Ancient Maya reservoirs contained toxic pollution

Picture: The ancient town of Tikal rises over the rainforest in northern Guatemala.
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Credit: David Lentz/UC

Reservoirs in the coronary heart of an ancient Maya town were so polluted with mercury and algae that the drinking water possible was undrinkable.

Scientists from the University of Cincinnati found poisonous ranges of pollution in two central reservoirs in Tikal, an ancient Maya town that dates back to the third century B.C. in what is now northern Guatemala.

UC’s results propose droughts in the ninth century possible contributed to the depopulation and eventual abandonment of the town.

“The conversion of Tikal’s central reservoirs from existence-sustaining to sickness-inducing sites would have equally virtually and symbolically aided to provide about the abandonment of this magnificent town,” the research concluded.

A geochemical assessment found that two reservoirs closest the town palace and temple contained poisonous ranges of mercury that UC scientists traced back to a pigment the Maya utilised to adorn structures, clayware and other goods. Throughout rainstorms, mercury in the pigment leached into the reservoirs where it settled in levels of sediment more than the many years.

But the former inhabitants of this town, manufactured well-known by its towering stone temples and architecture, had ample potable drinking water from nearby reservoirs that remained uncontaminated, UC scientists found.

The research was released in the Character journal Scientific Reviews.

UC’s diverse crew was composed of anthropologists, geographers, botanists, biologists and chemists. They examined levels of sediment relationship back to the ninth century when Tikal was a flourishing town.

Formerly, UC scientists found that the soils all-around Tikal throughout the ninth century were really fertile and traced the resource to recurrent volcanic eruptions that enriched the soil of the Yucatan Peninsula.

“Archaeologists and anthropologists have been hoping to figure out what transpired to the Maya for 100 many years,” mentioned David Lentz, a UC professor of organic sciences and direct author of the research.

For the hottest research, UC scientists sampled sediment at ten reservoirs inside the town and done an assessment on ancient DNA found in the stratified clay of four of them.

Sediment from the reservoirs closest Tikal’s central temple and palace showed evidence of poisonous algae known as cyanobacteria. Consuming this drinking water, especially throughout droughts, would have manufactured people today sick even if the drinking water were boiled, Lentz mentioned.

“We found two varieties of blue-eco-friendly algae that create poisonous chemical compounds. The lousy factor about these is they are resistant to boiling. It manufactured drinking water in these reservoirs poisonous to drink,” Lentz mentioned.

UC scientists mentioned it is probable but not likely the Maya utilised these reservoirs for drinking, cooking or irrigation.

“The drinking water would have seemed nasty. It would have tasted nasty,” mentioned Kenneth Tankersley, an associate professor of anthropology in UC’s Faculty of Arts and Sciences. “There would have been these huge algae blooms. No person would have needed to drink that drinking water.”

But scientists found no evidence of the exact same pollutants in sediments from extra distant reservoirs known as Perdido and Corriental, which possible offered drinking drinking water for town residents throughout the ninth century.

These days, Tikal is a nationwide park and a UNESCO Earth Heritage web page. Scientists feel a combination of financial, political and social components prompted people today to depart the town and its adjacent farms. But the weather no doubt performed a part, far too, Lentz mentioned.

“They have a extended dry year. For part of the year, it’s wet and moist. The relaxation of the year, it’s really dry with just about no rainfall. So they had a dilemma getting drinking water,” Lentz mentioned.

Co-author Trinity Hamilton, now an assistant professor of biology at the University of Minnesota, worked on the assessment of ancient DNA from algae that sank to the reservoir base and was buried by hundreds of years of accumulated sediment.

“Usually, when we see a whole lot of cyanobacteria in freshwater, we believe of unsafe algal blooms that affect drinking water high quality,” Hamilton mentioned.

Finding some reservoirs that were polluted and many others that were not indicates the ancient Maya utilised them for distinct uses, she mentioned.

Reservoirs around the temple and palace possible would have been amazing landmarks, a great deal like the reflecting pool at the Nationwide Shopping mall is right now.

“It would have been a magnificent sight to see these brightly painted structures reflected off the area of these reservoirs,” mentioned co-author Nicholas Dunning, head of geography in UC’s Faculty of Arts and Sciences.

“The Maya rulers conferred to by themselves, among other items, the attribute of remaining ready to regulate drinking water. They had a exclusive connection to the rain gods,” Dunning mentioned. “So the reservoir would have been a fairly strong image.”

UC’s Tankersley mentioned a single popular pigment utilised on plaster walls and in ceremonial burials was derived from cinnabar, a pink-coloured mineral composed of mercury sulfide that the Maya mined from a nearby volcanic aspect identified as the Todos Santos Formation.

A shut evaluation of the reservoir sediment working with a method known as electricity dispersive X-ray fluorescence spectrometry found that mercury did not leach into the drinking water from the fundamental bedrock. Furthermore, Tankersley mentioned, UC dominated out a further likely resource of mercury — volcanic ash that fell throughout Central The us throughout the recurrent eruptions. The absence of mercury in other nearby reservoirs where ash would have fallen dominated out volcanoes as the offender.

As an alternative, Tankersley mentioned, people today were to blame.

“That signifies the mercury has to be anthropogenic,” Tankersley mentioned.

With its shiny pink color, cinnabar was normally utilised as a paint or pigment throughout Central The us at the time.

“Color was essential in the ancient Maya earth. They utilised it in their murals. They painted the plaster pink. They utilised it in burials and merged it with iron oxide to get distinct shades,” Tankersley mentioned.

“We were ready to uncover a mineral fingerprint that showed over and above a sensible doubt that the mercury in the drinking water originated from cinnabar,” he mentioned.

Tankersley mentioned ancient Maya metropolitan areas these types of as Tikal continue on to captivate scientists simply because of the ingenuity, cooperation and sophistication necessary to prosper in this tropical land of extremes.

“When I appear at the ancient Maya, I see a really complex people today with a really prosperous culture,” Tankersley mentioned.

UC’s crew is organizing to return to the Yucatan Peninsula to go after extra solutions about this impressive time period of human civilization.