Long term changes in Cadmium bioavailability in soil

A study was conducted to examine changes in total and phytoavailable Cd in a soil, which had received inputs of Cd due to fertilization with single superphosphate (SSP) at various rates since 1948. Accumulation of Cd in the soil was highly correlated to application rate of SSP. No evidence was found to indicate offsite movement of Cd, either through horizontal transfer or via leaching through the profile. Increases in soil Cd led to an increase in the Cd content of wheat, which was grown in the soil. However, using a radioisotope dilution technique, a significant proportion of the added Cd was found to exist in a non-bioavailable pool in the soil. A model was developed which estimated that Cd was being fixed in this soil at a rate of 1 to 1.5 % of total Cd added per year. (author)