Mop it up

日期:2017-06-19 06:08:08 作者:缑屁韪 阅读:

By Lila Guterman MUCUS secreted by freshwater snails and other creatures might one day clean up aluminium pollution in rivers and lakes, say British researchers. The method might also work for other metal pollutants. A major cause of aluminium pollution is acid rain, which makes aluminium compounds soluble and leaches the ions out of rocks and soils into standing waters and watercourses. High concentrations of aluminium ions can be deadly. “Fish are dying in acid waters, but elevated levels are [also] toxic to other aquatic organisms, from algae and plants to birds,” says Jonathan Powell, a chemist at St Thomas’s Hospital in London. Powell knew that mucus in the human intestine grabs toxic metal ions so that they can be excreted and wondered if mucus from other organisms does the same thing. He teamed up with experts on the freshwater snail Lymnaea stagnalis at the University of Manchester to see if the snail’s mucus also pulls metal ions out of water. They found that snails can significantly reduce aluminium levels in water. After 10 snails had spent 48 hours in a bucket of water containing very high levels of aluminium, its concentration fell by more than 80 per cent. Only a fraction of the lost aluminium ended up in the snails’ bodies, the researchers report in Environmental Science & Technology (vol 32, p 2591). The team believe the rest was bound to the mucus in the bottom of the bucket and on its walls. Snail mucus alone, which consists mainly of glycoproteins, also reduced aluminium concentrations. But bacteria and algae secrete far more mucus than snails, Powell says, so they could already play a key role in removing metal from rivers. Keith White, one of the biologists at the University of Manchester says aluminium could be removed from polluted waters by growing films of mucus on gravel that could be placed in the water. But Charles Driscoll, an environmental engineer at Syracuse University in New York says lab work may not reflect reality. “I think the environmental significance hinges on the relative contribution that these snails or other organisms that produce [mucus] would have in water bodies,