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REVIEW ARTICLE
Germanium in the soil-plant system—areview
Oliver Wiche
1,2
&Balázs Székely
2,3,4
&Christin Moschner
1
&Hermann Heilmeier
1,2
Received: 20 April 2018 /Accepted: 6 September 2018 /Published online: 14 September 2018
#Springer-Verlag GmbH Germany, part of Springer Nature 2018
Abstract
Germanium (Ge) is widespread in the Earth’s crust. As a cognate element to silicon (Si), Ge shows very similar chemical
characteristics. Recent use of Ge/Si to trace Si cycles and changes in weathering over time, growing demand for Ge as raw
material, and consequently an increasing interest in Ge phytomining have contributed to a growing interest in this previously
rather scarcely considered element in geochemical studies. This review deals with the distribution of Ge in primary minerals and
surface soils as well as the factors influencing the mobility of Ge in soils including the sequestration of Ge in secondary mineral
phases and soil organic matter. Furthermore, the uptake and accumulation of Ge in plants and effects of plant-soil relationships on
the availability of Ge in soils and the biogeochemical cycling of Ge are discussed. The formation of secondary soil minerals and
soil organic matter are of particular importance for the concentration of Ge in plant-available forms. The transfer from soil to plant
is usually low and shows clear differences between species belonging to the functional groups of grasses and forbs. Possible
uptake mechanisms in the rhizosphere are discussed. However, the processes that are involved in the formation of plant-available
Ge pools in soils and consequently its biogeochemical cycling are not yet well understood. There is, therefore, a need for future
studies on the uptake mechanisms and stoichiometry of Ge uptake under field conditions and plant-soil-microbe interactions in
the rhizosphere as well as the chemical speciation in different plant parts.
Keywords Availability .Trace element analysis .Soil fractions .Rhizosphere .Biogeochemistry
Introduction
Germanium (Ge) closely follows the properties and behavior
of silicon (Si) in biogeochemical cycles and has often been
considered as Bpseudoisotope^of Si (Goldschmidt 1958;
Pokrovsky et al. 2006a). In the upper continental crust of the
Earth, Ge is the 54th most abundant element (Reimann et al.
2014) with an estimated abundance of 1.3–1.6 μgg
−1
(Taylor
1964;Hölletal.2007;Rosenberg2007; Hu and Gao 2008;
Négrel et al. 2016). Ge shows remarkable geochemical simi-
larities to Si, largely due to their identical outer electron struc-
tures and very similar ionic radii (Si
4+
:40pm,Ge
4+
:53pm)
(Höll et al. 2007). The similarity between tetrahedral Ge–O
(175 pm) and Si–O (164 pm) bond lengths (Martin et al. 1996;
Kurtz et al. 2002) allows Ge to readily substitute for Si in the
tetrahedral site of silicate minerals (DeArgollo and Schilling
1978;Martinetal.1996) according to the principles of cam-
ouflage (Goldschmidt 1958). Germanates and silicates are
known to form isostructural compounds (Höll et al. 2007).
As a result, Ge has often been used to trace continental and
oceanic Si cycles (e.g., Froelich et al. 1985,1992;Mortlock
and Froelich 1987; Murnane and Stallard 1990; Derry et al.
2005; Baronas et al. 2016) and to determine changes in
weathering over time (Kurtz et al. 2002;Scribneretal.
2006;Lugolobietal.2010). In aqueous solutions, the domi-
nant inorganic species of Ge is the monomeric germanic acid
(Ge(OH)
4
) which has similar dissociation constants to the mo-
nomeric silicic acid (Si(OH)
4
).
However, Ge has a larger atomic radius than Si. This allows
it to form longer bonds with oxygen and sulfur (Bernstein
Responsible editor: Roberto Terzano
*Oliver Wiche
oliver.wiche@ioez.tu-freiberg.de
1
Institute for Biosciences, Biology/EcologyGroup, TU Bergakademie
Freiberg, Freiberg, Germany
2
Interdisciplinary Environmental Centre, TU Bergakademie Freiberg,
Freiberg, Germany
3
Department of Geophysics and Space Science, Eötvös University,
Budapest, Hungary
4
Department of Geodesy and Geoinformation, Vienna University of
Technology, Vienna, Austria
Environmental Science and Pollution Research (2018) 25:31938–31956
https://doi.org/10.1007/s11356-018-3172-y
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