Geologists say the sandstorms in Beijing may be worse than expected
Introduction: Sandstorms are far worse than we thought
In the dust-shrouded city, the sky turns orange, and this phenomenon is caused by the widely reported large-scale sandstorms. From a public health perspective, this is actually not a sandstorm, but a dust storm.
Image source: NOTICIAS CARACOL
This may sound like a show of geology, but it represents a key difference, namely the size of their mineral particles. Grains of sand are mineral particles larger than 0.06 mm in diameter – on windy days by the sea, the raised grains of sand will scratch your ankles, you will chew the grains of sand in the prepared sandwich, and your picnic plan will be ruined. The potential harm of dust is more serious than that of Yangsha.
Beijing and other parts of northern China suffered the biggest sandstorm attack in a decade; Mongolia, which was also attacked, killed at least 6 people and 81 people are missing.
—BNO News March 15, 2021
Dust particles (or what many geologists call silt and clay) are relatively small particles that feel silky to the touch and do not scratch the skin. Crucially, these smaller, lighter particles travel farther away with the wind.
Instead of relying on the short-distance emission movement of sand grains, they are suspended in the atmosphere and spread around the world as the atmosphere travels. Sand won't be blown away for hundreds of kilometres, let alone all over the world – but dust will.
Image source: ScienceDirect
The size of the particles is also an important feature, as dusts smaller than 10 microns (pm10) and especially less than 2.5 microns (pm2.5) can pose a serious hazard to human health because they are small enough to be inhaled into the lungs and reach the depths of the human body.
Long before humans had a widespread impact on the natural landscape, China was already being hit by sandstorms. During the repeated ice ages of the past 2.6 million years, large amounts of dust were generated and precipitated due to glacier movement, forming loess sediments.
Image source: Wikipedia
Over the millennia, these sediments have cumulatively reached a height of 350 meters, forming China's Loess Plateau, which is even larger than the size of France. Loess is rich in mineral nutrients and is a highly productive agricultural soil. Now, these soils have been eroded by wind and are re-entering the cycle in the form of dust.
If such a big change has been witnessed in the past, has the frequency of sandstorms changed today? It would be unwise to start from one region of China alone, because even within that region there are many different patterns and variations.
In fact, there is much evidence that the frequency of sandstorms in China has declined over the past few decades. At the same time, studies have shown that the frequency of dust storms in some parts of China has increased over the past few centuries.
The same complexity is true on a global scale. Israeli studies have shown an increase in the frequency of dust storms over the past three decades, while other studies have shown a decrease in frequency in other regions.
Five points artificial, five points natural
So, what causes the current dust storm problem? Is this entirely due to natural processes, or is it due to the effects of climate change, or is it due to improper land management? The answer is complex – it may contain any of these factors.
A recent study considers the combined effects of regimes and climate change on china over the past two millennia on the frequency of dust storms, and shows that the increase in dust storms coincides with population growth and an increase in the Asian monsoon circulation. Paradoxically, the increase in dust storms occurred during periods of increased rainfall, when the environment allowed for the era to flourish and population growth, increasing the need to clear agricultural land.
In other regions, this process is mostly caused by natural factors. For example, the Bodle Depression, located in the Sahara Desert, in a remote corner of western Chad, is the world's largest source of atmospheric dust, despite its small size and almost uninhabited.
The image above is taken by satellite, and the highlighted area is the atmospheric dust of the Bodlai Depression. Source: NASA
This situation is mainly caused by the extremely arid desert conditions in the area, a vulnerable surface composed of small remains of lake sediment, and the narrow-tube effect of the terrain of the nearby mountain ranges.
On the surface, dust storms have had many negative effects, causing landscape erosion, agricultural land loss, air pollution, and affecting people's health. But dust storms also have some positive effects. They play a key role in transporting critical nutrients, especially iron, to the ocean, and this has been discovered for some time. As a result, dust storms are also considered to be the main "fertilizer" for phytoplankton, the basis of the marine food chain.
Above is a satellite image of dust from the Sahara Desert over the Atlantic Ocean. Image source: Wikipedia
In 2014, a study showed that more than three-quarters of dissolved iron in the northern Atlantic came from the Saharan dust brought by free winds. Other studies have shown that the phosphorus contained in the saharan dust also plays a key role in nourishing the Amazon rainforest.
Therefore, stories like the wind blowing up desert dust in the sky are caused by many factors and are global.
BY: Dendi
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3. The original text comes from: https://www.sciencealert.com/beijing-s-sandstorm-was-actually-a-dust-storm-which-is-bad-news-health-wise
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