Emission inventories are divided into several source categories. These divisions stem from both differing methods for preparing the inventories and from different characteristics and attributes of the categories (more on these terms later). Generally, emission inventories are divided into the following source categories:
Stationary area/Nonpoint sources: Sources that are treated as being spread over a spatial extent (usually a county or air district) and that are not moveable (as compared to nonroad mobile and on-road mobile sources). Because it is not possible to collect the emissions at each point of emission, they are estimated over larger regions. The EPA introduced the term “nonpoint” to replace “stationary area” in order to avoid confusion with the term “area source”, which is used as a regulatory term in the toxics realm. However, “nonpoint” has not gained acceptance (thus far) by the criteria inventory/modeling community. Thus, in this manual we will use the term “stationary area” to refer to these sources when they are in criteria inventories, while we use the term “nonpoint” to refer to these sources when they are in toxics inventories. Examples of nonpoint or stationary area sources are residential heating and architectural coatings. Numerous sources, such as dry cleaning facilities, may be treated either as stationary area/nonpoint sources or as point sources; in particular, the toxics inventory contains numerous small sources (based on emissions) that are not inventoried as nonpoint sources because their locations are known and are provided.
Nonroad mobile sources: Vehicular and otherwise movable sources that do not include vehicles that travel on roadways. These sources are also computed as being spread over a spatial extent (again, a county or air district). Examples of nonroad mobile sources include locomotives, lawn and garden equipment, construction vehicles, and boating emissions. These sources are included in both criteria and toxics inventories.
On-road mobile sources: Vehicular sources that travel on roadways. These sources can be computed either as being spread over a spatial extent or as being assigned to a line location (called a link). Data in on-road inventories can be either emissions or activity data. Activity data consists of vehicle miles traveled (VMT) and, optionally, vehicle speed. Activity data are used when SMOKE will be computing emission factors via another model such as MOBILE6. Examples of on-road mobile sources include light-duty gasoline vehicles and heavy-duty diesel vehicles. On-road mobile sources are included in both criteria and toxics inventories.
Point sources: These are sources that are identified by point locations, typically because they are regulated and their locations are available in regulatory reports. Point sources are often further subdivided into electric generating utilities (EGUs) and non-EGU sources, particularly in criteria inventories in which EGUs are a primary source of NOx and SO2. Examples of non-EGU point sources include chemical manufacturers and furniture refinishers. Point sources are included in both the criteria and toxics inventories.
Wildfire sources with precomputed plume rise: Traditionally, wildfire emissions have been treated as stationary area sources. More recently, data have also been developed for point locations, with day-specific emissions and hour-specific plume rise (vertical distribution of emissions) being computed prior to input to SMOKE. In this case, the wildfire emissions are processed by SMOKE as point sources.
Biogenic land use data: Biogenic land use data characterize the type of vegetation that exists in either county total or grid cell values. The biogenic land use data in North American is available using two different sets of land use categories: the Biogenic Emissions Landcover Database (BELD) version 2 (BELD2), and the BELD version 3 (BELD3).
Emission processing in SMOKE is divided into four processing categories: area, biogenic, mobile, and point. The definitions of these categories that SMOKE uses are different than those used for defining emission inventories. Table 2.1, “Inventory source categories and SMOKE processing capabilities and categories” lists the inventory source categories, the types of inventories (activity data, criteria, particulates, and toxics) that SMOKE can process, the temporal resolution that is acceptable to SMOKE, and the SMOKE processing category that should be used for processing the inventory.
Table 2.1. Inventory source categories and SMOKE processing capabilities and categories
| Inventory source category | Temporal resolution that SMOKE can process* | SMOKE processing category | |||
|---|---|---|---|---|---|
| Activity data | Criteria | Particulates | Toxics | ||
| Nonpoint or stationary area | N/A | A, S | A, S | A, S | Area |
| Nonroad mobile | N/A | A, S | A, S | A, S | Area |
| On-road mobile | A | A, S | A, S | A, S | Mobile |
| EGU | N/A | A, S, D, H | A, S, D, H | A, S | Point |
| Non-EGU | N/A | A, S, D, H | A, S, D, H | A, S | Point |
| Wildfire with precomputed plume rise | N/A | D, H | D, H | N/A | Point |
| Biogenic land use | N/A | X | N/A | N/A | Biogenic |
| * A = Supports annual data; S = Supports average-day data; D = Supports day-specific data; H = Supports hourly data; X = Supports available data | |||||
Each inventory source category has source characteristics, source attributes, data values, and data attributes. Source characteristics are unique to each inventory source category and also distinguish one source in the inventory from another. Source attributes further describe the sources with other information that is useful for emissions processing, such as point-source flue gas exit height and temperature. The data values are either emissions values or activity values. The data attributes are additional information about the data values, such as the percentage reduction in emission from controls already applied to the source. In the following subsections, we summarize the source characteristics and attributes and the data values and attributes that are used by SMOKE for each of the inventory categories.
Source characteristics: For all typical inventories, the source characteristics that identify these sources are country/state/county code and SCC. See Section 2.3.4, “Country, state, and county codes” and Section 2.3.5, “Source Classification Codes” for further information.
Optional source characteristics: SMOKE can also use pregridded data as a SMOKE area source; this is described in more detail in Section 2.8.2.2, “Pregridded data route”. In this case, the country/state/county code and SCC are not used in SMOKE.
Source attributes: The inventory year is associated with all sources in the inventory input files. In addition, SMOKE assigns a time zone (see Section 2.9.14, “Assign country codes, years, and time zones” and an approach for normalization of temporal profiles (see Section 2.9.13, “Set the weekday averaging approach”). In the nonpoint toxics inventory only, Standard Industrial Classification (SIC) codes, Maximum Achievable Control Technology (MACT) codes, and North American Industrial Classification System (NAICS) codes are optional source attributes; the NAICS code is read by SMOKE but not otherwise used at this time. Additionally, a “source type” field is available in the nonpoint inventory to identify major and Clean Air Act (CAA) section 112 area sources. See Section 2.3.6, “Standard Industrial Classification codes” for a description of SIC codes, Section 2.3.7, “Maximum Achievable Control Technology codes” for more about MACT codes, and Section 2.3.8, “Source types: major and section-112 area sources” for more about source types. We will refer to the CAA section 112 area sources as simply “section-112 area sources”.
Data: SMOKE can read emissions data for criteria, particulate, and toxics pollutants for nonpoint/stationary area and nonroad inventories. The SMOKE system is not constrained with regard to the pollutants read (although typical examples were given in Section 2.3.1, “Inventory data types”). SMOKE accepts annual emissions data, average-day emissions data, or both (though not all input formats support all types). An emission factor value can also be read by SMOKE, but SMOKE does nothing with it.
Data attributes: Inventories for nonpoint/stationary area and nonroad mobile sources can contain control efficiency, rule penetration, and rule effectiveness information for each pollutant. SMOKE will use these data if provided; otherwise it will set default values that indicate that no control-based adjustments have been applied to the inventory pollutant data. The defaults are listed in the file formats in Chapter 8, SMOKE Input Files.
Source characteristics: For on-road mobile inventories, the minimum source characteristics that identify these sources are country/state/county code and either SCC or road class and vehicle type codes. When the SCC is provided, it must follow a specific pattern in order to contain the road class and vehicle type codes (see Section 2.8.4.2, “Special approach for on-road mobile SCCs”). When road class and vehicle type codes are provided to SMOKE directly, SMOKE translates these to SCC values.
Optional source characteristics: A link code may also identify on-road sources. This code must be unique within each county and SCC (or road class/vehicle type combination).
Source attributes: The inventory year is associated with all sources in the inventory input files. In addition, SMOKE assigns a time zone (see Section 2.9.14, “Assign country codes, years, and time zones”) and an approach for normalization of temporal profiles (see Section 2.9.13, “Set the weekday averaging approach”). For sources with link codes, SMOKE will use the starting and ending coordinates of the link, using either latitude-longitude (lat-lon) values or coordinates in the Universal Transverse Mercator (UTM) coordinate system.
Data: Emissions data for criteria, particulate, and toxics pollutants can be read for on-road mobile inventories. SMOKE is not constrained with regard to the pollutants read (although typical examples were given in Section 2.3.1, “Inventory data types”). SMOKE accepts annual emissions data, average-day emissions data, or both (though not all input formats support all types).
Additionally, on-road mobile inventories can contain VMT and average speed activity data, which are needed when users would like SMOKE to run MOBILE6 to compute emissions. A combination of precomputed emissions and VMT data is also acceptable for input to SMOKE, but you are responsible for preventing duplication of emissions. Duplication could occur if you input precomputed emissions for the same sources for which you have SMOKE calculate emissions using VMT data and MOBILE6.
Data attributes: No data attributes are associated with on-road mobile sources.
Source characteristics: The source characteristics for point sources depend on the inventory input format. The Inventory Data Analyzer (IDA) format and SMOKE one-record-per-line (ORL) format identify sources by country/state/county code, plant code, point code, stack code, segment code, and SCC. The Emissions Modeling System, ‘95 (EMS-95) format identifies sources by country/state/county code, facility code (same as plant code), stack code, device code, process code, and SCC.
Optional source characteristics: SMOKE can support up to five location identifiers within a plant, although the most used in any currently implemented input file format is four.
Source attributes: As with other source categories, inventory year is associated with all sources in the inventory input files. SMOKE also assigns a time zone (see Section 2.9.14, “Assign country codes, years, and time zones”) and an approach for normalization of temporal profiles (see Section 2.9.13, “Set the weekday averaging approach”). In addition, point sources have the following required source attributes not associated with other source categories: latitude, longitude, stack height, stack diameter (at the exit location), flue gas exit velocity, and flue gas exit temperature. Finally, the following optional source attributes are also used by SMOKE: SIC codes, MACT codes, plant descriptions, emissions release type point (e.g., horizontal stack, fugitive), source type (major or section-112 area), Office of Regulatory Information Systems (ORIS) identification codes, and boiler identification codes. Not all input formats support all types of optional source attributes. In particular, the ORIS and boiler codes (which are necessary for SMOKE to use in matching with Continuous Emissions Monitoring [CEM] hour-specific EGU data) are supported only by the IDA format. Also, the MACT code and source types are supported only by the SMOKE ORL format. See Section 2.3.6, “Standard Industrial Classification codes”, Section 2.3.7, “Maximum Achievable Control Technology codes”, and Section 2.3.8, “Source types: major and section-112 area sources” for more information.
Data: Emissions data for criteria, particulate, and toxics pollutants can be read for point inventories. SMOKE is not constrained with regard to the pollutants read (although typical examples were given in Section 2.3.1, “Inventory data types”). SMOKE accepts annual emissions data, average-day emissions data, or both.
Optionally, point-source emissions data can be provided using day-specific or hour-specific records. The formats for these data are described in Section 8.2.6, “PTDAY: Point source day-specific emissions” and Section 8.2.7, “PTHOUR: Point source hour-specific emissions”.
Data attributes: EGU and non-EGU point sources can contain control efficiency and rule effectiveness information for each pollutant. SMOKE will use these data if provided; otherwise it will set default values that indicate that no control-based adjustments have been applied to the inventory pollutant data. The defaults are listed in the file formats in Chapter 8, SMOKE Input Files.
Source characteristics: Wildfires with precomputed plumes are identified by the country/state/county code and the fire name.
Optional source characteristics: There are no optional source characteristics for wildfire sources.
Source attributes: Like other source categories, inventory year is associated with all sources in the inventory input files. SMOKE also assigns a time zone (see Section 2.9.14, “Assign country codes, years, and time zones”) and an approach for normalization of temporal profiles (see Section 2.9.13, “Set the weekday averaging approach”). In addition, wildfire sources require the latitude and longitude source attributes. Finally, additional hour-specific source attributes for wildfire sources must be provided for the fraction of emissions in the surface layer, the height of the bottom of the plume, and the height of the top of the plume. These hour-specific attributes are provided to SMOKE using the point-source hour-specific formats described in Section 8.2.7, “PTHOUR: Point source hour-specific emissions”.
Data: Wildfire source inventories can contain criteria and particulate pollutants. SMOKE is not constrained with regard to the pollutants read (although typical examples were given in Section 2.3.1, “Inventory data types”). These data must be provided as day-specific or hour-specific emissions values using point-source formats specified in Section 8.2.6, “PTDAY: Point source day-specific emissions” and Section 8.2.7, “PTHOUR: Point source hour-specific emissions”.
Data attributes: No data attributes are associated with wildfire sources.
Source characteristics: Biogenic emission data does not fit as neatly into the source-characteristic paradigm as the previously described source types. Emissions for biogenic sources are estimated starting with land use data, which are available for both BELD2 and BELD3 processing. The BELD2 data are available either by U.S. state/county and BELD2 land use category or by grid cell and BELD2 land use category. BELD3 land use data are available by 1-km grid cell over North and Central America and by BELD3 land use category.
Optional source characteristics: Biogenic land use data do not include optional source characteristics. The data are either by state/county or by grid cell.
Source attributes: There are no source attributes for biogenic land use data.
Data: The biogenic land use data consist of fractions associated with each land use type within a county or grid cell.
Data attributes: There are no data attributes for biogenic land use data.