Effect of DOM quality and quantity on transport and degradation of pesticides Karlien Cheyns,...
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Effect of DOM quality and quantity on transport and degradation of pesticides Karlien Cheyns, Mariangiola Mollicone, Stien Van Gestel Dirk Springael, Erik
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
Slide 2
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
Slide 3
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
Slide 4
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
Slide 5
Physico-chemical interactions Emphasis on 2 pesticides
(herbicides) Atrazine: Log K ow = 2,7 Expected low K DOC
Trifluralin: Log K ow = 4,83 High K DOC
Slide 6
Effect of DOM on atrazine sorption Batch sorption tests with or
without extra DOC: Solution of AT (~100 g/L) and different DOM
shaken with soil (2:1 l:s) After equilibrium (24h): analysis of AT
and DOC concentration in supernatans
Slide 7
Effect of DOM on atrazine sorption
Slide 8
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) 14 C Trifluralin (150 g/kg)
Slide 9
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 -> counter 3 ml -> TOC
analyser 5 ml + known # 14 C TFL -> counter
Slide 10
Effect of DOM on trifluralin desorption Theory desorption with
DOC K d * = K om oc/(1+K DOC C DOC ) Estimate K om from logK om
=0,72logK ow + 0,49 (Schwarzenbach and Westall, 1981) logK ow =4,83
=> logK om = 3,97
Slide 11
Effect of DOM on trifluralin desorption Theory desorption with
DOC
Slide 12
Effect of DOM on trifluralin desorption Influence pig manure
(< 0,45 m) on TFL desorption
Slide 13
Effect of DOM on trifluralin desorption Influence Aldrich Humic
Acid on TFL desorption (low DOC concentrations)
Slide 14
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 14 C-TFL and DOC concentration of supernatans
Slide 15
4 g spiked soil 20 ml CaCl 2 10 -2 M Desorption 5 ml ->
counter 3 ml -> TOC analyser Effect of DOM on trifluralin de-
and adsorption 0,5 g clean soil, (0,18 % C) 10 ml solution + 14 C
TFL Adsorption 5 ml -> counter 3 ml -> TOC analyser
Slide 16
Effect of DOM on trifluralin de- and adsorption Testing
reversible sorption: -> If reversible sorption: expect 1,4 g/l
after adsorption
Slide 17
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 H 2 O with DOM in batch Abiotic column
experiments to test if the batch sorption data explain DOM
facilitated leaching
Slide 18
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
Slide 19
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
Slide 20
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)
Slide 21
Effect of DOM on degradation of atrazine by pure cultures Test
addition of C (mixture glucose, citrate and gluconate) and DOM
(CaCl 2 10 -2 M extract from Termunck soil) Chelatobacter heintzii
(SR38) MediaDOC (mg/L) MMN + C110.0 MMN + C2118.4 MMN + C31300.0
DOM (CaCl 2 extract) 3.6
Slide 22
Effect of DOM on degradation of atrazine by pure cultures Test
addition of C (mixture glucose, citrate and gluconate) and DOM
(CaCl 2 10 -2 M extract from Termunck soil) Arthrobacter
crystallopoietes (SR30) MediaDOC (mg/L) MMN + C110.0 MMN + C2118.4
MMN + C31300.0 DOM (CaCl 2 extract) 3.6
Slide 23
Effect of DOM on degradation of atrazine by pure cultures
Effect of DOM on the maximal degradation rate Chelatobacter
heintzii (SR38) Arthrobacter crystallopoietes (SR30)
Slide 24
Effect of DOM on mineralisation of atrazine by soil communities
Mineralisation experiments: 0,2 g soil + 5 ml medium ~ 50 g/l 14 C
atrazine NaOH trap (1 ml 0,5 M) to catch 14 C-CO 2
Slide 25
Effect of DOM on mineralisation of atrazine by soil communities
Sample Last treatment Treatment time [years] Max mineralization
rate [%/day] Lag time [days] Mineralistation extent [% initial 14
C] Bev-12005136.04.9730.0 Bev-22006326.44.4834.2
Lub1997153.313.7235.2 TW2004105.911.9829.0 En-02200526.78.4038.1
En-04200415.68.4041.7 Ep1998100.00.360.8
Slide 26
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) CaCl 2 10 -3 M DOM extracted from 3 soils (TM, 18,
73) with CaCl 2 10 -3 M Atrazine 14 C: initial: ~ 38 g/l Topsoil
samples
Slide 27
Slide 28
Effect of DOM on mineralisation of atrazine by soil communities
DOM from soil 73 (different concentrations) in CaCl 2 10 -2 M
Slide 29
Effect of DOM on mineralisation of atrazine by soil communities
DOC concentration in time
Slide 30
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
Slide 31
Effect of DOM on mineralisation of atrazine by soil communities
CaCl 2 extract -> TOC measurement; divided by kg dry soil No
clear effect in depth
Slide 32
Effect of DOM on mineralisation of atrazine by soil communities
3 samples, 4 depths
Slide 33
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 CaCl 2 10 -3 M as control
Slide 34
Slide 35
Slide 36
Slide 37
Slide 38
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
Slide 39
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
Slide 40
Field experiment Trifluralin added on all plots Measurement of
trifluralin in samples? Kd~75 -> retention time high?
