Neodymium and hafnium isotopes and rare earth element concentrations from water bottle samples measured during METEOR cruise M121 along the Congo River plume (GEOTRACES cruise GA08)

To better understand the inputs of riverine REEs and Hf to the ocean and their impact on the open ocean we collected filtered seawater samples from 16 full water column profiles along the Congo River plume at the coast of Congo and Gabon and along an offshore section at 3°S, complemented by three freshwater samples collected directly from the Congo River. The water samples from the Congo River plume were collected during GEOTRACES cruise GA08 with German RV Meteor (M121) in November and December 2015 with a stainless steel CTD rosette and a towed fish for surface waters. River water end-member samples from the Congo River at zero salinity were taken upstream by boat in May, July and October 2017 near the center of the river at ~6°S and ~12.5°E (stations 12.1–12.3). We determine for the first time REE and Hf concentrations and isotope compositions within the Congo River plume and quantify Nd and Hf fluxes. Based on these data we evaluate how far the Congo River plume is traceable by these geochemical parameters, how it contributes to their budgets in the South East Atlantic Ocean, and to which degree the Nd and Hf isotope and REE distributions can be used as water mass tracers in areas of high continental inputs.