Document ID: EPA-HQ-OPP-2002-0188-0011
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2002-09-16T04:00Z

U.
S.
ENVIRONMENTAL
PROTECTION
AGENCY
WASHINGTON,
DC
20460
.
OFFICE
OF
PREVENTION,
PESTICIDES
AND
TOXIC
SUBSTANCES
PC
Code:
107201
DP
Barcode:
D215026;
D268715
MEMORANDUM
SUBJECT:
Tier
I
Estimated
Environmental
Concentrations
of
Hexazinone,
for
use
in
Human
Health
Risk
Assessment
FROM:
Larry
Liu,
Ph.
D.,
Environmental
Scientist
ERB
V,
Environmental
Fate
and
Effects
Division
(7507C)

THROUGH:
Mah
T.
Shamim,
Ph.
D.,
Chief
Environmental
Risk
Branch
V
Environmental
Fate
and
Effects
Division
(7507C)

TO:
Margaret
Rice,
Chief
Dirk
Helder,
Chemical
Reviewer
Manager
Reregistration
Branch
II
Special
Review
and
Reregistration
Division
(7508C)
and
Sherrie
Kinard,
Residue
Chemist
Carol
Christenson,
Risk
Assessor
RRB
II,
Health
Effects
Division
(7509C)

This
memorandum
presents
the
Tier
I
Estimated
Environmental
Concentrations
(EECs)
for
the
herbicide
hexazinone
for
use
in
the
human
health
risk
assessment.
EEC's
on
surface
waters
were
estimated
using
the
Tier
I
model
FIRST.
The
EEC's
on
groundwaters
were
estimated
using
an
available
small­
scale
prospective
groundwater
monitoring
study.
This
memorandum
also
provides
information
about
the
groundwater
prospective
small­
scale
study
conducted
by
the
registrant,
and
how
it
was
used
to
estimate
the
total
hexazinone
residues
in
ground
waters.
In
addition,
monitoring
data
available
from
the
state
of
Maine
was
presented.

The
surface
water
concentrations,
for
hexazinone
residues
were
as
follows:
acute
(peak)
value,
130
ppb,
and
the
chronic
annual
average
value,
47
ppb,
based
on
the
application
of
hexazinone
on
alfalfa,
which
is
the
major
food
crop
for
the
chemical.
The
groundwater
screening
concentration
for
hexazinone
residues
is
41.8
ppb.
These
values
represent
upper­
bound
estimates
of
the
concentrations
that
might
be
found
in
surface
water
and
groundwater
due
to
the
use
of
hexazinone
on
representative
crops.
It
is
noted
that
the
groundwater
screening
concentration
for
hexazinone
residues,
based
on
the
groundwater
prospective
monitoring
study
is
of
the
same
order
of
magnitude
than
the
groundwater
concentration
estimated
from
the
Tier
I
model
SCIGROW
(i.
e.,
20.2
ppb).
2
Should
the
results
of
this
assessment
indicate
a
need
for
further
refinement,
please,
contact
us
as
soon
as
possible
so
that
we
may
schedule
a
Tier
II
assessment.

Hexazinone
Environmental
Fate
Properties
Based
on
the
available
information,
hexazinone
appears
to
be
persistent
and
mobile
in
soil
and
aquatic
environments.
The
mobility
of
hexazinone
was
demonstrated
in
batch
equilibrium
data.
The
field
and
forestry
dissipation
data
also
confirm
that
hexazinone
is
persistent
and
mobile.
Furthermore,
the
batch
equilibrium
data
also
suggest
that
its
degradates
are
very
mobile.
Based
on
the
environmental
fate
properties
of
hexazinone
and
its
degradates,
it
can
be
concluded
they
may
be
of
concern
for
surface
water
and
groundwater
contamination..

The
following
table
summarizes
the
environmental
fate
properties
of
hexazinone,
and
the
adsorption
data
for
its
degradates:

Water
solubility
=
33,000
ppm
(25
C)
Vapor
pressure
=
2x10­
7
mm
Hg
Kow
=
15
Henry's
Law
Constant
=
2x10–
12
atm­
m3/
mol
Summary
of
Environmental
Fate
Properties
of
Hexazinone:

Study
Type/
Hexazinone
Half­
Life
Source
(MRID)

Hydrolysis
pH
5
stable
41587301
(acceptable)

pH
7
stable
41587301
(acceptable)

pH
9
stable
41587301
(acceptable)

Aqueous
Photolysis
(pH
7)
stable
41300801
(acceptable)

Soil
Photolysis
82
days
41300802
(acceptable)

Aerobic
Soil
216
days
41807401;
42635001
(acceptable)

Anaerobic
Aquatic
230
days
41807402
(acceptable)

Aerobic
Aquatic
60
days
41811801
(acceptable)
3
Summary
of
Environmental
Fate
of
Hexazinone
(continued):

Adsorption
(Mobility)
Studies
Kd
KOC
Source
(MRID)

Hexazinone
0.45
37
41528101
(acceptable)

Hexazinone
0.18
50
43621501
(supplemental)

Degradate
A­
1
0.03
27
43621501
(supplemental)

Degradate
2
0.15
45
43621501
(supplemental)

Degradate
H
0.31
51
43621501
(supplemental)

Degradate
D
0.34
59
43621501
(supplemental)

Degradate
B
0.44
90
43621501
(supplemental)

Degradate
1
0.20
122
43621501
(supplemental)

Degradate
A
0.69
176
43621501
(supplemental)

Field
Studies/
Hexazinone
Half­
Life
Source
(MRID)

Field
Dissipation
Delaware
­
123
day
(parent
was
detected
<
30
cm)
42377901
(acceptable)

Mississippi
­
154
day
(parent
was
detected
>
60­
75
cm)
42377901
(acceptable)

Forest
Dissipation
Litter
covered
soil
­
265
days
42379201
(supplemental)

Degradate
Profile
The
following
table
summarizes
the
degradates
detected
in
the
laboratory
fate
studies
and/
or
monitored
in
the
field
dissipation
and
the
groundwater
study
(i.
e.,
Degradates
A,
A­
1,
C,
D,
1,
2,
and
G3170).
It
should
be
noted
that:
C
although
Degradate
C
was
not
found
in
any
of
the
laboratory
fate
studies,
the
field
dissipation
and
the
small­
scale
prospective
groundwater
monitoring
study
monitored
this
degradate;
the
registrant
indicated
that
the
degradate
was
observed
in
aerobic
soil
metabolism
studies
with
acidic
soils;
C
Degradates
D
and
2
were
the
major
degradates
found
in
the
anaerobic
aquatic
metabolism
study;
however,
the
field
dissipation
and
the
small­
scale
prospective
groundwater
monitoring
studies
did
not
monitor
these
two
degradates.
Therefore,
the
fate
of
Degradates
D
and
2
could
not
be
assessed
under
natural
environment;
the
registrant
believed
that
both
field
studies
were
mostly
aerobic
and
the
degradates
were
unlikely
to
be
observed;
and,
4
C
the
field
dissipation
studies
did
not
monitor
the
fate
of
Degradate
G­
3170
which
was
the
degradate
detected
at
the
highest
concentrations
in
the
small­
scale
prospective
groundwater
monitoring
study
(MRID
45132801);
this
degradate
was
not
observed;
however,
in
the
aerobic
soil
metabolism
study.
C
Summary
of
Degradates
Found
in
the
Environmental
Fate
Studies
Maximum
Degradate
Concentration
(%
of
applied)
and
Time
(days)
to
Maximum
Concentration
in
Study:
Degradates
Analyzed
in
Study:

Degradate
Soil
Photo.
Aerobic
Soil
Anaerobic.
Aquatic
Aerobic
Aquatic
Field
Diss.
Ground
Water
A
(T3937)
5.5%
(365d)
yes
yes
A­
1
(G3453)
18.7%
(365d)
<10.0%
(56d)
yes
yes
B
(A3928)
10.1%
(30d)
2.3%
(365d)
<10.0%
(56d)
yes
yes
C
(T3935)
yes
yes
D
(B2838)
4.8%
(365d)
24.0%
(365d)
<10.0%
(56d)

1
((
JS472)
10.9%
(365d)
<10.0%
(56d)
yes
yes
2
(JT677)
25.0%
(365d)

G3170
yes
Background
Information
on
FIRST
FIRST
is
a
new
screening
model
designed
to
estimate
the
pesticide
concentrations
found
in
water
for
use
in
drinking
water
assessments.
It
provides
high­
end
values
on
the
concentrations
that
might
be
found
in
a
small
drinking
water
reservoir
due
to
the
use
of
pesticide.
Like
GENEEC,
the
model
previously
used
for
Tier
I
screening
level,
FIRST
is
a
single­
event
model
(one
run­
off
event),
but
can
account
for
spray
drift
from
multiple
applications.
FIRST
uses
a
Drinking
Water
Reservoir
instead
of
a
pond
as
the
standard
scenario.
The
FIRST
scenario
includes
a
427
acres
field
immediately
adjacent
to
a
13
acres
reservoir,
9
feet
deep,
with
continuous
flow
(two
turnovers
per
year).
The
pond
receives
a
5
spray
drift
event
from
each
application
plus
one
runoff
event.
The
runoff
event
moves
a
maximum
of
8%
of
the
applied
pesticide
into
the
pond.
This
amount
can
be
reduced
due
to
degradation
on
field
and
the
effect
of
binding
to
soil.
Spray
drift
is
equal
to
6.4%
of
the
applied
concentration
from
the
ground
spray
application
and
16%
for
aerial
applications.

FIRST
also
makes
adjustments
for
the
percent
crop
area.
While
FIRST
assumes
that
the
entire
watershed
would
not
be
treated,
the
use
of
a
PCA
is
still
a
screen
because
it
represents
the
highest
percentage
of
crop
cover
of
any
large
watershed
in
the
US,
and
it
assumes
that
the
entire
crop
is
being
treated.
Various
other
conservative
assumptions
of
FIRST
include
the
use
of
a
small
drinking
water
reservoir
surrounded
by
a
runoff­
prone
watershed,
the
use
of
the
maximum
use
rate,
no
buffer
zone,
and
a
single
large
rainfall.

Background
Information
on
SCI­
GROW
SCI­
GROW
provides
a
groundwater
screening
exposure
value
to
be
used
in
determining
the
potential
risk
to
human
health
from
drinking
water
contaminated
with
the
pesticide.
Since
the
SCI­
GROW
concentrations
are
likely
to
be
approached
in
only
a
very
small
percentage
of
drinking
water
sources,
i.
e.,
highly
vulnerable
aquifers,
it
is
not
appropriate
to
use
SCI­
GROW
for
national
or
regional
exposure
estimates.
SCI­
GROW
estimates
likely
groundwater
concentrations
if
the
pesticide
is
used
at
the
maximum
allowable
rate
in
areas
where
groundwater
is
exceptionally
vulnerable
to
contamination.
In
most
cases,
a
large
majority
of
the
use
area
will
have
groundwater
that
is
less
vulnerable
to
contamination
than
the
areas
used
to
derive
the
SCIGROW
estimate.

Small­
Scale
Prospective
Groundwater
Monitoring
Study
The
registrant
submitted
a
small­
scale
prospective
groundwater
monitoring
study
for
hexazinone
(MRID45132801).
Results
indicated
that
hexazinone
and
its
degradates
are
very
mobile
and
persistent.
As
indicated
earlier,
the
Degradates
D
and
2
(which
were
the
major
degradates
found
in
the
anaerobic
aquatic
metabolism
study),
were
not
monitored
in
the
small­
scale
prospective
groundwater
monitoring
studies.
No
information
about
the
fate
of
Degradates
D
and
2
under
natural
environment
is
currently
available.
The
following
table
provides
a
summary
with
the
maximum
concentrations
of
the
parent
and
its
degradates,
detected
in
the
small­
scale
prospective
groundwater
monitoring
study.
These
concentrations
(see
column
2)
were
expressed
in
parent
equivalents
(see
Column
3).
The
maximum
total
residues
of
hexazinone
and
its
degradates
detected
in
the
groundwater
study
were
41.8
ppb
(expressed
as
parent
equivalents).
6
Summary
of
Small­
Scale
Prospective
Groundwater
Monitoring
Study
Column
1
Column
2
Column
3
Chemical
Maximum
Concentration
in
Groundwater
(ppb)
Maximum
Concentration
in
Groundwater
(ppb,
expressed
as
parent
equivalent)

Parent
9.2
9.2
A­
1
(G3453)
3
2.8
B
(A3928)
7.2
7.6
C
(T3935)
1.2
1.1
1
((
JS472)
2.1
2.0
G3170
12.9
19.1
Total
Residues
(parent
equivalent)
Not
applicable
41.8
Concise
Facts
and
Results
About
the
Small­
Scale
Prospective
GroundWater
Study
Hexazinone
[Velpar
L,
2
lb
a.
i/
gallon
water­
dispersable
liquid]
was
broadcast
applied
once
at
0.75
lb
a.
i./
A
in
January
1996
onto
a
field
of
alfalfa
underlain
with
sandy
soil
in
Merced
County,
California.
The
site
is
located
within
the
recharge
area
for
a
shallow
unconfined
aquifer.
The
treated
area
consisted
of
five
100
x
300
foot
strips
separated
by
irrigation
berms,
and
the
control
area
was
100
feet
distant
and
upgradient
from
the
treated
area.
The
organic
matter
content
of
the
soil
was
#0.7%,
the
pH
was
7.5­
8.9
in
the
upper
1.5
feet,
and
there
were
no
continuous
impeding
layers.
The
first
rainfall
was
received
at
7
days
and
the
first
irrigation
event
was
at
75
days.
The
cumulative
net
daily
water
budget
was
<0.0
inches
through
19
days,
0.10
inches
at
21
days,
and
0.93
inches
at
21
days.
The
monthly
cumulative
precipitation
plus
irrigation
ranged
from
111
to
195%
of
baseline.
The
depth
of
the
water
table
ranged
from
8
to
15
feet
below
ground
surface
(bgs)
during
the
study.
Potassium
bromide
was
used
as
a
tracer;
breakthrough
into
the
shallow
groundwater
occurred
at
about
152
days
posttreatment.
Soil
(to
2
feet),
soil
pore
water
(lysimeters
at
3,
6,
9,
and
12
feet),
and
groundwater
(wells
screened
at
14­
19
and
20­
25
feet
bgs)
samples
were
collected
at
up
to
1063
days
posttreatment
and
analyzed
using
HPLC
for
hexazinone
and
six
transformation
products:
G3170,
A,
B,
C,
A1,
and
1.

Hexazinone
dissipated
from
the
upper
2
feet
of
soil
with
a
calculated
half­
life
of
25
days
(r
2
=
0.9997;
first
order
kinetics).
Hexazinone
and
its
degradates
exhibited
a
classic
pattern
of
leaching
through
the
soil
profile
and
into
the
groundwater.
Hexazinone
concentrations
above
background
(-0.05
ppb)
were
first
detected
in
pore
water
at
the
3­
foot
depth
at
60
days
posttreatment
and
in
the
6­
and
9­
foot
7
depths
at
95
days.
The
breakthrough
of
hexazinone
and
degradate
B
into
the
shallow
groundwater
occurred
at
152
days
posttreatment.
G3170
was
the
predominant
degradate
in
the
soil,
soil
pore
water,
and
groundwater;
breakthrough
into
the
shallow
groundwater
occurred
at
336
days.
In
the
individual
shallow
groundwater
wells
(14­
19
feet
bgs),
the
maximum
measured
concentrations
were
as
indicated
in
the
table
above.
In
the
individual
deep
groundwater
wells
(20­
25
feet
bgs),
the
maximum
measured
concentrations
were
2.33
ppb
for
hexazinone,
2.61
ppb
for
G3170,
1.32
ppb
for
B,
0.952
ppb
for
A1,
and
1.32
ppb
for
C.
The
average
concentrations
of
all
compounds
of
interest
in
the
shallow
and
deep
groundwater
were
below
their
Limit
of
Quantitation
(LOQ
2.0
ppb
except
4.0
ppb
for
C
and
G3170)
in
water,
except
once
at
363
days
when
hexazinone
averaged
2.02
ppb
in
the
shallow
groundwater.
There
was
a
distinct
difference
in
the
movement
of
hexazinone
through
soil
in
the
western
and
eastern
portions
of
the
site.
Hexazinone
residues
were
detected
infrequently
and
at
later
intervals
in
groundwater
in
the
eastern
portion
of
the
site,
where
soils
were
less
sandy
with
thicker
soil
lens.

Surface
Water
and
Ground
Water
Monitoring
Although
this
monitoring
study
was
not
considered
for
the
estimation
of
the
drinking
water
concentrations,
it
is
presented
for
informative
purposes,
since
it
corroborates
some
of
the
conclusions
made
earlier.
The
Board
of
Pesticides
Control
in
the
Department
of
Agriculture,
Food
and
Rural
Resources
in
the
State
of
Maine
conducted
a
statewide
assessment
to
determine
the
impact
of
highly
leachable
pesticides
(including
hexazinone,
an
herbicide
used
in
the
production
of
blueberries)
on
surface
water
and
ground
water
in
Maine.
This
assessment
crossed
a
variety
of
agricultural
and
nonagricultural
pesticide
use
sites.
Surface
water
samples
were
collected
in
Narraguagus
River
and
Pleasant
River
in
Maine.
Groundwater
samples
were
collected
from
the
wells
at
sites
with
the
following
characteristics:

C
they
contain
a
private
domestic
well,
currently
used
for
drinking
water;
C
they
were
within
1/
4
mile
of
an
active
blueberry
field
in
1994;
and
C
they
are
down
gradient
or
of
equal
elevation
with
the
blueberry
field.

Although
the
total
amounts
of
hexazinone
used
on
blueberry
in
Maine
is
very
low
(only
approximately
1%
of
the
total
sale
in
the
U.
S.),
it
was
detected
in
groundwater
and
surface
water
at
very
high
frequency
(43­
59%
of
ground
water
samples,
and
31­
90%
of
surface
water
samples;
refer
to
table
below).
Although
this
monitoring
study
is
inherently
different
than
the
ground
water
prospective
monitoring
study,
it
was
observed
that
the
maximum
concentrations
of
parent
hexazinone
observed
in
the
ground
waters
in
1998
and
1999
(i.
e.
2.15
and
1.97
ppb,
respectively),
were
similar
to
the
maximum
concentration
observed
in
the
small
scale
ground
water
monitoring
study
(i.
e.
9.2
ppb).
Degradate
B
was
also
detected
in
surface
water
and
groundwater;
however,
no
detailed
information
was
provided.
Results
are
summarized
in
the
following
table.
8
Summary
of
Monitoring
Information
from
the
Board
of
Pesticides
Control
in
the
Department
of
Agriculture,
Food
and
Rural
Resources
in
the
State
of
Maine
Year
No.
of
Samples
Collected
No.
of
Samples
with
Hexazinone
Detected
(%
of
Frequency)
Range
of
Concentrations
(ppb)

Ground
Water
1998
42
18
(43%)
0.14­
2.15
1999
22
13
(59%)
0.22­
1.97
Surface
Water
1998
36
11
(31%)
0.22­
0.94
1999
21
19
(90%)
0.13­
3.80
2000
24
21
(88%)
0.13­
2.65
2001
50
44
(88%)
0.08­
2.45
Modeling
Inputs
and
Results:
The
following
tables
summarize
the
input
values
used
in
the
model
runs
for
FIRST
and
SCIGROW,
respectively.
Fate
parameters
were
obtained
from
studies
submitted
by
the
registrant
and
modified,
if
necessary,
according
to
the
Guidance
for
Selecting
Input
Parameters
in
Modeling
the
Environmental
Fate
and
Transport
of
Pesticides,
Version
Il
(February
28,
2002).
Because
the
half­
lives
used
in
the
FIRST
model
are
extremely
long
and
the
chemicals
structures
for
degradates
are
very
similar
to
the
parent
compound
(except
for
G3170),
the
output
values
were
used
to
represent
hexazinone
residues
(including
its
degradates).
9
Environmental
Fate
Input
Parameters
for
FIRST.

Parameter
Hexazinone
Value
Source/
MRID
PC
Code
107201
OPP
Water
Solubility
(20°
C,
distilled
water)
33,000
mg/
L
registrant
Hydrolysis
Half­
Life
(pH
7)
Stable
41587301
Aerobic
Soil
Metabolism
Half­
Life
216x3=
648
days
41807401;
42635001
Aerobic
Aquatic
Metabolism
Half­
Life
60x3=
180
days
41811801
Aqueous
Photolysis
Half­
Life
(at
pH
7)
Stable
41300801
Soil
Water
Partition
Coefficient
(Kd)
0.45
41528101
Pesticide
is
Wetted­
In
No
label
PCA
0.87
OPP
Depth
of
Incorporation
(Aerial)
0.0
Label
Environmental
Fate
Input
Parameters
for
SCIGROW.

Parameter
Hexazinone
Value
Source
(MRID)

Organic
Carbon
Partition
Coefficient
(KOC)
37
41528101
Aerobic
Soil
Metabolism
Half­
Life
216
days
41807401;
42635001
Application
Information
and
Modeling
Results
for
Use
of
Hexazinone
on
Alfalfa.

Parameter
Hexazinone
value
Source
Crop
Alfalfa
label
Application
Method
Aerial
spray
label
Application
Rate
1.5
lbs
a.
i/
acre
label
Application
Frequency
once/
year
label
Incorporation
Depth
0
inches
lbel
Application
Interval
(days)
N/
A
label
10
The
modeling
results
associated
with
maximum
allowable
rate
per
year
for
representative
crops
are
presented
in
the
following
table.
Attached
to
this
memo
(Appendix
1)
are
copies
of
the
original
printouts
generated
from
FIRST
and
SCIGROW
runs.
In
addition,
the
chemical
structures
of
Hexazinone
and
its
major
degradation
products
are
presented
in
Appendix
2.

Modeling
Results
Model
Hexazinone
value
Source
FIRST
1.0
Peak
Untreated
Water
Concentration
129.8
ppb
Output
FIRST
1.0
Annual
Average
Untreated
Water
Concentration
47.1
ppb
Output
SCI­
GROW
Ground
Water
Concentration
20.2
ppb
Output
11
Appendix
1.
Printouts
of
Electronic
Outputs
Obtained
from
FIRST
and
SCIGROW
With
Use
of
Hexazinone
on
Alfalfa
at
1.5
lb
a.
i./
A
FIRST
run
RUN
No.
200
FOR
hexazinone
ON
alfalfa
*
INPUT
VALUES
*
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­

RATE
(#/
AC)
No.
APPS
&
SOIL
SOLUBIL
APPL
TYPE
%CROPPED
INCORP
ONE(
MULT)
INTERVAL
Kd
(PPM
)
(%
DRIFT)
AREA
(IN)
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­

1.500(
1.500)
1
1
.4
30000.0
AERIAL(
16.0)
87.0
.0
FIELD
AND
RESERVOIR
HALFLIFE
VALUES
(DAYS)
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­

METABOLIC
DAYS
UNTIL
HYDROLYSIS
PHOTOLYSIS
METABOLIC
COMBINED
(FIELD)
RAIN/
RUNOFF
(RESERVOIR)
(RES.­
EFF)
(RESER.)
(RESER.)
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­

648.00
2
N/
A
.00­
.00
180.00
180.00
UNTREATED
WATER
CONC
(MICROGRAMS/
LITER
(PPB))
Ver
1.0
AUG
1,
2001
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­

PEAK
DAY
(ACUTE)
ANNUAL
AVERAGE
(CHRONIC)
CONCENTRATION
CONCENTRATION
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­

129.789
47.139
SCIGROW
run
RUN
No.
300
FOR
hexazinone
INPUT
VALUES
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­

APPL
(#/
AC)
APPL.
URATE
SOIL
SOIL
AEROBIC
RATE
NO.
(#/
AC/
YR)
KOC
METABOLISM
(DAYS)
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­

1.500
1
1.500
37.0
216.0
GROUND­
WATER
SCREENING
CONCENTRATIONS
IN
PPB
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­

20.177970
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­

A=
211.000
B=
42.000
C=
2.324
D=
1.623
RILP=
5.524
F=
1.129
G=
13.452
URATE=
1.500
GWSC=
20.177970
A=
211.000
B=
55.000
C=
2.324
D=
1.740
RILP=
5.252
F=
.963
G=
9.178
URATE=
1.500
GWSC=
13.766800
12
N
N
N
O
O
CH
3
N(
CH
3
)
2
S
N
N
N
O
O
CH
3
N(
CH
3
)
2
HO
S
N
N
N
O
O
CH
3
N(
CH
3
)
2
OH
S
Appendix
2.
Chemical
Structures
of
Hexazinone
and
its
Major
Metabolites
Nomenclature
for
the
Degradates
Structure
of
Hexazinone,
A3674
Metabolite
A,
T3937
Metabolite
A1,
G3453
13
N
N
N
O
O
CH
3
NHCH
3
S
N
N
N
O
O
CH
3
N(
CH
3
)
2
O
Metabolite
C,
T3935
Metabolite
B,
A3928
Metabolite
1,
JS472
14
N
N
N
O
OH
CH
3
N(
CH
3
)
2
IN­
G3170
Nomenclature:

Metabolite
A,
T3937
3­(
4­
hydroxycyclohexyl)­
6­(
demethylamino)­
1­
methyl­
1,3,5­
triazine­
2,4(
1H,
3H)­
dione
Metabolite
A1,
G3453
3­(
2­
hydroxycyclohexyl)­
6­(
demethylamino)­
1­
methyl­
1,3,5­
triazine­
2,4(
1H,
3H)­
dione
Metabolite
C,
T3935
3­(
4­
hydroxycyclohexyl)­
6­(
methylamino)­
1­
methyl­
1,3,5­
triazine­
2,4(
1H,
3H)­
dione
Metabolite
B,
A3928
3­
cyclohexyl­
6­(
methylamino)­
1­
methyl­
1,3,5­
triazine­
2,4(
1H,
3H)­
dione
Metabolite
1,
JS472
3­(
4­
ketocyclohexyl)­
6­(
dimethylamino)­
1­
methyl­
1,3,5­
triazine­
2,4(
1H,
3H)­
dione
IN­
G3170,
N­
Demethyl
B3170
6­(
methylamino)­
1­
methyl­
1,3,5­
triazine­
2,4(
1H,
3H)
dione