Earth and Sky科普英語：Acid Rain 酸雨

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Damage from acid rain is widespread - not just in eastern North America, but throughout Europe, Japan, China, and Southeast Asia. Is the rain that's falling on your umbrella acidic? A listener's question -- on today's Earth and Sky.

JB: This is Earth and Sky with a question from Sandra Renee of Olive Hill, Kentucky. She asks, "How do you know when it rains that it's not acid rain, and what exactly is acid rain?"

DB: Sandra, you need a pH meter to reliably measure the acidity of rain or snow. But in certain parts of the US -- especially in the Northeast -- you can probably assume that most rain will be at least somewhat acidic. Westerly winds move pollutants eastward, so the eastern US gets more acid rain.

JB: Acid rain happens when airborne acids fall down to Earth in rain. Electrical utility plants that burn fossil fuels emit chemicals into the atmosphere that react with water and other chemicals in the air to form sulfuric acid, nitric acid -- the "acid" in acid rain. You don't have to live next door to a plant to get showered by acid rain. These acid pollutants reach high into the atmosphere and can travel with wind currents for hundreds of kilometers.

DB: The acids in acid rain are corrosive chemicals that leach nutrients from the soils, slow the growth of trees, poison lakes and combine with other chemicals to form urban smog. The simplest way to curtail acid rain is to use less energy from fossil fuels.

JB: Special thanks today to the Camille & Henry Dreyfus Foundation, a private foundation dedicated to advancing research and education in the chemical sciences. We're Block and Byrd for Earth and Sky.