Mobile iron, aluminium and carbon in sandy coastal podzols of Fraser Island, Australia: a quantitative analysis

Abstract

SUMMARYIn this paper podzols of free‐draining sands in south‐eastern Queensland are examined. The 14 profiles represent a chronosequence from young incipient podzols, to ancient ‘giant podzols’ of Pleistocene age, with a spodic horizon at a depth of 8–10 m.Carbon, Fe and Al were determined in pyrophosphate, and Fe, Al and Si in oxalate extracts. The resulting profile distributions were modelled by three expressions, fitted for each attribute, which accounted for surface accumulation, B horizon development and a phase (B/C horizon) of constant composition with depth.The parameters may be used to characterize soil profiles. They show that there is a tendency for the accumulation of carbon in the B horizon to be reflected by Fe and particularly A1 accumulation, which supports the proposition that carbon is directly associated with the transport of A1 and Fe.A feature of many of these soils is a deeply weathered surface with little tendency for commensurate development of an illuvial horizon. Rates of removal of Fe and Al from the A horizon were obtained by comparison of the depths of leaching with age estimates based on geomorphology, and they indicate a non‐linear rate of increase in the thickness of the A horizon.