Geochemical Map Zeeland

The geochemical map of Zeeland was created using the underlying data of the thesis Geochemical patterns in the soils of Zeeland, natural variability versus anthropogenic impact (see researchsection). The map was constructed to illustrate the different spatial patterns of the geochemical components and can be regarded as an, not officially published, appendix to the thesis.

Using the selection button below, the different components and their method can be selected. For information regarding the data collection, read on ...

Please select an element( and method)
Kies element (enmethode)

Data collection

Data for the map was collected in the period of 1998-2003 at Zeeland, South-West of the Netherlands. Location of the area and sampling locations are given in the figure on the left. The locations are situated in the agricultural Holocene marine clay area of the province. On each location about 15-20 subsamples were taken from the plough-layer (about 0-30cm) and the subsurface layer (about 50-100cm) resulting in two composite samples, respectively the topsoil sample and subsoil sample. The samples were analysed using aqua-regia inductive coupled plasma mass spectrometry (ICP-MS) and x-ray fluorescence (XRF).

The sampling and analytical procedures are extensively described in chapter 4 of the thesis, which can be read online or downloaded as PDF. This chapter also contains informations about analytical performance, reproducibility, standards used and summary statistics.

Explanation of the map

The map is devided in four graphs showing information of the spatial patterns in the geographical space, distribution of the elements within attribute space, and the relation with Al2O3. The latter being representative for the clay mineralogy to which many components are related. A key to the map is given in the figure to the left.

Graph 1 denotes the actual map, it shows two bubbleplots, one for the topsoil concentrations and one for the subsoil. The size of the bubbles is representative for the magnitude of the concentration of the depicted element. The background of the map is a kriged interpolation of the values. Although, kriging is used, it is just illustrative with very limited geostatistical meaning.

Graph 2 depicts a Box-and-Whisker plot of the distribution of the top- and subsoil data and shows the outliers. The boxes show the values between the second and fourth quartile, the so called interquartile range, while the whiskers show the value of 1.5 times respectively the second and forth quartile.

Graph 3 shows a cumulative frequency distribution plot where the probability of a value, shown as percentile, is plotted against the concentration. A normal distribution depicts as a straight line so deviations are easily recognised. Bends in the curve may indicated a skewed distribution. Higher and more deviating values are often typical for human influenced concentrations.

Graph 4 gives the relation between the element and Al2O3 which is represenative for the clay mineralogy of the area for both top- and subsoil. As described in the thesis, the subsoil can be used as a baseline which represents the natural soil background concentrations. Deviations from this baseline may indicate enrichment due to human input of certain elements, for example the so called "heavy metals". Not every element is associated with Al2O3.

A more detailed description of the above figures, the used statistics and interpretation is given in chapter 5 of the thesis. This can be read online or downloaded as pdf

PhD thesis


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Deze pagina's zijn auteursrechtelijk beschermd: © 2007 Job Spijker