National Academies Press: OpenBook

Research Needs Associated with Particulate Emissions at Airports (2008)

Chapter: Chapter 3 - Primer on Particulate Matter Emissions From Aviation

« Previous: Chapter 2 - Background
Page 5
Suggested Citation:"Chapter 3 - Primer on Particulate Matter Emissions From Aviation." National Academies of Sciences, Engineering, and Medicine. 2008. Research Needs Associated with Particulate Emissions at Airports. Washington, DC: The National Academies Press. doi: 10.17226/14160.
×
Page 5
Page 6
Suggested Citation:"Chapter 3 - Primer on Particulate Matter Emissions From Aviation." National Academies of Sciences, Engineering, and Medicine. 2008. Research Needs Associated with Particulate Emissions at Airports. Washington, DC: The National Academies Press. doi: 10.17226/14160.
×
Page 6
Page 7
Suggested Citation:"Chapter 3 - Primer on Particulate Matter Emissions From Aviation." National Academies of Sciences, Engineering, and Medicine. 2008. Research Needs Associated with Particulate Emissions at Airports. Washington, DC: The National Academies Press. doi: 10.17226/14160.
×
Page 7
Page 8
Suggested Citation:"Chapter 3 - Primer on Particulate Matter Emissions From Aviation." National Academies of Sciences, Engineering, and Medicine. 2008. Research Needs Associated with Particulate Emissions at Airports. Washington, DC: The National Academies Press. doi: 10.17226/14160.
×
Page 8
Page 9
Suggested Citation:"Chapter 3 - Primer on Particulate Matter Emissions From Aviation." National Academies of Sciences, Engineering, and Medicine. 2008. Research Needs Associated with Particulate Emissions at Airports. Washington, DC: The National Academies Press. doi: 10.17226/14160.
×
Page 9
Page 10
Suggested Citation:"Chapter 3 - Primer on Particulate Matter Emissions From Aviation." National Academies of Sciences, Engineering, and Medicine. 2008. Research Needs Associated with Particulate Emissions at Airports. Washington, DC: The National Academies Press. doi: 10.17226/14160.
×
Page 10
Page 11
Suggested Citation:"Chapter 3 - Primer on Particulate Matter Emissions From Aviation." National Academies of Sciences, Engineering, and Medicine. 2008. Research Needs Associated with Particulate Emissions at Airports. Washington, DC: The National Academies Press. doi: 10.17226/14160.
×
Page 11

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

5This section presents basic information on particulate matter (PM) emissions in general and aviation emissions specifically. Research activities are described, as are regulatory requirements. Analytical tools that are used to analyze these emissions are also described. Much of the general informa- tion on particulate matter is adapted from U.S. EPA data and information compiled in support of the National Ambient Air Quality Standards (NAAQS) for particulate matter.1,2,3 What is PM? Particle pollution from fuel combustion is a mixture of mi- croscopic solids, liquid droplets, and particles with solid and liquid components suspended in air. Solid particles are referred to as nonvolatile particles and liquid droplets are referred to as volatile particles. This pollution, also known as particulate matter, is made up of a number of components, including soot or black carbon particles, inorganic acids (and their corre- sponding salts, such as nitrates and sulfates), organic chemicals from incomplete fuel combustion or from lubrication oil, abraded metals, as well as PM present in the ambient air due to natural sources, such as soil or dust particles, and allergens (such as fragments of pollen or mold spores). The diameters of particles in the ambient atmosphere span five orders of magnitude, ranging from 0.001 μm (or 1 μm) to 100 μm. Larger particles, such as dust, soil, or soot, are often large or dark enough to be seen with the naked eye. Others are so small they can only be detected using an elec- tron microscope. Particle size is critical to the health effects it poses since smaller particles can be inhaled more deeply into the lungs, with a more significant potential health impact compared to larger particles. Residence time in the air is also dependent on size. Particle size also is a key determinant of visibility impacts. Larger particles, those smaller than 10 μm4 but larger than about 2.5 μm, are referred to as coarse particles and typically represent most of the mass included in PM10, the mass of particles smaller than 10 μm. Particles between 2.5 μm and 0.1 μm are referred to as fine particles. A particle 2.5 μm in di- ameter is approximately one-thirtieth the diameter of a human hair. Particles below 0.1 μm are considered ultrafine particles. Together, fine and ultrafine particles are represented as PM2.5, meaning all particles less than 2.5 μm. How is PM Formed? Different particle types tend to have different sources and formation mechanisms. Coarse particles around airports are generally primary particles from sources such as wind-blown dust, sea spray, sand or salt storage piles, construction activ- ity, or crushing or grinding operations (most commonly associated with construction activity). Ultrafine particles can arise from a number of sources as well, including primary PM produced during combustion or newly nucleated (e.g., con- densed) particles formed in the atmosphere or in aircraft plumes from condensable gases. Ultrafine particle emission sources at airports include various fuel combustion sources such as aircraft, auxiliary power units (APU), ground support equipment (GSE), power turbines, diesel emergency genera- tors, and vehicle traffic in and around the airport, as well as the atmospheric generation of new volatile particles from condensation. Ultrafine particles in aircraft exhaust include a variety of particle types ranging from those that form in the combustor (carbon particles), to those that nucleate from C H A P T E R 3 Primer on Particulate Matter Emissions From Aviation 1 Fine Particle (PM 2.5) Designations, Basic Information http://www.epa.gov/ pmdesignations/basicinfo.htm. 2 Particulate Matter, Basic Information http://www.epa.gov/oar/particlepollution/ basic.html. 3 Review of the National Ambient Air Quality Standards for Particulate Matter: Policy Assessment of Scientific and Technical Information, December 2005, http://www.eap.gov/ttn/naaqu/standards/pm/data/pmstaffpaper_20051221.pdf. 4 In this paper, particle size descriptions refer to the aerodynamic diameter (see definition for “classical aerodynamic diameter” in glossary).

condensable gases (sulfuric acid, partially burned fuel, and vaporized lubrication oil) and grow larger as a result of coag- ulation and condensation onto the particle surfaces in the 0.1 to 0.5 μm range. Diesel particles from GSE and other ground vehicles tend to be larger than aircraft particles and aggregate into chain particles rather than the more spherical particles seen from aircraft engines. The particles described here, which are emitted directly from a source or form in the immediate vicinity of the source, are referred to as primary particles or primary PM. Figure 1 illustrates the range of PM commonly encountered. Secondary particle formation, which results from complex chemical reactions in the atmosphere and/or particle nucle- ation processes, can produce either new particles or add to pre-existing particles. Examples of secondary particle forma- tion include: (1) the conversion of sulfur oxides (SOx), which are produced by oxidation of the sulfur in fossil fuels, to sulfuric acid (H2SO4) vapor, which then forms droplets as the sulfuric acid condenses due to its low vapor pressure. The resulting sulfuric acid aerosol can further react with gaseous ammonia (NH3) in the atmosphere, for example, to form various particles of sulfate salts (e.g., ammonium sulfate (NH4)2SO4); (2) the conversion of nitrogen dioxide (NO2) to nitric acid (HNO3) vapor that interacts with PM in the atmosphere, and reacts further with ammonia to form ammonium nitrate (NH4NO3) particles; and (3) reactions involving gaseous volatile organic compounds (VOC), yield- ing condensable organic compounds that can also contribute to atmospheric particles, forming secondary organic aerosol particles. The complex reactions that take place as a result of nucleation, condensation, accumulation, and reaction illus- trate why measuring PM emissions can be so complex. Aircraft engine emission standards apply at the engine exit, yet PM of concern to regulators and the community is not fully formed at that point. Figure 2 illustrates the evolution of primary and secondary particles. Ultrafine, fine, and coarse particles typically exhibit differ- ent behaviors in the atmosphere as the ambient residence time of particles varies with size. Ultrafine particles have a relatively short life, on the order of minutes to hours, and generally travel from less than a mile to less than 10 mi since they are likely to grow larger into fine particles. Fine particles remain suspended longer in the atmosphere since they do not grow larger and are too small to readily settle out or impact on stationary surfaces. They can be transported thousands of miles and remain in the atmosphere from days to weeks. Coarse particles can settle rapidly from the atmosphere with lifetimes ranging from minutes to hours (occasionally a few days) depending on their size, atmospheric conditions, and altitude. Large coarse particles are generally too large to follow air streams and tend to settle out gravitationally and by impacting onto stationary surfaces, rarely traveling more than 10 mi. Fine and ultrafine particles suspended in the atmosphere absorb and reflect light, which is the major cause of reduced visibility (haze) in parts of the United States. Sulfates, nitrates, organic matter, and elemental carbon are primary components of these small particles. 6 0.001 0.010 0.100 1.00 10.0 100. Gas phase Condensed gas aircraft carbon particle nucleation accumulation ultrafine particles large primary particle -like windblown dust or fly ash fine particles coarse particles PM 2.5 PM 10 diesel carbon particle Particle Diameter (micrometers) human hair Figure 1. Particle size of airport PM emission.

How Does PM Affect Health? Coarse particles can be inhaled but tend to remain in the nasal passage. Smaller particles are more likely to enter the res- piratory system. Health studies have shown a significant asso- ciation between exposure to fine and ultrafine particles and premature death from heart or lung disease. Fine and ultrafine particles can aggravate heart and lung diseases and have been linked to effects such as cardiovascular symptoms, cardiac arrhythmias, heart attacks, respiratory symptoms, asthma attacks, and bronchitis. These effects can result in increased hospital admissions, emergency room visits, absences from school or work, and restricted activity days. Individuals that may be particularly sensitive to fine particle exposure include people with heart or lung disease, older adults, and children. How is PM Regulated in the United States? A wide range of regulatory provisions intended for environmental purposes applies to airport activity and equip- ment. Aircraft engines have certification requirements for smoke emissions; ground access vehicles are subject to tailpipe emission standards; the composition of jet fuel, diesel fuel, and gasoline is regulated to limit harmful emissions; many op- erational activities and equipment require operating permits; and airport construction and expansion plans are subject to constraints where the regional air quality does not meet healthy standards. EPA sets most regulatory standards and many are administered by state agencies. FAA is responsible for ensuring these regulations do not pose conflicts with safety and other requirements especially for aircraft operations. This regulatory structure has developed over the past several decades. As a result of health and visibility concerns from PM, EPA set the first NAAQS for PM in 1971. At the time, standards for “total suspended particles” (TSP) were based on the mass- based concentration of particles between 25 and 45 μm, which then was the state-of-the-art for particle samplers. The primary (health-based) standard was set at 260 μg per cubic meter of ambient air, 24-hour average, not to be exceeded more than once per year and 75 μg/m3 annual average. A secondary (welfare-based) standard of 150 µg/m3, 24-hour average, not to be exceeded more than once per year was also established. The standards were revised in 1987 (moving from TSP to PM10), 1997 (adding PM2.5), and again in 2006. The 2006 standards set levels for PM10 of 150 µg/m3 for 24-hour average and for PM2.5 of 35 µg/m3 for 24-hour average and 15 µg/m3 annual average. The welfare-based secondary standards were made the same as the primary standard in 2006. EPA no longer regulates parti- cles larger than 10 μm (e.g., sand and large dust) since they are not deemed readily inhalable. Recent studies by EPA have shown that PM2.5 cannot be used as a surrogate for ultrafine particles, so future regulatory reviews may emphasize smaller particles, possibly using PM1.0 as the regulatory standard. The regulatory approach of the EPA sets standards for ambient air quality in geographic regions that generally rep- resent metropolitan areas. The local PM concentration is the sum of all regional sources of PM and the regional ambient background. The EPA estimates the annual average back- ground for PM10 ranges from 4 to 8 µg/m3 in the western 7 ambient mixing/dilution coated soot particles ~30-100 nm diameter condensation H H2O 2SO4HCs accumulation binary collision nucleation nucleation/accumulation mode particles <20 nm diametersoot activation/scavenging aircraft exhaust soot particles chemistry hydrocarbons (HCs) SO3 H2SO4 H2O H2O Aircraft engines emit a mixture of soot and volatile gases. As pictured above, these gases cool to ambient temperature by mixing with ambient air and convert to the particle phase by condensation and nucleation/growth. The nucleation/growth mode particles and soot coatings are complex mixtures of sulfuric acid, water, partially burned hydrocarbons, and engine oil. Figure 2. Evolution of particulate matter from aircraft engine exhaust.

United States and 5 to 11 µg/m3 in the eastern United States; for PM2.5, estimates range from 1 to 4 µg/m3 in the west to 2 to 5 µg/m3 in the east. Particulate matter emissions from airport and other regional sources mix relatively quickly with the ambient background PM. The combination of emissions from airports and other regional sources and ambient con- centrations of PM result in a combined atmospheric PM loading that depends on complex, nonlinear atmospheric processes, including chemical reactions and pollution trans- port. This makes it difficult to isolate the contribution of air- port activity from all other emissions sources in an area. In addition to the NAAQS, there are other regulations that directly or indirectly effect PM emissions from aviation. For example, the International Civil Aviation Organization (ICAO) has established aircraft engine certification stan- dards5 that limit smoke emissions, as measured by “smoke number.” Since smoke is a component of total PM, these standards indirectly influence aircraft PM emissions. The ICAO has also established international certification limits for oxides of nitrogen (NOx) from jet engines. These limit the amount of NOx emitted, which can produce nitrates that condense in the atmosphere hours to days after emissions forming secondary volatile particles. The EPA has adopted ICAO’s certification standards as national regulations and FAA in turn monitors and enforces engine certification. Sulfur in jet fuel combines with oxygen from the air dur- ing combustion, producing sulfur dioxide (SO2). This SO2 is further oxidized to sulfuric acid after leaving the engine, and eventually all of the fuel sulfur becomes sulfate. A small frac- tion (a few percent or less) of the sulfur converts to sulfate before the engine plume disperses, and is considered part of the primary particulate matter emissions. The remaining sulfur converts to sulfate hours to days after the emission, contributing to secondary particulate matter. Sulfur emis- sions are directly related to the sulfur content of the fuel. Internationally accepted standards6 for Jet A, which is the commercial aviation fuel used in the United States, limit fuel sulfur content to 0.30% wt. maximum. In practice, however, Jet A sulfur content ranges between 0.04 and 0.06% wt.7 Nonroad diesel equipment, such as GSE, is not required to have emission controls like diesel vehicles licensed for on-road use. Under new national regulations, EPA is requiring diesel fuel suppliers for nonroad equipment to reduce fuel sulfur content, eventually to the same ultra-low sulfur limits required for on-road diesel. This will allow the nonroad equipment to use advanced emission control technologies, which may be a requirement for these vehicles in the future. These require- ments for diesel fuel sulfur limits and engine emission stan- dards are being phased in between now and 2014. Reducing the fuel sulfur content and adding emission controls will reduce PM emissions from nonroad equipment by 90%.8 GSE using alternative fuels such as compressed natural gas, propane, or electricity9 have very little or no PM emissions. Stationary emission sources at airports include various facilities and equipment like boilers, emergency generators, incinerators, fire training facilities, and fuel storage tanks. Many of these equipment types require specific operating permits with PM emission limits. Stationary sources typically represent about 1% of PM emissions at airports. The National Environmental Policy Act of 1969 (NEPA) established a policy to protect the quality of the human envi- ronment and requires careful scrutiny of the environmental impacts of federal actions, which could include grants, loans, leases, permits, and other decisions or actions requiring federal review or approval. For airports, NEPA applies to most major construction projects as a result of FAA funding or approval. One of the most common assessments used to confirm NEPA compliance for airport projects is “general conformity,” which seeks to ensure that actions approved by the federal govern- ment do not cause increases in emissions that could exceed air quality standards. This serves to indirectly limit increases in ambient PM and other emissions. What are the Sources of PM at an Airport? There are many individual PM emission sources at air- ports. These include the following: • Aircraft engines, • Aircraft auxiliary power units (APU), • Ground support equipment (GSE), • Passenger vehicles, • Tire and brake wear, • Stationary power turbines, • Training fires, • Sand and salt piles, and • Construction grading and earth moving. Particulate matter emissions from each of these sources are different in terms of size, composition, and rate. Emissions from these sources can be quantified by direct measurement using monitoring equipment or estimated using emission 8 5 International Civil Aviation Organization, International Standards and Recom- mended Practices, Environmental Protection, Annex 16 to the Convention on International Civil Aviation, Volume II, Aircraft Engine Emissions. 6 ASTM International D 1655-04a, Standard Specification for Aviation Turbine Fuels. 7 Intergovernmental Panel on Climate Change, Aviation and the Global Atmo- sphere (1999). 8 Environmental Protection Agency, Office of Transportation and Air Quality, Final Regulatory Analysis: Control of Emissions from Non-Road Diesel Engines, EPA420-R-04-007, May 2004. 9 PM is emitted during electricity generation at the power plant; however, utility power production is well controlled compared to internal combustion engines and the net result is fewer PM emissions.

inventory methods. Historically for airport sources, emis- sions inventory methods have been most prevalent. These methods generally require information about each source’s population, size, activity rate, and a PM emission factor or emission index. An emissions factor is a representative value that attempts to relate the quantity of a pollutant released to the atmosphere with an activity associated with the release of that pollutant. These factors are usually expressed as the weight of pollutant divided by a unit weight, volume, dis- tance, or duration of the activity emitting the pollutant (e.g., milligrams of particulate emitted per kilogram of fuel burned). Such factors make it easier to estimate emissions from various sources of air pollution. In some cases, these factors are simply averages of all avail- able data of acceptable quality, and are generally assumed to be representative of long-term averages for all facilities in the source category (i.e., a population average). EPA maintains a reference10 of emission factors for many sources. In other cases, specific emission factors are compiled for each emis- sion source. For example, gaseous emission factors specifi- cally for aircraft are included in the ICAO Aircraft Engine Emissions Data Bank.11 Unfortunately, PM emission factors for aircraft, the largest PM source at airports, are not included in the Emissions Data Bank. Aircraft engine particulate emis- sions have not been well studied or characterized in the past and are only now being tested. Smoke number data are in the ICAO databank, but are only surrogates for PM emissions via the First Order Approximation (FOA) (see below). The second largest PM source at airports is commonly GSE, sometimes comparable to aircraft as a PM source. Ground sup- port equipment is mostly powered by diesel engines although a smaller percentage have gasoline engines and a smaller per- centage still use electric power. The diesel and gasoline engines used by GSE are common engine types found in trucks and other industrial vehicles. Particulate matter emissions from these engines are well characterized for mass of emissions; however, in emission factor references, GSE is typically lumped into a diverse set of equipment referred to as nonroad vehicles. These also include lawn and garden equipment, agricultural equipment, commercial marine vessels, recreational equip- ment, and other vehicle types. This makes it difficult to com- pute PM inventories that reflect airport-specific emissions. What are the Most Recent Aviation PM Research Efforts? To remedy the lack of information about PM emissions from aircraft, several initiatives have been pursued in the last few years. The FAA developed the FOA, initially in 2002, as an approach to estimate emissions based on smoke num- ber, a measure of soot obscuration in aircraft plumes. More recently, FAA, NASA, EPA and others funded a series of air- craft engine emission measurement programs known as APEX (Aircraft Particle Emissions eXperiment). The infor- mation from the first APEX1 tests, initially published in 2006, is basic, fundamental data on the quantity and char- acteristics of PM from a single engine type. The JETS- APEX2 study, from which a report has been released by the California Air Resources Board (CARB), and APEX3, from which a report is to be released soon, cover a range of commercial engines, but the data are still limited relative to the entire fleet. Another initiative organized to help close the knowledge gap on aviation PM emissions is the National PM Roadmap for Aviation. It is a PM research collaboration among federal agencies (e.g., FAA, NASA, DOT, DOD, and EPA), universi- ties, aircraft and engine manufacturers, airports, airlines, and other stakeholders. It was organized in 2004 to coordinate aviation PM research and leverage limited resources to focus on the most important research needs. Recently, the ACRP funded this study of aviation PM emissions and a second study (ACRP 02-04A), which is an assessment of the data from the APEX tests. ACRP initiatives should help bring needed focus to airport-specific PM emis- sion concerns. Why are Aviation-Related PM Issues so Important to Airport Operators? Airports today are faced with community, employee, and regulatory concerns about PM emissions, yet they have very limited data on PM emissions from aircraft engines and APUs, data on other sources varies in quality and availability, and only limited data are available on ambient PM around airports. Newly tightened ambient air quality standards and greater health and environmental concerns present hurdles for airports as they need to modernize and expand to meet the increasing demand for air transportation. Yet airports represent only one PM emission source category among many in a region. In addition to complying with general conformity require- ments and assisting states in complying with national ambi- ent air quality standards, airports must address complaints from communities and employees who are concerned about health impacts resulting from exposure to airport emissions. Many airports also receive complaints about deposits of soot, grit, and the oily residue that airport neighbors find on their cars and outdoor furniture, which the complainants believe must come from airport activity. Several airports have conducted particle deposition stud- ies in nearby and adjacent communities to evaluate whether 9 10 AP-42, http://www.epa.gov/ttn/chief/ap42/index.html. 11 ICAO Aircraft Engine Emissions Data Bank http://www.caa.co.uk/ default.aspx? catid=702&pagetype=90.

airport activity is responsible for the deposition of concern to the citizens. Deposition studies have been conducted near Los Angeles International Airport, T.F. Green Airport (Providence, R.I.), Boston Logan International Airport, Charlotte/Douglas International Airport, Detroit Metropol- itan Wayne County International Airport, John Wayne- Orange County Airport, Seattle-Tacoma International Airport, Ft. Lauderdale-Hollywood International Airport, and Chicago O’Hare International Airport. None of these studies have shown a definitive link between the airports and the deposited material. These studies commonly find the deposits are typical of the material found throughout urban areas that come from diesel trucks, construction activity, wind-blown dust, pollen, and mold. This is perhaps not un- expected since the PM from aircraft and APUs is comprised of fine or ultrafine particles, which are too small to settle gravitationally or to be deposited by impacting stationary surfaces and remain suspended in the atmosphere. These studies are not conclusive, however, since they used differ- ent methodologies and many only sampled dry deposition and did not collect material deposited through rainfall, which is a primary mechanism for scrubbing suspended particles from the atmosphere. Future deposition studies will be able to build both on these findings and on new information coming from aircraft PM research to improve our understanding of the contribution of airport emissions to deposited PM. As noted earlier, little was known about aircraft PM emis- sions until recently when several federally funded research programs were conducted. To date, a great deal is known about a few engines with no testing done on most of the engine models in the fleet. The research results are still being analyzed to better understand PM formation in aircraft en- gines and its evolution in the plume. Even for those engines studied, more testing will be required to gain the data needed to develop emission factors with the same level of confidence as for emission factors used for other emission sources, which can relate operating conditions to final state PM emissions. With regard to GSE, EPA has taken steps to reduce PM emissions from nonroad vehicles. In response to national environmental regulations, refiners will begin producing low- sulfur diesel fuel for use in locomotives, ships, and nonroad equipment, which includes GSE. Low-sulfur diesel fuel must meet a 500 parts per million (ppm) sulfur maximum. This is the first step of EPA’s nonroad diesel rule, with an eventual goal of reducing the sulfur level of fuel for these engines to meet an ultra-low standard (15 ppm) to enable new advanced emission-control technologies for engines used in locomo- tives, ships, and other nonroad equipment. These most recent nonroad engine and fuel regulations complement similarly stringent regulations for diesel highway trucks and buses and highway diesel fuel for 2007. Beginning June 1, 2006, refiners began producing clean ultra-low sulfur diesel fuel, with a sulfur level at or below 15 parts per million (ppm), for use in highway diesel engines. Low-sulfur (500 ppm) diesel fuel for nonroad diesel engines will be required in 2007, followed by ultra-low sulfur diesel fuel for these vehicles in 2010.12 Stringent emissions standards for new GSE will be phased in between 2008 and 2014 as part of this rule. Whether and when similar reductions in fuel sulfur content will occur in aviation jet fuel has yet to be determined. What Tools are Available for Evaluating PM Emissions at Airports? As noted earlier, airport emissions are analyzed by apply- ing emission factors (drawn from emissions testing data of representative sources) to airport-specific operational data for various emission sources. All sources are then combined into an “emissions inventory.” Inventories are usually represented in mass emissions per unit of time (e.g., lbs/day or tons/year). Inventories are typically compiled for criteria pollutants and their precursors (i.e., NOx, SOx, CO, VOC, and PM). Various analytical tools are available to support these complex computations and aid in analyzing the results. Emissions and Dispersion Modeling System13 The Emissions and Dispersion Modeling System (EDMS) is used to assess air quality at civilian airports and military air bases. The model was developed by FAA in cooperation with the United States Air Force (USAF) and is used to produce an inventory of emissions generated by sources on and around the airport or air base, and to calculate pollutant concentra- tions in these environments. Particulate matter emissions are computed for aircraft main engines in EDMS version 5.0.2 by applying the First Order Approximation version 3.0a, where smoke number data are available. Particulate matter emissions for on-road vehicles are computed using the MOBILE model, described below. Similarly, PM emissions for GSE are computed using the NONROAD model. EDMS also contains a database of PM emission factors for stationary sources that are commonly found at airports. No data currently exist for modeling PM from aircraft auxiliary power units (APU). 10 12 Environmental Protection Agency Clean Air Nonroad Diesel – Tier 4 Final Rule, http://www.epa.gov/nonroad-diesel/2004fr.htm. 13 Emissions and Dispersion Modeling System Homepage http://www.faa.gov/ about/office_org/headquarters_offices/aep/models/edms_model/.

MOBILE14 As mentioned above, EDMS uses the EPA-developed MOBILE model (version 6.2 is included with EDMS 5.0.2) to compute emission factors for on-road vehicles. MOBILE allows the user to model emission factors for a fleet of vehicle types or an individual vehicle class based on the mix of vehi- cle types and age, and considers vehicle speed and ambient meteorological conditions as well. NONROAD15 Similar to MOBILE, EPA’s NONROAD model provides emission factors for ground support equipment at airports that consider the rated horsepower of the engine, fuel type, and the load factor. The traditional application of the model is to use the embedded database of county-level nonroad fleet information; however, the EPA extracted the underlying vehicle data for use in EDMS to allow the emissions for indi- vidual vehicles to be computed. First Order Approximation 3.0a16 First Order Approximation 3.0 (FOA3) is being developed by the ICAO Committee for Aviation Environmental Protection (CAEP) Working Group 3 to estimate PM emissions from com- mercial aircraft engines in the absence of acceptable data or emis- sion factors. Data from the APEX aircraft engine emission tests are being used in its development. FOA3 models three compo- nents of PM using the sum of three separate equations: a power and polynomial function of smoke number for nonvolatile PM, a constant for SO4, and a function of HC emission indices for fuel organics. EDMS uses the FOA3a methodology for U.S airports, which includes additional reasonable margins to accommodate uncertainties. FOA3a adapts the FOA3 equations to be more conservative in the calculation of SO4 and fuel organics while keeping the equations the same for nonvolatile PM. Aviation Environmental Design Tool17 The Aviation Environmental Design Tool (AEDT), presently under development and testing, is designed to incor- porate and harmonize the existing capabilities of the FAA to model and analyze noise and emissions. Building on current tools, including EDMS, common modules and databases will allow local and global analyses to be completed consistently and with a single tool. With this tool, users will be able to ana- lyze both current and future scenarios to understand how avi- ation effects the environment through noise and emissions on a local and global scale. Aviation Environmental Portfolio Management Tool18 The Aviation Environmental Portfolio Management Tool (APMT) is currently being developed by the FAA as a compo- nent of AEDT to allow tradeoffs between noise and emissions to be better understood. The tool has three primary capabili- ties: (1) cost-effectiveness analysis, (2) benefit cost analysis, and (3) distributional analysis. The “costs” and “benefits” are computed at a societal level by considering economic and health effects. Community Multiscale Air Quality Model19 The Community Multiscale Air Quality Model (CMAQ) was developed through a NOAA-EPA partnership and allows the analyst to model a variety of air quality effects, including: tropospheric ozone, toxics, acid deposition, and visibility degradation. This is accomplished by including robust modeling of the atmospheric physics and chemical re- actions. The scale of the model is variable with grid sizes ranging from less than 4 km to over 36 km depending on the needs of the analysis. Microphysical Models Microphysical models refer to a class of atmospheric mod- els intended to predict cloud formations based on the forma- tion and size of droplets and the nucleation of particles. The same techniques used to predict water-based clouds in the sky can be applied toward predicting the formation of plumes of aerosols and particulate matter. Microphysical modeling has been used to model aviation PM evolution both at altitude and at ground level. 11 14 MOBILE 6 Homepage http://www.epa.gov/otaq/m6.htm. 15 NONROAD Homepage http://www.epa.gov/otaq/nonrdmdl.htm. 16 Kinsey, J., Wayson, R.L, EPAct PM Methodology Discussion Paper (2007). 17 Federal Aviation Administration, Office of the Environment and Energy AEDT News, (1:1), September 2007. 18 Aviation Environmental Portfolio Management Tool (APMT) Prototype http:// www.faa.gov/about/office_org/headquarters_offices/aep/models/ history/media/2006-02_CAEP7-WG2-TG2-6_IP02_APMT_Prototype.pdf . 19 CMAQ Homepage http://www.epa.gov/asmdnerl/CMAQ/cmaq_model.html.

Next: Chapter 4 - Survey and Interview Findings »
Research Needs Associated with Particulate Emissions at Airports Get This Book
×
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

TRB’s Airport Cooperative Research Program (ACRP) Report 6: Research Needs Associated with Particulate Emissions at Airports examines the state of industry research on aviation-related particulate matter emissions and explores knowledge gaps that existing research has not yet bridged.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  6. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  7. ×

    View our suggested citation for this chapter.

    « Back Next »
  8. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!