A couple distinct possibilities: This is a power plant releasing all this gas. Unlikely, considering how deviant the numbers are from the norm. No other city comes close to how much SO2 is being released from Wuhan. 

A second one: Wuhan is burning municipal trash and possibly contaminated animal carcasses. Possible, but why would they not just dump it where they usually do? 

And the third and most morbid: Dead bodies are being burned on the outskirts of the city, the death numbers are way higher than the CCP is letting on about, and things are really, really bad. 

I don't know the relative probabilities of these events, make up your own mind as to which is most likely. 

Also note that I changed the scale displayed to view only the peaks, look at concentrations above 500ug/m^3 to see the real story. 

If this tweet gets taken down you know what happened. 

This is from 4chins so take this with a grain of salt, but one poster extrapolated from the SO2 release data and estimated 14,000 bodies would have to be burnt to reach this level of emissions. #coronavirus

https://threadreaderapp.com/thread/1226267582740811777.html