In situ sea urchin carbonates analysis by LA-MC-ICP-MS to identify lead isotopic signatures: A case study at Trindade Island (South Atlantic Ocean versus anthropogenic)

Isabella Robert Rodrigues,Anderson Costa Dos Santos,Maria Virginia Alves Martins,Lucas Guimarães Pereira Monteiro,Luiz Felipe Romero,Armando Dias Tavares,Mauro César Geraldes

doi:10.1016/j.rsma.2023.103082

Isabella Robert Rodrigues, Anderson Costa Dos Santos + Show 5 more

https://doi.org/10.1016/j.rsma.2023.103082

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Abstract

Isotope ratios of lead (Pb) are increasingly applied to trace pollution sources in marine settings, using mostly carbonate remains of living organisms. However, this data has never been acquired in sea urchin carbonates. Sea urchins are widely distributed in marine settings and have been recognized for their ability to bioaccumulate heavy metals and their skill to track environmental changes. Thus, this work intends to perform, for the first time in-situ analysis of Pb isotope ratios using LA-ICP-MC-MS in sea urchin spines collected on the beaches from Trindade Island (SE Brazil). Trindade Island is a protected environmental area, almost uninhabited, located in a remote region of the South Atlantic Ocean (1200 km from the mainland). The results obtained in sea urchins spines collected on the beaches from Trindade Island varied from: 1.03 to 1.30 (mean 1.18 ± 0.06) for 206Pb/207Pb; 1.44 to 2.23 (mean 2.10 ± 0.07) for 208Pb/206Pb and 2.22 to 2.87 (mean 2.48 ± 0.15) for 208Pb/207Pb. The biplot of 208Pb/206Pb versus 206Pb/207Pb ratios show greater dispersion of isotopic values in the sea urchin spines than in the geogenic data of the Vitória-Trindade Ridge (VTR; used as reference) and the surface water from the Tropical Atlantic Ocean. While the Pb isotope ratios of rocks and sediments of the VTR are quite similar and present intermediate values, a significant variation of the isotopic signature in the sea urchin spines was observed. The comparison of the sea urchin spines 206Pb/207Pb ratios with data published in the literature from several materials suggests the presence of anthropogenic contamination on Trindade Island caused using fossil fuels. The range of variation of Pb isotopes analyzed in sea urchin spines suggests mixing between the natural source (the rocks and sediments of the Vitória-Trindade Ridge) and surface water masses of the Tropical South Atlantic and anthropogenic sources.

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