What an Arctic ‘chemical bank’ reveals about global pollution
While essential to modern life, industrial chemicals accumulate in organisms, presenting a health hazard; and both their variety and use are growing. “While between 1965 and 2015 the number of disclosed substances increased to 100 million, another 30 million were registered in the following two years alone. And the estimate that chemical pollution caused 1.6 million deaths in 2016 is probably an underestimate, as only a small fraction have been adequately tested for safety,” Anna Sobek(opens in new window) from Stockholm University says. Sobek is the coordinator of the Marie Skłodowska-Curie Actions(opens in new window) ARCHEM project set up to identify chemicals posing a global threat, by studying Arctic Ocean sediments (debris from living organisms and soil particles from coastal erosion and riverine inputs). As risk assessments don’t keep abreast of new chemicals, it remains largely unknown which should be prioritised for regulation. However, a chemical detected in the Arctic will have been emitted in large volumes elsewhere and has the capacity to disperse globally, indicating that it should be controlled.
Detecting a previously unidentified global threat
ARCHEM improved upon previous Arctic chemicals screening efforts which used low-resolution mass spectrometry and detected only known target pollutants. To enable non-target screening, ARCHEM used state-of-the-art ion mobility–high resolution mass spectrometry(opens in new window) (HRMS), with thousands of organic compounds digitalised. “This was like going from dinner with chopsticks – where you first decide what to pick up, then pick up one thing at a time – to a spoon,” explains Xiaodi Shi, principal investigator from Stockholm University, the project host. HRMS provided information about both the abundance and structure of compounds, “a bit like a pollutant fingerprint,” remarks Shi. These fingerprints were cross-referenced with pollutants databases. ARCHEM studied surface sediment in the Eurasian Arctic shelves, held by Stockholm University, alongside Canadian marine surface sediment and Canadian high Arctic lake sediment cores, and Antarctic marine surface sediment. “We detected about 150 pollutants in the Arctic sediments. One of the most interesting of previously unknown pollutants identified was fluorotelomer methyl sulfones, a class of non-polar per- and polyfluoroalkyl substances (PFASs). “We are working to determine their source; they could be by-products or degradation products of PFAS surfactants. They were also detected in sediments from the United States, the Baltic Sea and a Norwegian lake, highlighting their overlooked global threat,” explains Shi.
Uncovering a key constraint of pollutants distribution
In marine systems, many chemicals avoid water and concentrate in natural organic matter (OM), meaning their distribution is intertwined with OM’s natural characteristics, complicating the modelling of pollutant distribution and accumulation. To overcome this, ARCHEM analysed the weight of the carbon atoms in the sediment samples – derived from the open-science Circum-Arctic Sediment CArbon DatabasE(opens in new window) – to disentangle the sources of the OM – marine or soil – to study how that influences pollutant accumulation. “This is the first large-scale quantitative field test of factors controlling pollutants accumulation in marine systems,” adds Sobek. The team found that marine OM is about 10 times better at binding pollutants, suggesting it as a strong driver of pollutant accumulation. “Knowing that different OM has different binding potential, and that climate change will change the volume and sources of OM, suggests a future change in the distribution of pollutants,” notes Shi. In 2020, the European Commission published a ‘chemicals strategy for sustainability’(opens in new window) for a toxic-free environment. The associated legislative package includes both a new common data platform, and a monitoring and outlook framework. ARCHEM’s work substantively contributes to both. “While we investigated over 100 pollutants, this is less than 10 % of the available data. Big-data techniques will help us mine the remaining data,” adds Shi.
