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UK GEOTRACES 40 ° S Atlantic Ocean Water column Biogeochemistry

UK GEOTRACES 40 ° S Atlantic Ocean Water column Biogeochemistry. Eric Achterberg and Mark Moore. Modelled dust deposition (Mahowald, 2006). Surface water dissolved Fe and Al along AMT17. DAl (nM). DFe (nM). dFe/Dal Micha Rijkenberg&Simon Ussher Moore et al., submitted.

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UK GEOTRACES 40 ° S Atlantic Ocean Water column Biogeochemistry

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  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. 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) ID-ICP-MSIsotope dilution-inductively coupled plasma-mass spectrometry

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

  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

  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

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