Date Awarded

1995

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Virginia Institute of Marine Science

Advisor

Robert C. Hale

Committee Member

William G. MacIntyre

Abstract

Chloroguaiacols are common components of bleached kraft pulp mill effluent known to bioaccumulate in aquatic organisms, and sorb onto particulate material and sediments. Ionization properties of the chloroguaiacols must be known in order to explain their sorptive behavior in aquatic systems. to obtain this information, thermodynamic acid dissociation constants (p&K\sb{lcub}\rm a{rcub})& of guaiacol (o-methoxyphenol) and nine chloroguaiacols have been determined by spectrophotometric methods. These experimental p&K\sb{lcub}\rm a{rcub}& values have been compared with literature values, values predicted by the Hammett equation and predictions by quantum chemical calculations using MOPAC 6.0 with AM1 and MNDO Hamiltonian operators. Experimental and predicted acidities were linearly related, and the correlation and regression equations obtained have been used to calculate p&K\sb{lcub}\rm a{rcub}& values for those chloroguaiacols that were unavailable for experimental measurement. Sorption of chloroguaiacols onto sediments may result in reduced bioavailabilty to aquatic species, increased degradation rates or rapid burial. Conversely, it may result in increased exposure to deposit feeding species with subsequent transfer to higher trophic levels. The sorption of four chloroguaiacols (5-chloroguaiacol, 4,6-dichloroguaiacol, 4,5,6-trichloroguaiacol and tetrachloroguaiacol) with p&K\sb{lcub}\rm a{rcub}& values ranging from 9.06 to 6.06 was investigated on four estuarine sediments. The effect on sorption of aqueous phase pH, sediment organic carbon content and degree humification was investigated. Sorption coefficients, &K\sb{lcub}\rm d{rcub}&, were determined at two pH values (6.6 and 7.8). Linear relationships were observed between &K\sb{lcub}\rm d{rcub}& and both % total organic carbon(TOC) and % humic acids at each pH. &K\sb{lcub}\rm oc{rcub}& and &K\sb{lcub}humic{rcub},& sorption coefficients normalized to % TOC and % humic acids, were calculated. In addition to the amount of TOC present, the type of organic matter (ie. humic acids) is an important factor in sorption. Aqueous phase pH governs the ionization of chloroguaiacols. Sorption of the ionized and molecular species are different due, in part, to the different solubilities of the species and was reflected in the different &K\sb{lcub}\rm d{rcub}& values determined at each pH.

DOI

https://dx.doi.org/doi:10.25773/v5-j36d-ny47

Rights

© The Author

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