Abstract
Environmental geological survey of a chemical works situated in NE Hungary has been performed for decades. Up till now, several hundreds of drillings of different depths as well as engineering geological soundings have been carried out in the area. Vivianite has been found in a discrete part of a drilling in a gray, silty bed at the depth 6.8–8.5 m. Vivianite was analyzed using X-ray powder diffraction (XRPD), thermal analysis (TG/DTG), and scanning electron microscopic and energy dispersive spectrometry (SEM–EDS) techniques. To demonstrate the spatial distribution of hydrochemical parameters and selected chemical constituents the available data concerning drillings and hydrochemical analyses were collected and evaluated, and field measurements were also performed. For mapping the distribution of relevant physico-chemical parameters and chemical constituents kriging interpolation method was used. Archive aerial photographs demonstrate that a coffered, earth-bedded reservoir for storing huge amounts of extracted plant debris is situated in the vicinity of the drilling. Our study suggests that orthophosphate derived from decomposing biomass entered the groundwater and accumulated within the lowest permeability zone of the intact bedrock. Therefore, the discrete appearance of vivianite in the drilling can be regarded, at least partly, the result of a man-induced mineralogical process.
Highlights
Vivianite is a hydrous ferrous iron phosphate mineral [Fe3(PO4)2·8H2O] named after John Henry Vivian (1785–1855), an English mineralogist, by Abraham Gottlob Werner (1749–1817)
Beneath the approximately 3 m thick mixed clayey–silty–sandy anthropogenic filling, there is a 1 m thick silt of brown color followed by a 4 m thick clayey formation containing vivianite of earthy appearance and bluish color at the depth ranging from 7.6 to 8.5 m showing aggregates of flattened crystals on a background consisting of quartz and phyllosilicates (Fig. 5)
X-ray powder diffraction (XRPD) and thermal analytical studies show that the mineral constituents of the layer are quartz (63%), illite ± muscovite (19%), plagioclase (13%), calcite (3%) and chlorite (2%) (Table 2)
Summary
Vivianite is a hydrous ferrous iron phosphate mineral [Fe3(PO4)2·8H2O] named after John Henry Vivian (1785–1855), an English mineralogist, by Abraham Gottlob Werner (1749–1817). Vivianite can be formed as a secondary mineral in the oxidation zone of ore deposits, and it may precipitate in sediments under reducing conditions in fluvial, lacustrine, marine and estuarine environments, and waterlogged soils (Rothe et al 2016; Grizelj et al 2017). It can be found in organic-rich, highly contaminated canal beds (Dodd et al 2000, 2003; Taylor and Boult, 2007), in wastewater sludge (Frossard et al 1997) as well as in archeological settings (McGowan and Prangnell 2006). Since increased nutrient supply is favorable for vivianite authigenesis, its occurrence in sedimentary settings may indicate human impact (Goslar et al 1999)
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