Polychlorinated Compounds chlorinated dioxins

Stalling, D.L., L.M. Smith, J.D. Petty, J.W. Hogan, J.L. Johnson, C. Rappe, and H.R. Buser. 1983. Residues of polychlorinated dibenzo-p-dioxins and dibenzofurans in Laurentian Great Lakes fish. Pages 221-240 in R.E. Tucker, A.L. Young, and A.P. Gray (eds.). Human and Environmental Risks of Chlorinated Dioxins and Related Compounds. Plenum Press, New York. 

Dual-phase extraction cannot remediate heavy chlorinated compounds, pesticides, or heavy hydrocarbons including polychlorinated biphenyls (RGBs), dioxin, fuel oil No. 6, or metals (with the possible exception of mercury). High-velocity pump systems (such as liquid ring vacuum pumps) tend to form emulsions, especially when diesel fuel is part of the recovered fluids. The problem of emulsion can be solved with prepump separation or a de-emulsification unit. 

Polychlorinated Dibenzo-(p)-Dioxins and Dibenzo-Furans. Another group of compounds that we need to specifically address are the polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzo-furans (PCDFs) (Fig. 2.15). The PCDDs and PCDFs are not intentionally produced but are released into the environment from various combustion processes and as a result of their occurrence as unwanted byproducts in various chlorinated chemical formulations (e.g., chlorinated phenols, chlorinated phenoxy herbicides see Alcock and Jones, 1996). Because some of the PCDD and PCDF congeners are very toxic (e.g., 2,3,7,8-tetrachloro dibenzo-p-dioxin, see margin), there have been and still are considerable efforts to assess their sources, distribution, and fate in the environment. Similarly to the PCBs or DDT (see above), the PCDDs and PCDFs are highly hydrophobic and very persistent in the environment. It is therefore not surprising that they have also been detected everywhere on earth (Brzuzy and Hites, 1996 Lohmann and Jones, 1998 Vallack et al., 1998). Finally, we should note that polybrominated diphenylethers (PBDEs, see margin) that, like the PBBs (see above), are used as flame retardants, are of increasing environmental concern (de Boer et al., 2000). 

CDDs are a family of 75 different compounds commonly referred to as polychlorinated dioxins. These compounds have varying harmful effects. The CDD family is divided into eight groups of chemicals based on the number of chlorine atoms in the compound. The group with one chlorine atom is called the mono-chlorinated dioxin(s). The groups with two through eight chlorine atoms are called di-chlorinated dioxin (DCDD), tri-chlorinated dioxin (TrCDD), tetra-chlorinated dioxin (TCDD), penta-chlorinated dioxin (PeCDD), hexa-chlorinated dioxin (HxCDD), hepta-chlorinated dioxin (HpCDD), and octa-chlorinated dioxin (OCDD). The chlorine atoms can be attached to the... 

Stalling DL, Smith LM, Petty JD, et al. 1983. Residues of polychlorinated dibenzo-p-dioxins and dibenzofurans in Laurentar Great Lakes fish. In Tucker E, Young AL, Gray AP, eds. Human and environmental risks of chlorinated dioxins and related compounds. New York, London Plenum Publishing Corp, 221-240. 

Blumenstock, M. Zimmermann, R. Schraumm, L. W. Kaune, A. Henkelmann, B. Kettrup. A. Presence of polychlorinated dibenzo-p-dioxins (PCCD), dibenzofurans (PCDFs), biphenyls (PCB), chlorinated benzenes (PCBz) and polycyclic aromatic hydrocarbons (PAH) under various combustion conditions in a post combustion chamber, Organohalogen Compounds, 1998, 36, 59-63. 

In this volume of Issues we address the sources, environmental cycles, uptake, consequences and control of many of the more important chlorinated organic micropollutants. Under this heading we have included a range of semi-volatile persistent compounds, notably polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) as well as a number of chlorinated pesticides. We have not sought to include volatile species such as CFCs which cause environmental problems of an entirely different nature. The compounds included in this volume cause no threat to the stratospheric ozone layer, but have given widespread cause for concern in relation to their environmental persistence and high toxicity, and their potential for adverse effects on humans and wildlife. 

Hagenmaier H, Brunner H, Haag R, Kraft M (1987b), Environ. Sci. Technol. 21 1085-1088. Copper-catalyzed dechlorination/hydrogenation of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and chlorinated aromatic compounds"... 

Gotz R, Friesel P, Paepke O, Ball M, Lis A (1993), Chemosphere 27 105-112.. .Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) and other chlorinated compounds in the river Elbe results on bottom sediments and fresh sediments collected in sediment chambers"... 

As shown in Fig. 6, some of the reduction reactions, including intermediate steps, for the destruction of a variety of contaminants using the gas-phase chemical reduction process. The process primarily involves the gas-phase reduction of organic compounds by hydrogen at temperatures of 850°C or higher. Chlorinated hydrocarbons, such as PCBs and polychlorinated dibenzo-p-dioxins (dioxins), are chemically reduced to methane and... 

The formation during combustion of a range of chlorinated aromatic compounds including polychlorinated benzenes, styrenes, and naphthalenes (Yasahura and Morita 1988) and chlorobenzoic acids (Mowrer and Nordin 1987). The formation of chlorinated dioxins and 4,4 -diphenoqui nones is noted further in Chapter 3, Section 3.6.3. 

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