\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

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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.

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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

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