1. UK GEOTRACES 40° S Atlantic Ocean Water column Biogeochemistry
Eric Achterberg and Mark Moore

2. Modelled dust deposition (Mahowald, 2006)

3. Surface water dissolved Fe and Al along AMT17
DAl (nM)
DFe (nM)
dFe/Dal Micha Rijkenberg&Simon Ussher
Moore et al., submitted

4. ID-ICP-MS Isotope dilution-inductively coupled plasma-mass spectrometry
6 elements - not suitable for mono-isotopic elements
Can be used for Ag, Cd, Cu, Fe, Ni, Pb, Zn
Off-line preconconcentration
Single sample - 8 minutes extraction
Use of isotopic ratio
E.g. Fe56 (natural)
and Fe57 (spike)

5. Preconcentration 12 ml sample Spiked with isotope mixture
- 100 µl isotope mix
- Standard addition
- Buffer
1.5 M HNO3
12 ml sample
Spiked with isotope mixture
Standard addition for mono-isotopic elements (Al, Co, Mn)
Chelating resin
 1 ml elution

6. Accuracy
Accuracy verified by intercalibration samples from SAFe project and Geotraces project

7. East and West edges

8. Cadmium

9. Cadmium

10. Cd vs. P Cadmium as a tracer fro paleophophorus concentrations
Next slide put in historic Cd/P ratio (figure from paper) and compare to this study, see how the ratios hold for this work

11. Hypothesis for 40°S consortium
Bioactive trace elements control productivity along 40ºS in the Atlantic Ocean.
The bioactive trace elements are intimately involved in various physical-biogeochemical feedback loops that influence our climate

12. Objectives
Determine deep water TEI supply from diapycnal mixing and upwelling (incl. turbulence measurements)
Identify sources of TEI to the region through tracer measurements (Al, Ti, Mn)
Establish natural microbial community structure
Determine nitrogen fixation rates
Establish trace elements and nutrient streams through modelling

13. Conclusions
ID-ICP-MS - powerful technique for high accuracy multi-element detection in low volumes of seawater
HNLC status of region results in preferential removal of Fe in surface waters relative to other elements
Strong correlation observed between Cd and phosphate (in agreement with literature)
Mn confirms sedimentary source of Fe for Kerguelen region