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Soil geochemistry is often investigated by considering a large number of variables, including major, minor and trace elements. Some of the variables are usually highly correlated due to coherent geochemical behaviour, but the effect of anthropic factors tends to increase data variability, sometimes obscuring natural relationships governing their distributions. In this framework it may be difficult to identify geochemical features linked to natural phenomena as well as to separate geogenic anomaly from the anthropogenic ones. Consequently the identification of background/baseline values may be seriously compromised. However, knowledge about these reference terms is fundamental to manage and protect natural resources on different scales. Moreover, adequate estimations of background/baseline values are possible only if a sufficient number of chemical analyses are stored in complex repositories. In this contribution the multi-element data archive of the Campania Region (Southern Italy) was explored from the CoDA (Compositional Data Analysis) multivariate perspective to characterise its structure. The archive contains abundance data of Al, As, B, Ba, Ca, Co, Cr, Cu, Fe, K, La, Mg, Mn, Mo, Na, Ni, P, Pb, Sr, Th, Ti, V and Zn (mg/kg) determined in 3535 new topsoils as well as information on coordinates, geology and land cover. Under CoDA the proportionality features of abundance data are fully taken into account enhancing their relative multivariate behaviour in the correct sample space. Results indicate that the structure of the whole matrix appears to be constituted by a core that geographically is mainly given by topsoils developed on volcanic materials and several outlier compositions whose origin is different. Anomalous compositions can originate from the robust barycentre all around when the following conditions are present: 1) high Na–K volcanic products, 2) limestones and dolostones with their terrigenous component, 3) flysch deposits or 4) fertiliser contribution. The (1 × D) robust barycentre of the whole dataset together with the variation array of the core represents the most frequent (1 × D) multi-element vector as well as the proportionality relationships among its components. It might be considered a compositional baseline.

The complex geodynamic evolution of Aeolian Arc in the southern Tyrrhenian Sea resulted in melts with some of the most pronounced along the arc geochemical variation in incompatible trace elements and radiogenic isotopes worldwide, likely reflecting varia

In 2017, a geochemical survey was carried out across the Commune of Santiago, a local administrative unit located at the center of the namesake capital city of Chile, and the concentration of a number of major and trace elements (53 in total) was determined on 121 topsoil samples. Multifractal IDW (MIDW) interpolation method was applied to raw data to generate geochemical baseline maps of 15 potential toxic elements (PTEs); the concentration-area (C-A) plot was applied to MIDW grids to highlight the fractal distribution of geochemical data. Data of PTEs were elaborated to statistically determine local geochemical baselines and to assess the spatial variation of the degree of soil contamination by means of a new method taking into account both the severity of contamination and its complexity. Afterwards, to discriminate the sources of PTEs in soils, a robust Principal Component Analysis (PCA) was applied to data expressed in isometric log-ratio (ilr) coordinates. Based on PCA results, a Sequential Binary Partition (SBP) was also defined and balances were determined to generate contrasts among those elements considered as proxies of specific contamination sources (Urban traffic, productive settlements, etc.). A risk assessment was finally completed to potentially relate contamination sources to their potential effect on public health in the long term. A probabilistic approach, based on Monte Carlo method, was deemed more appropriate to include uncertainty due to spatial variation of geochemical data across the study area. Results showed how the integrated use of multivariate statistics and compositional data analysis gave the authors the chance to both discriminate between main contamination processes characterizing the soil of Santiago and to observe the existence of secondary phenomena that are normally difficult to constrain. Furthermore, it was demonstrated how a probabilistic approach in risk assessment could offer a more reliable view of the complexity of the process considering uncertainty as an integral part of the results. Physical and Mathematic Science Faculty (Universidad de Chile); University of Chile [N/A1/2014]; FONDAP [15200001]; ICM [NC130065] Published version This work was supported by startup funds awarded to Linda Daniele and Claudia Cannatelli by the Physical and Mathematic Science Faculty (Universidad de Chile). Linda Daniele also acknowledges the partial use of funds from Program U-Apoya (N/A1/2014) of the University of Chile, FONDAP #15200001 (Centro de Excelencia en Geotermia de los Andes, CEGA) and ICM #NC130065 (Nucleo Milenio Trazadores de Metales, NMTM).

In this paper we present a comparison of statistical and spatial distributions between Pb, Cu and Zn concentration data and clr-transformed data of 3669 topsoil samples from the Campanian Region. Results show that both approaches, the classical univariate analysis and the compositional data analysis, are necessary to understand the real structure of the data and shed light on different aspects. In particular, the spatial distributions of concentration (‘raw’) data and clr-transformed data of the three elements differ completely. Raw data essentially represent a high anthropogenic impact, requiring an additional human health risk assessment for the three investigated elements. The information obtained by the clr-coefficient maps reveals the geogenic contribution to the element distribution. To better constrain the degree of contamination due to these potentially toxic elements and their impact on human health, we present an RGB composite map of Pb, Cu and Zn. This map unravels potential sources of contamination and locates the areas where concentrations exceed thresholds established by the Italian legislation.

Clinopyroxene and olivine are ubiquitous phases in Somma-Vesuvius (SV) volcanics and for the first time they were systematically studied in several products younger than 40ka. In this manuscript chemical compositions (major, trace and rare earth elements) of a large set of olivine and clinopyroxene crystals from selected rock samples are presented and discussed. Fourteen pumice samples from Plinian pyroclastic deposits as well as three scoriae and eight lava samples from inter-Plinian deposits were collected. A representative number of olivine and clinopyroxene crystals (n~50) were selected for each sample and analysed by electron microprobe and laser ablation inductively coupled plasma mass spectrometer, resulting in a large database, which is now available to the scientific community. All studied eruptive products contain olivine and clinopyroxene crystals spanning a wide range of compositions. Olivines show Fo content varying from 91 to 68, while clinopyroxenes display Mg# ranging from 93 to 71. In samples younger than A.D. 79, the more evolved (Mg#82–72) clinopyroxene crystals show clear Ca enrichment (~23.5–24.5wt% CaO) with respect to those from older samples (before-A.D.79, ~23–21wt% CaO). The results corroborate disequilibrium between olivine, clinopyroxene and the hosting melt, and an increasing role of carbonate assimilation in SV magma evolution in the last 2ka. The database here produced is thought as a share product that makes available mineral data and can be used for further studies by researchers to investigate geochemical evolution of the SV system.

This review paper is intended to be a guideline to novices on how to conduct research on silicate melt inclusions in volcanic environments, which analytical techniques are more suitable to gather the desired data and the major pitfalls scientist may encounter. Silicate melt inclusions (SMIs) are small quantities of silicate melt that are trapped in minerals during their growth or crystallization. They contain liquids formed in equilibrium with their host minerals and therefore record the liquid line of descent of magmatic systems. Upon trapping, SMIs become ideally closed to the surrounding environment, and behave as time capsules, giving important information about processes that originated magmas and the nature of their mantle source. A melt inclusions investigation is composed of several steps: (1) a detailed petrographic study to characterize and select representative SMIs, with the aim of identifying Melt Inclusions Assemblages (MIA), the only reliable tool to assess that SMIs obey Roedder's rules and have not re-equilibrated following entrapment; (2) a careful preparation of samples for re-heating experiments and microanalysis; (3) high temperature studies in order to homogenize the SMIs and be able to perform chemical analysis; (4) interpretation of SMIs data, which should always be compared with bulk rock composition and relevant experimentally derived liquid compositions. We suggest that the search for good SMI candidates for study will be achieved by good petrographic analysis of SMIs and detailed petrographic information (size, shape, appearance, position relative to the host and other SMI within the same host). If the goal of a SMIs study is to determine volatile concentrations, assessing the relative time of trapping among SMIs is of paramount importance, as it allows understanding if the variation in volatile concentrations is consistent with a certain magmatic physical–chemical process. Researchers that choose to work with SMIs face several challenges. SMIs are not always hosted in all samples or they can be difficult to recognize (mostly due to their small size). Additionally, due several processes, such as post-entrapment crystallization, boundary layer and sampling melt heterogeneity at the micron scale, they may not be representative of the original trapped melt composition.

This study presents the results of 12 trace elements that have been classified by Italian Environmental law as potentially dangerous to human health and new Pb isotope data for topsoils and soil profiles collected in the Casoria municipal area (Napoli). Elemental concentrations were determined in 126 topsoil samples and were produced interpolated distribution (MIDW) and baseline maps using GeoDAS software. Results show Casoria soils to be significantly enriched in several elements (e.g., Cd, Cu, Pb, Zn). Two geochemical sources were determined associating elemental distribution with the background values of Neapolitan soils: one geogenic and another one anthropogenic. High As, Co, Se and Tl concentrations are coherent with bedrock lithology, and elemental concentrations show the same values typical of Neapolitan volcanic soils. Higher Cd, Hg, Pb and Zn concentrations can be linked with anthropic activities coherent with previous studies in the Neapolitan area. Cr, Cu, Sb and V geochemical concentration and distribution shows both geogenic and anthropogenic influence. Pb isotope analyses allow the determination of the source of the Pb and the level of anthropogenic/geogenic influence on their concentration. Pb sources in the Casoria soils overlap the isotopic compositions typical of industrial soils/aerosols. This anthropic influence on Pb concentration is quantified by anthropogenic fraction (AF%). Casoria topsoil shows very high amount of anthropogenic Pb: AF% is 41–58 %. In profile soil samples leached (L) AF(%) is 31–43 % (topsoils) and 38–56 % (bottom soils); in profile soil samples residues (R) AF(%) is shifted toward the geologic signature, 18–43 % (topsoils) and 25–50 % (bottom soils). © 2016, Springer-Verlag Berlin Heidelberg.