The key facts

  • Traces of mercury-based pigments used by the Maya have been found in the sediments of Lake Cobá and Lake Xcanche in Yucatán
  • During the Classic period, mercury concentrations reached 18 µg/g, and accumulation proceeded tens of times faster than usual
  • The rise in pollution coincided with a decline in cyanobacteria, algae, mollusks and crustaceans

Mercury in the lakes of Yucatán

The widespread use of mercury-based pigments may have caused severe pollution of water bodies and soils in Maya cities and become one of the factors behind the decline of this civilization. That is the conclusion reached by an international team of scientists led by specialists from Auburn University in the United States; the results were published in the journal Science Advances.

What the analyses showed

The Maya widely used red pigments based on mercury, including cinnabar, to decorate objects, buildings and burials; archaeologists have found traces of them in ancient cities and the surrounding soils. To test the hypothesis about damage to ecosystems, the researchers studied the bottom sediments of Lake Cobá and Lake Xcanche on the Yucatán Peninsula, next to which large settlements had stood, and, for comparison, two lakes located far from ancient cities.

The scale of the pollution

An analysis of soil layers showed that during the Classic period, from 250 to 950 CE, mercury concentrations in some sediments reached 18 micrograms per gram, and the rate of accumulation of the metal was tens of times higher than in other historical periods. The rise in pollution coincided with a decline in the numbers of cyanobacteria, algae, mollusks and crustaceans, indicating serious changes in aquatic ecosystems.

Caution in the conclusions

The authors believe that mercury pollution could have aggravated the environmental problems of Maya cities and become one of the factors in their decline. At the same time, as Gazeta.Ru notes, the study does not prove that mercury was the cause of the disappearance of large settlements in the ninth century: other circumstances could also have contributed to the crisis. Earlier, the same newspaper reported that a ruined Maya city was not abandoned for hundreds of years.