Saharan dust has gained attention in recent years for its ability to travel across the globe, resulting in picturesque orange skies and a thin layer of wind-blown dust covering our cities. This phenomenon has various implications, including the impact on our infrastructure (such as reduced solar energy production) and global activities (such as decreased visibility for flights). It also affects human health, particularly causing respiratory issues, and has consequences for the natural environment, such as increased cloud formation and reduced temperatures due to the reflection of solar radiation back into space.
In February 2021, Europe experienced an extreme dust deposition event. In response, scientists initiated a citizen science campaign, enlisting individuals in snow-covered mountain ranges to collect snow samples. These samples were then analyzed for dust by Dr. Marie Dumont of the National Center for Meteorological Research in France and her colleagues.
Volunteers and scientists collected snow samples measuring 10 x 10 cm2 throughout the entire dust layer in the Pyrenees (bordering France and Spain) and the European Alps (specifically the regions spanning France and Switzerland) up to an elevation of 2,500 m above sea level. The collected samples were sent to laboratories in Toulouse and Grenoble, France, where they were filtered and dried to extract the dust particles.
The findings, published in Earth System Science Data, indicate that a total of 152 snow samples were collected from 70 locations over a four-week period. The dust volume in the samples varied from 0.2 to 58.6 g/m2, depending on the location. Additionally, the particle size decreased with increasing distance from the Sahara Desert, as heavier and larger particles were deposited closer to the source, while smaller and lighter particles were carried further by the wind.
The composition of the dust also changed with distance. Particles containing iron were predominantly deposited closer to the source, with the Pyrenees samples containing 11% iron by mass, compared to only 2% in the Swiss Alps. The primary deposition of dust occurred on south-facing slopes, aligning with the dominant wind direction that carries dust from Africa.
2023-07-29 00:00:04
Link from phys.org