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Scientists have discovered a new culprit contributing to China's notorious smog in winter, and controlling it could help maintain significant improvements in air quality that Beijing and other cities in the north-east experienced in the winter last, according to a study published Thursday.
Scientists at Harvard and two Chinese universities have reported that formaldehyde emissions – mainly from vehicles, chemical refineries and oil – play a bigger role than previously thought in producing thick and toxic pollution. which chokes a large part of the country each winter.
In a report published in the journal Geophysical Research Letters, scientists claimed that a "large portion" of sulfur in fog was the result of a chemical reaction between formaldehyde and sulfur dioxide released by the coal combustion.
China's efforts to reduce turbidity have focused in recent years on reducing sulfur dioxide emissions. Although these efforts have borne fruit and drastically reduced pollutants last winter, research suggests that China could further improve air quality by directing its efforts – and resources – towards improving air quality. reduction of formaldehyde emissions in vehicles and industrial refining.
"Our research indicates ways to more quickly eliminate air pollution," said Jonathan M. Moch, Harvard researcher and lead author of the study.
The simplest solution is to improve the ignition switches of cars and trucks and to install rubber seals at service stations to prevent fumes, he said. Reducing emissions from chemical and oil refineries, which are heavily concentrated in Tianjin, the coastal metropolis near Beijing, could also have a disproportionate impact, he said, but these could prove more difficult to apply.
As with efforts to reduce the industrial combustion of coal, significant reductions in refinery production could oppose the economic and political imperatives of the government, particularly at a time when the trade war with the United States threatens China's growth.
When the Chinese Ministry of Ecology and the Environment released its annual guidelines for 28 cities in the northeast of the country last month, it has The requirements for further emission reductions have been somewhat eased and the restrictions imposed last winter have forced many steel mills, coking plants and other factories to close for several months.
This has led many to fear that next winter will once again be clouded by suffocating clouds at the levels of safety recommended by the World Health Organization.
Pollution of the country – measured by the concentration of PM 2.5, or particles of a size considered particularly harmful, has been attributed to one million premature deaths per year.
It has long been thought that the main particles suspended in pollution in China are sulphate, a product of sulfur dioxide released by burning coal. But another sulfur molecule, hydroxymethane sulfonate, is also a major contributor, according to the study conducted with scientists from Tsinghua University in Beijing and the Harbin Institute of Technology in Harbin, capital of Heilongjiang Province. , the most northerly of China.
The molecule is formed by a chemical reaction between formaldehyde and sulfur dioxide, and explains why "extreme air pollution phenomena" have persisted despite efforts to reduce sulfur emissions, the researchers found.
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