Spatial Distribution Characteristics of Cd,Pb and As Contents in the Farmland Black Soil in the Northeast of China

Analyses of the spatial distribution of Cadmium(Cd),Lead(Pb) and Arsenic(As) contents in farmland black soil in the Northeast of China indicated that the variance coefficient of Cd content was the highest,As the lowest,and Pb medium.Average contents of Pb and As were higher than the background values for black soil,and there were 45 samples,of which the content of Cd was higher than the soil environment quality standard.There were no distinct patterns in the distribution of Cd,Pb and As in the direction of latitude.According to the results of investigation,pollution of the farmland near coal mines was relatively heavy.Kriging interpolation method was used to create the distribution maps of the three elements in the farmland of the suburb of Changchun city,and it was found that the accumulation of Cd,Pb and As in the black soil was obvious.Analyses of vertical distribution showed that Cd,Pb and As were mainly accumulated within the depth of 0-20cm,and the contents in the subsurface layer were relatively lower.