Accumulation of cadmium derived from fertilisers in New Zealand soils.

Accumulation of cadmium was assessed by comparing 58 soil samples archived up to 50 years ago with present-day soils from the same sites. Mean levels of acid-extractable Cd have increased from 0.39 mg kg-1 to 0.85 mg kg-1 closely matching the amount of Cd applied in phosphate fertiliser. CaCl2-extractable Cd has increased from 0.02 mg kg-1 to 0.11 mg kg-1, a greater percentage increase than for acid-extractable Cd. This may be attributed to added Cd being more mobile than native Cd. Cadmium levels have increased in Allophanic Soils, Brown Soils, Gley Soils, Organic Soils, Oxidic Soils, Pallic Soils, Pumice Soils, and Hydrothermal Recent Soils but not in Fluvial Recent Soils, which appear to have a lower Cd retention capacity.