El Tajín, a Totonac ruin in the municipality of Papantla, Veracruz, Mexico. Picture taken from the top of a pyramid. Photo © 2004 by Jacob Rus

Washington, Feb 20: Acid Rain is posing a threat to thousand year old precious stone carvings at one the Mexico’s most important archaeological sites.

The pre-Aztec city of El Tajin, located on Mexico's Gulf coast, is famous for its temple pyramids and intricately carved reliefs.

Built in what is now the state of Veracruz by the Totonac, a civilization that reached its peak from the early 9th to the early 13th century AD, much of El Tajin refers to one of the names for the Totonac god of thunder, and remains unexcavated.

The site's most famous building is an elaborate niche-studded pyramid. The ceremonial center also has a number of other temple pyramids, palaces, and courts for playing a ritual Mesoamerican ball game sometimes compared to basketball.

Experts say no other site has as many depictions of ball players and their equipment as the sculptures and carvings at El Tajin, whose inhabitants were apparently great fans of the game.

But acidic air pollutants pumped out by oil-drilling platforms and power stations along the coast is slowly eroding these carvings.

According to Humberto Bravo, an air pollution specialist at the University of Mexico's Centre for Atmospheric Sciences, the “deterioration is alarming and could cause irreparable damage to monuments that are an important part of Mexico’s cultural heritage".

He fears the hieroglyphics will completely disappear in a century or maybe even a decade if nothing is done to control the pollution.

"Within 10, 20, or 100 years, these hieroglyphics will disappear if we don't do anything about it," he said.

Bravo and his colleagues have spent several years simulating the effects of polluted air and acid rain on El Tajin's soft limestone buildings.

He has said the erosion is primarily due to contaminants like chlorine, sulphates and nitrates in the air from power stations and oil refineries.

Acid rain causes erosion on ancient monuments because the sulphuric and nitric acid chemically reacts with the calcium carbonate in the stones to create gypsum, which then flakes off.

Acid rain forms when pollutants in the air become trapped inside water droplets in a cloud. The pollution is then carried down to earth with the rain.

"The Veracruz region has some of the highest acid levels in the air in Mexico," National Geographic quoted Bravo as saying.

John Machado, a pre-Columbian art historian at Chaffey College in Rancho Cucamonga, California, has also expressed similar alarm at the detrimental effects of pollution on El Tajin.

"The art of El Tajin is crucial to our understanding of the ancient history of the Gulf coast. It gives evidence of a powerful and complex civilization that had broad interaction with Mesoamerican cultures in both central Mexico and Maya-controlled regions but still cultivated its own unique Veracruz style and iconography. The loss of these images would be devastating to the cultural heritage of the area," Machado said.

“But the problem of pollution affects archaeological sites throughout Mexico. The sources of degradation vary. Pollutants in the archaeological zone of Templo Mayor range from smog to water filtrations underground. We found that there had been a significant change in the rate of pollutants derived from sulfur, which had diminished considerably, compared to an increase in the quantity of chloride and heavy metal pollutants,” added Maria Lourdes Gallardo, chief conservator at the main Aztec temple, Templo Mayor, in Mexico City.

"I can document with 30 years of photographs just how acid rain is destroying those magnificent works of art. The details are slowly disappearing,” said David Grove, professor emeritus of anthropology at the University of Illinois at Urbana-Champaign, who has worked extensively at the site of Chalcatzingo in Morelos, 60 miles south of Mexico City.

The site is noted for its Olmec-style bas-relief carvings dating back to 700 B.C. in granodiorite, a rock much harder than limestone. (ANI)