Emissions of Chromium, Copper, Arsenic, and PCDDs/Fs from Open Burning of CCA-Treated Wood
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- 作者：Shirley J. Wasson ; William P. Linak ; Brian K. Gullett ; Charles J. King ; Abderrahmane Touati ; Frank E. Huggins ; Yuanzhi Chen ; Naresh Shah ; and Gerald P. Huffman
- 刊名：Environmental Science & Technology
- 出版年：2005
- 出版时间：November 15, 2005
- 年：2005
- 卷：39
- 期：22
- 页码：8865 - 8876
- 全文大小：231K
- 年卷期：v.39,no.22(November 15, 2005)
- ISSN：1520-5851
文摘
Aged and weathered chromated copper arsenate (CCA)treated wood was burned in an open burn researchfacility to characterize the air emissions and residual ash.The objectives were to simulate, to the extent possible,the combustion of such waste wood as might occur in anopen field or someone's backyard; to characterize thecomposition and particle size distribution (PSD) of the emittedfly ash; to determine the partitioning of arsenic, chromium,and copper between the fly ash and residual ash; andto examine the speciation of the CCA elements. This workreports preliminary air emission concentrations andestimated emission factors for total particulate matter,arsenic (As), chromium (Cr), copper (Cu), and polychlorinateddibenzodioxins/dibenzofurans (PCDD/F) totals and toxicequivalents (TEQs). The partitioning of As, Cr, and Cu betweenthe emitted fly ash and residual ash is examined andthermochemical predictions from the literature are usedto explain the observed behavior. Results indicate a unimodalfly ash PSD between 0.1 and 1.0 
m diameter. In additionto a large carbonaceous component, between 11 and14% of the As present in the burned CCA treated woodwas emitted with the air emissions, with the remainderpresent in the residual ash. In contrast, less than 1% of boththe Cr and Cu present in the wood was emitted with theair emissions. PCDD/F levels were unremarkable, averaging1.7 ng TEQ/kg of treated wood burned, a value typicalfor wood combustion. Scanning electron microscopy (SEM)was unable to resolve inorganic particles consisting ofCu, Cr, or As in the wood samples, but X-ray absorptionfine structure (XAFS) spectroscopy confirmed that theoxidation states of the CCA elements in the wood wereCu2+, Cr3+, and As5+. SEM examination of the fly ash samplesrevealed some inorganic microcrystals within the mostlycarbonaceous fly ash, while XAFS spectroscopy of the samesamples showed that the oxidation states after combustionwere mixed Cu+ and Cu2+, Cr3+, and mixed As3+ andAs5+. Estimates of the ratios of the mixed oxidation statesbased on the XAFS spectra were As3+/(total As) = 0.8-0.9 and Cu+/(total Cu) = 0.65-0.7. The Cu and Cr present inthe fly ash were determined to coexist predominantly inthe two oxide phases CuCrO2 and CuCr2O4. These resultsindicate that the open burning of CCA-treated wood can leadto significant air emissions of the more toxic trivalentform of As in particle sizes that are most respirable.
m diameter. In additionto a large carbonaceous component, between 11 and14% of the As present in the burned CCA treated woodwas emitted with the air emissions, with the remainderpresent in the residual ash. In contrast, less than 1% of boththe Cr and Cu present in the wood was emitted with theair emissions. PCDD/F levels were unremarkable, averaging1.7 ng TEQ/kg of treated wood burned, a value typicalfor wood combustion. Scanning electron microscopy (SEM)was unable to resolve inorganic particles consisting ofCu, Cr, or As in the wood samples, but X-ray absorptionfine structure (XAFS) spectroscopy confirmed that theoxidation states of the CCA elements in the wood wereCu2+, Cr3+, and As5+. SEM examination of the fly ash samplesrevealed some inorganic microcrystals within the mostlycarbonaceous fly ash, while XAFS spectroscopy of the samesamples showed that the oxidation states after combustionwere mixed Cu+ and Cu2+, Cr3+, and mixed As3+ andAs5+. Estimates of the ratios of the mixed oxidation statesbased on the XAFS spectra were As3+/(total As) = 0.8-0.9 and Cu+/(total Cu) = 0.65-0.7. The Cu and Cr present inthe fly ash were determined to coexist predominantly inthe two oxide phases CuCrO2 and CuCr2O4. These resultsindicate that the open burning of CCA-treated wood can leadto significant air emissions of the more toxic trivalentform of As in particle sizes that are most respirable.