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  • The lead (Pb) isotope signa...
    Walraven, N.; van Os, B.J.H.; Klaver, G.Th; Middelburg, J.J.; Davies, G.R.

    The Science of the total environment, 02/2014, Letnik: 472
    Journal Article

    In this study the origin, behaviour and fate of anthropogenic Pb in sandy roadside soils were assessed by measuring soil characteristics, Pb isotope composition and content. In 1991 and 2003 samples were taken at different depth intervals at approximately 8 and 75m from two highways in The Netherlands. The Pb isotope composition of the litter layer (206Pb/207Pb=1.12–1.14) differs from the deeper soil samples (206Pb/207Pb=1.20–1.21). Based on a mixing model it is concluded that the samples contain two Pb sources: natural Pb and anthropogenic Pb, the latter mainly derived from gasoline. 206Pb/207Pb ratios demonstrate that the roadside soils were polluted to a depth of ~15cm. Within this depth interval, anthropogenic Pb content is associated with organic matter. Although Pb pollution only reached a depth of ~15cm, this does not mean that the topsoils retain all anthropogenic Pb. Due to the low pH and negligible binding capacity of soils at depths >15cm, anthropogenic Pb migrated towards groundwater after reaching depths of >15cm. The Pb isotope composition of the groundwater (206Pb/207Pb=1.135–1.185) establishes that groundwater is polluted with anthropogenic Pb. The contribution of anthropogenic Pb to the groundwater varies between ~30 and 100%. Based on the difference in soil Pb content and Pb isotope compositions over a period of 12years, downward Pb migration is calculated to vary from 72±95 to 324±279mgm−2y−1. Assuming that the downward Pb flux is constant over time, it is calculated that 35–90% of the atmospherically delivered Pb has migrated to the groundwater. •Lead isotope composition of litter and topsoil differs from the deeper soil samples.•Litter and topsoil contain anthropogenic Pb, with gasoline Pb as main source.•Anthropogenic Pb is strongly associated with organic matter in litter and topsoil.•Approximately 35–90% of atmospherically derived Pb migrated to groundwater.•Migration is caused by low soil pH and lack of reactive phases in subsoil.