Discussion

Application

Due to the highly porous nature of the sample, without a prior definition of the epoxy, the signal is highly variable and there are quite a lot lot of outliers, this could also be due to a slightly rough surface when ablating in Line 4. Lead, at the moment, seems to be the best candidate to view urbanization, but the other ratios such as Mg/Ca, Sr/Ca and Ba/Ca help quantify the natural system, and seasonality can be seen by the cyclical nature of those ratios.

Cost

Changes to the initial proposal were made, initially, the sample was going to be thin sections, however since they were not contiguous a switch to a different type of sample was made. Also, the scan rate was decreased, and the laser power was decreased from the original expectations because of the number of analytes. Totally in time, the laser was actively ablating for 3 hours, however, set up, method development, and data processing on Iolite took 7 hours. The final cost of laser ablation did turn out to be $219 when the laser was on, however, there were time periods of gas flow as breaks were taken between method development and ablation, which cost roughly $20. For a total of $239.

Improvement

In the future, it would be better to use epoxy that has been well characterized, and possibly doped in some element, or not used at all so that it can be easily extracted out as well as to sand the surface so that the travertine transect can lie completely flat. Also, it may be beneficial to run multiple full-line scans to get a better characterization of differences in geochemistry spatially.  It would be beneficial to stop halfway through if a future travertine is of similar size and length and take time to refocus the laser so that noise is reduced.