To provide input data for a mathematical model to estimate potential groundwater contamination from chemicals in land disposal sites, hydrolysis rate constants were measured for 70 regulated chemicals under carefully 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 constants to meet modeling requirements, as determined through model sensitivity 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 constant temperature bath were measured by gas chromatography, liquid chromatography, or ion exchange chromatography. Identities and purities of the chemicals were determined by mass spectrometry, supplemented, in some cases, by infrared spectrometry. Four chemicals (DL-trans-4-chlorostilbene oxide, benzyl chloride, 2,4-dichlorophenoxyacetic acid methyl ester, and lindane) were used as standard reference compounds (SRCs) to ensure reproducibility of analytical operations and control of parameters that affect hydrolysis rates of chemicals in an aqueous environment.

Distributed to depository libraries in microfiche. Caption title. "EPA/600-S3-88-028." "Sept. 1988."