Using the Element Analyzer

After completing initial assessments of my cores, the next step in lab work was sampling each core for analysis in the Element Analyzer. This instrument combusts a small sample of dry sediment, passing the gasses through a series of chambers in order to analyze the gasses for percentages of Carbon, Nitrogen and Sulfur. With these percentage results (in addition to Carbon to Nitrogen ratios), geochemical changes related to changes in depositional environment are often apparent. Sulfur can be particularly useful since it often tracks changes from marine to freshwater inputs, where higher Sulfur levels are likely marine.

For analysis, I sampled each of my cores every 4cm in order to capture geochemical changes throughout the core. In areas thought to be transitions between different depositional environments, I sampled more frequently (2cm intervals). For each sample, I extracted a 1cm3 volume of sediment from the core using a small syringe and then freeze-dried these samples to remove water.

After the samples were freeze-dried, it was time to employ my fine motor skills. For each sample, I took small (4-6mg) weights of sediment, placed the samples into small tin capsules and folded each capsule tightly to prevent sediment from falling out. These small tin sediment packages were kept in a desiccator to stay dry as I folded over a hundred samples. I ran my samples over several days in addition to Sulfanilamide standards (with known concentrations of Carbon, Nitrogen and Sulfur) and triplicate samples which help ensure the machine is measuring samples accurately.

The results from the Element Analyzer showed clear transitions in elemental percentages. For exa mple, Sulfur in Farstadvatnet was very low in the upper ~45 cm of the core, below which it rose rapidly and remained high for nearly 230 cm. A preliminary interpretation is that this transition marks a transition from marine (higher sulfur) to freshwater (low sulfur). Using the transitions in these elemental percentages, in addition to the Magnetic Susceptibility and visible changes in sediment, I’m slowly piecing together the sea-level history of these lakes!

Sampling every 4cm using a syringe in preparation for Freeze-drying and the Element Anaylzer

Sampling every 4cm using a syringe in preparation for Freeze-drying and the Element Anaylzer

Preparing Samples for the EA

Preparing Samples for the EA

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