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SSS 2009-11-16

时间:2010-05-19 03:07来源:互联网 提供网友:mark@li   字体: [ ]
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    (单词翻译:双击或拖选)

It seemed like a good idea—because rivers and ponds in Bangladesh were contaminated with bacteria, Bangladeshis switched to wells. But soon after, in the early ‘80s, researchers realized those wells were harming Bangladeshis with a new poison—arsenic1.

 

The underground sediment2 of the Ganges Delta3 contains arsenic. In 2002 M.I.T. researchers determined4 that microbes digesting organic carbon were freeing that trapped arsenic. But where did the carbon come from and how was the arsenic getting into the water supply? The M.I.T. team now thinks they have the answers, which they report in the journal Nature Geoscience.

 

Using a six-square-mile test plot, they found that the organic carbon comes from shallow ponds that were dug to provide soil for flood protection. The carbon compounds sink in the pondwater and seep5 underground where bacteria digest them, setting up the perfect chemical conditions to free up the soil’s arsenic. Groundwater flow then brings the arsenic-rich water to the wells.

 

Future wells dug deep enough, to the low-arsenic part of the aquifer6, could help. Rice fields filter arsenic from the water, so wells under those fields could also be part of an answer to a problem affecting millions of Bangladeshis.

 

—Cynthia Graber
 


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1 arsenic 2vSz4     
n.砒霜,砷;adj.砷的
参考例句:
  • His wife poisoned him with arsenic.他的妻子用砒霜把他毒死了。
  • Arsenic is a poison.砒霜是毒药。
2 sediment IsByK     
n.沉淀,沉渣,沉积(物)
参考例句:
  • The sediment settled and the water was clear.杂质沉淀后,水变清了。
  • Sediment begins to choke the channel's opening.沉积物开始淤塞河道口。
3 delta gxvxZ     
n.(流的)角洲
参考例句:
  • He has been to the delta of the Nile.他曾去过尼罗河三角洲。
  • The Nile divides at its mouth and forms a delta.尼罗河在河口分岔,形成了一个三角洲。
4 determined duszmP     
adj.坚定的;有决心的
参考例句:
  • I have determined on going to Tibet after graduation.我已决定毕业后去西藏。
  • He determined to view the rooms behind the office.他决定查看一下办公室后面的房间。
5 seep rDSzK     
v.渗出,渗漏;n.渗漏,小泉,水(油)坑
参考例句:
  • My anger began to seep away.我的怒火开始消下去了。
  • If meteoric water does not evaporate or run overland,it may seep directly into the ground.如果雨水不从陆地蒸发和流走的话,就可能直接渗入地下。
6 aquifer iNayl     
n.含水土层
参考例句:
  • An aquifer is a water-bearing rock stratum such as sandstone and chalk.地下蓄水层是一些有水的岩石层,如沙岩和白垩岩。
  • The wine region's first water came from an ancient aquifer.用来灌溉这个地区葡萄园的第一批水来自古老的地下蓄水层。
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