Compound-specific Carbon Isotope Analysis Research Articles

Evidence of a significant marine plant diet in a Pleistocene caribou from Haida Gwaii, British Columbia, through compound-specific stable isotope analysis

The Northwest Coast of Canada was likely an important location for glacial refugia in the Late Pleistocene. Recently, a caribou (Rangifer tarandus) antler fragment was reported from Graham Island dating prior to the Fraser Glaciation (MIS 3; 48,200–45,200 cal yr BP). The high carbon and nitrogen stable isotope values found in the bulk collagen samples of this caribou prompted further investigation into its diet and palaeoecological context. Today, caribou in British Columbia face rapid population and range decline, and have been placed on threatened and endangered species lists by both the U.S. and Canadian governments. Further insights into this species and its responses to changing environmental conditions can both improve our understanding of the Late Pleistocene ecosystems of the Northwest Coast and add relevant data to modern conservation issues. We employed compound-specific carbon and nitrogen stable isotope analysis to the individual amino acids of antler collagen to better understand the isotopic signal of this specimen. Our results suggest a significant marine plant contribution to the caribou's spring–summer diet, potentially reflecting an intensive foraging behavior observed in some modern-day Rangifer tarandus populations under conditions of terrestrial resource restriction.

Dynamics of chlorinated aliphatic hydrocarbons in the Chalk aquifer of northern France

The Chalk aquifer used for drinking-water production in the southwest of the Lille European Metropolis is threatened by the presence of chlorinated aliphatic hydrocarbons (CHCs), their concentrations in groundwater regularly exceeding the regulatory limits for drinking water in France. This hinders its use for drinking-water production. Understanding the dynamics and spatial distribution of CHC in the aquifer is a key factor for resource sustainability. For that purpose, an intensive monitoring was undertaken in several well fields and at different depths over eight years. To assess a possible migration and/or degradation of the compounds, the water column in several wells was sampled at various depths with passive samplers. Furthermore, CHC degradation mechanisms were investigated with compound-specific carbon-isotope analysis. The CHC concentrations and their distributions in the area depend on past and current industrial activity, causing plumes emphasized by pumping in the wells, such plumes being multi-source with no identified origin in most wells. In the south area of Les Ansereuilles, reductive dechlorination of tetrachloroethylene from a former industrial laundry highly impacted the surrounding area with its main degradation product cis-1,2-dichloroethylene. The same area is also affected by tetrachlroroethylene from several industrial laundries, textile factories and dyeing industries with also an anaerobic degradation. In the northern part of Les Ansereuilles, tetrachloroethylene, trichloroethane, trichloroethylene and 1,1-dichloroethylene were found as primary products, whereas cis-1,2-dichloroethylene appears to be an anaerobic degradation product of TCE. The other well fields (Houplin-Ancoisne, Seclin and Emmerin) are less impacted by CHC pollution, and it was shown that no CHC degradation occurred in the wells. However, the stratification of CHCs in the well-water columns, their constant concentration values over time caused by the large amount of available CHCs, and the minor degradation occurring in wells are of concern for water operators in the future.

Patterns and compound specific stable carbon isotope analysis (δ13 C) of capsaicinoids in Cayenne chilli fruits of different ripening stages.

Capsaicinoids are alkaloids of high pungency which are exclusively formed by fruits of the genus Capsicum. Capsaicinoid content and composition of Capsicum fruits are influenced by ripening. Determination of changes in content and pattern of individual capsaicinoids in chilli pods with fruit ripening. Compound specific stable carbon isotope analysis (δ13 C values (‰), CSIA) was used for a better understanding of capsaicinoid development during fruit ripening. Cayenne chillies (Capsicum annuum) were grown in a glasshouse and harvested from different plants at four ripening stages (unripe, semi-ripe, ripe, overripe). Nine capsaicinoids (one verified by synthesis) were quantified by gas chromatography with mass spectrometry (GC-MS). For CSIA, an acetylation method for derivatising capsaicinoids was developed. Variations in the patterns of the nine capsaicinoids were not relatable to a distinct ripening stage and also total contents varied extensively from plant to plant. However, changes in total capsaicinoid concentrations were systematic. In almost all plants, maximum values were reached in unripe fruits, then decreased to semi-ripe samples and increased again in the following ripening process. Likewise, δ13 C values of individual capsaicinoids were always by ~2‰ heavier in unripe than in semi-ripe or ripe fruits. However, direction of changes in sum-δ13 C values (‰) (taking contributions of all capsaicinoids together) could not be explained by corresponding variations in capsaicinoid concentrations. Both quantification and δ13 C values (‰) verified the presence of ripening-related changes in the capsaicinoid content which may be caused by simultaneously proceeding reactions like synthesis, storage and degradation of capsaicinoids.

Source apportionment of PAHs in roadside agricultural soils of a megacity using positive matrix factorization receptor model and compound-specific carbon isotope analysis

Polycyclic aromatic hydrocarbon (PAH) contamination in agricultural soils (n = 41) along Shanghai road net was systematically investigated to characterize pollution distribution and to apportion sources. Total PAH (Σ16PAH) concentrations in roadside agricultural soils varied from 17.2 to 3775 ng/g with an average of 339 ± 594 ng/g, 43.9 % of which corresponded to weakly - heavily contaminated levels. The spatial distribution of pollution hotspots depended on heavy traffic volume and intensive industrial activities in adjacent areas. A positive matrix factorization receptor model identified that vehicle emission and combustion of coal, biomass and natural gas were the predominant sources, accounting for 66.0 % and 23.7 % of Σ16PAH loadings, respectively. Stable carbon isotope analysis was applied for the first time in seven sites with high Σ16PAH concentrations for tracing their unique sources. It was concluded that PAHs in the heavily contaminated soil site G18 predominantly came from vehicle emission sources, different from the six other sites controlled by coal-processing and biomass combustion sources. Future studies should focus on quantifying the source contribution of PAHs in roadside agricultural soils based on the combination of multi-isotope approaches due to the data overlap of δ13C in certain sources.

Compound-specific carbon and hydrogen isotope analysis of volatile organic compounds using headspace solid-phase microextraction

Natural flavouring materials are in high demand, and a premium price is paid for all-natural flavourings, making them vulnerable to fraud. At present, compound-specific isotope analysis (CSIA) is perhaps the most sophisticated tool for determining flavour authenticity. Despite promising results, the method is not widely used, and the results are limited to the most common volatile organic compounds (VOCs). This paper describes a robust protocol for on-line measurements of δ13C and δ2H using HS-SPME coupled with GC-C-IRMS and GC-HTC-IRMS for common fruit VOCs. To achieve reproducible and accurate results, a combination of a peak size/linearity correction with drift correction were used. Finally, the results were normalised by multiple point linear regression using the known and measured values of reference materials. Special care was taken to avoid irreproducible isotopic fractionation and the effects of equilibration, adsorption, desorption times and temperatures on δ13C or δ2H values were examined. Method validation was performed, and the average combined measurement uncertainty (MU) was 0.42‰. All the δ13CVPDB values were below ±3*MU, regardless of analytical conditions. In contrast, for δ2HVSMOW-SLAP values, only low temperature (30 °C) with equilibration time (15 min) and shorter adsorption time (between 10 and 20 min) can produce an isotopic difference of <10‰. Therefore, method optimisation can minimise MU, and data normalisation and method validation are essential for obtaining meaningful data for use in flavour authenticity studies.

Compound-specific carbon and nitrogen isotope analysis of amino sugars and their applications

Amino sugars (AS) are one of the important biochemical components in the natural organic matter pool. Clarifying the sources and transformations of AS would facilitate our understan-ding of the microbial regulation of organic matter. As an emerging technology, compound-specific isotope analysis of amino sugars (CSIA-AS) provides more detailed dynamic information of indivi-dual AS in natural environment. Here, we systematically summarized the determination methods of CSIA-AS and gave an overview on innovative applications in the cycling of AS. CSIA-AS can be performed by gas chromatography-isotope ratio mass spectrometry (GC-IRMS) and ion chromatography-isotope ratio mass spectrometry (IC-IRMS). Each method has its own advantages and disadvantages, but reliable results can be achieved after calibration. The mean residence time of AS is relatively low in soil organic matter, and the bacterial-derived muramic acid possesses a higher minera-lization rate than glucosamine, galactosamine, and mannosamine. The source and metabolic transformation of AS are affected by the substrate, which is related to the specific response of microbial community to different carbon and nitrogen sources. The promotion of CSIA-AS technology requires further optimization of method and integration with other approaches such as microbial screening to decipher the source, transformation, fate and regulatory mechanisms of organic matter.

Compound-specific carbon isotope analysis for mechanistic characterization of debromination of decabrominated diphenyl ether.

Decabrominated diphenyl ether (BDE-209) is a notorious persistent organic pollutant widely found in the environment. Developing a compound-specific isotope analysis (CSIA) method is much needed in order to trace its transport and degradation processes and to evaluate the effectiveness of the remediation of BDE-209 in the environment. However, the conventional CSIA method, i.e. gas chromatography (GC) combustion isotope ratio mass spectrometry, is not appropriate for BDE-209 because of its high thermal instability and incomplete combustion. We developed a high-performance liquid chromatography (HPLC) method for the separation and purification of BDE-209 that prevents its thermal reactivity as occurred in prior GC-based methods. The δ13 C value of the purified BDE-209 was determined using offline elemental analyzer isotope ratio mass spectrometry (EA/IRMS). This two-step method was applied to determine the δ13 C values of BDE-209 in two commercial samples and to characterize carbon isotope fractionation associated with the debromination of BDE-209 via nanoscale zero-valent iron. The mean values of daily δ13 C analyses of six replicates of a BDE-209 standard varied from -27.66‰ to -27.92‰, with a standard deviation ranging from 0.07‰ to 0.16‰, indicating a good reproducibility of EA/IRMS. The EA/IRMS analysis of the purified BDE-209 standard indicated no obvious isotope fractionation during the sample purification. The impurity content in commercial BDE-209 samples may contribute additional variation of the δ13 C values of BDE-209. The δ13 C values of BDE-209 gradually changed from -27.47 ± 0.37‰ to -24.59 ± 0.19‰ when 74% of the BDE-209 standard was degraded within 36 h. The estimated carbon isotope enrichment factor was -1.72 ± 0.18‰. The two-step method based on HPLC and EA/IRMS avoids the thermal instability of BDE-209 in the traditional CSIA method. It offers a novel approach for elucidating the degradation mechanisms of BDE-209 in the environment and for source identification in contaminated sites.

Molecular evidence of changing foodways across the Mississippian transition at the George Reeves site (11S650)

ABSTRACTThe George Reeves site (11S650) is a multicomponent village on the bluffs in the central American Bottom, Illinois. The site was occupied from the Late Woodland Rosewood phase through the Mississippian Lohmann phase. Pottery use and dietary variation between the Late Woodland and Emergent Mississippian occupations at the site were explored through stylistic analysis, pottery residue analysis, and compound-specific carbon isotopic analysis of pottery residues. Although more samples should be analyzed, diet and pottery use at George Reeves seems to have been varied, with maize present by cal AD 900–1000, but comprising a relatively small portion of lipid residues in pottery. Residue analysis indicates a C4 presence in 5 of 16 sampled pots from the early Emergent Mississippian deriving from either maize or from meat from animals consuming maize. Pottery residues were mixed, showing C3 and C4 plants as well as meat and fish or shellfish. One residue showed a high incidence of C4 contribution, most likely from Portulaca oleracea (common purslane), as well as large amounts of fish or shellfish and another C3 plant. Residue from a ceramic pipestem indicates that maize may have been smoked, probably in the form of maize silk mixed with other nontobacco plants.

Stable carbon isotope analysis of polyphosphonate complexing agents by anion chromatography coupled to isotope ratio mass spectrometry: method development and application.

Compound-specific carbon isotope analysis (carbon CSIA) by liquid chromatography/isotope ratio mass spectrometry (LC-IRMS) is a novel and promising tool to elucidate the environmental fate of polar organic compounds such as polyphosphonates, strong complexing agents for di- and trivalent cations with growing commercial importance over the last decades. Here, we present a LC-IRMS method for the three widely used polyphosphonates 1-hydroxyethane 1,1-diphosphonate (HEDP), amino tris(methylenephosphonate) (ATMP), and ethylenediamine tetra(methylenephosphonate) (EDTMP). Separation of the analytes, as well as ATMP and its degradation products, was carried out on an anion exchange column under acidic conditions. Quantitative wet chemical oxidation inside the LC-IRMS interface to CO2 was achieved for all three investigated polyphosphonates at a comparatively low sodium persulfate concentration despite the described resilience of HEDP towards oxidative breakdown. The developed method has proven to be suitable for the determination of carbon isotope fractionation of ATMP transformation due to manganese-catalyzed reaction with molecular oxygen, as well as for equilibrium sorption of ATMP to goethite. A kinetic isotope effect was associated with the investigated reaction pathway, whereas no detectable isotope fractionation could be observed during sorption. Thus, CSIA is an appropriate technique to distinguish between sorption and degradation processes that contribute to a concentration decrease of ATMP in laboratory batch experiments. Our study highlights the potential of carbon CSIA by LC-IRMS to gain a process-based understanding of the fate of polyphosphonate complexing agents in environmental as well as technical systems.

Compound Specific Carbon Isotope Analysis in Sake by LC/IRMS and Brewers\u2019 Alcohol Proportion

Sake is a traditional Japanese alcohol. Nowadays, the consumption for Sake is increasing in worldwide and its popularity is growing. However, there are act of fraudulence by additional brewers’ alcohol and sugar. Therefore, a method is needed to find illegal fraud on label. In this work, we analyzed the δ13C values of the ethanol (δ13Ceth) and glucose (δ13Cglu) in Sake by liquid chromatography combined with isotope ratio mass spectrometry for the first time. Further, we developed the criteria using δ13Ceth and δ13Cglu to check brewers’ alcohol and sugar. In addition, there are some sake categories (Ginjyo and Futsu-shu) allowed to additional brewers’ alcohol up to legally determined percentage. The experimental additions of brewers’ alcohol from a C4 plant were conducted to Junmai, as sake by C3 plants. There was a strong correlation (R = 0.98, P < 0.05) between the percentage of added brewers’ alcohol and the δ13C values. We developed the method using the relationship for calculating percentage of brewers’ alcohol for the first time and estimated the percentage for commercial sake. Further, the price of sake was found to be inversely related to the percentage of brewers’ alcohol in the sake.

N-Alkyl nitriles and compound-specific carbon isotope analysis of lipid combustion residues from Neanderthal and experimental hearths: Identifying sources of organic compounds and combustion temperatures

Molecular and isotopic approaches offer the chance to identify combustion residues and substrate components of archaeological combustion features to infer past fire-related activities. Analysis of fatty acid methyl esters by gas chromatography-combustion-isotope ratio mass spectrometry have been successfully used to distinguish among different animal fat groups. However, plant oils from different tissues have not been widely investigated even though organic residues from leaf, root, and wood tissues are preserved in sediments from archaeological combustion structures. Our analyses of plant residues from controlled laboratory heating sequences and experimental hearths involving wood and animal residues, provide references to discern anatomical parts of fresh and charred plants and to differentiate contributions of terrestrial plants and animal sources in open air hearths. This information is compared with charred organic residues from combustion structures from three Middle Palaeolithic sites: El Salt (Spain), Abric del Pastor (Spain) and Crvena Stijena (Montenegro). The occurrence of n-alkyl nitriles in our samples corroborates their potential as combustion temperature biomarkers and the δ13C16:0 and δ13C18:0 values allow us differentiate between charred and fresh plant anatomical parts and between fresh plant oils and animal fats.

Simultaneous total analysis of core and polar membrane lipids in archaea by high-performance liquid chromatography/high-resolution mass spectrometry coupled with heated electrospray ionization.

Archaea have characteristic membrane lipids including diether and/or tetraether isoprenoidal core lipids with various polar head groups. Since the polar group is removed soon after the end of archaeal activity, the occurrences of core and polar lipids are regarded as dead and active signals, respectively. The core and polar lipids have generally been analyzed separately using atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI), respectively, coupled with mass spectrometry. In this study, simultaneous analyses of core and polar archaeal lipids have been examined using heated electrospray ionization (HESI) by high-performance liquid chromatography/high-resolution mass spectrometry (HPLC/HRMS). Both core and intact polar lipids can be analyzed simultaneously by HESI with good sensitivity (sub ng to 100 ng) and separation using a semi-bore diol column by normal-phase chromatography. The core lipids eluted firstly to separate archeaol, then glycerol dibiphytanyl glycerol tetraethers (GDGTs), followed by the polar lipids with glycosides and glycophosphates. The relative GDGT composition is identical between HESI and APCI methods. The simultaneous analysis has the benefit of minimizing sample amount and elution solvent as well as preparation work. The method can also be applied to a compound class fractionation for compound-specific carbon and hydrogen isotope analysis.

Assessing the source of oil deposited in the surface sediment of Mormugao Port, Goa - A case study of MV Qing incident

In June 2016, a cruise vessel was grounded in the Mormugao Port, resulting in unnoticed oil spill. The surface water and sediment samples were collected from the vicinity of the ship, and also an oil sample from the ship (OIL). These samples were subject to petroleum biomarker such as pentacyclic triterpenes (hopanes) and compound specific carbon isotopic (δ13C) analyses to assess the source of hydrocarbon pollution in the Mormugao Port. While no clear trend was observed in water samples, the bottom surface sediments did show an identical pattern of hopanes with the oil. The chemometric analyses of hopane Diagnostic Ratios (DRs) and δ13C ratios confirmed the ship oil as the source of oil pollution in sediments. Whereas the water is comparatively more dynamic than the sediment, the physical processes arising out of winds, waves, tides and currents might have dispersed the oil away from the grounded ship.

Development of a Purification Method for Compound Specific Carbon Isotope Analysis of Phytosterols and Long-chain &lt;i&gt;n&lt;/i&gt;-fatty Acids in Higher Plants

Development of a Purification Method for Compound Specific Carbon Isotope Analysis of Phytosterols and Long-chain &lt;i&gt;n&lt;/i&gt;-fatty Acids in Higher Plants

Toluene biodegradation in the vadose zone of a poplar phytoremediation system identified using metagenomics and toluene-specific stable carbon isotope analysis

Biodegradation is an important mechanism of action of phytoremediation systems, but performance evaluation is challenging. We applied metagenomic molecular approaches and compound-specific stable carbon isotope analysis to assess biodegradation of toluene in the vadose zone at an urban pilot field system where hybrid poplars were planted to remediate legacy impacts to an underlying shallow fractured bedrock aquifer. Carbon isotope ratios were compared spatio-temporally between toluene dissolved in groundwater and in the vapor phase. Enrichment of 13C from toluene in the vapor phase compared to groundwater provided evidence for biodegradation in the vadose zone. Total bacterial abundance (16S rRNA) and abundance and expression of degradation genes were determined in rhizosphere soil (DNA and RNA) and roots (DNA) using quantitative PCR. Relative abundances of degraders in the rhizosphere were on average higher at greater depths, except for enrichment of PHE-encoding communities that more strongly followed patterns of toluene concentrations detected. Quantification of RMO and PHE gene transcripts supported observations of active aerobic toluene degradation. Finally, spatially-variable numbers of toluene degraders were detected in poplar roots. We present multiple lines of evidence for biodegradation in the vadose zone at this site, contributing to our understanding of mechanisms of action of the phytoremediation system.

Carbon isotope fingerprinting palaeo fluid inclusion gases using a crushing-trapping technique

Carbon isotope fingerprinting has been widely used to study gas origin, maturity and gas-source correlations. However, natural gas accumulation in gas reservoirs can be affected by secondary alteration processes. In contrast, palaeo gases trapped in fluid inclusions (FIs) are free of any secondary alterations that may have occurred in the reservoir. FIs are normally less than 10 um in diameter, hence the gases trapped are at trace level amounts. An online crushing-trapping system has been developed in this study which enabled carbon isotope analyses of hydrocarbon gases which are normally in low concentrations. The crushing-trapping system mainly comprises of a gas-tight crusher and a gas concentrator interface module. The micro-trap is a critical part of the gas concentrator as it collects and concentrates all the released FI gases which results in sharp chromatographic peaks. This novel design is very sensitive, making it an increased challenge to obtain an acceptable blank before running samples. A clean blank is very important for such trace-level gas analysis. System blank results show that there are no hydrocarbon gases but trace amounts of CO2 (20 mV) detected in the blank. These trace amounts of CO2 in the blank have no influence on the carbon isotope calculation. It was found that no isotope fractionation was attributable to the cryo-trapping and subsequent thermal release from the trap but there is fractionation due to re-absorption onto the freshly crushed rock matrix (quartz or calcite) powder.Compound specific carbon isotope analysis of hydrocarbon gases (C1-C5 except M-C4) and CO2 released from a FI sample from the Cooper-Eromanga Basin was achieved for the first time as a proof of concept of the technique. Preliminary research on FI gases has been carried out in the Browse Basin, Australia.

Compound-Specific Carbon Isotope Compositions of Aldehydes and Ketones in the Murchison Meteorite.

Compound-specific carbon isotope analysis (δ13C) of meteoritic organic compounds can be used to elucidate the abiotic chemical reactions involved in their synthesis. The soluble organic content of the Murchison carbonaceous chondrite has been extensively investigated over the years, with a focus on the origins of amino acids and the potential role of Strecker-cyanohydrin synthesis in the early solar system. Previous δ13C investigations have targeted α-amino acid and α-hydroxy acid Strecker products and reactant HCN; however, δ13C values for meteoritic aldehydes and ketones (Strecker precursors) have not yet been reported. As such, the distribution of aldehydes and ketones in the cosmos and their role in prebiotic reactions have not been fully investigated. Here, we have applied an optimized O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) derivatization procedure to the extraction, identification and δ13C analysis of carbonyl compounds in the Murchison meteorite. A suite of aldehydes and ketones, dominated by acetaldehyde, propionaldehyde and acetone, were detected in the sample. δ13C values, ranging from -10.0‰ to +66.4‰, were more 13C-depleted than would be expected for aldehydes and ketones derived from the interstellar medium, based on interstellar 12C/13C ratios. These relatively 13C-depleted values suggest that chemical processes taking place in asteroid parent bodies (e.g. oxidation of the IOM) may provide a secondary source of aldehydes and ketones in the solar system. Comparisons between δ13C compositions of meteoritic aldehydes and ketones and other organic compound classes were used to evaluate potential structural relationships and associated reactions, including Strecker synthesis and alteration-driven chemical pathways.

From supratidal to subtidal, an integrated characterisation of Carbla Beach shallow microbial mats (Hamelin Pool, Shark Bay, WA): Lipid biomarkers, stable carbon isotopes and microfabrics

Modern microbial mats from Shark Bay are commonly regarded as robust analogues for Precambrian stromatolites. These microbial mats are complex ecosystems that exhibit intense biogeochemical recycling. In this study, a multi-proxy approach (including lipids, compound-specific carbon isotope analysis and petrography) is used to characterise microbial communities in three different types of mats (tufted, pustular and smooth) along the shallowest section of a tidal flat gradient. Cyanobacterial lipids were present in all three mats. Petrographical (optical and scanning electron microscopy) investigations also revealed that ooids in the tufted mat were larger and more common compared to the pustular and smooth mats. Biomarkers specific to sulfate reducing bacteria were detected in all mats. The diatom-specific C25:1 highly branched isoprenoid (HBI) alkene was most abundant in the smooth mat. However, imaging revealed that the smooth mat only contained rare diatoms of small size (~10 μm), whereas the pustular mat contained a variety of larger diatoms (~50 μm). The C25:1 HBI alkene marker is only produced by four diatom genera, which were most likely more represented in the smooth mat. Additionally, the smooth mat contained a greater contribution from aquatic macrophytes (Paq = 0.38) compared to the shallower mats, which is corroborated by the presence of 13C-enriched seagrass lipids (i.e. C29 steradiene). In all the mats, a major eukaryotic contribution was revealed via imaging techniques and supported by a high sterol content. This eukaryotic component (e.g. benthic foraminifera, diatoms) can impact the cohesive structure of the mats, the lithification processes and the lipid distribution, potentially complicating comparisons with Precambrian microbialites that were not affected by eukaryotic activity. This study reemphasizes the complexity of microbial ecosystems, and therefore highlights the benefit of multi-proxy approaches to characterise these biological systems.

Identification of Degradation Pathways of Chlorohydrocarbons in Saturated Low-Permeability Sediments Using Compound-Specific Isotope Analysis.

This study aims to investigate whether compound-specific carbon isotope analysis (CSIA) can be used to differentiate the degradation pathways of chlorohydrocarbons in saturated low-permeability sediments. For that purpose, a site was selected, wherea complex mixture of chlorohydrocarbons contaminated an aquifer-aquitard system. Almost 50 years after contaminant releases, high-resolution concentration, CSIA, and microbial profiles were determined. The CSIA profiles showed that in the aquitard cis-dichloroethene (cDCE), first considered as a degradation product of trichloroethene (TCE), is produced by the dichloroelimination of 1,1,2,2-tetrachloroethane (TeCA). In contrast, TeCA degrades to TCE via dehydrohalogenation in the aquifer, indicating that the aquifer-aquitard interface separates two different degradation pathways for TeCA. Moreover, the CSIA profiles showed that chloroform (CF) is degraded to dichloromethane (DCM) via hydrogenolysis in the aquitard and, to a minor degree, produced by the degradation of carbon tetrachloride (CT). Several microorganisms capable of degrading chlorohydrocarbons were detected in the aquitard, suggesting that aquitard degradation is microbially mediated. Furthermore, numerical simulations reproduced the aquitard concentration and CSIA profiles well, which allowed the determination of degradation rates for each transformation pathway. This improves the prediction of contaminant fate in the aquitard and potential magnitude of impacts on the adjacent aquifer due to back-diffusion.

The role of pottery in Middle Neolithic societies of western Mediterranean (Sardinia, Italy, 4500-4000 cal BC) revealed through an integrated morphometric, use-wear, biomolecular and isotopic approach

The use of pottery in the Early Neolithic communities of Western Mediterranean has begun to be addressed by recent studies concerning the residues of dietary commodities in potsherds. In order to contribute to a broader perspective on the issue of pottery function, we investigate pottery assemblages through an integrated methodology, combining the study of vessel morphology and morphometry, use-wear analysis, biomolecular and compound-specific carbon isotopic analysis of residues. We focus on the use of pottery containers by advanced Middle Neolithic societies of Sardinia (Italy, 4500-4000 cal BC), protagonists of significant technical, economic and cultural changes in the completion of Neolithisation in this island. The aims are to elucidate the role of whole pottery assemblages in technical and socioeconomic systems of Middle Neolithic communities and to provide data on the exploitation of animal and plant resources during this phase.Based on the integrated combination of data, six categories of vessel use are identified. The results reveal a differential integration of vessels in activities related to the exploitation of distinct kinds of resources (ruminant adipose/dairy fats and plant foods vs. non-ruminant and aquatic products) and highlight specific behaviours of Middle Neolithic societies in selecting pottery morphotypes for different uses, notably in processing products with heating.