"Cleaning" soil is an interesting concept. At what point does it just become dirt? Presumably some of the nutrients will remain, but it seems like this would sterilize it.
Dirt still has use, of course, but soil is expensive to produce for a reason.
Considering the existing DDT contamination, ending up with dirt that needs to be fortified with compost is hardly the worst trade-off.
I would definitely bet against this if I could. Soil is far more potent than DDT can harm.
DDT, like organic mercury compounds, bioaccumulates up the food chain. Contaminated soil is sequestered to prevent it from contaminating insects and animals and then humans.
Hence, the trade-off: DDT in the ecosystem, or killing soil and rebuilding it with compost and time.