Effect of DOM quality and quantity
on transport and degradation of pesticides
Karlien Cheyns, Mariangiola Mollicone, Stien Van Gestel
Dirk Springael, Erik Smolders, Jan Diels
01/02/2007
Objectives
Physico-chemical? - DOM-related transport and competition
?
?
Biodegradation?- availabilty?- DOM as C-source (catabolic repression, extra C-source, effect on microbial diversity)
DOM influences pesticide transport in soil• To predict the effects of DOM on
transport and degradation of pesticides with emphasis on the subsoil environment
• To unravel how DOM quality and quantity affect the dynamics/activity and competence of pesticide degrading populations with emphasis to the subsoil environment
Hypotheses
H1: Effects of DOM on transport of pesticides (Trifluralin) depends on the structure of DOM and can be predicted from batch sorption test
H2: Effects of DOM on pesticides (Atrazine) degradation in (sub)soil is the net result of effects on bioavailability and on population dynamics
H3: The final effect of DOM on the fate of pesticides in soil depends on DOM structure and is concentration dependent
Task 1: Study of the physico-chemical interactions between DOM, soil and pesticides
Task 2: Study of the effect of DOM on pesticide degradation
Task 3: Study of the net-effect of DOM on pesticide transport and biodegradation in soil columns
Task 4:
Effect of DOM on
the transport
of pesticides in field
experiments
Task 1: Study of the physico-chemical interactions between DOM, soil and pesticides
Task 2: Study of the effect of DOM on pesticide degradation
Task 3: Study of the net-effect of DOM on pesticide transport and biodegradation in soil columns
Task 4:
Effect of DOM on
the transport
of pesticides in field
experiments
Physico-chemical interactions
• Emphasis on 2 pesticides (herbicides)
– Atrazine: Log Kow= 2,7
Expected low KDOC
– Trifluralin: Log Kow = 4,83
High KDOC
Effect of DOM on atrazine sorption
• Batch sorption tests with or without extra DOC: – Solution of AT (~100 µg/L) and different
DOM shaken with soil (2:1 l:s)– After equilibrium (24h): analysis of AT
and DOC concentration in supernatans
Effect of DOM on atrazine sorption
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1,00
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7,00
8,00
9,00
0,00 5,00 10,00 15,00 20,00 25,00 30,00 35,00
DOC (mg C/l)
AT
(µ
g/l
)
Effect of DOM on trifluralin desorption
• Trifluralin: low solubility in water first spiking soil, then desorption tests in
batch with different DOM solutions
Fresh soil TM (2mm)
Treflan (19,2 mg TFL/kg)
14C Trifluralin (150 µg/kg)
Effect of DOM on trifluralin desorption
• Batch experiments
2 g spiked soil
10 ml DOM solution
24 h desorption
2 g control soil
10 ml DOM solution
Quench control
5 ml -> counter3 ml -> TOC analyser
5 ml + known # 14C TFL -> counter
Effect of DOM on trifluralin desorption
• Theory desorption with DOC– Kd
* = Komoc/(1+KDOCCDOC)
– Estimate Kom from logKom=0,72logKow+ 0,49
(Schwarzenbach and Westall, 1981)
logKow=4,83 => logKom= 3,97
Effect of DOM on trifluralin desorption
• Theory desorption with DOCKom soil 9300 l/kgKdoc 5000 l/kgTrifluralin µg/kg kg l µg TFL14C 117 0,002 0,01 0,234bodem OC DOC Kd* conc% mg/l l/kg µg/l
0,8 1 74,03 1,480,8 5 72,59 1,510,8 10 70,86 1,540,8 15 69,21 1,580,8 20 67,64 1,610,8 25 66,13 1,640,8 30 64,70 1,680,8 40 62,00 1,750,8 50 59,52 1,810,8 60 57,23 1,880,8 70 55,11 1,950,8 80 53,14 2,010,8 90 51,31 2,080,8 100 49,60 2,140,8 110 48,00 2,210,8 120 46,50 2,270,8 130 45,09 2,340,8 140 43,76 2,400,8 150 42,51 2,460,8 160 41,33 2,530,8 170 40,22 2,590,8 180 39,16 2,650,8 190 38,15 2,710,8 200 37,20 2,77
y = 0,0065x + 1,4839
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0 50 100 150 200
DOC (mg/l)
co
nc
en
tra
tio
n t
rifl
ura
lin
(µ
g/L
)
Effect of DOM on trifluralin desorption
• Influence pig manure (< 0,45 µm) on TFL desorption
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TOC (mg C/L)
TF
L (
µg
/l)
y = 0,0066x + 1,4619
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TOC (mg C/L)
TF
L (
µg
/l)
Effect of DOM on trifluralin desorption
• Influence Aldrich Humic Acid on TFL desorption (low DOC concentrations)
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0,20
0,40
0,60
0,80
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1,20
1,40
1,60
1,80
0 2 4 6 8 10 12 14 16 18 20
TOC (mg C/L)
TF
L (
µg
/l)
Effect of DOM on trifluralin de- and adsorption
• Testing reversible sorption:– Use supernatans from desorption test
with TFL spiked soil– Add non-spiked soil with low C
content– Equilibrate on shaker– Measure 14C-TFL and DOC
concentration of supernatans
4 g spiked soil
20 ml CaCl2 10-2M
Desorption
5 ml -> counter3 ml -> TOC analyser
Effect of DOM on trifluralin de- and adsorption
0,5 g clean soil, (0,18 % C)
10 ml solution + 14C TFL
Adsorption
5 ml -> counter3 ml -> TOC analyser
Effect of DOM on trifluralin de- and adsorption
• Testing reversible sorption:
-> If reversible sorption: expect 1,4 µg/l after adsorption
TFL (µg/l) DOC (mg C/l)desorption a 2,36 0,85
b 2,24 1,34c 2,37 1,21
adsorption a 1,07 0,64b 1,08 0,52c 1,14 1,08
Conclusions task 1 (physico-chemical interactions)
• Atrazine: – No expected DOM-facilitated mobilisation
• Trifluralin: – Indications of low mobilisation from batch
experiments with high DOC concentrations -> representative in field conditions?
= > Future task 1
• Additional de/adsorption tests of Trifluralin with DOM of different quality and quantity
• Test ‘enhancement solubility’ of Trifluralin in H2O with DOM in batch
• Abiotic column experiments to test if the batch sorption data explain DOM facilitated leaching
Task 1: Study of the physico-chemical interactions between DOM, soil and pesticides
Task 2: Study of the effect of DOM on pesticide degradation
Task 3: Study of the net-effect of DOM on pesticide transport and biodegradation in soil columns
Task 4:
Effect of DOM on
the transport
of pesticides in field
experiments
Effect of DOM on pesticide degradation
• Two approaches– Effect of DOM on activity of pure
atrazine-degrading cultures– Effect of DOM on activity of soil
microbial communities
Effect of DOM on degradation of atrazine by pure cultures• Atrazine-degrading cultures:
– Nocardioides (SP 12), – Arthrobacter crystallopoietes (SR 30) – Chelatobacter heintzii (SR 38)
(Mandelbaum et al., 1995; Radosevich et al., 1995).
• Atrazine concentration measured by HPLC analysis (start conc 33 mg/l)
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0 2 4 6 8
time [day]
Atr
azin
e [%
of
con
tro
l]
Nocardioides SP 12
Arthrobacter crystallopoietesSR 30
Chelatobacter heintzii SR 38
Effect of DOM on degradation of atrazine by pure cultures
• Test addition of C (mixture glucose, citrate and gluconate) and DOM (CaCl210-2 M extract from Termunck soil)
– Chelatobacter heintzii (SR38)
Media DOC (mg/L)
MMN + C1 10.0
MMN + C2 118.4
MMN + C3 1300.0
DOM (CaCl2extract) 3.6
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0 50 100 150 200 250 300 350
time [hour]
Atr
azin
e [%
of
the
con
tro
l] MMN
MMN+C1
MMN+C2
MMN+C3
DOM
Effect of DOM on degradation of atrazine by pure cultures
• Test addition of C (mixture glucose, citrate and gluconate) and DOM (CaCl210-2 M extract from Termunck soil)
– Arthrobacter crystallopoietes (SR30)
Media DOC (mg/L)
MMN + C1 10.0
MMN + C2 118.4
MMN + C3 1300.0
DOM (CaCl2extract) 3.6
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20,0
40,0
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120,0
0 100 200 300 400 500 600
time [hour]
Atr
azin
e [%
of
the
init
ial] MMN
MMN+C1
MMN+C2
MMN+C3
DOM
Effect of DOM on degradation of atrazine by pure cultures• Effect of DOM on the maximal
degradation rate
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0,5
1,0
1,5
2,0
2,5
MMN MMN+C1 MMN+C2 MMN+C3 DOM
De
gra
da
tio
n r
ate
[%
/ho
ur]
0,0
1,0
2,0
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5,0
MMN MMN+C1 MMN+C2 MMN+C3 DOMD
eg
rad
ati
on
ra
te [
%/h
ou
r]
–Chelatobacter heintzii (SR38) –Arthrobacter crystallopoietes (SR30)
Effect of DOM on mineralisation of atrazine by soil communities
• Mineralisation experiments:– 0,2 g soil + 5 ml medium– ~ 50 µg/l 14C atrazine
– NaOH trap (1 ml 0,5 M) to catch 14C-CO2
Effect of DOM on mineralisation of atrazine by soil communities
SampleLast
treatment
Treatment time
[years]
Maxmineralization
rate[%/day]
Lag time[days]
Mineralistation extent
[% initial 14C]
Bev-1 2005 13 6.0 4.97 30.0
Bev-2 2006 32 6.4 4.48 34.2
Lub 1997 15 3.3 13.72 35.2
TW 2004 10 5.9 11.98 29.0
En-02 2005 2 6.7 8.40 38.1
En-04 2004 1 5.6 8.40 41.7
Ep 1998 10 0.0 0.36 0.8
Effect of DOM on mineralisation of atrazine by soil communities
• Setup: – 0,2 g soil + 5 ml medium– Different media:
• Mineral medium without N (MMN)• CaCl2 10-3 M• DOM extracted from 3 ≠ soils (TM,
18, 73) with CaCl2 10-3 M
– Atrazine 14C: initial: ~ 38 µg/l– Topsoil samples
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
50%
0 10 20 30 40 50
time (day)
%A
Tb
roke
nd
ow
n
CaCl2
MMN
CaCl2 + DOM TM
CaCl2 + DOM 73
CaCl2 + DOM 18
max mineralisation rate
0%
1%
2%
3%
4%
5%
6%
CaCl2 MMN DOM TM DOM 18 DOM 73
% A
T /
day
Effect of DOM on mineralisation of atrazine by soil communities
• DOM from soil 73 (different concentrations) in CaCl2 10-2 M
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
0 200 400 600 800 1000 1200 1400
time (hours)
% A
T b
rok
en
do
wn
100 mg/l
80
60
40
20
0
Effect of DOM on mineralisation of atrazine by soil communities
samples
0
50
100
150
200
250
300
350
400
1 week 2 weeks 3 weeks 4 weeks 5 weeks
mg
C/l
blancos
0
50
100
150
200
250
300
1 week 2 weeks 3 weeks 4 weeks 5 weeks
mg
C/l
DOC concentration in time
Effect of DOM on mineralisation of atrazine by soil communities• Mineralisation capacity tested in different
depths – Sampling in depth (0-60 cm)– Different depths, seperatly incubated:
0-15; 17-30; 32-45; 47-60 cm
Effect of DOM on mineralisation of atrazine by soil communities
• CaCl2 extract -> TOC measurement; divided by kg dry soil
• No clear effect in depth
1.1 1792,7 500,7 2.1 2104,5 104,6 3.1 2488,8 669,4
1.2 3577,2 869,4 2.2 4959,1 1438,0 3.2 3928,1 530,2
1.3 897,0 1315,8 2.3 1858,2 177,0 3.3 1234,9 7,1
1.4 731,8 1062,4 2.4 882,3 1196,6 3.4 1152,1 185,0
DOC / DS (mg/l/kg)
StdevDOC / DS (mg/l/kg)
Mean StdevMean StdevDOC / DS (mg/l/kg)
Mean
Effect of DOM on mineralisation of atrazine by soil communities
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0 200 400 600 800 1000 1200
tijd (uren)
% A
T b
roke
n d
ow
n
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time (hours)
% A
T b
roke
n d
ow
n
layer 1
layer 2
layer 3
layer 4
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0 200 400 600 800 1000 1200
tijd (uren)
% A
T b
roke
n d
ow
n
3 samples, 4 depths
Effect of DOM on mineralisation of atrazine by soil communities
• Different depths + different media:– DOM: extracted from TM soil
(DOM TM)– DOM: Aldrich Humic Acid (AH)– DOM: Humic Acid extracted
from Zegveld soil (ZH)– Salt solution which imitates TM
extract without organic matter
– CaCl2 10-3 M as control
TOC mgC/lDOM TM 9,72AH 75,1ZH 50,8
Layer 1 (topsoil)
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5,00%
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15,00%
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25,00%
30,00%
35,00%
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45,00%
50,00%
0 200 400 600 800 1000 1200 1400
time (h)
% A
T b
roke
n d
ow
n
ZH
CaCl2
AH
DOM TM
salt
layer 2
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5,00%
10,00%
15,00%
20,00%
25,00%
30,00%
0 200 400 600 800 1000 1200 1400
time (h)
% A
T b
roke
n d
ow
n
CaCl2
ZH
AH
DOM TM
salt
layer 3
-5,00%
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30,00%
35,00%
40,00%
45,00%
0 200 400 600 800 1000 1200 1400
time (h)
% A
T b
roke
n d
ow
n
CaCl2
ZH
AH
DOM TM
salt
layer 4
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5,00%
10,00%
15,00%
20,00%
25,00%
30,00%
35,00%
40,00%
45,00%
0 200 400 600 800 1000 1200 1400
time (h)
% A
T b
rok
en
do
wn
CaCl2
ZH
AH
DOM TM
salt
Conclusions Task 2 (pesticide degradation)
• Indications that degradation of atrazine by pure atrazine-degrading cultures was enhanced by additional C
• Mineralisation rate of atrazine in soil was in few cases inhibited by certain DOM solutions -> quality important?
• In depth: faster and higher mineralisation in topsoil, other layers no clear effect of depth
• DOC influence on mineralisation in depth: inhibition by DOM extracted from TM at each depth, but unclear effects of other C-sources
= > Future task 2
• Examine effect of other DOM with different quality and quantity on atrazine degradation
• Examine effect of DOM on soil microbial activity (glucose respiration, nitrification potential)
• Analyse effect of DOM on dynamics of soil communities by means of 16S rDNA based DGGE
• Analyse effect of DOM on dynamics and activity of atrazine degraders by qPCR
Task 1: Study of the physico-chemical interactions between DOM, soil and pesticides
Task 2: Study of the effect of DOM on pesticide degradation
Task 3: Study of the net-effect of DOM on pesticide transport and biodegradation in soil columns
Task 4:
Effect of DOM on
the transport
of pesticides in field
experiments
Field experiment
• Trifluralin added on all plots
• Measurement of trifluralin in samples? – Kd~75 -> retention
time high?
Thanks for your attention !
Questions?