Characteristics of a polluted artificial soil located along a motorway and effects of acidification on the leaching behavior of heavy metals (Pb, Zn, Cd)

摘要: Abstract Polluted artificial soils (average concentrations: Pb: 1460 ppm; Zn: 2830 ppm and Cd: 2.8 ppm) have been collected at the edge (less than 1 m) of A-71 motorway in Sologne. These are characterized by XRD a procedure sequential extraction Pb, Zn, Cd, Mn Fe ( Tessier et al., 1979 ). Excepting for Fe, “labile” fractions F I, II III, respectively “exchangeable”, “carbonate-related” “Fe-hydroxides-related” dominant on “residual” fraction V. Fraction IV “related to organic matter” is mostly significant Pb. A study different size indicates strong metal enrichment finest one μ m) while extractions suggest that small Fe-hydroxide particles play role fixation Artificial and, comparison, suspensions from nearby retention pond Lee 1996 ) submitted 24 h leaching tests HNO 3 solutions increasing acidity (10 100 mmol/L). Differences between both types samples result mainly buffering effect carbonates, present lacking suspensions. Acid equivalent sum I+F II+F III while, probably kinetic reasons, amounts leached lower. As deduced runs, relative mobility heavy metals found be: Cd>Zn≫Pb, suggesting carbonate-free systems moderately acid rainstorms may leach Cd part Zn border motorway, Pb would remain fixed. similar scale has derived other highly polluted materials related motorways Lebreton Thevenot, 1992 ; Colandini 1995 Touray, 1997 When addition considered, becomes Mn≅Cd>Zn≫Pb>Fe, as well suspensions, spite large differences contents localizations. This agreement with idea most “acid labile” localized within material, comparable diluted proportion local Sologne soil.