Date of Award
Doctor of Philosophy (PhD)
The impact of a multitude of toxic chemicals, or xenobiotics, on diverse aquatic environments and the need to consider such factors in adjacent land use and disposal situations has necessitated the development of usable analytical predictive approaches. A microbial and enzymatic assessment protocol for determining the environmental effect and fate of these manufactured chemicals in coastal wetlands was devised. The protocol combined in situ analyses of interrelated soil/sediment microenvironments with statistical and analytical laboratory microcosm approaches in presenting valid predictive models of xenobiotic fate and effect. The general objective of this combined field/laboratory analysis was to provide a better understanding of biotic and abiotic factors that influence toxic chemical breakdown over a range of salinity conditions. An overview of research in the area of microcosm development and design was first outlined followed by a technical description of two aquatic microcosm systems developed in this study. Variations in microbial diversity, enzyme activity, microbial ATP, and substrate uptake in ecologically-diverse, interrelated coastal soil/sediment microenvironments were examined to develop baseline protocols for combined in situ/microcosm fate and effect analyses. Strong correlative linkages were established between control microcosm and in situ measurements. Environmental impact was assessed using these correlative field approaches in a toxicant runoff incident in a freshwater swamp forest habitat. A testing protocol for examining microcosm features and operating parameters was also presented. Sequential and differential introduction of a toxicant into microcosm systems assessed the importance of pre-exposure and adaptation responses in environmental fate and effect estimates. Several industrial source phenols were used in a test case to evaluate overall microcosm performance. Relative biotransformation and biodegradation was dependent upon ecological factors such as salinity, temperature, pH/Eh and water-sediment ratio. In addition, the chemical structure of the phenolic compound itself was a key factor in compound disappearance and in its effect on important food web substrate rates, i.e., chitin degradation, in wetland systems. Biotransformation and biodegradation kinetics of several toxicant classes were examined with microcosm mathematical model estimates comparing closely to chromatography residue data and in situ results. A ranking criteria of relative toxicity for potentially hazardous chemical classes in coastal wetlands was achieved.
Portier, Ralph Joseph, "Correlative Field and Laboratory Microcosm Approaches in Ascertaining Xenobiotic Effect and Fate in Diverse Aquatic Microenvironments." (1982). LSU Historical Dissertations and Theses. 3817.