engleski

Surface physico-chemical properties of terra rossa and calcomelanosol developed on hard limestone

Two different soils developed on hard limestone in Istria, Croatia, were investigated in order to evaluate the relation between their composition and surface physico-chemical properties. Terra rossa bearing typical Fe-oxide characteristics (e.g., Fed and Fed/Fet) and calcomelanosol enriched in organic matter were analysed. Kaolinites (KlD and Kl), illitic material and Fe-oxides are main mineral phases in the clay fraction of terra rossa while calcomelanosol contains kaolinites, chlorite and vermiculite as main mineral phases in the clay fraction. To define relation between the individual constituents and properties of soils, samples were selectively dissoluted. Granulometric composition, the specific surface area (SSA) and the cation exchange capacity (CEC) were measured on the following subsamples: original samples, samples treated with H2O2, samples treated with H2O2+NH4-oxalate, samples treated with H2O2+NH4-oxalate+Na-dithionite-citrate-bicarbonate. The morphology of samples and size of aggregates and particles were examined by scanning field-emission electron microscopy. Differences were observed between the surface properties of terra rossa and calcomelanosol that are the result of particle-size distribution, mineral composition and different share of organic matter. The distribution of CEC values among subsamples of terra rossa and calcomelanosol is different. On the contrary, the trend of SSA is same in the first three subsamples of analysed soils. The SSA increased proportionally to the amount of the removed organic matter in both soils. Following the dissolution of amorphous Fe-oxides, the SSA decreased. After the removal of well crystallized Fe-oxides the SSA decreased in calcomelanosol and highly increased in terra rossa due to major soil aggregate decomposition and accordingly, increased fine clay content.

surface; physico-chemical properties; terra rossa; calcomelanosol; limestone

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