Formulations for Aircraft and Airfield Deicing and Anti-Icing: Aquatic Toxicity and Biochemical Oxygen Demand (2009) / Chapter Skim
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From page 41... ...
3-1 SECTION 3 AIRCRAFT AND AIRFIELD DEICING FORMULATIONS COMPONENTS ASSESSMENT Laboratory analyses were conducted to characterize two critical aspects of currently used deicers: aquatic toxicity and BOD. This section describes the analytical methods employed and the results of those analyses.
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3-2 Figure 3-1. Scheme for conducting toxicity identification and evaluation assays on deicer products.
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3-3 Methods Baseline Toxicity Testing Before beginning work on the TIE process, a total of 14 deicer products (Table 3-1) were screened for toxicity using Microtox and common aquatic regulatory species, including the fathead minnow (Pimephales promelas)
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3-4 replicates and test organisms were used, test solutions were not renewed, and water quality parameters were not monitored. One deicer product from each category was selected for acute marine toxicity testing using the marine species mysid shrimp (Mysidopsis bahia)
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3-5 microcentrifuge tubes. The tubes were mixed on a vortex mixer then centrifuged at 14,500 rpm for 5 min.
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3-6 Figure 3-2. Fractionation scheme for separating Type IV deicer products prior to toxicity assays and analytical characterization.
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3-7 This fractionation scheme was used to separate all four Type IV deicer products into 15 GPC/HPLC fractions plus one additional fraction of polymeric thickener (isolated by precipitation and resuspended in a minimal volume of nanopure water)
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3-8 Figure 3-3. Fractionation scheme for separating Type I deicer products prior to toxicity assays and analytical characterization.
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3-9 for toxicity testing, and the remaining 200 µL of each fraction was reserved for chemical analysis. Toxicity Assays of Deicer Fractions The toxicity of fractions of deicer formulations prepared as described above was characterized using the fathead minnow, C
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3-10 The polymeric thickener components of the Type IV deicers were characterized using Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR)
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3-11 ramped to 0 percent B from 32.7 min to 38 min and held at 0 percent B for 2 min. Initial conditions were returned (50 percent B)
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3-12 Results Baseline Acute Toxicity Testing Five Type I products were assayed to generate LC50s for regulatory species (Figure 3-4)
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3-13 Figure 3-4. Acute test lethal concentrations (LC50s)
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3-14 Figure 3-6. Acute toxicity test lethal concentrations (LC50s)
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3-15 Figure 3-7. Chronic test lethal concentrations (IC25s)
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3-16 Figure 3-8. Chronic test lethal concentrations (IC25s)
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3-17 Type IV Deicer Products Initial TIE work focused on the Type IV deicer products because these were found to be the most toxic formulations (as described above)
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3-18 TABLE 3-2 Summary of Toxicity Results from GPC/HPLC Fractionation of Type IV Deicer Products Blank 1 Blank 2 Product K Product J Product I Product H Fraction* M C F M C F M C F M C F M C F M C F MeOH control 80 100 100 84 100 100 78 100 100 78 100 100 76 100 100 77 90 100 1 2 0 0 24 0 100 0 0 0 8 0 0 0 0 75 6 0 0 2 73 100 100 64 100 100 37 0 100 76 100 75 20 100 100 41 0 100 3 72 100 75 82 100 100 68 100 100 79 100 100 91 100 100 85 100 100 4 73 100 100 83 100 100 80 100 100 80 100 100 74 100 100 74 90 100 5 76 100 100 82 100 100 0 0 0 37 0 0 9 0 0 38 20 100 6 80 100 100 63 0 100 2 0 0 22 0 100 0 0 100 25 0 100 7 72 100 100 86 100 100 29 0 100 63 100 100 19 100 100 78 100 100 8 69 100 100 78 90 100 35 100 75 75 100 100 99 100 100 68 100 100 9 82 100 100 88 100 100 84 100 100 77 100 100 -- -- -- 84 100 100 10 79 100 100 89 40 100 61 0 0 82 100 100 86 100 100 29 20 75 11 0 0 0 0 0 0 0 0 0 1 0 0 0 0 100 4 0 0 12 25 0 100 33 0 100 41 0 100 59 70 100 15 100 100 77 100 100 13 78 100 100 35 80 100 80 100 100 79 100 100 137 100 100 77 100 100 14 75 100 100 81 100 100 56 100 100 75 100 100 108 100 100 79 90 75 15 64 100 100 84 100 100 46 100 75 78 100 100 113 100 100 79 100 100 Thickener -- -- -- -- -- -- 30 100 100 77 100 100 82 100 100 66 100 100 Values correspond to percent survival.
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3-19 Analyses of the toxic fractions identified in Table 3-2 were conducted by MS methods to identify major chemical components that may have contributed to the observed toxic effects. To this end, high-resolution electrospray quadrupole/TOF MS and MALDI-TOF MS were used to enable the most comprehensive qualitative analysis possible.
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3-20 TABLE 3-3 Summary of Major Chemical Components Identified in Toxic GPC/HPLC Fractions Isolated from Type IV Deicer Products Deicer Fraction No.a Compounds Identified in Fractionb 5 OPE 2-9,c NPE 4-24,c C16EO 3-6c 8 methyl-1H-benzotriazolec Product K 10 OPE 2-5 Product J 5 C10EO 5-16,c C12EO 2-19,c C14EO 2-17c Product I 5 NPE 2-18,c C13EO 15-19,c C16EO 3-13c 5 C12EO 5-19, C14EO 4-18 Product H 10 C12EO 2-6 a Fraction numbers correspond to those in Figure 3-2. b See text for chemical nomenclature.
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3-21 (Tables 3-2 and 3-3)
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3-22 was confirmed with toxicity results matching the expected LC50 of glycol (Figure 3-4) in three of the products (product C glycol fraction had a higher LC50 because it is a ready-touse, or diluted, product)
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3-23 TABLE 3-5 Summary of Toxicity Results from Distillation/HPLC Fractionation of Type I Deicer Products Blank Product A Product B Product C Product E Fractiona M C F M C F M C F M C F M C F Volatilesb n/a n/a n/a NT NT NT NT NT NT NT NT NT NT NT NT Glycolb n/a n/a n/a 42,000 44,000 47,000 50,000 36,000 23,000 >111,000 76,000 79,000 >64,000 45,000 64,000 Organic-solubleb n/a n/a n/a NT NT 67,000 NT NT NT NT NT 79,000 NT NT NT MeOH control 80 100 100 77 100 100 74 100 100 77 90 100 81 100 100 HPLC F1 66 100 100 88 100 100 86 0 100 79 100 75 81 90 100 F2 80 100 100 87 80 100 96 0 100 69 100 75 81 100 100 F3 67 100 100 76 100 100 82 0 100 42 70 100 73 100 100 F4 73 100 100 74 100 100 74 100 100 59 80 75 77 100 100 F5 76 100 100 68 100 75 70 100 100 74 100 100 78 100 100 F6 74 100 100 75 100 75 66 100 100 78 100 100 78 90 100 F7 71 100 100 77 100 100 67 100 100 80 100 100 72 100 100 F8 69 100 100 59 100 100 77 100 100 50 100 100 77 100 100 F9 76 100 100 71 100 100 66 90 75 70 80 100 47 60 25 F10 58 100 100 78 100 100 64 80 75 81 80 100 53 30 0 Fraction test concentrationsc 160,320 133,440 133,440 153,600 Values correspond to percent survival unless noted otherwise. Green cells represent non-toxic fractions, red cells indicate toxic fractions, and orange cells represent fractions exhibiting slight toxicity.
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3-24 TABLE 3-6 Summary of Major Chemical Components Identified in Toxic Distillation/HPLC Fractions Isolated from Type I Deicer Products Deicer Fractiona Compounds Identified in Fractionb Product A Organic soluble C10EO 5-16 C12EO 5-12 Product B 10 C10EO 5-16 C12EO 5-16 Product C Organic soluble C13EO 9-15 C14EO 9-20 C15EO 8-23 C16EO 8-22 Product E 9, 10 C12EO 6-17 C13EO 6-19 C14EO 6-17 aFraction numbers correspond to those in Figure 3-3. bChemical nomenclature: see text for explanation.
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3-25 Several conclusions can be drawn from the data presented in Table 3-7. All of the products contained one or more classes of polyethoxylated nonionic surfactants, and among these series, most had average EO numbers less than 10.
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3-26 TABLE 3-7 Summary of Surfactants Identified in Type I and Type IV Deicer Products by Q-TOF, MALDI, and LC-MS Mass Spectrometry Techniques Deicer Surfactants Identifieda Estimated Average EO Numberb Relative Spectral Abundancec Product He C10EO 2-19 C11EO 2-18 C12EO 1-20 C13EO 1-17 C14EO 1-18 C15EO 1-17 C16EO 1-5 6.13 8.13 6.08 6.08 6.66 9.53 2.85 2 1 100 3 19 5 1 Product Ie OPE 5-13 NPE 1-18*
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3-27 of deicer products K and I (Figure 3-10)
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3-28 Values represent mean ± SD (n = 3)
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3-29 product I contained 0.270 ± 0.017 percent polymeric thickener, product J contained 0.677 ± 0.006 percent polymeric thickener, and product K contained 0.237 ± 0.006 percent polymeric thickener. Validation of TIE Results Toxicity Testing of Reformulated "Mock" Deicer Products Resolution of the components responsible for observed toxicity in deicer products required a final stage of TIE testing; this was essentially a reverse TIE approach wherein mixtures were "built up" from identified and quantified components in order to verify that these components accounted for the full toxicity of the mixture from which they were originally isolated.
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3-30 for surfactants in products H and J were 0.09 g/L and 0.14 g/L respectively, both significantly lower than the surfactant concentrations measured in products I and K above (approximately 3.0 g/L)
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3-31 TABLE 3-10 Toxicity of Mock Type IV Deicer Product I to Aquatic Species EC50 and LC50 Values (mg/L) Formulation W ater Ethylene G lycol (59% )
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3-32 TABLE 3-12 Toxicity of Mock Type IV Deicer Product K to Aquatic Species EC50 and LC50 Values (mg/L) Formulation W ater Propylene G lycol (46.6% )
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3-33 TABLE 3-13 Toxicity of Selected Deicer Components Used in Mock Formulations EC50 and LC50 Values (mg/L) Component Microtox C
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3-34 surfactants. In one case, relatively high concentrations of triazole-based corrosion inhibitors in a Type IV deicer triggered toxicity in TIE assays.
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3-35 Biochemical Oxygen Demand Introduction The potential for aircraft and airfield deicing runoff to contribute to decreased DO in receiving waters is a function of the biodegradable materials in the deicers in stormwater discharges, and the characteristics of the receiving waters, which affect the rate at which biodegradation occurs. Biochemical oxygen demand (BOD)
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3-36 contribution of the "seed" material (i.e., source of microorganisms) and any demand exerted by the reagent water used to prepare the samples.
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3-37 Developing seed inoculums is typically done on a trial-and-error basis by attempting to find the ideal food (carbon) -to-organism ratio.
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3-38 TABLE 3-14 COD and BOD5 for Selected Aircraft and Airfield Deicers and Anti-icers COD BOD5 Values Expressed as Primary Source of Oxygen Demand Formulation % FPD Specific Gravity mg/kg % RSD (Replicates) mg/L mg/kg % RSD (3 Replicates)
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3-39 TABLE 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 Freshwater 20°C Marine Water 20°C Freshwater 5°C Marine Water 5°C Formulation Day Mean (mg/kg)
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3-40 TABLE 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 Freshwater 20°C Marine Water 20°C Freshwater 5°C Marine Water 5°C Formulation Day Mean (mg/kg)
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3-41 COD test results estimate the potential TOD for each of the liquid and solid deicer formulations. These results, as well as results from standard BOD5 and the 40-day BOD series testing, show wide variability among the tested products (Tables 3-14 and 3-15)
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3-42 TABLE 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 Mean BOD (mg/kg) Formulation Day Freshwater 20°C Marine Water 20°C Freshwater 5°C Marine Water 5°C 5 283,000 -- ND a -- 15 871,000 -- ND a -- 28 904,000 -- 200,000 -- EG Type I (as ethylene glycol)
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3-43 TABLE 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 Mean BOD (mg/kg) Formulation Day Freshwater 20°C Marine Water 20°C Freshwater 5°C Marine Water 5°C 28 970,000 987,000 894,000 721,000 40 993,000 1,240,000 897,000 718,000 5 NDa -- 631,000 -- 15 1,060,000 -- 797,000 -- 28 981,000 -- 916,000 -- Sodium acetate deicer (as acetate)
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3-44 Figure 3-11. Comparison of 5-day BOD results obtained using the traditional BOD5 and modified 40-day time-series methods.
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3-45 Figure 3-12. Percent biodegradation of selected aircraft and airfield deicers and anti-icers based on 5-Day BOD-to-COD ratios.
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3-46 Figure 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.
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3-47 Results of the 40-day freshwater tests at 5°C (Figure 3-15) indicate 23–55 percent degradation for EG products, 61–77 percent degradation for PG products, 86 percent for the potassium acetate product, and 94 percent for the sodium acetate product.
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3-48 Figure 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.
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3-49 Figure 3-17. Inhibitory effect of sodium formate deicer on the BOD5 test results.
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3-50 TABLE 3-17 First-Order Decay Rate Constants Computed from 40-Day Biochemical Oxygen Demand Testing with Aircraft and Pavement Deicing and Anti-icing Formulations Deicer Product Ethylene Glycol Propylene Glycol Type I Type IV Type I Type IV Potassium Acetate Deicer Sodium Acetate Deicer Sodium Formate Deicer F r e s h w a t e r 2 0 ° C Relative Decay Rate (1/day) (95% confidence interval)
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