Exploratory analysis of the effects of particulate characteristics on the variation in partitioning of nonpolar organic contaminants to marine sediments.

The partitioning of nonpolar organic contaminants to marine sediments is considered to be controlled by the amount of organic carbon present. However, several studies propose that other characteristics of sediments may affect the partitioning of contaminants. For this exploratory analysis, we measured 19 sediment characteristics from five marine sediments and 11 characteristics of humic acids extracted from the sediments. These characteristics included elemental composition, grain size, soot carbon, polarity indices and molar ratios. Each individual characteristic and combinations of these characteristics were then used to normalize partition coefficients (Kp) generated for three organic contaminants: lindane, fluoranthene and a tetrachlorinated biphenyl (PCB). A coefficient of variation (CV) was then calculated for each contaminant to determine which normalization characteristic (individually or in combination) resulted in the lowest variability in partitioning between study sediments. For lindane and the PCB. normalization by the amount of sediment organic carbon resulted in the lowest variability in partition coefficients with CVs of 16.2% and 37.7%. respectively. However, normalization of fluoranthene by silt content resulted in lower CVs than those generated by organic carbon normalization: 31.0% vs. 37.6%. Normalization of contaminants Kp's by combined values of sediment characteristics resulted in lower CVs but only by a few percent. Using humic acid characteristics, humic organic carbon reduced variability between sediments most effectively. But only the normalized fluoranthene values had a CV (i.e., 25.4%) lower than the one based on normalization by sediment characteristics. When combined, humic acid characteristics resulted in lower CVs than normalization by individual or combinations of sediment characteristics for fluoranthene and the PCB with CVs of 19.3% and 28.7%, respectively. This analysis indicates variability associated with the partitioning of some organic contaminants to marine sediments can be further reduced when normalization by sediment characteristics other than organic carbon are utilized.