23 July, 2002
I thought I should let you know why my last few journals have been posted so late in the afternoon of the day after the entry. For the past few days, I have been getting up just in time for lunch after going to bed very late. Once up, I usually spend time editing my journal. Although I try to write a draft before dinner on the day of the journal, things happen between dinner and when I post the journal, and they never seem to happen when scheduled. I always check in at the lab to get an update on times for the various tests at the station and try to plan my time based on the posted schedule. Different types of sampling take different lengths of time. The longest is perhaps the pumping of water. The group analyzing water for thorium-234 needs to pump water for fours hours straight. Everyone else looks forward to the pumping because they know they have a four hour period without any other sampling going on and without any other schedule changes! That’s a long block of time on board a research ship, and people find lots of ways to fill it. They do laundry, work out in the ship’s gym, read, sleep, watch a movie, or use the time to process their own samples and get caught up with data recording.
Rick Nelson from the Bedford Institute of Oceanography in Halifax, Nova Scotia, and Sandor Mulsow from the International Atomic Energy Marine Radioactivity Laboratory in Monaco are responsible for doing the water pumping (and making everyone else very happy for four hours). Their work is a part of a project being conducted by Bradley Moran of the University of Rhode Island. At the designated time, they put four pumps into the water, each at a different depth. For their work, it is the top 200 meters of water that are the most important. The isotope thorium-234 (remember that an isotope is a different form of an element due to a different number of neutrons) has a relatively short half life (a measure of how fast an element will decay), and it sticks to parcticles in the water. By measuring the amount of thorium-234, they can get an indication of “how fast the mill grinds.” Radioactive elements act as a sort of “clock,” showing us the rate at which things happen. Rick and Sandor are able to get a picture of the short term movement of parcticles (POM or parcticulate organic matter) through the water.
The pumps work very effectively to filter out POM, and that can actually present somewhat of a problem. The pumps were designed for work in the ocean basin where, due to the greater depths, there is far less organic matter. Because we have been sampling in the Chukchi Sea which is so productive, the filters collect an enormous amount of material. It took nearly nine hours for Rick to complete the final filtering of approximately 1000 milliliters of water (about a quart)! Once the filtering is complete, the filter itself is burned in a 500 degree oven in order to produce an ash. They then measure the gamma radiation released by the thorium in the ash. As the gamma counter works on the sample, a computer records and graphs the resulting data.
Check out the pictures below to see what the actual filter looks like. The picture of Sandor also gives you a much better idea of the mustang suits we all wear on deck.
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