\u United States Environmental Protection Agency Environmental Research Laboratory Athens GA 30613 Research and Development EPA/600/S3-88/028 Sept. 1988 &EPA Project Summary Measurement of Hydrolysis Rate Constants for Evaluation of Hazardous Waste Land Disposal: Volume 3. Data on 70 Chemicals J. Jackson Ellington, Frank E. Stancil, Jr., William D. Payne, and Cheryl D. Trusty To provide input data for a mathematical model to estimate poten- tial ground-water contamination from chemicals in land disposal sites, hydrolysis rate constants were measured for 70 regulated chemicals under careful- ly controlled conditions. Hydrolysis rates were measured under sterile conditions at precisely controlled temperatures and at three hydrogen-ion concentrations (ph 3, 7, and 11). Conditions were adjusted to provide sufficiently precise rate con- stants to meet modeling requirements, as determined through model sensitivi- ty tests. In addition to precise control of temperature and pH, precautions were taken to minimize impact of adventitious processes. Chemical concentrations as a function of incubation time in the con- stant temperature bath were measured by gas chromatography, liquid chroma- tography, or ion exchange chromatogra- phy. Identities and purities of the chemicals were determined by mass spectrometry supplemented, and in some cases, by infrared spectrometry. Four chemicals (DL-rrans-4- chlorostilbene oxide, benzyl chloride, 2, 4-dichlorophenoxyacetic acid methyl ester, and lindane) were used as stan- dard reference compounds (SRCs) to en- sure reproducibility of analytical opera- tions and control of parameters that af- fect hydrolysis rates of chemicals in an aqueous environment. The methyl ester and lindane were used as SRCs in the pH ranges of 8 to 9.5 and 9.5 to 11, respec- tively. Benzyl chloride and the stilbene oxide were used in conjunction with neutral and acidic hydrolysis rate deter- minations, respectively. Determinations of the hydrolysis rates of the SRCs repeated at varying temperatures and pHs over a 2-year period yielded coeffi- cients of variation of less than 12% in the measurements. This Project Summary was developed by EPA's Environmental Research Laboratory, Athens, GA, to announce key findings of the research project that is fully documented in a separate report of the same title (see Project Report order- ing information at back). Introduction The Hazardous and Solid Waste Amend- ments of 1984 to PL 98-616 (RCRA) stipulate that land disposal of "hazardous wastes" is prohibited unless the EPA Ad- ministrator determines that prohibition of some wastes is not required to protect human health and the environment because those particular wastes are not likely to reach unacceptable levels in groundwater as a result of land disposal. The amendments define hazardous waste ------- as any of 362 specific compounds (either part of or inclusive of Appendix VIII com- pounds). In compiling this list, major con- siderations were the toxicity and quantity of the waste material generated annually. In implementing the 1984 Hazardous and Solid Waste Amendments to the Resource Conservation and Recovery Act (RCRA), EPA's Office of Solid Waste (OSW) will app- ly a decision rule based on a mathematical model of chemicals under consideration that considers horizontal underground movement of a chemical in a contaminated aquifer offsite to a withdrawal point based on advection, dispersion, sorption, and chemical hydrolysis. Application of the model requires as input the second- or first- order hydrolysis rate constants for those chemicals containing hydrolyzable func- tional groups. It is necessary to acquire hydrolysis rate constants for each of the 362 chemicals ex- cept for solvents ("fast track" in the list), which will be treated as non-degrading, non-sorbing constituents and chemicals already banned by the State of California (listed as "California"). These two groups comprise 21 and 44 chemicals, respective- ly. The remainder of the 362 chemicals were separated for regulation into three fac- tions by EPA's Office of Solid Waste: 81 in the "first third," 121 in the "second third," and 95 in the "third third." This report pro- vides first- and second-order hydrolysis rate constants for all those organic compounds in the first and second "thirds" plus an ad- ditional 12 chemicals of interest (Table 1) for which satisfactory values were not developed in an earlier evaluation process. It also describes the laboratory experiments conducted to measure hydrolysis rate constants. The Environmental Protection Agency has proposed that manufacturers and pro- cessors of the remaining 31 "third third" chemicals be required, under Section 4 of the Toxic Substances Control Act (TSCA), to perform testing for chemical fate in- cluding determination of hydrolysis rate constants. Hydrolysis Measurements A typical hydrolysis experiment consisted of preparing a spiking solution of the com- pound of interest, preparing buffer solu- tions, transferring spiked buffer to individual "rate point tubes" (15-ml sealed ampules), then monitoring disappearance over time by analyzing individual tubes and determin- ing the amount of compound remaining. Spiking solutions were prepared by dissolving the compound in acetonitrile, methanol, or water. The concentration was such that 0.1 ml diluted to 100 ml with buf- fer gave a test compound concentration that was 1x10-s/W or was 50% of the water solubility or less. Initial screening hydrolysis runs were per- formed at three pH levels (3, 7, and 11). Buf- fer pH was measured at the temperature of the hydrolysis run. These initial hydrolysis runs were used to set pH and temperature conditions for subsequent rate constant measurements. The measure- ments of rate constants were normally per- formed in triplicate; however, some com- pounds required more replicates and some less. Standard Reference Compounds (SRCs) Chemical standards of known concentra- tion have long been used for assuring reliability of quantitative chemical analyses, calibrating instruments, and measuring recoveries of analytes from various matrices. In a manner analogous to using chemicals of known concentration as stan- dards for concentration measurement, chemicals whose hydrolysis rate constants have been measured with established precision by one experimenter or group can be used as SRCs by other experimenters in establishing and maintaining quality con- trol in rate measurements. Four compounds were used as SRCs for this study, one each for acid and neutral hydrolysis, and two for base hydrolysis. Reproduction of the hydrolysis rate con- stants of the SRCs at the established con- centrations, pHs, and temperatures en- sured that the experimental conditions were reproducible ahcTnefped 'evaluate the ac- curacy and precision of measurements for the other compounds. Frequency Distribution of Hydrolysis Rate Constants The frequency distribution of the measured/extrapolated half-lives for 127 of the 362 OSW compounds is represented in Figure 1. The actual hydrolysis rate con- stants for these compounds can be found in Tables 1 and 2 and reference 1 of the complete text. The 127 chemicals covered a wide range of chemical classes and chemical reactivity within each class. Thus, the distribution in Figure 1 (60% of half- lives < 3 years) might be considered as be- ing representative of organic compounds in general. Table 1. Hydrolysis Rate Constant and Half-Lives at 25°C for Selected Compounds CAS Number 108-90-7 628-89-7 107-07-3 594-20-7 95-50-1 541-73-1 106-46-7 24009-05-0 608-93-S 319-94-8 95-94-3 88-06-2 Compound Chlorobenzenea 2-(2-Chloroethoxy) ethanol 2-Chloroethanol (41, 42) 2, 2-Dichloropropane 1, 2-Dichlorobenzenea 1,3-Dichlorobenzenea 1,4-Dichlorobenzenea 1-Hydroxychlordeneb Pentachlorobenzenea Pentachlorocyclohexene (gamma PCCH) 1, 2,4,5-Tetrachlorobenzenea 2,4,6-Trichlorophenolc Rate Constants Acid Neutral (32+0.1) x 10-5 4.5 x 10-6 (4.7 ±0.2) x 10-2 3.0 x 10-5 (2.3±3.5) x 10-7 Base <09 36.0 <0.9 <0.9 <0.9 <1 X 10-4 <09 74 + 3 <0.9 Calculated Half-life at pH 7, 25°C > 900 yr 3yr 9.9 yr 15 hr > 900 yr > 900 yr > 900 yr 200,000 yr > 900 yr 2.1 yr > 900 yr >40 yr a= Based on assumed base mediated 1% disappearance after 16d at 85°C and pH 9.70 (pH 11.26 at room temperature). b = Based on assumed base mediated 5°/o disappearance after 48d at 85°C and pH 9.51 (pH 11.04 at room temperature). c = Based on assumed 5% disappearance after 330 hr at 85°C. ------- Figure 1. 0-1 hr 1-24hr 1 -30 d 1-12 mo 1-3 y Half-Life (25°C, pH 7) Half-lives of OSW compounds. 3-5 y 5-10 Y >10y The EPA authors J. Jackson Ellington (also the EPA Project Officer, see below), and Frank E. Stancil. Jr., are with the Environmental Research Laboratory, Athens, GA 30613; William D. Payne is with Technology Applications, Inc., Athens GA 30613; and Cheryl Trusty is with the University of Georgia, Athens, GA 30613. The complete report, entitled "Measurement of Hydrolysis Rate Constants for Evaluation of Hazardous Waste Land Disposal: Volume 3. Data on 70 Chemicals," (Order No. PB 88-234 042/AS; Cost: $12.95, subject to change) will be available only from: National Technical Information Service 5285 Port Royal Road Springfield, VA 22161 Telephone: 703-487-4650 The EPA Project Officer can be contacted at: Environmental Research Laboratory U.S. Environmental Protection Agency College Station Road Athens, GA 30613 ------- United States Center for Environmental Research Environmental Protection Information Agency Cincinnati OH 45268 Official Business Penalty for Private Use $300 EPA/600/S3-88/028 OCOG329 PS U S E»¥IR PROTECTION AGClfCT REGION 5 LIBRART Z30 S DEARBORN STRfET CMICftGO IL 60«04 ------- |