Title

The Distribution of Six Trace Metals in the Sediments of Lake Whatcom, Washington

Date of Award

2004

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Science

First Advisor

Matthews, Robin A., 1952-

Second Advisor

Bodensteiner, Leo R., 1957-

Third Advisor

Cancilla, Devon A. (Devon Anthony)

Abstract

I analyzed the distribution of copper, iron, manganese, sodium, lead, and zinc in the sediments of Lake Whatcom, the primary drinking water source for the city of Bellingham, Washington. Ongoing studies by the Institute of Watershed Studies suggest that a degradation of water quality is steadily occurring. Several recent studies have found elevated concentrations of various trace metals in the streams of Lake Whatcom’s watershed and in the surface microlayer of the lake.

In order to determine if sediments in Basin 1 were contaminated with trace metals, 91 sediment grab samples were collected along transects crossing the north end of the lake including Basin 1, Basin 2, and the northern end of Basin 3. The trace metals were extracted with a strong acid digestion and analyzed using atomic absorption spectroscopy. Other analyses included percent moisture, total volatile solids, sediment pH, sediment color, and sediment particle size.

Basin 1 differed significantly from the other two basins in several respects. Higher concentrations of organic matter were found throughout most of Basin 1, with several locations containing almost 20% organic matter. Elevated levels of copper, lead, and zinc were found in the Basin 1 sediments. The highest levels of iron and manganese, however, were collected in the sediments at the deepest site in Basin 3. In Basins 1 and 2, a zone of manganese accumulation seemed to exist at about 10 m depth.

Sodium was used as a conservative element, assumed to be ubiquitous and without a significant anthropogenic source. Variations in sodium were assumed to be due to natural concentrations in clay matrices, and sodium concentrations were used to estimate the anthropogenic portion of the remaining trace metal concentrations. When the trace metal concentrations were normalized by the sodium concentrations it was evident that Basin 1 was enriched in copper, lead, and zinc relative to the other basins.

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