Zn/Pb Concentration Ratios Emphasize Spatiotemporal Airborne Metal Dynamics in Soils Under Different Land Use

Zinc (Zn) and lead (Pb) concentrations were measured in 173 samples collected in soils under forest, wetland, and arable land around a Zn smelter plant that stopped activity in the 1960s. The adopted sampling strategy consisted in collecting 0-30-cm-depth samples from all soils, tilled or not, in order to harmonize the analyzed soil volume to that of plowed soils. Airborne deposition was modeled as a function of the distance from the pollution source and of land use. The Zn/Pb concentration ratios in the surface layer remarkably contrasted 3-4, 1.5-2, and similar to 0.5 for arable, wetland, and forest soils, respectively, independently from the distance to the emission source, while total Zn and Pb concentrations, taken separately, were only slightly discriminant. For metal pollution sites originating from former industrial activity, Zn/Pb concentration ratios determined on relevant soil samples represent a powerful indicator that provides easy and rapid information in real field conditions on time-related input/output dynamics of mobile and less-mobile metal pollutants, and hence, on interactions between pollutants and soils under different land use conditions.