| Chemical Abstract Number (CAS #) |
297972
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| Synonyms | Zinophos |
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Thionazin | O,O-Diethyl-O-(2-pyrazinyl)phosphorothioate | Phosphorothioic acid, O,O-diethyl O-pyrazinyl ester |
| Analytical Methods |
EPA Method 622.1 |
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EPA Method 8141A |
| Molecular Formula | C8H13N2O3PS |
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| Use | FORMERLY A SOIL INSECTICIDE ON VEGETABLES; CORN; STRAWBERRIES;
MINT
/Former uses/: Thionazin is a soil insecticide and nematocide effective against a number of plant
parasitic as well as free living nematodes, including those attacking buds, bulbs, leaves and roots,
as well as against soil dwelling pests such as root maggots and symphylids and foliar insects such
as aphids and leaf miners. When incorporated in mushroom compost at spawning it is effective
against mushroom flies.
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| Apparent Color | PURE CMPD IS ALMOST COLORLESS LIQUID
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| Boiling Point | 80 DEG C
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| Melting Point | -1.7 DEG C
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| Molecular Weight | 248.26
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| Density | 1.204-1.210 @ 25 DEG C
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| Environmental Impact | If produced thionazin may enter the environment as a fugitive emission during its
manufacture, formulation, and during its application as a pesticide. If released to the atmosphere,
it is expected to exist predominantly in the vapor phase. Rapid destruction by the reaction with
photochemically produced hydroxyl radicals is expected to occur; the half-life for this process can
be estimated at 4.3 hr. Wet deposition may also occur. If released to soil, limited data suggests
that microbial degradation under aerobic conditions may occur. The half-life of 10-100 ppm
thionazin in soil is on the order of 2-6 weeks which encompasses the removal processes leaching,
biodegradation and hydrolysis. Higher concentrations of thionazin are removed at a slower rate. It
appears to be removed more rapidly from alkaline soils than from acidic soils. Thionazin is
expected to be highly mobile in soil. If released to water, thionazin is expected to undergo
hydrolysis at an experimentally determined half-life at 25 deg C of about 30 days at pH 7. Neither
adsorption to sediment and suspended matter, nor bioconcentration in fish and aquatic organisms
are expected to be significant fate processes. Occupational exposure to thionazin may occur by
inhalation or dermal contact for those involved in the synthesis, formulation, or application of this
pesticide.
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| Environmental Fate | TERRESTRIAL FATE: SOIL WAS TREATED WITH ZINOPHOS SHORTLY
AFTER PLANTING. DETECTABLE AMT REMAINED FOR 1 YR IN CHURCH FIELD
SOIL (PH 5.4) BUT IN HIGH FIELD (PH 7.3) NO RESIDUES DETECTED AFTER THIS
PERIOD. ZINOPHOS HALF-LIFE IN SOILS VARIED FROM ABOUT 5-12 DAYS @ LOW
DOSAGE (5 PPM) TO ABOUT 9-22 DAYS @ HIGH DOSAGE (20 PPM).
TERRESTRIAL FATE: Thionazin was described as slightly persistent in soil, with a given
half-life of 2-6 weeks encompassing removal by leaching, hydrolysis, and biodegradation .
Commercial formulations of 10 ppm thionazin applied to the top or broadcast 4 inches into a
sandy loam soil (pH= 6.1) resulted in a removal half-life of 23 days . The initial loss rate when
thionazin was applied at 250 ppm was much slower, and traces of thionazin remained after 2
years . In a laboratory assay, 100 ppm thionazin lost 95% of its biological activity in 100
days . Thionazin was found in soil up to one year after its application to an acidic sandy loam
field, but this compound was not detected after 10 weeks in alkaline clay soil .
AQUATIC FATE: If released to water, thionazin is expected to undergo hydrolysis. An
experimentally determined half-life for the hydrolysis of thionazin at 25 deg C under neutal
conditions was given as 29 days at pH 7(1,2). A half-life of approximately 40 and 4 days at pH 10
and pH 11, respectively, can be calculated from a basic hydrolysis rate constant of 7.3
L/mole-hr(1,2). Thionazin was reported as having a half-life of 14 weeks in natural water at pH
6.8 .
ATMOSPHERIC FATE: If released to the atmosphere, the vapor pressure, 3X10-3 mm Hg at
30 deg C , suggests that thionazin may exist entirely in the vapor phase in the ambient
atmosphere . Thionazin is expected to undergo rapid destruction by the gas phase reaction with
photochemically produced hydroxyl radicals; the half-life for the reaction can be estimated at 4.3
hr(2,SRC). The water solubility, 1140 mg/l at 25 deg C , suggests that wet deposition may
occur.
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