13 (b) To reduce the pollution, new water treatment works were built. Also PCBs which were used in the paper factories were banned. Scientists found that the pollution in Lake Malaren cleared fairly quickly. The effects of the pollution in Lake Vattern are taking much longer to disappear. Explain why this is taking longer. ................................................................................................................................................... ................................................................................................................................................... .............................................................................................................................................. [2] [Total: 5]
Š OCR 2014
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