A stream-sediment survey was carried out for the island of Aruba. Concentrations in stream sediments represent the abundance of chemical elements in the drainage basins. A geochemical atlas was created from the collected data and natural background values were established. Cluster analysis and pattern recognition techniques were used to gain a better understanding of the data set.

Two cluster models were selected to study the various geochemical controls on the sediments and to establish a spatial basis of environmental-quality settings for the development of future environmental policies. The first cluster model was suitable to recognise in some detail the reflection of the geology on the geochemistry of the stream sediments. The second, coarser cluster model stressed the importance to distinguish between the two main lithological units of the island when instituting natural background values. Not one uniform value per element is valid, but the value depends on the lithology.

A geochemical soil survey was carried out on the island of Curaçao in October 1992 as part of an overall geochemical characterisation of the three Leeward islands of the Netherlands Antilles. The aim of this soil survey was to provide systematic geochemical data of the rural soils of Curaçao for characterisation, geochemical mapping and environmental application. A total of 122 samples was collected from the topsoils (upper 0.1 m) within a rectangular grid (2 km2). All samples were sieved to a grain size of < 2 mm and analysed for 24 elements by ICP-AES, after decomposition with hot aqua regia. A small, selected set of soil samples was subjected to a more extensive study of soil properties.

It appears from statistical data interpretation of the chemical compositions with techniques like non-linear mapping and cluster analysis that the topsoils of Curaçao can be divided into six homogeneous groups (soil types) with contrasting chemical signatures. Labelled according to their dominant geology, soil process or most striking characteristic, these soil types are defined as follows: sandy limestone soil type, Midden Curaçao soil type, arid/calcareous soil type, basalt West soil type, agriculture-influenced soil type, and the basalt East soil type.

Geochemical contour maps were made that provide a basis for environmental issues on the island. Finally, background levels (baseline data) were derived from the chemical soil composition of several elements, taking into consideration the correlation with the Fe or Al content of these soils. The defined baselines can be used to establish background values for future soil surveys.