El. Kruger et al., PERSISTENCE AND DEGRADATION OF [C-14] ATRAZINE AND [C-14] DEISOPROPYLATRAZINE AS AFFECTED BY SOIL DEPTH AND MOISTURE CONDITIONS, Environmental toxicology and chemistry, 12(11), 1993, pp. 1959-1967
The fate of atrazine and one of its degradation products deisopropytat
razine has been investigated using radiotracers under laboratory condi
tions. The metabolic route and rate were investigated under saturated
and unsaturated conditions, with samples of soil taken from four depth
s down to 120 cm. The major degradation products identified from [C-14
]atrazine and [C-14]deisopropylatrazine treatments were deethylatrazin
e and didealkylatrazine, respectively. The detected minor degradation
products were hydroxyatrazine, deethylhydroxyatrazine, and deisopropyl
hydroxyatrazine. Under unsaturated conditions atrazine and deisopropyl
atrazine were least persistent in the top 30 cm, and their persistence
increased with increase in depth. The half-life of atrazine under uns
aturated conditions increased with depth and ranged from 41 to 231 d f
or the studied depths, whereas the half-life of deisopropylatrazine ra
nged from 32 to 173 d. Deisopropylatrazine was more susceptible to min
eralization than atrazine, and the amount of mineralization decreased
with increase in depth. Bound residues were formed to a greater extent
in surface soils. Under saturated conditions at the 90- to 120-cm dep
th, the half-life of atrazine was 87 d. Deisopropylatrazine was less p
ersistent in saturated soil than in unsaturated soil at the 90- to 120
-cm depth, with a half-life of 58 and 173 d, respectively. The increas
ed degradability of deisopropylatrazine as compared with atrazine and
the decreased persistence of deisopropylatrazine under saturated soil
conditions provides a logical explanation for its relatively low conce
ntrations in ground water as compared with atrazine.