It’s usually a very expensive process to clean the soil, whether by heat treatment, chelation and/or washing. One less-expensive way around outright soil retreatment is soil management, where the goal is to prevent plant absorption of the contaminants.
Global Warming. We will have more of our money confiscated from us so China can be clean.
Of course getting rid of ethanol and growing more corn so we can export food to China would be out of the question.
I was thinking that planting some kind of plant that absorbed the heavy metals (potatoes or maybe kudzu) and then processing the plants to recover the heavy metals might be an option. It would take the food out the food chain but there are likely other uses for the crops - ethanol perhaps?