Spatial variability of soil hydrochloric acid extractable heavy metals in the Yangtze River Delta

Spatial variability characteristics of soil hydrochloric acid extractable metals(Cd, Cr, Cu, Ni, Hg, Pb, Zn and Co) in the topsoil(0～20 cm) from Kunshan City, the typical region of Yangtze River delta, were analyzed by geostatistical method, and the spatial distribution and its pollution source and cause of heavy metals were discussed. Results show that hydrochloric acid extractable Cd, Cr, Cu, Pb, Zn, Hg are strong variability, while Ni and Co are medium variability. Semivariance analysis show that all the hydrochloric acid extractable heavy metals are fitted for spherical model, and the concentrations of eight heavy metals are correlated in a given spatial range. Kriging interpolation method was applied to estimate the heavy metal concentrations of the unobserved points and their spatial distribution maps were obtained, which indicates that the concentrations of soil hydrochloric acid extractable metal have a close relationship with industry activity, sewage irrigation and atmosphere deposit. Combined principal component analysis with geostatistics, soil hydrochloric acid extractable metals in Kunshan City were composed by four components, and the first component(Cd, Cu, Pb, Cr, Zn) is affected by industrial sewage irrigation, atmosphere deposit and geochemistry feature of element; the second component(Ni) is influenced by soil intrinsic factor, the third component(Hg) relates with industry pollution sources, and the fourth component(Co) is probably affected by topography.