The ruins of Tikal, the Mayan city in Guatemala, were abandoned more than 1,000 years ago and rediscovered by a rubber collector in 1853.
Today, scientists may be closer to understanding why its inhabitants abandoned the city, the capital of a warring state that has become one of the most powerful Mayan kingdoms.
New research has found toxic levels of pollution in water reservoirs in the heart of the city, showing that water became unfit for drinking after drought in the ninth century.
This is contributing to the city’s decline and abandonment, according to researchers at the University of Cincinnati.
The city flourished between 300 and 850 AD and is called by the Maya Mutul. Researchers found toxic levels of mercury and algae in four central reservoirs in Tikal, now in northern Guatemala.
„The transformation of Tikal’s central reservoirs from life-sustaining to disease-causing and death-causing would be a serious reason to abandon this magnificent city,“ the study said.
The geochemical analysis found that two reservoirs near the city palace and temple contained extremely high and toxic levels of mercury. Researchers have found that pollution comes from a pigment that the Mayans used to decorate buildings, pottery, and other goods. During rainstorms, the mercury in the pigment is washed away and drained into the tanks, where it settles to the bottom over the years.
„Archaeologists and anthropologists have been trying to understand what has happened to the Maya for 100 years,“ said David Lenz, a professor of biological sciences at the University of Cincinnati and lead author of the study.
Researchers took sediment samples from 10 reservoirs within the city and analyzed ancient DNA found in the stratified sediment of four of them.
This water, especially during droughts, would make people sick, even if the water was boiled, Lenz said.
„We found two species of blue-green algae that produce toxic chemicals. The bad thing about them is that they are resistant to boiling. This makes the water in these tanks toxic to drink, ”he says.
Researchers say it is possible, but unlikely, that the Mayans used these tanks for drinking, cooking, or irrigation. „The water would look bad and taste bad,“ said Kenneth Tankersley, an associate professor of anthropology at the University of Cincinnati College of Arts and Sciences.
„These big blue-green algae were in the water. No one would want to drink this water. „
Researchers have found lower but still toxic levels of mercury in sediments from more distant reservoirs called Perdido and Coriental, which would also provide drinking water for the city’s residents in the ninth century.
They believe that a combination of economic, political, and social factors has prompted people to leave the city and its surrounding farms. But climate no doubt also plays a role, Lenz said.
„There has been a long dry season. For part of the year, it was rainy and humid. The rest of the year is really dry and almost without precipitation. So they had a problem finding water. „
Researchers say a popular pigment used on plaster walls and in ceremonial burials is derived from cinnabar, a red mineral composed of mercuric sulfide that the Maya extracted from a nearby volcanic mountain known as the Todos Santos Formation.
Careful examination of the sediment of the tank using a technique called energy-dispersive fluorescence spectrometry revealed that this pigment was the source of mercury in the water.
The study is published in Scientific Reports.