This study is one of very few dealing with the distribution and the origin of heavy metals in French soils from a priori non-polluted forest areas. The abundance of heavy metals measured in these soils decreases as follows: Cr) Zn)Pb)Ni)Cu)Co4Cd. Total concentrations of Pb, Cr and Ni in some soils exceed the European thresholds for non-polluted soils and even the French association of normalization critical values for sludge spreading. The lowest heavy metal contents are observed in acid soils while the highest concentrations are in the calcaric cambisol and in the mollic andosol, which is rather scarce as compared with the other French forest soils. With the exception of the podzol, Cr and Ni concentrations increase with depth in all soil profiles. The distribution pattern of Co, Cu, Zn depends on the soil characteristics. In some acid soils, however, Cu and Zn decrease with depth. Pb and Cd are accumulated in the upper soil horizons. Heavy metals accumulate in deep soil horizons in relation to important clay content in the dystric planosol and stagnic luvisol. The concentration of each heavy metal is always controlled by different parameters (soil pH, iron and aluminum oxide content, clay content, organic matter and cation exchange capacity), which are heavy metal specific. This study highlights the metal-trapping character of andosol and calcaric soil, the weak heavy metal retention in acid soils, the leaching and trapping character in leached clayed soils, and the migration of heavy metals in the podzol. Pb and Cr concentrations indicate a significant enrichment in surface horizons from various soils in areas which receive significant acid atmospheric pollution. Particularly, the highest Pb content is observed in a soil located in the N-NE part of France. Lead isotope ratios measured in the cambic podzol and the calcaric cambisol, exhibit the importance of the anthropogenic sources and particularly the influence of global atmospheric inputs from leaded gasoline compared to regional and local industrial emissions. The anthropogenic Pb contribution is estimated to 83, 30 and 11%, respectively, for surface, intermediate and deep horizons of the cambic podzol located in the northern part of France, and to 68% in surface horizon of the calcaric cambisol located in the Alps.

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Les affluents de la rive gauche du fleuve Garonne, dans le Sud-Ouest de la France, traversent des bassins versants marqués par de fortes activités agricoles. Pour évaluer la qualité de la phase dissoute de ces cours d'eau, soixante-quinze (75) échantillons d'eau ont été prélevés. Plusieurs éléments traces métalliques ont été analysés dans cette phase aqueuse. Les concentrations moyennes de ces éléments, dans cette région, sont dans l'ordre décroissant : Zn (4,46 µg.l-1), As (1,03 µg.l-1), Cu (0,79 µg.l-1), Ni (0,62 µg.l-1), Cr (0,30 µg.l-1), Co (0,23 µg.l-1), Pb (0,04 µg.l-1) et Cd (0,01 µg.l-1). Ces valeurs sont, pour la plupart, inférieures à celles des eaux de rivières des zones non anthropisées à l'échelle mondiale. La distribution de ces polluants, dans les écosystèmes aquatiques de cette région, est notamment contrôlée par les chlorures et le carbone organique dissous, surtout dans les zones où la contribution anthropique en chlorures et en matière organique est très significative. Dans les zones moins anthropisées, la disponibilité de ces éléments traces métalliques, dans la colonne d'eau, diminue lorsque le pH et l'alcalinité augmentent conformément aux processus géochimiques naturels. Ces observations traduisent l'action prépondérante des activités anthropiques sur la mobilité et la disponibilité biologique des polluants métalliques dans les affluents du fleuve Garonne.