If memory serves, they carry enough 30mm for around 20 seconds of firing.
So, by the sources I can find the DU penetrator on a 30mm cannon shell is about 0.3 kilograms, and the plane carries 1350 of them. So about 400 kilograms in total, a little under half a metric ton of depleted uranium.
And we know that pilots did just fire off the entire lot at a single target fairly frequently, because of course they want to fire the penis-extender 9000 at every opportunity. Those friendly fire and civilian casualty statistics aren't going to write themselves..
A tank can be sitting around shooting near indefinitely and more efficiently move around when it does have to move while an A-10 can only deliver a few fart volleys per sortie. The intensity of the fighting in Ukraine seems to be quite a bit higher than in Iraq, so one could imagine tanks firing quite a lot without it being tactically gratuitous.
Tanks only tend to carry about 40-50 rounds. Obviously, they're tank rounds so they're a lot heavier, making the total ammo weight potentially comparable with the A10. Realistically, a tank wouldn't carry 50 APDS rounds though. 10 is probably a much more reasonable number. The depleted uranium penetrator also weighs proportionally less at about 5kg. So we can probably assume any given tank only carries a maximum of about 50kg of depleted uranium.
This isn't to justify the use of depleted uranium at all (although I will point out, both sides are doing it) just that there's a relatively big difference in the level of contamination associated with different systems.