Citation:

Tabak*, H H., J. M. Lazorchack, L. Lei, A. P. Khodadoust, J. E. Antia, R. Bagchi, AND M. T. Suidan. STUDIES ON BIOREMEDIATION OF POLYCYCLIC AROMATIC HYDROCARBON-CONTAMINATED SEDIMENTS: BIOAVAILABILITY, BIODEGRADABILITY, AND TOXICITY ISSUES. C.H. Ward (ed.), ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY. SETAC Press, Pensacola, FL, 22(3):473-482, (2003).

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The widespread contamination of aquatic sediments by polycyclic aromatic hydrocarbons (PAHs) has created a need for cost-effective bioremediation processes, on which the bioavailability and the toxicity of PAHs often have a significant impact. This research investigated the biodegradation of PAHs in a chronically PAH-contaminated estuarine sediment, East River (ER) sediment, characterized by high concentrations of PAHs, sulfide, and metals. New York/New Jersey Harbor (NY/NJH) marine sediment with trace quantities of PAHs was also used in the research as a PAH containing matrix. The focus was to examine the relationship between bioavailability of PAHs and their biological removal, as well as the toxicity issue of sediments. Fresh water and marine sediment toxicity tests were used to measure baseline toxicity of samples collected from (NY/NJH) and ER sediments to amphipods, aquatic worms, fathead and toxicity test was developed and used in parallel with standard tests. Five sediment manipulation procedures, namely: (1) sediment purge; (2) sediment dilution; (3) sediment aeration; (4) Ambersorb (563 and 572) treatments (for PAH removal); and (5) Amberlite (IRC-718) (for metal removal) procedures were used to determine the cause of toxicity in the sediments. Results showed that freshwater amphipod survival was improved with sediment aeration and dilution procedure combined with 8% Ambersorb 563 and 572 and Amberlite (IRC-718) treatments. Toxicity studies revealed that ER sediment was acutely toxic to all freshwater and marine organisms tested, and toxicity to the ecosystem was mainly caused by sulfide, PAHs, and metals present in the sediment. In spite of the high toxicity, aerobic experiments on sediment/water slurry systems showed that most of the PAH compounds can be significantly degraded, if the initial high oxygen demand hurdle due to the high sulfide content of the sediment was overcome. The bioavailability of individual PAH compounds was assessed by two methods: examining the extent of desorbability of model PAH compounds after establishing adsorption equilibrium in freshly spiked NY/NJH sediment, or studying the desorption of all PAHs from ER sediment in 90% isopropanol solution in water. It was found that the removal of PAHs by biodegradation was closely related to the desorbability of PAHs in the solution of 90% isopropanol in water. Desorption from freshly spiked NY/NJH sediment did not describe the bioavailability of PAHs in aged contaminated sediments well. This research improves our understanding of the factors that control in-situ bioremediation of PAH contamination, and suggests that aerobic biodegradation has the potential for both PAH removal and ecotoxicity reduction of the PAH-contaminated sediments.

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