Effect of DOM quality and quantity on transport and degradation of pesticides - PowerPoint PPT Presentation

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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?