# Tag Info

## Hot answers tagged pm2.5

10

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 the maximum one-hour ozone concentration was 0.58 ppm. Since then, that number has come down to about 0.12 ppm. You can obtain the latest ozone data from EPA....

8

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 $O_3$, $PAN$, $VOCs$, $NO_x$ have all declined. And O3 variation trends were strongly correlated to $NO_x$ which can be explained by the VOC-NOx chemistry. Another material I have ...

7

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) $\rightleftharpoons$ NH$_4^+$(aq) + H$_2$O(l) The end product is an ammonium ion. We also have gas phase species SO$_2$ and NO$_2$ in air. They dissolve in water ...

7

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. There is a massive overabundance of data in this paper that mostly speaks for itself, but let me summarize. The subway was in first place or last place in most ...

6

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: Increasing SO$_2$ increases PM$_{2.5}$ Increasing NO$_2$ increases PM$_{2.5}$ Increasing NO$_2$ doesn't necessarily increase O$_{3}$ The last point is what you ...

5

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. Their figure 8 is a rough schematic of where particles of different size deposit in the lungs. Things with very large or very small inertial impaction size get ...

5

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 equates health risk categories to the pollutant concentrations. The pollutant with the highest health risk (at present concentrations) will effectively determine ...

4

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 question is during the middle of winter, which generally does not have enough sunlight to allow ozone to build up in the atmosphere. Furthermore, when there ...

3

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 (which could be as fast as one measurement per minute), the compact device shown in the image in question uses a single filter position, and just keeps measuring ...

1

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 popular approach is often called the US-based system. Pollutant concentrations for each pollutant are transformed onto a normalised numerical scale of 0 to ...

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