Wow, these past weeks have been crazy and exciting! The Hardison and McClelland labs have been bustling with activity. Two weeks ago we journeyed into Tropical Storm Bill to collect sediment cores from the Mission River. Sopping wet but satisfied with our successful field day, we returned to the lab and processed the cores late into the night. The next day, I sliced each of my ten cores (two from each of five sites) into four slices and split each slice in half. I measured the mass of one of the halves before placing in a drying oven. As these sediment samples dry, I measure the new mass to determine the percent mass lost due to water. This can be used to determine the porosity of the sediment. Next week, I will grind these samples with a mortar and pestle and determine the sediment organic matter (percent carbon and nitrogen) with an elemental analyzer.
I performed grain size analysis on the other half-slices by washing each through a set of sieves, stacked with the coarsest on top and the finest on bottom. As the sediment runs through the sieves, the coarser grains are trapped while the fines grains escape through the wire mesh onto the next sieve. After I wash each half-slice through the sieves, I place each size fraction in the drying oven. While this is a rather time-intensive process, I really enjoy discovering hidden components of the sediment such as shell fragments and coarse grains in muddy sediments.
I finished the grain size analysis of the Mission River sediments just in time for our field/lab extravaganza day on the Aransas River. This day was much warmer and sunnier, but the cores were harder to collect on account of sandier sediments that often fell out of the core before we were able to cap it. Nevertheless, I was happy about the sandy sediment because it makes grain size analysis easier. I am now finishing up the Mission River grain size analysis and preparing to gather the porosity and organic matter data next week!
Dr. Amber Hardison, Tricia, Xin, Dr. Jim McClelland, me, and Hengchen on the Aransas River