Abstract:

In order to thoroughly investigate the spatial distribution of heavy metals, the methods of frequency distribution, bimodal fitting and separation were used to study the characteristics of statistical distribution of heavy metals in Beijing cultivated soil. It was demonstrated that, Cu, As, Cd and Pb were bimodal distribution. Double Gaussion Function could be used to fit the empirical distribution well after log-transformation, suggesting the presence of two independent log-normally distributed populations for Cu, As, Cd, and Pb. The geopmetric means of the two populations were (23.35±6.39) mg/kg and (95.84±38.73) mg/kg for Cu, (9.35±2.20) mg/kg and (23.67±6.16) mg/kg for As, (0.1208±0.0334) mg/kg and (0.3548±0.2344) mg/kg for Cd, (20.07±6.07) mg/kg and (82.55±39.33) mg/kg for Pb, respectively. The four heavy metals all could be divided into low value group and high value group. Heavy metals showed obvious bimodal distribution, the reason could be explained from a statistical point and may be complicated based on the spatial distribution of the two groups.