Winter Temperature Inversion Fog-Smog: Drastic Enhancement to Local Air Pollution in Some Places

Winter Temperature Inversion Fog-Smog: Drastic Enhancement to Local Air Pollution in Some Places

Recently it has been reported that some areas such as Salt Lake City, Utah have been experiencing meteorological inversion which drastically enhances the concentration 2.5 particulate matter in the immediate breathing atmosphere. This typically increases emergency room visits for asthma and other respiratory issues such as chronic obstructive pulmonary disease (COPD. One study indicated a 40% increase in such visits during these inversions including a 90% increase in visits for COPD. This commonly occurs in Utah counties adjacent to the Wasatch mountain range front. According to Salt Lake City’s website:

“Wintertime inversions are a common event in Utah, occurring primarily during the months of December through February. Prolonged inversions can lead to the high levels of fine particulate pollution, or PM2.5. These high pollutant levels raise significant health and air quality concerns, particularly on days when the pollutant concentrations exceed the national health standards.”

Sources of PM2.5 are vehicles, particularly diesel vehicles, coal-burning power plants, wood fires, and waste biomass incineration. There are primary PM2.5 particulates and secondary PM2.5 particulates, which result from chemical reactions on different sized particles. The Salt Lake city website notes that the major sources there are mobile and area sources (89%) rather than large industrial sources (11%). Area sources include “small industrial and commercial sources that emit less than 100 tons per year of pollution and activities generally associated with urban living, including gas and wood stoves, dry cleaning, gas stations, and water treatment facilities.”

In Utah it is estimated that 25% PM2.5 is primary and 75% PM2.5 is secondary. All are thought to be derived from fuel combustion. The phenomenon of inversion is caused when a warm layer of air develops over a cold layer of air, trapping any rising particulates and keeping them low enough in the atmosphere to increase their concentration in places where people breathe. The phenomenon commonly occurs after a snowfall in subsequent clear skies and van manifest as post-snowfall fogs. I believe the secondary particulates are a result of what’s called “photochemical smog.” In Utah the high particulate air can build up in prolonged inversions between storms.

In Utah the air is monitored for PM2.5 with the Air Quality Index as it is in parts of the country susceptible to particulates and photochemical smog. The Utah Division of Air Quality issues action alerts to indicate when health may be impacted by inversions. They also suggest people drive less during these periods and consider public transportation where available. Several Utah counties have enacted wood-burning bans during inversions and the fines for burning have recently been increased for both first-time offenders and repeat offenders. Fines were increased because even with existing burn bans the wood smoke in the atmosphere did not drop and in the past few fines were actually leveled, as much wood-burning goes undetected. Wood-burning is one of the major sources of particulates and one that should be able to be addressed adequately through both education and fines when necessary. Burn bans happen in many places in the world in winter when particulates increase.

Places susceptible to winter inversion as well as places like California that are very susceptible to summer smog can benefit from low-emissions transportation fuels like natural gas which can be burned in very low emissions engines like the new Cummins natural gas engine that eliminates 99.5% of photochemical smog precursors nitrogen oxides (NOx). Electric vehicles are also emissions free in operation as is solar energy.

The following video shows a Dec. 2017 inversion above the Salt Lake Valley.

References:

Winter Inversions: What Are They and What Can We Do to Help? – by Salt Lake City, Utah website, ci.slc.ut.us http://www.ci.slc.ut.us/winter-inversions-what-are-they-and-what-we-can-all-do-help

The Dirty, Cough-Inducing Inversion Fog Hanging Over the Wasatch Front Might Linger for Weeks – by Luke Ramseth, in The Salt Lake Tribune, Dec. 12, 2017

Higher Wood-Burning Fines Aimed at Utah’s Winter Inversion Days – Forecast to Start This Week – by Emma Penrod, in Salt Lake Tribune, Dec. 6, 2017

Study Shows Spike in ER Visits on Utah’s Bad Air Days – by Brady Mccombs (AP), in Salt Lake Tribune, March 12, 2016

Salt Lake Valley Inversion 2017 -by RoadTrippinNomad, in youtube.com https://www.bing.com/videos/search?q=inversion+fog&view=detail&mid=2077AF0EC6EB4795462B2077AF0EC6EB4795462B&FORM=VIRE