Toxic threat to quake survivors

Toxic chemicals and heavy rain have added to the threat faced from "quake lakes" in danger of bursting their banks in China.

About 5,000 tonnes of chemicals, including sulphuric and hydrochloric acid, are trapped downstream from the Tangjiashan lake and have to be moved to safe ground, reports said.

The chemicals, adding pollution to the threat of flooding, are stranded in different work sites downstream from the lake.

Tangjiashan lake was created when landslides blocked the Jianjiang river above the town and county of Beichuan in mountainous Sichuan province, near the quake epicentre.

The Finance Ministry illustrated this sense of urgency by announcing an extra £73.1 million to be spent on relief work on an estimated 35 quake lakes.

This is on top of the £29.2 million already alloted to work on smaller damaged dams.

China has evacuated more than 150,000 people living below the swollen Tangjiashan lake amid fears it could burst and trigger massive flooding.

The official death toll from the 7.9-magnitude quake on May 12 is already more than 68,000 and is certain to rise further, with nearly 20,000 listed as missing.

Heavy rain at the site has hampered efforts by more than 600 soldiers to open a giant sluice to discharge floodwaters, and helicopters shipping in equipment have been unable to take off.

Some 1,000 People's Liberation Army soldiers were making their way by foot to the lake, carrying more than ten tonnes of diesel for bulldozers already there.

Alexander Densmore, a seismologist at Durham University, said any break in a quake lake is likely to be sudden.

He said: "It's a very real problem. These landslide dams pose a really significant risk in these mountain regions, and in these narrow valleys it doesn't take much material to create a complete blockage."

Once a breach occurred, there could be an accelerating process leading to a sudden rush of water downstream.

"Once that process starts, it's virtually impossible to do anything to decrease the water... When they (quake dams) fail, they tend to fail catastrophically," he said.

A massive relief effort, which involves providing food, tents and clothing for millions and the reconstruction of housing and infrastructure, including the many destroyed schools, is expected to take up to three years.

Education officials in Wenchuan county, the epicentre, are pressing neighbouring school authorities to accept more of the county's 14,000 children who have no schools to go to.

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