I saw a documentary about the Chernobyl exclusion zone a couple of years back. One of the more interesting facts was that while the radioation levels on the ground and soil surface have slowly gone down, the radiation levels from the trees are higher.

Explanation for this oddity was also provided, and like most things, makes perfect sense in retrospect. The radioactive particles have been slowly washed downwards in the soil, which explains the soil surface figures. But as the particles get to the depth where trees and saplings have their roots, these suck the particles in and eventually they get distributed in the leaves.

Funky, but oh so natural.