Quantifying Lake Sediment Elemental Abundance with a Scanning Electron Microscope
Location
CSU 204
Start Date
9-4-2012 3:00 PM
End Date
9-4-2012 4:00 PM
Student's Major
Chemistry and Geology
Student's College
Science, Engineering and Technology
Mentor's Name
Chad Wittkop
Mentor's Department
Chemistry and Geology
Mentor's College
Science, Engineering and Technology
Description
Our previous work quantified siderite (FeCO3) abundance within the sediments of Otter Lake, Michigan. Siderite forms in a restricted geochemical environment and is often associated with hydrocarbons and iron ore deposits. To further understand how siderite forms, we collected elemental data from Otter Lake sediments with a scanning electron microscope (SEM). SEMs are used to perform microanalysis by reflecting electrons off the surface and greatly magnifying the specimen. When electrons with several kilovolts of energy encounter a surface, X-rays are produced and emitted that show the characteristics of the atoms present. From the measurement of the wavelength of the emitted X-rays we are able to quantify how much of an element is present. We collected bulk elemental abundance data throughout the Otter Lake core in 20-cm intervals and plotted them against calendar years before present (cal yr BP). We then compared elements sensitive to reduction-oxidation (redox) with non-sensitive redox elements to further understand the controls of siderite production. We also examined siderite crystal morphology compared to various elemental abundances. We also tested whether the SEM elemental abundance data compares to previously collected data of a more reliable, but expensive method to quantify elemental abundance, inductively coupled plasma mass spectrometry (ICPMS). SEM’s elemental data shows that when more iron is available, the more abundant siderite is; except after 2200 cal yr BP, where iron is still available, but siderite is not produced. We also determined that SEM’s data is comparable to ICPMS data.
Quantifying Lake Sediment Elemental Abundance with a Scanning Electron Microscope
CSU 204
Our previous work quantified siderite (FeCO3) abundance within the sediments of Otter Lake, Michigan. Siderite forms in a restricted geochemical environment and is often associated with hydrocarbons and iron ore deposits. To further understand how siderite forms, we collected elemental data from Otter Lake sediments with a scanning electron microscope (SEM). SEMs are used to perform microanalysis by reflecting electrons off the surface and greatly magnifying the specimen. When electrons with several kilovolts of energy encounter a surface, X-rays are produced and emitted that show the characteristics of the atoms present. From the measurement of the wavelength of the emitted X-rays we are able to quantify how much of an element is present. We collected bulk elemental abundance data throughout the Otter Lake core in 20-cm intervals and plotted them against calendar years before present (cal yr BP). We then compared elements sensitive to reduction-oxidation (redox) with non-sensitive redox elements to further understand the controls of siderite production. We also examined siderite crystal morphology compared to various elemental abundances. We also tested whether the SEM elemental abundance data compares to previously collected data of a more reliable, but expensive method to quantify elemental abundance, inductively coupled plasma mass spectrometry (ICPMS). SEM’s elemental data shows that when more iron is available, the more abundant siderite is; except after 2200 cal yr BP, where iron is still available, but siderite is not produced. We also determined that SEM’s data is comparable to ICPMS data.
Recommended Citation
Lubenow, Brady. "Quantifying Lake Sediment Elemental Abundance with a Scanning Electron Microscope." Undergraduate Research Symposium, Mankato, MN, April 9, 2012.
https://cornerstone.lib.mnsu.edu/urs/2012/oral-session-13/2
