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ADSORPTION OF POLYCYCLIC AROMATIC HYDROCARBONS IN AGED HARBOR SEDIMENTS
Citation:
Khodadoust, A. P., L. Lei, J. E. Antia, R. Bagchi, M. T. Suidan, AND H H. Tabak. ADSORPTION OF POLYCYCLIC AROMATIC HYDROCARBONS IN AGED HARBOR SEDIMENTS. M.K. Banks (ed.), JOURNAL OF ENVIRONMENTAL ENGINEERING. American Society of Civil Engineers (ASCE), Reston, VA, 131(3):403-409, (2005).
Description:
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 significant hysteresis in desorption from sediment, due to strong retention by the aged sediment organic carbon. Sediment organic carbon-water partition coefficients (log Koc) 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). There is considerable interest in the bioremediation of environments contaminated with PAHs. Successful bioremediation of sediment-bound PAHs is believed to involve two factors: (i) Estimation of reversibly sorbed fraction of PAHs in sediments, which would be available for biological transformation by microorganisms. (ii) Methods for delivery of nutrients and/or oxygen to the microorganisms that possess catabolic enzymes needed to degrade PAHs. The overall objectives of the present research effort are to develop systematic remediation protocols for application to sediments contaminated with PAHs. In particular, these protocols would quantify natural recovery rates, contaminant bioavailability, natural and enhanced in-situ biodegradation rates, and attainable endpoints. As a first step in the treatment of sediments contaminated with PAHs, it is necessary to quantify the amounts of contaminants that are adsorbed and desorbed (available for biodegradation) by sediments under abiotic equilibrium conditions with the surrounding aqueous phase. Data from these adsorption/desorption isotherms are also useful in determining diffusion and mass transfer coefficients, as well as calculating PAH adsorption/desorption rates in sediments. In turn, these mass transfer parameters are necessary in developing strategies for treating PAH contaminated sediments. The bioavailability of individual PAHs is presented in fundamental studies characterizing the extent of adsorption and desorption from uncontaminated sediments.