A unique study of persistent organic pollutants in the frozen Tibetan Plateau was a leading journal’s most read paper of 2014
Analysis of frozen ice cores from the Tibetan Himalayas show that international agreements on phasing out the use of toxic persistent organic pollutants are working.
The research paper in the leading American Chemical Society journal, Environmental Science & Technology, has been downloaded more than 19,600 times since it was published in January 2014.
Lancaster University scientists worked with colleagues from China and Germany to collect and analyse samples from ice cores which had been laid down over 30 years, to show how residues of Perfluoroalkyl substances (PFASs) in the environment have changed over time.
“PFASs are used in many everyday products such as fabric linings, non stick pans and fire fighting foams,” said Dr Crispin Halsall from the Lancaster Environment Centre
“They are very persistent in the environment and some can bioaccumulate. Many of these compounds are thought to be toxic to humans: a recent study has shown very strong evidence that one, PFOA, retards human fetal growth.
“Chemical residues are carried thousands of miles on the prevailing winds and deposited in the ice. Ice cores are very effective barometers of pollution over time as ice is laid down over the decades. We wanted to see whether the level and type of these chemicals in the cores had changed over time.”
It is much cheaper to test ice cores, which capture years of data in one core, than to do repeated air sampling over time. There are also advantages in testing in remote regions, far away from pollution sources, because samples are not distorted by local activities, and so the results provide a global picture.
The successful research project started out of a chance meeting in 2010, when Dr Xiaoping Wang, from the Institute of Tibetan Plateau Research, was visiting the Lancaster Environment Centre. Chatting to Crispin’s PhD student Garry Codling over a cup of tea, she realised he could help her with a research problem: how to extract and transport samples from frozen ice cores that her institute had collected over the previous year. Garry had developed a portable chemical extraction kit for use in the Arctic, where he was doing his PhD research. With Crispin’s encouragement, he agreed to loan Xiaoping the equipment and to travel to Tibet to operate it.
“We’d failed to take account that the Asian Games were happening that year, and the equipment was held up by customs in Hong Kong for months. When it arrived Garry had to work very long hours over Christmas and New Year to get the work done in time. The samples were then transported to a lab in Germany for analysis.”
The ice cores came from two sites: one on the eastern end of the Plateau where the prevailing wind comes from Asia, and the other on the western end with prevailing winds from Europe.
The results when they came through were fascinating: reflecting changes in policy and production of these chemicals in the different regions over time.
On the western side the ice cores showed deposits of PFASs initially increasing as they were used more and more in European industry, and then decreasing as industrial output changed. One of these compounds is classed as a persistent organic pollutant under the United Nations Environmental Programme (UNEP) Stockholm Convention. Industry has agreed, largely voluntarily, to phase out some of these compounds.
On the eastern side the level of residues is still increasing as Asia becomes more industrialised, but the nature of the PFASs are changing.
“Some of the long carbon chain compounds are particularly toxic and industry has responded by producing shorter chain compounds, and we are starting to see that in the ice cores. Good practice in industry is having an impact,” Crispin said.
“It provides the evidence that you can change things and reduce the prevalence of toxic chemicals through consensus and an international framework. That is very encouraging.
“I think the paper is so popular because it highlights that remote environments like The Tibetan Plateau can act as a barometer for assessing changes to global industrial output of these chemicals.”