THE THERMAL DEGRADATION CHARACTERISTICS OF ENVIRONMENTALLY
                    SENSITIVE PESTICIDE PRODUCTS
                                  by

Debra A. T1rey, Barry Dellinger, Wayne A. Rubey, and Philip H. Taylor

               University of Dayton Research Institute
                     Environmental  Sciences  Group
                       Dayton, Ohio 45469-0132
                 Cooperative Agreement CR-813938-01-0
                         Co-Project Officers
               Donald A. Oberacker and Philip C.  L.  Lin

   Waste Minimization,  Destruction, and Disposal Research Division
                Risk Reduction Engineering Laboratory
                         Cincinnati,  OH 45268
                 RISK REDUCTION ENGINEERING  LABORATORY
                  OFFICE OF RESEARCH AND DEVELOPMENT
                 U.S. ENVIRONMENTAL PROTECTION AGENCY
                         CINCINNATI, OH 45268

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                                  DISCLAIMER


      This report has been reviewed by the Risk Reduction Engineering
Laboratory, U.S. Environmental Protection Agency, and approved for
publication.  Approval does not signify that contents necessarily reflect the
views and policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute endorsement or
recommendation for use.
                                       11

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                                   FOREWORD


      Today's rapidly developing and changing technologies and Industrial
products and practices frequently carry with them the increased generation of
materials that if improperly dealt with, can threaten both public health and
the environment.  The U.S. Environmental Protection Agency is charged by
Congress with protecting the Nation's land, air, and water resources.  Under a
mandate of national environmental laws, the agency strives to formulate and
implement actions leading to a compatible balance between human activities and
the ability of natural systems to support and nurture life.  These laws direct
the EPA to perform research to define our environmental problems, measure the
impacts, and search for solutions.

      The Risk Reduction Engineering Laboratory Is responsible for planning,
implementing, and managing of research, development, and demonstration
programs to provide an authoritative, defensible engineering basis in support
of the policies, programs, and regulations of the EPA with respect to drinking
water, wastewater, pesticides, toxic substances, solid and hazardous wastes,
and Superfund-related activities.

      This publication provides the results of theoretical and laboratory-
scale research which examined thermal breakdown behavior of a variety of
pesticides and one pesticide container  material when subjected to heat such as
during open-burning and/or intermediate conditions within an incinerator.  The
report contains  information important to the technical community concerned
with excess or waste pesticide disposal via burning or incineration.
                                     E.  Timothy Oppelt,  Director
                               Risk Reduction Engineering  Laboratory
                                       ill

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                                   ABSTRACT


      The thermal decomposition properties of the active ingredient of 16
pesticides have been theoretically examined.  The parameter used to rank their
stability was the temperature required for 99% destruction at a gas phase
residence time of 2.0 s under oxygen starved conditions.

      Experimental studies on 5 pesticide related materials were also
conducted under a controlled laboratory testing.  Experimental studies of the
high-temperature oxidation and pyrolysis of four key pesticide materials
including the identification and quantification of products of incomplete
combustion (PICs) were conducted.  The four pesticides were: Aldicarb and
Phorate (both insecticides), and Atrazine and Alachlor (both herbicides).
These compounds are the active ingredients of Thimet, Temik, Aatrex-Nine-0,
and Lasso II, respectively.  A fifth material, a polyethylene blend bag which
is used as an Atrazine container, was also examined.

      The examination of the incineration ranking among the 16 subject
pesticides indicated that they should be considered thermally fragile.
However, each pesticide in the controlled laboratory testing decomposes to
yield a large number of reaction intermediates.  More intermediates were
consistently produced under pyrolytic conditions.  Most of the intermediates
were decomposed by 700°C.  Some persisted at'the maximum temperature ,1000'C.
It appears that these materials may be amenable to properly controlled,
high-temperature incineration.  It is clear that open-burning of spent
pesticide bags may not significantly reduce their impact on the environment.
It  is  also  concluded  that  further  development of the analytical  protocols
associated with the monitoring of decomposition products from pesticide materials
should be conducted.

      This report was submitted  in fulfillment of Cooperative Agreement No. CR-
813938-01-0 by the University of Dayton Research Institute, under the sponsorship
of the U.S. Environmental Protection Agency.  This report covers a period from
October, 1990  to August, 1991,  and work was completed as of April, 1992.
                                      iv

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                                   CONTENTS


Foreword 	 111
Abstract	  1v
Figures	  v1
Tables	 v11


      1.  Introduction	.	 1

      2.  Conclusions	 4

      3.  Recommendations	 5

      4.  Experimental Procedures		 6
          4.1  Instrumentation	 6
          4.2  Sample Introduction	 9

      5.  Results and Discussion  	14

References  	29
Appendices

      1.  Pesticide Thermal Stability  Data Sheet  	31
      2.  Response Factors for  Analytical Standards  	48
      3.  Mass Balance Data 	50

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                                   FIGURES


Number                                                                  Page

  1   Close-up schematic of the Insertion-split Interface as 1t 1s
      configured 1n the IDAS 	 8

  2   Structures of the active Ingredients of the four pesticides
      Investigated 1n this study 	12

  3   Example chromatogram generated for Alachlor pyrolysls,
      phi=10, 4000 ppm, 2s residence time, 1.23 atn	17

  4   Weight % remaining curves for parent materials, Alachlor
      and Atrazine, generated under ox1dative (phi - 0.5) and
      pyrolytic (ph1= 10.0) conditions, 2.0 sec residence time,
      4000 and 3000 ppm respectively, and 1.23 atra	18
                                      v1

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                                    TABLES
Number                                                                  Page
  1   Pesticide Thermal Stabll Ity Data	3
  2   Volatilization Parameters and Concentration of 0, 1n
      the Carrier Utilized to Achieve Target Test Conditions	13
  3   Number of Decomposition By-products Observed		14
  4   Pesticide Stabllity	15
  5   Height % Yield of Products Detected in Aldicarb Oxidation	19
  6   Weight % Yield of Products Detected in Aldicarb Pyrolysis	20
  7   Weight % Yield of Products Detected in Atrazine Oxidation	21
  8   Weight % Yield of Products Detected in Atrazine Pyrolysis	22
  9   Weight % Yield of Products Detected in Alachlor Oxidation	23
 10   Weight % Yield of Products Detected in Alachlor Pyrolysis	24
 11'   Qualitative Data of Phorate Oxidation Products	26
 12   Qualitative Data of Phorate Pyrolysis Products	27
 13   Qualitative Data of Polyethylene Bag Oxidation Products	28
 3.1  Aldicarb Oxidation	50
 3.2  Aldicarb Pyrolysis	51
 3.3  Atrazine Oxidation		52
 3.4  Atrazine Pyrolysis	53
 3.5  Alachlor Oxidation	54
 3.6  Al achlor Pyrolysis	55
                                      vii

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                                   SECTION 1

                                 INTRODUCTION


      Each year hundreds of thousands of pounds of pesticides, Insecticides,
herbicides, and fungicides are applied worldwide to control rodents, Insects,
weeds and fungi thought to be a direct threat to human health, or a threat to
livestock and crops raised for human consumption (1).  There has recently been
renewed concern over the Impact of applying these chemicals at an ever
expanding rate, both to the environment and to people, whose quality of life
these chemicals have been designed to enhance.

      Many studies conducted to address these concerns have evaluated the
persistence and toxicology of pesticide materials in soils and plant and
animal tissues.  These studies Indicate that most pesticides themselves are
fragile compounds that are readily transformed in the environment to other
metabolites which may or may not be more toxic or more persistent than the
parent material (2-8).

      However, what happens when pesticides are thermally decomposed, as in
the case of open burning of spent bag materials containing trace quantities of
pesticides, as is a common practice for many farmers?  Or, what occurs when a
pesticide has been determined through  'persistence and toxicologicaV studies
to no longer be suitable for widespread use and is suddenly banned?  The
method of choice for the disposal of these materials in many Instances is
incineration.  How will these materials react upon thermal decomposition?  A
review of the open literature suggests that there is only limited Information
available  (9-12).

      Kennedy, et. al., conducted thermal degradation studies of 20 pesticide
materials  in the late 1970's:  Atrazlne,  Bromacil, Carbaryl, Dalapon, DDT,
Dicamba, Dieldrin, Diuron, Dinoseb, DSHA, Malathion, Hemagon, Paraquat,
Piclorara,  PMA, Trifluralin, 2,4-D,  2,4,5-T, Vernara, and Zineb (9).  The
weight loss of each pesticide with  increasing temperature was determined using
a muffle furnace.  Degradation studies of each pesticide were also conducted
using  sealed ampoules containing the pesticide so that the evolved gases could
be  subjected to mass spectral analysis.   However, there was no attempt to
separate the gases that entered the mass  spectrometer (i.e., all gases were
detected simultaneously),  and identification was very crude by today's
standards  since compounds  were only  identified by presence of their
characteristic fragments,  and less  than  10% of the tentatively identified
compounds  were subsequently confirmed.   In  addition, no attempt was made to
analyze  the  solid  residues that may  have  remained in the ampoule.

       Turco, et. al., examined the thermal  decomposition of 8 substituted
4,6-bi s(alkylamino)s-triazines:  2-Chloro-4,6-bis-ethylamino-s-triazine
 (S i mazi ne),  2-Chl oro-4-ethylami no-6-1sopropylami no-s-tri azi ne (Atrazi ne),
 2-Chloro-4,6-bis-isopropyl-amino-s-triazine (Propazine),
 2-Methoxy-4-ethylamino-6-tert-butyl amino-s-tri azine,
 2-Methyl-4,6-bis-i sopropyl amino-s-triazine,
 2-Hydroxy-4,6-bis-ethylamino-s-triazine,

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2-Hydroxy-4-ethylam1no-6-1sopropyl-s-tr1az1ne, and
2-Hydroxy-4,6-b1s-1sopropylamino-s-tr1azine (10).  Thermogravametric Analysis
(TGA), Differential Thermal Analysis (DTA), and  Differential Thermal
Gravimetry (DTG) techniques were used to determine the temperature at which
the onset of decomposition began, as well as the overall decomposition
profile.  This data was used to determine their Arrhenlus decomposition
kinetic parameters.  However, no attempt was made to Identify the products of
combustion.

      Duvall, et.  al., evaluated the thermal decomposition of Kepone, M1rex,
and p,p'-DDT at  1  second residence time 1n air utilizing a quartz flow reactor
(11).  Decomposition profiles were determined,, but only United products were
Identified and verified using standards.  This study showed that the
pesticides were  fragile, (i.e., decomposing to >99X by 700"C), while their
products of incomplete combustion  (PICs) were much more stable (persisting at
>900'C).

      Durig, et. al., examined the thermal decomposition of six
organophosphorus compounds:  Ethylphosphonic dichloride, Methylphosphonic
dichloride, Ethyldichlorophosphine,  Ethyldimethylphosphine,
Dimethoxymethylphosphonate,  and  Ethylphosphonic difluoride  (12).  A
pyrolysis-GC method was  used to  decompose  the compounds and a flame  ionization
detector was used to  quantitate  the  products.  Decomposition pathways were
proposed based  upon the  levels of  decomposition observed at various  pyrolysis
temperatures;  however, no  products were identified.

       In this  study,  we  have theoretically examined  the thermal decomposition
 properties of  the active ingredient  of 16  pesticides and conducted
 experimental  studies  on  5  pesticide  related materials.  The theoretical
 stability evaluations were prepared  using  available  laboratory data,  or data
 on structurally similar  compounds  in conjunction  with chemical reaction
 kinetic theory  (13).   A summary of this work is  presented  in Table  1.   The
 parameters used to rank their stability was the  temperature required for 99%
 destruction at  a gas phase residence time of 2.0 s under  oxygen  starved
 conditions, T«g(2).  This  parameter has also been used in a ranking of toxic
 organic compound  incinerability (14).   The table 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 seven
 classes currently included in the list ( a ranking of 1 being most stable).
 Data sheets on  each pesticide are presented in Appendix 1.

       This report focuses on detailed experimental studies of the
 high-temperature  oxidation and pyrolysis of four key pesticide materials
 including the identification and quantification of products of incomplete
 combustion (PICs).  The four pesticides were: Aldicarb and Phorate (both
 insecticides),  and Atrazine and Alachlor (both herbicides).  These compounds
 are  the active  ingredients of Thimet, Temik, Aatrex-Nine-0, and Lasso II,
 respectively.   A fifth material, a polyethylene blend bag which is used as an
 Atrazine  container, was also examined.  Hopefully, the knowledge gained in
 these  studies can be used to make more informed decisions concerning future
 handling  of the pesticides.

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                TABLE  1. PESTICIDE THERMAL STABILITY DATA
Compound
DCPA
Al achl or
Acephate
Pron amide
Carbonfuran
Trial! ate
Fonofos
Ethoprop
Chlorprifos
Atrazine
Terbufos
Cyanazine
Azinpho| Methyl
Phorate
Methomyl^
Aldicarb

750
620
595
570
560
550
530
530
510
510
510
500
460
400
200
200
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
mmmmm
Class Division
3
4
5
5
5
5
5
5
5
5
5
5
5
6
7
7
Derived from experimental data obtained from this study

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                                  SECTION 2

                                 CONCLUSIONS


      The experimental results of this study are very complex, full
Interpretation of which go far beyond the scope of this program.  Some simple
conclusions are, however, readily apparent.

1.  Based on the stability of the parent pesticides and their thermal
by-products, it appears that these materials may be amenable to properly
controlled, high-temperature incineration.  However, the number yields and
stability of the by-products suggest that open-burning of spent bag materials
containing pesticide residues may not significantly reduce their impact on the
environment.

2.  Based on comparison to results of a previously generated ranking of
hazardous waste incinerability, the 16 subject pesticides (with the possible
exception of DCPA) should be considered thermally fragile( i.e., 1^(2)  <
600*C).

3.  With the exception of Alachlor, there was almost no effect of reaction
atmosphere 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
interrediates. More  intermediates were consistently produced under pyrolytic
conditions.  Most of  the intermediates were decomposed by 700*C, however, some
persisted  at 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,
 suggesting a  reasonably complete set  of  product  identifications.

 6.   Polyethylene bag  oxidation intermediates  did not appear to  be  as
 environmentally significant as the  pesticide  intermediates.

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                                   SECTION 3

                                RECOMMENDATIONS

      Based on the complex chemistry observed  in these studies it would be
unwise to suggest that we can, on a theoretical basis, predict the by-products
from the open-burning of pesticides not subjected to laboratory testing.  The
myriad of potentially toxic by-products that can be formed may represent an
insurmountable challenge if Initial Identifications are attempted In field
tests prior to controlled laboratory testing.  Due to the numerous by-products
and complex chemistry observed as the results  of the thermal degradation of
pesticides, we offer the following recommendations:

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 Impact of pesticide burning and guide
larger scale evaluation programs.

2.  Further development of the analytical protocols associated with the
monitoring of decomposition products from pesticide materials should be
conducted.  Many  of the by-products observed in our laboratory evaluations are
polar and may be  water soluble thus complicating their analysis.  Standardized
analytical techniques are not available for many compounds.  This can result
in a reduced tendency to analyze for these  potentially environmentally
significant species, although analytical  techniques may already be available.

3.  Thermal decomposition chemistry and kinetics of pesticides should be the
subject of further research such 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.  Toxicological evaluation  of the observed by-products should be performed
to  aid in the determination of  the environmental  risk associated with
open-burning  and incineration of pesticides.

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                                  SECTION 4

                           EXPERIMENTAL  PROCEDURES


      An exhaustive experimental study of the thermal degradation
characteristics of four pesticides was undertaken.  This Included a successful
atom balance for carbon, nitrogen, sulfur, phosphorus and chlorine.

4.1   INSTRUMENTATION
                                                                           V
      All experiments were performed on the Thermal Decomposition Analytical
System  (TDAS) which has been described in detail elsewhere (15).  The TDAS is
a closed, in-line quartz flow reactor system capable of accepting a solid,
liquid  or gas phase sample, exposing the volatilized sample to a highly
controlled thermal environment, and then performing an analysis of the
effluents resulting from this exposure.

      Gas-phase  samples are swept with carrier  gas through heated transfer
lines into a quartz flow reactor where controlled  high temperature exposure
occurs.  Mean residence times of 0.5 to  6.0 seconds may be achieved.  Thermal
decomposition data may be taken over the temperature range 200 to 1050'C.

      The effluent resulting from thermal exposure is swept by carrier gas to
an  HP 5890 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  separated compounds eluting from the column can then be
sent to either  the ion  source of an HP 5970B mass  selective detector  (MSO), or
to  a flame  ionization detector  (FID) located within  the GC assembly.

      Data  acquisition  and  analysis for  the TDAS is  accomplished with the  aid
of an HP 59970  ChemStation  and  the accompanying system software which Includes
an  on-line  NIH-EPA mass spectral  library.  Species with molecular weights
between 16  g/mol (analytical  unit  limit) and  450 g/mol  (transport limit  of the
thermal unit)  may be  analyzed  using this system.

       In order to successfully execute this  ambitious program,  it was
necessary to develop a new Interface  between the GC  and  the MSD.  This
 interface,  the insertion-split,  was  designed as a comproalse between the
 typically used 'direct-to-source  interface'  and the  'open-split  interface',
 incorporating the meritous aspects of each.   For example,  the direct-to-source
 interface promotes heightened sensitivity for the mass  spectrometer  because
 eluents from the column are deposited directly into  the source,  just as  the
 name implies.  However, there are many limitations to this type  of interface,
 one of which directly impacts the type work discussed here.   Namely,  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 pressure drop across  the
 column which literally pulls volatile compounds through the  latter 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
 paramount that there be separation of such compounds as CO^  CH4 and  the light
 C2 gases, since these were predicted  to  be major PICs.

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      The open-split Interface provides for the use of uuch larger column
bores and larger sample sizes, but protects the source of the mass
spectrometer from undue wear and tear since much of the column effluent Is
diverted before It enters the source.  One of the chief drawbacks of this type
of Interface 1s 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, 1t was Imperative to Isolate and analyze as many of the
products as possible.  The Insertion-split Interface provided the best answer
to these two dilemmas.

      Essentially the Insertion-split Interface 1s a small-bore transfer tube
placed within a capillary column which 1s surrounded by carrier gas that Is
constantly being swept away.  A drawing of this Interface as 1t 1s 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
spectrometer 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 10-20 era).  The end of
this tubing remaining  in the  oven is then placed inside the outlet end of the
GC capillary column.  Obviously, 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  GC-MS operation.   The ends of the transfer tubing
and  the capillary column which overlap are housed within a stainless steel
piece of tubing fitted with inlet and outlet  gas flows which allow a gaseous
carrier to  be  purging  the  area  surrounding the junction at all times.
 Finally, the entire stainless steel miniaturized housing  is  firmly mounted
 inside the  GC  oven  so  as to remain  stationary even while  the GC  oven fan  is
 running.

       Because  there is a finite annular gap  between the outer  wall of  the
 transfer tubing and the inner wall  of the capillary column,  and  as this
 junction is kept pressurized by the addition of flowing  helium carrier
 surrounding the two overlapping tubes,  the outlet  to  the  capillary column now
 experiences approximately atmospheric pressure.  Thus,  light weight  materials
 are not 'pulled' through the column without being  separated as with  the
 direct-to-source interface.  Also,  because the transfer tubing is placed
 inside the capillary column,  transfer of sample fro* column to MS is almost
 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 splitting of the sample at the coluan overlap junction.

        Before invoking the  insertion-split interface for this program
 considerable developmental work went into testing the linearity of splitting
 for light weight as well as heavy  materials  (I.e., whether heavy materials
 would  be preferentially split relative to light weight compounds because of
 the axial position they would tend to occupy while traveling through the
 capillary column).  The insertion-split interface design 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  a  wide-molecular weight test sample was consistently
  the same for  light,  intermediate,  and heavy  compounds.  (The compounds used

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                                 He IN
DIRECT *
TOMS
                                                   CAPILLARY
                                                   COLUMN
Figure 1.  Close-up schematic of the  Insertion-split Interface
          as 1t 1s configured  in the IDAS.
                             8

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were octane, octadecane, and octacosane In cyclohexane).  He also found that
for a given volumetric column flow, linear velocity  and head pressure, the
Insertion-split Interface response was always  a  fixed  fraction  (approximately
40-50%) of that experienced with the d1rect-to-source  Interface.  This number
1s of course dependent upon the length and dlaraeter  of the  transfer  tubing
positioned 1n the  source of the mass spectrometer.

4.2  SAMPLE  INTRODUCTION

      Standards of each of  four pesticides were  received  from the National
Repository located at Research Triangle Park,  North  Carolina.   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, while Phorate was  a  viscous  liquid.  The
structures of all  four of the compounds are  presented in  Figure 2.   A virgin
Atrazine  90  DF bag (I.e.,  a bag which  had seen no pesticide material) was
received  from the project officer.

       Target test conditions for the four pesticide active ingredients were
 1% mol/mol of pesticide in carrier gas,  a gas phase residence time (tr 1  »  Z.O
 seconds,  and 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.  The
 stoichiometric combustion equations for each pesticide are given below.
 Equilibrium calculations using the STAIWAN thermodynaimc equilibrium code
 indicated that NO, S02, and P04 were the  thermodynamically  stable combustion
 end-products for  N,  S, and P under our experimental conditions (16).


       Aldicarb (TEMIK)

       CrHuNa&S   +  11.5 02  —>   7 C02  +  2ND +  S02 + 7H20

       Phorate  (Thimet)

       C7H1702PS3   +   16.25 02 —>  7 C02  +  3 S02   +  P04  +  8.5 H20

       Atrazine (AA-TREX  Nine 0)

        C^HajClNOa   +   18.25 02 —> 14 C02 +  NO + HC1 +  9.5 H20

        Alachlor (LASSO-II)

        C8HUC1N5 +.13.75 02  —> 8C02 + 5NO + HC1 + 6.5 H20


        Sample delivery for the three solid pesticide active ingredients
  (Aldicarb, Atrazine, and Alachlor) in this  set of experiments Involved
  dissolving the solid material 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 System, Inc. ) which was then placed  into the insertion region

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of the IDAS.  Using temperature programming of both the Insertion region
itself and/or the pyroprobe heating co11» each pesticide was volatilized Into
flowing carrier gas at a specific, reproducible rate (for a given programming
protocol).  Separate TGA experiments were performed In flowing air and
nitrogen to aid 1n determining the first approximation of these temperature
protocols.

      Before each pesticide series was  to begin,  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  laboratory hood until just prior to use.    It was determined that  loading
the quartz tubes  in this manner provided the best reproducibillty with  regard
to sample size.

       Sample delivery for the  only liquid  active  ingredient,  Phorate, was more
straightforward than  for the three solids.   0.5 ul of  the pure liquid was
injected into  an insertion  region held  isothermally at 100 C  using  a 0.5 ul
full-scale liquid syringe  fitted  with a 6 inch needle.

       The polyethylene bag was run  as follows. 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 polymeric material from falling  out).   The tube was
 then placed in the platinum coil  of the CDS  Pyroprobe assembly and placed
 into the insertion region of the TOAS.   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
 approximation of this temperature protocol.

       The profiles generated using these sample  introduction techniques
 delivered the maximum possible ppm (mol/mol) concentration of pesticide in the
 carrier  gas while also delivering a suitable sample size to the analytical
 system downstream of the reactor for adequate conversion 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 ug.  Table 2 presents a
 summary  of the pesticide concentrations in  carrier gas utilized in this study,
 the  insertion  region protocols which delivered these  values, and the
 accompanying  oxygen  concentrations required for  phi * 0.5.

        Degradation  of each  of  the three pesticides was conducted under  both
 oxygen deficient  (fuel/oxygen equivalence ratio of 10) and oxygen  rich
  (fuel/oxygen  equivalence  ratio of 0.4  - 0.5) conditions.  Approximately 0.5%
 oxygen in helium (mol/mol) was available  for combustion in the oxygen
 deficient conditions (as  determined  by actual  measurement of the reaction
 g£)? whereas 1 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 mixing
  compressed air and helium at  a one to one ratio  vol/vol).  Gas mixtures were
  prepared by utilizing a gas mixing device developed in-house.   Residence time
  at temperature for all exposures regardless of atmosphere was held  constant at
  2 0 seconds, while the reactor temperature was varied over the  range  200-
  1000'C.  Experiments were conducted at 1.23 atm.  Sample  introduction  was
                                        10

-------
accomplished using the protocols described 1n the proceeding paragraphs.

      The effluent resulting from a single reactor exposure (unreacted parent
material and all PICs) was directed to a 60 m, DB-5, 0.32 mm 1.d. column (J&W
Scientific, Inc.) held at -60*C, using liquid nitrogen as coolant.
Individual reaction products were separated by programming the GC oven from
-60 to 290*C @  10'C/min with a 15 minute hold at -60'C and a 25 minute hold at
290*C.  Detection was accomplished with the aid of an HP 59706 quadrapole mass
spectrometer.   The mass spectrometer was operated In full-scan mode with an
electron energy of 70 eV and an electron multiplier setting of 1700.  To
optimize detection of products, the mass range scanned during the first 20
minutes of the  GC program was 10-200 amu, while from 20-80 minutes the mass
range scanned was 10-500 amu.  This allowed for maximum detection of light
gasses during the first part of the GC program.  Quantitatlon and
identification  of products was performed  with the aid of an HP ChemStatlon
data system and an on-line HIH-NBS mass spectral library as well as through
manual  Interpretation.

      Analytical standards for observed products were run wherever possible to
obtain  quantitative response factors.  Where obtaining a product was either
impossible, extremely difficult, or untimely (i.e., a 6 week or 2 month
waiting period), analytical standards were run for compounds which were in the
same class, or  closely related in structure to the compound of interest.
These response  factors were then used to estimate the response 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
switching,  split ratio, and GC program as were the pesticides.  Thus, response
factors generated from the curves could be used directly to perform absolute
quantification  of the area responses  reported  in each data run using the
following  equation:

Ng of  compound  detected - Area Counts  of  compound/response factor

The 'ng detected' values were  then  converted using molecular formulas and
molecular weights to  yield mass  and/or moles of carbon, nitrogen, sulfur,
phosphorus and  chlorine.   In this way a  balance 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.
                                       11

-------
                             ?"•        1
                      CHj.S-C.CH-N-O-C-NH.CH,

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                               8

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                                  12

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                                   SECTION S

                                    RESULTS


      As expected, the chromatograms generated 1n this study were very
complex, especially at Intermediate destruction temperatures.  For example,
the thermal decomposition of Alachlor under oxygen deficient conditions
yielded > 80 different PICs over the temperature range of 275  - 1000'C.  This
was the largest number of products formed  from an Individual compound that our
laboratory has ever observed.  A typical example chroraatogram  obtained from
the Alachlor experiments 1s presented in Figure 3.

      While the excess oxygen  chromatograms were generally  less complex than
the pyrolysls ones, a relatively large  number of products were nevertheless
detected  In these  experiments  as well.  The number of by-products observed for
each of the pesticides 1s summarized in Table 3.
             TABLE 3. NUMBER OF DECOMPOSITION BY-PRODUCTS OBSERVED
               Pesticide             phi  - 10          phi  - 0.4-0.5

               Aldicarb              39 (23)                22 (17)
               Phorate               31 (19)                25 (17)
               Atrazine              63 (50)                47 (36)
               Alachlor              86 (59)                29 (23)


 (   ) Indicates the number Identified by the mass spectra, remainder listed  as
 unidentified
       The metabolite studies found in the literature reported that these four
 pesticides were not persistent in the environment and that they were readily
 transformed to other compounds (2-10).  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 pyrolytlc
 and oxidative conditions.  The relative stabilities can be conveniently ranked
 by the temperature required for 99% destruction for a 2.0 second residence
 time  (T«,(2))  (see Table 4).   The relative stabilities  under  both  sets  of
 conditions in this study were:  Alachlor > Atrazine > Phorate > Aldicarb.

       Aldicarb and Phorate exhibited degradation at the lowest reactor
 temperature possible on the TDAS,  200"C.   Because no Aldicarb was detected
 in the quantitative transport run at 200*C (I.e., it had already been
 converted to products), this temperature was assigned as its Tw(2)  value.   In

                                       14

-------
the case of Phorate, the Tw(2) value  Is the  temperature at which no Phorate
was detected 1n replicate runs.  The detection limit for this compound was
approximately 0.4 % remaining.   A more In-depth explanation of the problems
associated with running Phorate are discussed 1n the following section of this
report.
                         TABLE 4. PESTICIDE STABILITY
                         aasmmmmmmmmmmmaammmmmmmmammmm

                                         rci
            Pesticide         phi • 10          pM - 0.4-0.5

            Aldlcarb          <200                    <200
            Phorate           <400                    <275
            Atrazine            510                     475
            Alachlor            620                     525
       It Is Interesting to note  that  none  of the  pesticides  displayed  a large
 dependence upon reaction atmosphere.  This observation infers  that  the
 decomposition mechanisms may be  dominated  by uniroolecular pathways.  A more
 pictorial  representation of this can  be  seen in the thermal  decomposition
 composite curves generated for the pesticides,  Alachlor and  Atrazine,  in
 Figure 4.

       Tables 5 through 10 present the specific  products detected in the
 decomposition studies of Aldicarb, Atrazine, and  Alachlor in the fora  of
 Weight % Yield (relative to parent) for  each atmosphere.  Many of the  products
 detected in these experiments may be environmentally significant.

       Due to the viscosity of Phorate, the small  volume available for  sampling
 (i.e., only 50 ul in a 1.5 mL vial volume), and the short 'shelf-life' of
 Phorate once exposed to the atmosphere,  the reproducibility  of injection was
 not good.  Replicate and triplicate injections  at each reaction condition
 resulted in relative standard deviations of as  much as +- 36%.  For this
 reason, only qualitative analysis of the Phorate  decomposition products  are
 listed in Tables 11 and 12.  All areas of peaks that were not  identifiable by
 their mass spectra are summed under the  heading 'Unidentified'.

       Results obtained from the Atrazine bag oxidation experiments  are
 presented  in the same manner as Phorate  data in Table 13 (i.e., as  qualitative
 analysis of the decomposition products).  The act of volatilizing the polymer
 in the  insertion region necessarily makes  'Height % Yield (relative to
 parent)' type data meaningless.   As with Phorate, areas of peaks which we were
 unable to  identify are summed under the heading 'Unidentified'.  The products
 seen  from  this  series of experiments v/ere  the same ones observed in previous


                                       15

-------
studies conducted 1n this laboratory In which polyethylene and
polyethylene/polypropylene blends were thermally decomposed (17).

      Mass balance for the pesticide experiments was achieved with a fairly
good degree of success.  Some temperature data points were clearly outliers,
while most data points were within •»•- 30% of the 100% recovery mark.  A
listing of the atom balances for  C, N, S, or Cl where appropriate are
presented In Appendix 3.  Because of the high degree of uncertainty associated
with the Phorate data, no atom balances were attempted.
                                       16

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 Atrazine Oxidation


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                                        18

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           TABLE 11. QUALITATIVE DATA OF PHORATE OXIDATION PRODUCTS
                                                      Temperature CO

Compound                                              200   250   275

Phorate                                               XXXX  XXX
Ethanol                                               XXXX
Ethanthiol                                            XXXX
Methanethiol                                          XXX
1,2,4-Trithiolane                                     XXX
1,1-Thio-bis-ethane                                   XXX
l,l'-[Methylenebis(thio)]-bis-ethane                  XXX
1,3,5-Trithiane                                       XXX
0,0-Diethyl-S-pentenyl-phosphorodithioc  acid          XXXX  XXXX
0,0-Di ethyl -S-alkyl-phosphorodithioac  acid  isomers    XXXX  XXXX
1,2,4-Trithiolane                                     XXX
Ethyl -thio-acetic  acid                                XXX
Di ethyl distil fide                                      XXX
2,2'-Dithio-bis-ethanol                               XXX
Ethyl -(l-methyl-propyl)-disul fide                    XXX
Sulfur dioxide                                       X     XX    XX
Carbon monoxide                                       X     XX    XX
Carbon dioxide                                       X     XX    XX
Sulfuric acid                                        
-------
           TABLE 12. QUALITATIVE DATA OF PHORATE PYROLYSIS PRODUCTS
Compound
            Temperature CO

200   250   300   325   350   375   400
Phorate                             XXX
Ethanthiol                          XX
1,1'-[Methylenebis(thio)]-bis-ethane
Carbon dioxide                      X
Ethanol
Thiirane
Methyl-thio-ethane
Tetramethylphosphine
1,1-Thio-bis-ethane
Ethyldisulfide
Dimethyldisulfide
Heptyl-thiophene
1,3,5-Trithiane
Sulfur dioxide
Carbon disulfide
                                          X
                                          X
            XXX   XXXX  XXXX  XXX
            XXXX  XX    XXXXX
                              XX
                        XX    XX
XX    XXX
X     X
XXXX  XXXX
XX
XXX
XXX
XXX
XX
XX
XXX
                                                XXX
                                                      XX
XXX
XX

XX
                                                                        XX
                                                                        XX
 Unidentified
XXX   XXX   XX    XX
 1)     'X'  depicts an  area count  response  such  that   10,000  <  X  <  100,000
 2)     'XX' depicts an area count response such that   100,000  <  X  <  1,000,000
 3)     'XXX' depicts an area count response such that  1,000,000 < X < 10,000,000
 4)     'XXXX' depicts  an  area  count  response such  that   10,000,000 <  X <
       100,000,000
 5)     The  value   for  'Unidentified'  is   a  summation  of  the  areas  of   all
       unidentified peaks at that temperature
                                       27

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      TABLE  13. QUALITATIVE  DATA OF  POLYETHYLENE  BAG OXIDATION PRODUCTS


                                                Temperature CO

Compound                            300   400   500   600   700   750

Acetone                             XXX1'4XXX    XXX   XX
2-Oxopropanal                       X     XXX
3,5-Dipropy1-l,2,4-trioxolane       XX          XX    XX
D1hydro-2-methyl- 3(2H)furanone     XX          XX    XX
l-Acetyloxy-2-butanone              X
Pentenal                                  X
Hexenal                                   XX    XXX   XX    XX
Dihydro-2(3H)-furanone              XX    XX    XXX   XX
Dihydro-2,5-furan-dione                   XX
C6 Alkyl-cyclohex-anone             XX    XX
C7 Alkyl ketone                     XX    XXX
6-Methyl-octadecane                 XX    XX
Hexadecane                          XX          XX    XX
6-Methyl-octadecanal                XX          XX
Carbon dioxide                      XXX   XXX   XXX   XXX   XXX   XXX
Carbon monoxide                     XX    XX    XX    XX    XXX   XXX
2,5-Furandione                            XX    XX    XX
Butanedial                                XXX   XX    XX
Benzene      E                                               XXX
Unidentified5                        XXXX  XXXX  XXXX XXX


1)     'X' depicts  an  area count response  such that   10,000 <  X < 100,000
2)     'XX' depicts an area count response such  that   100,000  < X <  1,000,000
3)     'XXX'  depicts an area count response such  that   1,000,000 < X < 10,000,000
4)     'XXXX'  depicts  an  area  count response  such  that    10,000,000  <  X  <
       100,000,000
5)     The  value   for  'Unidentified'  is  a summation  of the  areas  of  all
       unidentified peaks at  that temperature
                                       28

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                                   SECTION 6

                                  REFERENCES


1.    J. E. Huff and J. K. Haseman, "Exposure to Certain Pesticides May Pose
      Real  Carcinogenic Risk,"  C & E News, pp. 33-36, January 7, 1991.

2.    N. R. Andrawes, H. W. Dorough, and D. A. Lindquist, "Degradation and
      Elimination of Temik in Rats," Journal of Economic Entomology, Vol. 60
      No. 4, pp. 979-987, August 1967.

3.    L. Ou, K. S. V. Edvardsson, and P. S. C. Rao, "Aerobic and Anaerobic
      Degradation of    Aldicarb in Soils, J. Agric. Food Chem., 33, pp.
      72-78, 1985.                                             »   » HH

4.    P. R. Boshoff and V. Pretorius, "Determination of Phorate and Its
      Metabolites by Mixed Phase Gas Chromatography," J. Agric. Food Chem ,
      Vol. 27, No. 3, pp. 626-630.

5.    S. Y. Szeto and M. J. Brown, "Gas-Liquid Chromatographic Methods for the
      Determination of Disulfoton, Phorate, Oxydemetron-methyl, and Their
      Toxic Metabolites in Asparagus Tissue and Soil," J. Agric. Food Chem.,
      30, pp. 1082-1086, 1982.

6.    L. Q. Huang, "Pesticide and Industrial Chemical Residues,"  J. Assoc
      Anal. Chem., Vol. 72, No. 2, pp. 349-354, 1989.

7.    I. Viden, Z. Rathouska', J. Davidek, and J. Hajslova,  "Use of Gas Liquid
      Chromatography/Mass Spectrometry for Triazine Herbicide Residues
      Analysis in Forage and Milk," Z. Lebensm Unters Forsch, 185, pp. 98-105,


8.    W. E. Pereira, C. E. Rostad, and T. J. Leiker, "Determination of Trace
      Levels of Herbicides and Their Degradation Products in Surface and
      Ground Waters by Gas Chromatography/Ion Trap Mass Spectrometry,"
      Analytica Chimica Acta, 228, pp. 69-75, 1990.

9.    M. V. Kennedy, B. J. Stoganovic, and F. L. Shuman, Jr., "Chemical and
      Thermal Aspects of Pesticide Disposal," J. Environ. Quality, Vol. 1, No
      1, pp.. 63-65, 1972.

10.   Turco, M. Cirstea, E. Chivulescu, E. Dragusin, "Thermal Decomposition of
      2-Substituted 4,6-bis(alkylamino) s-triazines," Rev.  Chim.  (Bucharest),
      29(2), pp. 109-13, 1978.                                             '

11.   D. S. Duvall and W. A. Rubey, "Laboratory Evaluation  of High-Temperature
      Destruction of Kepone and Related Pesticides," EPA 600/2-76-299,
      December 1976.
                                      29

-------
12.    J. R. Durig, D. F. Smith, and D. A. Barren, "Thermal Decomposition
      Studies of Some Organophosphorus Compounds," J. of Anal, and Appl.
      Pyrolysis, 16, pp. 37-48, 1989.
                                    >
13.    S. W. Benson and H. E. O'Neal, "Kinetic Data on Gas-Phase Unimolecular
      Reactions," NSRDS-NBS 21, National Bureau of Standards, Washington, D.
      C., 1970.

14.    P. H. Taylor and B. Dellinger, "Development of a Thermal Stability Based
      Index of Hazardous Waste Incinerability," Fiscal Year 1990 Report
      Prepared for US-EPA Cooperative Agreement CR-813938-01-0, C. C. Lee,
      Project Officer, October 1990.

15.    W. A. Rubey, "Design Considerations for a Thermal Decomposition
      Analytical System (TDAS)," Report prepared for U. S. Environmental
      Protection Agency, EPA-600/2-8-098, August 1980.

16.    W. C. Reynolds, "STANJAN Equilibrium Program, Version 3.0," Department
      of Mechanical Engineering, Stanford, University, Stanford, CA, 1986.

17.    D. A. Tirey, R. C. Striebich, and W. A. Rubey, "High Temperature
      Pyrolysis and Oxidation of Waste Plastics," Final Report prepared for
      Westinghouse Savannah River Laboratory, Aikon, SC, August 1990.
                                      30

-------
                                          APPENDIX 1

                         PESTICIDE THERMAL  STABILITY DATA SHEET
Empirical Formula:

Molecular Weight

IUPAC Name:
                                         ALOCHLOR
                                     (LASSO-n HERBICIDE)
             C14H20C1NO2

             270 g/mol

             2-CWoro-2',6t-dielhyl-N-(methoxy-methyl)-acetanilkle
 Structure:
                                                       -C2HS
                                                        C2HS
 Data Source

 1. Pure compound (Phi = 0.05)
 2. Pure compound (Phi = 10)

 Evaluation:
  Recommendation:
   Ranking:
T99 (2K°Q                         Comment

   525        No evidence of POHC reformation.
   620        No evidence of POHC reformation.

              Only apparent low energy unimotecular decomposition
              pathway is C-N fission.

   677        1. C-N fission, rough estimates of rate parameters yield
              log A = 16.0 1/s and Ea = 68 kcal/moL
              Ea based on C6H5CH2-NHCH3 bond strength of
              68.7 kcal/moL

              If radical chains are present, H abstraction from two ethyl
              groups may also contribute to destruction.

              C-N fission (forming resonance-stabilized intermediate)
              and H abstraction appear to be the rate-controlling
              decomposition channels. 90°C difference in observed
              and unimokcular T99 prediction indicates that significant
              radical chains contribute to destruction.

    620       Data Source No. 2.
                                                 31

-------
Empirical Formula:

Molecular Weight

IUPAC Name:

Structure:
                                            ATRAZINE
                                          (Aatrex Herbicide)
         216 g/mol

         2<;hlcro^
-------
                                           ALDICARB
                                         (Temik Insecticide)
Empirical Formula:

Molecular Weight

IUPAC Name:


Structure:
          190 g/mol

          2-Methyl-2-(melhylthio>propionaldehyde-o-
          (methylcarbamoyO-oxime
                                                           CM,

                                               CH3-S-C-CH=N-0-C-NH-CH3

                                                           CHg
 Data Source

 1.  Thermal Stability Ranking
 2. Pure compound (Phi - 0.05)
 3. Pure compound (Phi = 10)

 Evaluation:
T99(2X°Q
Comment
  Recommendation:
  Ranking:
   510    Based on C-S bond energy estimate of 59 kcal/mol and
          FY 90 Status Report estimated Arrhenlus parameters of
          log A - 16.0 1/s and Ea = 56 kcal/moL  This is now
          believed to be in error.
   <200   No evidence of POHC reformation.
   <200   No evidence of POHC reformation.

          There are at feast two tow energy unimokcular
          decomposition pathways: S-C fission and C-N fission.
          For this compound, there are 2 C-S routes and 1 C-N
          route.

   775     1. C-N fission. Rough estimates of rate parameters yield
          log A = 16.0 1/s and Ea £75 kcaWaoL
          Ea based on bond strength of CfcHsCH^NHCHa of
          68.7±1 kcal/moL  Since C-N fission for this compound
          does not form resonance-stabilized radical, Ea must be
           substantially larger than 69 kcal/moL

   673     2.  C-S fission.  D°(C2Hs-S) = 7O5 kcaVmoL Rough
           estimates of Arrhenius parameters yield tog A= 1631/1
           and Ea = 69 kcai/moL

           If radical chains are present. H abstraction from methyl
           groups may ako contribute to destruction.

           C-S fission, C-N fission, and H abstraction may contribute
           to complex decomposition mechanism. Large
           descrepancy between observed and predicted
           unimokcular T<99  suggests additional low-energy
           reaction channels arc occurring. Must analyze reaction
           products.

    <200   Data Source No. 3.
                                                33

-------
Empirical Formula:

Molecular Weight

IUPAC Name
                                            ACEPHATE
                                      (Orthene 75 WP Insecticide)
183g/mol

o^-Dirnelhyl-acetyl-phosphoranuothioate
Structure:
                                                CH3S>J>
                                                        >PNCCH3
                                                CU0'   H      3
 E>ata Source

 No literature data available

 Evaluation:
NA
                                   691
 Recommendation:
  Ranking:
600
        Comment
        NA
Only apparent tow-energy decomposition channel is C-S
fission. P-S bond may also be weak;

C-S fission. D0(C2,Hs-S) « 70 .5 kcal/mol. Rough
estimates of Arrhenius parameters yield log A = 16.0
 Ifs and Ea = 69 kcal/mol.

there is no available information to estimate the strength
of the P-S bond.

 If radical chains are present. H abstraction from methyl
 and methoxy groups may contribute to destruction,

 C-S fission, C-H fission, and H abstraction may contribute
 to complex decomposition mechanism. Estimate of
 ranking is more uncertain compared to the other
 insecticides and herbicides evaluated

 Theoretical estimate.
                                                    34

-------
Empirical Formula:

Molecular Weight

HJPACName


Structure:
                                      AZINPHOS METHYL
                                       (Guthion WP Insecticide)
       317 g/tnol

       o^-Dimelhylphosphorodithioate-s-ester-
       3^mercaptomelhyl)-lA3-benzotriaan-4{3H)-one
 Data Source

 No literature data available

 Evaluation:
  Recommendation:
  Ranking:
199 (2X°Q     Comment

NA     NA

        Low energy channels dominated by C-S fission.
        P-S bond may also be weak.

551     C-S fission, rough estimates of rate parameters
        yield tog A = 16.0 1/s and Ea » 59 kcaVmoL
        Ea based on bond strength of C6H5CH2-SCH3 of
        59.4±2 kcalAnol.

        There is no available data to estimate strength of P-S
        bond.

        If radical chains are present, H abstraction from methoxy
        group may also contribute to destruction.

        C-S fission (forming resonance-stabilized intermediate)
        and H abstraction may be rate-controlling decomposition
        channels.

 460    Theoretical estimate.
                                                   35

-------
Empirical Formula:

Molecular Weight

lUPACName


Structure:
  CARBONFURAN
  (Furadan Insecticide)

       C12H15N03

       221 g/mol

       23-Dihydro-2^-
-------
Empirical Formula:

Molecular Weight

IUPAC Name:


Structure:
                                         CHLORPRIFOS
                                         (Lorsban Insecticide)
       351 g/mol

       o,o-Diethyl-o-(3^,6-trichloro-2-pyridyl)-
       phosphorolhioate
                                                             0-P-(OC2H5)2

                                                               S
 Data Source

 No literature data available

 Evaluation:
  Recommendation:
  Ranking:
T99(2X°Q

NA     NA
                                                      Comment
        Low energy channels dominated by six-center
        elimination of ethylene (two channels)

570     Rough estimate of Arrhenius parameters yield
        log A = 12.8 1/s and Ea = 48 kcalAnoL These
        rate parameters are based on measurement of six-center
        ethylene elimination from CH3COOC2H5 as given in
        Table 3.12 of S.W. Benson Thermocbemical Kinetics.

        If radical chains are present, H abstraction from ethoxy
        group may also contribute to destruction.

        Six-center ethylene elimination is very likely to dominate
        the destruction of this compound. Small contribution
        from H abstraction may also contribute.

 510    Theoretical estimate.
                                                   37

-------
Empirical Formula:

Molecular Weight

RJPAC Name;


Structures:
            CYANAZINE
(Bladcx DF Hcrbicide/Extrazine n Herbicide)

               C9Hi3CIN6

               240 g/mol
               2-U4-CWoro-6XeihylamirKj)-s-triazin-2-yl]amino]-
               2-melhylproprionitrile
                                                                     !-C-(CH3)2
 Data Source

 No literature data available

 Evaluation:
T99(2X°Q

        NA
        Comment
 Recommendation:


 Ranking:
                                       659
NA
                Initiation dominated by C-N fission.

                For the cyanazine compound there are 2 such pathways
                with the N—C-(CH3)2 (CN) being slightly faster due to
                the formation of a resonance-stabilized radical

                Rough estimates of rate parameters yield
                log A =  16.3 1/s and Ea = 68 kcaVmoL
                Ea based on bond strength of CeHsCHz-NHCHs of
                68.7±1 kcal/mol

                If radical chains are present. H abstraction from methyl
                and ethyl groups may contribute to destruction.

                Decomposition mechanism likely dominated by C-N
                fission with a small contribution from H abstraction.
         500    Should be slightly less stable than ATRAZINE.
                                                  38

-------
Empirical Formula:

Molecular Weight:

lUPACName

Structure:
                                              DCPA
                                       (Dacthal W75 Herbicide)
               332 g/mol

               DimethyI-23,5,6-tetracnlorolerephthalate
                                                     COOCH3
                                                     COOCH3
 Data Source

 No literature data available

 Evaluation:
T99(2X°Q

        NA
       Comment
 Recommendation:
 Ranking:
NA
               Six-center molecular elimination not available as in longer
               chain phlhalates.

               If radical chains are present, H abstraction from methyl
               may contribute to destruction.

               Kinetic information on the primary decomposition
               channels for this compound can only be estimated
               by analogy with dimethylphthalate (TQ9 = 775°Q.

        750    Theoretical estimate.
                                              39

-------
Empirical Formula:

Molecular Weight

IUPAC Name

Structure:
                                             ETHOPROP
                                       (Mocap Granules Insecticide)
        242 g/mol

        o-Elhyl-s^-dipropylphosphorodithioate
                                                 C2H50-P-(S-C3H7)2

                                                          O
Data Source

No literature data available

Evaluation:
               Comment
 Recommendation:
 Ranking:
NA
                                        591
NA
        Six center elimination of ethylene only apparent low*
        energy decomposition pathway. P-S bond may also be
        weak.

        Rough estimate of Arrhenius parameters yield
        log A = 12.5 1/s and Ea = 48 kcai/mol. These
        rate parameters are based on measurement of six-center
        ethylene elimination from CH3COOC2H5 as given in
        Table 3.12 of S.W. Benson Thermochemical Kinetics.

        There is no available data to estimate strength of P-S
        bond.

        If radical chains are present. H abstraction from n-propyl
        groups may also contribute to destruction.

        Six-center ethylene elimination is very likely to dominate
        the destruction of this compound with significant
        contribution from H abstraction.
 530     Theoretical estimate.
                                                    40

-------
Empirical Formula:

Molecular Weight:

IUPAC Name

Structure:
                                             FONOFOS
                                          (Dyfonatc Insecticide)
       246 g/mol

       o-Ethyl-s-phenyl-ethyl-phosphorodilhioate
 Data Source

 No literature data available

 Evaluation:
  Recommendation:


  Ranking:
T99(2)(°Q

NA     NA
                                                        Comment
        Only apparent tow-energy decomposition channel is six-
        center elimination of ethylene. P-S bond may also be
        weak.

591     Rough estimates of Arrhenius parameters for six-center
        elimination are log A = 12.5 and Ea = 48 kcal/moL These
        rate parameters are based on measurement of six-center
        ethylene elimination from CH3COOC2H5 as given in
        Table 3.12 of S.W. Benson Thermochemical Kinetics.

        There is no available data to estimate strength of P-S
        bond.

        H abstraction from ethyl group may also contribute to
        destruction.

        Six-center ethylene elimination and H abstraction may be
        rate-controlling decomposition channels.

 530    Theoretical estimate.
                                                41

-------
Empirical Formula:

Molecular Weight

niPAC Name
                                          METHOMYL
                                         (Lannate Insecticide)
       162 g/mol

       s-Meutyl-N-{(methylcarbamoyO-oxy] -thioacetimidate
Structure:
                                                              ff
                                               CH3-C=N-O-C-N-CH3
                                                     S-CH5
 Data Source

 Thermal Stability Ranking
 FY 90 Status Report
 Evaluation:
  Recommendation:
  Ranking:
T99 (2X°Q     Comment

510     Based on C-S bond energy estimate of 59 kcal/mol and
        estimated Arrhenius parameters of log A - 16.0 1/s and
        Ea = 56 kcal/mol This is now believed to be in error.

        C-S fission (two pathways) and C-N fission are believed
        to be dominant decomposition routes.

775     1. C-N fission. Rough estimates of rate parameters yield
        log A » 16.0 IVs and Ea £75 kcal/moL
        Ea based on bond strength of CgHsCH^NHCHs of
        68.7±1 kcal/mol. Since C-N fission for this compound
        does not form resonance-stabilized radical, Ea must be
        substantially larger than 69 kcal/moL

673    2. C-S fission. D°(C2Hs-S) = 70.5 kcaVmol. Rough
        estimates of Arrhenius parameters yield log A = 163 I/*
        and Ea = 69 kcal/moL

        If radical chains are present, H abstraction from methyl
        groups may also contribute to destruction,

        C-S fission, C-N fission, aad H abstraction may contribute
        to complex decomposition mechanism. Expected to be
        slightly less stable than ALDICARB doe to the larger
        number of extractable H atoms.

 <200   Based on experimental data for ALDICARB.
                                                 42

-------
Empirical Formula:

Molecular Weight

IUPAC Name

Structure:
                                           PRONAMIDE
                                         (Kerb WP Herbicide)
       256 g/mol

       N-(l,I-
-------
Empirical Formula:

Molecular Weight

IUPAC Name

Structure:
                                           PHORATE
                                        (Thimck Insecticide)
       260 g/mol

       O,O-Diethyl-S-(ethylthio)methyl phosphorodilhioate
                                                           s
                                                           II
                                               (C2H5O)2-P-S-CH2-S-C2Hs
 Dala Source

 1.  Pure compound (Phi = 0.05)
 2.  Pure compound (Phi = 10)

 Evaluation:
  Recommendation:
  Ranking:
T99 (2X°Q     Comment

<400          No evidence of POHC reformation.
<400          No evidence of POHC reformation.

570     Possible six-center molecular elimination similar to that
        observed for esters. Rough estimates of Arrhenius
        parameters for the two degenerate channels yield
        log A - 12.8 1/s and Ea = 48 kcal/mol. These rate
        parameters are based on measurement of six-center
        ethylene elimination from CH3COOC2H5 as given in
        Table 3.12 of S.W. Benson Thermochemical Kinetics."

        Other low energy channels may include C-S fission
        (three channels) and P-S fission.

 645    D° (C2H5-S) = 70.5 kcai/mol. Rough estimates of
        Arrhenius parameters yield log A = 16.6  1/s and
        Ea = 69 kcal/mol.

        There is no available information to estimate the strength
        of the P-S bond.

        If radical chains are present. H abstraction from ethyl
        and ethoxy groups win contribute to destruction.

        Based on the very limited avaflabk data, six-center
        elimination is believed to be the dominant
        decomposition channel

 400    Theoretical estimate. Should be more stable than
         TERBUFOS due to the greater strength of C-H bonds in
         methyl versus ethyl groups
                                                 44

-------
Empirical Formula:

Molecular Weight:

IUPAC Name


Structure:
       TERBUFOS
(Counter Syslcmmic Insecticide)

          C9H2102PS3

          288 g/mol
           s-(((l,l-dimethylethyl)thio)methyl)-o,o-diethyl-
           phosphorodithioate
                                                            s
                                                            II
                                                (C2H50)2-P-S-CH2-S-C-(CH3)3
 Data Source

 No literature data available

 Evaluation:
   Recommendation:
   Ranking:
   799 (2)(°Q      Comment

   NA    NA

   570    Possible six-center molecular elimination similar to that
           observed for esters. Rough estimates of Arrhenius
           parameters for the two degenerate channels yield
           log A = 12.8 1/s and Ea = 48 kcalAnoL These rate
           parameters are based on measurement of six-center
           elhylene elimination from CH3COOC2H5 as given in
           Table 3.12 of S.W. Benson Thermochemical Kinetics."

           Other low energy channels may include C-S fission (two
           channels) and P-S fission.

    645     D° (C2H5-S) = 70.3 kcal/mol.  Rough estimates of
            Arrhenius parameters yield log A = 16.6 1/s and
            Ea = 69 kcal/mol.

            There is no available information to estimate the strength
            of the P-S bond.

            If radical chains are present, H abstraction from methyl
            and ethoxy groups will contribute to destruction.

            Based on the very limited available data, six-center
            elimination is believed to be the dominant
            decomposition channel

     500    Theoretical estimate. Should be of comparable stability
            compared to PRORATE.
                                                45

-------
                                            TRIALLATE
                                      (Far-Go Granules Herbicide)
Empirical Formula:

Molecular Weight

IUPAC Name:

Structure:
               305 g/mol

               s^3^'-Trichloroallyl)-diisopropyl-thiocarbarnate
 Data Source

 1. Pure compound in air


 Evaluation:
   Recommendation:
   Ranking:
        T99 (2X°Q     Comment

516     Data fit to pseudo-first order decay. A = 6.8E8 1/s and
                Ea = 31kcal/mol.

                Low-energy channels believed to be dominated by
                C-N fission, C-S fission, and 4-center HC1 elimination.

                For this compound, there are 2 C-N routes, 1 C-S route,
                and 1 HC1 elimination route,

        755     1. C-N fission. Rough estimates of rate parameters yield
                log A = 16.3 1/s and Ea 275 kcal/mol.
                Ea based on bond strength of CgHsCH^NHCHs of
                68.7±1 kcal/mol. Since C-N fission for this compound
                does not form resonance-stabilized radical, Ea must be
                 substantially larger than 69 kcal/mol.

        691     2. C-S fission. De(C2Hs-S) = 70.5 kcal/mol. Rough
                 estimates of Arrhenius parameters yield log A = 16.01/s
                 and Ea = 69 kcal/mol.

         751     3.  HC1 elimination, using 23-dicMoropropane by
                 analogy (sp2 hybridized Q, tough estimates of Arrhenios
                 coefficients are log A = 13.8 and Ea =* 63 kcal/moL

                 If radical chains are present. H abstraction from methyl
                 groups may also contribute to destruction.

                 C-S fission. C-N fission, four-center HC1 elimination, and
                 H abstraction may all contribute to this very complex
                 decomposition mechanism.

          550    Should be slightly more stable than Data Source No. 1.

-------
                                  APPENDIX 2

                  RESPONSE FACTORS FOR ANALYTICAL STANDARDS
      A complete list of the compounds run as analytical  standards in  this
program is presented below:
                                          Response Factors
Compound

Carbon Monoxide
n-Propane
Acetonitrile
Carbon Dioxide
2-Methyl-propane
Propanenitrile
Hydrogen Chloride
n-Butane
2-Methyl-propenenitrile
Methane
.2-Methyl-Butane
Butanenitrile
Ethane
n-Pentane
2-Butenenitrile
Ethylene
2-Methyl-pentane
2-Chloro-propeneni tri1e
Acetylene
n-Hexane
2-Butenedinitrile
Sulfur  Dioxide
2,4-Dimethylpentane
2-Methyl-propanenitrile
n-Heptane
Toluene
n-Octane
p-Xylene
n-Propylbenzene
n-Decane
n-Butylbenzene
n-Dodecane
n-C12
n-C13
n-C14
n-C15
Alachlor
Atrazine
Oxidative

 50
400
428
 50
500
527
100
450
300
100
175
546
181
190
554
200
227
381
175
232
331
100
230
538
180
350
180
375
355
181
450
190
190
181
186
 184
1000
1200
 Pyrolytic

 100
 600
 350
 100
 844
 527
 100
 627
 350
 200
 232
 546
 234
 230
 554
 240
 227
 381
 200
 232
 331
 350
 230
 538
 180
 350
 180
 375
 355
 181
 450
 190
 190
 181
 186
 184
1000
1200
                                       47

-------
                                          Response Factors

Compound                            0x1 dative         Pvrolvtlc

Diphenylamine                        500               500
Quinollne                            500               500
4-Chloro-aniline                     500               500
N,N-Dimethylan11ine                  450               450
Thloacetanride                        125               125
Naphthalene                          350               350
Aniline                              500               500
Benzonitrile                         350               350
Benzene                              352               352
Acenaphthene                         500               500
Acenaphthylene                       500               500
Anthracene                           500               500
Fluoranthene                         450               450
Fluorene                             450               450
Phenanthrene                         400               400
Pyrene                               500               500
                                     48

-------
                      APPENDIX  3

                  MASS BALANCE DATA



            TABLE 3.1. ALDICARB OXIDATION


                                    Weight X

Temp.fC)         C           N          S

 275              109.1        75.3      140.8
 300               93.2        70.1      122.6
 350               97.2        72;3      124.6
 400               90.1        75.9      115.9
 450              114.0       105.1      127.9
 500               99.3        97.3      103.4
 550               96.2        91.7      114.1
 600              103.8       124.9      112.6
 650               96.0        97.9      131.2
                           49

-------
sszsss
           TABLE  3.2.  ALDICARB PYROLYSIS
                                 inssssessa

                                   Weight %

                             H          S
300              106.1        73.4        140.5
350               82.6        62.0        111.8
400              104.1        73.0        140.4
450               93.9        54.4        118.9
500              123.6        91.7        130.0
550              120.4        101.3         78.3
600              116.7        105.7         65.4
650               93.5        93.2         74.9
700               94.9        97.6        106.9
750               99.5        106.7        126.7
800               96.0        97.4        132.0
850              103.0        93.9        151.0
900              106.9        84.4         93.3
950               94.6        104.9        106.0
1000              115.7        92.7        109.2
                           50

-------
            TABLE 3.3. ATRAZINE OXIDATION
                         = ======= = =3
Temp.CC)

 275
 300
 350
 400
 450   "
 475
 500
 550
 600
 650
 700
 800
100
109
104
 95
156.9
 89.0
135.
103
107
.7
.4
.3
108.1
 89.1
 42.2

N
100.9
109.9
104.6
94.3
119.1
48.4
79.4
89.9
116.0
153.2
161.0
54.6
Weiqht %
£1
100.9
100.9
104.6
94.5
93.5
52.6
48.0
112.8
98.9
97.4
99.2
103.1
                         51

-------
            TABLE  3.5.  ALACHLOR OXIDATION
            BssxaraajsaaaaasaaasaaaBBacasaea

                                    Height %

Temp.CC)         C           N           £1

 275              101.2       101.1       101.1
 300               98.2        99.1        97.1
 350               95.4        97.2        94.2
 400              101.6       105.7        91.9
 450               79.5        89.0        91.4
 500               93.7       101.9        76.0
 550               88.9        80.0        97.6
 600               84.3        37.2       100.9
 650               81.2       141.5       112.8
 700               94.4        93.3       106.2

-------
            TABLE 3.6. ALACHLOR PYROLYSIS
                                    Weight %

Temp.CC)         C           N           £L

 300              101.2       101.3       101.3
 400               96.6        97.8        94.2
 450              102.5       105.4        96.4
 475              100.3       107.2        88.0
 500              122.7       136.6        95.0
 525              135.8       138.3       102.3
 550               95.0        94.3        69.7
 600               91.9        83.2       126.4
 650               99.9        81.0       118.7
 700               69.3        52.0       100.6
 750               80.4        53.2        90.1
 800               69.6        51.5        69.4
 850               78.9        60.3        78.2
 900               70.9        78.8        94.3
 950               73.5       102.7       100.7
 1000               63.5       109.9        95.3
                           54

-------