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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.

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Effect of DOM quality and quantity on transport and degradation of pesticides

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  1. 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

  2. ? ? Objectives • To predict the effects of DOM on transport and degradation of pesticides with emphasis on the subsoil environment DOM influences pesticide transport in soil • Physico-chemical? • DOM-related transport and competition • To unravel how DOM quality and quantity affect the dynamics/activity and competence of pesticide degrading populations with emphasis to the subsoil environment Biodegradation? - availabilty? - DOM as C-source (catabolic repression, extra C-source, effect on microbial diversity)

  3. Hypotheses Task 1: Study of the physico-chemical interactions between DOM, soil and pesticides H1: Effects of DOM on transport of pesticides (Trifluralin) depends on the structure of DOM and can be predicted from batch sorption test Task 4: Effect of DOM on the transportof pesticides in field experiments Task 2: Study of the effect of DOM on pesticide degradation H2: Effects of DOM on pesticides (Atrazine) degradation in (sub)soil is the net result of effects on bioavailability and on population dynamics Task 3: Study of the net-effect of DOM on pesticide transport and biodegradation in soil columns H3: The final effect of DOM on the fate of pesticides in soil depends on DOM structure and is concentration dependent

  4. Task 1: Study of the physico-chemical interactions between DOM, soil and pesticides Task 4: Effect of DOM on the transportof pesticides in field experiments 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

  5. Physico-chemical interactions • Emphasis on 2 pesticides (herbicides) • Atrazine: Log Kow= 2,7 • Expected low KDOC • Trifluralin: Log Kow = 4,83 • High KDOC

  6. 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

  7. Effect of DOM on atrazine sorption

  8. Treflan (19,2 mg TFL/kg) Fresh soil TM (2mm) 14C Trifluralin (150 µg/kg) Effect of DOM on trifluralin desorption • Trifluralin: low solubility in water • first spiking soil, then desorption tests in batch with different DOM solutions

  9. Effect of DOM on trifluralin desorption • Batch experiments 24 h desorption 10 ml DOM solution Quench control 10 ml DOM solution 2 g spiked soil 5 ml -> counter 3 ml -> TOC analyser 2 g control soil 5 ml + known # 14C TFL -> counter

  10. 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

  11. Effect of DOM on trifluralin desorption • Theory desorption with DOC

  12. Effect of DOM on trifluralin desorption • Influence pig manure (< 0,45 µm) on TFL desorption

  13. Effect of DOM on trifluralin desorption • Influence Aldrich Humic Acid on TFL desorption (low DOC concentrations)

  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 14C-TFL and DOC concentration of supernatans

  15. Adsorption 10 ml solution + 14C TFL 0,5 g clean soil, (0,18 % C) 5 ml -> counter 3 ml -> TOC analyser Effect of DOM on trifluralin de- and adsorption Desorption 20 ml CaCl2 10-2M 4 g spiked soil 5 ml -> counter 3 ml -> TOC analyser

  16. Effect of DOM on trifluralin de- and adsorption • Testing reversible sorption: -> If reversible sorption: expect 1,4 µg/l after adsorption

  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 H2O with DOM in batch • Abiotic column experiments to test if the batch sorption data explain DOM facilitated leaching

  18. Task 1: Study of the physico-chemical interactions between DOM, soil and pesticides Task 4: Effect of DOM on the transportof pesticides in field experiments 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

  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

  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)

  21. 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)

  22. 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)

  23. Effect of DOM on degradation of atrazine by pure cultures • Effect of DOM on the maximal degradation rate • Arthrobacter crystallopoietes (SR30) • Chelatobacter heintzii (SR38)

  24. 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

  25. Effect of DOM on mineralisation of atrazine by soil communities

  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) • 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

  27. Effect of DOM on mineralisation of atrazine by soil communities • DOM from soil 73 (different concentrations) in CaCl2 10-2 M

  28. Effect of DOM on mineralisation of atrazine by soil communities DOC concentration in time

  29. 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

  30. Effect of DOM on mineralisation of atrazine by soil communities • CaCl2 extract -> TOC measurement; divided by kg dry soil • No clear effect in depth

  31. Effect of DOM on mineralisation of atrazine by soil communities 3 samples, 4 depths

  32. 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

  33. Conclusions Task 2 (pesticide degradation) = > 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 • 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

  34. Task 1: Study of the physico-chemical interactions between DOM, soil and pesticides Task 4: Effect of DOM on the transportof pesticides in field experiments 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

  35. Field experiment • Trifluralin added on all plots • Measurement of trifluralin in samples? • Kd~75 -> retention time high?

  36. Thanks for your attention ! Questions?

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