How to Use the Speciation Profile Data
This page last reviewed December 14, 2012
Each speciation profile provides weight fraction data of each chemical species making up either the total particulate matter (PM) or total organic gas (TOG), and is designated by an identification code number. The chemical species are identified by a 5-digit ARBCHEM (formerly known as ARB SAROAD) code, a 9-digit Chemical Abstract Service (CAS) number (where available), and the chemical name (chemname).
As can be seen in the diagram, below, speciating a TOG (or ORG) compound is simply a matter of multiplying the total TOG criteria pollutant emissions (available from the ARB's emission inventory web site) for the given SCC or EIC category times the fraction of TOG (wtfracoftog) made up by that compound. The ROG (reactive organic factor) fraction of TOG is included in the ORGPROF table, but is not used in the speciation calculation.
As can also be seen in the above diagram, for PM there are also PM size fraction values, which provide the particulate mass within each size fraction (PM total, PM 10, or PM 2.5) for individual source categories. To compute the amount of a specific chemical constituent in the PM size fraction of interest, each chemical compound's weight fraction in a given size fraction (e.g., PMSPEC:wtfracofpm10) must be multiplied by the appropriate weight fraction that that given size fraction is of the total PM (e.g., PMFRAC: wtfracPM10) size-based weight fraction (e.g., (wtfracpm10 x wtfracofpm10).
ARB's Excel files reflect the latest organic and particulate matter (PM) chemical speciation profiles, and how they are assigned to ARB's emission inventory source categories.
By way of background, the speciation profile data are applied to the Total Organic Gas (TOG) or Total Particulate Matter (PM) emissions from a source category to estimate the chemical species composition of the emissions. Further information on how to use the speciation profile Excel files follows.
(1.) A cross-reference file (SCC_ASSIGN_FRACTION) is also available that indicates which PM and Organic Gas profile is assigned to each source category in the inventory. The inventory source categories are represented by an 8-digit Source Classification Code (SCC) for point sources, or a 14-digit Emission Inventory Code (EIC) for area and mobile sources. This file also contains the fraction of reactive organic gas (FROG) values for organic profiles, and the PM 10 and PM 2.5 size fraction data for PM profiles. Some of the Organic Gas Speciation Profiles related to motor vehicles and fuel evaporative sources vary by the inventory year of interest, due to changes in fuel composition and vehicle fleet composition over time. The SCC_ASSIGN_FRACTION file for available inventory years is posted here in Excel format. Note that the YEAR field in this file may be 0 (zero). If it is zero, that means that this particular SCC code has the same profile set assigned for all years, whereas if an actual year value appears instead, it means that profile set applies only for that particular year and MAY change in other years.
The file also shows the PM size fractions for each category. The size fractions are the weight fractions of total Particulate Matter that are less than or equal to 10 microns and less than or equal to 2.5 microns aerodynamic diameter (FRAC PM10 and FRAC PM2.5, respectively) for each category.
(2.) The Organic Speciation Profiles (ORGPROF) file contains the weight fraction data (expressed as percent for ease of display) of each chemical in each profile. Each chemical fraction is multiplied by the Total Organic Gas (TOG) emissions for a source category to get the amount of each specific constituent chemical.
In addition to the chemical name for each chemical constituent, the file also shows the SAROAD code (a 5-digit internal identifier) and the Chemical Abstracts Service (CAS) number, which is a unique identifying code (up to 9 digits) assigned to chemicals by the CAS Registry Service.
(3.) The Particulate Matter (PM) Speciation Profile (PMPROF) file contains the weight fraction data (expressed as percent for ease of display) of each chemical in the profile, within each of the specified size fractions. Another file, the PMSIZE file, shows the PM size fractions for each profile.
The PM speciation profiles are applied in two steps. To get the amount of a specific chemical constituent in the total PM, each PM chemical weight fraction must be multiplied by the appropriate PM size fraction as well as the Total Particulate Matter (PM) emissions amount.
Note that the PM chemical speciation profile file is structured in two halves -- some profiles come in "original format" and some in "newer format". The "newer format" files are for a number of our newer profiles that include some supplemental "Other species" data. For example, some of the newer profiles contain data on Sulfates as well as total Sulfur content. Therefore, these newer-format profiles show these supplemental species separately, so as not to double count toward the total 100%.
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