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The aim of the study was to identify the geogenic source for elevated arsenic (As) concentrations recently discovered in soils
of the Heubach plain, North Rhine-Westphalia, Germany. Therefore, a catalogue of conditions that an As source has to fulfil
in order to be considered as geogenic was formulated, including the source’s linkage to the sink, its mineralogy, As total
content, As mobilization potential, groundwater redox conditions and As output. Accordingly, mineralogical, geo- and hydrochemical
investigations were carried out, including X-ray diffractometry, microscopy, ICP-OES and AAS analysis and a sequential extraction
procedure. Paleo bog iron ores (PBIOs) of Tertiary age, occurring within unconsolidated sands (Haltern-layers, Santonian–Lower
Campanian), and glauconitic marlstones (Dülmen-layers, Lower Campanian) were examined. Results indicate that output from the
PBIOs is responsible for the elevated As levels. Accounting their diverse mineralogy, five types of PBIOs were defined. Type-dependent,
they at least partly fulfil all of the formulated requirements. The relations and behaviour of As sources and sinks in space
and time could be clarified for the area of interest. The approach presented in this paper may offer a tool for identifying
natural As sources worldwide. 相似文献
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