Spatial distribution characteristics of heavy metals in the sediments of Changjiang River system - Geostatistics method

The spatial distribution characteristics of 11 heavy metals (Cu, Pb, Zn, Cd, Hg, Co, Ni, As, Cr, Mn, and Fe) in the sediments of Changjiang River system were studied using geostatistics method. The spatial distribution features were quantitatively described by variogram. Based on the variograms, Kriging interpolation was performed, and distribution maps were produced. The results show that all of the heavy metals being studied have good spatial structures, and their variograms could be fitted by spherical models with nuggets. Most of the ranges of variograms are around 1 000 km, which are consistent with average distances among patches with the same feature in the distribution maps. Over about 500 km, most elements show some directional features, and most of them have relatively good correlations in the directions of NE-SW or NW-SE, which are consistent with the trends of their spatial distribution.