Geochemical soil survey of the Netherlands. Atlas of major and trace elements in topsoil and parent material; assessment of natural and anthropegenic enrichment factors

Geochemical surveying is a generic tool to provide high quality, multi-element databases of the Earth’s surface compartments such as soil, sediment, and stream water. Such databases are not only an essential component of environmental knowledge, but also of relevance to other fields such as spatial planning, agricultural practice, epidemiology, and forensic sciences. The principal objective of the geochemical soil survey of the Netherlands is to provide a spatially representative, high quality, multi-element overview of the inorganic soil composition on a regional scale. In the first part of the thesis therefore, the results of the geochemical soil survey are laid down in a geochemical atlas, which contains information for over 40 elements in both the topsoil layer and the soil parent material from 358 locations. The locations are representative of the most common soil profiles and agricultural and semi-natural land use types in the Netherlands. To facilitate the interpretation of the patterns as observed in the atlas, a considerable amount of background information on the geology, pedology, and geography of the Netherlands is provided along with this first part. Whereas the principal objective of this thesis is of a largely inventory nature, more specific research objectives dealt with in the second part of the thesis focus on the understanding of the processes or factors that govern the bulk-chemical distribution of elements in the soil compartment on a regional scale. In a highly industrialized and densely populated country like the Netherlands, these not only include a number of natural processes, but also antropegenic influences. To differentiate between both, it is of greatest importance to have a clear understanding of the processes underlying the natural variation of element concentrations in the soil compartment. The natural variation of the soils in the Netherlands was inferred from the composition of the subsoil, or soil parent material. Results show that the majority of major and trace elements in the subsoil is principally related to the Al-bearing mineral fraction, whereas only a few elements are dominantly contained in other mineral phases. Regional variation in the composition of sandy soils in the Netherlands is caused by mineralogical differences related to sediment provenance. Furthermore, natural enrichment of various elements in conjunction with organic matter is observed in near-coastal areas in the Netherlands. The integrated knowledge about the natural variation in the deeper soil layer is used to evaluate the composition of the topsoil. This shows that the topsoil layer in the Netherlands is on average enriched by a factor two or more in P, Cd, Cu, Hg, Pb and Zn, which is largely the result of (historical) input by antropegenic emissions from industry, traffic, and agricultural practice. Also S, Bi, Sb, and Sn are antropegenically enriched in the toplayer. The enrichment of these elements shows considerable differences between mineral and organic soils, which are mainly due to a different density and not so much to a different input to these soil