DEPLETION OF 1ST-ROW TRANSITION-METALS IN A CHRONOSEQUENCE OF SOILS IN THE REEFTON AREA OF NEW-ZEALAND

Hydrofluoric-perchloric digestion followed by atomic absorption analysis was evaluated as a means of analysing soils and soil separates. The method was then applied in a study of the first-row transition metals (Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn) in a chronosequence of five soils. The soils ranged from a Dystric Fluvisol on the youngest surface, through Dystric Cambisols on middle terraces to Gleyic Podzols on the higher terraces. Data are presented on both a concentration (mass/mass) and amount (mass/volume) basis to facilitate a meaningful comparison of the transition metal content in soils of widely varying properties. Corrections are made to compensate for comparing soils which have expanded and then contracted during soil development. Silicon, Ti and V were found to have accumulated in the soils over 130 000 years (on a mass/volume basis) primarily as these elements are lost slowly during weathering of their minerals. After applying corrections to relate elemental concentrations to a soil volume at time zero, all the elements (except Ti) were found to have become depleted with time, by over 50% of original mass within 100 000 years.