Abstract：An improved BCR three step sequential extraction procedure was used to investigate the morphology of six heavy metals ( Zn, Cr, Pb, Ni, Cu and Cd) in the surface agricultural soils around coal gangue heap in Jiaozuo Zhongmacun coal mine. Based on the fraction distribution analysis of these metals, the contamination degree and risk assessment of heavy metals were conducted by a potential ecological risk index and a risk assessment code ( RAC) . The results indicated that: ( 1) the average concentrations of Zn, Cr, Pb, Ni, Cu and Cd were 81. 43, 48. 58, 33. 59, 29. 31, 24. 32 and 0. 48 mg·kg- 1, respectively, and some heavy metals contents decreased with the distance from the coal gangue heap; ( 2) the exchangeable fraction of Cd, Ni and Zn reached 36. 54%, 11. 39% and 4. 1%, respectively, and according to the RAC, Cd has a high risk and Ni has a low or a moderate risk to the environment; ( 3) the potential ecological risk index calculated by total concentration and bioavailable fraction were 134 ~ 360 and 67 ~ 266, suggesting that the heavy metals had a low or a moderate potential ecological risk; ( 4) the coal gangue heap was the main source of Pb, Cu, Ni and Cr.

Keyword：coal gangue;heavy metals;morphology distribution;potential ecological risk index;risk assessment code;