by Sinhue Torres Valdes
Hi there! My name is Sinhue and I am a Marine Biogeochemist (or chemical oceanographer), very interested (among other things) about how nutrients are distributed in the ocean. In a previous very cool blog post, Mark already talked about why we care about measuring nutrients and dissolved oxygen at sea. So, today I’ll talk a bit about what it involves and tomorrow I will talk about the team.
Leading a chemistry team is a massive responsibility (really cool one though!); first, you need to make sure that the data you obtain is of the best possible quality, and second (equally important), you need to make sure your team works safely, effectively, enjoys the expedition and learns a lot about how the ocean works and about carrying out analyses at sea (if we do not learn new stuff, then what’s the point of doing something kind of thing?!).
Measuring stuff at sea does not only involve collecting samples and putting them in a machine with some chemicals, out of which you get numbers. Collecting a sample may be the easy bit, but it is extremely important that you do it correctly and in a consistent way. If a sample is drawn incorrectly, then no matter how good the analysis is; the resulting number will be wrong!
We have to continuously prepare new chemical reagents and standards to calibrate the analyses, which also require things to be done properly. Even if you collected the sample in a proper way, if the chemical reagents and standards are prepared carelessly, the resulting numbers will be wrong!
Now, the instruments for the analyses; you need to understand how they operate, what can go wrong and how to correct issues you may come across. Understanding the basics of how the instrument works is crucial, since it’s the first step in the process of generating numbers where you can actually see if something is not going ok; whether a sample is contaminated, the chemical reagents are not working or the analytical instrument is malfunctioning……. or whether you forgot to connect a cable, a tube, or misplaced the chemical reagent 😉
Then there are the numbers themselves. How do you know if they are ok? Well, we do lots of quality checks, which involve analysing reference materials (stuff with ‘official numbers’ that we ought to be able to reproduce) and lab-made standards, which help you identify problems. Then, as soon as a single analysis is completed, we have to evaluate whether all the quality checks indicate the analysis was robust (or not).
We work continuously with the physics team because yet a further check involves putting the chemical and physics data (temperature, salinity, pressure) together to visually verify whether all the stuff we measure (what we term ‘variables’) are producing consistent results. Needless to say, it is a very time consuming process, but all the way worth doing as you go along. There’s nothing more satisfying than leaving the ship knowing that the data is ready to use.
Tomorrow you can read more about the team members that carry out all this work.
Images (photos and text by Penny Holliday): We arrived back at Rockall today, so here are more pictures of the rock and it’s present occupier Nick Hancock. Nick is raising money for charity by attempting a record solo stay on Rockall (www.rockallsolo.com). I will return to Rockall next summer when I will be leading another survey of the Extended Ellett Line.