Soil granulometry
Adsorption of pesticides applied alone or in mixtures on an
agricultural Vertic dark soil
1 Clermont Université, Université Blaise Pascal, Institut de
Chimie de Clermont-Ferrand, UMR-CNRS 6296, BP 80026, F-63171
Aubière Cedex, France
[email protected]
2 Faculty of Chemistry, Jagiellonian University, Ingardena 3,
30-060 Cracow, Poland
3 Institute of Physical, Chemical and Biological Problems of
Soil Science, Russian Academy of Sciences, Pushchino, Moscow Region
142290, Russia
Dumas, E.1, Zemelka, G.2, Alekseeva, T.3, Sancelme, M.1, Forano,
C.1, Besse-Hoggan, P.1
Acknowledgements: This work is part of an interdisciplinary
project funded by CPER (Contract between the State and Region)
Edith DUMAS would like to thank the Région Auvergne and FEDER
for financial support.
Clay identification
5 10 15 20 25 30 35
2 theta ( ) CuKα
Inte
nsitie
s(c
ps)
Kaolinite
Mg2+-Clay
Mg2+-Clay/350 C
Mg2+-Clay/550 C
Illite
1.000 nm
Applications of herbicide mixtures to enhance the effects are
now a common practice in agriculture. It allows the range of weeds
treated to be broadened and to limit the agronomic dose applied for
each herbicide. Nevertheless the presence of multi-contaminants in
the soil can affect the behaviour of individual components and only
a few studies have dealt with this phenomenon. The objective of our
study was to explore the sorption processes of herbicides belonging
to various chemical families, alone or in mixtures, on bulk soil
and fine fraction of a Vertic dark soil from a sedimentary valley
(central France). Indeed sorption is a key process governing the
fate of herbicides.
Soil properties
Sampling of an agricultural soil from an experimental field
located in the Limagne
plane (Auvergne, France) at four points and 2 depths
Adsorption kinetics Adsorption isotherms 1g dry soil,
preconditioning with 3mL Volvic water, 12 hours shaking, 20∘C
Centrifugation 12500rpm, 15min
3mL herbicide solution, concentration 100µM, in distilled water
(pH =6), shaking, at 20∘C
Centrifugation, HPLC analysis of supernatant
5 10 15 20 25 30 35 40 45 50 55 60 65 70
qf.sp mt
qmtq
cc
f.sp
mtq
qcmt
f.sp
c
f.sp
csm
m
f.spk
m
sm
f.sp
q
Rel
ativ
e in
tens
ities
(a.u
.)
2 theta (°) (CuK)
q
sm - smectitem - micak - kaolinitef.sp - feldsparq - quartzc -
calcitemt - magnetite
Bulk
Fine
5 10 15 20 25 30 35 40 45 50 55 60 65 70
qf.sp mt
qmtq
cc
f.sp
mtq
qcmt
f.sp
c
f.sp
csm
m
f.spk
m
sm
f.sp
q
Rel
ativ
e in
tens
ities
(a.u
.)
2 theta (°) (CuK)
q
sm - smectitem - micak - kaolinitef.sp - feldsparq - quartzc -
calcitemt - magnetite
5 10 15 20 25 30 35 40 45 50 55 60 65 70
qf.sp mt
qmtq
cc
f.sp
mtq
qcmt
f.sp
c
f.sp
csm
m
f.spk
m
sm
f.sp
q
Rel
ativ
e in
tens
ities
(a.u
.)
2 theta (°) (CuK)
q
sm - smectitem - micak - kaolinitef.sp - feldsparq - quartzc -
calcitemt - magnetite
Bulk
Fine
Bulk soil and fine fraction mineralogy
Conclusions: The present results show that the fate of
pesticides is strongly dependent on their chemical structure and
corresponding physico-chemical properties as well as on the
environmental conditions and soil characteristics. We have also
evidenced the effect of pesticide mixture on individual pesticide
adsorption behaviour. The equilibrium between soil and water
compartments observed for all the pesticides studied shows a great
mobility that can lead to leaching of pesticides when the water is
renewed in soil.
Adsorption kinetics on bulk soil
Adsorption isotherms of tembotrione (), nicosulfuron () and
S-metolachlor () on bulk soil
Same protocol as for kinetics, concentration ranging from 10µM
to 100µM. Shaking time for pesticides alone : see kinetics. 6h
shaking for pesticide mixtures.
Coarse sand Fine sand Silt Clay
> 500µm 50-500 µm 2-50µm < 2µm
5% 18% 34% 43%
Rich in organic matter: 2.35% Organic Carbon.
Total Carbon: 5.4%,
Total Carbon after H2O2 treatment: 3.5%
Organic matter strongly linked to clay minerals,
70% humin = insoluble
High combustion temperature (TGA): 320∘C
5 10 15 20 25 30 35
K+-Clay
K+-Clay-EG
Clay
Inte
nsitie
s(c
ps)
2 theta (°) CuKα
1.888 nm
1.523 nm
Swelling = Smectites
• Sulcotrione • Tembotrione
Cocktail for maize crops
Soil = Black vertisol, alkaline, rich in swelling clays,
stable insoluble organic matter
Freundlich C type isotherms : Equilibrium solid/liquid Physical
adsorption
quartz, calcite, smectite Main clay mineral: smectite. Other
clay minerals : kaolinite, illite
Clay soil
pH=8.2 Buffered by high quantity
of carbonates
Stable, insoluble organic matter
Sulcotrione: R = Cl, R’ = H
Mesotrione: R = NO2 , R’ = H
Tembotrione: R = Cl, R’ = -CH2-O-CH2-CF3
Nicosulfuron
S-Metolachlor
BET surface area (m2/g)
The herbicides studied are selective for maize crops and are
generally used in mixtures to get
better herbicidal results
0
20
40
60
80
100
120
140
0 100 200 300 400 500
nm
ol/g
dry
so
il
time (minutes)
0
20
40
60
80
100
120
140
0 100 200 300 400 500
nm
ol/g
dry
so
il
time (minutes)
4 hours for isotherm protocol 6 hours for isotherm protocol
0
50
100
150
200
250
300
350
0 100 200 300 400 500
nm
ol/g
dry
so
il
time (minutes)
• S-metolachlor
0
50
100
150
200
250
300
350
0 100 200 300 400 500
nm
ol/
g d
ry s
oil
time (minutes)
• Nicosulfuron
pKa Koc Water solubility 20°C, pH=7
tembotrione 3.18 nd 28.300 g/L
sulcotrione 3.13 36 1.670g/L
mesotrione 3.12 109 0.160g/L
nicosulfuron 4.78 20.7 7.500 g/L
S-metolachlore nd 200 0.480 g/L
4 hours for isotherm protocol 4 hours for isotherm protocol
0
10
20
30
40
50
60
70
80
90
100
0 0.2 0.4 0.6 0.8 1
Ad
sorb
ed
N2
(cm
3 /g)
Relative pressure (P/Po)
fine fraction fine fraction mineral
bulk soil bulk soil mineral
0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
20 30 40 50
Po
re V
olu
me
(cm
3/g.
Å)
Pore Diameter (Å)
Bulk soil Mineral bulk soil Clay fraction Clay fraction
mineral
76 88 141 154
Fast adsorption, better reproducibility after a few hours
Adsorption isotherms of N2 on bulk soil (), mineral bulk soil
(•), fine fraction () and mineral fine fraction ()
Mesoporous soil and fine fraction Higher surface when organic
matter is removed
Fraction of soil were separated by physical treatment. Fine
fraction is < 2µm. Organic matter was removed with H2O2
treatment to get
mineral soil and mineral fine fraction
Sulcotrione alone
Mesotrione alone
Tembotrione alone
Nicosulfuron alone
S-metolachlor alone
Soil 0.967 1.07 1.599 1.929 2.854
Fine fraction 1.147 1.52 1.801 3.867 5.752
Tembotrione +Nicosulfuron
+S-metolachlor
Tembotrione +Nicosulfuron
Tembotrione +S-metolachlor
Soil 0.854 0.844 0.789
Fine fraction 1.113 1.118 1.045
Nicosulfuron +Tembotrione
+S-metolachlor
Nicosulfuron +Tembotrione
Nicosulfuron +S-metolachlor
Soil 2.253 2.296 2.315
Fine fraction 4.293 4.009 4.238
S-metolachlor +Tembotrione +nicosulfuron
S-metolachlor +Tembotrione
S-metolachlor +Nicosulfuron
Soil 2.902 3.120 2.968
Fine fraction 5.558 5.972 5.503
Adsorption isotherms of tembotrione (), nicosulfuron () and
S-metolachlor () on fine fraction
Adsorption constant Kd (cm3.g-1) on soil and fine fraction
Kd S-metolachlor > Kd Nicosulfuron > Kd triketone family
Kd on fine fraction > Kd on soil Mixtures reduce the Kd of
tembotrione
Kd is the highest for tembotrione among triketone family members
(tembotrione, mesotrione and sulcotrione)
0
20
40
60
80
100
120
140
160
180
200
0 20 40 60 80 100
Cs (
nm
ol/
g d
ry s
oil
)
Ce (µmol/L)
0
20
40
60
80
100
120
140
160
180
200
0 20 40 60 80 100
Cs (
nm
ol/
g d
ry s
oil
)
Ce (µmol/L)
