Hierarchic models, biodegradability

Harada H and Cote WA (1985) Structure of wood. In Higuchi T (ed). Biosynthesis and biodegradation of wood components. Academic Press, London, 1-42 Harrington 11 (2002) Hierarchical modelling of softwood hygro-elastic properties. Ph.D thesis. University of Canterbury, Christchurch, New Zealand Harris IF (1976) Acid hydrolysis and dehydration reactions for utilizing plant carbohydrates. In Timell TE (ed). Proceedings of 8th cellulose conference. Wiley, New York, Vol. 1 131-44... 

In combination with other validated QSARs (Table 4.10), hierarchic models are recommended for estimating the biodegradability of three major classes of environmental contaminants acyclic compounds, monocyclic carboaro-matic compounds and aliphatic cyclic compounds (Figures 4.8-4.10). 

Current generally applicable biodegradation models focus on the estimation of readily and nonreadily biodegradability in screening tests. This is because most experimental data are from such tests (e.g., MITI-I). There are far fewer data that are both quantitative and environmentally relevant (i.e., measured half-lives or rate constants). However, individual transformations and pathways are well documented in the literature. This allows for development of explicitly mechanistic models, making use of established group-contribution approaches, hierarchic rule-based expert systems, and probabilistic evaluation of possible transformation pathways. 

Figure 4.8 Flow chart of hierarchic QS AR models for predicting the biodegradability of acyclic compounds (Degner, 1991 lUCT, 1992 OECD, 1993b). Reproduced with permission from OECD.

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