Organic copper complexation may stabilise seawater stable copper isotopic composition

Three deep-sea profiles were produced for the analysis of copper (Cu) concentration, along a transect covering very different biogeochemical regions: the oligotrophic North Tasman Sea (30ºS), the Tasman Front (40°S) and the productive waters of the Southern Ocean in the south (46°S).

Despite these differences, the Cu isotope composition of all three profiles was relatively homogenous. This homogeneity is attributed to the fact that more than 99% of the Cu is organically complexed, measured as part of the same study (Thompson et al, 2014; see references below). It is therefore argued that organic complexation stabilises heavy values of seawater stable copper isotopic composition (δ65Cu).

The authors also propose that decomposition of organic Cu complexes in environments such as anoxic basins may provide an isotopically heavy source of Cu for further scavenging and/or removal to the sediments. Such mechanism would help to balance the oceanic budget of δ65Cu, discussed in Little et al, 2014 (see reference below, and GEOTRACES science highlight).

14 Thompson l

Figure: Three dissolved copper concentration profiles versus depth (left panel) along with the isotope composition for dissolved copper (right panel). Samples were collected from three stations (P1, P2 and P3) occupied in the Tasman Sea region.


References :

Little, S. H., Vance, D., Walker-Brown, C., & Landing, W. M. (2014). The oceanic mass balance of copper and zinc isotopes, investigated by analysis of their inputs, and outputs to ferromanganese oxide sediments. Geochimica et Cosmochimica Acta, 125, 673–693. doi:10.1016/j.gca.2013.07.046 Click here to acces the paper.

Thompson, C.M., Ellwood, M.J., Sander, S.G., (2014). Dissolved copper speciation in the Tasman Sea, SW Pacific Ocean. Marine Chemistry, 164: 84-94. doi: 10.1016/j.marchem.2014.06.003 Click here to access the paper.

Thompson, C.M., Ellwood, M.J., (2014). Dissolved copper isotope biogeochemistry in the Tasman Sea, SW Pacific Ocean. Marine Chemistry, 165: 1-9. doi: 10.1016/j.marchem.2014.06.009 Click here to access the paper.

Latest highlights

Science Highlights

Loss of old Arctic sea ice increases methylmercury concentrations

Researchers from the SCRIPPS, the Stockholm Natural Museum and the Mediterranean Institute of Oceanography show the importance of sea ice composition on methylmercury budgets


Science Highlights

Estimating Atmospheric Trace Element Deposition Over the Global Ocean

A recently developed method based on the natural radionuclide Be-7 has provided a means to estimate the bulk atmospheric trace element deposition velocity

Science Highlights

Dissolved gallium unravels Pacific and Atlantic waters in the Arctic Ocean

Whitmore and co-workers demonstrate that the dissolved gallium distribution provide a better water source deconvolution than the nutrient tracers


Science Highlights

Precise estimate of the mercury export from the Arctic to the Atlantic Ocean

Using new observations acquired during GEOTRACES Arctic cruises, a refined arctic mercury budget has been established