英语听力文摘 喜欢毒素的树
Toxin-loving Trees
树木能调节气候,保持生态平衡，树木通过光合作用，吸进二氧化碳,吐出氧气,使空气清洁，新鲜。一亩树林放出的氧气够65人呼吸一辈子。树还能防风固沙，涵养水土,吸收各种粉尘，一亩树林一年可吸收各种粉尘20-60吨.。树林也能够减少噪音污染，40米宽的林带可减弱噪音10-15分贝。噪音的污染对人类的生活、学习、工作、休息等方面都造成了很大的危害，可以说是人们的“敌人”。因此我们更要重视植树造林。树木的分泌物能杀死细菌。空地每立方米空气中有3，4万个细菌，森林里只有300-400个。植树造林是我们每个公民的义务，国家还专门规定了在三月十二日这天为植树节。植树造林对我们的学习、工作、生活等方面都有很大的好处。树可以减低温度，和提高湿度30度气温可以降到二十几度左右。
In our increasingly complex age of high technology and instant electronic communication, it’s important to recall a few simple truths. Forexample–trees are good. Think about it trees help hold soil in place, create oxygen, and provide shade on hot summer days. And now, thanks to researchers at the University of Georgia, trees may soon help us clean up toxic waste.
Here’s how it works. Scientists isolated a gene from a type of bacteria that thrives in places polluted by mercury–a metal that is highly toxic in large amounts.
They then implanted the gene, which converts mercury into a less-toxic form, into day-old saplings. Once the genetically engineered trees were big enough, they were transplanted to soil contaminated by mercury. When tested against regular trees, the genetically enhanced trees were able to absorb and dilute ten times more mercury, which they released into the air as harmless vapor. In fact, the trees seemed to thrive on mercury. When grown in soil lacking the toxin, the trees became weak and sickly.
Mercury pollution is a serious threat to wildlife and to humans. Eating fish that have ingested large amounts of mercury, for example, can cause neurological damage in humans. Cleaning up soil and water polluted by mercury is typically very expensive, which makes mercury absorbing trees an even more attractive prospect. Trees are relatively cheap to grow and plant, and scientists hope to engineer trees to absorb other toxins besides mercury.
It remains to be seen how well the trees will function on a wider scale. But if they are able to help decontaminate our soil and water, we’ll have even more reason to appreciate toxin-loving trees.
- 频道推荐
- |
- 全站推荐
- 推荐下载
- 网站推荐
