EPA 600/3-91/016
March 1991
PB9 1-181958
MICROBIAL TRANSFORMATION RATE CONSTANTS
OF STRUCTURALLY DIVERSE MAN-MADE CHEMICALS
by
William C. Steen
Measurements Branch
Environmental Research Laboratory
Athens, GA 30613
Project Officer
William C. Steen
ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
ATHENS, GA 30613
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DISCLAIMER
T!ie information in this document has been funded by the United States
Environmental Protection Agency. It has been subject to the Agency's peer and
administrative review, and it has been approved for publication as an EPA
document. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use by the U.S. Environmental Protection
Agency.
11
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FOREWORD
As environmental controls become more costly to implement and the
penalties of judgment errors become more severe, environmental quality
management requires more efficient analytical tools based on greater knowledge
of the environmental phenomena to be managed. As part of this Laboratory's
research on the occurrence, movement, transformation, impact and control of
environmental contaminants, the Measurements Branch develops microbial
transformation rate constants for use in exposure and risk assessment models.
The U.S. Environmental Protection Agency reviews hundreds of new and
existing chemicals each year to determine their impact on the environment,
key process in the fate of these chemicals is microbially mediated
transformation. In this report, second—order microbial transformation rate
constants are provided for 35 chemicals of diverse chemical structure. The
data are Intended for use in mathematical models that are used in evaluating
chemical risk.
Rosemarie C. Russo, Ph.D.
Director
Environmental Research Laboratory
Athens, Ceorgia
iii
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ABSTRACT
To assise in estimating microbially mediated transformation rates of man-
made chemicals from their chemical structures, all second order rate constants
that have been measured under conditions that make the values comparable have
been extracted from the literature and combined with rate constants not
reported before to compile a comprehensive list of second order rate constants
for chemicals of diverse structures. Chemicals for which constants are
presented include seven chlorinated carboxylic acid esters of 2,4—
dichlorophenoxyacetic acid (2,4-D), phenol and seven substituted phenols,
three phthalate esters, three anilines, seven amides, and seven acetanilides.
The 35 constants were measured in the laboratory by a protocol that measures
disappearance of the chemical substrate as a function of time in the presence
of suspended natural populations from unpolluted aquatic systems. Second
order rate constants, k2 (L org.-1 hr."1), range from 4.2 x 10"8 for the hexyl
acid ester of 2,4,-D to 4.2 x 10"15 for the di—ethylhexyl phthalate ester.
iv
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MICROBIAL TRANSFORMATION RATE CONSTANTS
OF STRUCTURALLY DIVERSE MAN-MADE CHEMICALS
INTRODUCTION
The U.S. Environmental Protection Agency's Office of Toxic Substances
(OTS) reviews about 1800 new chemicals and about the same number of existing
chemicals annually to determine their potential impact on the environment. A
principal consideration in the review process is the chemical's persistence in
the ambient environment. For many man-made chemicals, a major mechanism for
transformation is mlcrobially mediated transformation. Therefore, it is
necessary to assess the rate at which chemicals under review will undergo
microbial transformation under environmental conditions (3). Information on
microbial transformation rates is provided to OTS for only about 2 percent of
the chemicals submitted for review, and relevant information on microbial
transformation is sparse in the literature.
In the absence of measured microbial transformation rate constants, the
OTS reviewers muse estimate the rate on the basis of chemical structure (1).
To assist OTS in predicting microbial transformation from chemical structure,
this report lists second order microbial transformation rate constants,
measured in the laboratory using the same protocol, for 35 chemicals of
diverse chemical structure. Included in the data are rates for 7 para-
substituted acetanilides not reported previously.
1
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THE MEASUREMENT PROTOCOL
The protocol used for measuring the second-order rate constants is
described in detail by Steen (10). A flow diagram of the procedure is
presented in Figure 1. This report will Include only a brief summary of the
protocol.
Collection of microbiota is accomplished by a grab-sampling technique—
3.8—liter amber glass jugs are immersed in the appropriate aquatic source
until full. The aquatic sites chosen for study had no known history of
exposure to the organic chemical being investigated. At sampling, water
temperature is recorded. Samples are transferred immediately to the
laboratory. Population densities and pH are measured from sub-samples taken
after arrival at the laboratory. Physical, chemical, and biological
properties or characteristics of the waters are recorded.
Methodologies for determining suspended population densities, for
measuring parent chemical disappearance, for preparing of sterile and non-
sterile treatments, and for analyzing metabolites and products are covered in
detail by Steen (L0). Treatment of the aquatic samples in the laboratory
takes one of two courses prior to determination of the experimental second-
order rate constant. Based on preliminary investigations and determination of
the rate of disappearance of the test chemical using unconcentrated natural
populations, a decision is made either to determine rate constants using
Initial population densities or to concentrate the population when the initial
rate proves too slow to measure reproducibly or permit adequate estimation.
For unconcentrated populations, a test chemical is added and chemical
disappearance as a function of time is measured. When concentration of
microbial population is required, larger volumes of the aquatic source are
sampled. This is necessary because bacterial populations in water samples may
be concentrated 10-fold by filtering 22 liters through a 0.22-pm-pore-diameter
membrane filter (Nucleopore or equivalent) prevashed with sterile distilled
water. Following filtration, filters are collectively placed in 3—liter,
wide-mouth, cotton-plugged Erlenmeyer flasks containing 2.2 liters of the
original aquatic source. Sterile aqueous stock solutions of nutrients are
prepared to yield concentrations (g/L) of NH*C1 (0.5),(NHt)2S0» (0.5), Na2HP04
(0.5), KH2PO* (0.5), HgSO* (0.001), and FeCl3 (0.001). No more than 1 ml of
each nutrient then is added to the concentrated bacterial population
resuspended from the filters to the aqueous phase. Bacterial suspensions are
incubated for 68 hours at 22*C in a temperature-controlled shaker (150 to 200
rpm) prior to the addition of supplemental nutrients. This procedure effects
a 10— to 100—fold enhancement of the natural bacterial population and allows
for maintenance of the population over the incubation period. Concentrating
the populations enables measurement of rates of transformation of chemicals
that would otherwise be difficult to measure at the low indigenous population
levels normally encountered in the aquatic sources.
2
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Procedures for calculating the second-order microbial transformation rate
stant have been covered in detail by Paris et al. (5) and Steen (10). The
a equation used for this determination is:
-d(S]/dt - k2(B](S] (1)
re [S] is the concentration of the chemical, [B] is the concentration of
suspended bacterial population, and k2 is the second—order rate constant
ressed as L org.'1 hr."1. The second—order rate constants vere determined
forcing the overall reaction to proceed in a pseudo first—order fashion by
ntaining the microbial population in great excess relative to the
centratlon of the chemical substrate.
UMPTIONS AND LIMITATIONS
Four assumptions are made in application of the protocol. First, the
centage of degrader organisms for newly encountered, man-made chemicals Is
uned to be about the same in all natural, unpolluted surface waters. While
s assumption needs much more study, the work of Paris et al. (5) provides
stantial support for this assumption. Second, it is assumed that
ptation time is ignored in calculating rates. For most chemicals
estigated, adaption time (if not an artifact of the measurement protocol)
short (less than 50%) relative to total transformation time. Third, the
strate (test chemical) concentration is assumed to be much less than the
oretical Ks half—saturation concentration and the reaction kinetics are
umed to be first-order with respect to substrate concentration. Fourth,
carbon and energy contributions from the test chemical are assumed to be
ufficient to cause measurable growth of the constitutive populations.
These assumptions and limitations notwithstanding, the data presented in
s report should provide a reliable basis for comparing the relative
radation rates of the chemicals measured by the same protocol, and the
ues developed should contribute substantially to estimation of microbially
lated transformation on the basis of chemical structure. Justification for
rapolation of results beyond the conditions listed in the references has
been fully, established. The use.of a standard protocol, a consistent set
assumptions, and a bench mark chemical approach for determination of
ative degradation rates was addressed by Newton et al. (4).
3
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SOURCES OF CHEMICALS
Chemicals used in all of the microbiological investigations were obtained
from analytical stocks of major chemical manufacturers, from the analytical
chemical repository of EPA's Pesticides and Industrial Chemicals Repository,
Research Triangle Park, North Carolina, or from analytical stocks of the
Environmental Research Laboratory, Athens, Georgia. In all cases, chemicals
investigated were in excess of 95 percent purity. All spike solutions were
prepared under aseptic conditions from these analytical stocks. Co—
chromatography, gas chromatography-infrared spectroscopy, and gas
chromatography-mass spectrometry vere used to identify or confirm knovn or
speculated products/metabolites.
RESULTS AND DISCUSSION
The microbial transformation rate constants presented in this report were
measured as a part of eight different studies. The most significant thing
about the constants from the standpoint of using t-.hea to estimate the reaction
rates of other compounds is that they were all measured in thr. same way
Tables 1 through 4 reflect historical data genevated for the purpose of
testing th-j second-order mathematical expression as an adequate predictor of
microbial transformation rates in natural aqv.atic systems. Rate constants
likewise, were used in the development of p7:operty—reactivity relationships
(relationships between chemical properties and biological reactivity). Tables
5 and 6 summarize rate constants generated by a standard protocol developed
from previous experimental efforts (literature cited) for measurement of
relative microbial transformation rates using standard methodologies, an
aquatic source extensively characterized, and for the development of property-
reactivity relationships.
The first series of chemicals tested (Table 1) were those presented by
Paris et al. (5) in a study to determine Che variability in rate constants
measured by a protocol in which the total microbial population was measured to
provide the value for [B) in Equation 1. Hicrobial transformation rate
constants were measured for three chemicals representing somewhat diverse
structures. These comparisons also were made between and among some 40
natural freshwater aquatic sites encompassing a wide variety of aquatic
systems. Additionally, the waters spanned a fairly vide range of
temperatures. For the three chemicals investigated, butoxyethyl ester of 2.4-
dichlorophenoxyacetic acid (2,4—DBE), malathion (an organophophorous
insecticide), and chlorpropham (CIPC), microbial transformation rate constants
were not measurably different from site to site. Hean values of second-order
microbial transformation rate constants for the 40 natural aquatic sites were
5.4 (±2.7) X 10"10, 4.4 (±2.9) X I0"n, and 2.6 (±1.3) X 10"1* liter org."1 hr."1
for 2,4 DBE, malathion and CIPC, respectively. Results of these
investigations also suggested strongly that the second—order rate expression
could be used to describe microbiological transformation of xenobiotics at low
concentrations, which was the focus of the investigation. Rate constants (kz)
for the three chemicals were reproducible (Coefficient of Variation
approximately 65%). An additional investigation by Rogers ec al. (9) showed
significantly larger variations in measured second-order rate constants using
4
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similar methods. The reasons for these differences are not clear and should
be investigated in future studies.
Results of an early study of property—reactivity reported by Paris et al.
(7) provided microbial transformation rates for phenol and seven substituted
phenols: p-methylphenol, p—methoxy phenol, p-chlorophenol, p-bromopbenol, p—
acetylphenol, p—cyanophenol, and p—nitrophenol. Table 2 provides a summary of
the mean microbial rate constants for the eight phenols studied in waters from
five different sites. The variation from site to site is apparently well
within the approximate 65% coefficient of variation presented by Paris et al.
(5). This study involved a different microbiological pathway (microbial
oxidation) from the hydrolytic pathways investigated to this point.
The study of three phthalate esters by Steen et al. (12) to determine the
effects of sediment sorption on microbial transformation provided the data in
Table 3. For these three chemicals, the major microbial transformation
occurred in the aqueous phase.
Tables 4 through 7 present results from studies related to property-
reactivity correlations, which are becoming more and more important as the
need to predict microbial transformation rates for man-made chemicals
continues to increase and the number of laboratory measurements remains
relatively small. Tables 4 and 5 contain measured transformation rate
constants for a series of chlorinated carboxylic acid esters and a series of
substituted anilines studied by Paris et al. (8) and Paris and Wolfe (6). In
both studies, property/reactivity relationships were sought. The relationship
between microbial transformation ind hydrophobicity using K,,,, was examined
for the esters of chlorinated carboxylic acids. For the substituted anilines,
microbial transformation was related to bulk substituent steric properties
such as Vander Waals radii. The esters of the chlorinated carboxylic acids
were transformed via classical microbiological hydrolytic processes, whereas
the substituted anilines were transformed through different enzymatic
mechanisms dloxygenases classed as oxidation processes.
Steen and Collette (11) developed what has been described as a highly
promising departure from tradition.il property—reactivity relationships (2).
The rate constants for seven amides presented in Table 6 were used to relate
infrared spectral characteristics to microbial transformation. To extend this
concept to para-substituted acetanilides, Steen is reporting the rate
constants in Table 7 for the first time in this report. A thorough analysis
of the results will be presented in a subsequent report. For the para-
substituted acetanilides, the initial attack by suspended bacterial
populations is assumed to be an hydrolytic reaction at the N—C-O bond to yield
para substituted aniline as the primary metabolite/product. Based on co-
chromatography with known analytical standards, this appears to have been the
case. This observation will be confirmed by spectroscopic analysis.
Microbial transformation rates are currently being measured for two
additional classes of organic chemicals, halogenated aromatic and aliphatic
ethers and sulfonyl urea—based chemicals under development for use as
herbicides.
5
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Table 8 is a compilation of all of Che rate constants for the 35 chemicals
which the measurement protocol has been applied. This relatively small
amber of compounds represents the largest number of chemicals for which
aboratory measurement of second order microbial transformation rates have
een performed by the same protocol and are therefore comparable for use in
redicting microbial transformation based on chemical structure.
6
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LITERATURE CITED
1. Boethling, W.C. and S. Sabljic, "Screening—Level Model for Aerobic
Blodegradablllty Based on A Survey of Expert Knowledge," Environ. Sci.
Technol. 21. 672-679. (1989).
2. Borman, S., "New QSAR Techniques for Environmental Assessments," Chem. a
Engr. News. £8, 19-23. (1990).
3. Freed, J.R., S.N. Nacht, T. Chambers, W.N. Christie, and C.E. Carpenter,
Methods for Assessing Exposure to Chemical Substances. Volume 2. U.S.
Environmental Protection Agency, Vashington, DC, EPA 560/5-85-002. (1985).
4. Newton, T.D., G.K. Cattie, and D.L. Lewis, "Initial Test of the Benchmark
Chemical Approach for Predicting Microbial Transformation Sates in Aquatic
Systems," Appl. Environ. Microbial. 288-291 (1990).
5. Paris, D.F., W.C. Steen, G.L. Baughman. and J.T. Barnett, Jr., "Second-
order Model to Predict Microbial Degradation of Organic Compounds in
Natural Waters," Appl. Environ. Microbiol. 41, 603—609 (1981).
6. Paris, D.F. and N.L. Wolfe, "Relationship Between Properties of a Series
of Anilines and Their Transformation by Bacteria," Appl. Environ.
Microbiol. £1, 911-916 (1987).
7. Paris, D.F., N.L. Wolfe, W.C. Steen, and C.L. Baughman, "Effect of Phenol
Molecular Structure on Bacterial Transformation Rate Constants in Pond and
River Samples," Appl. Environ. Microbiol. 45, 1153—1155 (1983).
8. Paris, D.F., N.L. Wolfe, and W.C. Steen, "Microbial Transformation of
Esters of Chlorinated Carboxylic Acids," Appl. Environ. Microbiol. 47, 7-
11 (1984).
9. Rogers, J.E., S.W. Li, and L.J. Felice, Microbial Transformation Kinetics
of Zenoblotlcs in the Aquatic Environment. U.S. Environmental Protection
Agency, Athens, GA, EPA-600/3-84-0430. (1983).
10. Steen, W.C., Interim Protocol for Measuring Microbial Transformation Rate
Constants for Suspended Bacterial Populations In Aouatic Systems. U.S.
Environmental Protection Agency, Athens, GA, EPA—600/3-88-007, 1988.
11. Steen, W.C. and T.W. Collette, "Microbial Degradation of Seven Amides by
Suspended Bacterial Populatons,K Appl. Environ. Microbiol. 2545-2549,
1989.
12. Steen, W.C., D.F. Paris, and G.L. Baughman, "Effects of Sediment Sorption
on Microbial Degradation of Toxic Substances," pp. 168-173 in Proceedings
of the Symposium on Processes Involving Contaminants and Sediments. R.
Baker, (ed.), American Chemical Society, Washington, DC, 1979.
7
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Figure 1. RATE CONSTANT MEASUREMENT FLOW SCHEME
Sample
Spike to desired
test concentrations
oo
Samples taken through 2-3 haif-Uves
<10*15 sanples/flask)
Calculate mean concentration
of organism (org/1 or cfu/1)
Dispense into approp.
reaction vessels
Filter end/or
Autoclaved
SterUe Controls
*>-sterfle water
Cfopl1cBt«s/
tiepllcetes
Prepared Stock
Aqueous Solution
of Test Chemical
9ulk Aqueous Sample (i liters)
Record Temp at Sampling
Extraction with
appropriate solvent
for GC analysis or
direct HPLC analysis
of aqueous sample
Samples taken concurrently
for determination of
population concentret tons
with tine
linear-least squares analyrls of
chemical disappearance uith
time (psevxto-i1rst-«rder rate
constant)
Characterize bacterial
population (conc. etc.)
Plate court or
Direct Microscopic counting
Determine (a) nutrient status
(*, P. C)
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Table 1. MICROBIAL TRANSFORMATION RATE CONSTANTS IN AQUATIC
SYSTEMS FROM ACROSS THE CONTINENTAL UNITED STATES*
Size
Teop CC>
k, (liters oroanfsa'V}
2.4-DBE
Nalathion
CIPC
Northeast
John's Creek
19
(2.4
*
1.0)
X
10"
Potts Ht. Creet
20
(8.6
t
4.5)
X
10"
Roanoake River
21
(3.9
*
2.2)
X
10*"
Augusta Creek
10
(6.5
*
1.8)
X
10-"
Sautatuck River (a)
10
(1.5
*
0.3)
X
10""
Carnegie Lake
2
(1.6
t
0.4)
X
10""
Oneida Lake
16
(6.7
t
2.1)
X
10'"
Princeton Ca^at
7
Southeast
Hickory Hi lis Pond
26
10"
Oconee River
20
(3.1
*
1.9)
X
Black Warrior River
22
U.S. Department of
10"
Agriculture pond
25
(5.0
*
2.7)
X
Weiss Reservoir
27
Manchester Creek
IP
(4./
*
3.2)
X
Iff-"
Shoals Creek
20
(6.7
a
4.6)
X
10-"
Rich I arid Creek
17
(6.4
t
2.2)
X
10-"
Overtook Lake
25
(1.6
t
0.6)
X
10"
Okefenokee Swanp
20
(7.6
t
4.7)
X
10"
Walker-s Prong
26
(11.5
*
8.9)
X
10"
Mississippi River
18
(12.0
t
5.6)
X
10"
Guntersville Lake
29
(5.9
t
2.0)
X
10""
Escambia Bay (a)
24
10-"
Coweeta Creek
17
(5.2
t
2.7)
K
Coosa River
28
Wheeler's Lake
27
(4.9
t
1.4)
X
10-"
Tennessee River
27
(1.7
* 0.6)
X
10""
Gulf Breeze (a)
27
(5.6
t
2.9)
X
10-"
Northwest
Willamette River 20
Ouluth water treatment 17
St. Louis Diver 18
Pond Oregon 20
(5.4 i 1.0) X 10"'
{6.0 i 1.7) X 10"1
(2.9 * t.1) x 10"
(6.2 * 3.7) X 10 -1
(2.7 x 2.0) X 10 "
(2.5 i 1.4) X 10 "
(2.0 t 1.6) X 10 "
(6.3 l 3.2) X 10 "
(3.6 t 2.9) X 10"
(1.8 » 1.3) X 10''
(3.0 ± 2.3) X 10 "
(5.5 *
3.3)
X
10"
(1.7 i 1.2) X 10 "
(5.3 *
2.9)
X
10"
(1.3 I 1.0) X 10"
(5.9 *
2.3)
X
10"
(2.2 t 1.6) X 10
(2.1 t 1.5) X 10"'
(2.9 t 2.1) X 10'*
Coluifcia River
20
(6.8 *
2.6) X 10 "
(4.2 t
3.6)
X
10""
Blue River (sinner) (b)
26
(37 ±
12) X 10"'4
(5.2 i
1.0)
X
10"
Blue River (winter)
1
(7.1 *
6.3) X 10*"
Lake Superior
16
(4.9 t
3.0)
X
10-"
(4.9 t
4.1)
X
10
Southwest
Ada
20
(6.3 i
3.1) X 10""
(3.1 i
2.1)
X
10
SearsviIle
15
(5.5 *
1.8) X 10-"
Trinity River
12
(3.6 i
1.6) X 10*"
Lake Travis
22
(2.3 t
1.3) X 10*"
(4.0 t
3.0)
X
10"
(3.9 t
1.8)
X
10
Lake Head
22
(3.8 i
1-5) X to*"
(4.4 t
2-2)
X
10"
HEAD 19.5 * 6.7 (5.4 t 2.7) X Hr4* (4.4 * 2.9) X 10 " (2.58 i 1.29) * 10 "
* Data taken from Paris et at., 1981.
a Marine waters.
b Not included in nean value or statistical analysis.
9
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Table 2. MICROBIAL TRANSFORMATION RATE CONSTANTS
FOR A SERIES OF SUBSTITUTED PHENOLS"
k, <1 org/'hr."1) (Bean (t S.E.)'
Conpound Mean for all sites
Phenol (3.3 * 1.2) * 10 "
a-Hethylphenol (2.7 * 1.3) * 10'"
g-Methoxyphenol (2.2 t 1.1) X 10'"
g-Chlorophenol (7.1 * 1.6) X 10'"
(2-Bronupfcenol (9.1 l 1.0) X 10'"
B-Acetylphenol (2.0 * 1.0) X 10'"
g-Cyenopfienol <*.2 t 1.7) X 10"'*
e-Nitrophenol (3.8 * 1.4) X 10'"
a Extracted from Paris et at., 1983.
b Mean value of eight determination per site with the standard
error of the estimate.
3. MICROBIAL TRANSFORMATION OF A SERIES OF PHTHALATE
ACID ESTERS IN NATURAL AQUATIC SYSTEMS
Compound k, (L or8."'hr.'1)*
Dl-butyl phthalate (3.1 t 0.8) X 10'"
Di-octyl phthalate (3.7 t 0.6) X 10'"
Dl-ethyl hexyl phthalate (4.2 t 0.7) X 10'"
* Extracted from Steen et al., 1979.
10
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Table 4. SECOND-ORDER RATE CONSTANT FOR ESTERS OF
2,4 DICHLOROPHENOXYACETIC ACID IN 5 SITES"
2,4 0 ester
k, (L orfl/'hr."1 * S.E.) mean of all sites'
Methyl
(5.8 * 0.9) X IC-'0
Ethyl
(5.2 * 1.6) X 10-"
Propyl
(2.9 t 1.2) X 10"*
Butyl
(4.1 * 1.2) X 10"*
Hexyl
(4.2 t 3.3) X 10"*
Octyl
(3.2 t 1.1) K 10"*
a Fro® Paris et al., 1984.
b Hean of eight determinations per site.
Table 5. TRANSFORMATION RATE CONSTANTS FOR
THREE ANILINES AND THREE SITES"
Compound
Aniline
3-Cfilorooril line
3-Nltroanlllne
k, (L ora-^hr."1)*
Mean kt for alt sites
(1.1 t 0.8) X 10 "
(2.2 t 1.7) X 10*"
(4.6 * 0.1) X 10 "
a Paris and Wolfe, 1987.
b Mean value of eight determinations per site t standard error of
the estfpate.
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Table 6. SECOND-ORDER RATE CONSTANTS FOR SEVEN AMIDES
Second-order Rate Constant
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Table 8. COMPILATION OF SECOND-ORDER MICROBIAL TRANSFORMATION
RATE CONSTANTS MEASURED AT ATHENS ENVIRONMENTAL
RESEARCH LABORATORY FOR 35 ORGANIC CHEMICALS
Chemical Class
CAS Mo.
k, (L org.
Butyl
(94-80-4)
(4.1
t 1.2)
X
10-*
Butoxy ethyl
(1929-73-31
<5.4
i 2.7)
X
10-"
Ethyl
(533-23-3)
(5.2
* 1.6)
X
10"
Hexyl
(1917-95-9)
(4.2
* 3.3)
X
10"*
Methyl
(1928-38-7)
<5.8
t 0.9)
X
10-"
Octyl
(1928-44-5)
<3.2
* 1.1)
X
10"*
Propyl
<2.9
* 1.2)
X
10-*
Phenots
Phenol
(108-95-2)
<3.3
* 1.2)
X
10"
g-acetyl
(99-93-4)
<2.0
t 1.0)
X
10""
fi-brorao
(106-41-2)
<9.1
t 1.0)
X
10"
E" chloro
(106-48-9)
<7.1
t 1.6)
X
10"
Q-cyano
(767-00-0)
<4.2
t 1.7)
X
10"
fi-nltro
(100-02-7)
<3.8
t 1.4)
X
10"
g-methoxy
(150-76-5)
<2-2
t 1.1)
X
10"
B* methyl
(106-44-5)
<2.7
t 1.3)
X
10"
Phthalate ester
di-butyl
(84-74-2)
<3.1
t 0.8)
X
10"
dl-ethylhexyl
(1*7-81-7)
<4.2
t 0.7)
X
10"
di-octyl
(117-84-0)
<3.7
t 0.6)
X
10"
Anilines
Aniline
(6*.-53-3)
<1.1
x 0.8)
X
10"
3-chloro
(108-42-9)
<2.2
x 1.7)
X
10""
3-nitro
(99-09-2)
<4.6
l 0.1)
X
10""
Amides
10"
2-acet amidofIuorene
(53-96-3)
<4.8
t 2.8)
X
btnitnllide
(93-98-1)
<2.4
t 0.7)
X
10"
Mortal ide
(7287-36-7)
<6.0
t 2.3)
X
10"
Niclosamide
(50-65-7)
<2.0
t 0.8)
X
10"
Pronamide
(23950-58-5)
<5.0
t 2.3)
X
10"
Propochlor
(1918-16-7)
<1.1
* 0.9)
X
10"
Propanfl
<709-98-8)
<5.0
t 2.7)
X
10-"
Acetanilides
Acetanllide
g-bccrao
p-chloro
g-cyano
g-methaxy
methyl
B-nitro
(103-84-4)
(1.48
*
1.02)
X
10-"
(103-88-8)
(3.85
l
2.27)
X
10"
(539-03-7)
(1.11
l
0.65)
X
10"
(35704-19-9)
(1.45
l
1.19)
X
10'"
(51-66-1)
(8.51
t
3.97)
X
10'"
(103-89-9)
(1.70
t
0.57)
X
10""
(104-04-1)
(2.20
«
0.68)
X
10-"
13
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