pollutant emissions is
presented below. The methodology described in detail in AP-42, Volume
II , and used in NEDS to estimate criteria pollutant emissions can be
used in combination with speciation factors provided in Air Emissions Species
Manual2 to estimate emissions of air toxics. These data may be used to apportion
VOCs and particulates based on activities at the airport such as takeoffs
and landings and are provided in Tables 5-1, 5-2 and 5-3.
5.3 Methodology Options
NEDS uses the AP-42 methodology to estimate LTO's and emissions of
criteria pollutants, including total hydrocarbons for commercial, civil,
and military aircraft. In that methodology emissions of criteria
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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Table 5-1 Military Aircraft
Species Name
Isomers of Dodecane
Isomers of Tetradecane
Isomers of Pentadecane
Isomers of Pentene
C16 Branched Alkane
C7-C16
Methane
Ethane
Ethylene
Propane
Propene
Acetylene
Butene
cis-2-Butene
1 ,3-Butadiene
N-Pentane
1-Pentene
2-Methyl-2-Butene
Metnylpentane
Heptane
Octane
Nonane
N-Decane
N-Undecane
1-Hexene
N-Dodecane
N-Tndecane
N-Tetradecane
N-Pentadecane
Heptene
Octene
1-Nonene
Formaldehyde
Acetaldehyde
Propionaldehyde
Acrolein
Butyraldehyde
Hexanal
Glyoxal
Methyl Gloxal
Percent Weight
0.19
0.20
0.18
0.76
0.16
0.32
9.37
0.91
18.36
0.19
5.44
4.41
2.06
0.50
1.89
0.22
0.89
0.21
-0.41
0.07
0.05
0.13
0.44
0.54
0.86
1.07
0.67
0.59
0.26
0.54
0.30
0.26
15.47
4.83
0.98
2.38
1.24
0.22
2.18
2.06
6/88 -- AIRCRAFT
5-2
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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Table 5-1 (Continued)
Species Name Percent Weight
Crotonaldehyde 0.00
Acetone 2.41
Benzene 2.02
Toluene 0.55
Ethylbenzene 0.18
0-Xylene 0.20
Styrene 0.41
Pentyl Benzene 0.21
Butyl Benzene 0.26
Phenol 0.26
Benzaldehyde ' 0.57
Napthalene 0.60
Methyl Naphthalenes 0.52
M-Xylene and P-Xylene 0.30
1-Oecene 0.17
C6H1803SI3 6.96
C8H2404SI4 2.37
Hexadecane 0.12
N-Heptadecane 0.01
Note: Composite profile developed from data .for CFM-36 jet engine fired
with JP-5 fuel at idle, 30% thrust and 80% thrust. Data
collected by GC/MS and DNPH analyses were combined according to
average LTO cycle times obtained from AP-42 (4th. Edition) for
military aircraft
Source: Reference 2
6/88 "- AIRCRAFT 5-3
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Table 5-2 Civil Aircraft
Species Name
Isomers of Dodecane
Isomers of Tetradecane
Isomers of Pentadecane
Isomers of Pentene
C16 Branched Alkane
C7-C16
Methane
Ethane
Ethylene
Propane
Propene
Acetylene
Butene
cis-2-Butene
1,3-Butadiene
N-Pentane
1-Pentene
2-Methyl-2-Butene
Methyl pen tane
Heptane
Octane
Nonane
N-Decane
N-Undecane
1 -Hexene
N-Dodecane
N-Tridecane
N-Tetradecane
N-Pentadecane
Heptene
Octene
1-Nonene
Formaldehyde
Acetaldehyde
Propionaldehyde
Acrolein
Butyraldehyde
Hexanal
Glyoxal
Methyl Gloxal
Percent Weight
0.16
0.17
0.15
0.64
0.13
0.27
10.95
0.92
15.48
0.20
4.59
3.69
1.79
0.45
1.57
0.19
0.75
0.18
0.35
0.06
0.04
0.15
0.42
0.52
0.76
1.21
0.66
0.59
0.27
0.52
0.25
0.22
14.14
4.32
0.90
2.06
1.19
0.20
2.53
1.81
6/88 AIRCRAFT 5"4
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Table 5-2 (Continued)
Species Name Percent Weight
Crotonaldehyde 0.00
Acetone 2.93
Benzene • 1.79
Toluene 0.49
Ethylbenzene 0.13
0-Xylene 0.19
Styrene 0.37
Pentyl Benzene 0.17
Butyl Benzene 0.22
Phenol 0.22
Benzaldehyde 0.53
Napthalene 0.51
Methyl Naphthalenes 0.44
M-Xylene and P-Xylene 0.25
1-Oecene 0.15
C6H1803SI3 11.77
C8H2404SI4 4.20
Hexadecane 0.14
N-Heptadecane 0.01
Note: Composite profile developed from data for CFM-36 jet engine
fired with JP-5 fuel at idle. 30% thrust and 80% thrust. Data
collected by GC/MS and DNPH analyses were combined according to
average LTD cycle times obtained from AP-42 (4th. Edition) for
general aviation.
Source: Reference 2
5-5
6/88 AIRCRAFT
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Table 5-3 Commercial Aircraft
Species Name
Isomers of Dodecane
Isomers of Tetradecane
Isomers of Pentadecane
Isomers of Pentene
C16 Branched Alkane
C7-C16
Methane
Ethane
Ethylene
Propane
Propene
Acetylene
Butene
cis-2-Butene
1 ,3-Butadiene
N-Pentane
1-Pentene
2-Methyl-2-Butene
Methylpentane
Heptane
Octane
Nonane
N-Oecane
N-Undecane
1-Hexene
N-Dodecane
N-Tndecane
N-Tetradecane
N-Pentadecane
Heptene
Octene
1-Nonene •
Forma Idehyde
Aceta Idehyde
Prop lona Idehyde
Acrolein
Butyra Idehyde
Hexana 1
Glyoxal
Methyl Gloxal
Percent Weight
*•
0.18
0.19
0.17
0.73
0.14
0.30
9.56
0.88
17.42
0.18
5.15
4.17-
1.97
0.48
1.80
0.21
0.84
0.20
0.39
0.06
0.05
0.13
0.42
0.53
0.82
1.07
0.66
0.58
0.26
0.54
0.28
0.24
15.00
4.65
0.95
2.27
1.20
0.21
2.54
1.97
6/88 . AIRCRAFT 5'6
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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Table 5-3 (Continued)
Species Name Percent Weight
Crotonaldehyde 0.00
Acetone 2.45
Benzene 1.94
Toluene 0.52
Ethylbenzene 0.17
0-Xylene 0.19
Styrene 0.39
Pentyl Benzene 0.19
Butyl Benzene 0.24
Phenol 0.24
Benzaldehyde 0.55
Napthalene 0.57
Methyl Naphthalenes 0.49
M-Xylene and P-Xylene 0.29
1-Decene 0.17
C6H1803SI3 9.10
CbH2404SI4 ' 2.92
Hexadecane 0.12
N-Heptadecane 0.01
Note: Composite profile developed from data for CFM-36 jet engine
fired with JP-5 fuel at idle, 30'7. thrust and 80% thrust. Data
collected by GC/MS and ONPH analyses were combined according to
average LTD cycle times obtained from AP-42 (4th. Edition) for
commercial aircraft.
Source: Reference 2
6/88 . AIRCRAFT 5-7
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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pollutants are estimated based on aircraft takeoffs and landings. The
general approach is to first estimate the number of landing and takeoff
(LTO) cycles per aircraft type for a specified period of time at each
airport facility. An LTO cycle incorporates all of the normal flight and
around operation modes (at their respective times-in-mode), including
descent/approach from approximately 3000 feet (915 meters) above ground
level(AGL), touchdown, landing run, taxi in, idle and shutdown, startup
and idle, checkout, taxi out, takeoff, and climbout to 3000 feet (915
meters) AGL. It is during this cycle that most compound emissions that
affect the subsequent ground-level concentrations of concern are
released. The LTO estimates are multiplied by aircraft and specific
emission factors, and the results are summed to provide an estimate of
particulate and organic compound emissions for the inventory period and
location of interest.
Alternative, more labor intensive, approaches are available to
estimate LTOs. One possible approach, for example, is to obtain
information directly from each airport. Airports often have detailed
information on their operations that can be very helpful.
5.4 Example Calculation
Example Calculation
The example below demonstrates a methodology for estimating total
annual airport emissions of three pollutants: 1,3 butadiene,
formaldehyde, and benzene.
Step 1. Obtain VOC Data.
The emission factors are given by percentage of VOC for three types
of aircraft: military, civil, and commercial. NEDS gives estimates of
countywide VOC estimates for these aircraft categories. Data for a
hypothetical county is given below.
6/88 . AIRCRAFT 5-8
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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Aircraft Type VOC Emissions (kkq/vr)
Military 384
Civil 40
Commercial ,. 1,357
Step 2. Multiply VOC estimates by pollutant specific emission factors.
Table 5-1, 5-2, and 5-3 provide speciation factors for the three
compounds. The emissions of three pollutants of concern -(1,3 butadene,
formaldehyde, and benzene) are calculated as follows.
Military
1,3 butadene: 384 Metric tons x 0.0189 = 7.3 Metric tons/yr
year
formaldehyde: 384 Metric tons x 0.1547 = 59.40 Metric tons/yr
year
benzene: 384 Metric tons x 0.0202 - 7.75 Metric tons/yr
year
Civil
1,3 butadene: 40 Metric tons x 0.0157 = 0.6 Metric tons/yr
year
formaldehyde: 40 Metric tons x 0.1414 = 5.7 Metric tons/yr
year
benzene: 40 Metric tons x 0.0179 = 0.7 Metric tons/yr
year
Commercial
1,3 butadene: 1.357 Metric tons x 0.0180 = 24.4 Metric tons/yr
year
formaldehyde: 1.357 Metric tons x 0.1500 = 203.6 Metric tons/yr
year
benzene: 1.357 Metric tons x 0.0194 = 26.3 Metric tons/yr
year
6/88 . AIRCRAFT 5"9
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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5.5 Methods to Apportion Countvwide Emissions from Aircraft
As described in Section 1.0 and Appendix A when performing air
dispersion modeling, it is generally recommended that countywide
emissions be distributed within the study area into rectangular area
source grid cells reflecting spatial variations in activity and
emissions. Similarly temporal in activities can be factored into the
modeling to reflect seasonal or diurnal fluctuations in emissions.
Modeling results would then reflect ongoing activities in that portion of
the county, e.g., residential heating in the winter, commercial solvent
usage during working hours of weekdays.
In apportioning emissions from aircraft the U.S. Geological Survey
and other sources can be used in combination with the spatial resolution
for aircraft, to distribute emissions based on the type of activity being
performed, as shown in Table 5-4.
The best approach for estimating spatial distribution is to identify
airports on U.S. Geological Survey land use maps, contacting local
airport authorities, and surveying U.S. Department of Transportation data
on airport activities, as noted in Table 5-4. Spatial, temporal
variations on activity and emissions tend to be unique for each airport;
airport authorities usually have detailed information on variations in
activity.
6/88 - AIRCRAFT 5-10
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Table 5-4
Spatial and Temporal Resolution for Aircraft
Aircraft, General0
Spatial Resolution
Surrogate indicator:
Information source(s)1
Temporal Resolution
Seasonal:
Daily:
Hourly:
airport area (code 14)
land use map, local airport
authority, and Reference 4
uniform through the year
40 percent of operations occur on
weekends
and 60 percent on weekdays
uniform from 0700 to 2100, otherwise
zero
Aircraft, Commercial
Spatial Resolution
Surrogate indicator:
Information source(s):
Temporal Resolution
Seasonal, daily, and
hourly:
airport area by airport (code 14)
land use map, local airport
authority, and References 5 and 6
Since the temporal profiles of
commercial airports vary widely, the
respective airport managers should be
contacted. The airport managers
usually have very detailed temporal
information.
Aircraft, Military
Spatial Resolution
Surrogate indicator:
Information source(s):
Temporal Resolution
Seasonal, daily, and
hourly:
airport area (code 14)
land use map, local airport
authority, and Reference 7
Estimate on individual basis. Contact
local airport authorities and
appropriate military agencies.
6/88
AIRCRAFT
5-11
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REFERENCES
1. Compilation of Air Pollutant Emission Factors, Volume II: Mobile
Sources (AP-42), Fourth Edition, Office of Mobile Sources, U. S.
Environmental Protection Agency, Ann Arbor, MI, 1985.
2. Air Emissions Species Manual, EPA-450/2-88-003a and b, Office of Air
Quality Planning and Standards, U. S. Environmental Protection
Agency, Research Triangle Park, NC, April 1988.
3. Procedures for the Preparation of Emission Inventories for Volatile
Ozone Compounds. Volume II; Emission Inventory Requirements for
Photochemical Air Quality Simulation Models.EPA-450/4-79-018,
Office of Air Quality Planning and Standards, U. S. Environmental
Protection Agency, Research Triangle Park, NC, September 1979.
4. Census of U. S. Civil Aircraft, U. S. Department of Transportation,
Federal Aviation Administration, Washington, DC. Annual.
5. FAA Air Traffic Activity Reports, U. S. Department of Transportation,
Federal Aviation Administration, Washington, DC. Annual.
6. Aircraft Activity Statistics for Certified Route Air Carriers, U. S.
Department of Transportation, Federal Aviation Administration,
Washington, DC. Annual.
7. Military Air Taffic Report, U. S. Department of Transportation,
Federal Aviation Administration, Washington, DC. Annual.
3/89 ' AIRCRAFT 5-12
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6. COMFORT AND INDUSTRIAL COOLING TOWERS
6.1 General1
Chromium, in the form of chromates, is commonly added to cooling
tower water as a corrosion inhibitor. Water droplets and the dissolved
solids, including chromates, that they contain are entrained in the air
and are emitted from the cooling tower stack. Because this cooling tower
"drift" will also presumably contain chromates, it follows that cooling
towers are potentially an important source of hexavalent chromium air
emissions.
There are two types of cooling towers, comfort and industrial.
Comfort cooling towers are used to maintain a specified environment or
refrigeration system. Industrial process cooling towers are used to
control the temperatures of process fluids in industrial production units.
Chromium emission rates vary depending on the type of cooling tower.
It is estimated that national baseline emissions of hexavalent chromium
from comfort cooling towers are between 7.2 and 206 metric tons annually,
and national baseline emissions from industrial cooling towers (for the
four major industries that make up the majority of industrial towers) are
795 metric tons per year.
Warm water is cooled by cooling towers when it contacts ambient air
that is drawn or forced through the tower. For most cooling towers,
about 80 percent of the cooling occurs through evaporation of water, as
the air flowing through the tower contacts the water flowing from the top
to the bottom of the tower. Most tower systems are designed with
recirculating water systems to conserve water resources or reduce the
cost of purchasing water. The major cooling tower components are the
fan(s), fill material, water distribution deck or header, drift
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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eliminator, structural frame, and cold water basin. Other components
that affect tower operation include the pumps and pipes necessary to
circulate the cooling water through the tower and heat exchanger loops.
Cooling towers are designed with mechanically induced-, mechanically
forced-, or natural-draft airflow. Induced-draft airflow is provided by
a propeller-type fan located in the stack at the top of the tower.
Forced-draft towers are usually smaller than induced-draft towers and
have either centrifugal fans located at the base of the tower or axial
fans located on the side of the tower. Natural-draft airflow relies on
the buoyancy created by differences in temperature between the air in the
tower and the atmosphere. When the cooling demands are minimal and the
air temperature is low enough, water can be circulated through the tower
and can be cooled sufficiently without using the fans. In these
instances, a natural draft is created in a mechanical draft tower. The
direction of airflow in a mechanical-draft tower is either crossflow or
counterflow. Crossflow refers to horizontal airflow through the fill;
counterflow refers to upward vertical airflow.
Drift eliminators can be installed at the exit of the fill sections
to reduce the drift in the exiting airflow. The drift removal efficiency
is a function of the drift eliminator design, of which there are four
major types: blade-type, waveform, cellular, and herringbone.
(Herringbone is similar to blade-type, but the blades in one row are
offset from the blades in the next row.) Typically, herringbone and
blade-type units are the least efficient, waveform units are moderately
efficient, and cellular units are the most efficient. Drift eliminators
are constructed of wood, PVC, metal, asbestos-cement, polystyrene, or
cellulose.
Comfort cooling towers. Comfort cooling towers are used in all
states in the U.S., primarily in urban areas. Major users of comfort
cooling towers with heating, ventilating, and air conditioning (HVAC)
systems include hospitals, hotels, educational facilities, office
6/88 ; COMFORT AND INDUSTRIAL COOLING TOWERS 6-2
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buildings, and shopping malls. Refrigeration systems that may operate
with comfort cooling towers include ice skating rinks, cold storage
(food) warehouses, and other commercial operations. Estimates from the
two largest manufacturers of cooling towers indicate that the nationwide
2 3
population of comfort cooling towers is between 200,000 and 300,000. '
Water treatment vendors estimated that 10 to 25 percent of comfort
cooling towers use chromium-based water treatment chemicals. ' For
analysis purposes, it is assumed that the nationwide population of
comfort cooling towers is 250,000 units and that 15 percent of them
(about 37,500) use chromium-based water treatment chemicals. Hexavalent
chromium use in comfort cooling towers appears to be distributed randomly
across the country.
Typically, comfort cooling towers are open recirculating systems with
either forced- or induced-draft airflow (natural-draft airflow is not
used for comfort cooling towers) and are designed with crossflow air
direction.
Industrial cooling towers. The industrial cooling tower category
includes all cooling towers that are used to remove heat from an
industrial process or chemical reaction. Towers that are used to cool
both industrial processes and HVAC and refrigeration systems are also
included in this category. Only towers devoted exclusively to cooling
HVAC and refrigeration systems are defined as comfort cooling towers.
Major users of industrial cooling towers are chemical manufacturing,
petroleum refining, primary metals, and numerous miscellaneous
industries. The industries in the U.S. using chromium-based water
treatment chemicals include approximately 190 petroleum refineries,
1,800 chemical manufacturing plants, 1,000 primary metals plants
(including 775 foundries), and 750 plants in five miscellaneous
industries (textiles, tobacco products, tire and rubber products, glass
6/88 - COMFORT AND INDUSTRIAL COOLING TOWERS 6-3
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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products, and utilities). It was assumed that chromates are not used in
miscellaneous industries other than the five referred to above.
Approximately 8,800 industrial cooling towers are estimated to be
operating in all eight industries. It is further estimated that the
percentage of towers using chromium-based chemicals is 73 percent at
petroleum refineries, 40 percent at chemical manufacturing plants, 21
percent at primary metals facilities, and 15 percent in the miscellaneous
industries, except for utilities where only two are reported to use
chromates. These percentages result in a total of about 2,800 industrial
cooling towers using chromium-based water treatment chemicals.
In a typical industrial cooling system, cooling water is pumped from
the cooling tower basin to the heat exchanger(s) being served by the
tower, and the heated water flows back to the cooling tower water
distribution system. The cooling water loop may include numerous
separate heat exchangers of various designs. Heat exchangers are
designed to transfer heat from one fluid to another. The transfer can
occur directly by mixing the hot and cold materials or indirectly through
a device separating the hot and cold materials. Indirect heat exchanger
types include shell-and-tube, flat plate, and spiral designs. In most
industries, heat transfer is accomplished with shell-and-tube heat
exchangers. '
6.2 Factors
Comfort cooling towers. Chromium emission factors have been
developed based on EPA-sponsored tests performed on industrial cooling
towers equipped with lower efficiency drift eliminators, which are
similar to comfort cooling towers. These emission factors relate
chromium emissions to the chromium concentration in the recirculation
water. Data on chromate concentrations in comfort cooling tower water
indicate that concentrations vary from less than 1 ppm to 20 ppm
8910
chromate. '' Although a large amount of data has
6/88 . COMFORT AND INDUSTRIAL COOLING TOWERS 6-4
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
shown that the average concentration of chromate in industrial process
cooling towers is 13 ppm, there are insufficient data on comfort cooling
towers to justify using a concentration other than the midpoint of the
11-19
observed range. Therefore, the chromate <
to be 10 ppm, or 4.48 ppm hexavalent chromium.
11-19
observed range. Therefore, the chromate concentration is assumed
The lowest emission factor is-thought to underestimate emissions
because some of the hexavalent chromium in the samples was retained on
the walls of the beakers used to concentrate the samples. Errors are
not, expected to account for most of the difference between the lowest
and highest emission factors, however. The wide differences among
emission factors indicate that emissions may vary substantially with time
for an individual tower as'well as from tower to tower.
The above results were used to develop emission factors on a per
capita basis. The total number of comfort cooling towers was apportioned
(by size groups) by state based on state population. The chromium
emissions for individual towers in each state are dependent on the
utilization rate for the state. The utilization rate is the percentage
of the number of days that the tower operates annually. The utilization
rate depends on the climate at the cooling tower site. It was assumed
(as a rough approximation) that the tower is not used on days when the
average temperature is below 60°F
The annual chromium emissions from individual towers in each state
were estimated by calculating annual emissions based on the factors cited
above. The estimated individual emission rates for the six tower sizes
in each state were then multiplied by the respective number of comfort
cooling towers of that size in the state to obtain the statewide chromium
emission. The average emission rate per person for each state was
estimated by dividing the total chromium emission rate for the state by
the population of the state. The resulting emission factors are provided
6/88 - COMFORT AND INDUSTRIAL COOLING TOWERS 6-5
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
in Table 6-1. The factors are presented as ranges because they were
calculated from the highest and lowest emission factors from the
EPA-sponsored study. Therefore, the lower value carries the same -
uncertainty as the Agency's lowest emission factor because of the problem
of the chromium retention in the beaker during the test.
Industrial cooling towers. An estimated national average emission
factor for chromium releases from industrial cooling towers was
determined based on four industries: petroleum refining, chemical
manufacturing, primary metals, and miscellaneous industries (including
the textiles, tire and rubber, tobacco, glass manufacturing, and
utilities industries), as well as four different sizes of cooling towers
in each industry.
Data compiled from the petroleum refinery industry indicate that the
average chromate concentration in industrial cooling towers is
approximately 13 ppm. Data from the Chemical Manufacturers Association
also indicate an average of 13 ppm chromate in the chemical manufacturing
industry. (These two categories account for the majority of the
industrial cooling towers.) In the absence of data for other industries,
13 ppm chromates was assumed for all industry categories. Thirteen ppm
chromates translates into 5.82 ppm hexavalent chromium.
A chromium emission factor was developed from EPA-sponsored tests
performed on industrial cooling towers equipped with low efficiency drift
eliminators. The emission factor relates chromium emissions to
recirculation rate and chromium concentration in the water. Testing was
done for crossflow towers, the most common type of comfort cooling tower
in use. Information from a cooling tower vendor indicates that crossflow
towers are more likely to have higher drift rates than the other type of
tower, counterflow towers, because crossflow towers have higher
velocities at the outlet.
6/88 -. COMFORT AND INDUSTRIAL COOLING TOWERS 6-6
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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Table 6-1 Lower- and Upper-Bound Estimates of
Annual Cr Emissions Per Person By State
State
Alabama
Alaska3
Arizona
Arkansas
Cal ifornia
Colorado
Connecticut
Delaware
Florida
Georgia
Hawa i i
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Uti lization
(percent)
59
0
55
56
54
29
33
33
89
59
100
21
42
42
38
42
42
65
21
46
33
33
29
59
42
Hexavalent Chromium
Emissions
(kg/yr
per person)
4.13E-05-1.17E-03
O.OOE+00-O.OOE+OO
3.85E-05-1.09E-03
3.92E-05-1.11E-03
3.78E-05-1.07E-03
2.03E-05-5.76E-04
2.31E-05-6.56E-04
2.31E-05-6.56E-04
6.23E-05-1.77E-03
4.13E-05-1.17E-03
7.QOE-05-1.99E-03
1.47E-05-4.17E-04
2.94E-05-8.35E-04
2.94E-05-8.35E-04
2.66E-05-7.55E-04
2.94E-05-8.35E-04
2.94E-05-8.35E-04
4.55E-05-1.29E-03
1.47E-05-4.17E-04
3.22E-05-9.14E-04
2.31E-05-6.56E-04
2.31E-05-6.56E-04
2.03E-05-5.76E-04
4.13E-05-1.17E-03
2.94E-05-8.35E-04
Hexavalent Chromium
Emissions
(Ib/yr
per person)
9.11E-05-2.59E-03
0-OOE+OO-O.OOE+OO
8.49E-05-2.41E-03
8.64E-05-2.45E-03
8.33E-05-2.37E-03
4.48E-05-1.27E-Q3
5.09E-05-1.45E-03
5.09E-05-1.45E-03
1.37E-05-3.90E-03
9.11E-05-2.59E-03
1.54E-04-4.38E-Q3
3.24E-05-9.20E-04
6.48E-05-1.84E-03
6.48E-05-1.84E-03
5.86E-05-1.67E-03
6.48E-05-1.67E-03
6.48E-05-1.84E-03
1.00E-04-2.85E-03
3.24E-05-9.20E-04
7.10E-05-2.02E-03
5.09E-05-1.45E-03
5.09E-05-1.45E-03
4.48E-05-1.27E-Q3
9.11E-05-2.59E-03
6.48E-05-1.84E-03
Alaska .was assumed to have no comfort cooling towers because, on average, there
are no days when the main temperature exceeds 60°F.
6/88
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6-7
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Table 6-1 (Continued)
State
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carol ina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
Washington, D.C.
Uti 1 ization
(percent)
25
42
39
27
42
39
33
53
25
39
54
23
39
33
59
33
50
63
31
25
42
20
42
31
25
50
Hexavalent Chromium
Emissions
(kg/yr
per person)
1.75E-05-4.97E-04
2.66E-05-7.55E-04
2.73E-05-7.75E-04
1.89E-05-5.37E-04
2.94E-05-8.35E-04
2 73E-05-7.75E-04
2.31E-05-6.56E-04
3.71E-05-1.05E-03
1.75E-Q5-4.97E-04
2.73E-05-7.75E-04
3.78E-05-1.07E-03
1.61E-05-4.57E-04
2.73E-05-7.75E-04
2.31E-05-6.56E-04
4 13E-05-1.17E-03
2.31E-05-6.56E-04
3.50E-05-9.94E-04
4.41E-05-1.25E-03
2.17E-05-6.16E-04
1.75E-05-4.97E-04
2.94E-05-8.35E-04
1.40E-05-3.98E-04
2.94E-05-8.35E-04
2.17E-05-6.16E-04
1.75E-05-4.97E-04
3.50E-05-9.95E-04
Hexavalent Chromium
Emissions
(Ib/yr
per person)
3.86E-05-1.10E-03
5.86E-05-1.67E-03
6.02E-05-1.71E-03
4.17E-05-1.18E-03
6.48E-05-1.84E-03
6.02E-05-1.71E-03
5.09E-05-1.45E-03
8.18E-05-2.32E-03
3.86E-05-1.10E-Q3
6.02E-05-1.71E-03
8.33E-05-2.37E-03
3.55E-05-1.01E-03
6.02E-05-1.71E-03
5.09E-05-1.45E-03
9.11E-05-2.59E-03
5.09E-05-1.45E-03
7.72E-05-2.19E-03
'9.72E-05-2.76E-03
4.78E-05-1.36E-03
2.86E-05-1.10E-03
6.48E-05-1.84E-03
3.09E-05-8.76E-04
6.48E-05-1.84E-03
4.78E-05-1.36E-03
3.86E-05-1.10E-03
7.72E-05-2.19E-03
Source: Reference 1
6/88 COMFORT AND INDUSTRIAL COOLING TOWERS
6-8
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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Table 6-2 lists the emission factors for counterflow, crossflow, and the
national average baseline. The emissions are given as amount of
hexavalent chromium emitted per hexavalent chromium concentration in the
cooling water. Hexavalent chromium emissions can be estimated by
multiplying the emission factor by the concentration of chromium and the
recirculation rate.
Emission factors have also been calculated to relate hexavalent
chromium emissions to the number of employees in the study area for the
industries that contribute the most to industrial cooling tower
emissions. The Background Information Document for Industrial Cooling
Towers contains data on national emissions of hexavalent chromium for
the petroleum refining, chemical manufacturing, primary metals, textile
finishing, tobacco, tire and rubber, and glass manufacturing industries
as well as for utilities.
20
County Business Patterns was used to determine the number of
employees nationally for each of the SIC codes listed in Table 6-3. The
number of employees (by SIC code) was summed for each industry. The
national hexavalent chromium emission for that industry was then divided
by the national number of employees for that industry, giving the
emission factor as kg/yr/employee (Ib/yr/employee). Table 6-4 presents
these emission factors.
6.3 Methodology Options
Comfort Cooling Towers. To estimate area source emissions of
hexavalent chromium from comfort cooling towers, the following steps are
recommended:
6/88 - COMFORT AND INDUSTRIAL COOLING TOWERS 6-9
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Table 6-2 Industrial Cooling Tower Emission Factors
Emission factor
+6 +6 +6 +6
mg Cr /ppm Cr /I HO Ib Cr /ppm Cr /gal HO
0.0003 2.49 x 10"9
Source: Reference 2.
Table 6-3 SIC Codes Included in Industry-Specific Emission Factors
Industry SIC Codes
Petroleum Refining 291
Chemical Manufacturing 281, 282, 286, 287
Primary Metals 331,332,333
Textile Finishing 223, 226
Tobacco 211, 212, 213
Tire and Rubber 301, 302, 304, 306
Glass Manufacturing 321, 322
Utilities 491
Source: Reference 7.
6/88 . COMFORT AND INDUSTRIAL COOLING TOWERS 6"10
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Table 6-4 Industrial Cooling Tower Hexavalent Chromium
Employee-Based Emission Factors
Industry
Emission factor
kg/yr/employee Ib/yr/employee
Petroleum Refining
Chemical Manufacturing
Primary Metals
Textile Finishing
Tobacco
Tire and Rubber
Glass Manufacturing
Utilities
0.35
0.19
0.02
0.09
0.018
0.0037
0.005
0.002
0.75
0.42
0.045
0.20
0.044
0.008
0.011
0.005
6/88
COMFORT AND INDUSTRIAL COOLING TOWERS
6-11
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
• Determine the population of the study area. This information
can be obtained from population reports published by the U.S.
Department of Commerce, Bureau of the Census.
• Multiply the emission factor for the state in which the study
area lies by the population of the study area to give an
estimate of the study-wide area emission of hexavalent chromium
from comfort cooling towers.
Industrial cooling towers. The easiest method for estimating area
source emissions of hexavalent chromium is to determine the number of
employees in industries likely to use hexavalent chromium in cooling
towers, and to apply the emission factors in Table 6-5, as follows:
• Determine, for each industry listed in Table 6-5, the number of
employees in the study area. This information is available
21
from County Business Patterns. which
employees for each SIC code by county.
21
from County Business Patterns. which gives the number of
• For each industry, multiply the emission factor by the number
of employees in the study area to give an estimate of the area
source emissions for that industry.
• Sum the emissions over all industries in the study area to
obtain an estimate of the total area source emissions of
hexavalent chromium from industrial cooling towers in the study
area.
Alternately, area source emissions of hexavalent chromium from
industrial cooling towers can be estimated using the following approach:
6/88 - COMFORT AND INDUSTRIAL COOLING TOWERS 6-12
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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Determine, by surveying the facilities in the study area, which
facilities have cooling towers that use chromate-based water
treatment, and what the annual recirculation rate is for each
of the towers under consideration.
Sum the recirculation rates to determine the total
recirculation rate of chromium-containing cooling water in the
study area.
Multiply the national average baseline emission factor by the
concentration of hexavalent chromium (assumed to be 4.48 ppm)
and by the total recirculation rate in the study area to give
an estimation of the study-wide area emission of hexavalent
chromium by industrial cooling towers.
6.4 Example Calculations
Example Calculation 1
Hexavalent chromium emissions can be calculated on a per capita basis
as shown in the following example.
The emission is calculated on a per capita basis. Assuming the study
area is in Alabama and the study area population is 150,000, the per
capita emission factor for Alabama from Table 6-1 is multiplied by the
study area population of 150,000:
1.17 x 1 kg/yr/person x 150,000 people = 175.5 kg/yr
2.59 x 10 Ib/yr/person x 150,000 people = 388.5 Ib/yr.
6/88 ; COMFORT AND INDUSTRIAL COOLING TOWERS 6-13
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Example Calculation 2
A method for estimating hexavalent chromium emissions from industrial
cooling towers is demonstrated in the following example.
One can assume that there are 15 industrial cooling towers in a study
area-that use chromates for corrosion control and that summing the
recirculation rate for all 15 of these towers yields a total
recirculation rate of 6.8 x 10 1/hr (1.8 x 107 gal/hr). Multiplying
this value by the national average baseline emission factor will give the
emission of hexavalent chromium from industrial cooling towers in the
study area:
(6.8 x 107 1/hr) x (4.48 ppm) x (0.0016 mg Cr/ppm Cr/1 H20) = 4.88 x 105 mg/hr
(1.8 x 107 gal/hr) x (4.48 ppm) x (1.33xlO~8 IbCr/ppm Cr/gal H20) = 1.07 Ib/hr.
Alternatively, the emissions can be calculated based on number of employees f
the major industries in the study area. Assuming the study area is Allegheny
County, Pennsylvania, the number of employees by SIC code can be determined from
County Business Patterns (Pennsylvania). The number of employees for Allegheny
County for each SIC Code of concern is as follows:
Industry
Petroleum Refining
SIC Code
291
Total
No. of
employees
Chemical Manufacturing
281
282
286
287
Total
468
1,679
250-499 (assume average of 375)
0
2,522
Primary Metals
331
332
333
Total
38,68
2,622
0
41,311
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COMFORT AND INDUSTRIAL COOLING TOWERS
6-14
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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No. of
Industry
Textile Finishing
SIC Code
223
226
Total
employees
0
0
Tobacco
Tire and Rubber
Glass Manufacturing
211
212
213
Total
301
302
304
306
Total
321
322
Total
0
0
0
0
0
0
20-99 (assume average of 60)
60
0
877
877
Utilities
491
Total
250-499 (assume average of 375)
375
The next step is to multiply the emission factor for each industry by
the total number of employees for that industry
Industry
Petroleum Refining
Chemical Manufacturing
Primary Metals
Textile Finishing
Tobacco
Tire and Rubber
Glass Manufacturing
Utilities
Emission factor
(Ib/yr/employee)
4.03
2.27
0.24
1.06
0.21
0.044
0.06
0.029
No. of employees
Emissions Cr-6
flb/yr)
2
41
0
,522
,311
0
0
60
877
375
0
,725
,915
0
0
3
53
11
6/88
COMFORT AND INDUSTRIAL COOLING TOWERS
6-15
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Finally, summing the chromium emissions over all the industries will
givean estimate of the hexavalent chromium emissions from industrial
cooling towers in the study area:
5,725 + 9,915 + 3 + 53 + 11 = 15,707 Ib/yr.
6.5 Methods to Apportion Countywide Emissions from Cooling Towers
As described in Section 1.0 and Appendix A when performing air
dispersion modeling, it is generally recommended that countywide
emissions be distributed within the study area into rectangular area
source grid cells reflecting spatial variations in activity and
emissions. Similarly temporal in activities can be factored into the
modeling to reflect seasonal or diurnal fluctuations in emissions.
Modeling results would then reflect on-going activities in that portion
of the county, e.g., residential heating in the winter, commercial
solvent usage during working hours on weekdays.
There are three alternative approaches that can be used in spatially
distributing emission: (1) population, i.e., the magnitude of emissions
within a grid are directly proportional to the population living in the
grid, (2) land area, i.e., emissions from a countywide area source are
assumed to be uniform throughout the county and are distributed based on
the size of the area source grid, and (3) landuse patterns, that assume
that certain area source activities, most likely occur in certain areas
of the county, e.g., commercial, residential or industrial.
In apportioning emissions from comfort and industrial cooling towers,
any of these methods may be appropriate. Land area and population data
can be readily obtained, and applied as described in Appendix A. Land
use data, available from the U.S. Geological survey and other sources can
6/88 . COMFORT AND INDUSTRIAL COOLING TOWERS 6-16
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
be used in combination with the spatial resolution for both categories of
cooling towers, to distribute emissions based on the type of activity
being performed, as shown in Table 6-5.
Estimated seasonal, daily and hourly temporal resolution for
industrial and comfort cooling towers are also included in Table 2-5, and
can be used with the annual countywide emissions data to estimate
temporal variations.
6/88 . COMFORT AND INDUSTRIAL COOLING TOWERS 6-17
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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Table 6-5 Temporal and Spatial Oesolution for Industrial and
Comfort Cooling Towers
Industrial Cooling Towers
Spatial Resolution
Surrogate indicator- industrial areas (codes 13 and 15)
Information source: land use maps
Temporal Resolution
Seasonal: uniform through the year
Daily: uniform through the week
Hourly: 80 percent from 0700 to 1900, 20
percent from 1900 to 2400.
otherwise zero
Comfort Cooling Towers (Residential/Commercial/Instltutional)
Spatial Resolution
Surrogate indicator: residential areas (land use codes
11, 16, and 17) and commercial
areas (land use codes 12 and 15)
Information source(s): land use maps
Temporal Resolution
Seasonal: 25 percent uniform through year and
75 percent uniform during months
that have an average temperature of
68* or more
Daily: 90 percent Monday through Saturday
10 percent Sunday
Hourly: 75 percent 0800 through 2000
25 percent 0100 through 0800
6/88 . COMFORT AND INDUSTRIAL COOLING TOWERS 6-18
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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REFERENCES
1. U.S. Environmental Protection Agency. Chromium Emissions from Comfort
Cooling Towers - Background Information for Proposed Standards
(Preliminary Draft). Office of Air Quality Planning and Standards.
Research Triangle Park, NC. 1987.
2. Telecon. Comfort Cooling Towers Population. P-. Bellin, MRI, with I.
Kularic, Marley Cooling Towers. July 5, 1985.
3. Telecon. Comfort Cooling Tower Population. M. Upchurch, MRI with J.
Carroll, BAC-Pritchard. Septembers, 1986.
4. Telecon. Chromium-using Comfort Cooling Towers. C. Green, MRI, with
R. Kellog, Jr., Dubois Chemical Division, Chemed Corp. March 29,
1985.
5. Telecon. Chromium-using Comfort Cooling Towers. C. Green, MRI, with
P. Thomas, Drew Chemical Company. April 2, 1985.
6. Telecon. Chromium-using Comfort Cooling Towers. C. Green, MRI, with
J. Lee, 01 in Water Services. April 2, 1985.
7. U.S. Environmental Protection Agency. Background Information Document
(Chapters 3 Through 8) for Chromium Emissions from Industrial Process
Cool ing Towers. (Draft). Office of Air Quality Planning and
Standards. Research Triangle Park, NC. 1987.
8. Trip report: Sovran Bank, Norfolk, Virginia. D. Randall, MRI, to R.
Meyers, EPA:ISB. July 15, 1986.
9. Letter and attachments. Response to Section 114 information request.
Campbell R., Union Oil Company of California, to Farmer, J., EPA:ESED.
July 1, 1986. •
10. Letter and attachments. Response to Section 114 information request.
Arvidson, P., BASF Corporation, to Farmer, J., EPA:ESED. July 31, 1986,
11. Letter and attachments. Summary of CMA member survey on corrosion
inhibitors used in process cooling towers including average
circulating water pom. Mayer, A., Chemical Manufacturers Association,
to Cuffe, S., EPA:ISB. September 27, 1986.
12. Letter and attachments. Response to Section 114 information request.
Evans, R., AMOCO Oil Company, to Myers, R., EPA:ISB. June 14, 1985.
6/88 - COMFORT AND INDUSTRIAL COOLING TOWERS 6-19
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
REFERENCES (Continued)
13. Letter and attachments. Response to Section 114 information request.
Simmons, R., ARCO Petroleum Products Company, to Farmer, J., EPA:ESED.
June 3, 1985.
14. Letter and attachments. Response to Section 114 information request.
Parker, F., Chevron U.S.A., to Farmer, J., EPA:ESED. May 16 and 31,
1985.
15. Letter and attachments. Response to Section 114 information request.
Johnson, J., Exxon Company, U.S.A., to Farmer, J., EPA:ESED. May 20,
1985.
16. Letter and attachments. Response to Section 114 information request.
Williams, J., Gulf Oil Products Company, to Farmer, J., EPA:ESED. May
20 and July 26, 1985.
17. Letter and attachments. Response to Section 114 information request.
Kienle, R., Shell Oil Company, to Farmer, J., EPA:ESED. May 22, 1985.
18. Letter and attachments. Response to Section 114 information request.
Hawes, R., Mobil Oil Corporation, to Farmer, J. EPA:ESED. May 20,
1985.
19. Letter and attachments. Response to Section 114 information request.
Cox, R., Texaco U.S.A., to Farmer, J., EPArESED. May 24, 1985.
.20. U.S. Department of Commerce. County Business Patterns 1982 United
States, Employment and Payrolls, Number and Employment, Size of
Establishments by Detailed Industry. CBP-82-1. Bureau of the Census.
October 1984.
21. U.S. Department of Commerce. County Business Patterns 1980
Pennsylvania, Employment and Payrolls, Number and Employment. Size of
Establishments bv Detailed Industry. CBP-80-40. Bureau of the Census.
July, 1982.
6/88 - COMFORT AND INDUSTRIAL COOLING TOWERS 6-20
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7. FOREST FIRES AND AGRICULTURAL BURNING
7.1 General
Open burning (e.g., forest wildfires, managed burning, and
agricultural burning) is a source of a number of air toxics, most
notably, products of incomplete combustion such as polycyclic organic
matter (POM). A forest "wildfire" is a large-scale natural combustion
process that consumes various ages, sizes, and types of botanical
specimens growing outdoors in a defined geographical area. Managed
burning activities include slash burning and prescribed burning. Slash
burning practices are used to burn wastes from logging operations under
controlled conditions, whereas prescribed burning is used as a forest
management practice to establish favorable seedbeds, remove competing
underbrush, and produce to other ecological benefits. Agricultural
burning is practiced routinely to clear and/or prepare land for
planting.
7.2 Factors
Emissions from wildfires and controlled burning in areas can be
significant despite the relatively short duration of the burn. The size
and intensity of these fires are dependent on such variables as
meteorological conditions, species of vegetation and their moisture
content, and the weight of consumable fuel per acre.
Limited data are available to characterize air toxics emissions from
wildfires, managed burning, and agricultural burning. It has been
hypothesized (but not proved) that the nature and amounts of air
pollutant emissions are directly related to the intensity and direction
(relative to the wind) of the wildfire and are indirectly related to the
rate at which the fire spreads. The factors the rate of spread are (1)
weather (wind velocity, ambient temperature, relative humidity, and
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precipitation); (2) fuels (type, bed array, moisture content, and size);
and (3) topography (slope and profile). However, logistical problems
(such as size of the burning area) and the difficulties involved in
safely situating personnel and equipment near the fire have prevented the
collection of reliable experimental emission data on actual wildfires.
Thus, it is presently impossible to verify or disprove the above
hypothesis. Until such measurements are made, therefore, the only
available information is that obtained from burning experiments in the
laboratory. Although existing emission factors are adequate for
laboratory-scale emissions estimates, substantial errors may result if
they are used to calculate actual wildfire emissions. Emission
factors that can be used to estimate air toxics emitted from forest
fires, managed burning, and agricultural burning are presented in Tables
7-1, 7-2, and 7-3.
7.3 Methodology Options
For each type of burning or burning operation, the quantity of air
toxics emitted can be estimated by multiplying the number of acres burned
in each county by a fuel loading factor and the emission factor for each
pollutant. The acreage burned can be obtained from NEDS, along with the
estimated VOC emissions. Emission estimates of semivolatiles can be
obtained either directly by using the emission factors provided in
Table 7-1. Emissions for a subset of volatile organic compounds (VOC's),
by the data contained in Tables 7-2 and 7-3.
Alternatively, instead of relying on NEDS data, Table 7-2 identifies
the percentage by weight of various VOC's emitted from ponderosa loggings
slash materials collected from the San Bernadino National Forest and
2
burned under controlled laboratory conditions. Table 7-3 is a summary
of total hydrocarbon emission factors for forest wildfires as a function
of geographical area. Wildfire emissions of a compound listed
6/88 -. FOREST FIRES AND AGRICULTURAL BURNING 7-2
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Table 7-1 Emission Factors Used to Estimate Emissions from
Wildfires, Managed Burning, and Agricultural Burning
Emission factor
Air toxic (kg/MT dry fuel)
Anthracene 2.5 x 10
Benzo(a)anthracene 3.1 x 10
Benzo(a)f luoranthene 1.3 x 10
Benzo(k)f luoranthene 1.3 x 10
Benzo(ghi)perylene 2.5 x 10
-4
Benzo(a)pyrene 7.4 x 10
Cnrysene 3.1 x 10
Fluoranthene 5.5 x 10
Indeno(l,2,3-cd)pyrene 1.7 x 10 J
Phenanthrene 2.5 x 10
Pyrene 4.6 x 10
Emission factor
(Ib/ton dry fuel)
5.0 x 10"3
6.2 x 10~3
2.6 x 10"
2.6 x 10"J
.5.0 x 10'3
1.5 x 10'3
6.2 x 10"3
1.1 x 10"2
2.4 x 10*
5.0 x 10~3
9.2 x 10"3
Source: Reference 4.
6/88 - FOREST FIRES AND AGRICULTURAL BURNING 7-3
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Table 7-2 Summary of Hydrocarbon Emission Factors
for Forest Wildfires3
Geographic area
Emission factors, kg/hectare
Hydrocarbons
Rocky Mountain
.group
Northern.
Region 1
Rocky Mountain,
Region 2
Southwestern,
Region 3
Intermountain.
Region 4
996
1.620
808
269
215
Pacific group
Cal iforma,
Region 5
Alaska,
Region 10
Pacific N.W..
Region 6
512
485
431
1.620
Southern group
Southern,
Region 8
242
242
North Central group
Eastern, Region 9
(Both groups are in
Region 9)
296
296
Eastern group
(With Region 9)
296
Total United States
458
aAreas consumed by wildfire and emissions are for 1971.
Geographic areas are defined in Figure 7-1
Source: Reference 1.
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7-4
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Table 7-3 Volatile Organic Species Profile
from Typical Forest Wildfires
Chemical name
Isomers of pentane
Propane
N-Butane
Isobutane
Isomers of butene
Ethylene
Propylene
Butene
1 ,3-Butadiene
3-Methyl-l-butene
Unidentified hydrocarbons
Acetylene
Methylacetylene
Methane
Ethane
Percent weight
15
.35
.24
.11
.92
19.11
3.93
.81
.52
.17
44.59
8.40
.41
9.82
10.47
Source: Reference 3
6/88 -. FOREST FIRES AND AGRICULTURAL BURNING
7-5
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in Table 7-2 can be estimated by simply (1) multiplying the "percent
weight" term for that compound by the hydrocarbon emission factor
corresponding to the geographical area of interest and (2) multiplying
that product by the estimated acreage of the wildfire. This procedure is
illustrated in Example 2 in this section.
As noted earlier, NEDS lists the acreage, tons of growth burned per
acre, and VOC emissions. In most cases these data are adequate.
For forest "wildfires," estimates of the quantity and types of growth
burned in a given area can also be obtained from the U.S. Forest
Service's state forestry or agricultural department, or from local fire
protection agencies. For localities where estimates are not available,
2
the U.S. Forest Service annually publishes Wildfire Statistics, which
gives the total acreage burned in each state. Although this document
does not include data for each county, local fire and forestry officials
can usually provide county-specific estimates. If sufficient information
cannot be obtained from local officials, the state total from Wild Fire
Statistics should be apportioned to counties according to forest acreage
per county.
Determination of tons of growth burned per acre ("fuel loading") is
equally important, and local officials should be contacted for this
information. The emissions in the study area are then obtained by
multiplying the appropriate emission factor by the fuel loading factor,
then multiplying this product by the amount of forest acreage burned.
Average fuel loadings for the various U.S. Forest Service regions are
presented in Table 7-4.
Slash Burning and Agricultural Field Burning. Wastes from logging
operations are often burned under controlled conditions to reduce
6/88 - FOREST FIRES AND AGRICULTURAL BURNING 7-6
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Table 7-4 Summary of Estimated Fuel Consumed
by Forest Fires
Area and region
Eastern group
Estimated average fuel loading
MT/hectare ton/acre
Rocky Mountain
Region r
Region 2:
Region 3:
Region 4:
Pacific group
Region 5:
Region 6:
Region 10:
Southern group
Region 8:
group
Northern
Rocky Mountain
Southwestern
Inter-mountain
Cal ifornia
Pacific Northwest
Alaska
Coastal
Interior
Southern
83
135
67
22
40
43
40
135
36
135
25
20
20
37
60
30
10
8
19
18
60
16
60
11
9
9
25
11
North Central group
Region 9: Conifers
Hardwoods
25
22
27
11
10
12
6/88
a Geographical areas are defined in Figure 7-1.
Source: Reference 1
"- FOREST FIRES AND AGRICULTURAL BURNING
7-7
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10
JUNEAU
• HEADQUARTERS
_ REGIONAL BOUNDARIES
Figure 7-1 Forest Area and U.S. Forest Service Regions
6/88
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7-8
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the potential fire hazard in forests and to remove brush that can serve
as host for destructive insects. As with forest fires, NEDS provides
data on the acreage and tons of growth burned per acre, and the estimated
VOC emissions. If NEDS data are not used, Officials of the U.S. Forest
Service or the state forestry department can be contacted for estimates
of the area burned and quantity of slash burned per acre. If an estimate
of the quantity of slash burned per acre cannot be obtained from other
sources, a rough value of 75 tons per acre can be used.
Also included in this source category are agricultural field burning
operations such as stubble burning and burning of land-clearing refuse.
Little published information is available on this subject, so burning
activity estimates must be determined through state agriculture
departments or extension services.
Acreage and average fuel loadings should be estimated. The U.S. Soil
Conservation Service should be able to provide some of this information.
Average fuel loadings and organic emission factors for various wastes are
provided in Section 2.4 of Reference 1. In some cases, agricultural
burning may be reported under residential open burning.
7.4 Example Calculations
Example Calculation 1
By assuming that a wildfire in a county located in the Pacific
Northwest consumes 1,735 hectares, one can estimate the quantity of
Benzo[a]anthracene (BaA) emitted. Using Table 7-1, the total quantity
emitted can be calculated as follows:
Total BaA = 3.1xlO'3kg BaA x 1,735 hectares x 60MT fuel*
MT dry fuel hectare
Total BaA = 3.2 x IQ/kg BaA emitted.
* From Table 7-4
6/88 . FOREST FIRES AND AGRICULTURAL BURNING 7-9
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In a similar manner, emissions can be estimated for the other
pollutants shown in Table 7-1, as follows:
Anthracene 260 kg = 0.3 MT
Benzo(a)fluoranthene 135 kg * 0.1 MT
Benzo(k)fluoranthene 135 kg = 0.1 MT
Benzo(ghi)perylene 229 kg = 0.2 MT
Benzo(a)pyrene 770 kg » 0.8 MT
Chrysene 323 kg = 0.3 MT
Fluoranthene 572 kg = 0.6 MT
Indeno(l,2,3-cd)Pyrene 177 kg = 0.2 MT
Phenanthrene 260 kg = 0.3 MT
Pyrene . 479 kg = 0.5 MT
Example Calculation 2
NEDS reports that a wildfire in a county in Alaska produces 1,208
tons of VOC emissions annually; one can estimate the quantity of
1,3-butadiene using the speciation factor provided in Table 7-2.
Total 1,3-Butadiene = (1208 tons/yr) (907 kg/ton) (0.0052 kg/kg of VOC)
= 5.7
In a similar manner, emissions can be estimated for the other
pollutants in cited Table 7-2, as follows:
Isomers of pentane 1.6 x 10 kg
Propane 3.8 x 103 kg
N-Butane 2.6 x 103 kg
Isobutane 1.2 x 103 kg
Isomers of butene 1.0 x 10 kg
Ethylene 2.1 x 105 kg
Propylene 4.3 x 10 kg
Butene • 8.9 x 103 kg
*
From Table 7-2.
6/88 FOREST FIRES AND AGRICULTURAL BURNING 7-10
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3-Methyl-l-butene 1.9 x 103 kg
Acetylene 9.2 x 104 kg
Methy acetylene 4.5 x 10 kg
Methane 1.1 x 105 kg
Ethane 1.2 x 105 kg
Unidentified hydrocarbons 4.9 x 10 kg
7.5 Methods to Apportion Countywide Emissions from Forest Fires and
Agricultural Burning
As described in Section 1.0 and Appendix A when performing air
dispersion modeling, it is generally recommended that countywide
emissions be distributed within the study area into rectangular area
source grid cells reflecting spatial variations in factored into the
modeling to reflect seasonal or diurnal fluctuations in emissions.
Modeling results would then reflect on-going activities in that portion
of the county, e.g., residential heating in the winter, commercial
solvent usage during working hours on weekdays.
There are three alternative approaches that can be used in spatially
distributing emission: (1) population, i.e., the magnitude of emissions
within a grid are directly proportional to the population living in the
grid, (2) land area, i.e., emissions from a countywide area source are
assumed to be uniform throughout the county and are distributed based on
the size of the area source grid, and (3) land use patterns that assume
that certain area source activities, most likely to occur in certain
areas of the county, e.g., commercial, residential or industrial.
In apportioning emissions from agricultural burning, and of these
methods may be appropriate. Land area and population data can be readily
obtained, and applied as described in Appendix A. Land use data,
available from the U.S. Geological Survey and other sources can be used
6/88 - FOREST FIRES AND AGRICULTURAL BURNING 7-11
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in combination with the spatial distribution for agricultural burning, to
distribute emissions based on the type of activity being performed, as
shown in Table 7-5.
Seasonal, daily, and hour temporal resolution are also included in
Table 7-5, and can be used with the annual countywide emissions data to
estimate temporal variations.
6/88 - FOREST FIRES AND AGRICULTURAL BURNING 7-12
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Table 7-5 Spatial and Temporal Resolutions
for Agricultural Burning
Spatial Resolution
Surrogate indicator: areas where these activities occur
Information source(s): U.S. Forest Service, state forestry
departments, state agricultural
department, extension services, citrus
grove operations, and land use map
Temporal Resolution
Seasonal, and Daily: Base on local regulations and on data
collected from information sources.
Hourly: N/A
6/88 FOREST FIRES AND AGRICULTURAL BURNING 7-13
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REFERENCES
1. U.S. Environmental Protection Agency. Compilation of Air Pollution
Emission Factors, Volume I: Stationary Point and Area Sources
(AP-42) Fourth Edition. EPA-460/3-81-005. Office of Air Quality
Planning and Standards. Research Triangle Park, NC. 1985.
2. U.S. Environmental Protection Agency. Volatile Organic Compound
(VOC) Species Data Manual. Second Edition. EPA-450/3-81-005.
Office of Air Quality Planning and Standards. Research Triangle
Park, NC. 1980.
3. U.S. Department of Agriculture, Forest Service. Wildfire Statistics
(Annual]. Washington, DC.
4. Arthur D. Little, Inc. An Exposure and Risk Assessment for
Benzofalpyrene and Other Polvcvlic Aromatic Hydrocarbons, Volume IV,
Benzofalpyrene, Acenaphthylene. BenzFalanthracene,
Benzofblfluoranthene. Benzol" blfluoranthene, Benzofklfluoranthene,
Benzofg,h,i1pery1ene. Chrvsene, Pibenzfa.hi anthracene, and
Idenori.2.3-c.d1pyrene. U.S. EPA Contract No. 68-01-6160. U.S.
Environmental Protection Agency, Office of Water Regulations and
Standards. Washington, D.C. 1982.
5. U.S. Environmental Protection Agency. Guidelines for the Preparation
of Emission Inventories for Volatile Organic Compounds Volume II:
Emission Inventory Requirements for Photochemical Air Quality
Simulation Models. EPA-450/4-78-018. U.S. Office of Air Quality
Planning and Standards. Research Triangle Park, NC. September 1979.
6/88 FOREST FIRES AND AGRICULTURAL BURNING 7-14
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8. GASOLINE SERVICE STATIONS (GASOLINE MARKETING)
8.1 General
Air toxics are emitted from gasoline stations as a result of (1)
underground storage tank filling, (2) underground storage tank breathing,
and (3) vehicle refueling. The quantity of gasoline vapor released from
each of these sources is affected by the method and rate of tank filling,
tank geometry, and quantity of gasoline added. The amount of any one
toxic chemical released.with the vapor depends on such factors as the
initial concentration of the chemical in the gasoline, the vapor-liquid
equilibrium of the system, and the temperature within the tank.
Gasoline is generally transported to retail sales outlets in
8,000-gallon tank trucks. When these trucks unload the gasoline into.
underground storage tanks, gasoline vapor in the storage tank is
displaced by the liquid gasoline and vented to the atmosphere. The
underground storage tank may be filled by either a splash or a submerged
method.
With the splash filling method, the fill pipe ends above the level of
the gasoline in the tank so that, as gasoline enters the tank, it
.splashes into the liquid already in the tank, causing turbulent mixing
and additional vaporization of volatiles. The displaced vapors are then
lost through the hatch.
Submerged filling lessens the amount of vaporization because the fill
pipe extends below the liquid level. Although this method avoids the
turbulent splattering of the splash method, emissions of displaced vapors
are still not controlled.
One control method that avoids this problem is a vapor balance system
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wherein gasoline vapors are returned to the tank truck and the
underground tank is equipped with a pressure relief vent. This method of
submerged filling is 93 to 100 percent efficient at controlling vapor
emissions.
In 1980, an estimated 70 to 95 percent of the service stations used
submerged filling techniques, with the balance using splash filling.
Only a very small number used the vapor balance method. Recent trends
show a move toward submerged and vapor balanced methods and away from the
splash technique. Current local data on the filling techniques and
control methods should be used whenever possible.
Underground storage tank breathing losses result from daily changes
in temperature and barometric pressure, which change the vapor-liquid
equilibrium of the system and cause expansion and contraction of the
vapors. Expansion forces vapors out of the tank and into the
atmosphere. When the vapor in the tank contracts, however, fresh air is
drawn into the tank, and volatilization increases until equilibrium is
again reached. This cycle repeats with daily environmental changes. The
quantity of fresh air introduced into the tank when gasoline is withdrawn
also increases the amount of evaporation and, thus, breathing losses.
Vehicle refueling also results in the emission of vapors to the
atmosphere because the vapors present in the automobile gas tank are
displaced by gasoline and because gasoline spilled during refueling
evaporates. Emissions of displaced vapors can be controlled by conveying
the displaced vapors back to the underground storage tank through a
specially-designed hose and nozzle. This conveyance can either be caused
by a natural pressure differential established during gasoline transfer
(as with the vapor balanced storage tank fill method) or by a
vacuum-assisted method.
6/88 .GASOLINE SERVICE STATIONS (GASOLINE MARKETING) 8-2
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8.2 Factors
Emission factors relating the quantity of benzene,
1,2-dichloroethane, (ethylene dichloride), and ethylene dibromide (EDB)
released from sources within gasoline service stations to the volume of
gasoline flowing through the system are presented in Table 8-1. In this
table apportionment factors have been applied, where appropriate, to the
estimated quantity of gasoline vapors emitted from each source. In order
for these factors to be useful, the quantity of gasoline flowing through
the system must be known. This quantity can be approximated by using the
quantity of gasoline sold within a given study area, as provided in NEDS
or other data sources.
Estimates of VOC emissions can be speciated using factors being
developed by OAQPS.2 The speciation profile for gasoline marketing is
presented in Table 8-2. It should be noted that the benzene speciation
factor is approximately five times greater in Reference 2 than it is in
Reference 1; this discrepancy is probably at least in part attributable
to the large variation in gasoline compositions.
8.3 Methodology Options
As noted earlier, NEDS contains data on the quantities of gasoline
marketed in a county (as well as estimated VOC emissions). In most
cases, these data are considered to be adequate. However, if NEDS
estimates are believed to be out of date, or unreliable for other
reasons, the quantities of gasoline sold in a study area can be estimated
using one of several methods described below (in order of preference):
Distributor Data. Data from the gasoline distributor provide the
most accurate source of gasoline use figures because they are based on
the actual quantity of gasoline passing through the system rather than on
the amount sold. Unfortunately, these data are not usually available for
all areas of the country.
6/88 -GASOLINE SERVICE STATIONS (GASOLINE MARKETING) 8-3
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Table 8-1 Selected Air Toxic Emissions from Gasoline Stations3
Emission source
Benzene emissions
(g/Db
(lb/gal)
Ethylene dichloride
emissions
(g/Dc
(lb/gal)
Ethyene dibromide
emissions
(g/D
! lb/gal)
Filling Underground Storage Tanks
Submerged
Splash
Vapor balance
(submerged)
Breathing
Losses
Vehicle Refueling
Uncontrolled
displacement
Controlled
displacement
Spillage
5.28 x
(4.4 x
8.28 x
(6.9 x
2.4 x
(2.0 x
7.2 x
(6.0 x
7.92 x
(6.6 x
7.92 x
(6.6 x
4.8 x
(4.0 x
ID'3
10'5)
io-35
10 5)
ID'4
10'5)
ID'4
10'6)
ID"3
10"5)
ID'4
10"6)
10~46
10'6)
4.4 x
(3.7 x
6.9 x
(5.8 x
2.0 x
(1.7 x
6.0 x
(5.0 x
6.6 x
(5.5 x
6.6 x
(5.5 x
4.0 x
(3.3 x
ID'4
ID'6
10"46
10 6)
ID'5
ID'7)
io-5
103)
io-4
IO"6)
ID'5
10"3)
IO-5
10"3)
4.4 x
(3.7 x
6.9 x
(5.8 x
2.0 x
(1.7 x
6.0 x
(5.0 x
6.6 x
(5.5 x
6.6 x
(5.5 x
4.0 x
(3.3 x
ID'5
ID'7)
ID'5
1Q-7)
io-6
10'8)
ID'6
10"8)
1C'5
10"7)
io-6
10"8)
ID'6
10'8)
Emission factors given in units of grams of toxic vapor released per liter of
gasoline passing through the system.
bBased on the apportionment factor, 6.0 x 10"3 MT benzene/MT VOC (Reference 1 in
conjunction with emission factors from AP-42. (Reference 4)
GBased on the apportionment factor, 5.0 x 10"4 MT ethylene dichloride/MT VOC
(Reference 1). in conjunction with emission factors from AP-42. (Reference 4)
Based on the apportionment factor, 5.0 x 10 MT ethylene dibromide/MT VOC
(Reference 1), in conjunction with emission factors from AP-42. (Reference 4)
6/88
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Table 8-2 VOC Special ion Factors for Gasoline Marketing
Species Name Percent Weight
Isomers of Hexane 0.10
Isomers of Decane 0.10
Isomers of Undecane 0.09
Isomers of Undecane 0.00
Isomers of Dodecane 0.00
Isomers of Dodecane 0.05
Isomers of Tetradecane 0.02
C-7 Cycloparaffins 0.05
C9 Olefins 0.08
C9 Olefins 0.01
C9 Olefins 0.01
C9 Olefins 0.00
CIO Olefins 0.04
CIO Olefins 0.00
CIO Paraffin 0.00
CIO Paraffin 0.00
CIO Paraffin 0.00
C9 Paraffin 0.48
C-8 Olefins 0.00
C-8 Olefins 0.21
C8 Paraffin 3.84
C7 Paraffin 0.04
C5 Olefin 1.91
C5 Paraffin 2.09
C5 Paraffin/Olefin 1.08
Cll Olefin 0.00
Cll Olefin 0.01
Cll Olefin 0.04
C9H16 0.00
C9H16 0.02
C9H16 0.00
C8H14 0.00
Butene 0.14
Hexane 3.91
Heptane 1.84
Cyclopentane 0.16
Methylcyclohexane 0.21
Methylcyclopentane 0.68
Heptene 0.03
Methylcyclopentene 0.45
6/88 GASOLINE SERVICE STATIONS (GASOLINE MARKETING) 8-5
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Table 8-2 (Continued)
Species Name Percent Weight
Cyclohexene
Ethyl eye lohexane
Cyclopentene
C7H120
Dimethylcyclobutanone
Isomers of Butylbenzene
Isomers of Butylbenzene
Isomers of Oi ethyl benzene
Trimethylbenzene
Isomers of Propylbenzene
C10H12
C10H10
C10H10
Benzene
Toluene
Ethyl benzene
0-Xylene
Cunene (Isopropyl Benzene)
Styrene
Methyl Styrene
Ethyltoluene
Propylbenzene
Ethyldimethylbenzene
Tetramethyl benzene
CS-Alkylbenzene
C5-Alkylbenzene
C5-Alkylbenzene
C5-Alkylbenzene
C5-Alkylbenzene
C5-Alkylbenzene
C5-Alkylbenzene
C5-Alkylbenzene (Unsat.)
C6-Alkylbenzene
C6-Alkylbenzene
C6-Alkylbenzene
C6-Alkylbenzene
C6-Alkylbenzene
C6-A1ky1benzene
C4-Alkylstyrene
C4-Alkylstyrene
C4-Alkylstyrene
C4-Alkylstyrene
0.04
0.08
0.18
0.04
0.05
3.18
0.03
0.02
4.29
0.76
0.04
0.00
0.00
3.25
15.22
4.07
6.41
0.33
0.17
0.05
3.61
0.92
1.24
1.03
0.35
0.02
0.04
0.05
0.83
0.05
0.09
0.05
0.00
0.06
0.00
0.03
0.02
0.00
0.04
0.02
0.00
0.01
6/88 ".GASOLINE SERVICE STATIONS (GASOLINE MARKETING) 8-6
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Table 8-2 (Continued)
Species Name Percent Weight
C7-Alky1benzene 0.00
Benzaldehyde 0.00
Chlorobenzene 0.03
Oimethylnaphthyndine 0.01
Napthalene 0.80
Methyl Naphthalenes 0.64
C2-Alkylnapthalene 0.10
Methylindan 0.01
Methylindan 0.52'
Methylindan 0.00
Methyldihydronaphthalene 0.01
Dimethylindan 0.00
Dimethylindan 0.42
Dimethylindan 0.00
Dihydronapthalene 0.06
Dimethylindene 0.01
Ethylindan 0.04
Tnmethyl indan 0.06
M-Xylene and P-Xylene 15.28
Methylpropane 2.65-
Methylpropene 0.14
Methylbutene 0.06
Methylbutadiene 0.01
Methylpentene 0.48
Methylpentene 0.41
Methylpentane 1.76
Methylcyclopentadiene 0.04
Methylhexane 1.68
Methylhexene 0.00
Methylhexene 0.03
Methylhexadiene 0.25
Methylcyclohexadiene ' 0.02
Methylhexanal 0,92
Methylheptyne 0.02
Methytheptane 0.35
Methylcyclohexene 0.14
Methylnonane 0.21
Methyldecane 0.12
Pentenyne 0.03
Hexene 0.40
6/88 GASOLINE SERVICE STATIONS (GASOLINE MARKETING) 8-7
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Table 8-2 (Continued)
Species Name Percent Weight
Hexadienal 0.03
Heptadienal 0.02
Dimethylbutane 2.29
Dimethylbutene 0.30
Dimethylpentane 0.36
Dimethylpentene 0.02
Dimethylcyclopentane 0.15
Dimethylcyclopentene 0.22
Dimethylcyclopentene 0.09
Dimethylhexane 0.48
Dimethylhexane • 0.28
Dimethylhexadiene 0.10
Dimethylethylcyclohexane 0.09
Oimethyloctane 0.04
Dimethyloctane 0.02
Oimethylundecane 0.00
Oimethyldecane Q.Q7
Ethylpentene 0.03
Ethylcyclopentene 0.06
Ethylmethylcyclopentane 0.12
Ethylhexane 0.24
Ethylmethylhexane 0.21
Ethylmethylcyclohexane 0.04
Ethylmethylcyclohexane 0.02
Ethylheptane 0.02
Ethylmethyloctane 0.02
Ethylbicycloheptane 0.01
Ethyldimethylpentane 0.13
Tetramethylcyclobutene 0.04
Tnmetnylpentane 0.68
Trimethylpentadiene 0.05
Tnmethylheptane 0.09
Trimethylheptane 0.05
Trimethylhexene 0.04
Trimethyloctane 0.07
Trimethyldecane 0.03
Octatnene 0.01
Nonene 0.03
Pentadiene • 0.04
Methyloctane 0.55
Indane 0.44
6/88 GASOLINE SERVICE STATIONS (GASOLINE MARKETING) 8-8
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Table 8-2 (Continued)
Species Name Percent Weight
Tnmethylcyclopentane 0.09
Dimethylcyclohexane 0.10
Tnmethylcyclohexane 0.02
Dimethyl heptane • 0.16
Unidentified 0.00
Source: Reference 2
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Fuel Tax Data. Fuel tax data, on the other hand, are readily
available through state fuel tax offices. These data provide tax
statistics for local political jurisdictions. Therefore, because tax is
collected for each gallon sold, gasoline consumption can be
back-calculated with the tax formulas from each jurisdiction. Care must
be taken, however, that the local jurisdictions of interest have
comparable tax bases. For instance, gasoline sold to government
agencies, or for nonhighway use, may not be taxed in one jurisdiction,
but may be taxed in another.
Questionnaires. If the area sources of interest do not correspond
directly with a local tax area, and if the sources are relatively few in
number, direct questionnaires concerning gasoline volumes distributed may
be useful. An example of a situation for which this method may be
helpful is if the investigator is concerned only with emissions resulting
from gasoline sales by convenience stores within a three-county area.
Advantages of this type of data include the accuracy of the results and
the flexibility to ask particular questions, such as emission control
practices and number of employees. Obvious administrative and analytical
difficulties limit the usefulness of this data source.
Publications. National publications also provide data on gasoline
consumption and sales. The Federal Highway Authority publishes Highway
Statistics, containing state consumption data. These state data can
be apportioned to local areas if the percent of state gasoline sales
occurring within each jurisdiction can be determined. Other
apportionment factors such as vehicle miles traveled, registered
vehicles, or population within the local jurisdiction, can be used if
6/88 ^ASOLINE SERVICE STATIONS (GASOLINE MARKETING) 8-10
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they are more appropriate for a particular area. Countywide gasoline
sales data are available in the Census of Retail Trade. ' '
8.4 Example Calculation
Analysis of fuel tax data for the county of concern showed that
Q
2.78 x 10 liters of gasoline were sold in that county in 1986. It was
also determined that approximately 90 p_ercent of the stations were
equipped for submerged fueling of underground storage tanks, 5 percent
used splash filling techniques, and 5 percent used a vapor balanced
technique. In addition, .only 10 percent of the stations were equipped
with pump nozzles that controlled refueling losses. Benzene emissions
from gasoline service stations in this county can be estimated as
follows, based on emission factors provided in Table 8-1.
(1) Filling of underground storage tanks
(a) Submerged
(5.28 x 10"3 grams of benzene/liter) x (2.78 x 109 liters)
x 0.90
= 1.32 x 10^ grams of benzene/year
(b) Splash
(8.28 x 10'3) x (2.78 x 109) x 0.05
= 1.15xl06 grams of benzene/year
(c) Vapor Balanced
(2.4 x 10'4) x (2.78 x 109) x 0.05
= 3.34xl04 grams of benzene/year
(2) Breathing losses
(7.2 x 10'4) x (2.78 x 109)
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= 2.00 x 106 grams of benzene/year
(3) Vehicle refuel ing
(a) Uncontrolled
(7.92 x 1CT3) x (2.78 x 109) x 0.90
= 1.98x10? grams of benzene/year
(b) Controlled
(7.92 x 10'4) x (2.78 x 109) x 0.10
= 1.98x106 grams of benzene/year
(4) Spillage
(4.8 x 10'4) x (2.78 x 109)
= 1.33x10^ grams of benzene/year.
The total countywide emissions of benzene from gasoline service
stations can be estimated by summing the component emissions as shown:
(1.32 x 107)+(1.15 x 105)+(3.34 x 104)+(2.00 x 106) + (1.98 x 107) +
(1.98 x 106) + (1.33 x 106)
= 3.95 x 10 grams of benzene/year
= 39.5 MT benzene/year.
Similarly, emissions of 1,2 dichoroethane are estimated to be
3.3 MT/yr, and emissions of ethylene dibromide are estimated to be
0.3 MT/yr.
8.5 Methods to Apportion Countvwide Emissions from Gasoline Marketing
As described in Section 1.0 and Appendix A when performing air
dispersion modeling, it is generally recommended that countywide
emissions be distributed within the study area into rectangular area
source grid cells reflecting spatial variations in activity and
emissions, similarly temporal in activities can be factored into the
modeling to reflect seasonal or diurnal fluctuations in emissions.
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Modeling results would then reflect on-going activities in that portion
of the county, e.g., residential heating in winter, commercial solvent
usage during working hours on weekdays.
There are three alternative approaches that can be used in spatially
distributing emission: (1) population, i.e., the magnitude of emissions
within a grid, (2) land area, i.e., emissions from a countywide area
source are assumed to be uniform throughout the county and are
distributed based on the size of the area source grid, and (3) land use
patterns, assume that certain area source activities, most likely occur
in certain areas of the county, e.g., commercial, residential or
industrial.
In apportioning emissions from gasoline marketing, any of these
methods may be appropriate. Land area and population data can be readi.ly
obtained, and applied as described in Appendix A. Land use data,
available from the U.S. Geological Survey and other sources can be used
in combination with the spatial resolution for gasoline marketing, to
distribute emissions based on the type of activity being performed, as
shown in Table 8-3.
Estimated seasonal, daily, and hourly temporal resolution for
gasoline marketing are .also included in Table 8-3, and can be used with
the annual countywide emissions data to estimate temporal variations.
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Table 8-3 Spatial and Temporal Resolutions
for Gasoline Marketing
Spatial Resolution
Surrogate indicator: Industrial and commercial/institutional
land use areas (Codes 12, 13, and 15}
Information source(s): land use map and Reference 14
Temporal Resolution
Seasonal: uniform through the year
Daily: Monday through Saturday
Hourly: uniform from 0600 to 2000, otherwise
zero
6/88 GASOLINE SERVICE STATIONS (GASOLINE MARKETING) 8-14
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REFERENCES
1. U.S. Environmental Protection Agency. Evaluation of Air Pollution
Regulatory Strategies for the Gasoline Marketing Industry.
450/3-84-012a. Office of Air and Radiation. Washington, DC. 1984.
2. Air Emissions Species Manual, Volume I: Volatile Organic Compound
(VOC) Species Profiles And Volume II; Particulate Matter (PM) Species
Manual. EPA-450/2-88-003a and b, U. S. Environmental Protection Agency,
Research Triangle Park, NC, April 1988.
3. U.S. Environmental Protection Agency. Procedures for the Preparation
of Emission Inventories for Volatile Organic Compounds, Vol. I. EPA
450/2-770-028. Office of Air Quality Planning and Standards.
Research Triangle Park, NC. 1980.
4. U.S. Environmental Protection Agency. Compilation of Air Pollutant
Emission Factors. Vol. I: Stationary Point and Area Sources (AP-42).
Fourth Edition. EPA-460/3-81-005. Office of Air Quality Planning
and Standards. Research Triangle Park, NC. 1985.
5. U.S. Department of Transportation. Highway Statistics. Federal
Highway Administration, Washington, DC. Annual.
6. U.S. Department of Commerce. Census of Retail Trade. Bureau of
Census. Washington, DC. Quinquennial.
7. GCA Technology Division, Inc. Area Source Documentation for 1985
National Acid Precipitation Assessment Program Inventory. Office of
Research and Development. Washington, DC. 1986.
8. U.S. Environmental Protection Agency. Procedures for the Preparation
of Emission Inventories for Volatile Organic Compounds Volume II:
Emission Inventory Requirements for Photochemical Air Quality
Simulation Models. EPA-450/4-79-015. U.S. Office of Air Quality
Planning and Standards. Research Triangle Park, NC. September 1979.
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9. CHROMIUM ELECTROPLATING
9.1 General
The chromium electroplating source category includes two distinct
types of plating operations: hard and decorative. In hard plating, the
substrate (usually steel) is plated with a relatively thick layer of
chromium to provide wear resistance, low coefficient of friction,
hardness, and corrosion resistance or to build up surfaces that have been
eroded by use. Hard plating is used for items such as hydraulic
cylinders and rods, industrial rolls, zinc die castings, plastic molds,
engine components, and marine hardware. In decorative plating, the
substrate (e.g., brass, steel, aluminum, or plastic) is plated with a
layer of nickel followed by a relatively thin layer of chromium to
provide a bright, tarnish-resistant surface. Decorative plating is used
for items such as automotive trim, metal furniture, bicycles, hand tools,
and plumbing fixtures. Although other types of operations performed at
electroplating plants involve chromium in some form, this source category
includes only those processes that use chromic acid in an electrolytic
cell to deposit chromium metal on a product.
There are approximately 4,500 chromium electroplating operations
in the country. Chromium electroplating is used in the manufacture of a
wide variety of industrial and consumer items. In general, chromium
plating operations are located at or near the industries they service,
which are usually in centers of high population density. Plating
operations range in size from small shops operating one tank for as few
as 15 hours per week to large shops operating several tanks for as many
as 130 hours per week. Most plating operations are "captive" processes
performed within larger manufacturing facilities. Some operations are
"job shops" that provide custom plating services for many different
clients. Captive platers and job shops may perform either hard plating,
decorative plating, or both.
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The actual chromium plating process is similar for hard and
decorative plating, although pretreatment processes and operating
parameters may differ somewhat. The plating process involves dipping the
item to be plated in a tank containing chromic acid solution and a small
amount of sulfuric acid as a catalyst. Electric current passed through
the lead anodes causes chromium to deposit out of solution onto the
substrate, which acts as the cathode. (In the case of plating a plastic
substrate, the pretreatment process includes steps to render the surface
conductive so that it can act as the electrical cathode.)
The chromium plating process is inefficient. Only 10 to 20 percent
of the electric current supplied to the anodes is used to deposit
chromium onto the item; the rest produces chemical reactions that
generate hydrogen gas at the surface of the cathodes and oxygen gas at
the surface of the anodes. Efficiency can be improved in some situations
by using fluoride rather than sulfuric acid as the catalyst in the
plating solution. Fluoride cannot be used in all types of plating
solutions, however, and may cause "etching" or "burning" of exposed steel
surfaces if used in hard plating solutions.
9.2 Factors
Hexavalent chromium is emitted during the chromium electroplating
process. It can be seen as a yellow mist that is formed when hydrogen
gas is released through the surface of the plating solution.
Additionally, oxygen bubble formation and plating bath evaporation
contribute to chromium emissions; however, their contribution is
negligible when compared to emissions related to hydrogen gas generation.
The amount of mist generated and consequently the amount of
hexavalent chromium emitted depends on several factors: (1) the
magnitude of the current supplied to the anodes, (2) the surface area
plated, (3) the duration of electrolysis, (4) the quantity of chromic
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acid consumed, and (5) the efficiency of any mist control systems.
Emissions factors that can be used to estimate the quantity of hexavalent
chromium emitted from uncontrolled hard and decorative plating operations
are presented in Table 9-1. These factors were derived from EPA source
tests conducted in Greenville, South Carolina, and Sterling Heights,
Michigan.
9.3 Methodology Options
A reasonable method of estimating chromium emissions is based on
population density, because chromium electroplating operations are used
by many different industries and are usually located in centers of high
population density. According to OAQPS 147,000 kg of hexavalent chromium
are emitted by electroplaters. This estimate of 147,000 kg/yr of Cr
was calculated by OAQPS based on the emission factors provided in
Table 9-1, and assumed that hard platers had the following levels of
control:, scrubber (40%), fume suppressant (15%), mist eliminator (15%)
and uncontrolled (30%). Decorative platers were assumed to have the
following levels of controls: scrubbers (35%), fume suppressnat (50%),
and uncontrolled (15%). It was also assumed that scrubbers are 95
percent effective in reducing Cr emissions; mist eliminators are 85
percent effective; and fume suppressant, 90 percent effective.
Based on the United States population of 2.265 x 10 thousand
persons, the per capita quantity of chromium emitted annually can be
calculated at 6.5 x 10"1 kg Cr^/lOOO persons (1.4 x 10"1 Ib
Cr+ /I,000 persons). The population of a given county can be obtained
from U.S. Census data and multiplied by this per capita emission factor
to estimate the amount of Cr emitted from plating operations in the
county.
6/88 -. CHROMIUM ELECTROPLATING 9-3
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Table 9-1 Uncontrolled Emission Factors Used to Estimate
Emissions from Chromium Electroplating Operations
Type of operation
mg/Cr /ampere
hour
Basis
Hard
10
EPA source test at
Carolina
Plating—Roll
Division plant in
Greenville, South
Carolina.
Decorative
EPA source test at
C. S. Ohm
Manufacturing
Company plant in
Sterling Heights,
Michigan.
Based on the assumption that the fume suppressant used during the test
controlled 80 percent of the misting.
Source: Reference 2.
6/88
CHROMIUM ELECTROPLATING
9-4
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9.4 Example Calculation
Given that a county has 33,345 residents, the chromium emission can
be estimated as follows:
Chromium emitted = 33.345 (thousand persons) x 1.4 Ib of Cr+6/1000 persons
= 46.7 Ib Cr+6 emitted annually.
9.5 Methods to Apportion Coimtywide Emissions from Chromium
Electroplating
As described in Section 1.0 and Appendix A when performing air
dispersion modeling, it is generally recommended that countywide emissions
be distributed within the study area into rectangular area source grid
cells reflecting spatial variations in activity and emissions. Similarly
temporal in activities can be factored into the modeling to reflect
seasonal or diurnal fluctuations in emissions. Modeling results would
then reflect on-going activities in that portion of the county, e.g.,
residential heating in the winter, commercial solvent usage during working
hours on weekdays.
There are three alternative approaches that can be used in spatially
distributing emission: (1) population, i.e'., the magnitude of emissions
within a grid are directly proportional to the population living in the
grid, (2) land area, i.e., emissions from a countywide area source are
assumed to be uniform throughout the county and are distributed based on
the size of the area source grid, and (3) land use patterns, that assume
that certain area source activities, most likely occur in certain areas of
the county, e.g., commercial, residential or industrial.
In apportioning emissions from chromium electroplaters any of these
methods may be appropriate. Land area and population data can be readily
obtained, and applied as described in Appendix A. Land use data,
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available from the U.S. Geological Survey and other sources can be used in
combination with the spatial reolution for chromium electroplaters, to
distribute emissions based on the type of activity being performed, as
shown in Table 9-2.
Estimated seasonal, daily and hourly temporal resolution for chromium
electroplaters are also included in Table 9-2, and can be used with the
countywide emissions data to estimate temporal variations.
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Table 9-2 Spatial and Temporal Resolution
for Chromium Electroplaters
Spatial Resolution
Surrogate indicator: commercial and industrial areas
(codes 12, 13, and 15)
Information source(s); land use maps
Temporal Resolution:
Seasonal: uniform through the year
Daily: 95 percent Monday through Friday,
5 percent Saturday
Hourly: 80 percent from 0700 to 1900, 20
percent from 1900 to 2400, otherwise
zero
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REFERENCES
1. U.S. Environmental Protection Agency. Chromium Electroplating NESHAP
Background Information Document. Chapters 3 through 5. Office of Air
Quality Planning and Standards. Research Triangle Park, NC. February
1987.
2. U.S. Environmental Protection Agency. Technical Paper: Chromium
Electroplating (unpublished). Office of Air Quality Planning and
Standards. Research Triangle Park, NC. 1985.
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10. HOSPITAL AND LABORATORY STERILIZERS
10.1 General
Ethylene oxide (EO) is a highly toxic compound that is widely used as
a fumigant and sterilant. It has been estimated that there are 7,000
potential emitters and that U.S. hospitals alone emitted 400 to
1 2
450 metric tons of EO in 1976. ' Research laboratories emitted an
2
additional 275 to 444 metric tons. Types of equipment that use
ethylene oxide include vacuum chambers, atmospheric chambers,
ampule/liner bags, and sterijet systems.
Vacuum chambers are pressure vessels, each with a vacuum pump that
removes air from the chamber prior to sterilization and removes the
EO/air mixture after sterilization. Units vary in size and design. For
example, small countertop models are primarily used in health care and
diagnostic facilities. Generally, these models have capacities of less
than 0.1 m . In hospitals, these units can be used in operating
rooms. The EO is supplied to the unit by single dose cartridges or
pressurized cylinders. Emissions occur when the EO is vented through a
2
length of tubing directly to the atmosphere.
Chambers from 0.1 m to 2.8 m are used primarily in hospital
central supply facilities. Ethylene oxide is provided from .pressurized
cylinders. Emissions occur when the chamber is vented directly to the
atmosphere. Also, emissions may be mixed with water and routed to a
2
sewer drain.
Since atmospheric chambers do not evacuate air before treatment, a
longer sterilization time is usually required. Ethylene oxide is
supplied as a gas mixture in a cartridge, and emissions occur when the
units vent their contents directly into the workplace. Other units
reduce emissions by manually pumping the chamber contents through a
2
charcoal adsorbent.
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Ampule/liner bags contribute to EO emissions. In this method, the
article to be sterilized and a broken ampule of 100 percent EO are placed
in a plastic liner bag. The bag is sealed and the EO escapes slowly into
2
the atmosphere.
•»
The sterijet system is used in hospitals and is similar to the
ampule/liner bag method. In this system the article to be sterilized is
placed in a pouch. It is attached to a gas delivery nozzle that draws a
slight vacuum on the pouch and then injects a premeasured amount of EO
mixture. The pouch is heat sealed, and emissions to the atmosphere occur
2
as EO diffuses through the pouch.
Other important emitters of EO are research laboratories. It has
been estimated that in 1976, research laboratories used between 275 and
2
444 metric tons of EO for sterilization. Emissions would result as
previously discussed for hospitals.
10.2 Emission Factors
Whenever possible, emissions of ethylene oxide from sterilizers
should be treated as a point source. Many of the emission factors and
procedures that are described in this section can be applied to a single
laboratory or hospital. When activity coefficients are available on a
point source basis, the preferred approach is to treat the source as a
point source, rather than an area source. When facility-specific data
are unavailable, the source can be incorporated into the area source
inventory.
Hospitals. Emission factors for estimating ethylene oxide emissions
from hospitals were developed based on the results of a study by Midwest
Research Institute (MRI) to estimate chlorinated fluorocarbon (CFC)
emissions that resulted from sterilization procedures at
6/88 : HOSPITAL AND LABORATORY STERILIZERS 10-2
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hospitals. Often, these sterilization processes use a mixture of
88 percent dichlorodifluoromethane (Freon ) and 12 percent ethylene
oxide (EO). This mixture is referred to as "12/88."
MRI estimated Freon emissions program to evaluate nationwide
ethylene oxide emissions. Based on their findings, 12/88 hospital usage
was divided into three categories:
(1) large hospitals (>500 beds), (2) medium hospitals (200 to 500 beds),
and (3) small hospitals (<200 beds). Hospitals do not emit sterilant at
the same rate, and a linear regression analysis indicated that for the
data from the Section 114 responses, 12/88 emissions are most closely
related to the number of beds at the hospital. The following ethylene
oxide emission factors are presented on a per bed basis:
• Large hospital 1.8 Ib/bed/yr
• Medium hospital 1.3 Ib/bed/yr
• Small hospital 1.7 Ib/bed/yr.
An alternative method of estimating ethylene oxide emissions uses a
countywide per capita emission factor. Assuming that
425 metric tons of ethylene oxide are emitted nationally, and that there
8 3
is a national population of 2.265 x 10 people , it is estimated that
ethylene oxide is emitted from hospitals at an annual per capita rate of
1.9 kg/1000 persons (4.2 lb/1000 persons).
Research Laboratories. As noted, research laboratories used 275 to
2
444 metric tons of ethylene oxide for sterilization in 1976. It may
be difficult to determine the number'of individual laboratories in a
given county or city because they generally constitute a smaller
operation in a large company or institution. For example, a
pharmaceutical manufacturer may have a research laboratory associated
with its production facilities, and a teaching hospital can have
extensive research laboratory facilities.
6/88 ". HOSPITAL AND LABORATORY STERILIZERS 10-3
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10.3 Methodology Options
Hospital Emissions. To estimate area source emissions of ethylene
oxide resulting from hospital sterilization, the following steps are
recommended:
(1) Determine the number of hospitals in each county, and the
number of beds in each hospital. This information can be
located in the American Hospital Association Guide to the
Health Care FieTd"?*
(2)(a) Estimate the annual quantity of ethylene oxide emitted by
multiplying the emission factors times the number of beds in
each hospital, or
(b) Survey the individual hospitals in the receptor area to
determine the amount of ethylene oxide that was purchased and
used. Conservatively, it can be assumed that all EO used is
emitted to the atmosphere. Emissions from hospitals could be
treated as an area source and summed. Emissions from large
hospitals can be treated as point sources for modeling
purposes, if so desired.
Laboratory Emissions. Laboratories tend to be located in urban areas
of high population density; a reasonable method of estimating area source
emissions from these facilities is to use a per capita emissions factor.
Assuming a median value of 360 Mg of EO is consumed and emitted
annually by research laboratories, and a national population of 2.265 x
10 thousand persons, an annual emission factor can be calculated to be
1.6 kg/1000 persons/yr (3.5 lb/1000 persons).2'4
County and city population data can be obtained from the U.S. Bureau
of Census. The population of a particular county or city can then be
multiplied by the per capita emission factor to estimate a countywide
emission of ethylene oxide from laboratories.
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10.4 Example Calculations
Example Calculation 1
EO emissions from hospitals are calculated as follows.
The study area has five hospitals. One is a large facility with 530
beds and a 75 percent annual occupancy. Another is a medium-sized
facility of 450 beds and a 70 percent occupancy. The remaining three
hospitals are small facilities having 125, 150, and 165 beds, with
percent occupancies of 73, 78, and 82 percent, respectively.
Ethylene oxide emissions can be estimated for the large hospital as
follows:
530 beds x 1.8 Ib EO/bed/yr = 954 Ib EO/yr.
Ethylene oxide emissions can be estimated for the medium hospital as
follows:
450 beds x 1.3 Ib EO/bed/yr = 585 Ib EO/yr.
EO Emissions from the small hospitals can be estimated as follows:
125 x 1.7 Ib EO/bed/yr = 213 Ib/yr
150 x 1.7 Ib EO/bed/yr = 255 Ib/yr
165 x 1.7 Ib EO/bed/yr = 281 Ib/vr
Total = 749 Ib/yr
The total EO emission can be determined by adding the quantity emitted by
the large hospital, the quantity emitted by the medium hospital, and the
total annual quantity of EO emitted by small hospitals, 954 + 585 + 749
or 2,288 Ibs EO/yr.
6/88 I HOSPITAL AND LABORATORY STERILIZERS 10-5
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Example Calculation 2
EO emissions from laboratories are calculated as demonstrated.
If a county has a population of 219,368 persons, the area source
emission of EO from laboratories can be estimated as follows:
EO Emissions = 219 (1,000 persons) x 1.6 kg EO/1000 persons/yr
= 350 kg EO/yr.
10.5 Methods to Apportion Countvwide Emissions
As described in Section 1.0 and Appendix A when performing air
dispersion modeling, it is generally recommended that countywide
emissions be distributed within the study area into rectangular area
source grid cells reflecting spatial variations in activity and
emissions. Similarly temporal in activities can be factored into the
modeling to reflect seasonal or diurnal fluctuations in emissions.
Modeling results would then reflect on-going activities in that portion
of the county, e.g., residential heating in the winter, commercial
solvent usage during working hours on weekdays.
There are three alternative approaches that can be used in spatially
distributing emission: (1) population, i.e., the magnitude of emissions
within a grid are directly proportional to the population living in the
grid, (2) land area, i.e., emissions from a countywide area source are
assumed to be uniform throughout the county and are distributed based on
the size of the area source grid,and (3) land use patterns that assume
that certain area source activities, most likely occur in certain areas
of the county, e.g., commercial, residential, or industrial.
In apportioning emissions from sterilizers, any of these methods may
be appropriate. Land area and population data can be readily obtained,
and applied as described in Appendix A. Land use data, available from
the U.S. Geological survey and other sources can be used in combination
with the spatial resolution for hospitals and laboratories to distribute
emissions based on the type of activity being performed, as shown in
6/88 : HOSPITAL AND LABORATORY STERILIZERS 10-6
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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Table 10-1; hospitals can, in fact, often be identified on topographical
or street maps and may be treated as point sources in the inventory..
Estimated seasonal, daily, and hourly temporal resolution for both
categories of sterilizers are also included in Table 10-1, and can be
used with the annual countywide emissions data to estimate temporal
variations.
6/88 -. HOSPITAL AND LABORATORY STERILIZERS 10-7
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Table 10-1 Spatial and Temporal Resolution of Countywide
Emissions Totals for Hospital and Laboratory Sterilizers
Hospital Sterilizers
Spatial Resolution
Surrogate indicator:
Information source(s):
Temporal Resolution
Seasona1:
Daily:
Hourly:
Laboratory Sterilizers
identify hospitals on maps or
commercial areas (code 12)
land use map and U.S.6.S. topographical
maps, street maps
uniform through the year
uniform through the week
uniform through the day
Spatial Resolution
Surrogate indicator:
Information source(s):
commercial (code 12) and industrial and
commercial complexes (code 15)
land use maps
Temporal Resolution
Seasonal:
Daily:
Hourly:
uniform through the year
90% Monday through Friday; 10% Saturday
uniform from 0800 to 2400; otherwise
zero
6/88
HOSPITAL AND LABORATORY STERILIZERS
10-8
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REFERENCES
1. Memorandum: Baseline Freon 12 Emission Estimates from Hospital
Sterilization Processes. MRI Project No. 8662-k. From Bruce
Nicholson to Neil Patel. U.S. Environmental Protection Agency.
Office of Air and Radiation. Washington, DC. 1986.
2. Radian Corporation. Locating and Estimating Air Emissions from
Sources of Ethvlene Oxide. EPA-450/4-84-0071. U.S. Environmental
Protection Agency, Office of Air QuaTity Planning and Standards.
Research Triangle Park, NC. 1984.
3. U.S. Department of Commerce. Census of Population 1980 Number of
Inhabitants. Part 1. United States Summary. Bureau of the Census.
Washington, DC. 1983.
4. American Hospital Association. American Hospital Association: Guide
to the Health Care Field; Chicago, IL.
6/88 . HOSPITAL AND LABORATORY STERILIZERS 10-9
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APPENDIX A
A. METHODS TO APPORTION COUNTYWIDE AREA SOURCE EMISSIONS
In order to perform air dispersion modeling, it is generally
recommended that countywide area source emissions are distributed within
the study area into rectangular area source grid cells and that spatial
and temporal variations of area source emissions are defined within the
grid. By spatially and temporally apportioning countywide area source
emissions, modeling results will reflect on-going activities in that
portion of the county, e.g., residential heating in the winter, or
commercial solvent use on weekdays.
Note that methods used in selecting the area source grid boundaries
are not addressed in -this Appendix; it would suffice to say that the
boundaries are somewhat subjective, and are established based on the
level of detail in the inventory, the boundaries of the study area, the
requirements of the air dispersion model and the resulting data analysis.
Two methods are commonly used to spatially distribute countywide
emissions to area source grids. In some cases, the area source emissions
can be determined directly from the area source activity within the grid
cell. The most frequently used method, however, is to apportion the
countywide emissions to the grid cell level by assuming that the
distribution of the area sources behaves similarly to that of a surrogate
indicator. Often these spatial apportionment factors are generic in
nature, i.e., they are based on "typical" national data. Obviously,
site-specific data are preferred, when available.
Temporal apportionment, on the other hand, is usually based on
typical seasonal, weekly, and daily operating schedules.
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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A.I Direct Determination of Emissions within an Area Source Grid
This method is often used when data are available on the location of
individual minor facilities that comprise an area source category. For
example, a local gas company may have information on the quantity of
natural gas consumed in every household or commercial facility, or a
survey can identify the locations of commercial or industrial facilities
such as dry cleaners or service stations. These data can be compiled by
surveying facilities within an industrial category, using the telephone
Yellow Pages, Dunn and Bradstreet's Electronic Yellow Pages . zip code
2
locations, the Thomas Registry , or other sources. Emissions can then
be calculated at the grid cell level, resulting in emission estimates
that better reflect variations within the county.
A.2 Spatial Apportionment
The selection of apportionment factors for a given area source
category depends on the spatial distribution of the emissions and on what
other information is available. In most cases, data are not readily
available to directly estimate area source emissions at the grid level.
As a result, default or "surrogate" indicators can be identified that
reflect activity and emission rates at the grid cell level. These
surrogate indicators can then be used to apportion grid all emissions to
the basic countywide Inventory. Variables often used as surrogate
indicators of area source activity include land area, land use
parameters, employment in various industrial and commercial sectors and
population. Appropriate surrogate indicators for each area source
category (Sections 2.10) are presented in the appropriate section of the
manual.
6/88 METHODS TO APPORTION COUNTYWIDE AREA SOURCE EMISSIONS A-2
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Spatial Apportionment Based on Land Area
Land area (e.g., square mileage, acres) can be used as a surrogate
indicator for those area source categories where the activity level is
typically uniform across the study region. The step-by-step procedure,
described below, is based on the assumption that source emissions are
directly proportional to land area.
1. Estimate the area of the study region.
If the study region is a unique geographic entity (i.e., city or
county) this information is often available from a local or state
government agency. If the study region is not so easily defined,
however, the areas must be estimated manually. A planimeter is a
tool frequently used to accomplish this task.
2. Overlay the chosen grid system onto the study region and estimate
the area of each grid cell.
A planimeter is again useful for this procedure. If the area grid
cell extends beyond the study region, only the cell area that is
within the study region should be considered in the apportionment
process.
3. Apportion the area source emissions within the grid cell according
to land area.
Because area source emission estimates are typically available on
a county level, it is best to proceed with the .allocation process
on a county-by-county basis. The area source emissions within
each grid cell are apportioned according to the percentage of the
respective total county land area the grid cell occupies. (For
example, if .05 percent of the land area of County A resides in a
grid cell, then .05 percent of the area source emissions of County
A are apportioned to the grid cell.) This relationship can be
expressed mathematically as follows:
Area Within Grid = Country Area
Grid Cell Area Source Emissions Total County Area Source
Emissions.
This methodology is illustrated in Example Calculation #1, Section 3.5.1.
6/88 METHODS TO APPORTION COUNTYWIDE AREA SOURCE EMISSIONS A-3
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The major advantage of this methodology is its simplicity. It is
relatively easy to obtain all the information necessary to accomplish
this method of apportionment. It should be noted, however, that the
method assumes that emissions are uniform across the country or study
region; in reality, even for source categories that are relatively
uniform across a region there tends to be clustering a't distinct
geographical locations (i.e., gasoline stations are often found at
intersections).
Spatial Apportionment Based on Population Density
The spatial distribution of many area source emissions such as those
from residential heating is proportional to population density within the
study region. As a consequence, countywide area source emissions are
frequently assigned to the grid cell level by using population density as
a surrogate indicator. This methodology is described in the following
steps:
1. Obtain population density information and a census tract
identification map for the study region.
Population data statistics are assembled according to census
tracts. The data and the census tract identification maps for the
study region can be obtained from the U.S. Department of Commerce,
Bureau of the Census or any current census almanac publication.
2. Overlay the chosen grid onto the census tract map and estimate the
area of the census tracts and each grid cell.
A planimeter is frequently used to estimate these areas. At this
point, it is important to closely identify those grid cells or
portions thereof that lie within each county comprising the study
area.
6/88 METHODS TO APPORTION COUNTYWIDE AREA SOURCE EMISSIONS A-4
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3. Apportion population within a grid cell according to the
percentage of 4he area of the respective census tract that the
grid cell occupies. (For example, if the area of the grid cell
occupies 50 percent of the area of a census tract, then it is
assumed that 50 percent of the population of that census tract
lies within the grid cell.)
Special attention is required when determining the population of
those grid cells which overlap two or more population census
tract. In those cases, the area of the grid cell that lies within
each census tract and the corresponding population within that
area must be computed separately. These population estimates must
then be summed to estimate the total population of the grid cell.
4. Apportion the area source emissions for the study area by grid
cell population density.
Because area source emission estimates are typically available on
a county level, it is best to proceed with the allocation process
on a county-by-county basis. The area source emissions within
each grid cell are apportioned according to the percentage of the
respective county population'residing in the grid cell. (For
example, if .05 percent of the population of County A resides in a
grid cell, then .05 percent of the area source emissions of County
A is apportioned to the grid cell.) This relationship can be
expressed mathematically as follows:
Population Within Grid = County Population
Grid Cell Area Source Emission Total County Area Source Emission.
This methodology is illustrated in Example Calculation #2, Section 3.5.2.
The obvious advantage of this approach lies in the simplicity of the
methodology and the availability of the information needed to perform the
procedure. This method is quite useful for those source categories such
as residential heating that can be spatially related to population
density. The primary weakness of this approach is the assumption that
emissions are proportional to population. While this is true for many
source categories, some categories such as degreasing or industrial
heating, are not necessarily concentrated in the more densely populated
6/88 METHODS TO APPORTION COUNTYWIDE AREA SOURCE EMISSIONS A-5
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
areas. Other categories such as forest fires may, in fact, be inversely
proportional to population density. A second major disadvantage lies in
the assumption that population density is uniform throughout the census
tract.
Spatial Apportionment Based on Land Use Patterns
Land use patterns can serve as a useful surrogate indicator of the
spatial distribution of area source emissions because they provide a more
accurate picture of the "real world" situation. Frequently, pollution
sources are located in low population areas such as industrial parks.
Local ordinances may dictate the location of certain types of industries
or businesses. This clustering of area sources results in concentrations
of certain types of sources in specific sections of a study area. For
example, small dry cleaners, a source of perchloroethylene, are typically
found in commercial areas, whereas domestic heating emissions are common
to suburban and urban residential areas.
A prerequisite for using this approach is the availability of land
use data. The U.S. Geological Survey (USGS) maintains a comprehensive,
computerized data base of information on land use distributions
throughout the country. One of the basic sources of land use compilation
data for the USGS is the NASA high latitude U-2/RB-57 aerial
photocoverage, usually at macroscales. This land use and land cover
data compilation is based upon the classification system of land use and
cover shown in Table A-l.
State and local governments frequently compile land use maps for
urban areas that are, in some instances, more current, more detailed, and
less costly than the USGS survey land maps.
6/88 METHODS TO APPORTION COUNTYWIDE AREA SOURCE EMISSIONS A-6
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Historically, land use data have been presented on topographical
maps; however, much of these data have, in recent years, been
computerized. USGS now compiles digital data, for many regions in the
country, in terms of 200 meters x 200 meters (4 hectare) grid cells.
For ease of transfer and readability, USGS data files also are
available in a character-coded format. These data files contain records
of each individual grid cell and provide the following information:
• UTM zone number;
• UTM Easting value in meters;
• UTM Northing value in waters;
• Land use and land cover attribute code (see Table A.2-1);
• Political unit code;
• USGS hydro!ogic unit code;
• Census county subdivision or SMSA tract code;
• Federal land ownership agency code; and
• State land ownership code.
The standard character-coded grid cell data files will have only grid
cell records for which at least one of the categories is coded.
Apportionment of areawide emissions according to land use patterns
requires the manipulation of enormous amounts of data. There are
frequently 500,000 to 1,000,000 four-hectare grid cells in a study area.
Data manipulation of such magnitude can be achieved only by using a
computer.
Land use data are compiled at four Levels (I through IV) with
increasing levels of detail. For environmental analyses, however, Levels
I and II provide sufficient detail for categorizing pollution source
distribution. A more complete description of USGS land use categories
can be found in Reference 3.
6/88 METHODS TO APPORTION COUNTYWIDE AREA SOURCE EMISSIONS A-7
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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Table A-l Land Use Categories
1. URBAN OR BUILT-UP LAND
11 Residential
12 Commercial and Service
13 Industrial
14 Transportation, communtcat ions
and services
15 Industrial and
commercial complexes
16 Mixed urban or
built-up land
17 Other urban or built-up
land
I. AGRICULTURAL LAND
21 Cropland and pasture
22 Orchards, groves, vineyards,
nurseries, and ornamental
horticultural groves
23 Confined feeding operation
24 Other agricultural land
3. RANGELAND
31 Herbaceous range land
32 Shrub and brush range land
33 Mixed range land
4. FOREST LAND
41 Deciduous forest land
42 Evergreen forest land
43 Mixed forest land
5. WATER
51 Streams and canals
52 Lakes evergreen
53 Reservoirs
54 Bays and estuaries
6. WETLAND
61 Forested wetland
62 Nonforested wetland
BARREN LAND
71 Dry salt flats
72 Beaches
73 Sandy areas, other
75 Strip mines, quarries,
and gravel pits
76 Transitional areas
77 Mixed barren land
TUNDRA
81 Shrub and brush tundra
82 Herbaceous tundra
83 Bare ground
84 Wet tundra
85 Mixed tundra
PERENNIAL SNOW OR ICE
91 Perennial snow fields
92 Glaciers
Source: Reference 3
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METHODS TO APPORTION COUNTYWIDE AREA SOURCE EMISSIONS
A-8
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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The basic steps to the apportionment procedure are as follows:
1. Compute or obtain county-specific area source emissions. This
information can usually be obtained from local and state
government agencies.
2. Identify the total number of land use grid cells in the county by
land use category.
3. Identify the area grids lie within the county.
4. Compile a grid cell/area source grid matrix.
Land use fractions for each area grid are computed for the various
land use categories. This information is then combined with the
data assembled in steps 1 through 3 above and compiled into a
matrix format. An example of this type of matrix is shown in
Table A-2.
5. Allocate area source emission fractions into land use categories.
This step requires the compilation of a land use/area source
matrix. Table A-3 is an example of this type of matrix. The
creation of this matrix should be based upon source distributions
found in the literature in combination with engineering judgment,
as needed. Emissions from residential heating, for example, can
be totally assigned to the residential land use category. Dry
cleaning emissions, 90 percent of which come from coin-operated
and commercial dry cleaners,4 can be distributed proportionately
to the commercial and services land use category. Surface coating
emissions can be distributed between five urban categories, all of
which paint and coat surfaces. A sixth urban category, "mixed
urban," is typically redistributed equally among Categories 11,
12, 12, 14, 15, and 17. Site-specific characteristics, if
available, should be used in the development of this matrix.
6. At the area source grid level in a county, for each area source
category and each pollutant, multiply the county area source
emission by the land use fraction of Step 4 and the emission
fraction of Step 5 to obtain land use emissions.
The two matrices, when multiplied, are transformed into a product
matrix that defines the fraction of the area source emissions is
assigned to each area source grid. This fraction is then
multiplied by each pollutant total in the countywide emission
inventory to determine the apportionment of each pollutant to each
area grid cell.
6/88 METHODS TO APPORTION COUNTYWIDE AREA SOURCE EMISSIONS A-9
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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Table A-2 Example of Grid Cell/Area Source Grid Matrix
Land Use Category
Resident lal
Com. & Services
Industrial
Trans., Com.. & Services
Ind. & Com Complex
Mixed Urban
Other Urban
Streams & Canals
Lakes
Reservoirs
Bays & Estuaries
All Other
Area 02
3774
53.6
797
63.8
276
59.2
261
61.1
166
57.6
133
75.1
357
32.5
100
68.5
0
0.0
48
76.2
0
0.0
15510
88.1
Area 06
820
11.7
82
6.6
119
25.5
60
14.1
• 0
0.0
5
2.8
243
22.2
46
31.5
0
0.0
9
14.3
0
0.0
993
5.6
Area 07
1034
14.7
159
12.7
44
9 4
79
18.5
80
27.8
16
9.0
184
16.8
0
0.0
0 •
0.0
5
7.9
0
0.0
777
4.4
Area 11 County total
1409 7037
20.0
212 1250
17.0
27 466
5.8
27 427
6.3
42 288
14.6
23 177
13.. 0
313 1097
28.5
0 146
0.0
0 1
0.0
1 63
1.6
0 1
0.0
326 17606
1.9
6/88
METHODS TO APPORTION COUNTYWLOE AREA SOURCE EMISSIONS
A-10
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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METHODS TO APPORTION COUNTYWIDE AREA SOURCE EMISSIONS
A-ll
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
An example calculation using this procedure is presented as Example
Calculation 3, Section A. 5.
An alternative approach is based on extracting data directly from..
land use maps. In this approach, the surrogate indicator is the area in
the study region devoted to each land use zone. Key assumptions in this
methodology are that (1) area source activity is uniformly distributed
throughout land use zones, and (2) the area of the grid cell devoted to a
particular land use code is a true indication of the magnitude of the
area source emissions within that grid cell. The basic steps in this
alternative procedure are summarized below.
1. Identify the total countywide emissions of the area source
categories under study. These estimates can usually be obtained
from local and state governmental offices or can be estimated from
available area source activity data.
2. Identify the land use code in which the activity of a particular
area source category would be likely to occur. An example of this
association is to assume that dry cleaning activities would be
most likely to occur in a commercial land use zone.
3. Superimpose the grid system network on the land use map and
estimate the area of each grid cell devoted to each land use code.
4. Estimate the emissions from each grid cell as a simple fraction of
the total as follows:
E1 = Et (Si/St)
where
E = area source emissions;
S = surrogate indicator;
i = the value in grid cell; and
t = the total for the county or region
is' known as the "apportioning factor."
The units for the surrogate indicator(s) can be arbitrary (i.e.,
percent of grid cell, square kilometer, square mile).
6/88 METHODS TO APPORTION COUNTYWIDE AREA SOURCE EMISSIONS A-12
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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An example of this apportionment method is shown in Example 4,
Section A.5.
The discussion above is applicable for apportioning area source
emissions based on a single land use surrogate indicator. In some cases,
more than one indicator may be used for an area source emission
apportionment. For example, miscellaneous solvent use can be associated
with the two consumer (residential and commercial) land use categories
(land use codes 11 and 12).
There are two principal ways to manage this type of apportionment.
The first approach is to estimate solvent emission subtotals for the two
types of land use involved; then each of these subtotals is apportioned
according to the corresponding land use areas. This action creates two
new emission subcategories where the countywide inventory may have had
only one. For example, one-half of the miscellaneous solvent emissions
could be assigned to multifamily residences (land use 11) and one-half to
commercial and service use (land use 12). Hence, if countywide emissions
from miscellaneous solvent use are 12 tons per day, 6 tons per day would
be apportioned at the grid cell level for each of these
subcategories,based on the distribution of the corresponding surrogate
indicator. Alternatively, the relative intensity of solvent use in the
two types of areas could be estimated. For example, it can be assumed
that residential areas have one-third the emission rate per unit area of
commercial and service areas. In this case, the apportioning factors
would be calculated using an appropriate weighting factor for the two
types of land use. This would be expressed, mathematically, by the
equation:
6/88 METHODS TO APPORTION COUNTYWIDE AREA SOURCE EMISSIONS A-13
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fik =
j =
2
2 Wjksij
1
n
2
i = 1
2
2
j =
Wjksij
1
where
f^ - apportioning factor
W-K = the weighting factor selected for land -use type j in
relation to source category k.
S,, = the value of the surrogate indicator (i.e., the area) of
' J
land use type j in cell.
The summation term appearing in the numerator is essentially a
composite surrogate indicator for the entire category. Consequently, if
solvent emissions are weighted according to the previous suggestion (W-,
= 1, W« = 3) and the respective areas in a given grid cell are 0.6 and
0.4, then the value of the composite surrogate indicator for that cell is
(0.6 x 1) + (0.4 x 3), or 1.8- The countywide emission for the category.
is then apportioned based on this composite surrogate indicator.
The above methodology can also be implemented using traffic
zone-level demographic statistics.
State and local transportation planning agencies often compile data
on employment and other demographic statistics for urban areas. These
data, which are frequently aggregated at the zonal level, can be used in
lieu of land use maps to define surrogate indicators for area source
apportionment. These zonal statistics are usually much more detailed in
data characterization than are land use data. For instance, zonal
6/88 METHODS TO APPORTION COUNTYWIDE AREA SOURCE EMISSIONS A-14
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PROCEDURES FOR ESTIMATING AND ALLOCATING
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statistics in a particular urban area may typically be compiled for five
or more commercial and industrial subcategories, whereas the
corresponding land use maps may only identify generalized commercial and
industrial land uses.
Reference 5 discusses this approach in greater detail.
A.3 Mobile Source Apportionment
Several methods are currently available to apportion emissions from
mobile sources. Each methodology is discussed below.
Apportionment Based on Vehicle Miles Traveled
Vehicle Miles Traveled (VMT) data can .be effectively used as a
surrogate indicator to allocate mobile VOC emissions to the grid cell
level for modeling purposes. State and local traffic agencies usually
compile VMT data disaggregated into traffic zones. In most cases, these
data are readily available for most metropolitan areas. The basic steps
in the allocation procedure are illustrated below: an example of this
procedure is presented as Example Calculation #5; Section 3.5.5.
1. Obtain countywide or study area VMT and mobile VOC emissions data
from state or local agencies. These data are typically compiled
according to vehicle type and pollutant species. VOC emissions
are also frequently categorized as either evaporative or exhaust
and are emanating from either gasoline or diesel fuels.
2. Obtain traffic zone VMT data from local or state agencies and
determine the total VMT for each grid cell. This is accomplished
by summing the VMT data for all the traffic zones lying within
each grid cell. If only a portion of a traffic zone lies within
the grid cell, apportion VMT's within the cell in proportion to
the area of the traffic zone lying within the grid cell (i.e., if
10 percent of the traffic zone lies within the cell apportion
10 percent of the traffic zone's total VMT to the grid cell). A
planimeter can be used to estimate the area of the traffic zones.
In some cases, area estimation can be done by sight.
6/88 METHODS TO APPORTION COUNTYWIDE AREA SOURCE EMISSIONS A-15
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
3. Determine the apportionment factor for each grid cell. The
apportionment (A-j) is defined by the following equation
A1 = VMTi/VMTt
where VMT-j is the VMT within the grid cell and VMTt is the
total VMT for the study area.
4. Apportion VOC emissions to each grid cell by multiplying the
apportionment factor by the total county/study area mobile VOC
emissions. The apportionment factor is further multiplied by each
pollutant-specific subtotal of the county/study area mobile VOC
emissions data to create a speciated VOC data base for each grid
cell.
Apportionment Based on MOBILES
As mentioned in Section 4, MOBILES is a computer program that
calculates emissions of hydrocarbon (HC), carbon monoxide (CO), and
oxides of nitrogen (NO ) from highway motor vehicles. MOBILES can be
adapted to apportion the estimated emissions into designated area grids
for modeling purposes. The best sources of data for input into the model
(i.e., VMT distribution, driving patterns) are local and state
transportation planning commissions and other related organizations.
Emissions can then be each estimated for grid within a county. For
further information on MOBILES, the reader is directed to User's Guide to
MOBILES (Mobile Source Emissions Model).
The VMT approach to apportionment is an effective screening tool for
mobile emission estimates; however, driving patterns and vehicle speed
are not considered in estimating emissions, which is a major drawback.
MOBILE4 estimates mobile emissions in a much more sophisticated manner
taking into account both driving patterns and vehicle speed. Mobile
emissions are categorized as evaporative or exhaust, resulting in a more
real life representation of pollutant production. A second major
advantage of MOBILES is that mobile emissions are directly apportioned
into area source grids.
6/88 METHODS TO APPORTION COUNTYWIDE AREA SOURCE EMISSIONS A-16
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
The sophisticated nature of MOBILES demands that persons familiar
with the program must conduct the modeling exercise. In addition,
obtaining the extensive data needed as input into the model, if not
readily available from a local or state transportation commission, can be
time consuming and expensive. In contrast, the Vehicle Miles Traveled
approach, while less accurate, can be performed more easily by
individuals not familiar with the MOBILES model.
«
A.4 Temporal Distribution of Countywide Emission Estimates
The countywide emission values used in the apportionment process
above are typically available only as annual or perhaps seasonal
estimates. In order to more effectively use the data for modeling
purposes, it must be translated into hour-by-hour emission rates.
If only annual emission estimates are available, the first step in
this process is to estimate the seasonal component of activity for each
area source. For many sources, activity is fairly constant from season-
to season, whereas for some sources, a strong seasonal component will be
evident. _Degreaser operations is an example of the former category where
activity is fairly constant throughout the year. Conversely, emissions
from residential heating will occur primarily in the colder winter
months.
Once the seasonal component is known, the daily component should be
determined. Again, some area source activities are relatively constant
from day to day, thereby simplifying the estimation process. For
example, gasoline storage losses and natural gas leaks can be assumed to
be uniform over the week. On the other hand, many work-related area
sources are more active on weekdays. Examples include dry cleaning
6/88 METHODS TO APPORTION COUNTYWIDE AREA SOURCE EMISSIONS A-17
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
plants and degreasing operations where activities are concentrated from
Monday through Friday (or Saturday in some cases). The seasonal
activity for these sources should be distributed only to those days on
which the source is active. For instance, if dry cleaning emissions for
the county are 312 tons of solvent over a 92-day period from July to
September, and most plants typically operate 6 days a week (for a total
of 78 operating days), then daily emissions from dry cleaning would be 4
tons (312 + 78). This daily rate would not be applicable to a
Sunday.
After the daily activity level has been determined for each area
source, the final step is to estimate hourly emissions. This is
generally accomplished by applying a 24-hour operating pattern to the
daily activity level. The 24-hour operating pattern can be obtained from
onsite measurements, survey data, or engineering judgment. To
illustrate, dry cleaning establishments generally operate from 7 a.m. to
5 p.m., Monday through Saturday, with uniform emissions throughout the
period. Given a countywide daily emission rate of 4 tons, the hourly
emission would be .36 tons (4 -=• 11).
Temporal resolution methodologies for various area source categories
are presented in the manual in Sections 2 through 10.
A.5 Example Calculations
Example calculations of selected area source apportionment
methodologies are provided. The examples presented are somewhat
simplistic to better illustrate the fundamental steps of each methodology.
6/88 METHODS TO APPORTION COUNTRYWIDE AREA SOURCE EMISSIONS A-18
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Example Calculation 1
Estimate area source spatial apportionment using land area as a
surrogate indicator.
County A has an area of 1472 square miles. For purposes of air
dispersion modeling, the county has been divided into two area source
grids. Using a planimeter, the square mileage of the grid is estimated
to be as follows:
Area % of Area
Grid 1 962 square miles 65
Grid 2 510 square miles 35
Emissions of benzene from gasoline marketing are estimated to be 11
MT/yr and emissions of formaldehyde from heating area sources is
estimated to be 75 MT/yr.
The emissions are apportioned using the methodology described in
Section A.2.1, as follows.
Benzene
Grid 1 (11 MT/yr) x (.65) = 7 MT/yr
Grid 2 (11 MT/yr) x (.35) = 4 MT/yr
Formaldehyde
Grid 1 75 MT/yr x (.65) = 49 MT/yr
Grid 1 75 MT/yr x (.35) = 26 MT/yr
6/88 METHODS TO APPORTION COUNTYWIDE AREA SOURCE EMISSIONS A-19
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Example Calculation 2
Estimate area source spatial apportionment using population density
as a surrogate indicator.
County A, USA has a population of 354,000 people. For purposes of
modeling the county has been divided into three area source grids with
the following populations estimated based on census tract data.
Grid 1
Grid 2
Grid 3
Population
193,000
120,000
41,000
% of County Population
55
34
11
Total emissions from area sources of perchloroethylene from dry
cleaners is estimated to be 73 MT/yr and trichloroethylene emissions from
degreasers are 49 tons/yr.
The emissions are apportioned using the methodology described in
Section A.2.2 as follows.
Perchloroethylene
Grid 1
Grid 2
Grid 3
Trichloroethvlene
(73 MT/yr) x (.55) = 40 MT/yr
(73 MT/yr) x (.34) = 25 MT/y,r
(73 MT/yr) x (.11) - 8 MT/yr
Grid 1
Grid 2
Grid 3
(49 MT/yr) x (.55) = 27 MT/yr
(49 MT/yr) x (.34) = 17 MT/yr
(49 MT/yr) x (.11) - 5 MT/yr
6/88
METHODS TO APPORTION COUNTYWIDE AREA SOURCE EMISSIONS
A-20
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Example Calculation 3
Sample calculations are provided below for apportioning emissions
from dry cleaning operations in County A, USA, utilizing the surrogate
land use matrix methodology. It is estimated that 162 MT/yr of
perch!oroethylene are emitted from area source dry cleaners.
Step 1
Number of Grid Cells in
Land Use Category Land Use .Category
Residential 2,799
Commercial and Services 618
Industrial 78
Transportation, Communications,
and Services 348
Industrial and Commercial
Complexes 1
Mixed Urban* • 3
Other Urban 128
Streams and Canals 233
Lakes 61
Reservoirs 519
Bays and Estuaries 652
All Other 53,480
Step 2
Area Grid Cells 22 and 23 lie within this county.
* Mixed Urban grid cells in Area Source 22: 3
Area Source 23: 0
The reallocation of the above grid cells will not change the county
and area grid distributions.
6/88 METHODS TO APPORTION COUNTYWIDE AREA SOURCE EMISSIONS A-21
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Step 3
Land Use Category
Area Source 22
Grid Cells %
Area Source 23
Grid Cells %
Residential 2107 75.3
Commercial and
Services 363 58.7
Industrial 75 96.2
Transportation,
Communication,
and Services 136 39.1
Industrial and
Commercial Complexes
Other Urban
Streams and Canals
Lakes
Reservoirs
Bays and Estuaries
All Other
Step 4
For dry cleaning, emission fractions
692
255
3
212
24.7
41.3
3.8
60.9
County Total
Grid Cells %
2799
618
78
348
100
100
100
100
1
97
9
- 24
285
29
34584
100
75.8
3.9
39.3
54.9
4.4
64.7
0
31
224
37
234
623
18896
0
24.2
96.1
60.7
45.1
95.6
35.3
1
128
233
61
519
652
53480
100
100
100
100
100
100
100
from various land use categories
are:
Commercial and Services: 90%
Industrial: 5%
Industrial and Commercial
Complexes: 5%
6/88
METHODS TO APPORTION COUNTYWIDE AREA SOURCE EMISSIONS
A-22
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Step 5
Area Source Grid 22 Perchloroethvlene
Commercial and Services = 162 MT/yr x 58.7 x 90
100 100
=85.6 MT/yr.
Industrial = 162 MT/yr x 96.2 x 5
100 100
=7.8 MT/yr
Industrial and Commercial
Complexes = 162 M.T./yr x 100 x 5_
100 100
= 8.1 M.T./yr.
Therefore, total perchloroethylene emissions from Area Source Grid 22
= 85.6 + 7.8 + 8.1 = 101.5 MT/yr
Similarly, in Area Source Grid 23,
Perchloroethylene emissions = 60.5 MT/yr.
Example Calculation 4
Example calculations are provided below for apportioning emissions
from dry cleaning operations in County B, USA, utilizing an alternative
surrogate land use methodology. It is estimated that 100 MT/yr of
perchloroethylene are emitted by area source dry cleaners. Refer to
Figure A-l.
Step 1 Surrogate Land Use Codes
12: Commercial
15: Industrial and Commercial Combined
6/88 METHODS TO APPORTION COUNTYWIDE AREA SOURCE EMISSIONS A-23
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS'OF AIR TOXICS
26
1 2
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
SOURCE: Reference 5
Figure A-l LAND USE MAP
6/88
METHODS TO APPORTION COUNTYWIDE AREA SOURCE EMISSIONS
A-24
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Steps 2 and 3
For Grid Cell (15, 15)
S, = .20 grid cells (20 percent of the area
is indicated as commercial/industrial)
St = 26.3 grid cells
(Si/St) for grid cell (15, 15) = .0076
Ei = (100) (.0076) = .76 MT/yr
Example Calculation 5
A county is divided into two grid cells for air dispersion modeling.
The following example apportions mobile emissions data resulting from
gasoline consumption from light duty vehicles (cars and light trucks) in
Grid Cells 931 and 932.
Total county emissions by pollutant (MT/yr), using the methodology
provided in Section 4 are as follows:
Acetaldelyde
Asbesto|
Benzene
Benzo(a)pyrene
1.3-butadiene
0.2
0.001
68.8
0.002
11.7
The benzene evaporative emissions factor on Table 4-1 is given as a
range to calculate the total county emissions, we assumed the benzene
evaporative factor was the mid-point of the range.
6/88 METHODS TO APPORTION COUNTWIDE AREA SOURCE EMISSIONS A-25
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Cadmuin = 0.003
Chromium = 298.9
Ethylene dichloride = 0.45
Formaldehyde = 16.3
Lead = 0.6
Polycyclic organic Matter = 1.9
Traffic zone data provided is as follows:
TRAFFIC ZONES VMT/DAY
1
2
3
4
5
' 6*
7
75,827
513,601
386,399
150,132
56,013
80,537
241,611
Step 1
Grid Cell 931 consists of traffic zones 1, 2, and 3.
Grid Cell 932 consists of traffic zones 4, 5, and 6, as well as
one-third of traffic zone 7.
Allocate VMT Data to Grid Cells 931 and 932.
Grid Cell 931:
75,827 + 51,3601 + 386,399 = 975,827
(Zone 1) (Zone 2) (Zone 3)
Grid Cell 932:
150,132 + 56,013 + 80,537 + (1/3 x 241,611) = 367,219
(Zone 4) (Zone 5) (Zone 6) (1/3 Zone 7)
Step 2
Apportionment Factor (^ = VMTi/VMTt)
Grid Cell 931; A = 975,827/(975,827 + 1,342,506) = .70
Grid Cell 932; A = 367,219/(975,827 + 1,342,506) = .30
One-third of the area of zone 7 lies within Grid Cell 932.
6/88 METHODS TO APPORTION COUNTYWIDE AREA SOURCE EMISSIONS A-26
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
Step 3
To apportion emissions to Grid Cells 931 and 932, multiply results of
Step 2 times countywide emissions
Light duty vehicle
Grid Cell 931
Acetaldehyde •
Asbestos
Benzene
Benzo(a)pyrene
1,3-Butadiene
Cadmium
Chromium
Ethylene dibromide
Formaldehyde
Lead
Polycyclic organic Matter
Grid Cell 932
Acetaldelyde
Asbestos
Benzene
Benzo(a)pyrene
1,3-Butadiene
Cadmium
Chromium
Ethylene dibromide
Formaldehyde
Lead
Polychclic organic matter
0.2
0.001
68.8
0.002
11.7
0.003
298.9
0.5
16.3
0.6
1.9
X
X
X
X
X
X
X
X
c
X
X
0.70
0.70
0.70
0.70
0.70
0.70
0.70
0.70
0.70
0.70
0.70
= 0.2
= 0.0007
= 48.2
= 0.002r
= 8.7
= 0.002
= 209.2
= 0.3
= 11.4
= 0.4
= 1.3
0
0
68
0
11
0
298
0
16
0
1
.2
.001
.8
.002
.7
.003
.9
.5
.3
.6
.9
X
X
X
X
X
X
X
X
X
X
X
0
0
0
0
0
0
0
0
0
0
0
.30
.30
.30
.30
.30
.30
.30
.30
.30
.30
.30
=
s
s
Si
=
=
=
=
s
sr
s
0
0
20
0
3
0
89
0
4
0
0
.07
.0003
.6
.0007
.5
.0001
.7
.1
.9
.2
.6
6/88
METHODS TO APPORTION COUNTYWIDE AREA SOURCE EMISSIONS
A-27
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PROCEDURES FOR ESTIMATING AND ALLOCATING
AREA SOURCE EMISSIONS OF AIR TOXICS
REFERENCES
1. Dunn and Bradstreet. Dunn's Electronic Yellow Pages (EPS) - Dialog
Data Base Catalog. Dialog Information Services Inc. January 1987.
2. Thomas Publishing Company. Thomas Register of American Manufacturers
and Thomas Register Catalog File. Volumes 1-14. New York, NY. 1986.
3. Fegeas, R.C. et al. USGS Digital Car to Graphic Data Standards:
Land Use and Land Cover Digital Data. GSC 895-E. U.S. Department of
the Interior. Washington, DC. 1983.
4. U.S. Environmental Protection Agency. Perchloroethvlene
Drvcleaning-Background Information for Proposed Standards.
EPA-450/3-79-029a. Office of Air Quality Planning and Standards.
Research Triangle Park, NC. August 1979.
5. Environmental Protection Agency. Procedures for the Preparation of
Emission Inventories for Volatile Organic Compounds Volume II:
Emission Inventory Requirements for Photochemical Air Quality
' Simulation Models. EPA-450/4-79-018. U.S. Office of Air Quality
Planning and Standards. Research Triangle Park, NC. September 1979.
6. U.S. Environmental Protection Agency. Computation of Air Pollutant
Emissions Factors. Volume II: Mobile Sources AP-42. Mobile Vehicle
Emissions Laboratory, Ann Arbor, MI - September, 1985.
7. U.S. Environmental Protection Agency. User's Guide to Mobi1e3. U.S.
Environmental Protection Agency. Ann Arbor, MI.
6/88 METHODS TO APPORTION COUNTYWIDE AREA SOURCE EMISSIONS • A-28
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