Different species of arsenic and chromium are characterized by different toxicities and different mobilities. The environmental impacts of CCA-treated wood would therefore be a function of the chemical forms of the metal releases. As a consequence a series of tasks were undertaken to evaluate arsenic and chromium species from CCA-treated wood. The intent of these tasks was to quantify the total quantity of metals released under different environmental conditions and to obtain some insight concerning the speciation of these releases. Samples evaluated in this study were speciated for arsenic as As(V), As(III), DMAA, and MMAA. Chromium speciation focused on evaluating the relative distribution of total chromium between Cr(III) and Cr(VI). Analyses were conducted on solid wood samples and on leachates from these wood samples using a series of different analytical techniques including HPLC-HG-AFS, HPLC-ICP-MS, ICP-AES, and ion chromatography. Tasks described in this study include: a) a "pH stat" experiment, b) SPLP and TCLP experiments, c) a set of lysimeter experiments, and d) analysis of groundwater in the vicinity of C&D landfills. The "pH stat" experiment focused on evaluating the distribution of different arsenic and chromium species with changes in pH. Two types of CCA-treated wood were evaluated, new CCA-treated wood and weathered CCA-treated wood. Results indicate that leaching of arsenic and chromium is enhanced at the pH extremes. Relative to new wood, the weathered wood sample leached greater quantities of arsenic and chromium within the near neutral pH range with total arsenic concentrations between 4 and 5 mg/L and total chromium concentrations between 1 and 2 mg/L range. The enhanced leaching of weathered wood may be due to the higher retention level and/or due to the age of the wood. Of interest is the finding that As(III) was observed to leach only from the weathered wood sample between a pH of 1 to 7. Cr(VI) was observed in both new and weathered wood at pH values greater than 9. The SPLP and TCLP experiments simulated leaching due to rainfall and landfill conditions. Samples evaluated in this portion of the study included unburned wood and wood ash. Results for unburned wood indicated that a weathered utility pole sample consistently leached a significant fraction of arsenic as As(III) in both the TCLP and SPLP tests, whereas the unweathered samples leached much smaller quantities of As(III). Upon sample ashing, As(III) was observed in significant quantities within the leachates from the 40 kg/m3-ash sample. Chromium leached from unburned wood as Cr(III) and from the ash as Cr(VI). Chromium leaching from the ash was found to be strongly dependent upon pH. The pH effect for chromium is likely influenced by the acidity of the CCA chemical added to the wood. Six lysimeters (two that simulate wood monofills, two that simulate C&D debris landfills, and two that simulate MSW landfills) were operated for a period of 18 months. Each set of two lysimeters were identical except that the wood component in one was untreated and the other was CCA-treated. Results showed that the quantities of arsenic leached from the CCA set of lysimeters was significantly higher than the quantities leached from the lysimeters containing solely untreated wood. The organic arsenic species, DMAA, predominated the speciation of arsenic from the untreated control lysimeters. Either As(V) or As(III) predominated the speciation of the lysimeters containing CCA-treated wood. Groundwater samples were collected in the vicinity of 21 unlined C&D landfills in an effort to determine whether or not arsenic is elevated at these landfills beyond background concentrations. The presumption was that CCA-treated wood has been disposed at these landfills and that the arsenic from the CCA-treated wood may be starting to impact groundwater at the monitoring wells located at the site. Of the 48 samples collected from compliance/detection wells, 21 were found to contain total arsenic concentrations greater than the 5 μg/L detection limit. Of these samples, 6 were characterized by concentrations greater than 20 ug/L. These 6 samples came from 3 separate landfills. Of interest is that the organic arsenic species (DMAA and MMAA) were the predominant arsenic species from the one landfill with elevated background concentrations. The predominant arsenic species in the other two landfills were As(III) and As(V). This difference in speciation was interesting and suggests perhaps a difference in source. Overall results of this study suggest that arsenic leaches from CCA-treated wood primarily as either As(V) or As(III). Chromium predominantly leaches as Cr(III). If the wood is burned, arsenic speciation of the leachates remains consistent with that of the unburned wood with As(V) and As(III) predominating, but chromium speciation of the leachates converts almost exclusively to Cr(VI). The degree of Cr(VI) leaching from ash is highly dependent upon the pH of the ash leachate, with higher leachate concentrations for samples with lower retention levels. Results of this study also showed that more As(III) leaches from weathered wood than from unweathered wood. The conversion of arsenic towards As(III) as it weathers may enhance the leaching of arsenic as wood structures increase in age. Furthermore, results also suggest that arsenic that leaches from untreated wood is primarily in the less toxic organic form (DMAA), whereas arsenic that leaches from CCA-treated wood is in the more toxic As(V) and As(III) forms. This difference in speciation is important when evaluating the relative impacts of arsenic.

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