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Apatite in a glacial lake

University of British Columbia

Apatite is a common accessory mineral in the source rocks for the glacial debris supplying recent sediments to many Canadian lakes. Chemical analyses of sediments in Kamloops Lake, British Columbia suggest that this apatite may comprise a significant portion of the total phosphorus load to the lake, thereby overestimating the trophic state that would be predicted by the relationship between total phosphorus load and the ratio of mean depth to flushing time. A method has been developed which uses scanning electron microscopy and energy dispersive X-ray spectrometry for direct identification of apatite. This method has been used to examine the apatite content of various size fractions in Kamloops Lake sediments. Apatite concentrations obtained by this direct examination correlate well with the apatite concentrations of the indirect chemical analyses and indicate that, in addition to comprising as much as 70% of the total phosphorus load, apatite may comprise as much as 20% of the "dissolved" (<0.45 μm) inorganic phosphorus load. Therefore, estimates of lake productivity could be erroneous even if dissolved rather than total phosphorus values are used for the estimation.

Text

2010-03-03

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http://hdl.handle.net/2429/21451

Geological Sciences

University of British Columbia

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