Patterns in soil quality: Natural geochemical variability versus anthropogenic impact in soils of Zeeland, The Netherlands

Abstract

We demonstrate a structured approach to identify natural as well as anthropogenic geochemical patterns in sedimentary soils, using statistical techniques that increase in complexity and the requirements for auxiliary data. Comparison with the average upper continental crust identified natural regional features, such as a relative enrichment of As, due to a low‐lying deltaic environment, and of Cr and Zr, related to a specific heavy mineral association. Identification of diffuse contamination is best achieved by comparison with a local reference. The Zeeland subsoil is shown to have undergone only minor anthropogenic influence and to serve this purpose very well. A topsoil–subsoil comparison revealed anthropogenic enrichments for Cd, Cu, P, Pb, S, Sb, Sn, Zn, and partly for As, while typically ‘non‐anthropogenic’ trace elements like Cs, Ga, La, and Rb were found not to be enriched. Except for P and S, the enriched components show a good correlation with Al2O3, a proxy for clay mineralogy, and a bivariate topsoil–subsoil comparison is made using a trimmed Reduced Major Axis regression. Two subregions are identified with different associations (Zn, Pb, and Cd, versus As, Cd, Cu, and Sn) of higher‐than‐average enrichments.