This week I am learning how to process the sediment samples that we have collected from our cruise. On the ship, once we were through extracting the pore water from the centrifuge tubes the samples were then placed in a freezer. While out to sea, one of the cores that we collected was cut up into twelve intervals instead of nine like the rest. Once we got back to campus, this was the core that I began to process. The first step is to take the samples to the core lab on the south side of campus.
Since 1960, the College of Earth, Ocean and Atmospheric Sciences (CEOAS) at Oregon State University
(OSU) has maintained an active program in Marine Geology, and CEOAS
continues to be one of the leading oceanographic institutions involved
in exploration, research and the collection of marine samples. To
preserve these materials for future research, Drs. Ted C. Moore and
LaVerne Kulm in 1971 established the OSU Core Lab, now known as the OSU
Marine Geology Repository. At present, the OSU Marine Geology Repository archives 6,094 sediment
cores totaling 15,952 m of core, 10,025 rock samples from 545 dredges,
2,200 deep-sea manganese nodules, 1,627 sediment trap samples, 693
plankton tow samples, and other materials, including lake sediments and
lake drill cores. Sample requests are increasingly high with more than
27,000 samples distributed over the last three years and more than
175,000 since 1972.
I enjoy going to the core lab because it is like walking into a marine sediment museum. You are sure to find something fascinating to look at! But alas, we take our samples there because they have freeze dryers that are available for use. Since the samples are in centrifuge tubes, it takes about two days for them to be completely freeze dried. After they are done, we then take them to the lab and break up the sediments and pour them into appropriately labelled bags. The next step is to break up the sediment and then use the scale to weigh out approximately 2-3g of sample. We keep the samples separated by interval, and we place the samples into falcon tubes that have previously been cleaned with nitric and Milli-q water. Falcon tubes are tubes that can be used in a centrifuge, but they are nicer then the ones used on the cruise because they have measurement marks. Milli-q water is water that goes through a purification processes involving successive steps of filtration and
deionization to achieve a purity expediently characterized in terms of
The next step for the samples is to complete a process called leaching. In this process, we are removing soluble or other constituents from by the action of a percolating liquid. There are two reagents that we use on the sediments to complete the leaching. The first one is buffered acetic acid, and the second is hydroxylamine.
Next, I begin the process by using Milli-q (MQ) to wash the sediments and putting them in the centrifuge and repeating this step three times. Then, we add the first reagent, buffered acetic acid. Then we use the vortex to shake the samples for the next two hours. The vortex is simply a machine that moves back and forth shaking the samples you have placed on it.
Overall, I have really enjoyed working on this part of the process. It is relatively time consuming, and one must be very detailed oriented on the follow through. Next week, I will be heading back into the clean room for the next step.