Psychological-Dog994 OP t1_ja9kopn wrote
Reply to comment by Spiritual_Jaguar4685 in ELI5: Why is it that when fertilizers make their way into waterways, all the oxygen disappears, killing the fish? by Psychological-Dog994
How does water gain dissolved oxygen does it come from photosynthesis?
Spiritual_Jaguar4685 t1_ja9lnyy wrote
A liquid will absorb a portion of any gas it's exposed to, for example water on Earth will absorb gases from the air above it. It's just a natural process called "Boyle's Law", something we've learned from physics and chemistry.
The amount of overall gases a liquid absorbs is complicated, but has to do with pressure (for example, this is why soda and beer bubble like crazy when you open them, because you're removing the pressure in the can and the beer can't hold that much gas at room pressure) and the proportion of the gases dissolved is the same as the proportion of the gases in the air (again, using beer as our example, this is why carbonated beers are so bubbly but only for a short time [lots of CO2 in the beer, barely any in the air, hence it all wants to come out quickly] and why nitrogenated beers like Guinness don't bubble as much and stay bubbly for so long [lots of nitrogen in the, but also lots of nitrogen in the air, it doesn't have any place to go])
Fat_Doinks408 t1_jaacbqb wrote
This is why i f*cken love reddit!! Learn something new everytime!
BudoftheBeat t1_jaav4ay wrote
Right? Like it's osmosis but for gases using liquid as the membrane
TheRichTurner t1_jaahyry wrote
Boyle's law: 'The absolute pressure exerted by a given mass of an ideal gas is inversely proportional to the volume it occupies if the temperature and amount of gas remain unchanged within a closed system.'
Boyle's law has nothing to do with water absorbing gasses.
Mvpeh t1_jaarxiu wrote
Classic reddit moment
ThepunfishersGun t1_jabiieu wrote
Henry's Law (I believe, been awhile since college/grad school) partial pressure of dissolved gas in liquid is proportional to partial pressure of undissolved gas. IIRC, it goes: p1/a1 = p2/a2 where one side of the equation describes gas dissolved at a given atmospheric pressure and the other side describes gas dissolved at a changed atmospheric pressure.
Revenge_of_the_User t1_jaaesjn wrote
The astronaut everyone loves, cant remember his name, demonstrated this not too long ago by being pretty deep below water level where the pressure is just...much greater than on a beach.
He shook a soda pretty vigorously, and then cracked it. Since the pressure was so high down there, the pop only slightly fizzed.
This is also why deep divers have to surface slowly, or spend time in a hyperbaric (pressure) chamber if the need to surface quickly. The nitrogen gas in their blood/tissue expands as they go up, and needs to be done slowly or you get "the bends". Think meat balloon on a cellular level. Can be fatal, or cause life long problems. One guys body swelled up like crazy after an emergency deep dive surfacing (lost his air hose) and survived; though the hyperbaric chamber didnt really help him like it can others - he stayed unfortunately very swollen. But at least he didnt die. The bends are very painful, im told.
All because of gasses in liquids at varying pressures.
BaconIsAVeg2 t1_jaaipsl wrote
> It's just a natural process called "Boyle's Law", something we've learned from physics and chemistry.
Example of it in action here.
paid2fish t1_jaapief wrote
Also, the amount of o2 that water can absorb is significantly affected by water temperature. Colder water holds more o2
Mvpeh t1_jaarwus wrote
Boyle’s law doesn’t apply here.
Moveover, Nitrogen is less soluble than CO2 in H2O, and equilibrates quicker.
breckenridgeback t1_ja9o92e wrote
Ultimately, yes: all of Earth's atmospheric oxygen is from photosynthesis. But in the more local sense, it's just dissolved into the water from the air around it.
zaphrous t1_ja9w9d2 wrote
You can aerate water. This happens naturally where air meets water. You can do it more quickly by spraying the water in the air like a fountain. So a fountain can keep pond fish alive. Or you can use a pump to make bubbles underwater. So probably a waterfall would be the best natural way to get oxygen back into the water, but rough waters would also work well.
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