Distribution and Speciation Analysis of Cd Element in Qingdao Surface Soils

In this paper, the content and chemical speciation of a heavy metal element, Cd, were studied from 63 urban soil samples extracted from five different functional areas, Industrial Area, Commercial Area, Scenic Area, Agricultural Area, and Residential Area, of Qingdao. The analysis results indicated the Cd content in soil was 0.2211 - 3.040 mg/kg, with an average value of 1.289 mg/kg. The contamination level ranked as Industrial Area > Residential Area > Scenic Area > Commercial Area > Agricultural Area. The chemical speciation of Cd varied among the soils from the five functional areas. The distribution trend of the chemical speciation of Cd was obtained as residual fraction > organic form > Fe-Mn oxide > exchangeable form > carbonate form. The sequence of the Cd activation in the areas followed as Scenic Area > Industrial Area > Residual Area > Commercial Area > Agricultural Area. The overall Cd activation level in the soils of Qingdao was relatively high, creating potential hazards to the environment.