Real-world ecological half-life longer than expected

I think it's gonna be a long long time...
http://www.wired.com/wiredscience/2009/12/chernobyl-soil/

Reinhabiting the large exclusion zone around the accident site may have to wait longer than expected. Radioactive cesium isn’t disappearing from the environment as quickly as predicted, according to new research presented here Monday at the... meeting of the American Geophysical Union. Cesium 137’s half-life — the time it takes for half of a given amount of material to decay — is 30 years. In addition to that, cesium-137’s total ecological half-life — the time for half the cesium to disappear from the local environment through processes such as migration, weathering, and removal by organisms is also typically 30 years or less, but the amount of cesium in soil near Chernobyl isn’t decreasing nearly that fast. And scientists don’t know why.

It stands to reason that at some point the Ukrainian government would like to be able to use that land again, but the scientists have calculated that what they call cesium’s “ecological half-life” — the time for half the cesium to disappear from the local environment — is between 180 and 320 years.

“Normally you’d say that every 30 years, it’s half as bad as it was. But it’s not,” said Tim Jannik, nuclear scientist at Savannah River National Laboratory and a collaborator on the work. “It’s going to be longer before they repopulate the area.”

The original research pdf is existing here, written in the language English: http://sti.srs.gov/fulltext/SRNL-STI-2009-00770.pdf