Mystery of London's 1952 Killer Fog is Solved
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Mystery Of London's 1952 Killer Fog Is Solved:
Londoners are used to a regular dose of fog, drizzle, and cloud in the winter. But in early December 1952, the city's fog took a much deadlier turn.
By the time "the big smoke" had lifted just five days later, it had killed 4,000 people and left 150,000 others seriously ill in hospital with respiratory tract infections. In the long term, it's estimated at least 12,000 people died from the killer fog, along with thousands of animals.
[...] Sulfates were a key component of the London fog. This gave the fog its definitively thick, smelly, and toxic properties. It's always been correctly assumed that the London fog was caused by sulfur dioxide released by the burning of low-quality soft coal from chimneys, industry, and power plants. However, why this sulfur dioxide turned into sulfuric acid remained unknown.
[...] "Our results showed that this process was facilitated by nitrogen dioxide, another co-product of coal burning, and occurred initially on natural fog," lead author Renyi Zhang of Texas A&M University explained in a statement.
"Another key aspect in the conversion of sulfur dioxide to sulfate is that it produces acidic particles, which subsequently inhibits this process. Natural fog contained larger particles of several tens of micrometers in size, and the acid formed was sufficiently diluted. Evaporation of those fog particles then left smaller acidic haze particles that covered the city."
A similar chemistry is happening right now in the air of rapidly industrializing Asian cities, many of which are in China. [..] High levels of ammonia from China's extensive fertilizer use and road traffic neutralizes the particles. This makes it less acidic, but a still utterly unsavory cocktail of sulfur dioxide and nitrogen dioxide.
Journal Reference:
Gehui Wang, Renyi Zhang, Mario E. Gomez, et al. Persistent sulfate formation from London Fog to Chinese haze [open], Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.1616540113)
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