Air pollution is one of the most pervasive environmental
problems because atmospheric currents can carry contaminated air to every
part of the globe. Most air pollution comes, from automobile emissions and
from power plants what burn coal and oil to produce energy for industrial and
consumer use. 62. ______ Carbon dioxide and
other harmful gases releasing into the air from these
63. ______ sources adversely effect weather patterns and the
health of people, animals and 64. ______ plants.
Industrialized nations produce most of the world’s air pollution. For
65. ______ example, because the United
States is home to just 5 percent of the world’s population, the country
generates 22 percent of human-made carbon dioxide
66. ______ emissions or 19 percent of all greenhouse gases such as
carbon dioxide and 67. ______ methane. These
emissions harm the environment by leading acid rain and global warming, and
by depleting (使衰竭) the protective ozone layer which
68. ______ surround the earth. Acid rain, a serious threat
around the world, occurs when sulfur dioxide and nitrogen oxide emissions
from automobiles and fossil-fuel burning power 69.
______ plants to fall back to Earth as acidic precipitation. Acid rain has
contaminated many lakes in Canada and the northeast United States and has
been documented even in the non-industrial state of Hawaii. In the United
70. ______ Kingdom, 57
percent of all trees are severely defoliated (使落叶) owe to
71. ______ corrosive fallout, and production of food crops has
been declined in many parts of the world. Acid rain has eroded the surfaces
of great art and architectural treasures, including the ancient sculptures of
Rome and the Sphinx in Egypt.