Zusammenfassung
Das Umweltverhalten von persistenten organischen Schadstoffen hängt wesentlich von ihrer Verteilung zwischen Luft, Wasser und natürlichen organischen Phasen ab. Angesichts der großen Anzahl von Schadstoffen einerseits und der großen Variabilität natürlicher organischer Phasen andererseits ist eine experimentelle Bestimmung aller relevanter Verteilungskonstanten ausgeschlossen. In der Umweltchemie ist es daher seit langem üblich, die Verteilungskonstanten zwischen Luft oder Wasser und einer organischen Phase mit den entsprechenden Oktanol/Luft oder Oktanol/Wasser-Verteilungskonstanten der Substanzen zu korrelieren. Eine Abschätzung unbekannter Verteilungskonstanten mit Hilfe solcher Beziehungen kann aber zu erheblichen Fehlern führen. Die Gründe dafür sind: a) Fehler in den Kow oder Koa Daten; b) die Substanz gehört nicht zu der Substanzklasse, für die die Kow-Beziehung erstellt wurde; c) die organische Phase unterscheidet sich von derjenigen, für die die Kow-Beziehung erstellt wurde. Obwohl diese Fehler zum Teil sehr groß werden können, werden sie häufig in Kauf genommen, da keine Alternativen bekannt sind. Hier soll ein Ansatz zur Vorhersage von Verteilungskonstanten beschrieben werden, der es erlaubt solche Fehler deutlich zu minimieren. Dieser Ansatz beschreibt die van-der-Waals Wechselwirkungen und H-Brücken Bindungen zwischen der Substanz und den Phasen durch getrennte Terme. Eine Reihe von Beispielen zeigen die beiden Ansätze im Vergleich.
Abstract
Equilibrium partition constants are required for assessing the transport and exposure of POPs in the environment. Due to the high number of compounds in daily use and the high number of different natural phases it is not conceivable to measure all partition constants of interest. In environmental chemistry the partitioning of POPs between water or air and natural organic phases is usually correlated to their respective partitioning into octanol (i.e. log Kow or log Koa). However, the predictive power of such one-parameter Linear Free Energy Relationships (LFER) is quite limited because no single descriptor is able to describe appropriately all the molecular interactions that determine the equilibrium partitioning of a given compound between two phases. Therefore, different compound classes usually require different log Kow or log Koa relationships. Furthermore, the heterogeneity of natural organic phases (e.g., different types of soil organic matter) is not reflected in correlations with log Kow. Poly-parameter LFER’s, which describe the intermolecular interactions relevant for the partitioning process, are a promising alternative. It can be demonstrated by a variety of applications that such poly-parameter LFERs are very useful tools to describe the partitioning of large sets of very diverse compounds with a single equation. Furthermore, in contrast to simple log Kow relationships, these equations can be used to characterize the sorbent properties of a given complex sorbent. Interestingly, to date, only few applications of poly-parameter LFERs have been published in the field of environmental chemistry.
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OnlineFirst: 17. Januar 2003
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Goss, K.U. Der Oktanol/Wasser Verteilungskoeffizient — Das Allheilmittel der Umweltchemie?. UWSF - Z Umweltchem Ökotox 15, 273–279 (2003). https://doi.org/10.1065/uwsf2003.01.050
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DOI: https://doi.org/10.1065/uwsf2003.01.050
Schlagwörter
- Koa (Oktanol/Luft-Verteilungskonstante
- Kow (Oktanol/Wasser-Verteilungskonstante)
- LFERs (Linear Free Energy Relationships
- persistente organische Schadstoffe (POPs)
- Verteilung
- Sorption