[Reading Science] Will Various Fine Dust Reduction Measures Be Effective?

A Chinese Meteorological Administration official loading bullets containing silver iodide into an anti-aircraft gun for artificial snowmaking.
[Photo by YouTube screen capture]

[Asia Economy Reporter Kim Jong-hwa] Various measures are being proposed to reduce fine dust. These include artificial rainfall to wash away fine dust, installing air purification towers, and spraying water. But do these methods actually help reduce fine dust?

China, one of the countries with the highest fine dust emissions, frequently uses artificial rainfall. Artificial rainfall involves spraying calcium chloride or silver iodide into moisture-rich clouds as seeds for raindrops to artificially induce rain. China's artificial rainfall technology is recognized as the best in the world.

They mainly use large anti-aircraft guns or surface-to-air missiles, and sometimes spray directly into clouds using aircraft. The method of firing shells containing silver iodide into clouds has about a 50% success rate, which is considered quite high.

China also enjoys artificial rainfall to the extent that tens of thousands of devices are installed on the ridges and high peaks of the Tibetan Plateau, where chimneys burn solid fuel to release silver iodide smoke into the clouds. However, despite the high success rate, the amount of precipitation is low, so it does not significantly help reduce fine dust.

Korea's artificial rainfall technology is inferior to China's. Still, several experiments to reduce fine dust have been attempted. From 2010 to 2017, 14 artificial rainfall experiments were conducted in Gyeonggi-do and Chungcheong-do, but only four were successful. Even then, the precipitation was only about 1mm, making the effect minimal.

In January last year, artificial rainfall was attempted over the West Sea, but the effect was negligible. To alleviate fine dust, at least 5 to 10mm of rain per hour is needed, but the precipitation was insufficient. Especially on days with severe fine dust in Korea, high pressure systems dominate.

On such days, the atmosphere is stable with weak winds, so dust does not disperse properly, and there are few rain clouds. Therefore, the success rate of artificial rainfall is significantly lowered. Ultimately, artificial rainfall measures to reduce fine dust in Korea are considered almost ineffective.

Moreover, excessive artificial rainfall attempts in China can disrupt natural atmospheric flows, causing abnormal weather, and snow or rain containing silver iodide may have harmful effects on human health. Frequent artificial rainfall may even trigger abnormal weather in neighboring countries like Korea. This is considered undesirable.

A giant air purification tower installed in Xi'an, China.
[Photo by YouTube screen capture]

The method that has shown some effectiveness is the 'air purification tower.' The massive air purification tower in Xi'an, China, is particularly notable. This 60-meter-high tower works on a simple principle: air passes through a huge filter inside the tower and is released outside. The China Institute of Earth Environment claims it can purify about 10 million cubic meters of air per day.

Although not sufficient, it has achieved some results. The problem is cost. Xi'an spent about 2 billion KRW to build this tower, and the annual maintenance cost is at least 30 to 50 million KRW. Therefore, many scientists within China argue that the cost-effectiveness is insufficient. Even if they want to build more, the high cost prevents expansion, so they barely maintain the existing ones.

To reduce fine dust, water cannons or sprinklers are also used. The idea is to spray water into dust-laden air to remove dust, a method actually tried in China and India. The advantages are low cost and low technical difficulty, making it widely applicable.

However, the effectiveness is unclear. While fine dust concentration slightly decreases at the moment of spraying, it worsens again once spraying stops, making it inefficient in the long term. Another drawback is the limited range of effectiveness.

Recently, drones have been utilized. Drones equipped with filters fly over specific areas to purify the air. Hundreds of airborne air purifiers operate to reduce fine dust in the air. Hundreds of drones must be equipped with air purification devices.

A simulation showing the National Institute of Meteorological Sciences dispersing silver iodide for artificial rainfall.
[Photo by YouTube screen capture]

Drones also carry chemicals and spray them in the air. Chemicals that coagulate fine dust are sprayed to make the dust clump and fall to the ground. However, drone capacity is still small, limiting altitude and payload, and there are concerns about side effects if sprayed chemicals reach the ground, so this method is not easily chosen.

Other measures under discussion include dispersing fine dust by jet engine blasts, installing fine dust purification devices on vehicles, and setting up collection devices in the West Sea to reduce fine dust inflow into Korea. However, these face criticism for low feasibility or insufficient expected effectiveness, which is a limitation.

If the operating costs of air purification towers can realistically be lowered, installations could increase across China and Korea. We hope that practical methods like air purification towers that can effectively purify fine dust will be developed as soon as possible.