Airport Air Quality Management 101 (2018)

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46 Airport Carbon Accreditation (ACA)—a program developed by the ACI for airports to track and reduce their GHG emissions. Airport Carbon and Emissions Reporting Tool (ACERT)—tool for tracking and managing progress in an airport’s Airport Carbon Accreditation program. Airport Construction Emissions Inventory Tool (ACEIT)—a tool developed under ACRP Project 02-33 (see ACRP Report 102) to facilitate emission calculations for construction projects at airports. Aviation Environmental Design Tool (AEDT)—FAA’s software that models aircraft perfor- mance in space and time to estimate fuel consumption, emissions, noise, and air quality consequences. AERMOD—EPA’s steady-state dispersion model designed for short-range (up to 50 kilometers) dispersion of air pollutant emissions. Air carrier—a commercial airline operating under the authority of the U.S. FAA. Airport Zero Emissions Vehicle and Infrastructure Pilot Program—an FAA program to improve airport air quality and facilitate use of zero emission technologies at airports. Air taxi—non-air-carrier commercial aircraft that fly scheduled service carrying passengers and freight on a limited basis. Air toxics—a pollutant that is hazardous to human health or the environment—typically a carcinogen, mutagen, or reproductive toxin—that is not covered under the NAAQS. Approach—the phase of a flight as a plane comes down from cruise altitude to landing on a runway; from an air quality perspective, the approach phase begins at the top of the mixing height (3,000 feet is commonly the default value used in air quality modeling). Area source—agglomeration of many sources that have low emission rates spread over a large area that are too numerous to treat individually (e.g., a parking lot). Attainment—a designation where the level of a criteria air pollutant meets the NAAQS; attain- ment is applied to a geographical area on a pollutant and averaging period basis. Auxiliary power unit (APU)—a self-contained power unit on an aircraft providing electrical/ pneumatic power to aircraft systems during ground operations. Avgas—aviation gasoline. Buoyancy—upward force exerted by a fluid. CAC—citizen advisory committee. Glossary

Glossary 47 Cargo aircraft—aircraft designed for the commercial transport of freight. Chemical reaction—the process of rearrangement of an element or a compound, thus forming a new chemical species, as opposed to a physical or nuclear change. Climb out—the phase of a flight following takeoff as the aircraft climbs toward cruise altitude; from an air quality perspective, the climb out phase ends at the top of the mixing height (3,000 feet is commonly the default value used in air quality modeling). Combustion—a rapid reaction with oxygen, producing heat as a byproduct. Commercial air carrier aircraft—aircraft operated on a scheduled basis by civilian international, national, regional, and commuter air carriers but also operated on an unscheduled basis by civilian charter operators. Complex terrain—a region having complex topography such as mountains, coastlines, or variations in land use that is likely to create unique local weather characteristics. Criteria pollutant—carbon monoxide (CO); lead (Pb); nitrogen dioxide (NO2), ozone (O3), particulate matter (PM), and sulfur dioxide (SO2). Deposition (dry and wet)—an atmospheric process of removal of air pollutants from the atmosphere onto the ground, without (dry) or with (wet) precipitation. Dispersion—the process by which atmospheric pollutants disseminate due to wind and vertical stability. Dispersion models—a mathematical simulation of how air pollutants are transported and dispersed in the ambient atmosphere. Downwash—disturbed atmospheric flow in the immediate vicinity of a structure. EMFAC—Emission factor model used to analyze mobile source emissions in California and to support regulatory and air quality planning efforts to meet FHWA’s transportation planning requirements. Emissions and Dispersion Modeling System (EDMS)—FAA’s legacy model to assess air quality impacts of proposed airport development projects. Emissions chemistry—the chemical transformation of pollutants within a plume or the atmosphere. Emissions inventory—the quantity or mass (e.g., lb or kg) of pollutant emissions from all sources on the airport or those within a study scope. Entrainment—transferring air or particles from the surrounding atmosphere into an organized air current. Environmental justice (EJ)—the fair treatment and meaningful involvement of all people regardless of race, color, national origin, or income with respect to the development, imple- mentation, and enforcement of environmental laws, regulations, and policies. Evaporation—changing from a liquid to a vapor. Fine particle—a particle that is 2.5 micrometers in diameter or smaller. Fugitive dust—sources such as unpaved road, storage piles, and heavy construction operations that discharge pollutants to the atmosphere in an unconfined flow stream. General aviation (GA) aircraft—aircraft that typically are privately owned and operated on a non-scheduled basis at a variety of facilities ranging from large commercial airports to small, privately owned airports.

48 Airport Air Quality Management 101 General conformity—rules to ensure that actions taken by federal agencies do not interfere with a state’s plan to attain and maintain the NAAQS. Geographic information system (GIS)—a system that integrates, stores, edits, analyzes, shares, and displays geographic information. Greenhouse gases (GHGs)—gases in the earth’s atmosphere that produce the greenhouse effect. Changes in the concentration of certain GHGs, due to human activity such as fossil fuel burn- ing, increase the risk of global climate change. Ground support equipment (GSE)—the broad category of vehicles and equipment that service aircraft, including those used for towing; maintenance; loading and unloading of passengers and cargo; and providing electric power, fuel, and other services to the aircraft. Hazardous air pollutant (HAP)—any of the 188 organic and inorganic chemicals and com- pounds identified by EPA that are regulated under the CAA as toxic air pollutants. Helicopter—an aircraft with rotating blades on a vertical axis through power supplied by an engine; helicopters are commonly used for medical evacuation, news and traffic reporting, and shorter trips where the origin and/or destination is not at an airport. Landing and takeoff (LTO) cycle—the phases of aircraft operations: approach, taxi, takeoff, and climb out. Maintenance area—an area previously designated “nonattainment” but redesignated as a “maintenance area” because air pollution levels have improved and are now in compliance with the NAAQS. Market-based measure (MBM)—an action or policy based on a pricing signal that is used to reduce aviation emissions such as taxes, charges, or emissions trading. Meteorology—weather-related parameters in the vicinity of the source. Military aircraft—aircraft operated by the U.S. Department of Defense including the full spectrum of aircraft types, ranging from high performance jet fighters to large transports to small-piston-engine training aircraft. Mixing height—the height of the completely mixed portion of the atmosphere that begins at ground level and extends to a few thousand feet overhead where the atmosphere becomes fairly stable (3,000 feet is commonly the default value used in air quality modeling). Mobile sources—moving vehicles that emit pollutants (e.g., aircraft, automobiles, and GSE). Motor Vehicle Emission Simulator (MOVES)—EPA’s emission modeling system that estimates emissions for mobile sources. National Ambient Air Quality Standards (NAAQS)—pollutant concentration levels established by EPA for six “criteria” air pollutants to ensure the outdoor air is safe for human health, the public welfare, and the environment. National Environmental Policy Act (NEPA)—the law requiring FAA and other federal agencies to consider the environmental impacts of their actions, which could include grants, loans, leases, permits, and approval of plans or projects. National Mobile Inventory Model (NMIM)—EPA’s emission modeling system for on-road motor vehicles and nonroad equipment. New source review (NSR)—an air quality permitting process under the Clean Air Act established to control air emissions from new or modified stationary sources using air pollution control technology or other emission reduction strategies.

Glossary 49 Nonattainment—a geographic area where the concentration of one or more of the criteria air pollutants is higher than the NAAQS as specified by pollutant and averaging period. NONROAD—a model that estimates air pollutant emissions from nonroad engines, equipment, and vehicles. Plume—a vertically or longitudinally moving, rising, or expanding mass of gas. Plume dynamics—of, or related to, the motion of a plume under the action of various atmo- spheric conditions. Point source—emission sources that come from a specific, stationary location (e.g., boilers, turbines, generators, and cooling towers). Pollutant concentration—amount of a pollutant within a reference volume of air [e.g., part per million (ppm) or microgram per cubic meter (µg/m3)]. Prevention of significant deterioration (PSD)—regulations intended to prevent degradation of air quality in a geographic area whose air is relatively clean and in attainment with the NAAQS. Receptor—a specified point on or above the ground at which pollutant concentrations are measured or computed. Shear—the local variation in the movement of a gas mass (e.g., plume) in a given direction across the ambient or prevailing atmosphere. Smoke number—a dimensionless term that quantifies smoke emissions from aircraft engines as a surrogate for particulate emissions. Stakeholder—any group or individual who can affect or is affected by the achievement of an organization’s objectives. Startup—the process of starting the aircraft main engine. State implementation plan (SIP)—a state’s detailed description of the regulations, programs, and measures to be used in that state for nonattainment and maintenance areas to reduce air pollution to attain the NAAQS for all criteria pollutants within required timeframes. Stationary source—a source of emissions that is immobile (e.g., fuel tank, degreaser, or power plant). In dispersion modeling, stationary sources can be modeled as point, area, or volume sources. Steady-state—meteorological conditions that are not changing with time. Takeoff—the phase of a flight where the aircraft accelerates down a runway and lifts off and continues until it has sufficient air speed to reduce its power and transition into the climb out mode. Taxi in—operating an aircraft on the ground from the runway to the gate after landing. Taxi out—operating an aircraft on the ground from the gate to the runway prior to takeoff. Time-in-mode—the time that an aircraft spends in each mode of the landing and takeoff (LTO) cycle. Title V—the section of the Clean Air Act Amendments of 1990 that requires emitters to have an operating permit that ensures its operations are consistent with the goals of the law. Transportation conformity—the rule that requires project-level conformance with PM air quality standards in nonattainment and maintenance areas for new transportation projects such as those around a congested intersection.

50 Airport Air Quality Management 101 Ultrafine particle—a particle that is 1 micrometer in diameter or smaller. Unburned hydrocarbons (UHCs)—uncombusted fuel emitted from an engine. Unclassifiable—not able to be assigned to a particular attainment class or category due to insufficient data. Vehicle mile of travel (VMT)—the product of the number of vehicles on a given roadway by the length of the roadway commonly measured in vehicle miles/year. Velocity—speed at which a gas moves with respect to a stationary reference, such as the airport. Volkswagen Settlement—$2.7 billion fund available to airports and others to remediate envi- ronmental effects of excess NOx emissions from vehicles modified by Volkswagen to defeat EPA vehicle emission standards. Voluntary Airport Low Emission (VALE)—a program designed to reduce all sources of airport ground emissions using Airport Improvement Program (AIP) funds and Passenger Facility Charges to finance low-emission vehicles, refueling and recharging stations, gate electrifica- tion, and other airport air quality improvements.