英语科普：蚯蚓能摄入土壤中的重金属
时间：2012-08-18 05:26:38
（单词翻译:单击）
Earthworms（蚯蚓） could be used to extract toxic1 heavy metals, including cadmium and lead, from solid waste from domestic refuse collection and waste from vegetable and flower markets, according to researchers writing in the International Journal of Environment and Waste Management. Swati Pattnaik and M. Vikram Reddy of the Department of Ecology and Environmental Sciences, at Pondicherry University, in Puducherry, India, explain how three species of earthworm, Eudrilus eugeniae, Eisenia fetida and Perionyx excavates2 can be used to assist in the composting of urban waste and to extract heavy metals, cadmium, copper3, lead, manganese, zinc4, prior to subsequent processing.
With rapid increases in urban populations particularly in the developing world, there is a growing problem of how to manage organic waste and to find alternatives to landfill disposal particularly for domestic food waste and that from vegetable markets. According to the research team, it is an unfortunate fact of life that much of this waste is currently dumped on the
outskirts5 of many towns and cities and is causing serious pollution, disease risk and general
ecological6 harm. It also represents a considerable wasted resource, whereas the organic matter might be exploited usefully in growing food crops.
The process of vermicomposting in this way allows such waste materials to be remediated and the compost used subsequently for use in growing human food without the risk of accumulating heavy metals in crops. The team says that up to about three-quarters of the various heavy metals can be removed by the worms from solid waste. The E. eugeniae species was the most effective worm at remediating solid waste and producing rich compost. The team's tests on vermicomposting reveal that the heavy metal content of such waste can be reduced to levels significantly below the
permissible7 safe limits.
The worms' digestive system is
apparently8 capable of detaching heavy metal ions from the complex
aggregates（总量，合体） between these ions and humic substances in the waste as it rots. Various enzyme-driven process then seem to lead to
assimilation（同化，吸收） of the metal ions by the worms so that they are locked up in the organism's tissues rather than being released back into the compost as worm casts. The separation of dead worms from compost is a
relatively9 straightforward10 process allowing the heavy metal to be removed from the organic waste.
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