2. 外语
  3. Only recently have investigators considered using these plants to clean up soil and waste sites that have been contaminated by t

Only recently have investigators considered using these plants to clean up soil and waste sites that have been contaminated by t

admin2014-09-29  58
问题     Only recently have investigators considered using these plants to clean up soil and waste sites that have been contaminated by toxic levels of heavy metals—an environmentally friendly approach known as phytoremediation. This scenario begins with the planting of hyperaccumulating species in the target area, such as an abandoned mine or an irrigation pond contaminated by runoff. Toxic minerals would first be absorbed by roots but later relocated to the stem and leaves. A harvest of the shoots would remove the toxic compounds off site to be burned or composted to recover the metal for industrial uses. After several years of cultivation and harvest, the site would be restored at a cost much lower than the price of excavation and reburial, the standard practice for remediation of contaminated soils. For example, in field trials, the plant alpine pennycress removed zinc and cadmium from soils near a zinc smelter, and Indian mustard, native to Pakistan and India, has been effective in reducing levels of selenium salts by 50 percent in contaminated soils.
Why does the author mention "Indian mustard"?
选项 A、To warn about possible risks involved in phytoremediation
B、To help illustrate the potential of phytoremediation
C、To show that hyperaccumulating plants grow in many regions of the world
D、To explain how zinc contamination can be reduced
答案B
解析
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