Modeling composition of Ca-Fe-Mg carbonates in a natural CO2 reservoir

Understanding the physical-chemical features of liquid, gas and solid phases in natural analogue reservoirs of Carbon Capture and Sequestration (CCS) site is fundamental as they can provide key data for building up both conceptual and numerical modeling of reaction path for gas-water-rock interaction in high pCO2 systems. The aim of this work is improve the knowledge about these processes, by employing appropriate methods for compositional data on a case study, focusing on the solid (minerals) phases. In the early eighties, the PSS1 well (Eastern Tuscany, Central Italy), drilled down to almost 5,000 m for oil exploration by ENI (Italian National Agency of Hydrocarbons), intercepted a high pressure (≈700 bar) CO2 reservoir at the temperature of 120 °C. The reservoir rocks in the fertile horizon, located at about 3,800 m, consist of altered volcanic deposits interbedded with gypsumdolomite- bearing evaporites (“Burano Formation”). Surveys for determining the actual paragenesis of volcanic rocks, carried out on the drill core samples, corresponded to the top of CO2 reservoir (3,864-3,871 m depths from surface on the PSS1 bore-well log). Quartz, Ca-Fe-Mg carbonates, clay minerals (illite and chlorite series) and Fe-Ti oxides were found as principal mineralogical phases. Electron Microprobe Analysis on the carbonates has allowed to recognize the presence of ankerite and calcites. Compositional data, related to atomic % content of Ca, Fe, and Mg in carbonates minerals, were transformed by using Isometric Log-Ratio balances, whilst the variability affecting the data pattern was investigated in simple binary diagrams. The stoichiometric substitution processes governing the presence of Ca, Fe and Mg in carbonates were modeled by using regression techniques in the new space defined by ilrs coordinates. Results have evidenced the different role of Fe and Mg in substituting or not Ca in both carbonate minerals of these CO2-bearing reservoir rocks

The isometric log-ratio (ilr)-ion plot: A proposed alternative to the Piper diagram

Abstract The Piper diagram has been a staple for the analysis of water chemistry data since its introduction in 1944. It was conceived to be a method for water classification, determination of potential water mixing between end-members, and to aid in the identification of chemical reactions controlling a sample set. This study uses the information gleaned over the years since the release of the Piper diagram and proposes an alternative to it, capturing the strengths of the original diagram while adding new ideas to increase its robustness. The new method uses compositional data analysis to create 4 isometric log-ratio coordinates for the 6 major chemical species analyzed in the Piper diagram and transforms the data to a 4-field bi-plot, the ilr-ion plot. This ilr-ion plot conveys all of the information in the Piper diagram (water mixing, water types, and chemical reactions) while also visualizing additional data, the ability to examine Ca2+/Mg2+ versus Cl-/SO42−. The Piper and the ilr-ion plot were also compared using multiple synthetic and real datasets in order to illustrate the caveats and the advantages of using either diagram to analyze water chemistry data. Although there are challenges with using the ilr-ion plot (e.g., missing or zero values zeros in the dataset must be imputed by positive real numbers), it appears that the use of compositional data analysis coupled with the ilr-ion plot provides a more in-depth and complete analysis of water quality data compared to the original Piper diagram

Exploration of geochemical data with compositional canonical biplots

The study of the relationships between two compositions is of paramount importance in geochemical data analysis. This paper develops a compositional version of canonical correlation analysis, called CoDA-CCO, for this purpose. We consider two approaches, using the centred log-ratio transformation and the calculation of all possible pairwise log-ratios within sets. The relationships between both approaches are pointed out, and their merits are discussed. The related covariance matrices are structurally singular, and this is efficiently dealt with by using generalized inverses. We develop compositional canonical biplots and detail their properties. The canonical biplots are shown to be powerful tools for discovering the most salient relationships between two compositions. Some guidelines for compositional canonical biplots construction are discussed. A geochemical data set with X-ray fluorescence spectrometry measurements on major oxides and trace elements of European floodplains is used to illustrate the proposed method. The relationships between an analysis based on centred log-ratios and on isometric log-ratios are also shown.Peer ReviewedPostprint (author's final draft

Modellizzazione delle variazioni composizionali delle specie dell’azoto (NH4 +, NO2 -, NO3 -) nelle acque di falda del Comune di Arezzo (Toscana)♦

Gli elementi chimici disciolti nelle acque continentali provengono dall’alterazione della crosta terrestre. L’acqua erode e dissolve i minerali delle rocce attraverso l’alterazione chimica avvalendosi del contributo dei gas presenti in atmosfera o nel sottosuolo. Il nitrato, una delle sostanze responsabili delle più gravi forme di inquinamento delle acque nei paesi in via di sviluppo, è un nutriente essenziale per la crescita delle piante e rappresenta un anello fondamentale del ciclo biogeochimico dell'azoto, in quanto viene prodotto dai batteri a partire dall'azoto atmosferico. In quantità eccessive il nitrato può essere dannoso per gli uomini e per gli animali. Elevati livelli di nitrato nell'acqua sono causati in larga misura dall'uso di fertilizzanti ricchi di nitrato e dal letame. In questo contesto, le condizioni redox delle acque naturali, che controllano la speciazione dei composti dell’azoto, sono altamente variabili perché controllate prevalentemente dall’attività biologica. In particolare, il bilancio fra i due processi dell’attività biologica, la fotosintesi e la respirazione (o decomposizione della sostanza organica), determina la presenza nel sistema di condizioni ossidanti o riducenti. I composti dell’azoto possono quindi essere considerati utili indicatori dello stato di salute di un acquifero superficiale. In questo lavoro sono analizzati i dati relativi ai tenori delle specie dell’azoto NH4 +, NO2 - e NO3 - relativi ad acque di falda campionate nell’area aretina nel corso della realizzazione dell’Atlante Geochimico delle Acque di Falda e di Scorrimento Superficiale del Comune di Arezzo. I dati sono analizzati proponendo nuove metodologie grafiche e numeriche per visualizzare lo stato del territorio nei confronti della pressione antropica come rilevata dal comportamento spaziale e temporale delle specie suddette

From vine to wine: data on 87Sr/86Sr from rocks and soils as a geologic and pedologic characterisation of vineyards

This data article describes the soils characterisation, bedrock geochemical composition and descriptive statistics of 87Sr/86Sr in wines, grape saps, labile fractions of soils (bio-available), whole soils, and bedrocks used to explore the Sr isotope conservation from rocks and soils to vine and wine. These data also describe the reproducibility of the isotopic composition of wine over four harvest years (2008–2011) on 11 selected experimental parcels (sampling point). The data reported in this paper are related to the research article (Braschi et al., 2018) [1]

A1 and A2a receptors mediate inhibitory rffects of adenosine on the motor activity of human colon

Experimental evidence in animal models suggests that adenosine is involved in the regulation of digestive functions. This study examines the influence of adenosine on the contractile activity of human colon. Reverse transcription-polymerase chain reaction revealed A(1) and A(2a) receptor expression in colonic neuromuscular layers. Circular muscle preparations were connected to isotonic transducers to determine the effects of 8-cyclopentyl-1,3-dipropylxanthine (DPCPX; A(1) receptor antagonist), ZM 241385 (A(2a) receptor antagonist), CCPA (A(1) receptor agonist) and 2-[(p-2-carboxyethyl)-phenethylamino]-5'-N-ethyl-carboxamide-adenosine (CGS 21680; A(2a) receptor agonist) on motor responses evoked by electrical stimulation or carbachol. Electrically evoked contractions were enhanced by DPCPX and ZM 241385, and reduced by CCPA and CGS 21680. Similar effects were observed when colonic preparations were incubated with guanethidine (noradrenergic blocker), L-732,138, GR-159897 and SB-218795 (NK receptor antagonists). However, in the presence of guanethidine, NK receptor antagonists and N(omega)-propyl-L-arginine (NPA; neuronal nitric oxide synthase inhibitor), the effects of DPCPX and CCPA were still evident, while those of ZM 241385 and CGS 21680 no longer occurred. Carbachol-induced contractions were unaffected by A(2a) receptor ligands, but they were enhanced or reduced by DPCPX and CCPA, respectively. When colonic preparations were incubated with guanethidine, NK antagonists and atropine, electrically induced relaxations were partly reduced by ZM 241385 or NPA, but unaffected by DPCPX. Dipyridamole or application of exogenous adenosine reduced electrically and carbachol-evoked contractions, whereas adenosine deaminase enhanced such motor responses. In conclusion, adenosine exerts an inhibitory control on human colonic motility. A(1) receptors mediate direct modulating actions on smooth muscle, whereas A(2a) receptors operate through inhibitory nitrergic nerve pathways