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O
O
H
N
P
HO
OH
TiO
2
OH
O
O
O
Adsorbed on Tio
2
H
N
H
N
CH
3
+ PO
3-
P
OH, O
-
, etc.
HO
HO
OH
OH
HCOO
-
CO
2
HOCH
2
COOH
Glycolic acid
O
+
OH
O
O
-
etc.
P
HO
OH
P
H
2
N
OH
OH
TiO
2
OH
TiO
2
Aminomethylphosphoric acid
NO
3-
+ PO
3-
FIGURE 6.12
Proposedtentativepathwayforthephotocatalyticdegradationofglyphosate.(Reprintedfrom
Chemosphere,
76,
Echavia,G.R.M.,Matzusawa,F.,andNegishi,N.,Photocatalyticdegradationoforganophosphateandphos-
phonoglycinepesticidesusingTiO
2
immobilizedonsilicagel.,595-600,(2009),withpermissionfromElsevier.)
paper,Kamiyaetal.(2001)alsodescribedtheeffectsofcyclodextrinsonphotodegradation
of organophosphorus pesticides in humic water. The decomposition of
14
C-fenitrothion
onsilicagelchromatoplatesaswellasinpolarandnonpolarsolventsundersunlightand
ultravioletlightwasdescribedbyZayedandMahdy(2008).Itsstabilityinsunlightonthe
leafsurfacesofbeanplantsandondifferentsurfaceswasalsodeterminedbyZayedand
Mahdy (2008). The main photoproducts were identiied as carboxyfenitrothion, fenitro-
oxon,carboxyfenitrooxon,and3-methyl-4-nitrophenolandsmallamountsof3-carboxy-4-
nitrophenolandmethylparathion.Theadditionofcarbarylanddeltamethrininsecticides
slightlyacceleratedthephotodecompositionoffenitrothiononsilicagelplatesandinsolu-
tion(Table6.8;ZayedandMahdy2008).Synthesisof
14
C-fenitrothionanditsmaindegrada-
tionproductsbyphotodecompositionisshownin
Figure6.13
.
TABLE 6.8
EffectofCarbarylandDeltamethrinonthePhotodecompositionof
14
C-FenitrothionExposed
toSunlightinSolutionandonSilicaGel
Percentage of Recovered Radiocarbon as Indicated Products
I
II
III
IV
V
Origin
Total
Pesticide
Chemical
A
B
A
B
A
B
A
B
A
B
A
B
A
B
Fenitrothion
54
70
10
4
Detected
bycolor
5
3
2
3
10
7
81
87
Fenitrothion+
carbaryl
46
60
5
3
3
1.5
3
2
15
12
72
78.5
Fenitrothion+
deltamethrin
40
45
5
5
5
4
2
2
20
18
72
74
Source:
Reprintedfrom
Chemosphere,
70,Zayed,S.M.A.D.andMahdy,F.,Decompositionof
14
C-fenitrothion
under the inluence of UV and sunlight under tropical and subtropical conditions, 1653-1659,
(2008),withpermissionfromElsevier.
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