Trace metal fluxes of cadmium, copper, lead and zinc from the Congo River into the South Atlantic Ocean are supplemented by atmospheric inputs

Science Highlights

21 February 2024

The Congo River, as the second largest river globally, supplies vast amounts of trace metals (TMs) to the South Atlantic via a far extended freshwater plume. However, existing work suggests a discrepancy within the TM budgets in the Congo plume and points to unknown source other than the Congo River or shelf sediments. Considering high precipitation rates of >200 mm across the Congo shelf during October to December, in a global context, coincident with the timing of GEOTRACES cruise GA08, Liu and colleagues (2023, see reference below) show that wet deposition (rainfall) augments some fluxes of TMs from the Congo River. Specifically, wet deposition contributed the equivalent of 43% dissolved cadmium, 21% dissolved copper, 20% dissolved lead and 68% dissolved zinc of the Congo River fluxes. This finding demonstrates an important role of wet deposition in contributing TMs to such a major river plume and to the open ocean.

Figure 1: Upper panel shows an overview of the study region including salinity (coloured dots), sampling locations of surface seawater (white circles), river water (red cross) and rainwater (stars). Background colour shows precipitation rates during the period of sailing. Green line highlights the Congo shelf region. Lower panel shows TM fluxes to the Congo shelf from the Congo River (red), rainfall (light yellow for total dissolved TMs and dark yellow for dissolved TMs) and dry deposition (black), respectively.

Reference:
Liu, T., Hopwood, M. J., Krisch, S.,Vieira, L. H., & Achterberg, E. P. (2023). Trace metal fluxes of Cd, Cu, Pb and Zn from the Congo River into the South Atlantic Ocean are supplemented by atmospheric inputs. Geophysical Research Letters, 50, e2023GL107150. Access the paper: https://doi.org/10.1029/2023GL107150

Latest highlights

Mercury content and isotopes in bird’s guano: a window to reconstruct past climates

By analysing peat cores, Chuxian Li and her colleagues have shown how populations of nesting seabirds have fluctuated on a sub-Antarctic Island over the last 8,000 years.

Contraction of North Atlantic Deep Water during glacial times: a paradigm called into question

Blaser and co-authors propose a new distribution of deep-water masses in the Atlantic Ocean during the Last Glacial Maximum and the Heinrich Stadial..

Authigenic radiogenic neodymium isotope composition traces millennial-scale overturning circulation variability in the Arabian Sea

The neodymium isotopic signature of the sediment authigenic fraction is, a priori, a valuable proxy for reconstructing deep-water mass trajectories…

Magmatic activity at the Carlsberg Ridge in the Indian Ocean triggered by glacial sea-level variation

De and colleagues provide a high-resolution record of magmatic input and associated hydrothermal activity over the past 49 kyr from a core recovered from a magmatic segment of the slow-spreading Carlsberg Ridge in the Indian Ocean.

Rechercher