Science: Tracing the Thames

Britain's Hydraulic Research Board (concerned with rivers, harbors and beaches) has been using radioactive tracers to keep track of the mud of the Thames. At present, the Port of London Authority keeps a fleet of dredges at work on the channel at an annual cost of nearly $2,000,000, and it suspects that a lot of the mud they dredge is washed back up the river by the rising tides. If it could be sure, the Authority figured, it might train the tides of the Thames to carry more mud out to sea.

Asked for help, Britain's Atomic Energy Research Establishment at Harwell cooked up some glass spiked with radioactive scandium and ground it down until its particles were the same size as the Thames silt. Two drums of the hot stuff were dumped by derrick on the bottom of the Thames. Then scientists armed with Geiger counters traced the movement of the radioactive particles. Some of them were found eleven miles upstream, confirming the worst suspicions of the Port of London Authority.

The operation was a pilot program to see if the method would work. This summer the Authority engineers will dose the river more liberally to trace the travels of its silt. Meanwhile, the Hydraulic Research Establishment is trying radioactive scandium-glass on Britain's beaches to find out how they get eroded away.