Glaciers melting due to the effects of global warming have become a secondary source of banned pollutants and free chemicals.
|Researchers drilling the core for samples|
Persistent organic pollutants – or POPs – which have accumulated on snow surface and frozen, are carried off by runoff water from melting glaciers to the nearest lake. They then sink, along with other matter in the melt water, and accumulate in the sediment. Researchers from Empa, the ETH Zurich and Eawag have analysed these sediment layers in Oberaarsee, an artificial reservoir in the Bernese Oberland.
“Based on our analysis of the layers we were able to confirm that POPs were being produced in large quantities from 1960 to 1970 and deposited in alpine lakes,” said Christian Bogdal, who completed a doctoral thesis on polluting effects of organic chemicals at Empa, and now conducts research in this field at EZH Zurich.
The cores showed a reduction in the quantity of pollutants in the early 1970s when they were banned. There was also a renewed increase in POP concentrations in sediment layers which were ten to 15 years old, according to Bogdal. Chlorine-containing chemicals found in the layers from the end of the 1990 were sometimes higher than those seen in the 1960s and 1970s. The lake is fed from runoff from the Oberaar glacier – which has shrunk by more than 120m in the last ten years and could have released a relatively large amount of accumulated toxin substances.
Sedimentologists from Eawag extracted drill samples of sediment which were
|The drill core from the Oberaarsee tells a story which goes back 50 years|
analysed in the laboratory at Empa. Researchers read the sediment layers like tree rings, layer for layer back to 1953 when the dam creating the lake was built. Their findings have been published in Environmental Science and Technology.
POPs are banned organic environmental pollutions – plasticisers, pesticides and dioxins – are endocrine disruptors and are carcinogenic, and are suspected of interfering with human and animal development. They are long-lived and can be transported through the atmosphere.
The team are hoping to further their research by investigating how POPs accumulate in glaciers, the paths they follow within them and the chemical changes they undergo, if any, when exposed to UV light.