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Leaching of Alternative Chemical Treated Wood & Aquatic Toxicity of Alternative Chemical Treated Wood Leachates

Leaching of Alternative Chemical Treated Wood & Aquatic Toxicity of Alternative Chemical Treated Wood Leachates. Update: July 9, 2001 . “ Chemical and Toxicity Characterization of Pressure Treated Wood Leachate.”. Kristin Stook Master of Engineering Thesis. Rationale.

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Leaching of Alternative Chemical Treated Wood & Aquatic Toxicity of Alternative Chemical Treated Wood Leachates

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  1. Leaching of Alternative Chemical Treated Wood&Aquatic Toxicity of Alternative Chemical Treated Wood Leachates Update: July 9, 2001

  2. “Chemicaland Toxicity Characterization of Pressure Treated Wood Leachate.” • Kristin Stook • Master of Engineering Thesis

  3. Rationale • Research in previous years found that alternative wood preservatives had advantages over CCA with respect to disposal issues and human toxicity issues • Aquatic toxicity of alternatives raised as an issue

  4. Objectives • Conduct a side-by-side comparison of CCA-treated wood and alternative chemical-treated wood with respect to chemical leaching and aquatic toxicity of leachates • Gather basic data that can be used as part of overall assessment of preserved wood types

  5. Status Chemical Analysis Interpretation&Recommendations Aquatic ToxicityAnalysis

  6. Leaching of Alternative Chemical Treated Wood Update: July 9, 2001

  7. Wood Preservatives • CCA- chromated copper arsenate • ACQ- alkaline copper quaternary • CBA- copper boron azole • CC- copper citrate • CDDC- copper dimethyldithiocarbamate

  8. Wood Preservative Components

  9. Sample Preparation

  10. Wood Preservation • Wood was selected based on certain criteria • One (2’) section of each piece of untreated dimensional lumber was sent for treatment • ½ to UM and ½ to UF

  11. Size Reduction • Cut wood using a 10’’ miter saw • Ground using a pulverizer

  12. Leaching Tests • SPLP- Synthetic Precipitation Leaching Procedure • TCLP- Toxicity Characteristic Leaching Procedure • Synthetic seawater (Instant Ocean) • DI water

  13. Analytical Procedures

  14. Chemical LeachingResults

  15. Start with CCA-Treated Wood

  16. Arsenic Concentrations Found in CCA-treated Wood Leachates TC= 5 mg/L DI TCLP SPLP SW

  17. DI TCLP SPLP SW Copper Concentrations Found in CCA-treated Wood Leachates

  18. DI TCLP SPLP SW Chromium Concentrations Found in CCA-treated Wood Leachates

  19. Difference in Leaching Tests for Alternative Chemical Treated Wood

  20. Copper Boron Azole

  21. General Observations about Leaching Tests • For copper, TCLP and saltwater extract the most (DI and SPLP are equivalent) • TCLP extracts the most chromium • Arsenic leaching approximately equal for TCLP, SPLP and DI • Organic chemicals for the most part leach independent of leaching fluid

  22. Compare Copper Leachability

  23. Comparison of Copper Leachability(concentration in mg/l) SPLP

  24. Comparison of Copper Leachability(mass leaching in %) SPLP

  25. Comparison of Total Metal Leachability(mass leaching in %) SPLP

  26. Observations • CCA treated wood leaching similar to previous tests (SPLP, TCLP) • Copper concentrations greater in alternative treated wood leachates • The mass percentage of copper that leaches is higher • The mass percentage of organic components that leach is chemical specific

  27. Remaining Work • Boron analysis • Interpretation

  28. Aquatic Toxicity of Alternative Chemical Treated Wood Leachates Update: July 9, 2001

  29. Aquatic Toxicity Assays Why conduct? Chemical leaching data can not account for other factors that affect aquatic toxicity, such as complexation, binding, interaction, etc…

  30. MetPLATETM • Metal bioavailability • Short term acute toxicity assay • 96-well microplate • CPRG- enzyme • Absorbance measured at 570 nm

  31. Microtox • General toxicity assay • Uses the decrease in the bioluminescence of the marine organism Vibrio fisherii to measure aquatic toxicity

  32. Selenastrum capricornutum • Chronic toxicity assay • 96-hr test • Relative inhibition of the leachates is measured based on a negative control

  33. 48 hour acute bioassay Samples analyzed in triplicate with 5 dilutions Ten neonates per sample Count the number of live/dead neonates Ceriodaphnia dubia

  34. Toxicity Expressions • EC50- mg/L or percent • LC50- mg/L or percent • IC50- mg/L or percent

  35. How Do Toxicity Tests Compare? • Let’s look at results on CDDC on SPLP leachate

  36. Comparison of Toxicity Tests(SPLP Leaching of CDDC)

  37. SPLP

  38. SPLP

  39. Copper as a Surrogate • Literature suggests that the copper leached from CCA is the primary toxicant to aquatic organisms • Does this apply to the alternative wood preservatives as well?

  40. Leachate EC50s (C.dubia) vs. Copper Concentrations

  41. C.dubia Copper/Leachate Comparison

  42. General Observations • Alternative chemical treated wood chemicals exhibit a greater degree of aquatic toxicity • Most sensitive tests are algae and daphnia, followed by Metplate and Microtox

  43. Next Steps • Conduct hormonally active chemical assay • Determine the relative contribution of copper and the co-biocides to aquatic toxicity • Make recommendations on how to use the data in the decision-making process

  44. Questions?

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