Geochemical imprints of humans on ecosystems

Every human action has a fingerprint on the ecosystems, whether it is direct or indirect. Given the intense use of land and human resources, the human fingerprint is also a geochemical fingerprint. Especially after the Industrial Revolution, that intensified the global use of land [1] and elements associated to the use of metals and minerals [2].

Sedimentary records are sentinels of past changes in ecosystems, encapsulating insights from the past in each layer of sediment. With the advances in X-Ray fluorescence for elemental analysis (XRF), the acquisition of geochemical data is widespread across literature. One of the most evident geochemical imprints is metallic pollution. From Iron (Fe), Lead (Pb) and Copper (Cu) from ancient mining activities [3] to other heavy metals such us Mercury (Hg) and such us Lead (Pb) from industries or leaded gasoline combustion [4], sedimentary records reflect the impact of human activities in peaks of those elements [5]. This contamination with heavy metals can also be seen in tree-rings, especially for atmospheric pollution [5]. But not only metals, Sulfur (S) has also a clear anthropogenic signal, associated with industrialization [6]. Ladwig et al. [7] pointed out that the salts used for building roads heavily polluted with Sodium (Na) the nearby lakes.

Geochemical profiles can also track environmental changes on the catchment where the sediment record was sampled. Increases in terrigenous elements such us Titanium (Ti), Strontium (Sr) or Zirconium (Zr) can track changes in the erosion rates, which humans tend to increase with intensive land use changes or fire activities. However, climate and vulcanism play also a relevant role in those signals that is often indistinguishable from the anthropogenic.

In the Temporal Ecology and Biogeography laboratory (TEBlab) and collaboration with researchers from CREAF, GEO3BCN and the Azores University, we have developed an approach for analyzing elemental data (bio and geochemistry) though the characterization of trajectories, which allow us to infer the magnitude, direction and graduality of the changes focusing on the elemental composition of the sedimentary records. We have acquired a portable XRF gun, that can be used to obtain the geochemical composition of discrete samples of sediment and other types of samples.

The geochemical disruption caused by humans is not expected to be halted. Although advances in circular economy and resource use effectiveness, the mineral resources needed each year to cope up with the new infrastructures and developments are increasing drastically [8], especially for those related with the energetic transition and digitalization such us rare earths and Lithium (Li).

Author

Javier de la Casa, PhD student

References:

[1] Steffen, W., Broadgate, W., Deutsch, L., Gaffney, O., & Ludwig, C. (2015). The trajectory of the Anthropocene: The great acceleration. The Anthropocene Review, 2(1), 81–98. https://doi.org/10.1177/2053019614564785

[2] Peñuelas, J., Sardans, J., & Terradas, J. (2022). Increasing divergence between human and biological elementomes. Trends in Ecology & Evolution, 37(11), 935–938. https://doi.org/10.1016/j.tree.2022.08.007

[3] Mil-Homens, M., Vale, C., Naughton, F., Brito, P., Drago, T., Anes, B., Raimundo, J., Schmidt, S., & Caetano, M. (2016). Footprint of Roman and modern mining activities in a sediment core from the southwestern Iberian Atlantic shelf. Science of the Total Environment, 571, 1211–1221. https://doi.org/10.1016/j.scitotenv.2016.07.143

[4] Norton, S. A., Jacobson, G. L., Kopáček, J., & Navrátil, T. (2016). A comparative study of long-term Hg and Pb sediment archives. Environmental Chemistry, 13(3), 517–527. https://doi.org/10.1071/EN15114