The role of sediment composition on the bioavailability of laboratory-dosed sediment-associated organic contaminants to the amphipod, Diporeia (spp.)

Bioavailability of sediment-associated contaminants depends on contaminant and sediment characteristics and organism behavior and physiology. Bioavailability of a sediment-associated contaminant can be defined by the uptake clearance. Uptake clearance is the volume or mass of the source compartment scavenged of contaminant per mass of organism per time. For non-polar organic contaminants, carbon normalization has been suggested as a means of normalizing the relative bioavailability among sediments of differing compositions. To examine this, amphipods, Diporeia spp., were exposed to five Lake Michigan sediments and one soil from Florissant, MO, each spiked with selected polycyclic aromatic hydrocarbon (PAH) and polychlorinated biphenyl (PCB) congeners. The uptake clearances (ks) were then determined. The PAH congeners were generally less bioavailable, based on ks, than the PCB congeners after accounting for contaminant hydrophobicity. The ks values generally declined as the fraction of fine particles (<63 μm) and organic carbon increased among the sediments. Organic carbon normalization reduced the variability among the ks values to approximately a factor of two among the Lake Michigan sediments, but the Florissant soil was an outlier. The compounds were more bioavailable from the Florissant soil than from the Lake Michigan sediments, and the relative availability increased with increasing contaminant hydrophobicity up to a factor of eight for hexachlorobiphenyl.