ROLE OF SOOT CARBON AND OTHER CARBON MATRICES IN THE DISTRIBUTION OF PAHS AMONG PARTICLES, DOC, AND THE DISSOLVED PHASE IN THE EFFLUENT ANDRECIPIENT WATERS OF AN ALUMINUM REDUCTION PLANT

The speciation of polycyclic aromatic hydrocarbons (PAHs) in natural w aters affects both the chemical fate and the bioavailability of these compounds. PAHs may be dissolved or sorbed to particles or dissolved o rganic carbon (DOC). Furthermore, soot carbon has recently been shown to control the sorption of PAHs onto particles in natural waters. The present study investigated the distribution of individual PAHs among t hese three phases by examining the effluent and recipient waters of a Soderberg aluminum plant and evaluating the importance of soot carbon partitioning. The results showed that soot carbon may control partitio ning between the dissolved and particulate phases and that the partiti on coefficients were orders of magnitude higher than would be expected on the basis of organic carbon-water partitioning alone. The carbon-n ormalized partition coefficient for the distribution of individual PAH s between DOC and the dissolved phase (K-DOC) exhibited no more than a weak correlation with hydrophobicity (K-ow) as compared with what was found for the partition coefficients for particles. This indicates th at there are different sorption mechanisms at work with DOC than with particulate organic carbon and soot. In the recipient water, up to 90% of the total concentration of individual PAHs was accounted far by a nonfilterable DOC-associated phase, which was not retained by the poly urethane foam (PUF) adsorbent.