Nonspecific Chlorination of Organics: a Chemistry Unique to Human Industry? (Putting Kraft Mill AOX Emissions into Perspective)

Abstract

To counter the claim that all biotreated organochlorine (AOX) emissions from modern kraft mills are unnatural and inherently hazardous, it has been argued that over 2400 different AOX compounds are now known to be produced by living organisms. This is an invalid rationale. These 2400 natural compounds are mostly specific halometabolites — each is produced as a large number of identical molecules by a specific enzyme-mediated mechanism. In contrast, in a kraft mill bleachery, heterogeneous wood derivatives are non-specifically chlorinated by hypochlorous acid (HOCl) or hypochlorite ion (OCl-) to produce mixtures containing hundreds of different AOX species. It is therefore much more reasonable to compare mill-derived AOX to other human and natural sources of OCl-/HOCl-generated non-specific AOX. Chloroperoxidase (CPO)-type enzymes naturally produce HOCl and OCl-from common chloride ions and hydrogen peroxide (H2O2). They have now been demonstrated in bacteria, fungi, algae, lichens, higher plants and animals. We demonstrate that a common fungal CPO can, when applied to soil extracts, lignins, cellulosics, tannins and natural lake water organics, rapidly generate nonspecific AOX. In agreement with earlier work done in other geographic areas, AOX was found in all of a wide range of samples from the Montreal region, both from urban and relatively remote pristine lakes and woodlands. Much of it is almost certainly produced via nonspecific HOCl/OCl- chlorination. Finally, we demonstrate that nonspecific AOX is produced by a CPO in mammalian blood as the natural result of the body's immune system fighting infections. Thus, HOCl/OCl- based production of AOX from mixtures of organic molecules is seen to be a common occurrence in nature as well as a product of human technology.

Descoloração e degradação de poluentes orgânicos em soluções aquosas através do processo fotoeletroquímico

“…Pequenas diferenças na estrutura de um composto poluente ou na composição do meio também podem atrapalhar o funcionamento de um sistema biológico estabelecido. Devido a esse conjunto de fatores, um consórcio de microorganismos pode não mais reconhecer certas substâncias e não degradá-las, ou transformá-las em produtos mais tóxicos 3 .…”

Characterization of AOX by Fractionation Analysis and Size-exclusion Chromatography

“…Chlorinated organic compounds have been determined in the environment for more than three decades. There have been significant efforts to identify halogenated compounds built during the chlorination in drinking water treatment [15], AOX substances in wastewaters from the paper and chemical industry [4,[12][13][14], biogenic generated AOX substances [2,5,7,16], AOX in swimming pool water [17], and in atmospheric deposition [18]. Both, individual compounds and group parameter are used in official regulations and environmental quality discussions.…”