Document ID: EPA-HQ-OPP-2004-0411-0011
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2004-12-21T05:00Z

UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
WASHINGTON,
D.
C.
20460
OFFICE
OF
PREVENTION,
PESTICIDES
AND
TOXIC
SUBSTANCES
DP
Barcodes:
D307105
PC
Code:
080801
Date:
11/
16/
2004
SUBJECT:
Drinking
Water
Exposure
Assessment
for
Proposed
Reregistration
of
Ametryn
Use
on
Corn,
Pineapple
and
Sugarcane
(
Revised)

TO:
Mark
Howard,
Chemical
Review
Manager
Reregistration
Division
William
Donovan
Health
Effects
Division
FROM:
Kevin
Costello,
Geologist,
RAPL
Environmental
Risk
Branch
IV
Environmental
Fate
and
Effects
Division
(
7507C)

THRU:
R.
David
Jones,
Ph.
D.
Senior
Scientist
Environmental
Risk
Branch
IV
Environmental
Fate
and
Effects
Division
(
7507C)

Elizabeth
Behl,
Branch
Chief
Environmental
Risk
Branch
IV
Environmental
Fate
and
Effects
Division
(
7507C)

The
eligibility
of
the
use
of
the
triazine
herbicide
ametryn
on
sugarcane,
corn
and
pineapple
for
reregistration
is
currently
under
consideration.
This
document
provides
drinking
water
estimated
concentrations
(
DWECs)
for
these
uses
for
the
human
health
dietary
risk
assessment
for
ametryn.
These
DWECs
are
derived
by
using
chemical
and
agronomic
data
as
input
to
the
simulation
models
PRZM/
EXAMS
and
SCI­
GROW.
Available
surface
water
and
ground
water
monitoring
data
are
described
to
put
the
results
of
both
the
modeling
and
monitoring
in
context.

The
potential
contaminants
of
concern
in
this
assessment
are
parent
ametryn
and
the
degradates
2­
amino­
4­
isopropylamino­
6­
methylthio­
s­
triazine
(
GS­
11354)
and
2­
ethylamino­
4­
amino­
6­
methylthio­
s­
triazine
(
GS­
11355).
These
metabolites,
which
are
­
2
­
primarily
formed
through
aerobic
soil
metabolism
of
ametryn,
were
identified
in
coordination
with
the
Health
Effects
Division
as
being
of
possible
toxicological
concern
based
on
their
structural
similarity
to
parent
ametryn.

A
complete
environmental
fate
database
is
not
available
for
these
degradates,
although
the
results
of
terrestrial
field
dissipation
studies
suggest
that
some
of
these
degradates
may
be
more
mobile
than
parent
ametryn.
In
the
absence
of
data,
the
persistence
of
ametryn
and
these
methylthio
degradates
are
considered
together
to
derive
an
aerobic
soil
metabolism
half­
life
for
"
total
toxic
residues".
In
the
absence
of
specific
mobility
data
for
all
of
the
degradates,
the
total
residues
are
assumed
to
be
as
mobile
as
parent
ametryn,
which
makes
up
the
bulk
of
the
residues
identified
in
the
aerobic
soil
metabolism
study.

Choice
of
Modeling
Scenarios
The
Tier
II
surface­
water
screening
models
PRZM
and
EXAMS
were
used
to
derive
DWECs
for
the
use
of
ametryn
on
sugarcane
and
corn
(
See
Table
1).
Modeling
scenarios
were
chosen
for
this
assessment
based
on
nationwide
distribution
of
ametryn
use.
These
scenarios
are
intended
to
represent
ametryn
use
on
the
crop
in
locations
simulated,
and
to
serve
as
surrogates
for
other
areas
in
which
those
crops
are
grown.

Table
1.
Ametryn
Use
Patterns
Crop
Max
Single
Rate
(
Lbs/
ai/
A)
Applications/
Yr
Maximum
Lbs
/
A/
Yr/

Corn
(
Field,
Sweet,
Pop)
2.0
1
2.0
Pineapple*
7.2
NS
7.2
Sugarcane
(
state
dependent)
8.0**
5
16.0
State
Use
Programs:

F
L
1.2
3
3.6
LA
2/
2.4/
2.4/
2.4/
2.4
5
11.6
TX
2/
2/
2
3
6.0
HI
7.2/
2.4/
2.4
3
12.0
PR
8/
4/
4
3
16.0
Sugarcane
Retreatment
Intervals:
30
days
where
specified.

*
Pineapple
Typical
use
in
Hawaii,
per
Pineapple
Growers
Association
of
Hawaii,
is
a
1.6
lbs
ai/
A
application
preplant
or
immediately
postplant
plus
additional
1.6
lbs
ai/
A
applications
prior
to
flower
induction;
Syngenta
supports
this
practice
within
the
7.2
lbs
ai/
A/
yr/
crop
maximum.
**
Maximum
varies
by
Application
and
by
state
NS
=
Not
Specified
on
Labeling
Ametryn
is
applied
to
corn
mostly
in
southeastern
states,
particularly
North
Carolina
and
South
Carolina,
with
some
use
in
Georgia
and
Texas.
Small
amounts
are
also
used
in
midwestern
states
(
WI,
OH,
IL).
Therefore,
corn
scenarios
for
eastern
and
­
3
­
western
North
Carolina
were
chosen
to
reflect
the
predominant
use
of
ametryn
on
corn
in
the
southeastern
United
States.

Sugarcane
use
occurs
mostly
in
Florida,
with
some
use
also
in
Hawaii,
Texas
and
Louisiana.
Standard
scenarios
are
available
for
Florida
and
Louisiana
sugarcane,
and
the
simulations
with
these
scenarios
modeled
ametryn
applications
according
to
the
labels
for
those
states.
As
described
below,
drinking
water
in
Hawaii
is
predominantly
derived
from
ground
water,
and
the
DWEC
calculated
with
the
screening
model
SCIGROW
is
recommended
for
Hawaii
sugarcane.
Surface
water
is
the
main
source
of
drinking
water
in
the
Texas
sugarcane
region;
the
DWECs
from
the
Florida
and
Louisiana
scenarios
are
recommended
as
surrogates
for
sugarcane
in
Texas.

Ametryn
is
applied
to
pineapple
in
Hawaii
and
in
Puerto
Rico.
The
ground­
water
DWEC
from
SCI­
GROW
is
recommended
for
Hawaii
pineapple.
No
PRZM
scenario
is
currently
available
for
Puerto
Rico.
The
DWECs
from
the
Florida
and
Louisiana
sugarcane
scenarios
are
recommended
as
screening
surrogates
for
pineapple
in
Puerto
Rico,
since
the
higher
concentrations
from
these
scenarios
make
them
more
conservative
surrogates
than
the
corn
scenarios,
and
because
the
weather
data
for
Louisiana
and
Florida
should
be
better
surrogates
for
Puerto
Rico
than
data
from
North
Carolina.

When
estimating
surface­
water
DWEC's,
model
output
concentrations
are
adjusted
with
percent
cropped
area
factors
(
PCAs).
The
PCAs
used
represent
the
maximum
areal
fraction
that
any
HUC­
8
watershed
in
the
United
States
is
planted
to
the
crop
of
interested.
The
PCA
for
corn
is
0.46,
which
is
consistent
with
a
HUC­
8
watershed
in
Illinois.
For
crops
which
do
not
currently
have
a
crop­
specific
PCA,
the
national
default
of
0.87
is
used,
which
represents
the
HUC­
8
watershed
with
the
greatest
areal
fraction
planted
to
any
crop
nationally.

Because
the
use
areas
for
the
three
crops
treated
with
ametryn
are
distinct
from
one
another,
they
are
unlikely
to
be
co­
located.
Therefore,
the
DWECs
for
each
crop
can
be
considered
separately
for
the
human
dietary
risk
assessment.
The
DWECs
below
for
the
scenarios
modeled
reflect
values
from
PRZM/
EXAMS
which
have
been
adjusted
with
regional
percent
cropped
area
factors.
The
regional
PCAs
used
represent
the
maximum
areal
fraction
that
any
HUC­
8
watershed
in
the
particular
major
basin
(
HUC­
2
watershed)
of
the
United
States
is
planted
to
the
crop
of
interest.

As
described
above,
the
sugarcane
simulations
for
Louisiana
and
Florida
are
recommended
as
surrogates
for
sugarcane
in
Texas
and
Puerto
Rico,
and
the
corn
simulations
in
North
Carolina
are
recommended
as
surrogates
for
the
less
common
corn
use
elsewhere
in
the
country.
The
regional
PCA
factors
for
Florida,
Louisiana
and
North
Carolina
do
not
apply
to
those
outside
areas.
Therefore,
the
DWECs
adjusted
with
the
default
national
PCAs
should
be
used
for
dietary
exposure
assessments
for
these
other
areas.
­
4
­
Modeling
Input
Parameters
Input
parameters
used
in
PRZM/
EXAMS
are
described
in
Table
2.
Input
parameters
used
in
SCI­
GROW
are
described
in
Table
3.
These
estimates
are
put
into
context
in
the
report
below
through
characterization
of
the
hydrology
of
major
ametryn
use
areas,
and
discussion
of
the
results
of
surface
water
and
ground
water
monitoring
for
ametryn
residues.

Table
2.
PRZM
(
v.
3.12.0.0)
and
EXAMS
(
v.
2.98.04)
input
parameter
values
and
results
for
ametryn
Parameter
Value
Comment
Source
Application
Rate
(
lb
a.
i./
A)
variable
see
Table
2
label
Number
of
Applications
variable
see
Table
2
label
Interval
between
Applications
(
days)
variable
see
Table
2
label
Molecular
Weight
(
g/
mol)
227.3
product
chemistry
Vapor
Pressure
(
torr)
2.74
e­
6
product
chemistry
Organic
Carbon
Partitioning
Coefficient
(
K
oc;
mL/
g)
371
Average
of
four
values
MRID
44651883
Aerobic
Soil
Metabolism
Half­
life
(
days)
(
total
toxic
residues)
273
3x
value
of
91
days
for
single
soil
MRID
41752401
Wetted
in?
no
label
Depth
of
Incorporation
(
inches)
not
incorporated
label
Method
of
Application
aerialsugarcane
ground­
corn
label
Percent
Cropped
Area
corn­
46%
sugarcane
and
pineapple­
87%
national
default
for
sugarcane
and
pineapple
EFED
policy
Solubility
in
Water
(
ppm)
1850
10
x
solubility
product
chemistry
Aerobic
Aquatic
Metabolism
Half­
life
(
days)
546
2x
aerobic
soil
no
study
submitted
­
5
­
Hydrolysis
Half­
life
@
pH
7
(
days)
stable
MRID
40885812
Aquatic
Photolysis
Half­
life
@
pH
7
(
days)
368
MRID
41169601
Table
3.
SCI­
GROW2
input
parameter
values
for
ametryn.

Parameter
Value
Source
Maximum
Application
Rate
(
lb
a.
i./
A/
application)
corn:
2
pineapple:
7.2
sugarcane:
varies
by
state
Maximum
label
rates,
Product
label
for
`
Evik
DF'
(
Syngenta)

Maximum
Number
of
Applications
per
Year
corn:
1
pineapple:
1
sugarcane:
varies
by
state
Maximum
label
rates,
Product
label
for
`
Evik
DF'
(
Syngenta)

Aerobic
Soil
Metabolism
Halflife
(
days)
91
(
total
toxic
residues)
MRID
41752401
Organic
Carbon
Partition
Coefficient
(
K
oc)
96
Input
value
is
lowest
value
of
four
reported
values
in
MRID
40995813
as
per
input
parameter
guidance
Modeling
Results
The
values
below
in
Table
4
reflect
values
from
PRZM/
EXAMS
which
have
been
adjusted
with
regional
PCA's.
These
DWEC's
should
be
used
in
the
human
dietary
risk
assessment
for
the
scenarios
modeled,
which
represent
a
substantial
portion
of
ametryn
used
in
the
United
States.

Table
4.
Surface
water
DWECs
based
on
ametryn
use
on
sugarcane
and
corn,
adjusted
for
regional
PCAs.

Scenario
Region
Regional
PCA
1­
in­
10
year
acute
(
ppb)
1­
in­
10
year
chronic
(
ppb)
30­
year
daily
average
(
ppb)

Florida
sugarcane
South
Atlantic­
Gulf
38%
96
19
12
Louisiana
sugarcane
Lower
Mississippi
85%
362
92
73
Eastern
North
Carolina
corn
South
Atlantic­
Gulf
38%
23
7.2
4.7
Western
North
Carolina
corn
Tennessee
38%
22
7.6
5.4
­
6
­
The
DWEC's
below
are
adusted
with
national­
scale
PCA's,
and
are
recommended
for
ametryn
uses
for
which
the
modeled
scenarios
serve
as
surrogates
(
such
as
Texas
sugarcane,
midwest
corn,
and
Puerto
Rico
sugarcane
and
pineapple).
The
PCAs
used
represent
the
maximum
areal
fraction
that
any
HUC­
8
watershed
in
the
United
States
is
planted
to
the
crop
of
interested.
The
PCA
for
corn
is
0.46,
which
is
consistent
with
a
HUC­
8
watershed
in
Illinois.
Since
a
crop­
specific
PCA
has
not
been
derived
for
sugarcane,
the
national
default
of
0.87
is
used,
which
represents
the
HUC­
8
watershed
with
the
greatest
areal
fraction
planted
to
any
crop.

Table
5.
Surface
water
EEC's
for
drinking
water
exposure
assessment
based
on
ametryn
use
on
sugarcane
and
corn,
adjusted
with
national
PCA's
Scenario
Surrogate
for:
1­
in­
10
year
acute
(
ppb)
1­
in­
10
year
chronic
(
ppb)
30­
year
daily
average
(
ppb)

Florida
sugarcane
Puerto
Rico
crops
219
44
27
Louisiana
sugarcane
Puerto
Rico
crops
371
94
75
Eastern
North
Carolina
corn
Midwestern
corn
28
8.8
5.7
Western
North
Carolina
corn
Midwestern
corn
26
9.2
6.6
Ground
Water
The
Tier
I
ground­
water
screening
model
SCI­
GROW
was
used
to
estimate
potential
exposure
concentrations
in
drinking
water
derived
from
ground
water.
The
SCI­
GROW
value
is
specifically
recommended
for
use
as
the
DWEC
for
ametryn
use
on
pineapple
in
Hawaii.
Pineapple
is
grown
on
the
islands
of
Oahu
and
Maui.
Ground­
water
is
the
sole
source
of
drinking
water
on
Oahu,
and
is
the
dominant
source
of
drinking
water
on
Maui.
The
Iao
and
Waihee
aquifer
areas,
on
the
eastern
side
of
West
Maui
Mountain,
are
the
principal
source
of
domestic
water
supply
for
the
island
of
Maui.
The
DWEC
calculated
with
SCI­
GROW
for
the
pineapple
use
is
9.4
ppb.

Ground
water
concentrations
shown
below
for
sugarcane
vary
for
different
states
because
application
rates
on
the
product
label
are
different
for
each
state,
as
described
in
Table
1.
­
7
­
Table
5.
Ground
water
EEC's
for
drinking
water
exposure
assessment
based
on
ametryn
use
on
sugarcane
and
corn.

Scenario
Ground­
water
concentration
(
ppb)

Florida
sugarcane
4.7
Louisiana
sugarcane
15.1
Texas
sugarcane
7.8
Puerto
Rico
sugarcane
21
Hawaii
sugarcane
15.6
Hawaii
pineapple
9.4
Corn
2.6
Surface­
Water
and
Ground­
Water
Monitoring
Since
ametryn
was
not
included
among
the
analytes
in
the
National
Water­
Quality
Assessment
NAWQA
program,
surface
water
monitoring
data
are
limited.
Some
monitoring
data
are
available,
but
the
frequency
of
the
sampling
is
not
sufficient
for
the
estimation
of
potential
acute
exposure,
nor
extensive
enough
to
allow
a
conservative
estimate
of
potential
chronic
exposure.
The
monitoring
data
and
hydrology
information
described
below
is
important,
however,
to
help
put
the
modeling
results
described
above
in
perspective.

Florida
Sugarcane
Sugarcane
in
Florida
is
grown
in
the
Everglades
Agricultural
Area,
which
is
located
to
the
south
and
east
of
Lake
Okeechobee,
and
north
of
the
Florida
Everglades
(
see
Figure
3).
The
South
Florida
Water
Management
District
(
SFWMD),
the
State
of
Florida,
and
the
United
States
Army
Corps
of
Engineers
(
USACE)
have
worked
to
maintain
the
viability
of
the
EAA
as
cropland
and
to
control
and
reduce
transport
of
agricultural
chemicals
(
particularly
phosphorus)
into
Lake
Okeechobee
and
the
Everglades.
This
is
being
accomplished
through
the
adoption
of
Best
Management
Practices
(
BMPs)
in
agriculture,
and
through
the
extensive
engineering
involved
in
the
Comprehensive
Everglades
Restoration
Plan
(
CERP).

While
the
Best
Management
Practices
are
intended
mainly
for
sediment
control
and
phosphorus
reduction,
they
may
also
serve
to
reduce
pesticide
transport.
For
instance,
farmers
in
south
Florida
pump
water
from
their
fields
during
a
normal
rainy
season
(
June
to
November)
into
drainage
canals
to
prevent
damage
to
their
crops
(
Ken
Todd,
Water
Resource
Manager
Palm
Beach
County,
personal
communication,
2002).
One
BMP
recommends
waiting
for
the
first
inch
of
rainfall
to
occur
before
pumping,
to
­
8
­
reduce
particulates
and
(
to
some
extent)
phosphorus
discharge.
BMPs
which
extend
holding
time,
or
settle
organic
matter
from
agricultural
water,
can
allow
time
for
pesticide
degradation
or
reduce
transport
of
entrained
pesticides.

Water
management
to
achieve
these
goals
is
accomplished
through
pumping
of
water
into
and
out
of
drainage
canals.
In
order
to
maintain
the
viability
of
sugarcane
in
the
EAA,
the
water
table
must
be
maintained
at
a
depth
of
at
least
6
to
12
inches
below
ground
surface.
Ground
water
pumped
from
the
EAA
is
directed
through
a
series
of
private
canals
to
four
main
public
drainage
canals
which
bring
water
out
of
the
EAA:
the
Miami
Canal,
the
North
New
River
Canal,
the
Hillsboro
Canal,
and
the
West
Palm
Beach
Canal.

The
water
from
each
of
the
public
drainage
canals
is
directed
through
constructed
wetlands
known
as
Stormwater
Treatment
Areas
(
STAs).
Each
STA
is
a
collection
of
constructed
wetlands
built
to
meet
phosphorous
loading
goals
established
by
the
CERP.
The
retarded
flow
of
water
through
the
STAs,
although
designed
to
reduce
phosphorous
levels,
should
also
reduce
the
load
of
pesticides
leaving
the
EAA
as
well
by
providing
more
time
for
the
pesticides
to
degrade.
Since
ametryn
degrades
slowly
relative
to
water
movements
in
the
canals,
and
it
does
not
bind
too
strongly
to
sediments,
this
may
be
a
less
efficient
removal
mechanism
for
ametryn
than
for
phosphorous.

The
SFWMD
includes
pesticides
among
the
analytes
it
monitors
in
surface
water
samples
taken
at
the
inflow
and
outflow
points
of
the
public
canals.
Monitoring
results
from
quarterly
sampling
between
1998
and
2003
indicate
that,
in
spite
travel
through
canals
of
the
EAA,
or
constructed
wetlands,
ametryn
is
still
detectable
in
the
water
of
the
drainage
canals.

The
concentrations
reported
in
these
monitoring
studies
are
significantly
less
than
those
resulting
from
PRZM­
EXAMS
simulation
modeling.
This
can
be
accounted
for,
in
part,
by
the
dissimilarity
of
the
PRZM/
EXAMS
reservoir
modeling
scenario
to
the
hydrology
of
the
EAA.
Some
reduction
in
concentrations
would
be
expected
from
flow
to
and
through
the
STAs.
Also,
the
monitoring
of
ametryn
by
the
SFWMD
is
for
parent
only,
and
does
not
include
the
metabolites
of
potential
toxicological
concern.

In
addition,
while
the
modeling
results
appear
to
be
a
conservative
estimate,
the
lesser
concentrations
in
the
monitoring
may
also
be
due
to
the
frequency
of
sampling
in
the
monitoring
program.
The
DWEC's
from
the
modeling
reported
above
are
the
1­
in­
10­
year
values
derived
from
modeling
of
daily
concentrations.
Quarterly
sampling
in
a
monitoring
program
is
not
sufficient
to
establish
potential
acute
drinking
water
concentrations
of
ametryn.
By
possibly
missing
peak
concentrations
of
ametryn
in
surface
water,
chronic
concentrations
that
could
be
calculated
with
the
monitoring
data
should
also
be
considered
a
rough
estimate.
­
9
­
Figure
3:
The
Everglades
Agricultural
Area
­
10
­
The
highest
concentrations
detected
in
the
quarterly
sampling
(
up
to
0.7
ppb)
occurred
during
the
winter
and
early
spring.
Ametryn
is
applied
as
a
post­
emergent
pesticide
to
sugarcane,
and
would
most
likely
be
applied
during
that
period.
Florida
sugarcane
is
planted
from
September
to
February,
although
emergence
of
the
ratoon
crops
could
lead
to
treatment
at
other
times.
The
use
closure
memo
for
ametryn
indicated
that
treatment
of
sugarcane
in
Florida
occurs
3
times
per
year,
with
a
minimum
30
day
interval.

Another
uncertainty
in
the
drinking
water
assessment
for
ametryn
use
on
Florida
sugarcane
stems
from
the
location
of
drinking
water
sources
in
relation
to
the
EAA.
Drainage
canals
from
sugarcane
fields
are
not
used
directly
for
drinking
water,
but
water
from
drainage
canals
eventually
feeds
water
bodies
used
in
southern
Florida
for
drinking
water
supply.

The
Everglades
Restoration
Plan
includes
Water
Preserve
Areas
in
the
current
Water
Conservation
Areas,
which
will
be
used
in
part
to
redirect
water
away
from
the
coast,
restoring
flow
through
the
Everglades.
The
city
of
West
Palm
Beach
derives
part
of
its
water
supply
from
the
drainage
canal
L­
8,
which
passes
through
the
Water
Conservation
Area.
Water
from
this
canal
is
diverted
to
M
Canal,
which
travels
through
25
square
miles
of
water
catchment
and
wetlands
and
into
Clear
Lake,
where
the
CWS
for
West
Palm
Beach
is
located.
The
distance
from
L­
8
to
Clear
Lake
is
about
22
miles.

Three
community
water
systems
(
CWS)
draw
from
the
southern
end
of
Lake
Okeechobee.
Water
flows
from
Lake
Okeechobee
predominantly
through
the
Caloosahatchee
River
to
the
west,
the
St.
Lucie
River
to
the
east,
and
south
through
the
EAA
toward
the
Everglades
(
South
Florida
Water
Management
District,
http://
www.
sfwmd.
gov/
org/
wrp/
wrp_
okee/
2_
wrp_
okee_
info/
maps/
homepagemap.
html).
The
South
Florida
Water
Management
District
(
SFWMD)
tightly
manages
water
in
this
area
to
direct
water
where
it
is
needed
or
for
flood
control.
This
can
at
times
also
mean
water
will
be
flushed
back
from
the
EAA
into
Lake
Okeechobee.

Louisiana
Sugarcane
According
to
the
1997
USDA
Census
of
Agriculture,
and
information
provided
by
registrant
Syngenta,
there
is
little
use
of
ametryn
on
sugarcane
in
Louisiana.
Monitoring
studies
support
the
supposition
that
concentrations
of
herbicides
in
surface
water
would
decrease
with
decreasing
use
(
Scribner,
et
al,
2000).
The
results
of
the
PRZM/
EXAMS
modeling
are
an
indication
of
the
concentrations
that
could
occur
if
the
chemical
is
used
according
to
the
label,
and
may
be
conservative
on
a
regional
scale
if
few
growers
use
ametryn
on
sugarcane
in
Louisiana.
­
11
­
A
study
of
herbicide
runoff
from
treated
fields
in
Louisiana
indicated
that
the
soils
and
weather
in
the
area
are
conducive
to
offsite
transport
(
Bengston
and
Selim,
2001).
The
study
investigated
the
runoff
from
three
types
of
applications
of
metribuzin
and
triazine
herbicide
atrazine
between
1994
to
1999.
The
application
types
were
a
high
rate
broadcast
(
1.8
lb
for
atrazine,
2.0
for
metribuzin),
a
"
standard"
application
of
half
those
rates
in
a
36­
inch
band
over
the
row,
and
a
low
rate
of
0.6
lb
and
0.7
lb,
respectively,
in
a
24­
inch
band.
Atrazine
was
applied
to
the
test
field
in
January
and
December,
1994.
The
average
rate
of
atrazine
loss
in
runoff
for
these
treatments
was
7.8,
5.7
and
5.0
percent
of
applied
active
ingredient
for
the
high,
standard
and
low
application
rates,
respectively.
Metribuzin
was
applied
in
the
spring
of
1994,
1995
and
1997,
and
had
average
loss
in
runoff
of
3.5,
2.9
and
1.2
percent
of
applied
active
ingredient
for
the
high,
standard
and
low
application
rates,
respectively.

It
is
not
clear
that
ametryn
loss
would
be
equivalent
to
that
of
atrazine,
although
both
chemicals
are
triazine
herbicides.
The
recent
interim
RED
for
atrazine
describes
it
as
being
similar
in
persistence
to
ametryn
(
aerobic
soil
metabolism
half­
life
of
"
3
to
4
months"
compared
to
84
days
for
ametryn),
but
slightly
more
mobile
(
K
d
values
<
1.0
for
sand,
sandy
loam
and
loam
soils,
2.49
on
clay).

There
are
a
number
of
community
water
supplies
which
draw
from
the
Mississippi
and
Atchafalaya
Rivers
in
the
sugarcane
production
area
of
southern
Louisiana
(
See
Figure
4).
Transport
of
pesticides
in
surface
water
is
complicated
by
leveeing
of
the
Mississippi
River
in
Louisiana
and
the
system
of
drainage
canals
in
southern
Louisiana.
While
agricultural
areas
around
tributaries
can
potentially
contribute
to
contamination
of
drinking
water
supplies,
drainage
from
fields
along
leveed
portions
of
the
Mississippi
River
may
follow
the
longer
path
through
managed
drainage
canals
to
a
potential
drinking
water
supply.

Residents
of
the
western
portion
of
the
Louisiana
sugarcane
area
draw
drinking
water
from
the
ground
water
of
the
Chicot
aquifer
of
southwest
Louisiana.
This
aquifer
is
a
"
sole
source"
aquifer
that
is
susceptible
to
contamination
(
Figure
5).
­
12
­
Figure
4:
Sugarcane
production
in
Louisiana
vs.
ground
water
as
drinking
water
supply
In
order
to
comply
with
TMDL
requirements,
the
Louisiana
Department
of
Agriculture
and
Forestry
(
LDAF)
conducted
surface
water
monitoring
in
2002
and
2003
in
the
Barataria
Basin,
a
major
sugarcane
production
area.
However,
ametryn
was
not
included
among
the
analytes.
Atrazine,
another
triazine
herbicide,
is
"
the
most
commonly
used
herbicide
in
sugarcane
culture,"
and
was
detected
at
all
10
sites
sampled.
The
highest
concentrations
found
in
monthly
sampling
were
those
most
directly
correlated
with
the
times
of
use
on
sugarcane.
­
13
­
Figure
5:
Sole
source
aquifers
of
EPA
Region
6
­
14
­
Hawaii
Pineapples
Pineapple
is
produced
primarily
on
the
islands
of
Oahu
and
Maui.
Public
water
supplies
in
Oahu
are
provided
entirely
by
ground
water.
The
deep
volcanic­
rock
aquifer
in
central
Oahu
and
Honolulu
supplies
more
than
90
percent
of
the
island's
public
water
supply
and
is
designated
as
a
Sole
Source
Drinking­
Water
Aquifer
by
the
USEPA.
The
aquifer
is
highly
permeable
and
unconfined
except
near
the
coast
(
see
map,
p.
20),
making
it
vulnerable
to
contamination
despite
depths
to
water
of
hundreds
of
feet
in
most
places.
(
NAWQA
Circular
1239).

Most
public
drinking
water
on
Maui
is
also
derived
from
ground
water.
The
USGS
reports
that
"
in
1998,
about
76
percent
of
the
ground
water
supplied
by
the
County
of
Maui
Department
of
Water
Supply
(
DWS)
to
the
island
was
from
the
Iao
aquifer".
A
portion
of
the
land
which
overlies
the
Iao
aquifer,
which
lies
on
the
flank
of
the
West
Maui
Volcano,
consists
of
sloping
alluvial
and
colluvial
plains
extending
east
from
the
mountains.
In
the
past,
sugarcane
was
grown
on
these
plains,
"
but
presently
the
land
is
used
for
macadamia
nuts,
pineapple,
papaya,
or
left
fallow"
(
Meyer
and
Presley,
2001).

Ametryn
was
included
among
the
analytes
in
a
ground­
water
monitoring
study
in
pineapple
growing
areas.
Samples
were
collected
by
the
Ciba­
Geigy
Corporation
from
1992
to
1994,
and
analyzed
for
residues
of
atrazine
and
ametryn.
Ametryn
degradates
GS­
11354,
GS­
26831
and
rarely
GS­
11355
were
also
included
as
analytes.
Ametryn
was
rarely
detected
in
ground­
water
samples,
although
the
maximum
concentration
detected
was
7.6
ppb.
Degradates
of
ametryn
were
not
detected
in
any
sample.
The
total
toxic
residue
concentration
calculated
by
SCI­
GROW
for
this
annual
application
rate
is
9.8
ppb.

Ground
water
in
Hawaii
is
particularly
vulnerable
to
contamination
from
agricultural
chemicals.
The
USGS
NAWQA
program
reports
that,
"
although
overlying
rock
is
weathered
to
depths
of
50
 
200
feet
(
Hunt,
1996),
this
soil
and
clay­
rich
overburden
does
not
prevent
downward
migration
of
chemicals
applied
or
spilled
at
land
surface."
Agricultural
soils
in
Hawaii
are
often
oxisols,
which
are
usually
well
drained,
in
spite
of
what
is
frequently
a
clay
or
clay
loam
soil
texture.

A
recent
ground­
water
monitoring
program
on
Oahu
confirmed
the
correlation
of
land
use
with
the
types
of
organic
chemicals
detected.
However,
radioisotope
dating
indicated
that
most
ground­
waters
in
the
30
public
supply
wells
sampled
were
last
in
contact
with
air
(
at
or
above
the
water
table)
sometime
between
1950
and
1980
(
Hunt,
2004).
Therefore,
detections
of
herbicides
in
present
and
former
agricultural
areas
reflect
pesticide
applications
of
several
decades
past.
Three
herbicides
introduced
to
­
15
­
the
island
since
1990
were
only
detected
in
samples
from
15
monitoring
wells
sampled
to
study
contamination
of
more
recently
recharged
ground
water.

Ametryn
was
not
included
among
the
analytes
in
this
study.
Atrazine,
however,
was
detected
in
57
percent
of
the
public
supply
wells,
and
93
percent
of
the
monitoring
wells.
Atrazine
degradates
were
also
detected
in
as
many
as
23%
of
the
supply
wells,
and
47%
of
the
monitoring
wells.
Most
other
pesticides
detected
followed
the
pattern
of
a
higher
detection
rate
in
the
shallower
monitoring
wells.
The
results
of
this
study
suggest
that
use
of
herbicides
such
as
ametryn
may
lead
to
long­
term,
lowconcentration
contamination
of
public
supply
wells
on
Oahu.

REFERENCES
Battaglin,
WA,
Thurman,
EM,
Kalkhoff,
SJ
and
Porter,
SD,
2003.
Herbicides
and
Transformation
Products
in
Surface
Waters
of
the
Midwestern
United
States.
J.
Am.
Water
Resources
Ass.,
39(
4):
743­
756.

Bengston,
R.
and
Selim,
M.,
2001
Herbicide
Losses
in
Surface
Runoff.
Louisiana
Agriculture,
vol
44,
no.
4.
http://
www.
getitgrowing.
com/
Communications/
LouisianaAgriculture/
agmag/
44_
4_
article
s/
herbicide.
asp
Brasher,
AMD,
2003.
Impacts
of
Human
Disturbances
on
Biotic
Communities
in
Hawaiian
Streams.
BioSceince
53(
11):
1052
­
1060.

Hunt,
CD,
2004.
Ground­
Water
Quality
and
its
Relation
to
Land
Use
on
Oahu,
Hawaii,
2000­
01.
USGS
WRIR
03­
4305,
Honolulu
Hawaii,
76
pp.

Klasner,
FL
and
Mikami,
CD,
2003.
Land
Use
on
the
Island
of
Oahu,
Hawaii,
1998.
USGS
WRIR
02­
4301,
Honolulu,
Hawaii,
20
pp.

Oki,
DS
and
Brasher,
AMD,
2003.
Environmental
Setting
and
the
Effects
of
Natural
and
Human­
Related
Factors
on
Water
Quality
and
Aquatic
Biota,
Oahu,
Hawaii.
USGS
WRIR
03­
4156,
Honolulu
Hawaii,
98
pp.

USDA,
2000.
Crop
Profile
for
Sugarcane
in
Hawaii.