Geochemical patterns in the soils of Zeeland
2005
It is widely understood that the geochemical environment plays a profound role in the ex- istence of life on earth. A large part of this geochemical environment is the thin layer between the earth crust and the atmosphere. Yet, Bridges and van Baren (1997) already argued that the significance of this thin layer, also called soil, is not always sufficiently ap- preciated, despite its vital role for human well-being. As they summarise, this natural body of mineral, animal, and plant organic matter forms a critical link between the inanimate rocks and minerals and the living plants and animals.
Soil, especially its biogenic content, can affect the biosphere by its role in global cli- matic processes. The bidirectional relations between consumption and production of CO2 , CH4 and N2O can directly influence climatic changes (Mosier, 1998). More directly, soils also play a major role in human health. Mineral nutrients are, mainly, transfered from soil to humans by plant and animal foods. Deficiencies, excesses, or imbalances in this dietary source can have deleterious influences. Such influences can occur on rather large, even global, scale; for example the atmospheric transport of persistent organic pollutants of soils from moderate climatic areas to colder areas, were the cold conditions cause precip- itation of the pollutants and subsequent uptake in the local food chain (Abrahams, 2002). These examples of the close relation between soil, health, and global sustainability confirm that soil plays a critical role as a major interface in our environment and that soil quality can be an important indicator for sustainable environmental management (Doran, 2002).
Soil quality, as defined by Karlen et al. (1997), is ”the capacity of a specific kind of soil to function, within natural or managed boundaries, to sustain plant and animal productivity, maintain or enhance water and air quality, and support human health and habitation”. Soil quality is often described in terms of physical (texture, thickness of topsoil layer, water holding capacity), chemical (organic C, Total N, pH, extractable N, P, K) and biological (biomass, soil respiration) parameters (Wienhold et al., 2004). An evaluation of the vari- ous quality indicators and their change over time may dentify if sustainable management is reached or that soil quality is aggrading/degrading. The type of soil informaton to be evaluated depends of course on the function of the soil, be it a natural ecosystem, food production, or just the base for building (Nortcliff, 2002). The framework and criteria for evaluation often depend on policy choices by relevant authorities or organisations.
This thesis is concerned with obtaining an overview of general (geo)chemical soil quality, within the framework of diffuse anthropogenic pollution and sustainable soil management in the Netherlands.