Critical parameters that need to be considered in a bioavailability st
udy are reviewed and applied to a study on the sorption (binding) of p
henanthrene to dissolved humic acid (HA). Sorption coefficients values
(K-oc) of phenanthrene to HA were measured for HA from several source
s. These values were used to calculate the amount of HA that was neede
d to bind different fractions of solution-phase phenanthrene. Sorption
linearity and complete reversibility were assumed. A mixed culture of
phenanthrene degraders, dominated by Pseudomonas sp. was sensitive to
changes in dissolved phenanthrene concentrations in the range that wa
s used in this study. Therefore, it was expected that if bound phenant
hrene was not available, as is commonly stated in the literature, sorp
tion would affect mineralization rate by reducing the concentration of
free phenanthrene, However, it was found that mineralization of phena
nthrene was not affected by sorption even when 90% of the phenanthrene
was in the bound phase. It was concluded that the organisms were able
to use the phenanthrene directly from the bound phase and at the same
rate as from the free phase. Copyright (C) 1996 Elsevier Science B.V.