Technical report 123

Conclusion

Although various purportedly reliable methods exist for calculating soil sorption properties of chemicals, these methods usually relate KOW directly to KOC. Whilst the resulting estimates may be acceptable for many simple, non-ionisable organic compounds, in the case of pesticides many alternative soil sorption mechanisms exist. These can be significant or even dominant over the established concept of hydrophobic interactions/binding. Indeed, incidents of .atypical¡± soil behaviour of pesticides are in fact relatively common. Since soil adsorption is simple and relatively inexpensive to determine experimentally, measurement of this important environmental property is preferred. Estimation is less suitable, unless (for a given chemistry series) it has already been demonstrated that hydrophobic-driven soil sorption is dominant.

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