The ozone in the upper atmosphere is on average only about 3mm thick if brought down to sea level. given that the density of ozone at sea level is 2.0 grams/litre, what is the total amount of ozone (in tonnes) in the upper atmosphere when it's sea level thickness is 3.2mm? take the radius of the earth to be 6400 km. (the volume of a thin skin around an object is the surface area of the object times it's skin thickness).