Diazinon

333-41-5

Sulfotepp: 1.4 - 6.9 ppm as impurity (Meier et al. 1979).

Active ingredient in insecticides.

A colourless oil (decomposes above 120 °C)

304.38

The mobility of diazinon is medium high. 
It is bound more
tightly to soil the higher is contents of humus in soil, the
dryer soil is and the lower temperature is in soil. 
Ka: 2 - 325 
Koc: 255 - 496 (KEMI 1991).

Decomposes above 120 °C.

Diazinon is transformed nearest by hydrolysis. 
The
transformation is relative slow. 
It depends on acidity in soil
or water; the sourer soil the quicklier transformation (KEMI 
1991).

Acid hydrolysis (pH ~ 2) reduced diazinon concentration
by >99.9%; hydrolysis products are
6-isopropyl-4-methyl-2-pyrimidinol and thiophosphate (Meier et 
al. 1976).

75 - 100 % disappearance from soils: 12 weeks (Verschueren
1983).

Persistence in soil at 10 ppm initial concentration:
                                   wk incubation to
                              50% remaining   5% remaining
sterile sandy loam                 12.5             -
sterile organic soil                6.5             -
non-sterile sandy loam             <1               1
non-sterile organic soil            2               7
(Miles et al. 1979)

Biodegradation:
0% by BOD
period: 14d
substance: 100 mg/l
sludge: 30 mg/l
(MITI 1992)

In soil diazinon is degraded by microorganisms under acidic
conditions. 
It is happening more quicklier if the soil is misty
and it has low pH and high temperature. 
In the laboratory
experiment half of diazinon was mineralized after five months
at 25°C. 
Degradation of diazinon by microbies is happening also
in water. 
The half-life in water is about 3 days in the
laboratory experiment (KEMI 1991).

In the degradation (clay soil) pyrimidinol and
hydroxypyrimidinol are the degradation products. 
Pyrimidinol
degradates in acidic conditions to carbon dioxide.

Diazinon transforms even to diazoxon and hydroxydiazinon.

Diaoxon is more toxicity than diazinon (KEMI 1991).

Bioconcentration ratios of diazinon by various species of
freshwater organisms - exposed to 10 ppb for 7 days:
                               bioconcentration ratio
                                     average
Pseudorasbora parva                   152
Cyprinus auratus                       36.6
Cyprinus carpio                        65.1
Lebistes reticulatus                   17.5
Procambarus clarkii                     4.9
Indoplanorbis exustus                  17.0
Cipangopoludina malleata                5.9

Pseudorasbora parva: bioconcetration ratio increased with body
weight (exposure at 10 ppb for 7 days) from 50 to 175 for body
weights between 2 and 6 g (Kanazawa 1978).

Effect of the diazinon concentration in test water on the
bioconcentration ratios by Pseudorasbora parva:
diazinon in  days after bioconc.  days after return  diazinon in
water, ppb   exposure   ratio     to clean water     fish, ppb
   11.5         7         118.2         8                 5
   52.5         7         206.0         7                26
(Kanazawa 1978)

Diazinon is moderately bioaccumulated. log Kow: 3.95; BCF in
fish 18 - 213 (KEMI 1991).

Confirmed to be non-accumulative or low accumulative (Anon 1987).

Bioconcentration factor (other organisms):
4.9 - 152,water organisms (Verschueren 1983).

Diazinon (12 mg/kg soil) hinders the growth of young earthworms
(Allolobophora calignosa) (KEMI 1991).

Highly toxic to bees (Martin 1968).

LD50, 48hr, 0.37 ug/bee (KEMI 1991).

LC50, 0.025 mg/l, 96hr, Pteronarcys californica
(Sanders & Cope 1968).

LC50, 0.0046 mg/l, 30d, Pteronarcys dorsata
NOEC, 0.0039 mg/l, 30d, Pteronarcys dorsata
(Verschueren 1983).

LC50, 0.0017 mg/l, 96hr, Acroneuria lycorias
LC50, 0.00125 mg/l, 30d, Acroneuria lycorias
NOEC, 0.00083 mg/l, 30d, Acroneuria lycorias
LC50, 0.0022 mg/l, 30d, Ophiogomphus rubinsulensis
NOEC, 0.00129 mg/l, 30d, Ophiogomphus rubinsulensis
LC50, 0.00354 mg/l, 30d, Hydropsyche bettoni
NOEC, 0.00179 mg/l, 30d, Hydropsyche bettoni
LC50, 0.00105 mg/l, 30d, Ephemerelia subvaria
NOEC, 0.00042 mg/l, 30d, Ephemerelia subvaria
LD50, 2450 ppm, rice field spider: Oedothorax insecticeps
(Ishikura 1972).

LC50, misty soil, 1.2 mg/kg soil, grasshopper
LC50, dry soil, 37.6 mg/kg soil, grasshopper
(KEMI 1991).

Application of diazonin at 0.42 kg a.i. 
(50 % emulsifiable
concentrate)/ha to about 30 days old tomatoes (Lycopersicon
esculentum) as foliar sprays caused a reduction in tomato
shoot dry weight (Stephenson et al. 1980).