How to remove black mold spots in cellar

My house is a new construction (finished in March) and after a heat wave, I've got black mold spots running all along the corners and floor edging in the basement.
Someone suggested I get a Dehumidifier for the basement. I got a 70 pint at Sears (no manual) and have been running it at 70% humidity level (to dry the air out), but the spots are still there.
How long does it take for these little buggers to die and should I consider something else as well.
I live in New Hampshire if that helps at all.
TIA
Jim
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wrote:

Decreasing the humidity will help prevent the mold from growing and from coming back once the mold is killed. Spray the mold with a bleach solution to kill it, wait 10 minutes, then wipe dry. Consider filling the cracks with the appropriate caulking to seal water and water vapor out.
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