Acid Rain Destroying Mexico’s Cultural Heritage

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MEXICO CITY – Acid rain, caused by pollutants being dumped into the atmosphere by humans every day, is destroying the cultural heritage of Mexico’s Maya civilization, biologist Pablo Sanchez told EFE.

Ancient Maya structures and monuments were built of limestone, which is mainly composed of calcium carbonate, which dissolves when it comes into contact with acid rain, eroding the inscriptions.

“We could lose all of the inscriptions and writing on stelas and columns within 100 years,” said the scientist, who is on the faculty of the Center for Atmospheric Sciences at the National Autonomous University of Mexico (UNAM).

Solving the problem will not be easy, he said, as conservators are unsure how to protect the structures, particularly the “lintels and stelas which have been increasingly affected” by acid rain.

Limestone “cannot be covered by a protective layer since these rocks need to breathe, absorbing humidity and water, so a sealant would only accelerate their deterioration,” Sanchez said.

Given that, conservation experts are researching how a protective layer could be applied to monuments so as not to impede gas exchanges through the rock. Rain is considered to be acid when its pH is less than 5.6. This happens “when pollutants such as sulfur oxide and nitrogen oxide are incorporated” into the rain, Sanchez said.

Pollutants derived from petroleum are a major source of these compounds, “which, because of their chemical nature, react with a cloud’s humidity and create acid rain.”

The phenomenon cannot be easily contained because pollutants can be released thousands of miles from where the rain actually takes place.

This means that acid rain in Mexico could be due to pollutants being released as far away as Cuba or Venezuela, the scientist said. – BERNAMA