Search

Pyrolysis-GC/MS is increasingly used to quantify microplastics (MP) in environmental samples. In general, prior to analysis, purification steps are carried out to reduce the environmental matrix in sediment samples. The conventionally used protocol of density separation followed by digestion of organic matter does not allow for complete isolation of MP from the associated organic and mineral matter. Among the pyrolysis products used as indicator compounds for plastic polymers, some may originate from other substances present in the environmental samples. In this paper, the indicator compounds are reviewed for the most common polymers: PE, PP, PS, PET and PVC and selected taking into account potential interactions with substances present in environmental matrices. Even after a purification step, a residual mineral fraction remains in a sediment sample, including matrix effects. This effect may be positive or negative, depending on the investigated polymer and is thus important to consider when using Pyr-GC/MS for the quantification of MP in sediment samples. It also shows that no external calibration can be used to reliably quantify MP in such samples and that the use of internal standards is compulsory. [ABSTRACT FROM AUTHOR]

In a Siberian river, the concentrations of chemical species vary with the hydrological regime. Dissolved Organic Matter (DOM) and aluminum ions show a parallel trend in the course of the hydrological year. However, the speciation of aluminum in this natural environment remains an open question. We propose here a combination of spectroscopic techniques to investigate the proximity between the aluminum atoms and DOM. First, one-dimensional (1D) solid-state Nuclear Magnetic Resonance (NMR), Electron Paramagnetic Resonance (EPR) and 1D and 2D solution NMR spectra were acquired, providing a clear overview of the DOM composition. Second, the sensitivity enhancement yielded by Dynamic Nuclear Polarization enabled the NMR detection of proximities between the 27 Al and 13 C nuclei. Hence, we show that 8.3 ± 1.3% of the carboxylate groups observed by NMR are connected to the Al 3 + ions in the DOM sample. We here demonstrate for the first time how advanced solid-state NMR methods can provide key information about the localization of aluminum in such complex natural materials. [ABSTRACT FROM AUTHOR]

The fate of leaf lipids upon early diagenesis was monitored in a two year litterbag experiment in a soil and at the water-sediment interface of an adjacent pond. The biomarker content of degrading leaves exhibited substantial variability among litterbags, even for a given time step within a given environmental condition, likely reflecting natural microenvironmental variability. Due to this variability and the oxic conditions in the pond, no substantial difference between the soil and the pond could be evidenced in the biomarker degradation pattern. An occasional increase in the abundance of several biomarkers (β- sitosterol, oleanolic acid, C 16 phytyl ester, C 27 n -alkane) was also noted during the experiment, which was attributed to release of bound compounds and/or an external contribution. Nevertheless, absolute quantification showed that the concentration of all lipid constituents was reduced, but they exhibited different decay profiles: (i) rapid extensive degradation (phytyl ester), (ii) exponential-like decrease (fatty lipids) and (iii) variable degradation profile (polycyclic triterpenoids). However, all the main constituents initially present in the senescent leaves were still detected after two years of degradation in both environments. Fatty lipids abundances generally decreased to < 10% of the initial content but the main distribution features (carbon number maximum and predominance) remained unchanged. The results thus tend to validate their use as proxy for source and environment in ancient organic matter. They also suggest that, on a mid-term basis, a plant biomarker signature is not substantially affected by differential degradation in soil and at the water-sediment interface, at least for a qualitative approach. [ABSTRACT FROM AUTHOR]

Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are a family of bacterial lipids which have emerged over time as robust temperature and pH paleoproxies in continental settings. Nevertheless, it was previously shown that other parameters than temperature and pH, such as soil moisture, thermal regime or vegetation can also influence the relative distribution of brGDGTs in soils and peats. This can explain a large part of the residual scatter in the global brGDGT calibrations with mean annual air temperature (MAAT) and pH in these settings. Despite improvements in brGDGT analytical methods and development of refined models, the root-mean-square error (RMSE) associated with global calibrations between brGDGT distribution and MAAT in soils and peats remains high (∼5 °C). The aim of the present study was to develop a new global terrestrial brGDGT temperature calibration from a worldwide extended dataset (i.e. 775 soil and peat samples, i.e. 112 samples added to the previously available global calibration) using a machine learning algorithm. Statistical analyses highlighted five clusters with different effects of potential confounding factors in addition to MAAT on the relative abundances of brGDGTs. The results also revealed the limitations of using a single index and a simple linear regression model to capture the response of brGDGTs to temperature changes. A new improved calibration based on a random forest algorithm was thus proposed, the so-called random F orest R egression for Pale O MAAT using br G DGTs (FROG). This multi-factorial and non-parametric model allows to overcome the use of a single index, and to be more representative of the environmental complexity by taking into account the non-linear relationships between MAAT and the relative abundances of the individual brGDGTs. The FROG model represents a refined brGDGT temperature calibration (R 2 = 0.8; RMSE = 4.01 °C) for soils and peats, more robust and accurate than previous global soil calibrations while being proposed on an extended dataset. This novel improved calibration was further applied and validated on two paleo archives covering the last 110 kyr and the Pliocene, respectively. [ABSTRACT FROM AUTHOR]

Background: MOSKI KIT® is a fun tool designed to interest children for prevention and management of malaria. This study was carried out with the objective to assess the short- and long-term impacts of this tool on the knowledge, attitudes, and practices of school children, and on the transmission of the knowledge received at the household level as well. Method: The study took place in elementary schools in the city centre (with relatively low endemicity) and in the Niayes area (at high risk of anopheline and malaria) in the Dakar region of Senegal. The various schools chosen for this study were divided into an intervention group and a control group. The intervention schools were also divided into two subgroups, a full package subgroup and another partial package. During this study three surveys were conducted, the first one before exposure to the MOSKI KIT®, the second one a week later and the third a year later. For the control schools only one survey was conducted and at the same time than the third for the intervention schools. Two household surveys (a week and a year after exposure) were also conducted for the intervention schools against one for the control schools. Results: Before sensitization, the proportion of school children with a grade above or equal to the average was 50% for the complete package subgroup (CPS) and 53% for the partial package subgroup (PPS). A week later, these proportions were 69% and 71%, respectively for the complete and PPSs. A year later, they were 99.4% for the CPS, 98.1% for the PPS and 99.5% for the control group; The number of children who spoke to their parents about malaria was greater in intervention schools than that of control schools. They were 46.63% and 32.58%, respectively in intervention and control schools. Conclusion: The MOSKI KIT, has enabled an increase of the knowledge of school children about malaria in the short term and favoured its retention in the long term. However, its impact was not felt on their attitudes and practices. [ABSTRACT FROM AUTHOR]

• 3-OH FAs and brGDGTs analyzed in soils from an altitudinal transect in the French Alps. • Investigation of the environmental factors controlling the distribution of bacterial lipids. • Influence of soil traits predominant over MAAT. • Statistical identification of the individual bacterial lipids influenced by MAAT/pH required. • Development of local calibrations with MAAT and pH based on such identification. Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are a family of bacterial lipids widely used for temperature and pH reconstructions in terrestrial settings. 3-hydroxy fatty acids (3-OH FAs) with 10–18 carbon atoms, produced by Gram-negative bacteria, have been recently proposed as independent and complementary proxies of temperature and pH in terrestrial environments. Nevertheless, the correlations between mean annual air temperature (MAAT)/pH and bacterial lipid (brGDGTs/3-OH FAs) distributions show a large degree of scatter, as the relative abundance of these lipids is influenced by factors other than temperature and pH. A full understanding of the environmental parameters influencing bacterial lipid distribution in soils is required to increase the reliability of the temperature and pH proxies based on these compounds in terrestrial environments. The aim of this work was to determine and quantify the cumulative effect of environmental parameters on the distribution of both brGDGTs and 3-OH FAs along a well-documented composite altitudinal transect in the French Alps (234–2748 m). Redundancy analysis revealed that the influence of local parameters (pH and to a lesser extent, soil moisture and grain size, related to vegetation and soil types) on brGDGT and 3-OH FA distributions amounted to 48.1% and 26.1%, respectively, and was predominant over MAAT. This likely explained the weak or lack of relationships between MAAT and brGDGT-/3-OH FA-based indices in this region. The identification of lipids whose fractional abundance is correlated with MAAT or pH allowed the development of local calibrations with MAAT/pH applicable in the French Alps, which are representative of highly contrasted microenvironments, reflecting different types of soil and vegetation. The present study highlighted the importance of constraining the environmental factors affecting the distribution of 3-OH FAs and brGDGTs in terrestrial settings prior to any paleoenvironmental reconstruction. Such an approach should be reproduced in other sites, where local factors could also strongly influence the bacterial lipid distribution. [ABSTRACT FROM AUTHOR]

During glacial terminations, the role of cross-equatorial currents in the northward spreading of warm and salty waters is essential to the reach of the following interglacial state. In the western tropical Atlantic, where the interhemispheric North Brazil Current develops, most of the existing temperature records focused on the last deglaciation. Here, using a marine sediment core covering the last 305 kyr before present (BP), we present two records of the surface (mixed layer) and the subsurface (upper thermocline) temperatures based on organic proxies UK' 37 and TEXH 86 , respectively. During the last three glacial terminations, these records exhibit large temperature increases especially in the subsurface layer. We suggest the combined influences of the thermal bipolar seesaw and the Agulhas Leakage, acting together to warm the interior South Atlantic, to explain the strong warming of the tropical western Atlantic thermocline (+5 °C) during these periods of reduced Atlantic meridional overturning circulation (AMOC). In addition, we propose an enhanced cross-equatorial gyre to elucidate the synchronous deglacial warming of the western and eastern sides of the tropical Atlantic. The resumption of the AMOC at the onset of the following interglacial leads to the release of heat stored in thermocline waters mainly in the whole South Atlantic, as highlighted by the sharp upper ocean cooling recorded at the end of the deglacial interval. The combination of this temperature record and previously published ones in the western tropical Atlantic confirms the strong sensitivity of the upper ocean to AMOC changes in this region. • UK' 37 -SST and TEXH 86 -SubT temperatures were reconstructed over the last 305 kyr BP. • Large subsurface warmings were highlighted over the last three deglaciations. • The thermal bipolar seesaw model explains part of the temperature increase. • Agulhas Leakage waters also contributed to the warming. • An intensified cross-equatorial gyre explains the deglacial spreading of warm waters. [ABSTRACT FROM AUTHOR]

A panel of geochemical techniques is used here to investigate the taphonomy of fossil feathers preserved in association with the skeleton of the Jurassic theropod Anchiornis huxleyi. Extant feathers were analysed in parallel to test whether the soft tissues morphologically preserved in the fossil also exhibit a high degree of chemical preservation. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) indicate that clays and iron oxide pseudomorphs occur in the surrounding sediment and also reveal the preservation of melanosome‐like microbodies in the fossil. Carbon gradient along a depth profile and co‐occurrence of carbon and sulphur are shown in the fossil by elastic backscattering (EBS) and particle‐induced x‐ray emission (PIXE), which are promising techniques for the elemental analysis of fossil soft tissues. The molecular composition of modern and fossil soft tissues was assessed from micro‐attenuated total reflectance fourier transform infrared spectroscopy (micro‐ATR FTIR), solid‐state 13C nuclear magnetic resonance (CP‐MAS 13C NMR) and pyrolysis gas chromatography mass spectrometry in the presence of TMAH (TMAH‐Py‐GC‐MS). Results indicate that the proteinaceous material that comprises the modern feathers is not present in the fossil feathers. The fossil feathers and the embedding sediment exhibit a highly aliphatic character. However, substantial differences exist between these samples, revealing that the organic matter of the fossil feathers is, at least partially, derived from original constituents of the feathers. Our results suggest that, despite the morphological preservation of Anchiornis feathers, original proteins, that is keratin, were probably not preserved in the 160‐myr‐old feathers. [ABSTRACT FROM AUTHOR]

Estuaries are important ecosystems from environmental and economical point of views and are the place of numerous transformations of organic matter (OM) during the transfer from land to the ocean. The dynamics of OM in estuarine systems is complex and was only rarely investigated at the structural or molecular level, even though OM transformation in the estuarine aquatic and sediment compartments involves processes taking place at this level. The aim of this study was to constrain the sources and fate of the OM in the Seine Estuary, one of the largest estuaries in France. The spatiotemporal dynamics of the OM along the estuary was investigated by comparing the bulk (elemental and isotopic composition) and structural (solid state 13C nuclear magnetic resonance) features of the different pools of OM – dissolved OM (DOM), particulate OM (POM) and sediment OM collected during five sampling campaigns. Reverse osmosis coupled with electrodialysis (RO/ED) was used to concentrate and isolate DOM, yielding an average organic carbon recovery of 59% (± 15%). RO/ED had a limited effect on DOM properties, DOM showing >75% of similarity with initial estuarine samples based on 3D fluorescence measurements. Bulk and structural analyses of DOM, POM and sedimentary OM showed that OM is mainly of aquatic origin in the Seine Estuary, regardless the OM pool. Nevertheless, significant differences in chemical composition between the three OM pools were observed: higher C/N ratios, carbohydrate, lipid and protein content as well as lower char and lignin contents in DOM than in the other two compartments. Spatial variations of OM properties, for POM and to a lesser extent DOM, were observed along the Seine Estuary based on δ13C and Δ14C analyses and 13C NMR-derived protein and lipid contents, showing the transition from a riverine to a marine-dominated system. In the mixing zone of the estuary, the Δ14C composition of the sediment OM was related to the tidal strength, with strong tides leading to the resuspension of recent sediment OM and weak tides allowing the deposition of recent aquatic OM. Altogether, the combination of bulk and structural techniques showed that the Seine Estuary OM quality is mainly related to the compartment (DOM/POM/sediment) and to a lesser extent to the sampling zone (upstream/maximum turbidity zone/downstream). The approach proposed for the characterization of the Seine Estuary OM could be applied to other estuaries, allowing a better understanding of the complex OM dynamics in such ecosystems. • Sources and fate of Seine Estuary organic matter (OM) investigated. • Dissolved, particulate and sediment OM mainly of recent aquatic origin. • River-dominated (recent DOM/POM) vs. marine-dominated (old DOM/recent POM) zones. • 13C NMR-based Protein/Lignin ratio promising proxy to discriminate OM sources. • OM quality mainly related to the compartment and secondly to the sampling zone. [ABSTRACT FROM AUTHOR]

Highlights • 3-hydroxy fatty acids analysed in soils from two contrasting altitudinal transects. • Distribution of 3-hydroxy fatty acids correlated with air temperature and soil pH. • Promising pH and temperature proxies in terrestrial environments. Abstract Three hydroxy (3-OH) fatty acids (FAs), containing 10 to 18 C and a hydroxyl group in third position are characteristic components of Gram-negative bacteria. These compounds were used previously to detect and quantify Gram-negative bacterial communities in various types of samples, from terrestrial, aquatic and atmospheric environments. The relative abundance of 3-OH FAs in soils was recently shown to vary with mean annual air temperature (MAAT) and pH in soils from Mt. Shennongjia (China). In the current study, the concentrations and abundances of 3-OH FAs were determined in soils from altitudinal transects under tropical and temperate climates: Mt. Rungwe (SW Tanzania) and Mt. Majella (Central Italy), respectively. The aim was to (i) examine and compare the distributions of 3-OH FAs in soils from different climatic zones and (ii) to investigate the potential of 3-OH FAs as temperature and pH proxies. When combined with previously published data, a moderate correlation (R2 0.62) between the summed iso and anteiso to the total amount of normal 3-OH FAs (RIAN index) and pH was obtained. We show that Gram-negative bacteria respond in the same way to temperature variations in soils from different latitudes, with a relative increase of the anteiso to normal 3-OH FA ratios of the C 15 and C 17 compounds (RAN 15 and RAN 17 indices, respectively) with decreasing temperature. Nevertheless, the intercepts of the relationships between RAN 15 and MAAT are mountain-dependent, suggesting that regional calibrations may be required to use RAN 15 as a temperature proxy. In contrast with RAN 15 , the statistical similarity of the local relationships between RAN 17 and MAAT leads to a combined calibration (R2 0.60, residual mean error 5.1 °C) covering a wide range of temperature (ca. 0–25 °C). As 3-OH FAs seem well-preserved in sedimentary archives, this strengthens the potential of these compounds as a temperature and pH proxy for paleoreconstructions in terrestrial settings. [ABSTRACT FROM AUTHOR]

Abstract Instrumental records of temperature and hydrological regimes in East Africa evidence frequent droughts with dramatic effects on population and ecosystems. Sources of these climatic variations remain largely unconstrained, partly because of a paucity of Late Holocene records. Here, we present a multi-proxy analysis of a 4-m continuous sediment core collected in the Kyambangunguru crater marsh, in southwest Tanzania, covering the last 4000 yrs (cal. BP). We used microscopic (macro-remains, microfossils, palynofacies, pollen), elemental (carbon, nitrogen contents), molecular (br GDGTs, n- alkanes) and compound-specific isotopic (δ2H n -alkanes) investigations to reconstruct the environmental history of the marsh. The multi proxy record reveals that, 2500 years ago, the marsh underwent a major ecological transition from a lake to a peatland. Temperature and hydrological reconstructions evidence warmer and drier conditions between 2200 and 860 cal. BP, which probably triggered the establishment of a perennial peatland. This study is one of the first combined temperature and precipitation record of Late Holocene in the region and highlights changes in the spatial distribution of the East African climate regimes. Several cold periods are observed, between 3300 and 2000 cal. BP and since 630 cal. BP, the latter corresponding to the Little Ice Age. Moreover, wetter conditions are reported during the Medieval Climate Anomaly in contrast to other north-eastern African records suggesting that Tanzania is located at the transition between two hydro-climatic zones (north-eastern versus southern Africa) and has experienced variable contributions of these two zones over the last millennium. Highlights • 4000-year continuous peat record of the Late Holocene in East Africa (SW Tanzania). • Multi proxy approach evidences major ecological changes at ca. 2500 yr cal. BP. • Detailed temperature and hydrology records highlight several cold events. • More recent climate conditions seem connected to South African climate variability. [ABSTRACT FROM AUTHOR]

• Forest management practices can lead to distinct compositions of topsoil OM. • Thermal stability is likely constrained by mineral interactions. • Thermal analysis and Py-GC/MS highlight forest management impacts on OM. The effect of forest management practices on carbon quality is poorly documented. To assess changes in the quality and stability of soil organic carbon (SOC) of a temperate forest upon human activities, we investigated soil from forests (i) developed following natural regeneration after clearcutting 20 and 40 years ago, (ii) developed following afforestation on an abandoned crop area 40 years ago and (iii) in an area where regular clear-cut (with wood residues input) was conducted 40 years ago. Topsoil and subsoil layers were collected (0–20 cm and 50–80 cm). Soil organic matter (OM) was characterized by elemental analysis (total carbon and total nitrogen), thermal analysis (Rock-Eval®) and thermochemolysis (i.e., Py-GC/MS in the presence of tetramethylammonium hydroxide (TMAH)). In addition, a size fractionation to separate the labile coarse fraction (50–2000 μm) from the fine fraction (<50 µm) was performed. These fractions were analyzed by thermal analysis. Despite no measurable differences in carbon and nitrogen contents, the characterization of the OM by thermal analysis, and the relative quantification of OM compounds revealed differences in the composition in OM for the topsoil layers. The thermal analysis clearly distinguished sites with inputs of woody residues (higher HI) with a higher relative contribution of lignin and cutin/suberin compounds. However, the OM thermal stability seems mainly controlled by the organo-mineral interactions rather than chemical composition. Combination of Rock-Eval® thermal analysis and Py-GC/MS suggests that thermal stability cannot be used as an indicator of stability in specific contexts where pedogenetic processes are deeply modified by regular and extensive anthropogenic inputs of woody residues. [ABSTRACT FROM AUTHOR]

The role of mountain evolution on local climate is poorly understood and potentially underestimated in climate models. One prominent example is East Africa, which underwent major geodynamic changes with the onset of the East African Rift System (EARS) more than 250 Myr ago. This study explores, at the regional East African scale, a molecular approach for terrestrially-based paleo-climatic reconstructions that takes into account both changes in temperature and in altitude, potentially leading to an improved concept in paleo-climatic reconstructions. Using surface soils collected along pronounced altitudinal gradients in Mt. Rungwe ( n = 40; Southwest Tanzania) and Mt. Kenya ( n = 20; Central Kenya), we investigate the combination of 2 terrestrial proxies, leaf wax n -alkane δ 2 H (δ 2 H wax ) and branched glycerol dialkyl glycerol tetraether (br GDGT) membrane lipids, as (paleo) elevation and (paleo) temperature proxies, respectively. At the mountain scale, a weak link between δ 2 H wax and altitude ( R 2 = 0.33) is observed at Mt. Kenya, but no relationship is observed at Mt. Rungwe. It is likely that additional parameters, such as decreasing relative humidity (RH) or vegetation changes with altitude, are outcompeting the expected 2 H-depletion trend along Mt. Rungwe. In contrast, br GDGT-derived absolute mean annual air temperature (MAAT) and temperature lapse rate (0.65 °C/100 m) for both mountains are in good agreement with direct field measurements, further supporting the robustness of this molecular proxy for (paleo) temperature reconstructions. At the regional scale, estimated and observed δ 2 H data in precipitation along 3 mountains in East Africa (Mts. Rungwe, Kenya and Kilimanjaro) highlight a strong spatial heterogeneity, preventing the establishment of a regional based calibration of δ 2 H wax for paeloaltitudinal reconstructions. Different from that, an improved regional soil calibration is developed between br GDGT distribution and MAAT by combining the data from this study (Mts. Rungwe and Kenya) with previous results from East African surface soils along Mts. Kilimanjaro (Tanzania) and Rwenzori (Uganda). This new regional calibration, based on 105 samples, improves both the R 2 (0.77) and RMSE (root mean square error; 2.4 °C) of br GDGT-derived MAAT over the global soil calibrations previously established ( R 2 = 0.56; RMSE = 4.2 °C) and leads to more accurate (paleo) temperature reconstructions in the region. [ABSTRACT FROM AUTHOR]

[Display omitted] • Lipid biomarkers from loess-paleosol sequences inform on palaeoenvironmental changes. • Shrub versus grass cover shifts suggested by n -alkyl compounds and triterpenoids. • Regional temperature variations suggested by bacterial membrane lipids. • Distinction between anthropogenic and climate impacts on local vegetation cover. • Significant impacts of reindeer herders on vegetation in sub-Arctic environment. Arctic reindeer herders demonstrate resilience to climate fluctuations by adjusting their pastoral practices to changing environments. The multiple phases of occupation at one of the oldest identified reindeer-herding sites, I A ^ rte 6 on the I A ^ mal peninsula, northwest Siberia, are thought to be linked to its local vegetation cover. Here we provide information on local palaeovegetation and climate shifts which occurred between the 7th and the 11th century CE based on lipid biomarkers. Aliphatic compounds, pentacyclic triterpenoids, branched glycerol dialkyl glycerol tetraethers (brGDGTs) and other lipids were analysed in four separate palaeosols from two loess-palaeosol sequences at the site. Based on different indices, the impact of human- or root-derived lipids and post-depositional microbial degradation on the signature of the studied pedosequences seem limited, which indicates that palaeobiomarkers are well preserved and representative of the analysed compounds. n -Alkanes, n -carboxylic acids, n -aldehydes and pentacyclic triterpenoids point to the progressive colonization of grasses, sedges and herbs at the site, which can be attributed to the regional decrease in temperature suggested by bacterial-derived brGDGTs. During the last phase of occupation, however, when proxies point to increasing temperatures, and shrubs would normally be expected to return, the shrub cover continued to decrease, probably due to the impact of camping and holding reindeer at the site. The decoupling trends observed for particular pentacyclic triterpenoids as potential dwarf birch biomarkers could suggest a preferential shift of species within shrubs, probably influenced by human activities. Multi-family lipid biomarker analysis therefore made it possible to distinguish anthropogenic impacts on the local vegetation cover from regional climatic changes, and show how significant the impacts of humans on local vegetation can be, even in extreme environments where such activities are limited. [ABSTRACT FROM AUTHOR]

Isoprenoid and branched glycerol dialkanol diethers (iso GDDs and br GDDs) have recently been detected in various environments, including sediment, soil and peat deposits. Their structures strongly resemble those of glycerol dialkyl glycerol tetraethers (GDGTs). Nevertheless, the origin of GDDs and their link to GDGTs remain unclear. Here we examined the concentration and distribution of iso GDDs and br GDDs, together with those of iso GDGTs and br GDGTs along a 4 m peat core from Tanzania. Whereas br GDDs have only been detected to date in their core lipid (CL) form, we report here, for the first time, br GDDs in both CL and intact polar lipid (IPL) forms, suggesting a biosynthetic origin for br GDDs. Concentrations of br GDGTs and br GDDs on one hand and of iso GDGTs and iso GDDs on the other hand, were observed to significantly co-vary ( R 2 0.49–0.58; p < 0.05), both for the CL and IPL fractions. Moreover, the fractional abundance of each GDD correlated significantly with that of its GDGT analogue ( R 2 0.33–0.97; p < 0.05). Taken together, the data show that GDDs and GDGTs are closely related and likely take part in common metabolic pathways, although the hypothesis of GDDs being degradation products of GDGTs cannot be excluded. [ABSTRACT FROM AUTHOR]

Abstract: The rate of the transfer of deuterium from to the three types (benzylic, aliphatic and aromatic) of bonds of 2-Ethylnaphthalene (and Methylnaphthalene) has been measured in the laboratory. The D/H ratio of each bond was calculated from the mass spectrum of the different isotopomers produced in the source of the GC mass spectrometer. The relations between the D/H ratio of the different isotopomers allow to calculate the internal isotopic fractionation factors (α i−j =(D/H) i /(D/H) j ) between the 3 bonds: α Benzylic–Aromatic =1.99±0.38 and α Aliphatic–Aromatic =1.22±0.39. Isotopic exchange rate constants are ⩾2.2×10−7±0.4 s−1, determined at room temperature for 10−3 g of 2-Ethylnaphthalene in contact with 5×1012 cm−3 of . These results are compatible with those measured in the insoluble organic matter (IOM) isolated from the Orgueil meteorite (), i.e., α Benzylic–Aromatic =1.96±0.05 and α Aliphatic–Aromatic =1.35±0.05. Using the calculated dust and H2D+ densities from the models of deuterium chemistry in protostellar disks, the duration needed to enrich the IOM up to its measured D/H ratio is ⩽104±1 s. These laboratory results are in agreement with a late deuteration of the insoluble organic matter taking place in the solar T-Tauri disk by interaction of the organic dust with H2D+. [Copyright &y& Elsevier]

• %Corg and %N reflect significant inputs of OM in sediments during fireplace operation. • Lipids and bulk OM mark the use of wood as fuel and the involvement of animal OM. • Distinction between meat-cooking and bone-fueled fireplaces is possible. • N-compounds are characteristic of culinary use. A better understanding of the operation and use of prehistoric fires is fundamental to interpreting the organization of living spaces. Following a previous study that focused on the organic signatures of fireplaces fueled with wood and/or bones, this study targeted the completion of an experimental reference database through the addition of a wood-fueled fireplace dedicated to the cooking of meat. Different sedimentary features of this experimental fireplace were visually identified (e.g. darkening, reddening), sampled, and subjected to geochemical analysis. Corg and N contents were quantified, samples were extracted with organic solvents and analyzed through GC–MS and bulk organic matter was characterized through py(TMAH)-GC–MS. Five different samples were studied and compared with a control sample, representative of the local background. A significant increase of Corg and N contents was measured for the three samples presenting darkened or charred caracteristics. The meat-cooking fireplace seems to be characterized by the strong contribution of nitrogen, which was visible in elementary analyses as well as in the molecular composition of solvent extracts, and bulk organic matter. More specifically, compounds containing nitrile functions, amides, N-heterocyclic and N-aromatic compounds could be detected in solvent extracts. Amines, amides, N-heterocyclic and N-aromatic compounds could be identified in py(TMAH)-GC–MS. Some of these compounds present a relative stability in soils and could therefore aid in our comprehension and functional interpretations of archaeological fireplaces, and may, more particularly, make it possible to highlight the use of fireplaces for the cooking of meat. [ABSTRACT FROM AUTHOR]