DOI: http://dx.doi.org/10.1065/ehs2001.06.008.3 ---
Present knowledge assumes that different mechanisms acting downstream in high tem perature processes lead to the for mation of polychlorinated di benzo(p) diox ins (PCDDs) and polychlorinated dibenzofu rans (PCDFs). Concerning the seventeen 2, 3, 7, 8-Cl-sub stituted PCDD/F congeners in particular, there is new evidence for a single-step re action type (re cently reported in this publica tion se ries, cf. also parts 1 and 2). A formation based on a combination of the several mechanisms, which have been proposed and discussed since 1985, becomes more and more unlikely.
Qualitatively, the PCDD/F formation down stream from high temperature processes depends instead on a thermodynamically forced single reaction step and quantitatively, on pure sta tistical distribution. This may be a new Ther moStat instead of de novo synthesis. |
