Improving Ground Support Equipment Operational Data for Airport Emissions Modeling (2015)

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62 Air carrier: An operator (e.g., airline) in the commercial system of air transportation con- sisting of aircraft that hold certificates of Public Convenience and Necessity issued by the department of transportation to conduct scheduled or nonscheduled flights within the country or abroad. Air pollution: One or more chemicals or substances in high enough concentrations in the air to harm humans, other animals, vegetation, or materials. Such chemicals or physical conditions (such as excess heat or noise) are called air pollutants. Airport operators: Airport owners/operators and their representatives (e.g., consultants and contractors). Among the various emission source categories typically included in SIPs, airports characteristically encompass a unique assembly of mobile sources including aircraft, APUs, and GSE. As such, airport operators are well incentivized and uniquely positioned to ensure that these emissions are properly represented and accounted for in SIPs. Attainment area: Any area that meets the NAAQS established for the criteria air pollutants Auxiliary power units (APUs): APUs are small turbine engines used by many commercial jet aircraft to start the main engines; provide electrical power to aircraft radios, lights, and other equipment; and to power the onboard air conditioning (heating and cooling) system. Carbon monoxide (CO): A product of incomplete combustion, is relatively non-reactive, and is mostly associated with motor vehicle traffic. High CO concentrations develop primarily during winter when periods of light winds interact with ground level temperature inversions (typically from the evening through early morning) and reduce the dispersal of vehicle emis- sions. Motor vehicles also exhibit increased CO emission rates at low air temperatures. When inhaled at high concentrations, CO combines with hemoglobin in the blood and reduces its oxygen-carrying capacity, resulting in reduced oxygen reaching the brain, heart, and other body tissues. This condition is especially critical for people with cardiovascular diseases, chronic lung disease, or anemia. Clean Air Act (CAA): The federal law regulating air quality. The first CAA, passed in 1967, required that air quality criteria necessary to protect the public health and welfare be developed. Since 1967, there have been several revisions to the CAA. The CAA Amendments (CAAA) of 1990 represent the fifth major effort to address clean air legislation. Clean Air Act Amendments (CAAA) of 1990: The CAAA of 1990 represent the fifth major effort to address clean air legislation. Revisions include significant strengthening of CAA, espe- cially by adding detailed requirements for federal actions to conform to State Implementation Plans (SIPs), expanding the list of hazardous air pollutants from eight to 189, and strengthening the operating permit program. Glossary

Glossary 63 Criteria pollutant: A pollutant determined to be hazardous to human health and regulated under the U.S. EPA’s National Ambient Air Quality Standards. The 1970 amendments to the CAA require the U.S. EPA to describe the health and welfare impacts of a pollutant as the “criteria” for inclusion in the regulatory regime. The standards are designed to protect both the public health—known as primary standards—and welfare (or the natural environment)— known as secondary standards—when applied to ambient (i.e., outdoor) conditions. Criteria pollutants are CO, nitrogen oxides (NOx), volatile organic compounds (VOCs), sulfur oxides (SOx), particulate matter (PM) equal to or less than 10 micrometers (coarse particulates or PM10), PM equal to or less than 2.5 micrometers (fine particulates or PM2.5), and lead (Pb). Emission factor: The rate at which pollutants are emitted into the atmosphere by one source or a combination of sources. Emissions: Releases of gases to the atmosphere (e.g., the release of carbon dioxide during fuel combustion). Emissions can be either intended or unintended releases. Emissions and Dispersion Modeling System (EDMS): The EDMS is designed to assess the air quality impacts of airport emissions sources, particularly aviation sources. In 1998, the FAA revised its policy on air quality modeling procedures to identify EDMS as the required model to perform air quality analyses for aviation sources instead of the preferred model. This revised policy ensures the consistency and quality of aviation analyses performed for the FAA. The FAA continues to enhance the model under the guidance of its government/industry advisory board to more effectively determine emission levels and concentrations generated by typical airport emission sources. Emissions inventory: A list of air pollutants emitted into the atmosphere of a community, state, nation, or the Earth, in amounts per some unit time (e.g., day or year) by type of source. An emission inventory has both political and scientific applications. General aviation: The portion of civil aviation that encompasses all facets of aviation except air carriers. It includes any air taxis, commuter air carriers, and air travel clubs that do not hold Certificates of Public Convenience and Necessity. General Conformity Rule: Rule that ensures that federal actions comply with the NAAQS. In order to meet this CAA requirement, a federal agency must demonstrate that every action that it undertakes, approves, permits or supports will conform to the appropriate SIP. Refer to the EPA website for more details. Greenhouse gases (GHG): Gases that trap heat in the atmosphere. The most prevalent GHGs are CO2, methane (CH4), and nitrous oxide (N2O), and fluorinated gases. Ground support equipment (GSE): Equipment that services aircraft after arrival and before departure at an airport and also the vehicles that support the operation of the airport. The types of GSE at airports include aircraft tugs, baggage tugs, deicers, fuel trucks, hydrant carts, catering trucks, cargo tractors, water trucks, lavatory trucks, cabin service, belt loaders, and cargo loaders. Jet fuel: Includes both naphtha-type and kerosene-type fuels meeting standards for use in air- craft turbine engines. Although most jet fuel is used in aircraft, some is used for other purposes such as generating electricity. Landing and takeoff (LTO) cycle: One aircraft LTO is equivalent to two aircraft operations (one landing and one takeoff). The standard LTO cycle begins when the aircraft crosses into the mixing zone as it approaches the airport on its descent from cruising altitude, lands, and taxis to the gate. The cycle continues as the aircraft taxis back out to the runway for takeoff and climbout as it heads out of the mixing zone and back up to cruising altitude. The five specific operating modes in a standard LTO are approach, taxi/idle-in, taxi/idle-out, takeoff, and climbout. Most aircraft go through this sequence during a complete standard operating cycle.

64 Improving Ground Support Equipment Operational Data for Airport Emissions Modeling Maintenance area: Any area that is in transition from formerly being a nonattainment area to an attainment area. National Plan of Integrated Airport Systems (NPIAS): The NPIAS identifies nearly 3,400 exist- ing and proposed airports that are significant to national air transportation and thus eligible to receive federal grants under the Airport Improvement Program. National Ambient Air Quality Standards (NAAQS): Air quality standards established by the EPA to protect human health (primary standards) and to protect property and aesthetics (secondary standards). National Environmental Policy Act (NEPA): An Act established “ . . . to declare a national policy which will encourage productive and enjoyable harmony between man and his environ- ment; to promote efforts which will prevent or eliminate damage to the environment and bio- sphere and stimulate the health and welfare of man; to enrich the understanding of the ecological systems and natural resources important to the Nation; and to establish a Council on Environ- mental Quality.” [42 USC § 4321—Congressional declaration of purpose] Nitrogen oxides (NOx): Gases consisting of one molecule of nitrogen and varying numbers of oxygen molecules. Nitrogen oxides are produced, for example, by the combustion of fossil fuels in vehicles and electric power plants. In the atmosphere, nitrogen oxides can contribute to formation of photochemical ozone (smog), impair visibility, and have health consequences; they are considered pollutants. Nitrogen dioxide (NO2): A pollutant that acts as a respiratory irritant. NO2 is a major com- ponent of the group of gaseous nitrogen compounds commonly referred to as NOx. A precursor to ozone formation, NOx is produced by fuel combustion in motor vehicles, stationary sources used in industrial activities, ships, aircraft, and rail transit. Typically, NOx emitted from fuel combustion is in the form of nitric oxide (NO) and NO2. NO is often converted to NO2 when it reacts with ozone or undergoes photochemical reactions in the atmosphere. Nonattainment area: Any area that does not meet (or that contributes to ambient air quality in a nearby area that does not meet) the NAAQS. Non-methane volatile organic compounds (NMVOCs): Organic compounds, other than methane, that participate in atmospheric photochemical reactions. Ozone: A colorless gas with a pungent odor, having the molecular form of O3, found in two layers of the atmosphere, the stratosphere and the troposphere. Ozone is a form of oxygen found naturally in the stratosphere that provides a protective layer shielding the Earth from ultraviolet radiation’s harmful health effects on humans and the environment. In the troposphere, ozone is a chemical oxidant and major component of photochemical smog. Ozone can seriously affect the human respiratory system. Ozone precursors: Chemical compounds, such as carbon monoxide, methane, non-methane hydrocarbons, and nitrogen oxides that, in the presence of solar radiation, react with other chemical compounds to form ozone, mainly in the troposphere. Particulate matter (PM10/2.5): Solid particles or liquid droplets suspended or carried in the air. Particulate matter equal to or less than 10 microns in diameter (PM10) and particulate matter equal to or less than 2.5 microns in diameter (PM2.5) represent fractions of particulate matter that can penetrate deeply into the respiratory system and cause adverse health effects. Particulate matter in the atmosphere results from many kinds of dust- and fume-producing industrial and agricultural operations, fuel combustion, and atmospheric photochemical reactions. Parts per million (ppm): Number of parts of a chemical found in one million parts of a par- ticular gas, liquid, or solid.

Glossary 65 Regulatory agencies: State, regional, and/or local air quality regulatory and planning agen- cies involved in preparing and updating SIPs. In this role, their work involves the preparation of emissions inventories for all emissions sources within the nonattainment and maintenance area (including airports), determining the appropriate amounts of emissions allowable region- ally, and formulating the necessary emissions reduction strategies and milestones to meet the NAAQS within prescribed timeframes. State Implementation Plan (SIP): Under the federal CAA, states are required to submit an SIP to the U.S. EPA for those counties or regions where air quality conditions do not meet one or more of the NAAQS. The SIP describes how each nonattainment region will attain and maintain the NAAQS. SIPs typically include emissions inventories, air quality monitoring data, emissions reduction goals and objectives, timetables, emissions control measures and strate- gies considered necessary for nonattainment and maintenance areas to meet the NAAQS, and enforcement mechanisms. Sulfur dioxide (SO2): A compound composed of one sulfur and two oxygen molecules. Sulfur dioxide emitted into the atmosphere through natural and anthropogenic processes is changed in a complex series of chemical reactions in the atmosphere to sulfate aerosols. These aerosols are believed to result in negative radiative forcing (i.e., tending to cool the Earth’s surface) and result in acid deposition (e.g., acid rain). Time-in-mode (TIM): The time that GSE are on and in use servicing an aircraft. Volatile organic compounds (VOCs): Organic compounds that evaporate readily into the atmosphere at normal temperatures. VOCs contribute significantly to photochemical smog pro- duction and certain health problems.