New Insights on the Dissolved Platinum Behavior in the Atlantic Ocean

Abstract

The water column profiles of dissolved Pt were determined in samples taken during the GEOTRACES GA02 section at three stations located in the North, Central and South West Atlantic Ocean. Average concentrations obtained in this study for dissolved Pt (0.22 ± 0.04 pM; n = 59) are in agreement with the only previous dataset for the Atlantic Ocean reported in the early nineties. However, results presented here do not show invariant concentrations with depth as previously indicated for the Atlantic and recently reported for the Pacific Ocean. Instead, these new data suggests that (i) atmospheric inputs can account for the observed Pt enrichment in surface waters of the North West Atlantic; (ii) conservative mixing control the Pt distribution in deep (>1000 m) waters; and (iii) oxygen may play a major role on the Pt distribution in the oceans, since similar trends of Pt with dissolved oxygen were observed with Pt depletion at water depths of maximum oxygen utilization. There is still, however, important open questions on the (bio)geochemistry of Pt in natural waters including the redox behavior of the Pt(II)/Pt(IV) couple and its impact on particle (inorganic and/or biogenic) reactivity, which impedes a better characterization of the observed distribution in this study. Also, potential analytical artifacts that could be behind the differences in the Pt distributions observed for the different ocean basins must be further explored