Formulations for Aircraft and Airfield Deicing and Anti-Icing: Aquatic Toxicity and Biochemical Oxygen Demand (2009)

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IV EXECUTIVE SUMMARY The Airport Cooperative Research Program (ACRP) has sponsored research on environmental characteristics of aircraft and pavement deicers and anti-icers focusing primarily on biochemical oxygen demand (BOD) and aquatic toxicity of formulated products and individual chemical components of formulations. This report presents a background of issues leading to this research, objectives of this document, and a description of the efforts and findings of this research. Except when the distinction among products is necessary for clarity, “deicer” will refer to aircraft-deicing fluids (ADFs), aircraft anti-icing fluids (AAFs), and pavement-deicing materials (PDMs) generally. Literature and Data Review An extensive library of policy documents, patent literature, professional literature, project reports, and other data was compiled and reviewed as well as a collection of deicer manufacturer literature. This extensive review provided a base of information to help define the current state of public knowledge regarding deicers. Federal Aviation Administration and Society of Automotive Engineers Policies Regarding Toxicity and Biochemical Oxygen Demand in Deicers The Society of Automotive Engineers (SAE) develops and issues the standards for aircraft and pavement deicing materials. The Federal Aviation Administration (FAA) recommends these specifications in Advisory Circulars. SAE provides the only numerical limits related to environmental characteristics, through AMS 1424, which requires Type I fluids to have 50 percent lethal concentrations (LC50s) greater than or equal to 4,000 mg/L for several organisms.1 No guidance is provided for the BOD content of deicers. Characterization of Components in Commercial Deicer Products A wide range of chemicals potentially used in deicers was identified in the literature, including 25 freezing point depressants (FPDs), 21 surfactants, 11 corrosion inhibitors, 13 thickening agents, six defoamers, nine pH modifiers, five dyes, four oils, and four antioxidants and antimicrobial agents. Not all of these component categories are present in all deicing products; thickeners, for example, are found only in aircraft anti-icing products. Toxicity data were available for less than one third of these chemicals, and the available data were not always comparable among different chemicals or relevant to deicing situations. It was therefore concluded that further testing will be needed to define the toxicity of individual candidate deicer components. 1 LC50 is the highest concentration at which 50 percent of the tested organisms do not survive the test period.

V Deicer manufacturers are constantly considering modifications to their products to improve performance, environmental characteristics, and cost. Nearly all Type I ADFs now meet SAE specifications for toxicity, BOD characteristics of PDM have been improved, four manufacturers have introduced new Type IV formulations in the 2007–2008 winter season, and one manufacturer ha introduced a new Type I formulation for the 2008-2009 winter season with assertions that these formulations would be more environmentally friendly than previously available products. Characteristics of Deicers in the Environment The primary environmental concerns with deicers are high organic content, resulting in high BOD, and aquatic toxicity. Some fate and transport characteristics of deicers are understood, but many others have not been studied as extensively. Most research on the fate and transport of deicers has focused on freezing point depressants (FPDs) and, to a lesser extent, on benzotriazole-derived corrosion inhibitors and alkyphenol ethoxylate (APE) surfactants. The components whose environmental characteristics are not well understood include dyes, thickeners, pH modifiers, defoamers, other corrosion inhibitors and surfactants, and even the FPDs used in pavement deicer products. Degradation rates of FPDs are dependent on environmental factors such as medium, temperature, travel time, and established bacterial communities in soils and receiving waters. Benzotriazoles and APEs have been studied at a small number of airports, but the bulk of research on APEs has been in wastewater treatment and not in situations where these surfactants are released directly to receiving waters without being treated. Benzotriazoles stay mostly in solution but have been detected in soils near deicing activities. Benzotriazoles have proven to degrade slowly or not at all in the environment. Of several different pathways, some APE degradation products are more toxic than thei parent compounds, express endocrine disruption potential, and have potential for sorption to sediment particles and persistence in benthic sediments. Assessing the aquatic toxicity of deicers is a complicated issue owing to several different factors. First, toxicity in ADF and AAF is due primarily to proprietary additives, and the chemical identities of most of these additives are treated by the manufacturers as confidential business information. Second, different formulations have different degrees of toxicity, so different effluents with similar glycol concentrations may have very different levels of toxicity. Third, different ADF and AAF formulations have different concentrations of glycol, again posing complications to interpreting chemical analysis from effluent samples. Last, the fate and transport characteristics of additives are not necessarily the same as those of glycol, so glycol and glycol surrogates such as chemical oxygen demand (COD) and BOD cannot be used as reliable indicators of additive content in effluents. Conclusions from current literature indicate that research is necessary to better understand toxicity in ADF and AAF formulations and deicer runoff; however, available data indicate that the most likely sources of toxicity in PDM are the FPDs. Characteristics of Deicers in Wastewater Treatment Systems The most commonly used FPDs (propylene glycol, ethylene glycol, acetate, and formate) are readily biodegradable under both aerobic and anaerobic methanogenic conditions. Because

VI of the ease by which the FPDs can be biodegraded, their primary impact on biological treatment systems is increased organic load. Available literature indicates that nonylphenol ethoxylates (NPEs) may be degraded through biological treatment, but reported details on degradation and byproduct generation vary depending on the specific literature. Triazoles are unlikely to be completely biodegraded in typical biological treatment systems. In sufficient concentration, they have been shown to inhibit degradation of other organic compounds, thereby decreasing treatment effectiveness of spent deicers. Recent research indicates that different treatment strategies have varying effectiveness, with conventional activated sludge the least effective, membrane bioreactors more effective, and ozonation resulting in complete mineralization of benzotriazole and 4- and 5-methyl-1H benzotriazole. Operational and Infrastructure Considerations Potential impacts on aircraft operations and infrastructure were identified in the literature. Potassium formate– and potassium acetate–based PDMs have been identified as potential contributors to corrosion of cadmium-plated electrical connectors in the Boeing 737 New Generation aircraft and to accelerated catalytic oxidation of carbon composite brake components. In both cases, potassium-based PDMs were in widespread use prior to material changes in the newer aircraft involved. Changes to components and maintenance procedures, including Boeing’s recommended practice to eliminate cadmium corrosion through the use of corrosion-inhibiting compound (CIC) on electrical connectors, have eliminated or minimized the corrosion reactions. SAE G-12 and aircraft manufacturers have specific task groups working on these important issues. Increased failure rates of airfield electrical components were also thought to be linked to potassium acetate PDM. It was subsequently found that poorly maintained systems allowed entry of PDMs. Corrective actions and improved products and components have greatly reduced or eliminated the problems. Reports of pavement deterioration, including degradation and disintegration of asphalt pavements, softening and stripping effects on bitumen and asphalt concrete, and scaling and surface cracking were determined to be a result of alkali-silica reactivity linked to potassium-based pavement deicing and anti-icing formulation (PDF). It was subsequently determined that other factors, especially construction methods and materials, can be used to mitigate these issues. Residues from Type II and Type IV fluids may form on aerodynamically quiet areas, and if not removed by deicing or anti-icing, the residue may absorb rainwater (rehydrate) and subsequently freeze, restricting the movement of unpowered flight control surfaces. Deicer Products under Development During the past 10 years, there have been a number of efforts to develop more environmentally friendly deicers. Some of these new products are entering the market, while others are not yet available commercially. Octagon Process, Inc. has introduced a propylene glycol/glycerol-based Type I ADF that is described as having lower BOD5 and aquatic toxicity compared to many previous Type I formulations. Battelle has recently released an ADF–AAF and a PDF, both based on glycerol as the primary FPD. Battelle is

VII also working on alternative PDF formulations that are less damaging to aircraft components and less expensive than current PDMs. Foster-Miller has previously developed two Type I fluids and one Type II fluid, with the objective of producing environmentally advantaged formulations that consider BOD and toxicity. METSS has developed two versions of Type I fluid using agriculturally based products that were intended to be favorable regarding toxicity and BOD issues. Even though some of these formulations have been certified according to SAE standards, problems involving residue formation, foaming, or unfavorable thickening after application have been encountered during field testing. The prospects for near-term commercial availability of these products are unclear. Methodological Issues A number of methodological issues were identified in the literature review. Biochemical Oxygen Demand Standard 5-day BOD (BOD5) testing as well as extended length BOD testing pose unique challenges in samples containing deicers. Issues include determining proper dilutions to characterize BOD accurately, properly acclimating microorganisms, and having seeds with insufficient microorganism densities. Analysis of Additives Standard techniques are not in place for determining deicer additives such as benzotriazoles and APEs. These techniques are currently in flux, necessitating regular review of literature to evaluate the most current methods. Aquatic Toxicity Acute deicer toxicity test results in low-temperature tests were not dramatically different from those in standard temperatures, with C. dubia slightly less sensitive to deicers at lower temperatures and fathead minnows slightly more sensitive to deicers at lower temperatures. One complication when conducting toxicity tests with samples containing deicer is low dissolved oxygen (DO) resulting from high BOD. A successful method for improving DO levels during fathead minnow tests is to reduce the number of fish per replicate and reduce the sample volume. Representativeness of Laboratory Analyses Results of BOD and toxicity tests performed in a laboratory under controlled light and temperature conditions provide valuable ecological information, but such conditions do not mimic environmental conditions, especially during deicer application events. Toxicity Characterization Baseline toxicity tests were conducted on seven Type I formulations, four Type IV formulations, and three PDMs. One group of five Type I products resulted in LC50s averaging about 10,000 mg/L, whereas two products showed LC50s near 30,000 mg/L. Type IV deicer products consistently demonstrated much greater toxicity than the Type I products, with LC50s near 2,500 mg/L and lower. Toxicity results with marine species were similar to those with freshwater test species. Toxicity in fractionated Type IV and Type I deicer products was associated with the presence of polyethoxylated nonionic surfactants, including both APE surfactants and aliphatic alcohol ethoxylate surfactants. Relatively high concentrations of triazole-based corrosion inhibitors in one Type IV deicer triggered toxicity in toxicity identification and evaluation (TIE) assays. Toxicity in pavement deicers is associated primarily with the FPDs.

VIII Four manufacturers introduced new Type IV formulations for the 2007–2008 winter season, one manufacturer introduced a new Type I formulation and one manufacturer introduced a new PDM for the 2008-2009 winter season with claims that these formulations would be more environmentally friendly than past AAF formulations. Research on these formulations is not included in this toxicity analysis. Biochemical Oxygen Demand and Chemical Oxygen Demand BOD and COD were characterized in seven deicer formulations, including ethylene glycol and propylene glycol formulations of Type I ADF, ethylene glycol and propylene glycol formulations of Type IV AAF, a potassium acetate–based liquid PDM, and sodium acetate– and sodium formate–based solid PDMs. Expanded testing was conducted on one formulation of propylene glycol Type I ADF, one propylene glycol Type IV AAF, and one potassium acetate PDF to determine decay rates over a 40-day period at 20°C and 5°C in marine water and freshwater. BOD5 and COD results are presented in Table ES-1. Biodegradability was examined by comparing BOD and COD results. The degradation percentage was between 40 and 82 percent for six of the formulations. Decay rates in the 40- day test indicate that degradation occurred more rapidly within the first 15 days than during the rest of the test period. At least 78 percent degradation was exerted for the six formulations over the 40-day test period. Results from sodium formate PDM testing are not included owing to apparent toxicity of this formulation to organisms in the BOD seed. Freshwater and marine water test results were comparable in the 40-day tests conducted at 20°C. Results of the 40-day freshwater tests at 5°C indicate lower degradation than those at 20°C with 23–55 percent degradation for ethylene glycol products, 61–77 percent degradation for propylene glycol products, and 86–94 percent for acetate-based products. Results of the 5°C marine tests indicated that degradation was significantly less in low TABLE ES-1 Summary of BOD5 and COD Results for Tested Deicers Values as Neat Formulation Values as Primary Source of Oxygen Demand Formulation % FPD COD (mg/kg) BOD5 (mg/kg) Primary Source COD (mg/kg) BOD5 (mg/kg) Ethylene glycol Type I 92 1,180,000 492,000 EG 1,280,000 535,000 Ethylene glycol Type IV 64 826,000 331,000 EG 1,290,000 517,000 Propylene glycol Type I 88 1,420,000 990,000 PG 1,610,000 1,130,000 Propylene glycol Type IV 50 842,000 539,000 PG 1,680,000 1,080,000 Potassium acetate (liquid) 50 315,000 247,000 Acetate 1,050,000 821,000 Sodium acetate (solid) 96 700,000 571,000 Acetate 1,010,000 826,000 Sodium formate (solid) 98 242,000 —a Formate 373,000 —a a BOD test results for sodium formate deicer were not considered reliable estimates of potential BOD exertion in environmental situations due to apparent toxicity of the formulation to BOD seed organisms.

IX temperatures with the propylene glycol ADF and AAF exerting less than 10 percent degradation, and the potassium acetate PDM exerting 69 percent degradation.

X CONTENTS Executive Summary .......................................................................................................................... iv Acknowledgments .......................................................................................................................... xiv Acronyms and Abbreviations......................................................................................................xvii 1 Introduction............................................................................................................................... 1-1 Background ................................................................................................................................ 1-1 Objectives.................................................................................................................................... 1-2 Report Structure......................................................................................................................... 1-3 2 Literature and Data Review.................................................................................................... 2-1 FAA and SAE Policies Regarding Toxicity and BOD in Deicers ........................................ 2-1 Requirements, Guidance, and Standards Regarding Toxicity and BOD .................... 2-1 Characterization of Components in Commercial Deicer Products .................................... 2-2 Deicing and Anti-icing Products ...................................................................................... 2-2 Knowledge and Data Gaps.............................................................................................. 2-10 Characteristics of Deicers in the Environment .................................................................... 2-10 Environmental Information from Manufacturer Literature ....................................... 2-10 Fate and Transport of Deicers ......................................................................................... 2-14 Biochemical Oxygen Demand......................................................................................... 2-17 Dissolved Oxygen ............................................................................................................. 2-17 Bacterial Growth ............................................................................................................... 2-17 Odors .................................................................................................................................. 2-18 Aquatic Toxicity ................................................................................................................ 2-19 Emerging Pollutants ......................................................................................................... 2-21 Recent Improvements in Environmental Characteristics............................................ 2-22 Knowledge and Data Gaps.............................................................................................. 2-22 Characteristics of Deicers in Wastewater Treatment Systems .......................................... 2-23 Knowledge and Data Gaps.............................................................................................. 2-24 Operational and Infrastructure Considerations.................................................................. 2-24 Pavement Deterioration ................................................................................................... 2-24 Airfield Electrical Systems............................................................................................... 2-25 Cadmium Corrosion......................................................................................................... 2-25 Carbon-Carbon Brake System Oxidation ...................................................................... 2-25 Residuals ............................................................................................................................ 2-26 Knowledge and Data Gaps.............................................................................................. 2-27 Deicer Products under Development ................................................................................... 2-27 Battelle D3 .......................................................................................................................... 2-27 Foster-Miller Low-BOD Fluid ......................................................................................... 2-28 METSS Type I .................................................................................................................... 2-28 Knowledge and Data Gaps.............................................................................................. 2-29 Methodological Issues ............................................................................................................ 2-29 BOD Analysis .................................................................................................................... 2-29

XI Benzotriazoles Analysis....................................................................................................2-30 Alkylphenol Ethoxylates Analysis..................................................................................2-32 Toxicity Test Methods.......................................................................................................2-34 Operational Characteristics Testing................................................................................2-34 3 Aircraft and Airfield Deicing Formulations Components Assessment .........................3-1 Toxicity Assessment ..................................................................................................................3-1 Methods ................................................................................................................................3-3 Results .................................................................................................................................3-12 Discussion and Synthesis of Results ...............................................................................3-33 Biochemical Oxygen Demand................................................................................................3-35 Introduction........................................................................................................................3-35 Methods ..............................................................................................................................3-35 Seed Inoculums..................................................................................................................3-36 Results .................................................................................................................................3-37 4 Conclusions................................................................................................................................4-1 Literature and Data Review......................................................................................................4-1 Airfield and Aircraft Components Assessment.....................................................................4-2 Toxicity..................................................................................................................................4-2 Oxygen Demand..................................................................................................................4-2 5 References ..................................................................................................................................5-1 Tables ES-1 Summary of BOD5 and COD Results for Tested Deicers ................................................ viiii 2-1 Summary of SAE Environmental Testing Standards for Deicers ....................................2-2 2-2 Freezing Point Depressants...................................................................................................2-3 2-3 Surfactants ...............................................................................................................................2-4 2-4 Corrosion Inhibitors ...............................................................................................................2-5 2-5 Thickening Agents..................................................................................................................2-6 2-6 Defoamers ................................................................................................................................2-6 2-7 pH Modifiers ...........................................................................................................................2-7 2-8 Dyes ..........................................................................................................................................2-7 2-9 Oils Used as Hydrophobic Agents.......................................................................................2-8 2-10 Antioxidant and Antimicrobial Agents...............................................................................2-8 2-11 Toxicity Values of Commercial Components as Reported in the ECOTOX Database...................................................................................................................................2-8 2-12 Summary of Available Information Regarding the Environmental Characteristics of Aircraft Deicing and Anti-icing Fluids..............................................................................2-11 2-13 Summary of Available Information Regarding the Environmental Characteristics of Pavement Deicing and Anti-icing Fluids ..........................................................................2-12 2-14 Examples of Recent Triazole Extraction and Analysis Methods ...................................2-30 2-15 Examples of Recent APEO Analysis Methods..................................................................2-32 2-16 Standards for Aircraft and Runway Deicing/Anti-icing Fluids and Runway Solids ......................................................................................................................................2-35 2-17 AMS Requirements for the Most Common Aircraft and Runway Deicing/Anti-icing Liquids ...................................................................................................................................2-35

XII 3-1 Summary of Deicer Product Candidates Considered for Inclusion in Toxicity Assays and TIE..................................................................................................................................... 3-3 3-2 Summary of Toxicity Results from GPC/HPLC Fractionation of Type IV Deicer Products................................................................................................................................. 3-18 3-3 Summary of Major Chemical Components Identified in Toxic GPC/HPLC Fractions Isolated from Type IV Deicer Products............................................................................. 3-20 3-4 Contribution of High Molecular Weight (>10,000 MWCO) Components to Toxicity of Type IV Deicer Products ..................................................................................................... 3-21 3-5 Summary of Toxicity Results from Distillation/HPLC Fractionation of Type I Deicer Products................................................................................................................................. 3-23 3-6 Summary of Major Chemical Components Identified in Toxic Distillation/HPLC Fractions Isolated from Type I Deicer Products .............................................................. 3-24 3-7 Summary of Surfactants Identified in Type I and Type IV Deicer Products by Q-TOF, MALDI, and LC-MS Mass Spectrometry Techniques..................................................... 3-25 3-8 Measured Concentrations (mg/L) of Triazoles in Deicer Products (mean ± SD; n = 3)....................................................................................................................................... 3-28 3-9 Toxicity of Mock Type IV Deicer Product H to Aquatic Species................................... 3-30 3-10 Toxicity of Mock Type IV Deicer Product I to Aquatic Species..................................... 3-31 3-11 Toxicity of Mock Type IV Deicer Product J to Aquatic Species..................................... 3-31 3-12 Toxicity of Mock Type IV Deicer Product K to Aquatic Species ................................... 3-32 3-13 Toxicity of Selected Deicer Components Used in Mock Formulations ........................ 3-32 3-14 COD and BOD5 for Selected Aircraft and Airfield Deicers and Anti-icers .................. 3-38 3-15 Biodegradation of Aircraft and Pavement Deicers and Anti-icers at 20°C and 5°C with Measurements at 5, 15, 28, and 40 Days .................................................................. 3-39 3-16 Biodegradation of Aircraft and Pavement Deicers and Anti-icers at 20°C and 5°C with Measurements at 5, 15, 28, and 40 Days Presented as Concentration of Primary Source of Oxygen Demand.............................................................................................................. 3-42 3-17 First-Order Decay Rate Constants Computed from 40-Day Biochemical Oxygen Demand Testing with Aircraft and Pavement Deicing and Anti-icing Formulations......................................................................................................................... 3-51 Figures 3-1 Scheme for conducting toxicity identification and evaluation assays on deicer products................................................................................................................................... 3-2 3-2 Fractionation scheme for separating Type IV deicer products prior to toxicity assays and analytical characterization. ........................................................................................... 3-6 3-3 Fractionation scheme for separating Type I deicer products prior to toxicity assays and analytical characterization. ................................................................................................... 3-8 3-4 Acute test lethal concentrations (LC50s) for Type I deicer products for Microtox and four regulatory species tested. ........................................................................................... 3-13 3-5 Acute test lethal concentrations (LC50s) for Type IV deicer products for Microtox and four regulatory species tested. ........................................................................................... 3-13 3-6 Acute toxicity test lethal concentrations (LC50s) for pavement deicer products for Microtox and four regulatory species tested.................................................................... 3-14

XIII 3-7 Chronic test lethal concentrations (IC25s) for Type I deicer products for three regulatory species tested. ....................................................................................................3-15 3-8 Chronic test lethal concentrations (IC25s) for Type IV deicer products for three regulatory species tested. ....................................................................................................3-16 3-9 Chronic test lethal concentrations (IC25s) for pavement deicer products for three regulatory species tested. ....................................................................................................3-16 3-10 Concentration (mg/L) of Individual APE Surfactant Ethoxymers (Ethoxy-Chain Lengths 1–17) in Product K and Product I (Type IV Deicers). .......................................3-27 3-11 Comparison of 5-day BOD results obtained using the traditional BOD5 and modified 40-day time-series methods.................................................................................................3-44 3-12 Percent biodegradation of selected aircraft and airfield deicers and anti-icers based on 5-Day BOD-to-COD ratios...................................................................................................3-45 3-13 Percent biodegradation of selected aircraft and airfield deicers and anti-icers at 20°C in freshwater based on a 40-day BOD time series as compared to COD values..............3-46 3-14 Percent biodegradation of selected aircraft and airfield deicers and anti-icers at 20°C in marine water based on a 40-day BOD time series as compared to COD values .........3-46 3-15 Percent biodegradation of selected aircraft and airfield deicers and anti-icers at 5°C in freshwater based on a 40-day BOD time series as compared to COD values..............3-48 3-16 Percent biodegradation of selected aircraft and airfield deicers and anti-icers at 5°C in marine water based on a 40-day BOD time series as compared to COD values .........3-49 3-17 Inhibitory effect of sodium formate deicer on the BOD5 test results............................3-50

XIV ACKNOWLEDGMENTS The ACRP 02-01 Project Team consists of University of South Carolina, U.S. Geological Survey, Wisconsin State Laboratory of Hygiene, Molecular Knowledge Systems Inc., Infoscitex Corporation, CH2M HILL, and Western Washington University. The project team would like to thank the members of the Project Panel for providing the opportunity to work on this project. We would also like to thank all those who provided valuable information for this report. Authors Lee Ferguson, Ph.D. University of South Carolina Steven R. Corsi U.S. Geological Survey Steven W. Geis Wisconsin State Laboratory of Hygiene Graham Anderson Wisconsin State Laboratory of Hygiene Kevin Joback, Ph.D. Molecular Knowledge Systems Inc. Harris Gold, Ph.D. Infoscitex Corporation Dean Mericas, Ph.D. CH2M HILL Devon A. Cancilla, Ph.D. Western Washington University Technical Analysts Amy Mager Wisconsin State Laboratory of Hygiene Mike Manix Wisconsin State Laboratory of Hygiene

XV Project Panel Susan Aha, Chair Port of Portland, Oregon Edward T. Harrigan, CRP Staff Representative Senior Program Officer Transportation Research Board Charlotte Thomas, ACRP Staff Representative Senior Program Assistant Transportation Research Board Jessica Baird, Member Sr. Environmental Advisor Transport Canada Kevin B. Bleach, Member Manager, Aeronautical and Tech Services Port Authority of New York and New Jersey Satya P. Chauhan, Member Battelle Memorial Institute (Battelle) Roy Fuhrmann, Member Airport Environmental Manager Minneapolis St Paul Metropolitan Airports Commission John Wheeler, Member Airport Environmental Manager City of Des Moines Department of Aviation Darcy C.Z. Zarubiak, Member Senior Consultant Leigh Fisher Associates Christine Gerencher, Liaison Representative Senior Program Officer Transportation Research Board Paul Friedman, ACRP Project Officer Federal Aviation Administration George I. Legarreta, Liaison Representative Federal Aviation Administration Jessica Steinhilber, Liaison Representative Airports Council International-North America (ACI-NA) Keith Johnson, Interested observer Cryotech Deicing Technology, Inc.

XVI Jacque Leroux, Interested observer Dow Chemical Canada Tim A. Pohle, Interested observer Air Transport Association of America, Inc.

XVII ACRONYMS AND ABBREVIATIONS µg/L micrograms per liter µL microliter µM micromolar AAF aircraft anti-icing fluid ACRP Airport Cooperative Research Program AD Airworthiness Directive ADF aircraft-deicing fluid AMS Aerospace Material Specification APE alkylphenol ethoxylate APHA American Public Health Association ASR alkali-silica reactivity ASTM American Society for Testing and Materials ATR attenuated total reflectance BOD biochemical oxygen demand BOD5 5-day biochemical oxygen demand BT benzotriazole CaCl2 calcium chloride CAS # Chemical Abstracts Service registry number CIC corrosion-inhibiting compound COD chemical oxygen demand DO dissolved oxygen EC50 half maximal effective concentration EG ethylene glycol EO ethoxymer EPA U.S. Environmental Protection Agency ESTCP Environmental Security Technology Certification Program FAA Federal Aviation Administration FID flame ionization detector FPD freeze-point depressant FTIR Fourier transform infrared GC/MS gas chromatography/mass spectrometry GMIA General Mitchell International Airport (Milwaukee, WI) GPC gel permeation chromatography HPLC high-pressure liquid chromatography

XVIII IC25 25 percent inhibition concentration ISO International Standards Organization kDa kilodalton KgO2/Kg kilogram of oxygen per kilogram of product L liter LC50 50 percent lethal concentration LC/MS/MS liquid chromatography–tandem mass spectrometry LRU line replaceable unit mg/L milligrams per liter mm millimeter MS/MS tandem mass spectrometry MWCO molecular weight cut-off ng/L nanogram per liter NMR nuclear magnetic resonance NP nonylphenol NPE nonylphenol ethoxylates OP octylphenol OPE octylphenol ethoxylates PDF pavement deicer and anti-icer formulation PDM pavement-deicing material PG propylene glycol Q-TOF quadropole time of flight SAE Society of Automotive Engineers SERDP Strategic Environmental Research and Development Program SPE solid phase extraction THF tetrahydrofuran TIE toxicity identification and evaluation TMDL total maximum daily load TOC total organic carbon TOD total oxygen demand TT tolyltriazole UV ultraviolet UV-VIS UV-visible spectrophotometry XC MAS cross-coiled magnetic angle spinning