Global warming may release frozen pollutants
Melting glaciers in the Alps may cause severe environmental damage due to the release of pollutants which have been frozen in ice for decades, according to research by Swiss scientists. With glaciers predicted to recede further due to global warming, the resulting melt may contain chemicals which have been banned or are not widely produced any more. Researchers from the Swiss Federal Institute of Technology Zurich, the Swiss Federal Laboratories for Materials Testing and Research (EMPA) and the Swiss Federal Institute of Aquatic Science and Technology (EAWAG) analysed sediment layers from the high-Alpine Oberaarsee reservoir in Switzerland. The scientists were able to reconstruct the processes by which long-lived organic compounds have accumulated in the ice over the last 60 years, and published their findings in the journal Environmental Science and Technology. These compounds are called 'legacy pollutants', and researchers found that accelerated glacier melting may account for increased levels of such chemicals in Alpine regions. The presence of legacy pollutants in the Alps is dangerous for several reasons, including the melting of snow in the spring, use of glacier melt water by consumers and industry, and increased specific exposure of humans and wildlife to hazardous compounds. 'Considering ongoing global warming and accelerated massive glacier melting predicted for the future, our study indicates the potential for dire environmental impacts due to pollutants delivered into pristine environments,' warned the researchers. When glaciers melt, the accumulated chemicals, deposited years earlier by air currents on to the snow layer and then frozen into the ice, are carried by the runoff water into the nearest glacial lake. There, together with other matter suspended in the melt water, they sink to the bottom of the lake and accumulate in the sediment. Researchers looked for a wide range of pollutants, including persistent organic pollutants, organochlorine pesticides and synthetic musk fragrances. The researchers were able to read the sediment layers in the Oberaarsee reservoir's sediment samples like tree rings, layer for layer all the way back to 1953, when the dam which created the lake was first built. Reading the rings, the scientists were not only able to distinguish pollutants produced in the 1960s and 1970s, but also see the reduction in chemicals after they were banned. Alarmingly, though, increased pollutant levels were visible from the 1990s. The researchers say that this may be due, in part, to runoff from the Oberaar glacier, which shrank by 120 metres in the last 10 years alone, and could have released a relatively large amount of accumulated toxic substances. Samples from Lake Oberaar were compared to core samples from lakes at lower levels. Sediment from these locations did not exhibit the same increase in legacy pollutants at the end of the 1990s. This finding supported the hypothesis that the increased levels of legacy pollutants in Lake Oberaar resulted from glacier melt. The study concludes by saying: 'The coupling of glacier dynamics and pollutant cycling is a complex topic and represents a poorly studied research field. Ongoing work in this field may provide additional insight into the fate of persistent organic pollutants in the Alpine environment.'
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