Zinc and lead isotopes reveal human footprint on the most remote oceanic regions

5 June 2026

Benaltabet and coworkers (2026, see reference below) analysed labile (i.e., mostly biogenic and oxide phases) and refractory fractions of suspended particles collected in the upper 500 m during the GEOTRACES GP21 cruise from Chile to New Caledonia. They determined the zinc (Zn) concentrations and isotopic composition of these particles as well as those in the aerosols. To better establish the anthropogenic sources, the authors associated the measurement of lead isotopic compositions. The results speak for themselves: in this remote area, as far from the nearest civilisation as the International Space Station, significant Zn and lead (Pb) enrichment factors, light Zn isotope signatures, and Pb isotope compositions clearly trace industrial emissions, while zinc from natural sources was nearly undetectable. Given that Zn is a critical coenzyme for phytoplankton development, these findings once again confront humanity with the consequences of its excesses.

Figure 1: GEOTRACES GP21 sampling stations in the South Pacific Ocean.All stations were sampled for water column particulate profiles and atmospheric aerosols (red circles). The stations for which we present marine particulate Zn (and Pb) isotope data are outlined in white. Blue lines and symbols depict the cruise tracks and sampling stations of previous studies. General flow-path of surface currents is depicted by grey arrows. Figure generated using Ocean Data View.
Figure 2: Isotope compositions of Zn and Pb in marine particles and aerosols along with potential sources. δ66Zn vs 206Pb/207Pb. The expected long-term isotope composition of Australian- and South American-sourced aerosols (green and grey squares, respectively) is estimated using the upper and lower boundaries of δ66Zn and 206Pb/207Pb measured in aerosols from South America and (offshore) Australia. Also presented are the ranges of dissolved South Pacific subtropical gyre data as well as urban and South Pacific marine aerosols.
Figure 3: Marine particulate manganese/zinc (Mn/Zn) and phosphorus/zinc (P/Zn) ratios used to assess the relative fractions of anthropogenic, biogenic, and Mn-oxide-associated Zn endmembers. a Upper water column bulk particulate Mn/Zn presented against bulk particulate P/Zn ratios (entire GP21 dataset < 500 m, n = 213) along with the ratios of the three endmembers (diamonds). b Histogram of the relative fraction of Zn endmembers in GP21 marine particulate samples, estimated with the three-endmember mixing model, showing the major predominance of anthropogenic contributions. Error bars represent uncertainties derived from the replicate analyses of certified reference materials.

Reference:

Benaltabet, T., Gosnell, K. J., de Souza, G. F., Jasinski, D., Rickli, J., O’Sullivan, E. M., Steiner, Z., Achterberg, E. P., & Vance, D. (2026). Pervasive contamination of the remote open ocean with anthropogenic zinc. Communications Earth Environment, 7. doi:10.1038/s43247-026-03425-y

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