Heavy metal contents in the most productive Argentinean Humid Pampa soils

Abstract

Argentinean Humid Pampa topsoil samples from sites with different land use patterns were analysed. Texture was dominated by fines (silt+clay > 50%) with high total organic carbon content (2.8 ± 1.8%), particularly in finer soils (3.7–9.9% to 0.99% in sandy soils). Carbon:nitrogen relationship was relatively homogeneous (13.9 ± 3.6%) pointing to a dominant contribution of terrestrial plant detritus. Heavy metal concentrations were low (Fe: 1.77 ± 0.50%; Mn: 446 ± 171; Zn: 48.4 ± 19.5; Cu: 17.6 ± 6.0; Pb: 10.0 ± 4.8; Cr: 7.2 ± 1.8; Ni: 6.1 ± 1.7; Cd: 0.05 ± 0.03 μg g–1) and spatially homogeneous (<50%) with more variability for Cd (±58%); the exception was an industrial site with atypically high values for Zn (111 μg g–1) and Cr (11.9 μg g–1). Heavy metal levels were lower than the Soil Environmental Quality Guidelines for Agriculture land use established in international legislation. Mn-Cu-Pb-Ni-Cd-Cr exhibited positive correlations with soil fine contents (R2 Mn = 0.76; R2 Cu = 0.73; R2 Pb = 0.73; R2 Ni = 0.56; R2 Cd = 0.45; R2 Cr = 0.38; p > 0.05). Heavy metal enrichment factors were low (0.07–2.28) indicating a natural origin.