Combination of stable isotope analysis and chemometrics to discriminate geoclimatically and temporally the virgin olive oils from three mediterranean countries

The knowledge of the isotopic composition of virgin olive oil (VOO) allows the evaluation of authenticity and geographical origin, being an important tool against fraud. This study aimed to assess if VOOs produced in three Mediterranean regions could be discriminated on the basis of multivariate statistical analysis of geoclimatic and isotopic data. A total of 138 geo-referenced VOO samples from Portugal, France and Turkey from two different cultivation years were collected. The isotopic composition (δ13C, δ2H and δ18O) of VOOs was obtained using an elemental analyzer coupled to an isotope ratio mass spectrometer (EA-IRMS). One-way analysis of variance for δ13C, δ2H and δ18O showed some significant differences either between crop years or geoclimatic conditions. Based on multiple regression analyses using meteorological and geographical parameters, a meteoric water line for olive oil from Portugal, France and Turkey, in two harvest years, were created to assess the impact of climate change on their δ2H and δ18O values. Principal component analysis and Linear Discriminant Analysis, used to sort samples according to geoclimatic origin, performed best for French and Portuguese olive oils. In light of the results, multivariate isotopic analysis of VOO samples may discriminate not only between geoclimatic regions but also among cultivation years

Pyrogenic organic matter from palaeo-fires during the Holocene: A case study in a sequence of buried soils at the Central Ebro Basin (NE Spain)

We studied the fire record and its environmental consequences during the Holocene in the Central Ebro Basin. This region is very sensitive to environmental changes due to its semiarid conditions, lithological features and a continuous human presence during the past 6000 years. The study area is a 6 m buried sequence of polycyclic soils developed approximately 9500 years ago that is exceptionally well preserved and encompasses four sedimentary units. The content and size distribution of macroscopic charcoal fragments were determined throughout the soil sequence and the analysis of the composition of charcoal, litter and sediments via analytical pyrolysis (Py-GC/MS). The high amount of charcoal fragments recovered in most horizons highlights the fire frequencies since the beginning of the Neolithic, most of which were probably of anthropogenic origin. In some soil horizons where charcoal was not found, we detected a distribution pattern of lipid compounds that could be related to biomass burning. On the other hand, the low number of pyrolysates in the charcoal could be attributed to high-intensity fires. No clear pattern was found in the composition of pyrolysates related to the age of sediments or vegetation type. The most ancient soil (Unit 1) was the richest in charcoal content and contains a higher proportion of larger fragments (>4 mm), which is consistent with the burning of a relatively dense vegetation cover. This buried soil has been preserved in situ, probably due to the accumulation of sedimentary materials because of a high-intensity fire. In addition, the pyrogenic C in this soil has some plant markers that could indicate a low degree of transformation. In Units 2–4, both the amount of charcoals and the proportions of macrofragments >4 mm are lower than those in Unit 1, which coincides with a more open forest and the presence of shrubs and herbs. The preservation of this site is key to continuing with studies that contribute to a better assessment of the consequences of future disturbances, such as landscape transformation and climate change

Pyrolysis-compound specific isotope analysis (Py-CSIA) of terrestrial analogue samples. Possible applications in astrobiology and geomicrobiology

Astrobiology greatly relies in cutting-edge analytical techniques to explore life in extreme conditions and eventually may help recognize different biospheres to that on Earth. This, in turn may allow us to better understand the origin of life on Earth and to investigate the possibility of life on other planets. Taking into account ongoing and upcoming planetary explorations, the detection of biosignatures in terrestrial analogue environments, such as lava tubes, hypersaline and acidic caves, appear extremely important. In this sense, the use of state-of-the-art techniques is of upmost importance for the accurate characterization of organic molecules preserved in minerals from planetary field analogue sites, such as in siliceous speleothems from lava tubes. Pyrolysis-compound specific isotopic analysis (Py-CSIA) is a cutting-edge method used to measure stable isotope composition (e.g, δ13C, δ15N and δ2H) in specific compounds released by pyrolysis. This technique combines analytical pyrolysis (Py-GC/MS) and isotope ratio mass spectrometry (IRMS) for characterizing the isotope composition of each individual compound separated by gas chromatography. It can provide valuable information on molecular fingerprinting of solid materials not amenable by conventional GC/IRMS techniques allowing traceability of formation processes and origin. The analysis can be done in small samples with minimum sample handling and pre-treatment minimizing the chance of contamination and artefacts. This technique is based on the coupling of an analytic pyrolyser to a gas chromatograph (GC) and using an isotope ratio mass spectrometer (IRMS) as detector. In short, the individual volatile pyrolysis products separated by gas chromatography are directed to a combustion (carbon and nitrogen) or a pyrolysis (hydrogen) micro-reactor and finally the isotope composition of the gases produced measured by IRMS via an appropriate interface. With this technique, it is possible to make measures of stable isotope composition in chromatographically separated compounds directly from solid samples (i.e. δ13C, δ15N, δ2H and δ18O). In this communication, we will introduce the Py-CSIA technique as a novel technique for the detection of bio-signatures and the direct determination of the isotopic composition of environmental samples from extreme and Mars analogue field sites. Case studies on lava tubes using Py-CSIA for the detection of biosignatures preserved in mineral deposits will be presented and the potential application in the field of astrobiology and geomicrobiology discussed

Pyrolysis Compound-Specific Isotope Analysis (Py-CSIA): a novel analytical approach for archaeological studies

The measurement of stable isotopes has become an important tool within the field of archaeology. The isotopic trace of human and animal tissues and components (bone, collage, keratin, muscle, fat etc.) allowed insight into the diet of our ancestors in a specific period of time, as well as its relationship with various human pathologies. Furthermore, this technique informs about food origin and possibly also their commercial routes, as well as population migrations. Pyrolysis-compound specific isotope analysis (Py-CSIA) is a cutting-edge analytical approach able to provide, not only a precise identification of organic compounds in different complex matrices, but also additional valuable information about nature and origin of the materials based on their isotope composition. This technique is based on the coupling of a micro-furnace pyrolysis unit to a gas chromatograph equipped with an isotope ratio mass spectrometer (IRMS) as detector. The individual volatile pyrolysis products separated by gas chromatography are directed to a combustion or pyrolysis micro-reactor (GC-Isolink system) and finally the isotope composition of the gases produced measured in a continuous flow IRMS via an interface unit. With this technique it is possible to make direct determinations of stable isotope ratios (i.e. δ13C, δ15N, and δ2H) of specific compounds with minimum sample handling and pre-treatment, thus minimizing the chance of contamination and artefacts productions. In this communication, we introduce the Py-CSIA technique into the field of archaeology by studying the direct determination of the isotopic composition of human skeletons buried in medieval necropolises from Center and South of Portugal