Developing the Methodology of Centrifugation for the Separation of Grain Sizes in Mud-based Sediments

Smyth Fleming

For this project, methods of centrifugation were developed in order to separate mud-based sediments by grain size. The purpose of this project was to separate sediments into <2, 2-10, and 10-63 micrometer fractions. This would allow us to understand where clay minerals settle in sediments. Initial testing of speeds and times was done to determine ideal efficiency for the methods. The standard pipette method was used as a benchmark to determine the accuracy of the centrifuge separation. The pipette method separates <2 and 2-63 micrometer fractions, so a method of centrifugation was developed to mirror the pipette method. This two-part grain separation was within 10% error of the pipette numbers, therefore it was deemed comparable. Following this, a three-part grain separation was developed based on the methods of a separate paper (Pryor et. al. 2023). The method was replicated using the same mud sample, and those results were dried and run under x-ray fluorescence to find average elemental composition. Results showed that some metals like Magnesium and Rubidium were more present in smaller size fractions. However, the majority of metals were more present in the larger size fractions, contrary to the original hypothesis. In the future, it might be pertinent to rinse out the calgon before the drying process to have more accurate data. As of now, it has been determined that more tests need to be performed with mud samples that have larger percentages of clay. If this is continued, results may show settling patterns and help identify contaminants in Tampa Bay.