Europe: air pollution already in antiquity

Mining of the Romans increased lead pollution of the air tenfold

Two ice cores from the summit of Mont Blanc prove that the air over Eurropa was contaminated with lead and antimony even in Roman times. © Björn S. / CC-by-sa 2.0
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Mining with consequences: Even back in Roman times the air over Europe was polluted with lead and other heavy metals. The intensive mining of lead, silver and other metals in the Roman Empire increased the lead exposure of the air tenfold, as evidenced by ice cores from Mont Blanc. The high points of ancient air pollution were therefore in the second century before and after Christ.

The era of manmade air pollution did not begin until the age of industrialization. Even before that, mining in particular led to measurable pollution of the air, especially with heavy metals, among others in the cultures of the Andes, at the time of the Spanish conquerors, but also in ancient and medieval Europe. These traces of early air pollution can be demonstrated, inter alia, in ice cores from mountain glaciers.

Roman lead ingots from the mines of Cartagena in Spain. © Nanosanchez / Public domain

Retrospect on the air of antiquity

But just how good or bad the air was in European antiquity, there was only inaccurate data including an ice core from Greenland. That's why Susanne Preunkert from the University of Grenoble and her team have analyzed two ice cores that were taken much closer to the scene: they come from the ice of Mont Blanc, the highest mountain in the Alps,

The ice of the two cores goes back about 5, 000 years. "It provides us with a comprehensive record of air pollution from European mining and engineering activities from the Bronze Age to antiquity to the early Middle Ages, " the researchers say. For their study, they analyzed the levels of lead, antimony, and other heavy metals deposited in the ice that are typically released during metal extraction and processing.

Ten times more lead in the air

The result: Already at the time of the Romans, the air over Europe was no longer clean, but showed clear signs of air pollution. From about 350 BC, researchers recorded significantly elevated levels of lead and antimony in the ice of their cores for about 500 years. "The alpine ice shows that lead contamination in ancient times increased the natural background value of lead by up to ten times, " says Preunkert's colleague Michael Legrand. The antimony value increased sixfold during this time. display

The cause of this air pollution was the metal mining of the Rums, which was almost on an industrial scale. They extracted large quantities of lead and silver, mainly from mines in Spain and the British Isles. The metal was used for silver coins as well as for the mass production of lead water pipes.

Two highs and one low

The lead exposure of the ancient air shows two distinct highs, which coincide with phases of Roman expansion and economic strength, as Preunkert and her team noted. The first peak is around 250 BC, marking a time when the Roman Empire spread throughout the Italian peninsula. The second peak of lead exposure is around 120 AD, coinciding with the phase when the Roman Empire expanded into much of the rest of Europe.

Between these two phases of Roman expansion and intensive metal extraction, however, there was a period of upheaval, which is also reflected in the ice core data: Between the two pollution highs, there is a 100-year long phase, in which the lead contamination significantly was lower. "This reflects the time when the Roman empire was awed by wars and the transition from the Roman Republic to the Empire, " the researchers say.

Important also for today's measurements

The new data shows that ancient mining left significantly more traces in the air over Europe than previously thought. The old assumption that there was hardly any significant air pollution on our continent before the industrial revolution is refuted, the researchers say. This should also be taken into account for the determination of the "natural" background load as a reference for air quality measurements.

"The air pollution by the R istmer is indeed five to ten times lower than by the leaded petrol of the modern era, but it held much longer several centuries instead of only about 30 years" says Legrand. (Geophysical Research Letters, 2019; doi: 10.1029 / 2019GL082641)

Source: American Geophysical Union

- Nadja Podbregar