Shelf Sea Biogeochemistry blog

Showing posts with label radium. Show all posts
Showing posts with label radium. Show all posts

Friday, 10 April 2015

DY029 Fe transect trilogy: The return of the Team Iron

Metal contamination free science on a metal ship: trace metal saga

Main characters:  The Incredible Team Iron

Maeve Lohan (University of Plymouth)
Antony Birchill (University of Plymouth)
Dagmara Rusiecka (University of Southampton/Geomar, Kiel)
Amber Annett (University of Edinburgh)

Metal contamination (Everywhere)

 . / . 

 DY029 Fe transect trilogy by Dagmara Rusiecka (University of Southampton/Geomar, Kiel): The return of the Team Iron 

It’s been less than four months since DY018 and ‘Team Iron’ is back on board RRS Discovery waiting with excitement for the first cast of the first iron transect…

Encouraging message from the Team Iron fan club onboard. Photo by Chata

April the 7
, 11PM, kick off: Team Iron is all dressed up in clean white Tyvek suits and white mop hats rushing around in the clean sampling lab. 24 grey bottles designed specifically for the trace metal sampling returned from 2500m and with gloved taps were very quickly transferred from the deck to the clean lab to minimize the risk of metal contamination. Now, they’re racked on the wall, safe, secured and ready for a solid 4 hour sampling session. Team Iron wearing ‘dirty’ gloves is tackling through sample bottles for other scientists; DOM (dissolved organic matter), SPM (suspended particulate matter), alkalinity, flow cytometry, chlorophyll a, oxygen, salinity. Finally, it’s time for the ‘clean’ gloves and the ‘clean’ samples!

In meantime, outside of the clean lab, Amber Annett is already waiting for the stainless steel rosette to return on deck with 480L of seawater just for Ra (Radium) isotope measurements at only a few depths! In plastic cubic containers she’s carrying 20L of seawater one by one on her shoulder to her container. She’s not only strong but also a lucky girl. No need to worry about the metal contamination but hey, she needs liters of seawater to detect the short-lived Ra 224 isotope! Therefore, the rosette is deployed again for another round and more water for Amber.

Team Iron in the zone of discussing results from DY018. Photo by Jose Lorenzo

All geared up with clean sampling clothing. Team Iron is tackling through ‘clean’ sample bottles.  5 liters for chromium isotopes, 1 liter for iron isotopes, 500 ml for copper speciation ……. It’s time for their own samples. 250 ml for iron speciation, one 125ml bottle for trace metals and one 125ml bottle for iron.

3 AM: Team Iron is packing samples from the first cast whilst the ship is already at the next station and the crew is ready for the next cast. “Here we go again guys! 6 stations to go!” and the process is starting all over again.

Rare and short appearance of 'Rosie' the trace metal clean titanium rosette with bottles on deck. Still with gloved taps, almost ready for the deployment. Photo by Dagmara Rusiecka

Coming up soon:
Volume two: The Two transects
Volume three: The Fellowship of the Iron: Final transect

So why do we do what we do?

As some of you may know, iron is an essential micronutrient to marine organisms present at very low concentration. It influences phytoplankton productivity, community structure and ecosystems and is a limiting factor on primary production in some regions. Our aim is to capture the mechanisms of iron off-shore transport to the open ocean that currently are unknown.

Tuesday, 17 March 2015

Studying radium concentrations in the muddy sendiments off the north west coast of Cornwall.

On Tuesday we continued with our coring as well as performing a few more CTDs.  Amber Annett (Edinburgh University) is taking water column samples from the CTD and sediment samples from an instrument called a megacorer, in order to study radium concentrations in the sediment and the overlying water, and she has written the following blog piece about her work.

Naturally occurring radium is a very useful element for studying many different shelf sea processes. This is because it is radioactive (no, not that dangerous sort of radioactive!), and we know the rate at which radium naturally decays. This means that radium can act as a kind of internal clock for a parcel of water, telling us how fast things happen.

Luckily, radium is also extremely rare in seawater, so even though it is a radioactive element it is present at concentrations thousands of times lower than anything we would need to worry about. Even though I use extremely sensitive detectors to measure radium (photo), because it is so rare I still need to sample a very large amount of water  to collect enough for a useful measurement– up to 150 litres for just one sample.

Amber's radium detectors on board the RRS Discovery

Radium comes from rocks, and there is plenty of lithogenic (rock) material in the sandy, muddy sediments on the UK continental shelf here off the north west coast of Cornwall. I am using a megacorer to collect pore water (water from in between the sand and mud particles inside marine sediments) and samples from the sediment-water interface, as well as a CTD to measure radium in the water column above. This lets me look at how much radium diffuses out of the sediments and into the sea, as well as how quickly this process occurs. This work is part of the trace metal group (SSB Work package 3), who are ultimately looking at how shelf seas can act as a source of iron, an essential nutrient for marine plant life, that is very scarce in many areas of the ocean. 
We will be using radium concentrations to help track iron that comes from sediments, where it goes and how fast it gets there.