Enrichment of trace elements from long-range aerosol transport in sandy podzolic soils of southwest France

Abstract

Total content of trace elements (Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn), was determined to a depth of about 1 m in the horizons of three representative podzolic soils (i.e., wet moor, dry moor, and dune soil) developed on the coarse sands of the Atlantic face of southwest France. In the aged soils (wet moor and dry moor), Cr, Cu, Ni, Pb and Zn, were highly concentrated in the B horizons whereas Cd accumulated in the litter. An estimate of metal balance was made in the soil profiles, comparing the total amount of metal recovered in the A-B horizons to the amount of indigenous metal determined in a rock matter (C) layer of a similar depth as the A-B horizons. Substantial long-term enrichment of the whole upper part of the profile (A-B horizons) of three representative sites was found for Cd (0.1–0.6 kg ha⁻¹), Cu (3–12 kg ha⁻¹), Ni (1–7 kg ha⁻¹), Pb (20–26 kg ha⁻¹), and, to a lesser extent, for Co, Mn, and Zn. Since the experimental site was remote from industrial, urban and agricultural activities, the increase in soil metal content was apparently caused by the deposition of metallic aerosols via long-range transport. Total long-term inputs are estimated for average values of Cd (0.6 kg ha⁻¹), Cr (5 kg ha⁻¹), Cu (12 kg ha⁻¹), Ni (7 kg ha⁻¹), Pb (25 kg ha⁻¹) and Zn (6 kg ha⁻¹) for the 1 m depth. Several Atlantic areas of Europe are probably affected by a similar metal input.