After yesterday's hot and smoky post where I discussed the impact of smoke on air quality, the wind shifted just enough to clear us out some, with an accompanying drop in PM2.5 (note the decline in the brown line just after noon on 7-10).
In addition, although the ozone concentrations were higher than the were the previous day at noon, with the decrease in smoke, they dropped just a bit during the afternoon, resulting in a lower peak (compare blue line above on 7-9 and 7-10). This may be evidence that the hydrocarbons accompanying the smoke were contributing to higher ozone levels.
Unlike our wintertime PM2.5 pollution where we have met the enemy and it is us, the above illustrates that there are some regional-scale factors that contribute to elevated PM2.5 and ozone in the summer. We are still our own worst enemy, but emissions from fires and other regional sources related to fossil fuel combustion play a role.
BTW: Yesterday's high at the Salt Lake Airport reached 104º, matching the record for the day. It was also our 9th triple digit day of the year (average is 5). So far we are running 7.6ºF above average for July.