Rapid Pollution Buildup

The build up of pollution in the Salt Lake Valley the past two days has been quite remarkable.  Below are photos taken at about 4:30 PM on December 24 (Day 0), 25 (Day 1), and 26 (Day 2) showing how we went from pristine skies to serious smog over a period of about 48 hours. 

PM2.5 data from the Utah Division of Air Quality showed that the 24-hour average PM2.5 for yesterday was 25 ug/m3.  It currently sits at 27.6 ug/m3.  Recall that the National Ambient Air Quality Standard (NAAQS) is 35 ug/m3.  The rise from 0 to 27.6 ug/m3 occurred in about 48 hours during a holiday period, which is both remarkable and disturbing.  

Source: Utah Division of Air Quality

An interesting aspect of the PM2.5 evolution is the dropoff in hourly concentrations during the overnight hours.  At 6 AM this morning, hourly concentrations had dropped to 14.8 ug/m3, but I would expect them to rebound later today.  

This case further illustrates my view that we need to be far more aggressive in declaring mandatory air quality action days during which the use of wood stoves and fireplaces is banned (see earlier posts on this subject here, here, and here).  On Christmas, we were in unrestricted action (a.k.a., "green burn").  Why?  The pollution in the Salt Lake Valley when there is snow on the ground simply builds too fast when a ridge builds in.  It appears we may get at least a partial mix out tomorrow as a weak front and upper-level trough moves through.  This may help the state avoid a NAAQS standard violation, but in the interim we are subjected to poor air quality approaching NAAQS levels.  Although it won't solve our air quality problems, reducing or eliminating wood burning probably represents the lowest-hanging fruit that can be plucked to improve our air quality during wintertime inversions.