HomeMy WebLinkAboutSouthold Demonstration Site - Aldicarb calculations - 1983
Aldicarb Calculations
South old 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 groUJld 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 7 ppb along the Depot Lane transect UJlder 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 UJlcertainty in the decay rate assumptions,
these dates are not included in the Final Report of the Southold Demonstration
Project.
Depot Lane Transect
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 how 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 (Baier and Robbins, 1982).
Aldicarb Simulation
The Depot Lane transect was
divided into 13 areas (Figures 1 and 2),
and the farmers were surveyeu 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, 1982).
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,
CX)
It)
q
0",
"0
;\'
0",
,,~
;\'/
.9",
o~
2
"0&.."""
~IIO
0"".:>
<II.:>
""
~
i
:i
~"
~
.
.
" 8
~ ~
.
.
.
g
.
o
~
o
~
,.:
Z
."
'0
.c
;;
0
en
U
..
~
c:
:!
-
..
c:
"
...J
'0
Q.
..
C
,.: ..
.. =
- 01
" c:
01 0
u:: ..
.
"-0
.!!
~
!:
"
c:
"
-e
"
.l:!
."
..
-
.2
."
..
~
"
~
"
..
.:;
3
,..
Or.gon Rd.
Middle lmR
ROld
MIln
ROld
..
..
2
3
.
..
5
Clllchoglll
Harbor
8 9 10 11
12
13
2.
Str.,mline
/
/
/
/
/
/
MSL L.LS-
;;
.!
.2 \
.. --40 \
~
.! \
W -&0
\
-50 \
,
-100 Sill Wat., Wldg.
--__ _1____
----
-----
'-
-120
Clly Bound.,y
-
-------
_ _.i ~'~l" ~~.
_140
-150
.
3 .
,
8 a 10 11 12 13 14 15 16 17 18 19 20
Distance from North Shore 11000 It )
Flgur. 2.
Simulated aldlcarb p.lumes along the Depot Lane transect, Southold, N.Y.
Table 1 Aldicarb use on areas along the Depot Lane transect, 1975 to 1979
A1dicarb Applied
(lb active ingredient/A)
Area"
1975 1976 1977 1978 1979 Total
1 0.5 0.0 0.0 0.0 0.0 0.5
2 2.5 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 2.3 2.3 2.3 8.4
5 1.1 1.9 2.4 2.4 2.4 10.2
6 0.5 1.8 2.5 3.7 3.7 12.2
7 0.0 0.0 0.0 0.0 0.0 0.0
8 1.7 2.0 2.0 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 2.1 4.0 4.0 5.2 3.7 19.0
12 0.0 0.2 0.2 0.2 0.0 0.6
13 1.7 1.7 1.7 1.7 1.7 8.5
is shortest in the root zone where
microbial populations speed the decaying
process, and longest in the saturated zone
because 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
231 days (Kain and Steenhuis, 1982). 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 (1982). 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 2. 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 150C and pH
of 6, conditions typical of Long Island's
ground water (see Table 3). Without 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
4
the table of simulation results gives a
false impression of accuracy. For this
reason, the estimated dates of aldicarb
decay presented in Table 2 were not
retained in the final reDort for the
Southold Demonstration Site.
Assumptions Implicit in the Ground-Water
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.
Disllersion. 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 all
dispersion occurs within the unsaturated
zone before the aldicarb enters the
aquifer and that no dispersion occurs
after that.
The fact that these simplifying
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
5
Table Z Simulation Results Showing Dates When Aldicarb Would Reach Ground Water and Would Decay to Concentrations Below 7 ppb Along the Depot
Lane Transect in Southold, N. Y.
A B C D E F G
Area Year Aldicub Year All Aldicarb Average Aldicarb Number of Date When Date When
Stream Tube First Reaches Hu Reached The Concentration in Years {or Watel' Avenge Aldicarb Average Aldicarb
Number Water Table Water Table Recharge Water Starting at the Concentration Concentration
at the Water Water Table to Would Be Below Would Be Below
Table {ppbl Be Discharged 7 ppb Assuming 7 ppb Assuming
from the 3 Year Half Life 10 Year Half Life
Aquifer
1979 1979 40.8 . 1983 1983
, 1979 1984 51.6 18 1993 ZOOl
3 1979 1984 2.3.6 3Z 1989 zaaz
. 1979 1984 38.9 53 1991 ZOO9
5 1979 1984 55.7 91 1993 Z014
6 1977 1982 61.6 143 1991 2013
7 NA.. NA.. NA.. NA** NA*. NA*.
8 1976 1981 78.0 60 1992 2016
9 1976 1981 109.9 51 1993 2021
10 1976 1981 99.4 .5 1992 2019
11 1976 1981 118.4 ,9 1993 2010
1, 1977 1980 5.0 ,0 1977 1977
13 1976 1981 61.8 8 1989 1989
In these cases the contaminated water would be dischar~ed from the aquifer before the aldicarb would decay to a concentration below 7 ppb.
'II. Not computed because no aldicarb was applied to this section.
'II.. Very little aldicarb was applied to Area *12. and simulated recharge concentrations from this area are always less than 7 ppb.
Explanation of Columns in Table 2
A . Area. Stream tube, Number ~ Area numbers refer to the numbered areas and corresponding stream tubes which receive the recharge from those areas
as depicted in Figures 1 and 2.
B . Year Aldicarb First Reaches Water Table - This gives the year in which aldicar"b would have first reached the water table according to the simulation.
Note that the greater the distance between the land surface and the water table, the longer the time between when aldicarb is applied at the
surface and when it reaches the water table.
C . Year All Aldicarb Has Reached the Water Table - After this year all aldicarb is in the saturated zone and none remains in the unsaturated zone
according to the simulation.
o . Averalle Aldicarb Concentration in Recharlle Water at the Water Table - This is the average concentration of aldicarb in water entering the saturated
zone between the time when aldicarb first reaches the water table and the time when it has all reached the water table.
E . Number of Years for Water StartinlZ at the Water Table to be Discharlled from the AQuifer - This gives the time it,takes for water to travel throuih
the stream tube to the Sound or Bay. This is an upper limit on the amount of time that contaminated water could remain in tee stream tube.
F . Date When Aldicarb Concentration Would Be Below 7 JJ1)b Assuminll a 3 Year Half Life - Asauming first order decay this iives the year that the
concentration given in column 0 would decay to below the 7 ppb guideline. The number of years tbat decay would require is added to the year in
column C to get the year in column E.
G . Date When AveraR:e A1dicarb Concentration Would Be Below 7 l1Pb AssuminlZ 10 Year Half Life - The same as the calculation for tbe 3 year balf life
only now using a ten year half lile.
6
Table 3
Laboratory data on half-lifes (in days) of aldicarb and its
degradation products in water at various p3's and temperatures.
pH
Source
5.5 6.0 7.0 7.5 8 8.5
Aldicarb
150C 3240 1900 170 b
250C 266 245 266 a
Aldicarb Sulfoxide
150C 440 360 10 b
NA NA 73 c
4221 422 42 d
250C 679 161 23 a
NA 154 22 c
Aldicarb Sulfone
150C 450 125 5 b
NA 2n 52 c
1458 145 15 d
250C 420 77 10 a
NA 84 10 c
597 60 6 d
Sources:
a) Chapman and Cole (1982).
b) Hansen and Spiegel (1982).
c) Hansen et a1. (1983) (Note: Values labelled "NA" are not yet
available but will be at the conclusion of the experiments).
d) 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 standad..
Alclicarb was applied to potato farms
along the uepot Lane transect for the
fi'le years between 1975 and 1979. The
.Jlumes of aldicarb contamination will
advance though the ground water
underlying the transect, preceded and
followed by aldicarb-free water
representing recharge from before and
several years after the application period.
Individual wells would therefore in most
cases be expected to exceed the 7 ppb
sta,dard for a shorter period of time than
'i- 0 dates in our table, which represent
7
aldicarb disappearance
nlume rather than at
along its path.
in the moving
stationary sites
The transect also portrays a wor_e
th311 usual case for aldicarb in SouthalL's
ground water because approximately half
of the land along Depot Lane is devoted
to potato farl.,lng, whereas in Southold as
a whole only approximately 41 percent of
the land is used for any type of
agriculture. ~'or Eastern Long Islan-i,
faming accounts for less than 20.'''' of the
~ ntal land use.
8
REFERENCES
Baier, J.H., and S.F. Robbins. 1982.
Report on the Occurrence and
Movement of Agricultural
Chemicals in Groundwater: North.
Fork of Suffolk County. Suffolk
County Department of Health
Services, Bureau of Water
Resources.
C1apman, R.A., and C.M. Cole. 1982.
Observations on the Influence of
Water and Soil pH on the
Persistence of Insecticides. J.
Environ. Sci. Health B17(5):487-
504.
Hansen, J.L. and M.H. Spiegel. 1983.
Long Term Hydrolysis Studies of
A1dicarb Sulfoxide and A1dicarb
Sulfone. Union Carbide Corp.,
unpublished Report.
Hansen, J.L., R.R. Romine and M.H.
Spiegel. 1982. Hydrolysis Studies
of Aldicarb, Aldicarb Sulfoxide and
Aldicarb Sulfone. Environmental
Toxicology and Chemistry 2:147-
153.
;(dn, 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 Pesticide, A1dicarb, Eastern
Long Island, New York. Center for
Environmental Research, Cornell
University, Ithaca, New York.