title: Behavior of PCDDs/PCDFs in remediation of PCBs-contaminated sediments by thermal desorption.
abstract: Thermal desorption is an effective method for removing volatile and semivolatile organic matter in contaminated solid remediation. Formation of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in many polychlorinated biphenyls (PCBs) destruction processes has been reported, but the removal pathways are poorly understood. We therefore investigated the behaviors of PCBs and PCDDs/PCDFs in thermal desorption of PCBs-contaminated sediment and predicted the reaction pathways. Four thermal desorption experiments using PCB-contaminated sediments containing different doses of PCBs were carried out. In all the experiments, decomposition of 48-70% of PCBs was achieved, resulting in formation of PCDFs. Despite the PCBs decomposition levels, toxic equivalencies (TEQs) in the treated and volatilized samples were 2.8-6.3 times and 8.0-10.5 times as high as the TEQs in the initial samples, respectively, indicating increased toxicity after treatment. Further analysis revealed that PCDFs with higher numbers of chlorine atoms are likely to remain in the sediments than those of volatilized PCDFs; this is supported by the positive correlation between the vapor pressures of PCDFs and the ratios of volatilized PCDFs.
authors.affiliation: Water & Environmental Process Engineering Department, Water & Environmental Engineering Center, Social Infrastructure Systems Company, Toshiba Corporation, 1-1-1 Shibaura, Minato-ku, Tokyo, Japan. takeshi18.sato@toshiba.co.jp
authors.forename: Takeshi
authors.initials: T
authors.lastname: Sato
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Todoroki
authors.forename: Kimiaki
authors.initials: K
authors.lastname: Shimoda
authors.forename: Akihiko
authors.initials: A
authors.lastname: Terada
authors.forename: Masaaki
authors.initials: M
authors.lastname: Hosomi
mesh_terms: D001572:Benzofurans / Q000032:analysis / Q000737:chemistry* / Q000633:toxicity; D000072338:Dibenzofurans, Polychlorinated; D052918:Environmental Restoration and Remediation; D019015:Geologic Sediments / Q000737:chemistry*; D006361:Heating; D007700:Kinetics; D011078:Polychlorinated Biphenyls / Q000032:analysis / Q000737:chemistry*; D000072317:Polychlorinated Dibenzodioxins / Q000031:analogs & derivatives* / Q000032:analysis / Q000737:chemistry / Q000633:toxicity; D012989:Soil Pollutants / Q000032:analysis / Q000737:chemistry* / Q000633:toxicity
chemical_list: D001572:Benzofurans; D000072338:Dibenzofurans, Polychlorinated; D000072317:Polychlorinated Dibenzodioxins; D012989:Soil Pollutants; D011078:Polychlorinated Biphenyls