10
votes
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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8
votes
Accepted
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 ...
- 797
8
votes
Accepted
How do current pollution levels in Los Angeles compare to the 1970s?
A figure downloaded from this site.
It represent the history trends of the pollutants related to the photochemical pollution from 1960s to 2000s
We can find that $O_3$, $PAN$, $VOCs$, $...
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7
votes
Accepted
How can agricultural ammonia lead to PM2.5 production in the atmosphere?
Acid/Base Chemistry
Gaseous ammonia (NH$_3$) acts as a base when it dissolves in water. The reactions are below.
NH$_3$(g) + H$_2$O(l) $\rightleftharpoons$ NH$_3$(aq)
NH$_3$(aq) + H$_3$O$^+$(aq) $\...
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7
votes
How much worse is the typical subway air, compared to street-level air pollution, in a typical city?
Depends on what type of pollution you are talking about
Moreno et al., 2015 studied this problem in Barcelona, and compared Metro (subway) to trams, buses, and walking in various parts of the city. ...
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6
votes
How to understand the bizarre high level for both PM2.5 and Ozone
I think it is important to keep in mind the mechanisms that form PM$_{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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5
votes
Accepted
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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5
votes
Accepted
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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4
votes
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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3
votes
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 ...
- 13.5k
3
votes
Accepted
What is a Micro-Aethalometer; how do portable Black Carbon (BC) Monitors work?
Following @ Friddy's comment, I started reading Aethlabs AE51 FAQ and was quite surprised!
While a conventional aethalometer use a long tape and move it to the new position after each measurement (...
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3
votes
Accepted
Why (and how) is particulate matter measured in mass per volume?
Why are particulate matter measurements (like PM2.5) from an air quality monitor given in micrograms per cubic meter (μg / mm^3)?
The fundamental measurement for particulate matter is done using a ...
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1
vote
Why (and how) is particulate matter measured in mass per volume?
Your post has multiple questions. Here are a few comments.
If the device does indeed count particles, how does it convert that to mass?
Conversion from particles per volume (a number density $\rho_N$...
- 450
1
vote
How can I test the Air Quality?
Ambient or roadside concentrations for each pollutant, over different
averaging times, will be converted into an index value. In general,
there are three common methods to achieve this. The most ...
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