Saturday, 9 February 2013

3 - Chemistry Team at Von Damm

Water sampling bottles are
lowered over the side of the ship.
The Chemistry Team got up early for a midnight deployment of the water sampling system. They use this to take up to 24 individual samples of water from the deep ocean and can filter up to a tonne of seawater through pumps mounted on the frame. All this water only yields a few grams of solid which is analysed later back in Southampton. Jeff Hawkes is leading the watch; he has spent the last three years using chemical sniffers to find hydrothermal plumes in different ocean environments.

The Von Damm plume is exciting and unusual because the fluid is rich in reduced gases but poor in metal-rich particles. Usually, hot hydrothermal vents emit particle-rich fluid (hence their name ‘black smokers’) but here the hot fluids are clear. Jeff directs delicate manoeuvres of the 5800 tonne ship so the water bottles, dangling two kilometres below us, stay in the plume while he snaps the bottle closed to capture the water.

These samples are key to our understanding of the dispersion and fate of the hydrothermal effluent in the deep ocean. Jeff and the team will be working on the samples for the next few years; analyzing a suite of elements and isotopes. These data will ultimately help us to understand how hydrothermal activity affects the highly sensitive ocean-climate system because these metals may fertilise life in the upper ocean.

By Rachel Mills

Aly Lough sets up the water filtration rig in the clean van. Aly wears blue nitrile gloves to keep the rig clean, the van is positively pressurized to stop airbourne contaminants entering the lab.

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