A geochemists life during the RAPID Challenge

Having the opportunity to be part of this year’s RAPID Challenge team has given me the chance to step out of day-to-day PhD life and into a modern scientific adventure. My main role on board is to collect seawater samples from a CTD (an instrument suite with water sampling bottles primarily measuring conductivity, temperature and depth - and for this cruise oxygen). The CTD takes a profile (anything from 5800m up to the surface) and then I determine the amount of dissolved oxygen in each sample. 

The CTD being deployed over the side of the ship.

Sounds easy, right? But unfortunately the challenges started immediately. During the transit to Tenerife, I attempted to set up a new titration system in the clean chemistry lab on board. Challenge 1: getting used to the very enclosed, very lonely, very warm clean lab whilst fighting to find my sea legs. Challenge 2: getting consistent results with the titration unit. 

Having failed on both counts, I explored a double plan B: New, spacious, cooler lab; and a different titration unit. Much better! My day starts with chasing all the bubbles out of the sampling tubes in the titrator. So far, this has been a long and frustrating process, struggling to shift smaller bubbles out of the tubes, and generally finding one gets stuck right at the very end of the aspirator (the part of the tube that enters the sample).

Sara using the oxygen analysis kit

Next, I check to see if the titration unit is behaving by measuring numerous “blank” and “standard” samples to make sure the numbers are consistent. The main stage is measuring the real samples collected from the CTD and then plotting the oxygen profile. 

My favourite part is collecting the samples from the CTD (although this is usually done at unsociable hours in the middle of the night). It’s refreshing to go outside, and I always feel a sense of wonder when handling water that was 5km below me only a few hours previously. Whilst filling the glass flasks, we must measure the temperature of the water. This has turned into a game to keep the spirit alive at 3am – whoever guesses the closest temperatures wins a Hobnob. I wish I was better at this game….!

Written by Sara (posted by Darren)