effect of dom quality and quantity on transport and degradation of pesticides

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 4:

Effect of DOM on

the transport


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

0,00

1,00

2,00

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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)


• 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


• 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


• 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

)


• 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)


• 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

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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



0,5 g clean soil, (0,18 % C)

10 ml solution + 14C TFL

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 4:

Effect of DOM on

the transport


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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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

3,0

4,0

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


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


• 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%

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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


• DOM from soil 73 (different concentrations) in CaCl2 10-2 M

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45%

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time (hours)

% A

T b

rok

en

do

wn

100 mg/l

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0


samples

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1 week 2 weeks 3 weeks 4 weeks 5 weeks

mg

C/l

blancos

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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


• 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


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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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0 200 400 600 800 1000 1200

time (hours)

% A

T b

roke

n d

ow

n

layer 1

layer 2

layer 3

layer 4

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35,00%

0 200 400 600 800 1000 1200

tijd (uren)

% A

T b

roke

n d

ow

n

3 samples, 4 depths


• 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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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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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

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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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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 4:

Effect of DOM on

the transport


experiments

Field experiment

• Trifluralin added on all plots

• Measurement of trifluralin in samples? – Kd~75 -> retention

time high?

Thanks for your attention !

Questions?

effect of dom quality and quantity on transport and degradation of pesticides

Documents

effects of dom

structure of dom

dom structure

effect of dom quality

supernatanseffect of

different dom

final effect of dom

domrelated transport