Environ. Sci. Technol. 2003, 37, 1563-1567
Formation of PCDDs, PCDFs, and Coplanar PCBs from Incineration of Various Woods in the Presence of Chlorides AKIO YASUHARA National Institute for Environmental Studies, 16-2, Onogawa, Tukuba, Ibaraki 305-8506, Japan TAKEO KATAMI Gifu Prefectural Institute of Health and Environmental Sciences, 1-1 Fudogaoka, Naka, Kagamigahara, Gifu 504-0838, Japan TAKAYUKI SHIBAMOTO* Department of Environmental Toxicology, University of California, Davis, California 95616
Exhaust gases from the combustion of woods (Japanese red pine, Japanese cedar, Siebold’s beech, seawaterimpregnated Japanese red pine and Japanese cedar, waste woods containing chlordane, and waste woods containing pentachlorophenol) were collected at the outlet of a combustion chamber. A small-scale incinerator with a stationary grate was used. The samples were analyzed for PCDDs, PCDFs, and coplanar PCBs by gas chromatography/ mass spectrometry (GC/MS). When the grate temperature of the combustion chamber was lower than 700 °C, the total amount of PCDDs, PCDFs, and coplanar PCBs formed was proportional to the chlorine content of the combustion samples. On the other hand, when the grate temperature of the combustion chamber was higher than 800 °C, there was only a slight formation of PCDDs, PCDFs, and coplanar PCBs regardless of the chlorine content of the combustion samples. When the grate temperature was low, nearly 90% of total PCDDs, PCDFs, and coplanar PCBs formed were PCDFs, whereas when the grate temperature was higher, 50-80% of total PCDDs, PCDFs, and coplanar PCBs formed was PCDFs. The total amount of PCDDs, PCDFs, and coplanar PCBs formed in a high-temperature condition was approximately 1/50 of that formed in a lowtemperature condition. Coplanar PCBs tended to form less than PCDDs or PCDFs did. Mono-ortho-PCBs were formed several times more than nonortho-PCBs. PCDDs or PCDFs contributed significantly to the values of TEQ, while coplanar PCBs contributed only slightly.
Introduction There have been many reports on formation of dioxins (PCDDs) and dioxin-like compounds (PCDFs and coplanar PCBs) during combustion of woods in various systems, including a fireplace in a house (1), a wood-chips boiler (25), an incinerator (6-8), and a fire (9). However, formation * Corresponding author phone: +81 (422) 33-3118; fax: +81 (422) 32-0393; e-mail:
[email protected]. 10.1021/es020948o CCC: $25.00 Published on Web 03/11/2003
2003 American Chemical Society
dioxins and dioxin-like compounds influenced by combustion conditions, such as chloride content of combustion materials and temperature of the combustion chamber, remained relatively unknown because of wide variations among combustion apparatuses and devices for exhaust gas treatment. A variety of woodssincluding logs with bark, wood chips, and barksshave been combusted in both public and private incinerators. Therefore, there are many reports on formation dioxins and dioxin-like compounds from various woods upon combustion. For example, some logs are contaminated with chloride from seawater. Therefore, it is known that barks from such logs produce dioxins and dioxinlike compounds upon combustion (4, 5). Also, dioxins and dioxin-like compounds formation upon combustion has been reported in the waste logs impregnated with a preservative (8). It is important to determine how dioxins and dioxin-like compounds form from various woods in the presence of chloride in high-temperature processes in order to reduce their role in environmental contamination. Therefore, exhaust gas was collected at the outlet located at a combustion chamber of a small-scale incinerator in which natural logs with bark, woods impregnated in seawater, and waste woods impregnated with chlorine containing preservatives or insecticides were combusted under various temperatures. Samples collected were analyzed for polychlorinated dibenzop-dioxin (PCDDs), Cl1-Cl8-PCDDs, Cl1-Cl8-PCDFs (polychlorinated dibenzofuran (PCDFs), and coplanar polychlorinated biphenyls (coplanar PCBs) by gas chromatography/ mass spectrometry (GC/MS) in order to investigate the factors influencing formation of PCDDs, PCDFs, and coplanar PCBs
Experimental Section Chemicals. Isotope-labeled PCDDs, PCDFs, and coplanar PCBs (nonortho-PCBs and mono-PCBs) for internal standards (100 ng/mL n-nonane) were purchased from Cambridge Isotope Laboratories, Inc. (Andover, MA). For the solution of the sampling-spike recovery test, a 1 mL n-nonane solution containing 0.0005 ng/µL each of 13C12-1,2,3,4-T4CDD, 1,2,3,4,7,8-H6CDF, and 1,2,3,4,7,8,9-H7CDF solution was prepared. For the solution of the cleanup-spike recovery test, a 100 µL n-nonane solution containing 0.005 ng/µL each of 13C -2,7-D CDD, 2,3,7-T CDD, 2,3,7,8-T CDD, 1,2,3,7,8-P 12 2 3 4 5 CDD, 1,2,3,6,7,8-H6CDD, 1,2,3,4,6,7,8-H7CDD, 1,2,3,4,6,7,8,9O8CDD, 13C12-2,3,7,8-T4CDF, 1,2,3,7,8-P5CDF, 1,2,3,4,7,8H6CDF, 1,2,3,4,6,7,8-H7CDF, 1,2,3,4,6,7,8,9-O8CDF, 13C123,3′,4,4′-T4CB, 3,4,4′,5-T4CB, 3,3′,4,4′,5-P5CB, 2′,3,4,4′,5-P5CB, 3,3′,4,4′,5,5′-H6CB, 2,3′,4,4′,5,5′-H6CB, 2,3′,4,4′,5,5′-H6CB, and 2,3,3′,4,4′,5,5′-H7CB was prepared. For the solution of the internal standards, a 2 µL n-nonane solution containing 0.25 ng/µL each of 13C-121,3,6,8-T4CDD and 1,2,3,7,8,9-H6CDD was prepared. n-Nonane was bought from Kanto Chemical Co., Inc. (Tokyo, Japan). Instruments. The chloride content in the samples was measured by a TOX-100 Total Organic Halogen Analyzer (Dia Instruments Co., Ltd., Chigasaki, Japan). Combustion chamber and flame temperatures were measured by a LK-1200 thermo-couple conductor interfaced to a CT-1310 digital thermometer (Custom Co., Ltd., Tokyo, Japan). Pretreatment for water removal from exhaust gas was conducted by PS-200SCR (Horiba, Ltd., Kyoto, Japan). Continuous measurement of carbon monoxide, carbon dioxide, and oxygen in samples was performed by a Horiba PG-230 Gas Analyzer (Horiba, Ltd., Kyoto, Japan). Hydrogen chloride concentration in exhaust gas was measured by a VOL. 37, NO. 8, 2003 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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TABLE 1. Conditions of Samples Combusted sample number
wood
amount (kg)
chlorine content (%)
combustion time
combustion rate (kg/h)
sample I sample II sample III sample IV sample V sample VI sample VII sample VIII sample IX
pine cedar seawater-impregnated pine seawater-impregnated cedar bark searwater-impregnated cedar without bark pine beech chlordane-impregnated waste woods pentachlorophenol-impregnated waste woods
4.725 4.502 1.999 2.356 2.696 6.482 4.578 4.025 4.043
