Sulfuric Acid's Effects on Limestone

Acid Rain

• Rainwater is naturally acidic. The naturally occurring sulfuric acid in rainwater comes from its reaction with volcanic gases. Rainfall in some areas of the world is now excessively acidic. According to Washington State University in St. Louis, in some parts of the U.S. rainwater is 1,000 times more acidic than normal. Acid rain is the result of atmospheric pollution. Sulfuric acid in rainwater forms when water reacts with the sulfur dioxide produced in the burning of sulfur-containing fossil fuels.

Limestone Buildings

• Acid rain erodes buildings made of limestone. When sulfuric acid comes into contact with limestone, the resulting chemical reaction breaks it down. The chemicals created in this reaction crystallize into a compound called gypsum. Gypsum dissolves in water and so washes away in areas that receive direct, heavy rainfall. In more sheltered areas, it accumulates and attracts dust and other airborne pollutants, and becomes stained black. Acid rain does not impact the structural integrity of buildings, but damages their appearance significantly.

Limestone Caves

• Groundwater is weakly acidic and over millenia it has eroded limestone deposits, forming many of the limestone caves around the world. According to the National Park Service, naturally occurring sulfuric acid caused the formation of the caves in the Guadalupe mountain range. Groundwater came into contact with oil deposits and ground-dwelling microbes, and the resulting acid ate away into cracks and fissures in the rock, enlarging and hollowing them out. As the water table fell, the erosion stopped and a new cave was left behind.

Limestone Soil

• Limestone soils are alkaline and unsuitable for growing plants that require neutral or acidic soils. According to Amy L. Shober and other scientists at the Gulf Coast Research and Education Center, it is impossible to reduce the alkalinity of limestone soils over a wide area or long-term. It is possible to have a temporary effect by adding horticultural sulfur according to manufacturers' guidelines. Soil bacteria change the sulfur into sulfuric acid, which then breaks down the limestone.