Are you suggestin' that gases accumulate in runoff?
That's the thing about the uranium decay series. Just after radium, it has this gaseous stage called radon, which doesn't matter one whit when it's sealed into a rock; an atom of radon in the middle of a piece of granite just sits there for a few days and then goes right on into being lead.
But if it's near the surface of a grain of sand or something, that radium turns into radon and the radon escapes into the surrounding air. And it goes wherever the air goes for the next day or two, before turning into lead.
So if that radon is in the runoff, it just fizzes out like any other dissolved gas, and blows around in the air along with all the other gases that make up the air, exactly like any other radon that had an escape route when it was created. There's radon in the air everywhere, right now, a brief stop on the decay chain that is otherwise all solids. And those atoms of radon are undergoing alpha decay all the time, turning into atoms of lead, minuscule bits of dust popping into existence, everywhere.
That's the thing about the uranium decay series. Just after radium, it has this gaseous stage called radon, which doesn't matter one whit when it's sealed into a rock; an atom of radon in the middle of a piece of granite just sits there for a few days and then goes right on into being lead.
But if it's near the surface of a grain of sand or something, that radium turns into radon and the radon escapes into the surrounding air. And it goes wherever the air goes for the next day or two, before turning into lead.
So if that radon is in the runoff, it just fizzes out like any other dissolved gas, and blows around in the air along with all the other gases that make up the air, exactly like any other radon that had an escape route when it was created. There's radon in the air everywhere, right now, a brief stop on the decay chain that is otherwise all solids. And those atoms of radon are undergoing alpha decay all the time, turning into atoms of lead, minuscule bits of dust popping into existence, everywhere.