Behavior of rare earth elements in an aquifer perturbed by CO2 injection: Environmental implications.

Three cubic-meters of CO2-saturated water was injected into a subsurface fractured aquifer in a post-mined area, using a push-pull test protocol. Groundwater samples were collected before and after CO2-injection to quantify geochemical changes. CO2-injection initially reduced the pH of water from 7.3 to 5.7, led to the enrichment of major ions (Ca2+, Mg2+, and alkalinity), and dissolved trace metals (including Fe, Mn, As, and Zn) in the groundwater. Rare earth elements (REE) and yttrium concentrations were also measured in these samples before and after CO2 perturbation, to evaluate their behavior. An enrichment of total Y plus REE (REY) occurred. REY fractionation was observed with higher heavy REE (HREE) enrichment compared to light REE (LREE), and significant variations in La/Yb and Y/Ho ratios were observed following CO2 perturbation. Enrichment by a factor of three was observed for Y, Lu, and Tm, and by nearly one order of magnitude for Dy and Yb. A geochemical model was used to evaluate the amount of REE aqueous ions complexed throughout the experiment. Modeling of the results showed that speciation of dissolved REE with carbonate, along with desorption from iron oxyhydroxide surface were the main factors controlling REE behavior. This study increases an understanding of dissolved REE behavior in the environment, and the potential use for applying iron oxides for REE recovery from mine drainages. Furthermore, the description of REE fractionation patterns may assist in surveying CO2 geological storage sites, surveying underground waste disposal sites, and for understanding the formation of ore deposits and fluid inclusions in geological formations.

Rapid migration of CO2-rich micro-fluids in calcite matrices.

The transport of supercritical fluids is a determining factor for several geological processes and fundamental in predicting natural resource accumulation and distribution. Calcite, ubiquitous in most geological environments, may contain supercritical CO2 trapped under the form of fluid inclusions that may move through grain boundaries affecting the rock physical properties. However, despite macroscopic evidence for this process, until recent it was not possible to characterize this process at the nano-scale due to the difficulty of such observations. In this study, we report nanometer-scale observations on calcite crystal surfaces and demonstrate that stress with absence of visible deformation produces fluid leakage from fluid inclusions. Atomic Force Microscopy scanning experiments on freshly cleaved calcite crystals containing visible fluid inclusions revealed the spontaneous formation of nanometer-scale hillocks on flat crystal terraces in only a few minutes, without evidence of surface dissolution. The fact the hillocks formed on flat surface in a short time was unexpected and suggests deposition of material from the inner crystal to the surface through small-scale fluid migration. We estimated the rate of this fluid mobility is by several orders of magnitude higher than the diffusion rate through vacancies estimated in calcite crystals showing that CO2-rich fluids through micro-pore and nano-pore spaces is in reality much higher than previously assumed using current predictive models.

Development of a biosensor for copper detection in aqueous solutions using an Anemonia sulcata recombinant GFP.

Fluorescent proteins from marine organisms represent potential candidates for biosensor development. In this paper, we described the isolation of a native green fluorescent protein from Anemonia sulcata and the cloning and purification of its equivalent as a recombinant protein in Escherichia coli. Furthermore, the spectroscopic behaviours of the native and recombinant GFPs were investigated as a function of Cu(2+), Cd(2+), Pb(2+) and Ni(2+) concentration. Our results suggest the high selectivity of both proteins at copper than the other metals and, for the recombinant protein, a great sensitivity at a very low concentration (0.1-1 µM). Moreover, starting from these data, using the combination of molecular biology techniques and optical setup, we developed a device for the detection of Cu(2+) in water solutions. The quenching effect detected with the device showed that the relative attenuation of the signal (0.46 ± 0.02 AU) was slightly larger than the data measured by fluorescence spectra (0.65 ± 0.03 AU). The good sensitivity in the span of two orders of the magnitude of Cu(2+) concentration, the fact that the instrument is made up of low-cost and sturdy parts and the selective quenching of rAsGFP to copper ions make this setup suited as a low cost, on-the-field, copper ion-specific biosensor.

Simultaneous determinations of zirconium, hafnium, yttrium and lanthanides in seawater according to a co-precipitation technique onto iron-hydroxide.

Very low concentrations (pg mL(-1) or sub-pg mL(-1) level) along with the high salinity are the main problems in determining trace metal contents in seawater. This problem is mainly considered for investigations of naturally occurring YLOID (Y and Lanthanides) and Zr and Hf in order to provide precise and accurate results. The inductively coupled plasma mass spectrometry (ICP-MS), both in high and low resolution, offers many advantages including simultaneous analyses of all elements and their quantitative determination with detection limits of the order of pg mL(-1). However in the analysis of YLOID in seawater, a better determination needs an efficient combination of ICP-MS measurement with a pre-concentration technique. To perform an ultra-trace analysis in seawater, we have validated an analytical procedure involving an improved modified co-precipitation on iron hydroxides to ensure the simultaneous quantitative recovery of YLOID, Zr and Hf contents with measurement by a quadrupole ICP-MS. The validity of the method was assessed through a series of co-precipitation experiments and estimation of several quality control parameters for method validation, namely working range and its linearity, detection limit, quantification limit, precision and spike recoveries, and the methodological blank choice, are introduced, evaluated and discussed. Analysis of NASS-6, is the first report on the latest seawater reference material for YLOID, hafnium and zirconium.

Source and nature of inhaled atmospheric dust from trace element analyses of human bronchial fluids.

Rapid volcanic eruptions quickly ejecting large amounts of dust provoke the accumulation of heavy metals in people living in surrounding areas. Analyses of bronchoalveolar lavage samples (BAL) collected from people exposed to the paroxysmal 2001 Etna eruption revealed a strong enrichment of many toxic heavy metals. Comparing the BAL to the dust composition of southeastern Sicily, we found that only V, Cr, Mn, Fe, Co, and U enrichment could be related to the volcanic event, whereas Ni, Cu, Cd, and Pb contents come from the dissolution of particles of anthropogenic origin. Furthermore, the nature of these inhaled anthropogenic particles was revealed by anomalous La and partially Ce concentrations in BAL that were consistent with a mixture of road dust and petroleum refinery emissions. Our results indicate that trace element distribution in BAL is a suitable tracer of human exposure to different sources of inhaled atmospheric particulates, allowing investigations into the origin of source materials inhaled by people subjected to atmospheric fallout.

Vertical bone augmentation versus 7-mm-long implants in posterior atrophic mandibles. Results of a randomised controlled clinical trial of up to 4 months after loading.

PURPOSE: To evaluate whether 7-mm-long implants could be a suitable alternative to longer implants placed in vertically augmented bone for the treatment of atrophic posterior mandibles. MATERIALS AND METHODS: Sixty partially edentulous patients having 7 to 8 mm of residual crestal height and at least 5.5 mm thickness measured on a computed tomography scan above the mandibular canal were randomised to receive either two to three submerged 7-mm-long NanoTite External Hex implants (Biomet 3i) or 10-mm or longer implants (30 patients per group) placed in vertically augmented bone. Bone was augmented with anorganic bovine bone blocks (Bio-Oss) using a sandwich technique and resorbable barriers. The grafts were left healing for 5 months before placing the implants, which were submerged. Four months after implant placement, provisional acrylic prostheses were delivered. Definitive screw-retained metal-ceramic prostheses were delivered 4 months later. Outcome measures were: prosthesis and implant failures, any complications, and time needed to fully recover mental nerve sensitivity. All patients were followed up to the delivery of the final restorations (4 months after loading). RESULTS: No patient dropped out. In two patients of the augmented group, there was not enough space to place 10-mm or longer implants as planned and 7-mm-long implants were used instead. The most likely reason for this is that the Bio-Oss blocks fractured in many pieces at placement. One prosthesis could not be placed when planned in the 7-mm group versus three prostheses in the augmented group, because of failure of one implant in each patient. The difference was not statistically significant. All implants were successfully replaced and final prostheses delivered. Four complications (wound dehiscence) occurred during graft healing in the augmented group (one possibly associated with the failure of one implant) versus none in the 7-mm-long implant group. The difference was not statistically significant. No patient suffered from permanent paraesthesia of the alveolar inferior nerve; however, sensitivity was recovered significantly faster in the short implant group. CONCLUSIONS: The early results of this study suggest that, when the residual bone height over the mandibular canal is between 7 and 8 mm, 7-mm short implants might be a preferable choice since the treatment is faster, cheaper and associated with less morbidity than vertical bone augmentation. These preliminary results must be confirmed by follow-ups of 5 years or more in order to monitor the performance of short implants over time.