i wouldn't spray with water. blow hard with fan on plant, also on top soil. mercury is bad, mkay? water might make it stick to leaves and absorb. any white powder you see needs to be eliminated at all costs.
that sucks. good luck. you might even take the top 1/4-1/2" of topsoil off and replace it. I wonder how much mercury actually is in CFLs compared to what will make you insane. Lemme see ...