Accessing the Past: A Sediment Core Revealing Anthropogenic Impacts of Technology-Critical Elements on the Marine Environment.

Abstract

One group of elements attracting more and more attention are so-called technology-critical elements (TCEs). In comparison with legacy pollutants, the anthropogenic impact of TCEs on the environment might still be minor, but various applications introduce them to the most remote places in the world including the marine environment. One area prone to pollution is the Baltic Sea, partly due to the lack of water exchange with the North Sea. In this study, a sediment core from the German Baltic Sea was used to analyze a total of 42 elemental mass fractions. Based on radiometric dating of ²¹⁰Pb and ¹³⁷Cs, results were classified in a recent (2020-2000) and a past period (< 1920), calculating background concentrations based on the Median + 2 Median Absolute Deviation (M2MAD) and the Tukey Inner Fence (TIF). Six legacy pollutants (Ni, Cu, Zn, As, Cd, Pb) and six TCEs (Ga, Ge, Nb, La, Gd, Ta) are discussed in detail. Anthropogenic impacts of both groups were assessed, and local enrichment factors were calculated showing an increase for the legacy pollutants (past period (≤ 0.8); recent period (≥ 1.2)), but also a minor increase for Ga, Ge and Nb (past period (0.9); recent period (1.1)). Values ≥ 1.5, indicating anthropogenic impact, were found for Cu, Zn, Cd and Pb, but also for Ge. Proposed background values may be considered as baseline for future studies.