Owing to their structure, layered double hydroxides (LDHs) are nowadays considered as rising materials in different fields of application. In this work, the results obtained in the usage of two different LDHs to remove, by adsorption, some cationic and anionic pollutants from industrial wastewater are reported. The two compounds MgAl-CO3 and NiAl-NO3 have been prepared through a hydrothermal synthesis process and then characterized by means of PXRD, TGA, FESEM, and FTIR spectroscopy. The available wastewater, supplied by a galvanic treatment company, has been analyzed by inductively coupled plasma-optical emission spectrometry (ICP-OES), resulting as being polluted by Fe(III), Cu(II), and Cr(VI). The water treatment with the two LDHs showed that chromate is more efficiently removed by the NiAl LDH through an exchange with the interlayer nitrate. On the contrary, copper and iron cations are removed in higher amounts by the MgAl LDH, probably through a substitution with Mg, even if sorption on the OH− functional groups, surface complexation, and/or precipitation of small amounts of metal hydroxides on the surface of the MgAl LDH could not be completely excluded. Possible applications of the two combined LDHs are also proposed.

Acorn barnacles are sessile crustaceans common in shallow-water settings, both in modern oceans and in the Miocene geological record. Barnacle-rich facies occur from polar to equatorial latitudes, generally associated with shallow-water, high-energy, hard substrates. The aim of this work is to investigate this type of facies by analysing, from the palaeontological, sedimentological and petrographical points of view, early Miocene examples from Northern Italy, Southern France and South-western Peru. Our results are then compared with the existing information on both modern and fossil barnacle-rich deposits. The studied facies can be divided into two groups. The first one consists of very shallow, nearshore assemblages where barnacles are associated with an abundant hard-substrate biota (e.g., barnamol). The second one includes a barnacle-coralline algae association, here named “barnalgal” (= barnacle / red algal dominated), related to a deeper setting. The same pattern occurs in the distribution of both fossil and recent barnacle facies. The majority of them are related to very shallow, high-energy, hard-substrate, a setting that represents the environmental optimum for the development of barnacle facies, but exceptions do occur. These atypical facies can be identified through a complete analysis of both the skeletal assemblage and the barnacle association, showing that barnacle palaeontology can be a powerful tool for palaeoenvironmental reconstruction.

No abstract

Metal-polluted mine waters represent a major threat to the quality of waters and sediments in a downstream basin. At the confluence between acidic mine waters and the unpolluted waters of the Gromolo Torrent (Liguria, North-West Italy), the massive formation of an ochreous amorphous precipitate takes place. This precipitate forms a soft blanket that covers the torrent bed and can be observed down to its mouth in the sea. The aim of this work is to evaluate the dispersion of metals in the Gromolo Torrent basin from the abandoned Cu-Fe sulphide mine of Libiola to the Ligurian Sea and to assess the metal remobilisation from the amorphous precipitates. The mineralogy of the superficial sediments collected in the torrent bed and the concentrations of different elements of environmental concern (Cu, Zn, Cd, Co, Cr, Mn, Ni, Pb, As, and Sb) were therefore analysed. The results showed that the precipitates contain high concentration of Fe, Al, Cu, and Zn, significantly modifying the bulk chemistry of the Gromolo Torrent sediments. In order to evaluate the possible remobilisation of ecotoxic elements from the amorphous precipitates, bulk leaching tests were performed with both deionised and seawater. Bulk leaching tests with deionised water mobilised primarily high Pb amounts, but also relatively high concentrations of Fe, Al, Cu, and Zn are released in the leachate. In seawater tests, Fe, Al, Cu, and Zn were released in smaller amounts, while other elements like Mn, Cd, Co, and Ni increased in the released fraction. Pb was still strongly released as in deionised water experiments. The results show that the interaction of precipitates and seawater can remobilise high concentrations of metals, thus affecting the surrounding environment.

In this study we have examined the currents and hydrological characteristics of the water column off the mouth of the Gromolo Torrent (north-western Italy) in relation to the grain-size, mineralogical characteristics and metal distribution in the marine sediment sampled. Our purpose was to quantify and map the contamination that was carried out to sea from the abandoned Libiola Fe-Cu sulphide mine that has heavily impacted the torrent. Our results show high concentrations of Cu and Zn, and relatively high concentrations of Cd and Ni inside the bay into which the Gromolo Torrent flows. However, high concentrations of As, Cr, Hg, Mn, Pb, and V found in the northern and/or eastern parts of the study area originated from other sources. The subdivision of study stations in terms of metal and mineral contents in the bottom sediments highlighted the clear influence of the currents on their dispersion and distribution in the area.