SSS 2009-11-16
时间：2019-01-08 作者：英语课 分类：Scientific American(十一)月
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—arsenic 1.
The underground sediment 2 of the Ganges Delta 3 contains arsenic. In 2002 M.I.T. researchers determined 4 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 seep 5 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 aquifer 6, 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
- 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。
- 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。
- 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。
- 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。