Getting down to it

14/09/1996
Down To Earth

the best way to ascertain whether or not manufacturers are complying with pollution laws related to toxic hazardous metals, is to monitor what comes out of their smokestacks. Till now, scientists have been periodically monitoring emissions by studying samples from these factories in their laboratories. A study at source is considered difficult due to the harsh environment of the average smokestack which precludes the use of delicate equipment needed to record the emissions. But the situation is now likely to change, thanks to the efforts of a scientist at the Massachusetts Institute of Technology ( mit ), Paul Woskov.

His method entails the use of microwaves to create a small cloud of hot ionised gas called plasma inside the smokestack. When the emissions pass through the plasma, it converts metals such as lead and chromium into their constituent atoms. Free electrons in the plasma collide with these, causing them to emit light which is picked up by an optical fibre and fed into a spectrophotometer. The spectrophotometer helps scientists see the spectrum through which they can identify the constituents of the emissions such as lead, mercury, arsenic, beryllium and other poisonous chemicals. "Like a fingerprint, each element has its own spectrum,' explains Woskov.

During the tests

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