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Bitter legacy

发布时间:2019-03-08 01:03:02来源:未知点击:

By Liz Tynan in Sydney ACID waste could leak from scores of mines in Australia, a new report claims. It warns that the mining industry’s practice of burying its waste is ineffective. A team led by John Harries of the Australian Nuclear Science and Technology Organisation in Sydney looked at 317 active and abandoned mines across the country. It found that 54 of them contained significant amounts of waste that could lead to acid contamination. A further 62 mines with smaller amounts of waste were also a cause for concern. The survey was funded by the Department of Environment. Opencast and underground mining often exposes large amounts of pyrite and other sulphide minerals to the air, which accelerates their oxidation. Once oxidised to sulphates, they will form an acid in water that can severely damage plant and animal life if it leaks from a mine. “In some areas it is [already] impossible for any aquatic life to live in rivers,” says Harries. The usual method of dealing with such waste is simply to bury it under soil and rocks, and grow vegetation on top. But according to team member Graham Taylor of the CSIRO, the Australian national research organisation, that is not a long-term solution. He warns that rainfall can easily wash the acid into the environment, and that it can bring with it dissolved heavy metals. The scientists found most of the problems at abandoned mines, including an old uranium mine at Rum Jungle in the Northern Territory and a zinc, lead, copper and gold mine at Captains Flat near Canberra. Taylor says that the risk would be significantly reduced if waste were properly treated while mines were still active. Rehabilitating abandoned sites costs at least A$100 000 (£38 000) per hectare, whereas the cost at active mines is about a third of that. Canada deals with the problem of acid wastes by placing them at the bottom of freshwater lakes, where they cannot be oxidised. That option is not available in Australia,