Date of Award

1996

Document Type

Honors Thesis (Colby Access Only)

Department

Colby College. Chemistry Dept.

Advisor(s)

Thomas W. Shattuck

Second Advisor

Frank A. Fekete

Third Advisor

Joceline Boucher

Abstract

Water samples from the Penobscot Bay Estuary and River were collected, and the particulate matter was filtered from the samples. Sections of the filters containing the particulate matter were analyzed using a scanning electron microscope (SEM) with an energy dispersive x-ray analysis system (EDS). Cluster analysis and discriminant analysis isolated groups of particles that had a similar composition. Twenty-three chemically distinct clusters were found. Principle component analysis suggested that certain particle types are related to a riverine source, some to an oceanic source, and some are constant throughout the system. The silicates appeared as the most prevalent particle type. Certain transition metals such as Fe and Ti appeared throughout the estuary and river. Heavy metal species have been detected in statistically insignificant quantities. Certain concerns had to be evaluated in conjunction with the actual analysis of Penobscot Bay water samples. The ion-exchange capacity of the silicates was such a concern. The principle purpose of this study was to determine if a wash could remove the NaCI predominance without disturbing the other particles, including the silicates and particularly colloidal species. Marine silts similar to those of the sample sites were suspended in a NaCI solution, and filtered. Some of the samples were washed with reagent grade water to remove NaCI while others were left unwashed as a control. Another issue was the detection limits of the elements involved in the SEM/EDS analysis. It was necessary to determine the minimum concentration value for each element which could be reliably and accurately determined by EDS analysis. Spectra from the multiple site study were used to determine these values. Determining the detection limits for the energy dispersive x-ray analysis system (EDS) is a difficult task. The signal to noise ratio was the primary factor in determining the size of a detection limit. Finally a study of the particulate matter as a function of depth was undertaken with samples from two sites in the Penobscot Bay Estuary. The procedures and techniques used in this study closely resembled those of the multiple site study with certain distinct differences such as the washing of these samples. The surface layer of primarily riverine particles was spatially homogenous. The bottom sample from the second site suggested powerful currents cleansing the area of many types of particles.

Comments

Full-text download restricted to Colby College campus only.

Keywords

Penobscot Bay, particle matter, scanning electron microscope (SEM), energy dispersive x-ray analysis system (EDS)

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