# Tag Info

## Hot answers tagged pm2.5

### How do current pollution levels in Los Angeles compare to the 1970s?

The air quality in Los Angeles does not meet federal air quality standards. That being said, the air quality has improved immensely since the 1970s. From the California Air Resource Board, in 1965 ...
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### How is the concentration of particulate matter calculated per cubic meter

The data that you are having are called emission fluxes. If these data are available as global averages then one can calculate global mean concentration by multiplying the residence time of the ...
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### How much worse is the typical subway air, compared to street-level air pollution, in a typical city?

Depends on what type of pollution you are talking about Moreno et al., 2015 studied this problem in Barcelona, and compared Metro (subway) to trams, buses, and walking in various parts of the city. ...
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### How to understand the bizarre high level for both PM2.5 and Ozone

I think it is important to keep in mind the mechanisms that form PM$_{2.5}$ are different than the mechanisms that form O$_3$. From the data your provided you can draw some simple conclusions: ...
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### Which particles are classified as PM2.5? How exactly is this defined?

I think answering your questions in reverse will make more sense. The "size" of PM is typically the aerodynamic/inertial impaction size, as you guessed. My standard reference for this is this paper. ...
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### How can I test the Air Quality?

The AQI calculation does not require that all pollutants be measured. Instead, it uses the pollutants that are available and then uses a function (chosen by the overarching regulatory agency) that ...
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### How to understand the bizarre high level for both PM2.5 and Ozone

Ozone is most closely correlated to temperature. Yes you need NOx and VOCs to create ozone, but you also need enough photolysis driven by sunlight in order for ozone to form. The day analyzed in the ...
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### How is the concentration of particulate matter calculated per cubic meter

You mention "volume" which is the crux of the problem: the surface mixing layer changes height throughout the day as solar heating influences the surface. Consider that the same emission ...
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