Adsorption of polycyclic aromatic hydrocarbons in aged harbor sediments

Polycyclic aromatic hydrocarbons (PAHs) are a group of hydrophobic organic contaminants which have low aqueous solubilities and are common pollutants in harbor sediments. Adsorption and desorption isotherms for PAHs are conducted to study the abiotic sorption of PAHs in uncontaminated harbor sediments in contact with the natural overlaying water. Representative 2-, 3-, and 4-ring PAHs are used to obtain PAH adsorption/desorption data. Linear adsorption onto sediment is obtained for the following PAHs: Naphthalene and 2-methyl naphthalene (2 ring), acenaphthene, anthracene, and phenanthrene (3 ring), and fluoranthene and pyrene (4 ring). Linear adsorption is followed by a significant hysteresis in desorption from sediment, due to strong retention by the aged sediment organic carbon. Sediment organic carbon-water partition coefficients (log K-oc) for the seven PAHs range from 2.49 to 4.63. Based on the sorption data for these representative PAHs, sediment organic carbon-water partition coefficients may be predicted for other PAH compounds, particularly the less soluble and the more hydrophobic PAHs (5 or more rings).