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| Titel |
Bioavailability of heavy metals, germanium and rare earth elements at Davidschacht dump-field in mine affected area of Freiberg (Saxony) |
| VerfasserIn |
Pavol Midula, Oliver Wiche |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250126290
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| Publikation (Nr.) |
 EGU/EGU2016-5989.pdf |
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| Zusammenfassung |
| Bioavailability research presents an essential tool, in modern phytoremediation and
phytomining technologies, allowing the estimation of plant available fractions of
elements in soils. However, up to date, sufficient interdisciplinary knowledge on the
biogeochemically impacted behavior of specific target elements, in particular Ge
and REEs in mining affected soils and their uptake into strategically used plants is
lacking.
This presented work is focused on a correlation study between the concentrations of
selected heavy metals, Ge and REEs in soils formed on the top of the dump-field of
Davidschacht and the corresponding their concentrations in 12 vascular plant species. The
mine-dump of Davidschacht, situated in the Freiberg (Saxony, Germany) municipality area
was chosen as the study area, which has been considered to be a high contaminated enclave,
due to the mining history of the region. In total 12 sampling sites with differing composition
of plant species were selected. At each sampling site soil samples from a soil depth of 0 –
10 cm and samples of plant material (shoots) were taken. The soil samples were
analysed for total concentration of elements, pH (H2O) and consequently analysed by
4-step sequential extraction (SE) to determine fractions of elements that are mobile
(fraction 1), acid soluble (pH 5) (fraction 2), bound to organic and oxidizable matter
(fraction 3) and bound to amorphic oxides (fraction 4). The plant material was
decomposed by hydrofluoric acid in order to extract the elements. Concentrations of
elements in soil extracts and digestion solutions were analysed by ICP-MS. For all
species bioconcentration factor (BCF) was calculated of the total concentration
of elements in order to investigate the bioaccumulation potential. Arsenic (As),
cadmium (Cd) and lead (Pb) were chosen as the representative heavy metals. Within the
REEs neodymium (Nd) and cerium (Ce) were selected as representatives for all
REEs, since Nd and Ce correlated significant with the other elements from this
group.
High amounts of As, Cd, Pb in mould horizons were proved. The surprisingly highest
concentrations were determined for As (in average 3328 mg kg−1). The results
of the pH measurement indicates acid conditions (in average 4.86, min. 3.89) for
whole mine heap. Due to the mobility of Cd and Pb in acid environment, a high
mobility of Cd in mobile soil fractions (in average 0.58 mg kg−1) was found, that
seems to be responsible for the Cd pollution of Freiberger Mulde river, situated near
the dump-field in the East direction from the studied area. The Pb content was in
the average 1513 mg kg−1. SE analyses shows, that only the minor amounts of
these metals were accounted in fractions I – IV (As: 7.75 %, Pb: 5.48 %, Cd: 26.77
%).
The total Ge content in soil samples was 2.7 mg.kg−1in average. The concentrations of
Nd and Ce were 17.7 mg kg−1and 38.5 mg kg−1, which is even lower than the average Nd
and Ce contents in the Earth crust. However, the concentration of Ge was roughly a factor of
two higher, than this average showing a large pool of Ge that could be accessed by
phytoextraction. The SE analyses shows, that the average in fractions I – IV is even much
lower, than in the case of the above mentioned heavy metals in comparison with Ge (1.75 %),
Nd (3.28 %) and Ce (3.12 %).
The BCF calculated for plants shows, that the only element, which could be possibly used
as the object of phytoaccumulation is Cd (the BCF > 1) in species Populus tremula
(3.0, 1.7), Spirea douglasii (1.4, 2.2) and Tanacetum vulgare (3.2, 1.3) at the most
sampling places. Since these species represent the natural occurring vegetation of
the dump, the use of these species together with soil amendments enhancing the
plant availability of elements in soil fractions hold promise for phytoextraction of
economically valuable metalloids and consequently an in situ bioremediation of the dump
field.
This work was realised with the support of Christin Jahns on behalf of the Saxonia
company and financial supported by grant scheme VEGA 1/0538/15 . The authors are
grateful to students and laboratory assistants contributing in the field work and sample
preparation. |
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