Atrazine
PESTICIDE NAME: Atrazine
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Trade name(s): AAtrex, Atranex
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Manufacturer(s): Shell Chemical Company, Agricultural Chemicals
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One Shell Plaza
P.O. Box 3871
Houston, TX. 77001
I. Basic information
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A. Molecular structure: C8H14ClN5
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B. Chemical name:
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2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine
C. Derivatives: hydroxyatrazine,
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4,5-bis(alkylamino)-1,3,5-triazin-2-ol (via hydrolysis), de-ethylated
atrazine, deethylated hydroxyatrazine
D. Molecular weight: 215.7 g/mole
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E. Solubility in water: 30 mg/l
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F. Common physical appearance: colorless crystals
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G. Oral LD50(rat): 3080 mg/kg
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H. Pesticide classification: triazine herbicide
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I. Restricted use list (N.Y.): no
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EPA priority pesticide list: no
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J. Crop use: corn, fruit
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II. Text
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Atrazine is a relatively non-toxic, moderately persistent triazine
herbicide widely used in the state of New York, particularly on corn.
There is substantial information in the scientific literature
concerning atrazine. Atrazine is a basic pesticide which easily
associates with hydrogen to form aprotonated species thus it can behave
as a cation in soil. It rapidly degrades to its metabolites, a process
which follows first-order kinetics. There is some evidence that
atrazine can leach; however, degradation is considered to be the main
source of loss of atrazine from the soil.
III. Soils information
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A. Degradation and transformation
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The degradation of atrazine follows first-order kinetics with no
initial lag time (2,5). When hydrolyzed, atrazine degrades to
4,5-bis(alkylamino)-1,3,5-triazin-2-ol. Hydrolysis is affected by
temperature, pH, organic matter content, and soil moisture content. A
wet soil will slow degradation. The rate of hydrolysis also slows at
elevated temperatures (ca.70deg C) if the pH is neutral; however, any
deviation from neutral pH at that same elevated temperature will
increase the hydrolysis rate. At 25deg C, an increase in pH will slow
the hydrolysis half-life from 64d at pH5 to more than 200d at pH 7 and
9(1,2).
At 64d after application, atrazine decomposed twice as fast in the
presence of organic matter as without. Levels of decomposition were
about equal with and without additions of organic matter at 264d(7).
Atrazine has no effect on soil microorganisms and does not inhibit them
from degrading added straw, etc.(7).
The tables given below present data concerning degradation and
transformation of atrazine. The reference is given in parentheses at
the end of each title.
Half-life of atrazine in two loamy sand soils(2)
half-life(soil) at 22degC
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Hatzenbuhl loamy sand (pH=4.8) 53 days
Neuhofen loamy sand (pH=6.5) 113 days
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Distribution of atrazine and hydroxyatrazine in silt loam soil at two
pH levels (% of applied)(1)
topsoil topsoil subsoil tot. tot.
ATRAZINE extract fixed extract leach respire plnt. rcov.
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pH 5.5 71.7% 13.8% 1.6% 0.1% 0.8% 1.4% 89.4%
7.5 65.4 14.8 5.5 0.2 0.9 3.9 90.6
HYDROXYATRAZINE
pH 5.5 87.6 4.1 1.1 0.1 0.4 0.1 93.4
7.5 85.4 6.7 5.7 0.1 0.4 0.4 98.8
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Disappearance rate and half-life of atrazine in loamy sand, sandy clay
loam and sandy loam soils (values averaged) over a period of three
years(5)
disappearance rate
total days constant/day half-life(d)
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1973 1-42 -0.049 14.2_2.7
1974 1-66 -0.021 33.1_9.2
1975 1-84 -0.018 39.6_8.8
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Effect of moisture level and amendments on atrazine decomposition in a
sandy loam soil (values given as % atrazine removed)(7)
Time After Treatment(d)
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Treatment 16 32 66 192 264 375 472 486 538 550
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aer.soil 0.05 0.14 0.64 5.84 9.94 13.69 - 16.21 - 17.93
aer.soil+ 0.06 0.27 1.41 6.92 10.35 13.81 - 16.33 - 18.07
bean straw
sat.soil - 0.02 0.03 0.13 0.27 0.53 1.04 - 1.48
sat.soil+ - 0.02 0.04 0.16 0.30 0.57 1.16 - 1.56
bean straw
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B. Adsorption and transport
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The adsorption of triazine herbicides has been found to follow the
order simazine
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criticism of unnamed products implied. Most of this information is historical
in nature and may no longer be applicable.
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