Mercury and methylmercury in the sediments of Lake St. Clair (Michigan, Ontario).

摘要

Lake St. Clair is a wide, shallow lake situated midway between Lake Huron and Lake Erie. The lake basin has been a region of significant mercury contamination for several decades due to intense industrial activities, largely those of chlor-alkali plants located up-river. As the lake flushes very rapidly (t R ∼ 4 days), little sedimentation takes place, hence it was expected that most contaminants would be carried downstream to Lake Erie. The persistence of Hg in the upper sediments and biota indicates that some other processes may be at work. Inorganic mercury that has been released to the environment can be converted through bacterial and photochemical pathways to methylmercury, which is highly toxic and is an efficient bioaccumulator. It was suspected that the delta of the inflowing St. Clair River has acted as a sink while the original discharge was taking place, and now, with its large areas of marshland and standing water, it may be converting this to methylmercury and releasing it to the ecosystem. In order to investigate this, sediment core samples were collected from various sites in the lake and the delta in the summer or 1997. Previous work in quantifying methylmercury in the environment has relied largely on methods which provide indirect confirmation of methylmercury (e.g. CV-AAS, GC-ECD). As a part of this study, a method was developed to overcome this limitation. In this method, methylmercury is isolated from the sediment matrix by solvent extraction and then derivatized to form a species more amenable to separation by gas chromatography. Element-specific detection was accomplished using a microwave plasma-atomic emission detector. Paper copy at Leddy Library: Theses u26 Major Papers - Basement, West Bldg. / Call Number: Thesis1999 .T66. Source: Masters Abstracts International, Volume: 39-02, page: 0508. Adviser: Brian J. Fryer. Thesis (M.Sc.)--University of Windsor (Canada), 1999.