Characterization of products of the early stages of pedogenesis in ornithogenic soil from Maritime Antarctica

Limited pedogenesis on the Antarctic continent results in unusual, but important, short-range order inorganic phases and organo-mineral complexes (both with broad peaks from X-ray diffraction) in the clay fraction, which can be studied by sequential chemical extractions. We aimed to develop a better sequential extraction procedure to obtain more detailed discrimination of the short-range order phases (SROP) of the clay fraction of soil from Maritime Antarctica. Selected chemical properties of the soil and clay fraction were related to different phases of these products. The total amount of SROP and organo-mineral complexes in the clay fraction ranged from 15.1 to 43.9%, with greater occurrence in ornithogenic soil. The continuous incorporation of guano from penguins into the soil profile has contributed to increasing amounts of organo-mineral complexes. Short-range order phases have an important effect on soil chemical properties, such as an increase in non-exchangeable acidity, quantity of hydroxyl groups on the surface of the colloidal fraction, the buffering capacity of Al3+ from non-exchangeable and structural forms of the element, and a decrease in soil CEC. The greater number of sequential extraction steps enabled the separation of SROP and organo-mineral complexes into two phases of stability, with a clear predominance of the more soluble forms.