Scanning electron microscopy of haze particles

Planet? capsule? jelly? No, it's not right. These are smog particles under a scanning electron microscope. Yesterday, teachers and students from Xi'an Jiaotong University collected the Xi'an Mist Particles, which was magnified hundreds of thousands of times in front of reporters. The complex appearance and composition were shocking.

What is the curiosity of smog?

“A lot of people know what smog is, but what is smog?” When troubled by haze this spring, Professor Shan Zhiwei, Executive Director of the Xi’an Jiaotong University’s Weiner Center, raised the issue, but no one around could answer him.

“What is the composition of smog? What is it like?” Under the guidance of Shan Zhiwei, graduate student Ding Mingshuai and his classmates began a special study. From March to April for two months in a row, they used silicon wafers to collect airborne particles each day, which were then amplified by tens of thousands to several hundred thousand times by a scanning electron microscope.

Ding Mingshuai said that they selected 1081 particle analysis, of which 494 PM2.5 particles. The smog particles under the microscope made him an eye-opener.

Analysis of the highest proportion of dust particles is mainly car exhaust

According to their appearance and composition, they classify air particles into seven categories. The highest proportion is dust particles, reaching 33.4%. The main components are aluminosilicates, calcium-rich particles, and their shapes are extremely irregular.

Followed by sulfur particles, accounting for 14.8%. Some are like salt grains and some are like pompons. "The main source is car exhaust. Once the sulfuric acid in the air is combined with water vapor, it is easy to generate weak acid, which has a corrosive effect." Shan Zhiwei said.

The ratio of coal fly ash and soot aggregates accounted for 9.5% and 6.1%, respectively. The shape of coal-fired fly ash is mostly a regular sphere. They believe that these two components should be related to the burning of coal and natural gas.

There are also sources of ingredients that are difficult to determine, such as silicon oxides, iron oxides.

Marvel at the curious appearance of special zinc particles like a bunch of grapes

Trace elements containing the most exotic particles. The titanium-bearing particles are semi-transparent spheres filled with titanium oxide particles; the bismuth-bearing particles are bamboos that are full of branches and their sources are unknown; the zinc-containing particles are like a bunch of grapes.

The biggest concern for Shan Zhiwei is lead and chromium particles. "This particle has been observed many times. The proportion of lead itself is relatively large, but when combined with other substances, it is like sitting in a small plane and spreading it around in the air, which is particularly harmful to health."

They also tested the mechanical properties of some particles and found that some of the particles had a hardness of 5 to 10 times that of steel. The inside of the granules is also very peculiar. The coal-fired fly ash particles are cut open and the interior is full of blister.

It is recommended to lock the haze source and take measures to reduce the hazard

"Understanding the haze component will make it easier to lock down the source and take targeted measures," said Shan Zhiwei.

He suggested that for dust particles, legislation should be adopted to regulate construction behavior; for automobile exhaust gas, additional installations can be used for effective filtration; for coal-fired fly ash and soot aggregates, new technologies can be adopted and energy structure can be adjusted to solve them.

Shan Zhiwei also reminded that while paying attention to health hazards, do not ignore the impact of PM2.5 on the industry. "High-hardness particles can cause damage and damage to high-precision machinery and equipment. It is necessary to improve the packaging process, the packaging environment, and reduce the impact of smog on the industry."