G. De Giudici

Natural Biomineralization in the Contaminated Sediment-Water System at the Ingurtosu Abandoned Mine

The Ingurtosu Pb–Zn mine (S-W Sardinia) was exploited for about a century until 1968. Huge amounts of tailings were abandoned, resulting in long-term heavy metal dispersion processes in both soils and waters. Zn and Pb concentration in tailings and soils attains values up to thousands of mg per kilogram. The maximum Zn concentration in water attains several hundreds of mg per liter, whereas Cd and Pb concentrations are in the order of thousands of μg per liter. Heavy metal concentration in waters of Rio Naracauli, the main stream of the area, is abated by seasonal biomineralization processes. Precipitation of hydrozincite [Zn5(CO3)2(OH)6] and of a Zn-rich amorphous phase results in a decrease of Zn concentration down to a few mg per liter. Other metals such as Pb, Cd, Cu, and Ni are coprecipitated with the Zn phases. This chapter reports the state of our knowledge on the Naracauli biomineralization process.

Zn biomineralization processes and microbial biofilm in a metal-rich stream (Naracauli, Sardinia).

Several decades after the closure of the Ingurtosu mine (SW Sardinia), a variety of seasonal Zn biomineralizations occurs. In this work, waters, microbial consortia, and seasonal precipitates from the Naracauli stream were sampled to investigate chemical composition of stream waters and biominerals, and microbial strain identity. Molecular and morphological analysis revealed that activity of dominant cyanobacterium Leptolyngbya frigida results in precipitation of Zn silicate. The activity of the cyanobacterium was associated to other bacteria and many kind of diatoms, such as Halamphora subsalina and Encyonopsis microcephala, which are trapped in the process of biomineral growth. In this work, the precipitation process is shown to be the result of many different parameters such as hydrologic regime, microbial community adaptation, and biological mediation. It results in a decrease of dissolved Zn in the stream water, and is a potential tool for Zn pollution abatement.

Microscopic biomineralization processes and Zn bioavailability: a synchrotron-based investigation of Pistacia lentiscus L. roots

Plants growing on polluted soils need to control the bioavailability of pollutants to reduce their toxicity. This study aims to reveal processes occurring at the soil-root interface of Pistacia lentiscus L. growing on the highly Zn-contaminated tailings of Campo Pisano mine (SW Sardinia, Italy), in order to shed light on possible mechanisms allowing for plant adaptation. The study combines conventional X-ray diffraction (XRD) and scanning electron microscopy (SEM) with advanced synchrotron-based techniques, micro-X-ray fluorescence mapping (μ-XRF) and X-ray absorption spectroscopy (XAS). Data analysis elucidates a mechanism used by P. lentiscus L. as response to high Zn concentration in soil. In particular, P. lentiscus roots take up Al, Si and Zn from the rhizosphere minerals in order to build biomineralizations that are part of survival strategy of the species, leading to formation of a Si-Al biomineralization coating the root epidermis. XAS analysis rules out Zn binding to organic molecules and indicates that Zn coordinates Si atoms stored in root epidermis leading to the precipitation of an amorphous Zn-silicate. These findings represent a step forward in understanding biological mechanisms and the resulting behaviour of minor and trace elements during plant-soil interaction and will have significant implications for development of phytoremediation techniques.

Erratum to: Zn biomineralization processes and microbial biofilm in a metal-rich stream (Naracauli, Sardinia)

Species composition of diatoms in biofilm, morphology characteristics, and site characteristics fromwhich the diatoms are known according to: Krammer and Lange-Bertalot (1991); Van Dam et al. (1994); Levkov (2009); Wojtal (2009) Instead of: Species composition of diatoms in biofilm, morphology characteristics, and site characteristics fromwhich the diatoms are known according to: 1—Krammer and Lange-Bertalot (1991); 2—Van Dam et al. (1994); 3—Levkov (2009); 4— Wojtal (2009)