Arsenic Speciation of CCA-Treated Wood Bernine Khan University of Miami May 6th, 2002

Purpose: Speciation analysis - to identify & quantify the arsenic species leaching from CCA-treated wood Interest of individual arsenic species? Arsenic toxicity varies with each species Species of interests to this study: Inorganic - As(III) & As(V) Organic – MMAA & DMAA Purpose of Study

Speciation Arsenic As(III) As(V)MMAADMAA Various forms of an element that make up the total concentration of that element Inorganic Organic Valence Inorganic Arsine (g)

Speciation Arsenic As(III) As(V)MMAADMAA Various forms of an element that make up the total concentration of that element Inorganic Organic Valence Inorganic Arsine (g)

In nature, arsenic compounds primarily exist in two oxidation states – arsenites [As(III)] (+3) & arsenates [As(V)] (+5) Soluble arsenic compounds are toxic to humans than insoluble arsenic As(III) - more soluble in water & body fluids Toxicity Interest in Speciation

In nature, arsenic compounds primarily exist in two oxidation states Soluble arsenic compounds are toxic to humans (eg. sodium arsenite, arsenic acid). Insoluble arsenic possess few toxic properties As(III) - more soluble in water & body fluids Toxicity Interest in Speciation

In nature, arsenic compounds primarily exist in two oxidation states Soluble arsenic compounds are more toxic to humans than insoluble arsenic As(III) compounds generally more soluble in water & body fluids – not excreted readily – accumulates in body – toxic at low concentrations Toxicity Interest in Speciation

In nature, arsenic compounds primarily exist in two oxidation states Soluble arsenic compounds are toxic to humans than insoluble arsenic As(III) - soluble in water & body fluids Toxicity is dependent upon: - arsenic compound - magnitude of exposure (conc. accumulated over time) - species Interest in Speciation

Toxicity of Arsenic Species Dependent on chemical form AsH 3 - arsine (gas) – most toxic (formed under reduced conditions eg. landfills) As(III) - arsenite As(V) - arsenate MMAA - monomethylarsonic acid DMAA - dimethylarsinic acid TMAO - trimethylarsine oxide AsB - arsenobetaine (marine) * AsC - arsenocholine (marine) *

Toxicity of Arsenic Species Dependent on chemical form AsH 3 - arsine (gas) As(III) - arsenite – inorganic (more toxic) As(V) - arsenate – inorganic - CCA MMAA - monomethylarsonic acid DMAA - dimethylarsinic acid TMAO - trimethylarsine oxide AsB - arsenobetaine (marine) * AsC - arsenocholine (marine) *

Toxicity of Arsenic Species Dependent on chemical form AsH 3 - arsine (gas) As(III) - arsenite – inorganic As(V) - arsenate – inorganic MMAA - monomethylarsonic acid DMAA - dimethylarsinic acid TMAO - trimethylarsine oxide AsB - arsenobetaine (marine) * AsC - arsenocholine (marine) * bacteria

Toxicity of Arsenic Species Dependent on chemical form AsH 3 - arsine (gas) As(III) - arsenite – inorganic As(V) - arsenate – inorganic MMAA - monomethylarsonic acid DMAA - dimethylarsinic acid TMAO - trimethylarsine oxide AsB - arsenobetaine (marine) * AsC - arsenocholine (marine) *

To Study Arsenic Leaching From CCA- Treated Wood Group 1 - Controlled Laboratory Batch Experiments Group 2 - Controlled Field-Scale Experiments Group 3 - Uncontrolled Field-Scale Experiments Study Setup:

Group 1 - Controlled Laboratory Batch Experiments pH Stat – Leaching of As species under different pH conditions (similar to TCLP) TCLP – Should treated wood waste be considered hazardous SPLP – Should treated wood waste be land applied Solvent-Extraction – Leaching characteristics from Deionized Water, Rainwater, & Seawater

Group 2 - Controlled Field-Scale Experiments Lysimeter Study – Leaching of As species under simulated MSW and C&D landfill conditions using field columns Deck Study – Leaching of As species from a field built treated deck

Group 3 - Uncontrolled Field-Scale Experiments Testing of Groundwater & Landfill Leachate – Identify & quantify As species found at MSW and C&D landfills

Group 1 - Controlled Laboratory Batch Experiments pH Stat Unburned CCA-treated wood subjected to leaching solvent (HNO 3 or NaOH – to obtain desired pH) New (0.4 pcf) CCA-treated wood measured at pcf pH Used (0.4 pcf) CCA-treated wood measured at pcf

Results of pH Stat New Wood As(V) was the only specie detected Highest concentration at extreme pH Environmental pH range – As(V) ~ 5mg/L TCLP 5 mg/L Environmental pH

Results of pH Stat Used Wood Both As(III) & As(V) detected As(III) up to pH 8.5 Environmental pH range – Total As increase Total As > 5 mg/L TCLP 5 mg/L As(III) As(V) Total Environmental pH

Results of pH Stat Total Arsenic More As from new wood – pH (40 – 9 mg/L) More As from used wood – pH (9 – 27 mg/L) Total arsenic conc. (mg/L) New (0.214 pcf) Used (0.386 pcf) – 14 yrs TCLP 5 mg/L Environmental pH

Summary of Results pH Stat Species - New – As(V), Used - As(V) & As(III) pH significant in As leaching As(III) due to biological factors More As leaching from new wood at pH 1 to 3 – more As on new wood surface – easily released under acidic conditions More As from used wood at pH 3 to 12 - Higher retention - Age of wood – weakening release more As - As(III) - more mobile specie & may not bind as strongly as As(V) to the wood

Group 1 - Controlled Laboratory Batch Experiments TCLP & SPLP Unburned CCA-treated wood & CCA-treated wood ash subjected to leaching solvent & rotated for 18  2 hrs. Unburned CCA-treated wood CCA-treated wood ash TCLP SPLP TCLP SPLP Untreated 0.25 pcf 0.6 pcf Weathered (0.6 pcf) 2.5 pcf C&D 1 C&D 3

Results of TCLP Unburned Wood TCLP 5 mg/L As(III) As(V) Total untreated 0.25 pcf0.6 pcf weathered 2.5 pcf C&D 1 C&D 3 - As(III) highest - weathered wood - As(V) highest pcf - Total As increased with increasing retention - As from 0.6 pcf weathered > 0.6 pcf new wood

Results of TCLP Wood Ash TCLP 5 mg/L As(III) As(V) Total untreated 0.25 pcf0.6 pcf weathered 2.5 pcf C&D 1 C&D 3 - As(III) highest – 2.5 pcf - As(V) highest pcf - Total As increased with increasing retention - As from 0.6 pcf weathered > 0.6 pcf new wood

Results of SPLP Unburned Wood SPLP 0.05 mg/L As(III) As(V) Total untreated 0.25 pcf0.6 pcf weathered 2.5 pcf C&D 1 C&D 3 - As(III) highest - weathered wood - As(V) highest – 0.6 pcf - Total As increased to 0.6 pcf & decline at 2.5 pcf - As from 0.6 pcf weathered > 0.6 pcf new wood

Results of SPLP Wood Ash SPLP 0.05 mg/L As(III) As(V) Total untreated 0.25 pcf0.6 pcf weathered 2.5 pcf C&D 1 C&D 3 - As(III) highest – 2.5 pcf - As(V) highest pcf - Total As increased with increasing retention - As from 0.6 pcf weathered < 0.6 pcf new wood

Results of TCLP & SPLP Sample Untreated 0.25 pcf 0.6 pcf Weathered 2.5 pcf C&D 1 C&D 3 TCLP (U) TCLP (A) SPLP U) SPLP (A) Total As – mg/LFail TCLP – 5mg/L U – unburned woodFail SPLP – 0.05 mg/L A - ash

Summary of Results TCLP & SPLP Ash samples leached considerably more As - Ash (new) ~118 to 245 mg/L (TCLP) ~ 53 to 330 mg/L (SPLP) - Unburned (new) ~3 to 10 mg/L (TCLP) ~ 3 to 6 mg/L (SPLP) As(III) predominant in weathered than new Overall As leaching for SPLP < TCLP - SPLP (pH ~4.22) & TCLP (pH ~4.93) - As release sensitive to small pH changes All failed TCLP & SPLP regulatory limit set forth for other arsenic-containing wastes

Group 1 - Controlled Laboratory Batch Experiments Solvent-Extraction – Deionized Water Unburned CCA-treated wood subjected to deionized water & rotated for 18  2 hrs. Unburned CCA-treated wood Untreated 0.25 pcf 0.6 pcf Weathered (0.6 pcf) 2.5 pcf C&D 1 C&D 2

Results of Deionized Water (Hypothetical Scenario) As(III) As(V) Total untreated 0.25 pcf0.6 pcf weathered 2.5 pcf C&D 1 C&D 3 - As(III) highest - weathered wood - As(V) highest – 0.6 pcf - Total As increased to 0.6 pcf & decline at 2.5 pcf - As from 0.6 pcf weathered > 0.6 pcf new wood

Summary of Results of Deionized Water Unburned (new) ~2.5 to 4.5 mg/L Unburned (weathered) ~ 5 mg/L As(III) predominant in weathered pH of deionized water ~ pH of new wood sample ~4.3 - pH of weathered sample ~5.2 - DI water -no buffering capacity - CCA chemical caused acidic leachate - One factor that drives As leaching - pH

Group 2 - Controlled Field-Scale Experiments Lysimeter Study - to be discussed by Jenna Jambeck (University of Florida) Deck Study – to be discussed by Dr. Helena Solo-Gabriele (University of Miami)

Tasks to be Completed Group 1- Controlled Lab Batch Expt - Rainwater & Seawater Extraction Group 2 - Controlled Field-Scale Expt - Lysimeter study – awaiting rainfall - Deck study – deck completion (end of May) Group 3 - Uncontrolled Field-Scale Expt - Re-collect & re-analyze groundwater & landfill leachate in Florida

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