Principal component analysis as a tool to indicate the origin of potentially toxic elements in soils

Distinguishing between different sources of potentially toxic elements in soils can be difficult. This paper describes an application of principal component analysis (PCA) to distinguish between geogenic enrichment and anthropogenic pollution with Be, Cd, Co, Cr, Cu, Hg, Ni, Pb, and Zn at 14 localities in Northern and North-eastern Czech Republic. Element speciation, profile distribution, and local geology were used to facilitate interpretation of the PCA results. Of the total element contents in the topsoil and subsoil, a group of non-polluting elements, comprising Co, Cr, Cu, Ni, and Zn, was identified by PCA. There were more non-polluting elements in the subsoil than in the topsoil. The silicate-bound fraction was the most abundant in their speciation. They are likely to be mainly of geogenic origin, therefore. Beryllium also probably originated mainly from parent rocks. However, it had a closer relationship with geogenic Hg and Pb. Cadmium, Pb, and Hg showed strong topsoil enrichment. In speciation, there were larger proportions of their mobile and mobilizable fractions. This implies a significant contribution of anthropogenic pollution to their soil content. In addition, sites with some geochemical anomaly and polluted sites were indicated by the PCA. The analysis provided a concise summary of the complex information on both the generally prevailing origin of potentially toxic elements and the origin of elements at individual sampling localities.