Energy-dispersive X-ray analysis on thin sections and unimpregnated soil material.

A combination of scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDXRA) was used in the study of soil materials. The investigation in situ of components in thin sections was used to estimate chemical elements with atomic numbers 11 upwards, from sodium on. EDXRA could detect chemical elements up to magnifications of X 10 000. The composition of amorphous and micro-crystalline materials cannot be estimated in thin sections by light microscopy but by this technique was clearly displayed. Composition of loose soil material can also be investigated. The material that could be studied by SEM-EDXRA did not need high polishing of the thin section, and the plastic used for impregnation of the soil material was not affected by the investigation.Identification of chemical elements in situ, high resolution of the topographic image and relatively short testing times for the elements make this combination of techniques useful for soil research. (Abstract retrieved from CAB Abstracts by CABI’s permission

Wavelength and energy-dispersive X-ray microanalysis with EMA and SEM-EDXRA on thin sections of soils.

Organic matter, minerals and iron-manganese nodules were studied in thin sections of soils with an electron microprobe analyzer (EMA) and a combination of a scanning electron microscope (SEM) and an energy-dispersive X-ray analyzer (EDXRA). Both instruments were used to estimate the presence and nature of chemical elements in two selected areas, one containing a combination of organic and mineral material and another inside an iron-manganese nodule. The detection of organic matter proved problematic. Of the light elements, N could not be detected with EMA and O was detected but was not specific to organic matter. EMA could not be used for C because of the C coating of the thin section. SEM-EDXRA only detected heavier elements. EMA produced somewhat better X-ray images of heavier elements, especially from an iron-manganese nodule. However, with organic material, SEM-EDXRA X-ray images were similar to or slightly better than EMA. An advantage of SEM-EDXRA over EMA is that the soil material can be analysed at various magnifications with a much higher limit, and point analysis can be made of loose material. For soil material, SEM-EDXRA was better as a routine instrument which solved most problems. EMA can be used as a complementary instrument. Other microanalytical techniques such as the ion microprobe mass analyzer (IMMA) were necessary to analyse light elements in organic material of soils. (Abstract retrieved from CAB Abstracts by CABI’s permission

Chemical element detection in thin sections of soils with the Laser Microprobe Mass Analyzer (LAMMA 500).

Components from thin sections of soils developed on weathered granite were analysed with the Laser Microprobe Mass Analyzer. Fragments of thin sections were mounted on sandwich grids, and perforated with the laser from the edges inwards (laser milling), using the laser light at grazing incidence. Laser-induced mass spectra of secondary titanium compounds and other constituents in the weathered granite were obtained in this manner. Positive and negative laser desorption mass spectra were recorded with such a speed and accuracy that in spite of the relatively large volume of analysed materials, minute changes in composition could be detected over very short distances. This allowed total chemical element analysis of spots in which titanium compounds concentrated during weathering, giving information on changes in purity of amorphous and semi-crystalline materials at such sites. Characteristic analysis possibilities of the Ion Microprobe Mass Analyzer (IMMA), Laser Microspectral Analyzer (LMA) and Laser Microprobe Mass Analyzer (LAMMA 500) are compared. (Abstract retrieved from CAB Abstracts by CABI’s permission

Verdronken dekzandgronden in Zuidelijk Flevoland (archeologische opgraving `A27-Hoge Vaart'); een interdisciplinaire studie naar de veranderingen van bodem en landschap in het Mesolithicum en Vroeg-Neolithicum

Bij een archeologische opgraving in Zuidelijk Flevoland is de bodemvorming en de vegetatieontwikkeling van een dekzandrug langs een diepe holocene stroomgeul onderzocht. Bodem en vegetatie kwamen in de loop van het Atlanticum onder sterke invloed van het grondwater te staan door de snel rijzende zeespiegel. Het landschap veranderde in een zoetwatergetijdengebied met sterk fluctuerende waterstanden. De oorspronkelijke bruine bosgrond degradeerde hierdoor tot een sterk verzuurde en hydromorfe zandgrond. Tussen 6000 en 5500 BP steeg de gemiddelde grondwaterstand in de dekzandrug met een snelheid van minstens 15 cm per eeuw. Rond 5500 BP werd de dekzandrug volledig overgroeid door rietveen