Reversible and irreversible adsorption of naphthalene and α-naphthol to soil

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Virginia Tech


Experiments were performed with naphthalene and a-naphthol to compare the processes involved in the sorption of a polycyclic aromatic hydrocarbon (PAH) and its metabolite, respectively, and to assess the bioavailability of these two compounds adsorbed to two sandy soils with different organic carbon contents. Adsorption conditions were varied to estimate the extent that biologically-mediated and chemically-induced oxidative coupling, and rate-limited diffusive processes contributed to the apparent irreversible adsorption of these compounds. The purposes of this research were to: (1) investigate the processes which cause the irreversible adsorption of organic contaminants to soil~ (2) gauge the impact that these different adsorption processes have on the bioavailability of sorbed contaminants; and, (3) evaluate the environmental significance of these processes in soils and the subsurface. This dissertation has been prepared as three separate articles for publication in peer reviewed journals. The first article serves as a literature review in evaluating the significance of oxidative coupling reactions in soil and subsurface environments. This review concludes that oxidative coupling of organic contaminants may be important in soils and could be stimulated as a viable remediation strategy. For subsurface systems oxidative coupling appears much more limited, however, engineered systems could be developed to enhance this process. The second article presents experimental results used to quantify the individual processes involved in the irreversible adsorption of naphthalene and a-naphthol. This article concludes that both biological and chemical catalysts are important in promoting irreversible adsorption reactions, and that once the partial oxidation of a PAH occurs, oxidative coupling can become a significant process affecting contaminant fate. The third and final article examines the effect of different adsorption processes on the subsequent bioavailability of sorbed naphthalene and anaphthol, and concludes that the biodegradation of naphthalene and α-naphthol adsorbed to both the soils tested was controlled by the rate of desorption and the reversibility of the adsorption process.



bioavailability, oxidative coupling