United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/SR-93/102 July 1993
Project Summary
Thermal Degradation
Characteristics of
Environmentally Sensitive
Pesticide Products
Debra A. Tirey, Barry Dellinger, Wayne A. Rubey, and Philip H. Taylor
The thermal decomposition proper-
ties of the active ingredient of 16 pesti-
cides have been theoretically examined.
The parameter used to rank their sta-
bility was the temperature required for
99% destruction at a gas phase resi-
dence time of 2.0 sec under oxygen-
starved conditions (T99(2)). Experimen-
tal studies on five pesticide-related
materials were also conducted under
controlled laboratory testing.
Experimental studies of the high-tem-
perature oxidation and pyrolysis of four
key pesticide materials including the
identification and quantification of prod-
ucts of incomplete combustion (PICs)
were conducted. The four pesticides
were Aldicarb* and Phorate (both in-
secticides) and Atrazine and Alachlor
(both herbicides). These compounds
are the active ingredients of Thimet,
Temik, Aatrex-Nine-O, and Lasso II, re-
spectively. A fifth material, a polyethyl-
ene blend bag which is used as an
Atrazine container, was also examined.
The examination of the incineration
ranking among the 16 subject pesti-
cides indicated that they should be con-
sidered thermally fragile. However, each
pesticide in the controlled laboratory
testing decomposed to yield a large
number of reaction intermediates. More
intermediates were consistently pro-
duced under pyrolytic conditions. Al-
though most of the intermediates were
decomposed by 700°C, some persisted
at the maximum testing temperature,
1000°C. It appears that these materials
tested may be amenable to properly
* Mention of trade names or commercial products does
not constitute endorsement or recommendation for
use.
controlled, high-temperature incinera-
tion.
We also concluded that open burn-
ing of spent pesticide bags may not
significantly reduce their effect on the
environment and that the analytical pro-
tocols associated with the monitoring
of decomposition products from pesti-
cide materials should be further devel-
oped.
This Project Summary was developed
by EPA's Risk Reduction Engineering
Laboratory, Cincinnati, OH, to announce
key findings of the SITE program dem-
onstration that is fully documented in a
separate report (see ordering informa-
tion at back).
Introduction
Pesticides, insecticides, herbicides, and
fungicides are applied worldwide to con-
trol rodents, insects, weeds, and fungi
thought to be a direct threat to human
health or to livestock and crops raised for
human consumption. A renewed concern
over the effect of applying these chemi-
cals at an ever expanding rate, both to
the environment and to people, has, how-
ever, recently been raised.
Many studies conducted to address
these concerns have evaluated the per-
sistence and toxicology of pesticide mate-
rials in plant and animal tissues and in
soils. These studies indicate that most
pesticides themselves are fragile com-
pounds that are readily transformed in the
environment to other metabolites that may
or may not be more toxic or more persis-
tent than the parent material.
What happens, however, when pesti-
cides are thermally decomposed, as in
the case of open burning of spent bag
Printed on Recycled Paper
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materials containing trace quantities of
pesticides—a common practice for many
farmers? Or, what occurs when a pesti-
cide has been determined through "per-
sistence and toxicological" studies to no
longer be suitable for widespread use and
is suddenly banned? The method of choice
to dispose of these materials is, in many
instances, incineration. How will these
materials react upon thermal decomposi-
tion? A review of the open literature sug-
gests that only limited information is avail-
able.
In this study, the thermal decomposition
properties of the active ingredient of 16
pesticides have been theoretically exam-
ined, and experimental studies on 5 pesti-
cide-related materials were conducted. The
theoretical stability evaluations were pre-
pared with the use of available laboratory
data or with data on structurally similar
compounds in conjunction with chemical
reaction kinetic theory (Table 1). The pa-
rameter used to rank their stability was
the temperature required for 99% destruc-
tion at a gas phase residence time of 2.0
sec under oxygen-starved conditions,
T99(2). Table 1 also indicates the thermal
stability ranking and the thermal stability
class ranking of each of the pesticides
within the hierarchy of the 330 individual
compounds and 7 classes currently clas-
sified ( a ranking of 1 being most stable).
Data sheets on each pesticide are pre-
sented in the full report.
Table 1. Pesticide Thermal Stability Data
Experimental Procedures
An experimental study of the thermal
degradation characteristics of Aldicarb,
Phorate, Atrazine, and Alachlor was un-
dertaken. This included a successful atom
balance for carbon, nitrogen, sulfur, phos-
phorus, and chlorine.
Instrumentation
All experiments were performed on the
Thermal Decomposition Analytical System
(TDAS). The TDAS is a closed, in-line,
quartz flow reactor system capable of ac-
cepting a solid, liquid, or gas phase
sample, of exposing the volatilized sample
to a highly controlled thermal environment,
and then of analyzing the effluents result-
ing from this exposure.
Gas-phase samples are swept with car-
rier gas of helium through heated transfer
lines into a quartz flow reactor where con-
trolled high-temperature exposure occurs.
Mean residence times of 0.5 to 6.0 sec
may be achieved. Thermal decomposition
data may be taken over the temperature
range 200° to 1050°C.
The effluent resulting from thermal ex-
posure is swept by carrier gas to a Hewlett
Packard 5890 gas chromatograph (GC)
where it is cryogenically focused on the
head of a capillary column located inside
the GC oven. Later, the oven temperature
is raised at a specified rate and the sepa-
rated compounds eluting from the column
can then be sent to either the ion source
of an HP 5970B mass selective detector
Pesticide
Compound
DCPA
Alachlor*
Acephate
Pronamide
Carbonfuran
Triallate
Fonofos
Ethoprop
Chlorprifos
Atrazine*
Terbufos
Cyanazine
Azinphos methyl
Phorate*
Methomyl
Aldicarbr
Oxygen-Starved
Condition,
Tu(2)rC)
750
620
595
570
560
550
530
530
510
510
510
500
460
400
200
200
Stability
Ranking
105-114
185-189
207
220
226-228
231-234
237-241
237-241
249-251
249-251
249-251
253-258
266-269
276-277
318-320
318-320
Stability
Class Division'
' Ranking of 1 indicates most stable.
f Derived from experimental data obtained from this study.
(MSD), or to a flame ionization detector
(FID) located within the GC assembly.
Data acquisition and analysis for the
TDAS was done with the aid of an HP
59970 ChemStation and the accompany-
ing system software that includes an on-
line National Institute of Health/U.S. Envi-
ronmental Protection Agency (NIH-EPA)
mass spectral library. It was also neces-
sary to develop an interface between the
GC and the MSD. This interface, the in-
sertion-split, was designed as a compro-
mise between the typically used "direct-to-
source interface" and the "open-split inter-
face" and incorporated the meritorious as-
pects of each. The direct-to-source inter-
face promotes heightened sensitivity for
the mass spectrometer because effluents
from the column are deposited directly
into the source. However, having the GC
column outlet placed directly in the source
of the mass spectrometer (typically held
at 10-6 or 10-7 torr) creates a huge pres-
sure drop across the column that literally
pulls volatile compounds through the lat-
ter portion of the column without allowing
for any separation that may be attained
by interaction with the liquid stationary
phase. For these experiments, it was para-
mount that such compounds as CO2, CH4,
and the light C2 gases be separated, since
these were predicted to be major PICs.
The open-split interface provides for the
use of much larger column bores and
larger sample sizes but protects the source
of the mass spectrometer from undue wear
since much of the column effluent is di-
verted before it enters the source. One of
the chief drawbacks of this type of inter-
face is the loss of sensitivity relative to the
direct-to-source interface. Since one of the
goals of this study was to perform a mass
balance of the data, isolating and analyz-
ing as many of the products as possible
was imperative. The insertion-split inter-
face provided the best answer to these
two dilemmas.
Essentially the insertion-split interface
is a small-bore transfer tube placed within
a capillary column; the tube is surrounded
by carrier gas that is constantly being
swept away. A drawing of this interface as
it is installed in the TDAS is presented in
Figure 1. A piece of narrow-bore, fused,
silica tubing (uncoated but deactivated) is
positioned in the source of the mass spec-
trometer in much the same way that the
capillary column would be positioned if it
were direct-to-source, with a fixed length
left on the oven side of the connection nut
(can be a variable length, 10 to 20 cm).
The end of this tubing remaining in the
oven is then placed inside the outlet end
of the GC capillary column. Obviously,
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Figure 1. Close-up schematic of the insertion-split interface as it is configured in the TDAS.
attention must be paid to the inner and
outer dimensions of the two tubes. The
film thickness of the capillary column is
also important relative to gas chromato-
graph-mass spectrometer (GC-MS) opera-
tion. The ends of the transfer tubing and
the capillary column that overlap are
housed within a stainless-steel piece of
tubing fitted with inlet and outlet gas flows;
this allows a gaseous carrier to be purg-
ing the area surrounding the junction at all
times. Finally, the entire stainless-steel
miniaturized housing is firmly mounted in-
side the GC oven so as to remain station-
ary even while the GC oven fan is run-
ning.
Because there is a finite annular gap
between the outer wall of the transfer tub-
ing and the inner wall of the capillary
column and because this junction is kept
pressurized by the addition of flowing he-
lium carrier surrounding the two overlap-
ping tubes, the outlet to the capillary col-
umn now experiences approximately at-
mospheric pressure. Thus, lightweight
materials are not "pulled" through the col-
umn without being separated as with the
direct-to-source interface. Also, because
the transfer tubing is placed inside the
capillary column, transfer of sample from
column to mass spectrometer (MS) is al-
most continuous; there is no axial or open
gap in the flowpath of the column effluent
as would be experienced by the open-
split interface. This fact helps to maintain
relatively good sensitivity for this interface
despite the fact that there is some split-
ting of the sample at the column overlap
junction.
Before invoking the insertion-split inter-
face for this program, considerable devel-
opmental work went into testing the lin-
earity of splitting for lightweight as well as
for heavy materials (i.e., whether heavy
materials would be preferentially split rela-
tive to lightweight compounds because of
the axial position they would tend to oc-
cupy while traveling through the capillary
column). The insertion-split interface de-
sign used a bluff-body mixing principle at
the annular split location as a contingency
for this concern. Test results indicated that,
indeed, the bluff-body design performed
as expected; splitting of test samples con-
taining a wide-molecular range of com-
pounds was consistently the same for light,
intermediate, and heavy compounds. (The
compounds used were octane, octadec-
ane, and octacosane in cyclohexane). We
also found that for a given volumetric col-
umn flow, linear velocity, and head pres-
sure, the insertion-split interface response
was always a fixed fraction (approximately
40% to 50%) of that experienced with the
direct-to-source interface. This number
depends on the length and diameter of
the transfer tubing positioned in the source
of the mass spectrometer.
Sample Introduction
Standards of each of four pesticides
were received from the National Reposi-
tory located at Research Triangle Park,
NC. The purity of each was certified as
greater than 98% (i.e., Aldicarb 99.8%,
Phorate 98.2%, Atrazine 99.4%, and
Alachlor 99.6%). Aldicarb, Atrazine, and
Alachlor were solids at room temperature,
whereas Phorate was a viscous liquid.
The Atrazine 90 DF bag was clean—no
pesticide material had been placed in it.
Target test conditions for the four pesti-
cide active ingredients were (1) 1% mol/
mol of pesticide in carrier gas, (2) a gas
phase residence time (tr) = 2.0 sec, and
(3) two reaction atmospheres: pyrolysis at
a fuel/oxygen equivalence ratio (phi) of 10
and oxidation at phi = 0.5 (100% excess
oxygen). The Atrazine bag material was
run only under oxidative conditions.
Sample delivery for the three solid pes-
ticide active ingredients (Aldicarb, Atra-
zine, and Alachlor) in this set of experi-
ments involved dissolving the solid mate-
rial in a suitable solvent and depositing an
aliquot of the solution into a quartz
pyroprobe tube. Once the solvent had
evaporated, the tube was placed in the
platinum coil of a CDS Model 120
pyroprobe assembly (Chemical Data Sys-
tem, Inc.) that was then placed into the
insertion region of the TDAS. With the
use of temperature programming of both
the insertion region itself and/or the
pyroprobe heating coil, each pesticide was
volatilized into flowing carrier gas at a
-------
specific, reproducible rate. Separate ther-
mal gravimetric analysis (TGA) experi-
ments were performed in flowing air and
nitrogen to aid in determining the first ap-
proximation of these temperature proto-
cols.
Approximately 40 quartz tubes were
loaded with sample from the same stock
standard solution, and solvent was allowed
to evaporate. The tubes were then kept
covered at room temperature in a labora-
tory hood until just before their use. Load-
ing the quartz tubes in this manner pro-
vided the best reproducibility with regard
to sample size.
Sample delivery for the only liquid ac-
tive ingredient, Phorate, was more straight-
forward than that for the three solids. The
pure liquid (0.5 p.L) was injected into an
insertion region held isothermally at 100°C
by using a 0.5 \iL full-scale liquid syringe
fitted with a 6-in. needle.
For the polyethylene bag, approximately
2 mg of bag material was placed in a
quartz pyroprobe tube (loaded with a plug
of quartz wool to keep the piece of poly-
meric material from falling out). The tube
was then placed in the platinum coil of the
CDS pyroprobe assembly and put into the
insertion region of the TDAS. As with the
solid pesticides, temperature programming
of both the insertion region itself and the
pyroprobe heating coil volatilized the
sample into flowing carrier. A separate
TGA experiment was performed in flowing
air to aid in determining the first approxi-
mation of this temperature protocol.
The profiles generated using these
sample introduction techniques delivered
the maximum possible part per million
(mol/mol) concentration of pesticide in the
carrier gas while also delivering a suitable
sample size to the analytical system down-
stream of the reactor for adequate con-
version to products. The concentration of
active ingredients ranged from 0.1% to
0.5% mol/mol in the carrier, with the
sample sizes ranging from 77 to 500 jig.
Table 2 presents a summary of the pesti-
cide concentrations in carrier gas used in
this study, the insertion region protocols
that delivered these values, and the ac-
companying oxygen concentrations re-
quired for phi = 0.5.
Degradation of each of the three pesti-
cides was conducted under both oxygen-
deficient (fuel/oxygen equivalence ratio of
10) and oxygen-rich (fuel/oxygen equiva-
lence ratio of 0.4 to 0.5) conditions. Ap-
proximately 0.5% oxygen in helium (mol/
mol) was available for combustion in the
oxygen-deficient conditions (as determined
by actual measurement of the reaction
gas), whereas a 10% mix of oxygen in a
balance of 51% helium/39% nitrogen was
used for the oxygen-rich experiments
(these were the values obtained by mix-
ing compressed air and helium at a one-
to-one ratio vol/vol). Gas mixtures were
prepared by using a gas mixing device
developed inhouse. Residence time at tem-
peratures for all exposures regardless of
atmosphere was held constant at 2.0 sec;
the reactor temperature varied over the
range 200° to 1000°C. Experiments were
conducted at 1.23 atm. Sample was intro-
duced by using the protocols described in
preceding paragraphs.
The effluent resulting from a single re-
actor exposure (unreacted parent material
and all PICs) was directed to a 60 m, DB-
5, 0.32-mm i.d. column (J&W Scientific,
Inc.) held at -60°C with the use of liquid
nitrogen as coolant. Individual reaction
products were separated by programming
the GC oven from -60° to 290°C at 10°C/
min with a 15-min hold at -60°C and a 25-
min hold at 290°C. Detection was accom-
plished with the aid of an HP 5970B quad-
rupole mass spectrometer. The mass spec-
trometer was operated in full-scan mode
with an electron energy of 70 eV and an
electron multiplier setting of 1700. To opti-
mize detection of products, during the first
20 minutes of the GC program, the mass
range scanned was 10 to 200 amu; from
Table 2. Volatilization Parameters and Concentration of O2in the Carrier Used to Achieve Target Test Conditions
Pyrolysis
Oxidation
Compound
Aldicarb/s*
Phorate/1
Atrazine/s
Alachlor/s
Atrazine DF
bags
Insertion
Region Program
Isothermal
@20CPC
Isothermal
@10CPC
Isothermal
@275°C
Isothermal
@300°C
Isothermal
@250°C
Pyroprobe
Program
No Program
Not used
Ambient to
275°C@
2CfC/ms
hold 20s
Ambient to
30CPC@
2CPC/ms
hold 20s
Ambient to
50(fC@
20PC/ms
Cone.
(mol/mol)
4000
5000
3000
4000
Not
applicable s
% 02* in
Carrier
0.5(0.5)
0.5(0.5)
0.5(0.5)
0.5(0.5)
0.5
p/j/*
10(10)
10(10)
10(10)
10(10)
Not
applicable
%02in
Carrier
10(9)
10(7)
10(10)
10(8)
10
phi
0.5(0.5)
0.5(0.5)
0.5(0.5)
0.5(0.5)
Not
applicable
* Concenration of oxygen mol/mol in carrier required for complete combustion based upon the stoichiometric equation for the pesticide listed as: actual
(theoretical).
* Phi value for the oxidative experiments listed as: actual (theoretical).
' "s" indicates solid phase sample. "1" indicates liquid phase sample.
s No attempt was made to calculate a "concentration" or "phi" value for the polymer.
4
-------
20 to 80 min, the mass range scanned
was 10 to 500 amu. This allowed for maxi-
mum detection of light gasses during the
first part of the GC program. Quantitation
and identification of products was deter-
mined with the aid of an HP ChemStation
data system and an on-line NIH-NBS mass
spectral library as well as through manual
interpretation.
Analytical standards for observed prod-
ucts were run wherever possible to obtain
quantitative response factors. Where ob-
taining a product was either impossible,
extremely difficult, or untimely (i.e., a 6-wk
or 2-mo waiting period), analytical stan-
dards were run for compounds in the same
class or closely related in structure to the
compound of interest. These response fac-
tors were then used to estimate the re-
sponse factors for the actual products seen
in thermal decomposition experiments.
Response factors were typically obtained
from 4 or 5 point calibration curves with
some replicate points being performed
where possible.
Standards were injected into the TDAS
using the same timetable, valve switch-
ing, split ratio, and GC program as were
the pesticides. Thus, response factors gen-
erated from the curves could be used
directly to perform absolute quantification
of the area responses reported in each
data run by using the following equation:
Ng of compound detected =
Area counts of
compound/response factor
The "ng detected" values were then con-
verted with the use of molecular formulas
and molecular weights to yield mass and/
or moles of carbon, nitrogen, sulfur, phos-
phorus, and chlorine. In this way, a bal-
ance of the atoms at each temperature
could be evaluated. The compiled list of
analytical standards run for this program
and the response factors determined in
both reaction atmospheres are given in
Appendix 2 of the full report.
Results
The chromatograms generated in this
study were very complex, especially at
intermediate destruction temperatures. For
example, the thermal decomposition of
Alachlor under oxygen deficient conditions
yielded greater than 80 different PICs over
the temperature range of 275° to 1000°C.
A typical example chromatogram obtained
from the Alachlor experiments is presented
in Figure 2.
Although the excess oxygen chromato-
grams were generally less complex than
were the pyrolysis ones, a relatively large
number of products were nevertheless
detected in these experiments as well.
The number of byproducts observed for
each of the pesticides is summarized in
Table 3.
The metabolite studies found in the lit-
erature reported that these four pesticides
were not persistent in the environment
and that they were readily transformed to
other compounds. Their thermal stability
as determined under the conditions of this
study was analogous to this behavior. All
four compounds themselves were labile,
disappearing by 600°C under both pyro-
lytic and oxidative conditions. The relative
stabilities can be conveniently ranked by
the temperature required for 99% destruc-
tion for a 2.0 sec residence time (T99(2))
(see Table 4). The relative stabilities un-
der both sets of conditions in this study
were: Alachlor > Atrazine > Phorate >
Aldicarb. Aldicarb and Phorate exhibited
degradation at the lowest reactor tempera-
ture possible on the TDAS, 200°C. Be-
cause no Aldicarb was detected in the
quantitative transport run at 200°C, this
temperature was assigned as its T99(2)
value. In the case of Phorate, the T (2)
value is the temperature at which no Phor-
ate was detected in replicate runs. A more
in-depth explanation of the problems as-
sociated with running Phorate are dis-
cussed in the full report.
Interestingly, none of the pesticides dis-
played a large dependence upon reaction
atmosphere From this observation, one
can infer that the decomposition mecha-
nisms may be dominated by unimolecular
pathways. A more pictorial representation
of this can be seen in the thermal decom-
position composite curves generated for
the pesticides Alachlor and Atrazine in
Figure 3.
The specific products detected in the
decomposition studies of Aldicarb, Atra-
zine, and Alachlor in the form of weight %
yield (relative to parent) for each atmo-
sphere can be found in Tables 5 through
10 of the full report. Many of the products
detected in these experiments may be
environmentally significant.
Because of the viscosity of Phorate, the
small volume available for sampling (i.e.,
only 50 (iL in a 1.5-mL vial volume) and
the short "shelf-life" of Phorate once ex-
posed to the atmosphere, the reproduc-
ibility of injection was not good. Replicate
and triplicate injections at each reaction
condition resulted in relative standard de-
viations of as much as ± 36%. For this
reason, only qualitative analysis of the
Phorate decomposition products are listed
in Tables 11 and 12 of the final report.
There, all areas of peaks not identifiable
by their mass spectra are summed under
the heading "Unidentified."
In the full report, the results obtained
from the Atrazine bag oxidation experi-
ments are similarly presented (i.e., as
qualitative analysis of the decomposition
products). The act of volatilizing the poly-
mer in the insertion region necessarily
makes "weight % yield (relative to parent)"
type data meaningless. As with Phorate,
areas of peaks we were unable to identify
are summed under the heading "Unidenti-
fied." The products seen from this series
of experiments were the same ones ob-
served in previous studies conducted in
this laboratory in which polyethylene and
polyethylene/polypropylene blends were
thermally decomposed.
Mass balance for the pesticide experi-
ments was achieved with a fairly good
degree of success. Although some tem-
perature data points were clearly outliers,
most data points were within ± 30% of the
100% recovery mark. A listing of the atom
balances for C, N, S, or Cl where appro-
priate are presented in Appendix 3 of the
full report. Because of the high degree of
uncertainty associated with the Phorate
data, no atom balances were attempted.
Conclusions
The experimental results of this study
are very complex. Some simple conclu-
sions are, however, readily apparent.
1. Based on the stability of the parent
pesticides and their thermal
byproducts, these materials may be
amenable to properly controlled, high-
temperature incineration. The number
yields and stability of the byproducts
suggest, however, that open burning
of spent bag materials containing
pesticide residues may not sig-
nificantly reduce their effect on the
environment.
2. When compared with a previously
generated ranking of hazardous waste
incinerability, the 16 subject pesticides
(with the possible exception of DC PA)
should be considered thermally fragile
(i.e., T(2)<600°C).
S.With trie exception of Alachlor,
reaction atmosphere had almost no
effect on pesticide stability. This
suggests that the primary mechanisms
of decomposition are unimolecular
(e.g., simple bond rupture or more
complex concerted intramolecular
reactions).
4. Each pesticide decomposes to yield
a large number of reaction
intermediates. More intermediates
were consistently produced under
pyrolytic conditions. Most inter-
mediates were decomposed by
700°C; however, some persisted at
-------
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Figure 2. Example chromatogram generated for Alachlor pyrolysis, phi= 10, 4000 ppm, 2 sec residence time, 1.23 atm.
the maximum temperature in this
study, 1000°C. The most stable
organic intermediates were primarily
nitrogen-containing compounds (i.e.,
nitriles and cyanides).
5. Relatively good mass balances were
obtained for three of the pesticides;
Table 3. Number of Decomposition Byproducts
Observed
Pesticide
phi = 10 phi = 0.4 to 0.5
Aldicarb
Phorate
Atrazine
Alachlor
39 (23)'
31 (19)
63 (50)
86 (59)
22 (17)
25 (17)
47 (36)
29 (23)
( ) indicates the number identified by the
mass spectra, remainder listed as unidenti-
fied.
this suggests a reasonably complete
set of product identifications.
6. Polyethylene bag oxidation inter-
mediates did not appear to be as
environmentally significant as the
pesticide intermediates.
Recommendations
Because of the numerous byproducts
and complex chemistry observed as the
results of the thermal degradation of pes-
ticides, we make the followings recom-
mendations:
1. Additional laboratory testing of other
pesticide products suspected to be
environmentally sensitive should be
performed. Results of these studies
can be used to evaluate the
environmental effect of pesticide
burning and to guide larger scale
evaluation programs.
2. The analytical protocols associated
with the monitoring of decomposition
products from pesticide materials
should be further developed. Many of
the byproducts observed in our
Table 4. Pesticide Stability
TK(2) CC)
Pesticide
Aldicarb
Phorate
Atrazine
Alachlor
phi = 10
<400
510
620
phi = 0.4 to 0.5
200°C
<275
475
525
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102
101
100
10-1
10-2
Alachlor Oxidation
Alachlor Pyrolysis
Atrazine Oxidation
Atrazine Pyrolysis
200
300
400 500
Temperature (°C)
600
700
Figure 3. Weight % remaining curves for parent materials, Alachlor and A trazine, generated under oxidative (phi = 0.5) and pyrolytic (phi= 10.0) conditions,
2.0 sec residence time, 4000 and 3000 ppm respectively, and 1.23 aim.
laboratory evaluations are polar and
may be water soluble thus
complicating their analysis. Standard-
ized analytical techniques are not
available for many compounds that
may be environmentally significant.
3. Thermal decomposition chemistry and
kinetics of pesticides should be the
subject of further research so that the
open burning and incineration
behavior of pesticides may be better
understood. Organic nitrogen and
sulfur combustion chemistry are
largely unexplored fields of apparent
environmental significance.
4. Close coordination between laboratory
researchers and field test researchers
should be attempted to ensure that
the products identified in the laboratory
are targeted for measurement in the
field.
5.lexicological evaluation of the
observed byproducts should be done
to aid in determining the environ-
mental risk associated with open
burning and incineration of pesticides.
The full report was submitted in fulfill-
ment of Cooperative Agreement CR-
813938-01-0 by the University of Dayton
Research Institute under the sponsorship
of the U.S. Environmental Protection
Agency.
•ffV.S. GOVERNMENT HUNTING OFFICE: IM3 - 7SO-07I/MM35
-------
D. A. Tirey, B. Dellinger, W. A. Rubey, and P. H. Taylor are with the University
of Dayton Research Institute, Dayton, OH 45469-0132.
D.A. Oberackerand P.C.L Lin are the EPA Project Officers (see below).
The complete report, entitled "The Thermal Degradation Characteristics of
Environmentally Sensitive Pesticide Products," (Order No. PB93-201127;
Cost: $19.50, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
Penalty for Private Use
$300
EPA/600/SR-93/102
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
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