16

If you are smelling something, you are inhaling gases, particles, or a combination of the two. They don't normally build up in the atmosphere because of three reasons: transport/dilution (which you mentioned), chemistry, and deposition. Yes there is plenty of fresh air out there but as you say, over billions of years there would be a lot of accumulation ...


12

Normally, temperature broadly decreases with altitude, and convection is effective: locally warmer air will rise, and cooler air will fall. A temperature inversion is where the air temperature rises with altitude. This means that convection is less effective because the air above is already warmer, and so there is less mixing of air between altitudes. Since ...


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 ...


8

A quick literature search seems to confirm Gordons estimation, even at the scale of a whole bucket: [T]he annual mean pH, based upon samples collected weekly during 1970-1971 and weighted proportionally to the amount of water and pH during each period of precipitation, was 4.03 at the Hubbard Brook Experimental Forest, New Hampshire; 3.98 at Ithaca, ...


8

Winter and Summer smog There are two types of smog: winter smog: high emissions of soot and of $SO_2$ through heating with wood, coal, etc. $SO_2$ reacts to sulfuric acid => formation of particulate matter => reduced visibility summer smog (photochemical smog): strong sunlight and emissions of $NO_X$, $CO$ and VOCs emissions of primary particulate ...


7

Raindrops gain a small amount of acidity as they fall through carbon dioxide in the air, but that's not what this question is about. Raindrops commonly start off as ice crystals which have to nucleate around something, usually an aerosol particle such as soot, clay, bacteria, sulphur dioxide , dimethyl sulphide, etc. If a small raindrop nucleates around an ...


7

My guess would be a combination of boundary layer, cloud cover, and emissions (though that isn't terribly specific). Smog is a combination of nitrogen oxides (which cause smog's brown color), ozone, and particulate matter. These in turn form from emissions of hydrocarbons and nitrogen oxides from vehicles and industrial combustion. If those emissions are ...


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 ...


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 ...


6

As others have noted, a temperature inversion is a layer where temperature increases with height. This is called an inversion because the normal temperature profile decreases with height. A temperature inversion can trap pollution. Factors that influence this are the environmental temperature profile, the height of the chimneys or smokestacks that expel ...


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 ...


6

Farrenthope is correct, but I would like to add some detail. An inversion occurs when the air is warmer than the ground. It is called an inversion because it is the opposite of what occurs during the day. During the day, the ground is heated by the sun and the air near the ground rises. However, during clear and calm nights, the ground will cool faster ...


6

Under the right conditions (in a basic sense, locally high relative humidity; see also this discussion on this site regarding contrail formation), the clouds initially formed by contrails may persist for hours and spread outwards to form larger areas of cirrus cloud. Additionally, NASA's Contrail Education Project website has some specific examples here ...


5

Temperature inversions are important to meteorology and pollution because they are the boundary for atmospheric mixing. If there is a strong inversion, the air above and below an inversion do not easily mix together. In the case of pollution, where the emissions come from the surface, a shallow temperature inversion in the boundary layer traps the ...


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 ...


5

You ask, How to remove these abnormal value for more precise data? The short answer is that you might be able to make your data look more representative of the natural 'truth', but you will probably have to pay for this with some precision. The problem is that the measurement itself is imperfect: this looks like an artifact of the data collection method. ...


5

Background pollution is what would be measured if no anthropogenic emissions existed. In other words, if you shut off human activity (or avoid the emissions from it), you can measure the background. Sometimes this is called the natural background. There are also regional backgrounds, like "the US background", which additionally includes anthropogenic ...


5

The first thing to do is to stop putting pollution in the air, particularly very small particulate matter that are produced by combustion. For the Beijing Olympic Games of 2008, the Chinese government forced the polluting plants and factories in the vicinity of Beijing and nearby areas to stop operating for weeks prior to the games and during the games to ...


4

By way of reference, "humidity depends on water vaporization and condensation, which, in turn, mainly depends on temperature". From the information you have supplied in your comments. There are waters in Bucharest and forests in the suburbs, but no waters or forests where the country house is located. From your information, Bucharest has a number of ...


4

In order to put your question in perspective, you need to consider atmospheric mixing and the size of the system you are curious about. The troposphere is several kilometers thick and the mixed layer of atmosphere above the ground can occupy a significant fraction of the troposphere. Granted, during cold events, the temperature of the air can be so cold ...


4

Each one of the monitor siting examples you list has a different purpose. As you have listed, a monitor will be sited for air regulatory compliance purposes (e.g. determining the highest concentrations downwind of a major source), understanding the region (e.g. representative site in well-mixed location), or health exposure risks (e.g. densely populated ...


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 ...


4

1. Basic concepts of visibility loss The deterioration of visibility can be divided into four parts as follows: absorption of gases + scattering of gases + absorption of aerosol + scattering of aerosol quote from a Ph.D dissertation link here scattering is a process where the incident radiation is reradiated into all directions after ...


4

What differences exist between natural rain and human “rain”? The only physically measurable difference between rain from seeded clouds and unseeded is in the seeds/ cloud condensation nuclei/ aerosols that are the surface that moisture can condensate onto and form cloud droplets. Measurements You could collect rainwater, evaporate it and the remaining ...


4

Pollution shouldn't contribute to produce freezing rain. It might have an impact in the precipitation rate and location but not on the likelihood of freezing rain. Freezing rain requires not only that the near-surface temperature is below freezing, but also that there is a temperature inversion that provides above zero temperature in the atmospheric layers ...


4

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 ...


4

Oxidation states of sulphur vary between -2 and +6. Sulphur compounds are generally emitted in reduced form. They are then oxidised in the Earth’s atmosphere, generally to SO2 , a +4 oxidation state. Around 65% (the remainder is removed by dry deposition) of this sulphur dioxide is eventually oxidised to the +6 state of H2SO4 , where SO2 – 4 is ...


3

Put it this way: We like our air to be mixed around well. Mixing the air prevents uneven concentration buildup of not just pollutants (smoke, ozone, chemicals, etc), but also fog (which is pooling of cool and moist air), smells, even sounds (that's why you can often hear distant traffic more near dawn). There are two places that air near the ground can go:...


3

I haven't found proper references yet, but this hasn't gotten an answer yet. To speculation! Long-lived (non-precipitating) clouds can decrease solar insolation at the surface, reducing convection and mixing below the cloud and increasing pollutant concentrations. If clouds are just a symptom of a high-humidity environment, that can promote the condensation ...


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