Title

The determination of ultra trace levels of mercury in environmental samples in the northeastern United States: Inferring the past, present, and future of atmospheric mercury deposition

Date of Award

2001

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Advisor(s)

Charles Driscoll

Keywords

Trace levels, Mercury, Environmental samples, Atmospheric mercury deposition, New York

Subject Categories

Analytical Chemistry | Chemistry | Environmental Sciences | Physical Sciences and Mathematics

Abstract

The interest in mercury (Hg) contamination lies primarily in the fact that fish containing high levels of Hg are a part of the human diet. However, the reactions and pathways of Hg before it is assimilated into fish tissue are complex, and in some cases still not well understood. Although Hg is naturally occurring, the concentrations that are measured today, from historical records such as sediment cores and ice cores, are higher than those in preindustrial times. This leads to the conclusion that anthropogenic activities have caused these increases, even in remote areas.

In this study the concentrations of total mercury (Hg T ) were measured in sediment cores from eight lakes in the Adirondack region of New York. Using the results, historical profiles were created for each lake showing the change in flux of Hg T to the sediments over the past 200 years. An increase of 3.5 times above preindustrial values was found, but there has been an evident decline in recent years. The watershed of the lakes was important in the accumulation of Hg in lake sediments.

Another portion of this study involved the analysis of Hg concentrations in water and sediment from 94 lakes in Vermont and New Hampshire. Relationships were developed with physical and chemical data from the lakes in order to elucidate some of the factors that influence the Hg concentrations in lakes in this region. The Hg concentrations were found to be most strongly related to the mean depth, residence time, and pH, and the concentrations of dissolved organic carbon, chloride, and dissolved oxygen of the lakes. The biggest influence of the watershed land use on Hg concentrations was its affect on the chemical characteristics of the lake.

Atmospheric emissions of Hg will be coming under more strict regulations in the forthcoming years. In order to implement regulations with the maximum effectiveness and still be cost effective, a better understanding of Hg behavior is imperative. With an ultimate goal of reducing human health risks from Hg contaminated fish, these results are another step towards shaping the future of atmospheric Hg deposition and its consequences.

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