Geoscience Reference
In-Depth Information
Table 16.4 Percent of remaining parathion and of its degradation products after 130 days of
incubation, in 14 sterile soils with different chemical and mineralogical properties (Yaron
1975
)
Soil type
Predominant
clay
Clay
(%)
Organic
matter
(%)
pH
Parathion
remaining
(%)
Diethyl
thiophosphoric
Dry
Wet
Dry
Wet
Sandy regosol
Mont.
2.9
0.45
8.2
96.8
79.0
330
2,200
Loessial light brown
Kaol.
16.9
0.66
8.2
88.0
84.0
1,300
1,700
Grumusolic brown
Mont.
40.0
0.08
7.9
83.0
90.8
1,700
960
Red terra rossa
Kaol.
75.5
1.07
6.8
77.0
87.0
2,400
1,400
Reddish brown grumusol
Mont.
57.6
1.50
7.6
82.8
90.8
1,800
960
Red terra rossa
Kaol.
76.6
1.89
6.9
81.1
99.0
1,900
100
Basaltic brown Mediterranean
Kaol.
22.4
2.47
6.4
92.0
97.5
840
10
Hamra
Kaol.
9.7
2.75
6.8
92.0
97.5
840
260
Basaltic brown Mediterranean
Kaol.
32.0
3.61
6.5
84.0
97.4
1,700
270
Calcareous brown
Mediterranean
Mont.
42.9
3.94
7.5
91.7
98.8
870
130
Reddish brown terra rossa
Mont.
65.3
4.10
7.7
96.8
98.0
400
200
Reddish brown terra rossa
Mont.
71.1
4.94
7.5
96.0
99.7
420
30
Red terra rossa
Kaol.
68.5
4.98
7.5
80.7
97.8
2,000
220
Brown rendzina
Mont.
46.5
12.10
7.3
95.7
99.8
450
20
The conversion of parathion is affected by soil constituents in the order kao-
linite [ smectite [ organic matter and is related inversely to the adsorption
affinity of these materials for this contaminant (Mingelgrin and Saltzman
1977
).
Although the extent of hydrolysis differs among soils, it is apparent that soil-
surface degradation of parathion is caused by hydrolysis of the phosphate ester
bond. The presence of water in the soil-parathion system led to a decrease in the
surface-induced degradation of the organic molecule and diminished the effect of
natural soil properties on its persistence.
16.1.3 Photochemical Reactions
Photochemical transformation of contaminants occurs in surface waters or when
adsorbed on atmospheric particulates, which originate from the subsurface solid
phase and are redeposited on land surfaces. We consider three studies: the first on
photochemical reactions of drugs in natural waters, the second on the photodeg-
radation of a polycyclic aromatic hydrocarbon adsorbed on a particulate, and the
third on the effect of sunlight on photodegradation of a flame retardant (BDE-209)
adsorbed onto clay minerals, metal oxides, and sediments.
The photolysis of a class of sulfa drugs containing six-membered heterocyclic
substituents (sulfamethazine, sulfamerazine, sulfadiazine, sulfachloropyridazine,
and sulfadimethoxine) was investigated by Boreen et al. (
2005
) in natural lake
