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| Titel |
Investigation of Chromium and Nickel mobility in serpentinite soils and rocks: Impact into groundwaters and influences of carbonation. |
| VerfasserIn |
Ilaria Baneschi, Claudio Natali, Chiara Boschi, Laura Chiarantini, Massimo Guidi |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250083910
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| Zusammenfassung |
| Potentially harmful elements such as Cr and Ni in soils are increasingly drawing the attention of scientists and authorities due to their potential toxicity to humans and ecosystems.
In the Tuscany region high levels of Cr in Ni have been reported in ultramafic rocks and soils. Furthermore, concentrations of Cr in groundwater of several aquifer systems of this area can approach the maximum contamination level of 50 µg/l, mainly in the form of Cr (VI). The main mechanism for mobilization Cr (VI) at these sites is the weathering of Cr (III) from ultramafic rock with subsequent oxidation.
To characterize the effects of weathering and the accessibility of geologically sourced and potentially toxic Cr and Ni in coastal Tuscany EU and Regione Toscana financed a multidisciplinary project, named RESPIRA.
The study of waters, rocks and soils was conducted in the some sites of the coastal area of Tuscany, where concentrations of Cr (VI) in springwaters are around 50 µg/l (like in Querceto and Montecastelli) or below the detection limit, such as in Santa Luce. It has to be noted that at the site of Montecastelli and Querceto carbonation of serpentinite outcrops has been revealed (Boschi, 2011), together with iron rich brucite.
Chemical and mineralogical analyses were conducted on rock and soil samples by scanning electron microscopy (SEM), electron microprobe (EMP), X-Ray Fluorescence (XRF) and seven-steps sequential extraction.
Extraction analyses were performed to obtain quantitative information on the distribution of trace metals in different mineralogical phases (clay minerals, carbonates, amorphous Fe, Mn oxides, organic matter and other silicates and oxides).
The results show that the residual fraction was the predominant form of Cr and Ni in soil and rock samples. However, the concentrations of Ni associated to exchangeable, carbonates, Mn oxides and non cristalline fractions were higher than those of Cr, indicating that Ni was more available than Cr in all samples tested by the sequential extraction. The major concentrations of Cr and Ni extracted correspond to the non-crystalline fraction. This suggests that Cr and Ni could be adsorbed by amorphous Mn and Fe hydroxides after the weathering of serpentinites and be released at different redox conditions, increasing in this way their mobility in the environment.
Moreover, even the Cr associated to more labile pool (exchangeable, carbonates, Mn oxides and non cristalline fractions) represents a small fraction of the total natural Cr in soils and rocks analysed, the concentrations are high enough to impact ground water quality.
Boschi C., Baneschi I., Langone A., Agostini S., Dallai L., Dini A., Guidi M., Tonarini S. (2011). Spontaneous CO2 mineralogical sequestration in mine waste materials: an example from Montecastelli copper mine (Tuscany). Epitome-Geoitalia 2011, Volume 4: 97 |
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