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| Titel |
Metal availability and bio-accessibility in water-logged soils: in vitro experiments. |
| VerfasserIn |
M. C. Florido, F. Madrid, L Madrid, F. Ajmone-Marsan |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250034526
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| Zusammenfassung |
| Reducing conditions of submerged soils were simulated in vitro by keeping various soil
samples for various times of reaction (between 1 and 15 days) in sealed flasks and N2
atmosphere under an aqueous solution, 0.01 M CaCl2 containing 1 g/l glucose.
Surface samples of soils from urban green areas of Ljubljana (LJU), Torino (TOR)
and Sevilla, were chosen. In the latter case, two samples of the same soil were
included, before (SE-0) and after (SE-8) receiving a composted biosolid (two yearly
doses of 80000 kg/ha) obtained from sewage sludge, often used as amendment
by the Parks & Gardens Service of the local Government. A fifth soil (QUE) was
chosen from the area affected by an accident where 2 million m3 of metal-rich mine
tailings were spilled over the Guadiamar river (SW Spain) and its riparian areas. This
highly polluted soil was included for comparison. Values of Eh, pH and several
metal concentrations were determined in the solution after each time, and metal
availability and bio-accessibility were estimated in the soils after treatment. The metals
studied were Fe, Mn and some of those called ‘urban’ metals, namely Cu, Pb and
Zn.
The solution pH for LJU, TOR and SE-0 was slightly acidified in the first days and
increased steadily afterwards. In contrast, QUE and SE-8 show pH increases from the
beginning and a constant pH after 4-8 days. This agrees with the expected H+ consumption
during reduction. Most soils show strong initial Eh decreases, subsequent slower increases up
to 5-8 days and slow decreases afterwards. Solution Fe and Mn showed significant increases
throughout the experiment, and Pb showed slight increases only up to 4 days. In contrast,
other metals showed non-significant changes, and very low amounts were dissolved during
the treatment.
However, the amounts of available and, especially, bio-accessible urban metals
in the solid phases were significantly increased by the treatment. Such increases
may cause a greater leaching of metals to the water table or a greater uptake of
potentially toxic metals. In the case of ornamental sites, playgrounds and other
recreational areas, such increases can have a direct significance on public health
through a hand-to-mouth transfer. The observed increases are significant even in
soils with not very high metal contents, as it is the case of LJU or SE samples. |
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