Studies of sediment cores from the sea floor and the coastal regions surrounding the Aegean Sea show that humans contaminated the environment with lead early on in antiquity. A research team led by geoscientists from Heidelberg University conducted the analyses, which revealed that human activity in the region resulted in lead contamination of the environment approximately 5,200 years ago – much earlier than previously known. Combined with the results of pollen analyses from the sediment cores, this contamination also offers insights into socioeconomic change in the Aegean, even reflecting historical events such as the conquest of Greece by the Romans.
The Aegean region gave rise to some of the earliest cultures of ancient Europe. The research team investigated when and to what extent early human activities in the region affected ecosystems both on land and in the marine environment. To this end, the team analyzed 14 sediment cores from the floor of the Aegean Sea and the surrounding coastline. One core from a peat bog offered up the earliest known evidence of environmental contamination with lead. The researchers dated this lead signal to approximately 5,200 years ago, about 1,200 years before the previously earliest known evidence of environmental contamination with the heavy metal that is traceable to human activity.
"Because lead was released during the production of silver, among other things, proof of increasing lead concentrations in the environment is, at the same time, an important indicator of socioeconomic change," states Dr Andreas Koutsodendris, a member of the Palynology & Paleoenvironmental Dynamics research group of Prof. Dr Jörg Pross at Heidelberg University's Institute of Earth Sciences. The sediment cores the Heidelberg scientists analyzed contained lead as well as pollen, which allowed them to reconstruct vegetation development in the Aegean region. The pollen content pointed to how the land was used. "The combined data on lead contamination and vegetation development show when the transition from agricultural to monetary societies took place and how that impacted the environment," stresses Jörg Pross.
Lead concentration rose significantly about 2,150 years ago, accompanied by intense deforestation and increasing agricultural use, as indicated by the composition of the pollen spectra. Starting then, lead contamination is also evident in sediment from the floor of the Aegean Sea – the earliest record worldwide of human-caused lead pollution in the ocean, emphasizes Andreas Koutsodendris. "The changes coincide with the conquest of Hellenistic Greece by the Romans, who subsequently claimed for themselves the region's wealth of resources," adds Heidelberg archeologist Prof. Dr Joseph Maran. The Roman conquerors thus pushed the mining of gold, silver, and other metals, with ore extraction and smelting also requiring wood.
The sediment cores from the Aegean Sea were collected during expeditions of the METEOR and AEGAEO research vessels between 2001 and 2021. The German Research Foundation (DFG) and the European Union financed the research expeditions, with the DFG also funding the most recent research work. Along with researchers from Heidelberg University, scientists from Berlin, Frankfurt (Main), Hamburg, Hohenheim, Tübingen and Greece also participated in the studies. The results were published in the journal "Communications Earth & Environment".
