Point-source emitters in Utah Valley. Source: Snowbrains
As an air quality scientist, I’m constantly looking through poor air quality images such as the what we find in the image above while also finding ways to not only predict when these sorts of conditions will develop but what we can do to reduce their likelihood. So let’s dive into a slightly gross but important topic: Particulate Matter.
Size distributions of particulate matter. Source: John Wenger, University of College Cork
Before we dive in, it’s important to distinguish between particulates and particulate matter. Particulates are the actual airborne particles while particulate matter (PM) refers to the concentrations of these solid and liquid particles that get suspended in the air and are made up of a wide array of elements. We break PM down into two elemental categories: organic and inorganic. Examples from both categories include anything from water vapor to soot from wildfires. They can also carry bits of chemical species, including nitrogen dioxide, ozone, and carbon dioxide, to name a few. As a result, inhaling air with high PM levels can cause both short and, depending on the level, long-term respiratory damage. The severity of the damage to the respiratory system is exasperated whenever the particulates within those concentrations have finer dimensional sizes that make them easier to inhale. In order to account for finer particle concentrations, PM are classified into dimensional categories as well. These include PM10, which include all particulates with diameters that are less than 10 micrometers (um) across, and PM2.5, which only include all particulates with diameters that are less than 2.5um across.
Emitters of particulate matter. Source: Lindsey Konkel, Food and Environment Reporting Network
Unfortunately, high PM conditions have become much more common in developing counties in recent years, including China and India, as emissions have increased in cities, resulting in greater anthropogenically(human-induced) PM levels. Emissions essentially allow for an even greater likelihood that particulates will develop, increasing their concentration while also decreasing their sizes as they take up more space and leave less room for development. In cities that are located in valleys, such as Salt Lake or Mexico City, the entrapment of man-made emissions in their urban cores only further enhances the likelihood that particulates will form, until their concentrations reach critical levels, as can be seen in the images below:
High PM levels over the LA Basin. Source: David Illif
So what can we do to mitigate PM levels in cities? Limiting emissions is the best method to bring those levels down, along with placing industrial centers away from places that geographically enable the entrapment of pollutants, like valleys and basins. Urban projects should be wary of how and where they develop residential areas in order to lower the likelihood that people will be exposed to dangerous PM levels. These are just some of the many methods that can help to reduce particulate concentrations. If you live in an area with high levels of pollution, you can also reach out to local government in order to get the community involved in reducing its emissions!
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©2020 Meteorologist Gerardo Diaz Jr.