Geoscience Reference
In-Depth Information
Table 12.6
Pesticides used in field experiments
Pesticides
Formula
Solubility in
water (mg/L)
Chemical name
Atrazine
C
8
H
14
ClN
5
30
2-Chloro-4-ethylamino-6-isopropylamino-
1,3,5-triazine
Azinphosmethyl
C
10
H
12
N
3
O
3
PS
2
30
O,O-Dimethyl S-[(4-oxo-1,2,3-benzotriazin-
3 (4H)-yl) methyl] phosphorodithioate
Bromacil
C
9
H
13
BrN
2
O
2
813-815
5-Bromo-3-sec-butyl-6-methyluracil
Napropamide
C
17
H
21
NO
2
73
(R,S)-N,N-diethyl-2-(1-naphthyloxy)
propionamide
Parathion
C
10
H
14
NO
5
PS
24
O,O-Diethyl O-4-nitrophenyl
phosphorothioate
N
2
,N
4
-Diisopropyl-6-methylthio-1,3,5-
triazine-2,4-diamine
Prometryn
C
10
H
19
N
5
S
33-48
Tetradifon
C
12
H
6
Cl
4
O
2
S
\0.1
4-Chlorophenyl 2,4,5-trichlorophenyl
sulfone
N
2
-Tert-butyl-6-chloro-N
4
-ethyl-1,3,5-
triazine-2,4-diamine
Terbuthylazine
C
9
H
16
ClN
5
(conservative) soluble tracers (chloride or bromide), was determined periodically.
Transport of contaminants was determined for both nonpoint (areal) and point
application on the field surface.
Field transport of a persistent organochlorine (tetradifon) and a degradable
organophosphorous (azinphosmethyl) insecticide was examined under dry and wet
irrigation treatments followed by winter precipitation (Yaron et al.
1974
). In the
dry irrigation treatment, the moisture deficit was replenished periodically in the
0-60-cm soil layer; in the wet treatment, an additional 30 % volume of water was
applied in the same irrigation cycles. Redistribution profiles of the two insecticides
in the 0-30 cm (a and b) and 0-110 cm (c) soil during the irrigation season are
presented in Fig.
12.32
. We see no significant differences in azinphosmethyl
concentration between the two irrigation treatments. Azinphosmethyl concentra-
tion decreased as a result of volatilization or biologically induced degradation.
Tetradifon, however, exhibited a concentration decrease under the wet irrigation
regime, on account of its downward movement. Tetradifon is persistent and rel-
atively soluble in water, and it was found in the soil profile up to a depth of 110 cm
after the rainfall period (when the amount of leaching water, irrigation and rainfall,
was 618 mm for the dry treatment and 770 mm for the wet treatment; see
Fig.
12.32
c). While in the dry irrigation treatment, the concentration front reaches
a depth of 60 cm, the wet treatment caused the front to reach a depth of 90 cm.
Significantly, the winter rainfall was sufficient to eliminate concentration differ-
ences created by the irrigation regimes.
In a separate study, the effect of spatial variability on the transport of non-
conservative and conservative contaminants, under leaching by irrigation and
rainwater, was studied in an experimental 175-m
2
plot located on a sandy loam
Mediterranean red soil. The redistribution of two nonconservative herbicides
