Acid rain takes a toll on stone buildings and other structures including those that are culturally significant. Just as limestone and marble buffer acidic water, acid rain dissolves buildings and statues made of these materials. The decreased pH of rain and fog is taking its toll on cultural objects, a phenomenon that has long been recognized. In the same year that he coined the term acid rain (1856), Robert Angus Smith wrote, "It has often been observed that the stones and bricks of buildings, especially under projecting parts, crumble more readily in large towns where coal is burnt . . . I was led to attribute this effect to the slow but constant action of acid rain."
Much of the world's architectural heritage is under siege from acid rain. Affected buildings include Westminster Abbey and St. Paul's Cathedral in London; the Taj Mahal in India; the Coliseum in Rome; the Acropolis in Greece; Egypt's temples at Karnak; and monuments in Krakow, Poland. In Sweden, medieval stained glass windows are thought to have been damaged by acid rain. In the United States, limestone buildings, such as the U.S. Capitol, show some acid rain damage.
The effects of acid rain on a stone building and statue. (Adam Hart-Davis /Photo Researchers)
In most cases, acid rain does not act alone to diminish the beauty of these buildings.
In limestone buildings, the calcite mineral that makes up the stone reacts with sulfur dioxide pollutants and moisture in the air to form the mineral gypsum. This mineral grows into a network of thin crystals that traps particles of dirt. A dark crust forms on its surface, turning the building black. Since the gypsum crust dissolves in water, it accumulates in sheltered areas protected from rainfall. The result is that much of the detail carved into many old limestone buildings appears black and dirty.
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