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Spring clean

it is well established that titanium dioxide, a chemical, can catalyse the breakdown of organic molecules in the presence of sunlight. This property has been exploited for many purposes, including manufacture of self-cleansing windows: when spread onto a pane of glass, the chemical chews up grease and helps dirt to slide away.

Now, a researcher in Britain has built a prototype water cleaning system that injects the chemical into a fountain. Gianluca Li Puma at the University of Nottingham, the uk, has designed the fountain in such a manner that it produces an umbrella-shaped film of water to maximise the surface area for sunlight to act upon. Li Puma says the fountain is as cheap and effective as the lumps of carbon currently used to soak up organic pollutants. And because his process degrades the pollutants into harmless compounds rather than simply absorbing them, it leaves no toxic residues. "The technique would also make the fountains look much more pretty,' he laughingly tells.

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