Dust travels from the Sahara and paints skies across Europe
Every year, a hazy veil from the Sahara turns the sky orange, a spectacle that also carries consequences. The drifting dust can curb solar energy generation by reducing sunlight reaching panels and it may irritate lungs, posing health risks for people with respiratory conditions. Importantly, the dust contains radioactive elements that accumulate in parts of Europe, including Spain, according to a recent study by a team of scientists.
Europe witnessed a striking dust event in February 2021, an episode that offered scientists a chance to involve residents in a citizen science effort. People in snowbound regions, such as the Pyrenees, were invited to collect snow samples for dust analysis. The study coordinator was Marie Dumont, affiliated with France’s National Meteorological Research Centre.
Volunteers helped gather 10 by 10 centimeter snow samples across the dust-covered areas of the Pyrenees and the European Alps, largely in France and Switzerland, from sea level up to 2,500 meters. The samples were melted, sent to laboratories in Toulouse and Grenoble, and then filtered and dried for dust particle analysis.
Researchers reported the results in Earth System Science Data. A total of 152 snow samples were collected from 70 sites over four weeks. The amount of powder varied from 0.2 to 58.6 grams per square meter, depending on location and particle size. Smaller, lighter particles traveled farther from the Sahara, while heavier, larger particles settled nearer to the source.
Dust composition shifts with distance
The make-up of the dust changed as the plume moved northward. Iron-rich particles tended to be deposited closer to their sources, with Pyrenees samples showing about 11 percent iron, decreasing to roughly 2 percent further north in the Swiss Alps.
Dust that settles on ice and snow can harm delicate ecosystems. It darkens bright surfaces, reducing albedo and causing more solar absorption which accelerates melting. The same principle applies to clothing color; dark fabrics absorb heat while light fabrics reflect heat, influencing how hot a person feels.
For instance, the 2018 dust event was linked to a winter snow-cover reduction of as much as 30 days in some locations.
Cesium, beryllium and lead in the dust
The February 2021 dust plume prompted media coverage alleging a rise in radionuclides such as cesium and beryllium, with claims tied to past nuclear tests conducted in the Sahara. France’s 1960s nuclear tests are part of the historical record referenced in discussions around these elements.
Scientists verified these observations through analysis. Cesium levels and a rise in short-lived radionuclides were detected in the Pyrenees. They noted that elements like beryllium and lead, commonly linked to radioactive fallout, accumulated on ground surfaces via recent snowfalls containing atmospheric dust.
Pu-239 and related plutonium levels did not show a significant deviation from background values, reflecting historical nuclear activities in the northern hemisphere during the 1950s and 1960s.
Dumont and colleagues suggest that the nuclear footprint of the current dust may differ from earlier Sahara-related French tests due to variations in fuels and engines used. Traces of cesium and lead measured in the Sahara align with global fallout from 1950s and 1960s tests by the United States and the Soviet Union, rather than solely with French activity.
Researchers note that French nuclear tests carried only a fraction of the power of those conducted by the United States and the Soviet Union. The study’s authors call for further work to understand how the predicted increase in such dust events will influence water supplies, snow and ice melt, runoff, avalanche risk, and the management of ski resorts.
Reference work: essd.copernicus.org/articles/15/3075/2023/
…