Censi, Valentina

Boron (B) and Lithium (Li) concentrations were studied in the Platani river, one of the most important catchments of South-Central Sicily which is under semiarid climatic conditions for roughly eight months to a year. In this area, evaporites result in potential B and Li sources for surface waters. Results from river waters have measured ionic strength values between 0.1 and 4.54 M. B and Li distributions in these waters were studied in colloidal (CF, extracted by ultrafiltration from the 0.45 μm filtrate) and total dissolved (TDF) fractions and in fractions extracted from corresponding riverbed sediments, according to changes of the B/Li ratio. In river waters, CF and TDF showed very similar B/Li values, suggesting that only negligible fractionation occurs between Li and B in the aqueous phase. Similar evidence was observed between B/Li values in TDF and the labile sediment fraction, whereas an inverse relationship arose between B/Li values in TDF and in the easily reducible sediment fraction. This relationship indicates that Mn oxy-hydroxides preferentially react with aqueous B species relative to Li at the riverbed sediment interface. The extent of the B-Mn oxy-hydroxide reactions is influenced by the ionic strength, so that only B/Li values below 4 are measured in river waters with ionic strength values above 0.5 M. Comparing B/Li and ionic strength values measured in the Platani river with those from oxic brines worldwide, the same preferential B removal relative to Li is observed. This evidence suggests that B is removed as positively-charged borate ion-pairs, formed in the aqueous phase under higher ionic strength conditions, reacting with negatively charged surfaces of Mn oxy-hydroxides. The observed B reactivity relative to Li could be exploited to bring down the B excess from natural or waste waters, allowing the natural reactions with Mn oxy-hydroxides to take place under natural conditions.

The Zirconium and Hafnium concentrations in worldwide fumaroles fed by magmatic fluids reveal that the Zr/Hf ratio is inversely related to the temperature of emission. Lower Zr/Hf ratio values below the chondritic signature are found in fluids having the highest temperature while super-chondritic Zr/Hf ratio values are found in lower temperatures. Sub-chondritic values of the Zr/Hf ratio may be related to larger volatility of Hf-chloride gas species with respect to Zr-Cl gas species, while super-chondritic ratios may correspond to fluid-rock processes resulting from cooling of uprising magmatic fluids. We propose that subchondritic Zr/Hf ratio values in fumaroles associated with high temperature may be an appropriate marker of fast magmatic rising representing a new sensitive tool for volcanic risks strategies.

Sources of groundwater contaminants in inhabited areas, located in complex geo-tectonic contexts, are often deeply interlocked, thus, making the discrimination between anthropic and natural origins difficult. In this study, we investigate the Peloritani Mountain aquifers (Sicily, Italy), using the combination of probability plots with concentration contour maps to retrieve an overall view of the groundwater geo-chemistry with a special focus on the flux of heavy metals. In particular, we present a methodology for integrating spatial data with very different levels of precision, acquired before and during the “geomatic era”. Our results depict a complex geochemical layout driven by a geo-puzzle of rocks with very different lithological natures, hydraulically connected by a dense tectonic network that is also responsible for the mixing of deep hydrothermal fluids with the meteoric recharge. Moreover, a double source, geogenic or anthropogenic, was individuated for many chemicals delivered to groundwater bodies. The concentration contour maps, based on the different data groups identified by the probability plots, fit the coherency and congruency criteria with the distribution of both rock matrices and anthropogenic sources for chemicals, indicating the success of our geostatistical approach.