Behavior and fluxes of Pt in the macrotidal Gironde Estuary (SW France)

Estimated daily gross dissolved (PtD) and particulate Pt (PtP) fluxes at La Réole, the main fluvial entry to the Gironde Estuary, were 0.018-0.11 mol day− 1 (3.6-22 g day− 1) and 0.001-0.18 mol day− 1 (0.21-35 g day− 1) in November and March, respectively. Using Boyle's method, the daily net PtD fluxes from the Gironde Estuary to the coastal ocean were estimated at 0.03 mol day− 1 (6.5 g day− 1) for moderate discharge and 0.17 mol day− 1 (34 g day− 1) during high discharge, reflecting the regime-dependent magnitude of Pt remobilization along the salinity gradient. The findings of the study suggest that estuarine reactivity is of major importance for both the distributions of Pt in estuaries and its export to the global ocean.