# Ozone gas (O₃) endurance in the atmosphere

If I release some ozone gas (O3) to the atmosphere, for how much time will it stay there in its original form? Does it change to some other form by reacting with other atmospheric constituents?

• Where in the atmosphere? Near the surface? – gerrit May 28 '14 at 19:56
• Yes, near the surface at height of 1 K.M – Jashan PJ May 29 '14 at 6:23

$\mathrm{O}_3$ decomposes to $\mathrm{O}_2$.

The rate of decomposition increases with temperature.

At 20 degrees C, the half-life is about 3 days in air.

$\mathrm{NO}$ can catalyze the formation and decomposition of ozone.

• This is more of a "in lab" answer, since the ambient air will not stay at 20 degrees C over night (when most ozone is depleted in urban areas). – farrenthorpe Mar 16 '15 at 18:04
• I like @farrenthorpe 's answer as he goes into more detail, but 3 days is probably in the ballpark and that's what the question asked. The IPCC report is less specific, saying "hours-days". cdiac.ess-dive.lbl.gov/pns/current_ghg.html – userLTK Mar 21 '18 at 11:37

Really, it is impossible to know how long ozone will persist in the troposphere without knowing what the other chemical concentrations (e.g. CO, NOx, HOx) are and what your photolysis rates are (is it night? cloudy? what latitude? how many hours of sunshine?). Ozone is constantly cycling in the presence of sunlight, so if you are concerned about total overall ozone (not just the molecules you released), you will get a very different answer.

As indicated by DavePhD, the amount of NOx in the region will greatly influence the rate that ozone is converted. In an atmosphere with relatively low levels of NOx, it will persist for a few days. If there is no photolysis (e.g. night time) then ozone won't get re-created and high levels of NOx would titrate out most of your ozone overnight. Though there is a happy medium where moderate levels of NOx will actually increase your total ozone concentrations.

Also it is important to keep in mind that if there is enough CO in the air, OH reactions with ozone will decrease, as the OH will preferably react with CO, and ozone loss will occur more slowly.

Another important thing to consider is that without rain, HNO3 (which is created when NO2 reacts with OH) will not deposit and ozone precursors can persist for many days, allowing more ozone to be re-created. Finally, don't forget that ozone does get dry deposited as well, so the land surface does have some influence on loss rates.

Considering what I've learned about CFC - chlorofluorocarbons, O3 is easily "annihilated" into O2 and chlorine-containing compounds.

See, CFCs are a group of chemicals found in pressurized containers which, as said in its name, contain chlorine, fluorine, or another halogen. When they reach the ozone layer (from anywhere between 1 week and a few years), they form bonds with the ozone and hijack an O atom to form ClO (chlorine monoxide). The by-product O2 sinks downwards for some reason. The ClO meets a free oxygen atom and breaks into more O2, and Cl-.

I would say that ozone would remain in the atmosphere until CFCs come murder it, probably at least 5 weeks.

• Do you have a reference to back up the claim of 5 weeks? – user889 Dec 8 '14 at 2:37
• Yes, I do. Tropospheric Ozone Please note I have factored in the time it takes for CFCs to reach the ozone layer as well. – boxspah Dec 8 '14 at 2:48
• CFCs do not "form bonds with the ozone"; O2 does not sink downward; to be CFC, a compound must contain only carbon, fluorine and chlorine. – DavePhD Dec 9 '14 at 14:14