Gauging the economic impact of the crisis is as difficult as predicting when and where the next cloud of ash will appear.

测量这次危机带来的经济影响如同预测下一次火山灰何时何地出现一样困难。

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Experts stressed that the ash, in tiny particles and difficult to detect, was no danger to public health but posed a distinct danger to aircraft.

专家们强调，微小颗粒的灰尘不易察觉，是不会危害公众健康危险，但是极易对飞机构成威胁。

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If the image had been taken later in the year, when snow covers the entire peninsula, the ash plume would be difficult to see against a white background.

如果晚些时候拍摄，到积雪覆盖整座火山之后，火山烟流将在白色背景下难以看到。

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In winter of course healthy and sick ash trees are difficult to tell apart as the leaves will all have fallen to the ground.

BBC: The heartbreak of watching the slow death of ash trees

Modern industry produces many things, from coal ash to computers, that are difficult to dispose of properly.

ECONOMIST: The waste industry

Gauging the economic impact of the crisis is as difficult as predicting when and where the next cloud of ash will appear.

ECONOMIST: The effect on business and leisure