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Lower High Falls, Talladega Forest - Bill Wilson
Emissions Modeling & Inventory

The Air Division is charged with the responsibility of insuring that Alabama's air quality meets federal standards. The Air Division has several QA/QC methods that can be used in order to analyze the quality of Alabama's air. Computer models use air emissions to simulate what the ground-level concentrations of a pollutant(s) would be using meteorological data and terrain information. Stack tests are conducted to measure the actual levels of emissions that are being released by a facility. Emission inventories use the past year's actual emissions to analyze emission trends.

In some situations, including the Prevention of Significant Deterioration (PSD) program, receiving a permit may involve dispersion modeling to determine the impact of source emissions on air quality. The ADEM Air Division has developed a set of modeling guidelines to help applicants with the procedures involved in modeling.

Emissions measurements include source sampling, air toxics monitoring, continuous emissions monitoring system (CEMS) certification, CEMS audits, and visible emissions detection training and certification. Source sampling activities involve the observation of emissions tests at regulated and non-regulated industrial facilities throughout the state and the evaluation of reports from these emissions tests. The Air Toxics Program includes monitoring for hazardous compounds at both regulated and non-regulated facilities. Monitoring efforts have included fenceline sampling at pulp and paper mills, chemical plants, landfills, and other sources of hazardous air pollutants.

Emissions Inventory

An emissions inventory is a tool that uses the past year's emissions to analyze emission trends. Trends in emissions can alert the Air Division to potential air quality problems. A statewide emission inventory contains actual and estimated emissions from the following sources:

Point sources - large industries, such as power plants, paper mills, chemical plants, manufacturing plants, etc.

Area sources - smaller sources that don't emit much pollution on their own, but when collectively analyzed in any area, can contribute significantly to air emission totals. Examples include dry cleaners, gasoline stations, bakeries, surface coaters, solvent cleaning, etc.

Onroad Mobile sources - vehicles that use roadways, such as cars, trucks, SUVs, diesel trucks, motorcycles, etc

Nonroad Mobile sources - vehicles that do not utilize roadways, such as boats, airplanes, construction equipment, railroad equipment, yard and agricultural equipment, etc.

Biogenic sources - natural sources that release emissions into the air, such as trees, soil, animals, decaying vegetation, etc.

The actual type of emissions that are released can be categorized as criteria pollutants (main pollutants, such as nitrogen oxides, sulfur dioxide, carbon monoxide, volatile organic compounds, lead, and particulate matter) or hazardous air pollutants (air toxics, such as benzene, toluene, vinyl chloride, methanol, formaldehyde, mercury, etc.).

National Emissions Inventory (NEI)

The National Emissions Inventory (NEI) contains toxic and criteria air pollutant data needed for regional scale and human exposure modeling. It is primarily for state, local, and tribal air agency use.

Every three years, EPA accepts point source data, area source data, onroad mobile source data, nonroad mobile source data, and biogenics data from agencies. Although most of the agencies do not have the capability to inventory all of these different factions, agencies submit what they do have. EPA supplements the missing data with estimates of their own. EPA then sends the complete inventory back to the agencies for review. After corrections are made, a final inventory is created. The entire process takes approximately 2 years.

The ADEM Air Division submitted criteria pollutant data for point sources in 1998 (the first year the NEI was established) for emissions released in calendar year 1996. In 2001, the ADEM Air Division submitted criteria and toxics data for point sources, as well as some criteria pollutant data for area sources and nonroad mobile sources, and some input data for the onroad mobile sources. This submittal was for emissions released in calendar year 1999. Since then, the ADEM Air Division has submitted emissions inventories for the 2002 and 2005 calendar years. Data for the 2008 National Emissions Inventory must be submitted by June 1, 2010.

National Emissions Inventories (NEI)
National Air Toxic Assessment (NATA)

Contact Information

Attn: Air Division
Post Office Box 301463
Montgomery, Alabama 36130-1463
(334) 271-7861
(334) 279-3044 fax