Scientists Solve Mystery of London's Deadly Sulfuric Fog

An international team of scientists published a paper in Proceedings of the National Academy of Sciences that shows how the deadly London fog of 1952 was formed.  It's been known for some time that emissions from coal burning are likely to blame, but until now science couldn't explain the appearance of the sulfuric acid that killed the 12,000 people exposed to the murderous mist.  

According to Texas A&M University researcher Renyi Zhang who led the study, "People have known that sulfate was a big contributor to the fog, and sulfuric acid particles were formed from sulfur dioxide released by coal burning for residential use and power plants, and other means.

But how sulfur dioxide was turned into sulfuric acid was unclear. Our results showed that this process was facilitated by nitrogen dioxide, another co-product of coal burning, and occurred initially on natural fog. 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."

The lab experiments and atmospheric measurements that led to the study came from China, which houses 16 of the world's 20 most polluted cities.

Source: EarthSky