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As and Cr Speciation of New & Weathered CCA-Treated Wood

As and Cr Speciation of New & Weathered CCA-Treated Wood. Outline. Purpose Basic As and Cr Chemistry Solvent-Extraction Leaching Experiments (Cr & As) As Analysis of GW at Florida C&D Landfills As Leaching from Lysimeters. Purpose & Motivation of Study.

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As and Cr Speciation of New & Weathered CCA-Treated Wood

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  1. As and Cr Speciation of New & Weathered CCA-Treated Wood

  2. Outline • Purpose • Basic As and Cr Chemistry • Solvent-Extraction Leaching Experiments (Cr & As) • As Analysis of GW at Florida C&D Landfills • As Leaching from Lysimeters

  3. Purpose & Motivation of Study • Quantify As & Cr species in leachates from CCA-treated wood • As & Cr toxicity varies with each specie • As & Cr mobility varies with each specie • Estimate the impact of As & Cr leaching from • in-service & disposed CCA-treated wood on • groundwater

  4. As Speciation Arsenic Valence -3 0 +1 +3 +5 Arsine (g) Inorganic Inorganic Organic As(V) MMAA DMAA As(III)

  5. Toxicity & Mobility As Speciation Arsenic Valence -3 0 +1 +3 +5 Arsine (g) Inorganic Inorganic Organic As(V) MMAA DMAA As(III)

  6. Toxicity & Mobility Toxicity & Mobility As Speciation Arsenic Valence -3 0 +1 +3 +5 Arsine (g) Inorganic Inorganic Organic As(V) MMAA DMAA As(III)

  7. Toxicity & Mobility Cr Speciation Cr Speciation Chromium Valence +6 +3 0 Inorganic Inorganic Cr(VI) Cr(III)

  8. Analytical Methods for Speciation • As: HPLC-ICP-MS or HPLC-HG-AFS • Cr: IC for Cr(VI) • Total Cr by ICP-AES • Cr(III) by difference

  9. Solvent Extraction Study

  10. Solvent-Extraction of CCA-Treated Wood CCA-treated wood subjected to leaching solvent, rotated for 18  2 hrs & filtered. Filtrate analyzed for As & Cr species pH 1,2,3. etc.. Untreated 0.25 pcf 0.6 pcf 2.5 pcf TCLP New CCA-treated wood SPLP DI Water Playground Utility pole Fence C&D waste Weathered CCA-treated wood Rainwater

  11. 40 35 30 25 20 Arsenic Concentration (mg/L) 15 10 5 0 6.00 1.00 2.00 3.00 4.00 5.00 6.28 6.93 7.52 7.96 9.13 10.90 12.65 pH pH Experiment - New Wood (0.32 pcf) Total As (As(V)) – HPLC-HG-AFS Total As – ICP-AES Environmental pH • As(V) was the only specie detected • Highest concentration at extreme pH • Environmental pH range ~ 5mg/L

  12. As(III) As(V) Total As - HPLC-HG-AFS Total As – ICP-AES 45 40 35 30 25 20 Arsenic Concentration (mg/L) 15 10 5 0 1.27 2.56 3.72 4.15 5.16 5.41 6.54 8.04 9.43 10.19 10.68 11.91 12.76 pH pH Experiment - Weathered Wood (0.41 pcf) Environmental pH • As(III) & As(V) detected, As(III) up to pH 9.5 • Environmental pH range – Total As increase • Total As > 5 mg/L

  13. 12 10 8 6 4 2 0 I (9.12) E (3.86) S (3.16) P (1.96) F (3.62) T (1.41) B (4.06) R (5.47) J (46.01) D (5.90) C (5.63) A (1.49) V (1.86) Q (5.79) O (5.28) N (6.26) L (27.54) G (13.03) H (24.57) K (20.37) M (24.05) SPLP New & Weathered Wood (Simulated Rain Water) Weathered New SPLP As(III) As(V) Total As Arsenic Concentration (mg/L) Retention (kg/m3)

  14. Leachate As Conc. vs CCA Retention 10 New 9 SPLP Rainwater TCLP DI Water Seawater 8 7 Total As Conc. (mg/L) 6 5 4 3 2 1 0 kg/m3 0 5 10 15 20 25 30 35 40 45 50 14 Weathered 12 10 Total As Conc. (mg/L) 8 6 4 2 0 kg/m3 0 2 4 6 8 10 12 14 16 18 20 22 24 26

  15. pH Experiment - New Wood (0.32 pcf) Environmental pH • Cr(III) predominates • Cr(VI) observed at high pH values

  16. SPLP New & Weathered Wood (Simulated Rain Water) • Unburned wood Cr as Cr(III) • No Cr(VI) observed

  17. Ash – SPLP and TCLP • Ashing results in converstion of Cr(III) to Cr(VI) • Cr in ash leachate exists as Cr(VI)

  18. Low Retention Level Wood Leaches More Cr Ash Results for Chromium

  19. Summary • As & Cr species leaching pH dependent • At environmental pH range (6-10) • - As ~ 5mg/L • - Cr ~ 1 mg/L • More As leaching from weathered wood than new wood  As(III) • As Leaching in rainwater, TCLP, SPLP comparable. Seawater less. • Incineration results in the conversion of some Cr(III) to Cr(VI). Greater conversion for lower retention levels.

  20. ? ? ? Questions

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