The two pictures on the left show the effects of acid precipitation on sculptures. The picture on the left side was taken in 1908, while the picture on the right side was taken in 1969. Acid precipitation is the term used to refer to rain, snow, or fog with a pH more acidic than pH 5.6. It is predominantly caused by the presence in the atmosphere of sulfur oxides and nitrogen oxides, which react with water in the air to form strong acids. These acids then fall to earth in the form of rain or snow. Acid precipitation is a major environmental threat to living organisms because it damages wildlife, crops, and water environments. Acid precipitation also washes away certain mineral ions that ordinarily help buffer the soil solution and are vital nutrients to plant growth. However, we have made progress in reducing acid precipitation.
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