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Acid rain |
Today I’m going to talk about: Acid rain I’ve divided my presentation into two parts: First I’d like to introduce of acid rain and second I’ll say same effects of acid rain. So, let’s start with introduce Acid Rain, form of air pollution in which airborne acids produced by electric utility plants and other sources fall to Earth in distant regions. The corrosive nature of acid rain causes widespread damage to the environment. The problem begins with the production of sulfur dioxide and nitrogen oxides ffrom the burning of fossil fuels, such as coal, natural gas, and oil, and from certain kinds of manufacturing. Sulfur dioxide and nitrogen oxides react with water and other chemicals in the air to form sulfuric acid, nitric acid, and other pollutants. These acid pollutants reach high into the atmosphere, travel with the wind for hundreds of miles, and eventually return to the ground by way of rain, snow, or fog, and as invisible “dry” forms. Finally let’s consider: with effects of acid rain Acidic substances hhave pH numbers from 1 to 6—the lower the pH number, the stronger, or more corrosive, the substance. A Soil. In soil, acid rain dissolves and washes away nutrients needed by plants. It can also dissolve toxic substances, such as aluminum and mercury, wwhich are naturally present in some soils, freeing these toxins to pollute water or to poison plants that absorb them. Some soils are quite alkaline and can neutralize acid deposition indefinitely; others, especially thin mountain soils derived from granite or gneiss, buffer acid only briefly. B Trees Forest Damaged by Acid Rain Forests, lakes, ponds, and other terrestrial and aquatic environments throughout the world are being severely damaged by the effects of acid rain. Acid rain is caused by the combination of sulfur dioxide and nitrogen compounds with water in the atmosphere. In addition to chemically burning the leaves of plants, acid rain poisons lake water, killing most, if not all, the aquatic inhabitants. C Agriculture Most farm crops are less affected by acid rain than are forests. The deep soils of many farm regions, such as those in the Midwestern United States, can absorb and neutralize large amounts of acid. Mountain farms are more at risk—the thin soils in these higher elevations cannot neutralize so much acid. Farmers can prevent acid rain damage by monitoring the condition of the soil and, when necessary, adding crushed limestone to the soil to neutralize acid. If excessive amounts of nutrients have been leached out of the soil, farmers can replace them by adding nutrient-rich fertilizer. D Plants and Animals TThe effects of acid rain on wildlife can be far- reaching. If a population of one plant or animal is adversely affected by acid rain, animals that feed on that organism may also suffer. Ultimately, an entire ecosystem may become endangered. Some species that live in water are very sensitive to acidity, some less so. Freshwater clams and mayfly young, for instance, begin dying when the water pH reaches 6.0. Frogs can generally survive more acidic water, but if their supply of mayflies is destroyed by acid rain, frog populations may also decline. Fish eggs of most species stop hatching at a pH of 5.0. Below a pH of 4.5, water is nearly sterile, unable to support any wildlife. |
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· 1970.01.01 05:00
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