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Soil Fate and leaching of the natural carcinogen ptaquiloside

DWRIP 2014 KU-SCIENCE. Soil Fate and leaching of the natural carcinogen ptaquiloside.

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Soil Fate and leaching of the natural carcinogen ptaquiloside

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  1. DWRIP 2014 KU-SCIENCE Soil Fate and leaching of the natural carcinogen ptaquiloside Hans Christian Bruun Hansena, Lars H. Rasmussenb, Frederik Clauson-Kaasa, Ole Stig Jacobsenc, Rene K. Juhlerc, Søren Hansena, and Bjarne W. Strobela a Department of Plant and Environmental Sciences, KU-SCIENCE b Metropolitan University College c Department of Geochemistry, Geological Survey of Denmark and Greenland (GEUS)

  2. Azores, Portugal • Bracken form dense ”mats” • Præstø Fed, Denmark • Bracken is ”invasive” – and outcompetes other vegetation.

  3. DWRIP 2014 KU-SCIENCE Why is this important? • Bracken is one of very few plants known to cause cancer in animals • Bracken is everywhere in Nature; 5th most abundant plant on Earth • The carcinogen in Bracken is produced in high amounts (up to 1 % dw) • The carcinogen is very mobile in soil and water • Several exposure routes for humans (air, milk, meat, drinking water) • Little is known

  4. DWRIP 2014 KU-SCIENCE A well known carcinogen in animals - Examples for cattle - • Bovine enzootic haematuria (BEH): Tumours in the urinary bladder of cows and sheeps. Recognized worldwide. Test animals fed bracken produce similar symptoms. • Upper digestive tract carcinomas: Ususally seen in conjunction with papillomavirus that infects the mucosa of the upper digestive tract in cattle. In presence of PTA papillomas transform to carcinomas

  5. DWRIP 2014 KU-SCIENCE Exposure routes for humans • Aranho, P (2013)

  6. DWRIP 2014 KU-SCIENCE • Bracken norsesquiterpene glycosides and hydrolysis products • Hydrolysis • products

  7. DWRIP 2014 KU-SCIENCE • Hydrophobic • Hydrophilic • PTA amphiphilic

  8. DWRIP 2014 KU-SCIENCE • Methods used for determination of PTA and PTB

  9. DWRIP 2014 KU-SCIENCE PTA production, distribution and hydrolysis in soil and water

  10. DWRIP 2014 KU-SCIENCE Bracken growth, PTA contents and PTA loads • PTA contents in fronds during growing season at different sites in DK and UK • PTA in fronds (ug g-1) • Aug • PTA content in fronds per m2 land surface during growing season at different sites in DK • 300 mg m-2 = 3 kg ha-1 • PTA load (mg m-2) • May • Rasmussen (2003) • Julian day number

  11. DWRIP 2014 KU-SCIENCE High variation in PTA content between bracken populations • Rasmussen (2003)

  12. DWRIP 2014 KU-SCIENCE • Hydrolysis of PTA • kA = 25.7 h-1 M-1; kN = 9.49 10-4; h-1 M-1; kB = 4.83 104 h-1 M-1 • - Half-lives at pH 4, 6 and 8 (25 oC): 8 d, 20 d, and 0.6 d • - Low temperatures increase half-lives considerably • Ayala et al. (2006)

  13. DWRIP 2014 KU-SCIENCE • Microbial contribution to PTA degradation • Degradation of PTA in soils at field moisture and 10 oC with initial PTA concentration of 25 g kg-1 • Fast reaction: Abiotic • Slow reaction: Biotic + Abiotic • open symbols: sterilized; closed symbols: untreated soil • Ovesen et al. (2008)

  14. DWRIP 2014 KU-SCIENCE Can degradation in soil be attributed to hydrolysis in solution phase? • Hydrolysis in soil solution • Kinetics of PTA degradation in soil solutions from sandy and clayey top- and subsoils (10 oC). • Open symbols represent solutions filtered (0.2 µm) before incubation; closed symbols unfiltered solutions. • !! No significant hydrolysis • PTA is stabilized in soil solution! • pH 4.5 - 7 • Ovesen et al. (2008)

  15. DWRIP 2014 KU-SCIENCE Leaching

  16. DWRIP 2014 KU-SCIENCE • PTA and PTB in shallow groundwater at Bracken infested areas • Study sites • Sampling in small inspection wells. • Determination of PTA and PTB by a SPE-LC-MS/MS • Clauson-Kaas et al. (2014)

  17. DWRIP 2014 KU-SCIENCE • PTA and PTB distribution in soil • PTAw, PTBw: Extracted with water • PTBa: Extracted with methanol • - PTA concentrations highest in the litter layer, but much higher total quantities in the mineral soil • Higher PTB than PTB concentrations in mineral soil • PTB as ”memory” effect of PTA? • Clauson-Kaas et al. (2014)

  18. DWRIP 2014 KU-SCIENCE • Observed groundwater concentrations of • PTA and PTB (µg L-1) • T = trace • - PTA could be detected at all sites • - Max. PTA concentration observed 0.09 ug L-1; max PTB observed 0.49 ug L-1. • - Big variations over time! • Clauson-Kaas et al. (2014)

  19. DWRIP 2014 KU-SCIENCE • Observed concentrations of PTA in pond • water near Bracken stands (µg L-1) • T = trace • - PTA detected in all surface waters • - max. PTA concentration 1.1 g L-1; max. PTB concentration 0.56 g L-1. • - Large temporal and spatial variation • Clauson-Kaas et al. (2014)

  20. DWRIP 2014 KU-SCIENCE • Modelling of PTA leaching from a sandy soil using the DAISY Plant-Soil-Water model • - First attempt - • PTA production: Biomass production data of Rasmussen and Hansen (2002) • PTA in biomass: 200 g g-1 DM (low) • PTAsoil transfer: Leaching from fronds (Rasmussen et al., 2003), and decaying plants (frost for 3 consecutive days) • Soil: Sandy soil (Præstø), 2 - 6 % of clay • Hydraulic properties estimated according to Mualen and van Genuchten • PTA degradation: Model from Ovesen et al. (2008) • Climate data: Data for Zealand (Højbakkegaard) 1962 - 2001 used. • Modelling: Leaching modelled for the period 1962 - 2001, and for a selected 1-year period (1967 - 1968).

  21. DWRIP 2014 KU-SCIENCE • Modelling results for the period 1962 - 2002 • Separate degradation rate constants have been used for O, A and B soil horizons for fast and slow degrading PTA pools • Annual total PTA addition to soil 1.6 kg ha-1. • Note the extremely variable soil contents and amounts of PTA leached

  22. DWRIP 2014 KU-SCIENCE • Conclusions • PTA proven animal and suspected human carcinogen. • PTA production of kg ha-1 y-1. High spatial and temporal variation. • Initial PTA degradation due to hydrolysis; highly sensitive to pH and temperature. Apparent stabilization in soil water • Fast abiotic and slower biotic degradation of PTA in soil; stabilization of PTA in soil by clays. • Sorption of PTA in soil is insignificant  fast leaching • PTA and PTB present in groundwater and surface water; µg L-1 to ng L-1 range • Groundwater and surface water monitoring is strongly needed; high time and spatial resolution is critical.

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