Krypton and radon background in the PandaX-I dark matter experiment

We discuss an in-situ evaluation of the ${}^{85}$Kr, ${}^{222}$Rn, and ${}^{220}$Rn background in PandaX-I, a 120-kg liquid xenon dark matter direct detection experiment. Combining with a simulation, their contributions to the low energy electron-recoil background in the dark matter search region are obtained.