Shallow retardation of the strontium isotope signal of agricultural liming - implications for isoscapes used in provenance studies

An intensified debate centers on the use of strontium isotopes in surface water run-off as archive for bioavailable signatures in prehistoric provenance studies. Its use has been challenged by a recent suggestion that modern agricultural liming of farmlands exerts a serious imprint on the strontium isotope compositions of these waters. We here present results from a soil profile beneath agricultural farmland in the glaciogenic outwash plain of central West Jutland, Denmark, which show that strontium and its isotope composition derived from lime products is efficiently retained near the surface. Pore waters and bioavailable strontium from the acidic zone below the surface soil depict strontium isotope signatures that can best be explained by a mixture of silicate-derived and relic natural (not agriculturally added) carbonate-derived strontium. We therefore argue that agricultural liming does not contaminate groundwaters and groundwater-supported surface waters, rendering reference maps based on them relevant for modern and past provenance studies. [Display omitted] •Agriculturally added strontium is retained in the top soils.•We investigated a soil profile from farmland that experienced long-term liming.•Lime-derived strontium does not penetrate into the vadose zone.•Provenance studies depend on suitable characterization of baselines.•Strontium in surface water is used to characterize baselines for provenance studies.