Sunday, January 08, 2006

Sampling introduction!

Our new comers made it out in the boats today for a deep sampling out at Station E. The purpose of this event was to try and determine where the DMS concentration in the water column drops to 0. Other side points to going out were to give everyone a good idea on how things work out on the boat and why it can take so long to complete sampling. Unfortunately this was not one of the best days we have had out at Station E, but it also gave a good perspective to what types of things can go wrong while out sampling.

A couple of the problems that occurred out here started with a malfunctioning depth sounder. The wind combined with the current was moving us off station; therefore we did not know what depth we could lower our bottles to safely. Plus we were given a new measuring pulley, called a block, for sending the bottles down to the specific depth and this block measured in feet. We have been operating with a metering block since the beginning; it gives us time to stop the winch in the correct place, it was more exact and meters are the unit of measure that all of the teams use out here. This just tested out math and ability to remember conversions. We also found out mid drop that the block was slipping and not measuring, leaving us with incorrect depths. Wait there is more… We decided that since all were feeling a little green, some more green than others, that we would head back with just a 10 meter and surface sample. In bringing up the bottles to the 10 meter point the waves picked up and the first bottle hit the side of the boat, breaking off the sampling valve and spilling the sample. We needed to come back with something so a new bottle was recocked and sent back down, even though none of us really felt like doing anything else. After much time being invested this sampling was successful. Ron performed DMSPd filtrations right on the boat to determine what type of effects can occur to the samples while they are in transit back to the lab and waiting for us to filter and prepare. On Research Vessels, where we are used to performing this analysis, we have the ability to process samples instantly, we feel this gives a much more precise measurement.

Our new members now have a great appreciation for the difficulty involved in the sampling process.

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