system
Given the following post, respond as if you're commenting on Reddit:
human
Does the oxygen content of air differ much between a city and a forest?

Is that what makes forest air so much more refreshing? Or is it less pollutants? Also, would oxygen content differ between a city park and a downtown area?
gpt
Forests, plants, trees and even rain forest jungles actually account for far less atmospheric oxygen than most people assume. Atmospheric oxygen at sea level is around 209,460 ppmv (20.946%) and this is fairly evenly distributed around most of the planet. The core of your question seems to be more along the lines of, would there be more atmospheric oxygen near the 'source'? The short answer is yes. Arctic and antarctic regions have slightly higher oxygen ratios due to the abundance of oceanic phytoplankton in those regions. Oxygen saturation is inversely proportional to the temperature of the water and phytoplankton life is abundant in cold waters. The amount of oxygen produced by single cell organisms is way more than that produced by multicellular plants. That's one of the problems with global warming. Geological evidence says that there's less oxygen in general when the Earth is warmer to the point where extinctions are common during the warm periods while biodiversity increases during the cold periods.