英語聽力文摘 喜歡毒素的樹

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Toxin-loving Trees

樹木能調(diào)節(jié)氣候,保持生態(tài)平衡，樹木通過光合作用，吸進二氧化碳,吐出氧氣,使空氣清潔，新鮮。一畝樹林放出的氧氣夠65人呼吸一輩子。樹還能防風(fēng)固沙，涵養(yǎng)水土,吸收各種粉塵，一畝樹林一年可吸收各種粉塵20-60噸.。樹林也能夠減少噪音污染，40米寬的林帶可減弱噪音10-15分貝。噪音的污染對人類的生活、學(xué)習(xí)、工作、休息等方面都造成了很大的危害，可以說是人們的“敵人”。因此我們更要重視植樹造林。樹木的分泌物能殺死細菌。空地每立方米空氣中有3，4萬個細菌，森林里只有300-400個。植樹造林是我們每個公民的義務(wù)，國家還專門規(guī)定了在三月十二日這天為植樹節(jié)。植樹造林對我們的學(xué)習(xí)、工作、生活等方面都有很大的好處。樹可以減低溫度，和提高濕度30度氣溫可以降到二十幾度左右。

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.