SMALL-SCALE DISTRIBUTION OF AL, HEAVY-METALS, AND PAHS IN AN AGGREGATED ALPINE PODZOL

Aggregates of the EA horizon, the Bhs and the Bs horizons of an Alpine Podzol were separated into core and surface fractions. In the air-dri ed aggregate fractions CEC, C-org, 7 fractions of Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn using a sequential extraction procedure, and PAHs were determined. Cation exchange capacity, C-org and PAHs were determined i n homogenized bulk soil samples, too. Both cation exchange capacity an d C-org were higher in the aggregate surface than in the core fraction s. Total concentrations of Al, Mn, Fe, Cr, Ni, and Zn were lower in th e aggregate surface fraction of the EA horizon and generally higher in the B horizons. Total Cu, Cd, and Pb, however, were enriched in the a ggregate surface compared to the core fractions, at least in the upper two horizons. All metals were more available in the aggregate surface than in the core fractions. The total concentration of PAHs was highe r in the aggregate surface than in the core fractions. The enrichment in the aggregate surface fraction was highest for the more soluble com pounds with low molecular weight and decreased with depth. These resul ts suggest that the small scale heterogeneity of metals and PAHs is th e result of both atmospheric input with preferential sorption at aggre gate surfaces, and soil internal redistribution due to eluvial and ill uvial processes. Implications may arise for interpreting plant availab ility of heavy metals and PAHs as well as for modeling transport in ag gregated soils.