HomeMy WebLinkAboutNYS Fertilizer & Pesticide DemoSOUTHOLD
DEMONSTRATION SITE
New York State Fertilizer and
Pesticide Demonstration Project
Aldicarb
Calculations
October
1983
Center For Envlronmimtll Research
Holliater Hall
Cornell University
Ithac~a, N.Y. 14853
Aldicarb Calculations
Southold Demonstration Site
New York State Fertilizer
and
Pesticide Demonstration Project
October 1983
Center for Environmental Research
468 Hollister Hall
Cornell University
Ithaca~ New York 14853
ALDICARB CALCULATIONS
Southold Demonstration Project
In the final report for the Southold Demonstration Site of the New York
State Fertilizer and Pesticide Demonstration Project, Table VI-2 presents the
results of our simulation of aldicarb movement below the Depot Lane Transect
in Southold, N.Y. Included are the dates when the simulation shows aldicarb
entering the ground water and the average concentrations of these recharge
plumes. The following explanation provides greater detail about the simulation,
including the many simplifying assumptions inherent in its design.
Table A-2 also provides the dates when the simulation shows aldicarb to
decay below ? ppb along the Depot Lane transect under two different half life
assumptions. These dates are meant merely to illustrate what may happen at
this site if the assumptions are correct, not to predict with any accuracy what
will occur. Because of the great uncertainty in the decay rate assumptions,
these dates are not included in the Final Report of the Southold Demonstration
Project.
Depot Lane Trzn-~ect
In 1980 the Suffolk County
Department of Health Services had a
series of geologic test holes and
observation wells drilled along Depot
Lane in Cutchogue in order to obtain
information about ho~v aldicarb and other
contaminants move through the North
Fork's aquifer. The transect cuts across
the North Fork from north to south and
runs parallel to ground-water flow in both
the northerly and southerly directions.
Private wells were sampled by the County
in the Spring of 1980, and the observation
wells were tested a year later. Aldicarb
contamination was found up to 100 feet
below the water table near the center of
the transect and at shallower depths {up
to 40 feet below the water table) at the
northern and southern extremities, with
concentrations ranging from one to 149
ppb (Baler and Robbins, 198Z).
Aldicarb Simulation
The Depot Lane transect was
divided into 13 areas (Figures 1 and Z),
and the farmers were surveyeJ~ about
their aldicarb use on fields within each of
these regions. The aldicarb application
rates for each field in an area were
averaged, and fields where no aldicarb
was applied were included in the
averaging. Results are shown in Table 1.
For our simulations, the adsorption
partition coefficient was set at 0.09 in
the root zone and at 0.0 below the root
zone, indicating that only a small percent
of the aldicarb contained in the soil water
would be adsorbed to soil particles in the
root zone, and none below this zone.
These numbers were calculated from a
linear regression relating adsorption
coefficients to soil organic matter
derived from the results of four field and
laboratory experiments (Kain and
Steenhuis, 198Z).
The greatest uncertainty in
modelling aldicarb is its rate of
attenuation in the root zone, unsaturated
zone, and saturated zone. The half-life,
or time that it takes for half of the
aldicarb to decay to nontoxic byproducts,
-120.
,.~,, , , . . · · . , ~ _ ~,;::r/ '- \
DJst~nc~ fr~ N~th Share 11000 ltl
Flpre 2.
Simulated aldlclrb ~lume8 along t~ Depot LI~ tranm~t, S~thold, N.Y.
'fable 1
Aldicarb use on areas along the Depot Lane transect, 1975 to 1979
Area
Aldicarb Applied
(lb active ingredient/A)
1 0.5 0.0 0.0 0.0 0.0 0.5
Z Z.5 0.6 1.0 1.0 1.0 6.1
3 0.4 0.7 1.1 1.1 1.1 4.4
4 0.1 1.4 Z.3 Z.3 Z.3 8.4
5 1.1 1.9 Z.4 Z.4 Z.4 10.Z
6 0.5 1.8 Z.5 3.7 3.7 1Z.Z
7 0.0 0.0 0.0 0.0 0.0 0.0
8 1.7 Z.O Z.O 2.9 2.9 11.5
9 1.6 3.7 3.7 4.6 4.6 18.2
10 2.1 2.6 2.6 3.8 3.8 14.9
11 Z.1 '4.0 4.0 5.2 3.7 19.0
lZ 0.0 O.Z 0.2 O.Z 0.0 0.6
13 1.7 1.7 1.7 1.7 1.7 8.5
1975 1976 1977 1978 1979 Total
is shortest in the root zone where
~nicrobial populations speed the decaying
process, and longest in the saturated zone
b,;cause of the lower temperatures and
low rates of microbial activity.
Unfortunately, laboratory and field
experiments on these half-lives are few,
and the results are inconclusive. A
previous review summarizing studies on
aldicarb degradation in a variety of soils
showed ranges in half-lives from one to
Z31 days (Kain and Steenhuis, 198Z). This
review indicated that for Long Island soil
types, a 50 day half-life was reasonable
for the root zone, which was assumed to
be 30 cm deep. This was increased to 100
days for the next 30 centimeters in depth
because microbial populations diminish
with increasing depth (Pacenka and
Porter, 1981). For the remainder of the
unsaturated zone, a half-life of 10 years
was used. The 50 day root zone half-life
is from Kain and Steenhuis (198Z). The
other numbers were derived by calibrating
our model with field data from a potato
field on the North Fork studied by Intera
(1980) and a deep soil core taken at the
Long Island Horticultural Research
Laboratory (unpublished data).
The simulation results indicating the
dates and concentrations of aldicarb
leaching to the ground water are shown in
Table Z. Dates of aldicarb decay are
presented for two potential half-lives,
three years and ten years, chosen
somewhat arbitrarily to represent a range
of possible half-lives for aldicarb in
ground water. Aldicarb's half-life in
ground water is highly speculative,
however, because no laboratory data are
available for its half-life at 15oc and pH
of 6, conditions typical of Long Island's
ground water (see Table 3}. ~rithout an
accurate estimate of the half-life in
ground water, any simulation of aldicarb's
disappearance has to be based on
speculation alone. Field and laboratory
research currently underway will better
define aldicarb's half-life under Long
Island conditions. Until these data
become available, simulations which
predict specific dates of disappearance
are likely to be misleading. We felt that
the table of simulation results gives a
false impression of accuracy. For this
reason, the estimated dates of aldicarb
decay presented in Table Z were not
retained in the final report for the
Southold Demonstration Site.
As~umptio~a Implicit in the C, ro~nd-~ater
Simulations
The flow system. The velocities of
the aquifer are calculated from data in
the study conducted by the Suffolk
County Department of Health Services
(Baier and Robbins, 1982). These
calculations assume that the aquifer is
composed of uniform material. Variations
in the material which undoubtedly occur
will cause the actual flows to be slightly
different. The Suffolk County
Department of Health Services estimate
that time of travel calculations would be
accurate to within + 25 percent.
Dispersion. The process of
dispersion was modelled in the
unsaturated flow where dispersion is quite
significant. In the saturated zone
dispersion was not explicitly accounted
for. Instead, a simplifying assumption
was made that all aldicarb within the
plume is evenly distributed throughout the
plume and therefore that the
concentration in the plume is uniform.
This is comparable to assuming that ali
dispersion occurs within the unsaturated
zone before the aldicarb enters the
aquifer and that no dispersion occurs
after that.
The fact that these simplifyina
assumptions only approximate reality
means that the simulation results must be
used carefully with an appreciation for
their limitations.
An additional word of caution needs
to be made about the interpretation of
the aldicarb decay dates in this table.
These dates represent the times when the
entire plume of aldicarb from each area
along the transect would be expected to
decay below 7 ppb, not the times for
Are&
Stream Tube
Number
9
C
D
F
G
Table 3
Laboratory data on half-lifes (in days) of aldicarb and its
degradation products in water at various pH's and temperatures.
pH
5.5 6.0 7.0 7.5 8 8.5
Source
Aldicarb
15oc
ZSoc
Aldicarb Sulfoxide
15oc
ZSoc
Aldicarb Sulfone
15oc
ZSOC
Sources:
a)
h)
c)
d)
3Z40 1900 170 b
- Z66 Z45 - Z66 - a
440 - 360 10 b
NA NA 73 - c
4ZZ1 4ZZ 4Z - d
679 161 23 - a
NA 154 ZZ - c
450 - 1Z5 - 5 b
NA Z7Z 52 c
1458 145 15 d
4Z0 77 10 a
NA 84 10 c
597 60 6 d
Chapman and Cole (198Z).
Hansen and Spiegel (198Z).
Hansen et al. (1983) (Note: Values labelled HNA" are not yet
available but will be at the conclusion of the experiments).
Lemley (1983) (Note: These data are extrapolated from experiments
conducted at pH's 11 to 13).
which wells at individual houses would be
expected to exceed the standard.
Aldicarb was applied to potato farms
along the Depot Lane transect for the
five years between 1975 and 1979. The
plumes of aldi :arb contamination will
advance thoug ~ the ground water
underlying the transect, preceded and
[ollowed by aldicarb-free water
representing recharge from before and
several years aft ~r the application period.
Individual wells would therefore in most
cases be expect ~.d to exceed the 7 ppb
standard for a sl-orter period of time than
tbe dates in ou' table, which represent
aldicarb disappearance in the moving
plume rather than at stationary sites
along its path.
The transect also portrays a wor~;e
than usual case for aldicarb in $outhold's
ground water because approximately half
of the la_nd along Depot Lane is devoted
to potato fart~mg~ whereas in Southold as
a whole only approximately 41 percent of
the land is used for any type of
agriculture, r'or Eastern Long Islan4,
farming accounts for less than Z0'>3 of thc
total land use.
8
REFERENCES
Baier, J.H., and S.F. Robbins. 198Z.
Report on the Occurrence and
Movement of Agricultural
Chemicals in Groundwater: North
Fork of Suffol~ County. Suffolk
County Department of Health
Services, Bu'~eau of Water
Chapman, R.A., and C.M. Cole. 198Z.
Observations ou the Influence of
Water anl .~;oil pH on the
Persistence of Insecticides. J.
Environ. Sci. Health B17(5):487-
504.
IIansen, J.L. and M.H. Spiegel. 1983.
Long Term Hydrol),sis Studies of
Aldicarb Sulfo'dde and Aldicarb
Sulfone. Uni)n Carbide Corp.,
Unpublished Report.
t-lansen, J.L., R.R. Romine and M.H.
Spiegel. 198l. Hydrolysis Studies
of Aldicarb~ Aldicarb Sulfoxide and
Aldlcarb Sulfone. Environmental
Toxicology and Chemistry l:147-
153.
Kain, D.P. and T.S. Steenhuis. 1983.
Adsorption Partition Coefficients
and Degradation Rate Constants and
Half-Lifes of Selected Pesticides
Compiled from the Literature.
Unpublished Manuscript. Cornell
University, Ithaca, New York.
Lemley, A.T. 1983. Unpublished Results.
Department of Design and
Environmental Analysis, Cornell
University, Ithaca, N.Y.
Pacenka, S. and K.S. Porter. 1981.
Preliminary Regional Assessment of
the Environmental Fate of the
Potato Pesticid% Aldicarb~ Eastern
Long Island~ New York. Center for
Environmental Research, Cornell
University, Ithaca, New York.