Effects of different forms of organic carbon on the partitioning and bioavailability of nonylphenol.

Oxygenated nonpolar organic contaminants (NOCs) are underrepresented in studies of the partitioning and bioavailability of NOCs, including nonylphenol. In this investigation, we evaluated the toxicity, partitioning, and bioavailability of nonylphenol as affected by different forms of organic carbon. Along with organic carbon content, the role of organic carbon polarity was assessed. Toxicity of nonylphenol to a mysid and amphipod was comparable to results reported in the literature for marine organisms with median lethal concentrations (LC50s) of 82.3 and 236 microg/L, respectively. The presence of the different forms of organic carbon in every instance altered, often statistically significantly, the toxicity and bioavailability of the nonylphenol and increased the LC50 by approximately a factor of two. Partition coefficients (KPs) for nonylphenol ranged from 21.3 for cellulose to 9,770 for humic acid; log organic carbon-normalized partition coefficients (KOCs) ranged from 1.71 for cellulose to 4.71 for sediment. An exercise to predict nonylphenol effects using our toxicity data and normalized partition coefficients indicated organic carbon content was most protective and also highlighted the need for further research to better understand nonylphenol bioavailability. These data suggested that with regard to partitioning and bioavailability, the oxygenated NOC nonylphenol behaves like conventional NOCs. The data also suggest that, with refinements, polarity may have some advantages in predicting nonylphenol bioavailability.