Spatial Variability of Soil Heavy Metals in Characteristic Fruit Planting Area:a Case Study in Cangzhou

Geographic information system(GIS) combined with geostatistics was applied to reveal the spatial variability of soil heavy metals(Cu,Zn,Pb,Ni,Cd,Cr,Hg and As) and its affecting factors based on data from 1470 points of surface soil(0-20 cm) samples in Cangzhou of Hebei Province.The results showed that the content exceeded the national soil quality criteria with the exception of Hg,Cr and Pb.The highest and lowest coefficient variation of the eight heavy metals was Hg and Cr,and the value was 0.40 and 0.10 respectively.A significant correlation was also observed between the eight heavy metals at 1% level.The C0 /(C + C0) ratio of Ni and Cr was lower than 25% which indicated strong spatial dependence,while the other six heavy metals C0 /(C + C0) ratios were between 25% and 75%,and had moderate spatial dependence.The range of heavy metal content varied from 25.99 km to 108.80 km,and the Cd had the largest range which indicated that Cd was correlated and depended on the soil parent material.Correspondingly,the Cr had the smallest range 25.99 km which implied that the length of the spatial autocorrelation was much longer than the sampling interval.The spatial distribution map showed similar geographical trends that western part was higher because there were more factories.The result showed that all the eight heavy metals were mainly affected by parent material,however human factors such as transport exhaust,chemical fertilizer and pesticides could not be neglected too.