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Sulfur isotope composition of organic tissues is a commonly used tool for gathering information about provenance and diet in archaeology and paleoecology. However, the lack of maps predicting sulfur isotope variations on the landscape limits the possibility to use this isotopic system in quantitative geographic assignments. We compiled a database of 2,680 sulfur isotope analyses in the collagen of archaeological human and animal teeth from 221 individual locations across Western Europe. We used this isotopic compilation and remote sensing data to apply a multivariate machine-learning regression, and to predict sulfur isotope variations across Western Europe. The resulting model shows that sulfur isotope patterns are highly predictable, with 65% of sulfur isotope variations explained using only 4 variables representing marine sulfate deposition and local geological conditions. We used this novel sulfur isoscape and existing strontium and oxygen isoscapes of Western Europe to apply triple isotopes continuous-surface probabilistic geographic assignments to assess the origin of a series of teeth from local animals and humans from Brittany. We accurately and precisely constrained the origin of these individuals to limited regions of Brittany. This approach is broadly transferable to studies in archaeology and paleoecology as illustrated in a companion paper (Colleter et al. 2021).

The global biosphere is commonly assumed to have been less productive before the rise of complex eukaryotic ecosystems than it is today 1 . However, direct evidence for this assertion is lacking. Here we present triple oxygen isotope measurements (∆ 17 O) from sedimentary sulfates from the Sibley basin (Ontario, Canada) dated to about 1.4 billion years ago, which provide evidence for a less productive biosphere in the middle of the Proterozoic eon. We report what are, to our knowledge, the most-negative ∆ 17 O values (down to −0.88‰) observed in sulfates, except for those from the terminal Cryogenian period 2 . This observation demonstrates that the mid-Proterozoic atmosphere was distinct from what persisted over approximately the past 0.5 billion years, directly reflecting a unique interplay among the atmospheric partial pressures of CO 2 and O 2 and the photosynthetic O 2 flux at this time 3 . Oxygenic gross primary productivity is stoichiometrically related to the photosynthetic O 2 flux to the atmosphere. Under current estimates of mid-Proterozoic atmospheric partial pressure of CO 2 (2–30 times that of pre-anthropogenic levels), our modelling indicates that gross primary productivity was between about 6% and 41% of pre-anthropogenic levels if atmospheric O 2 was between 0.1–1% or 1–10% of pre-anthropogenic levels, respectively. When compared to estimates of Archaean 4 – 6 and Phanerozoic primary production 7 , these model solutions show that an increasingly more productive biosphere accompanied the broad secular pattern of increasing atmospheric O 2 over geologic time 8 . Triple oxygen isotope measurements of 1.4-billion-year-old sedimentary sulfates reveal a unique mid-Proterozoic atmosphere and demonstrate that gross primary productivity in the mid-Proterozoic was between 6% and 41% of pre-anthropogenic levels.

• A growing number of field studies report isotopic offsets between stem water and its potential sources that prevent the unambiguous identification of plant water origin using water isotopes. We explored the causes of this isotopic offset by conducting a controlled experiment on the temperate tree species Fagus sylvatica. • We measured δ²H and δ18O of soil and stem water from potted saplings growing on three soil substrates and subjected to two watering regimes. • Regardless of substrate, soil and stem water δ²H were similar only near permanent wilting point. Under moister conditions, stem water δ²H was 11 ± 3‰ more negative than soil water δ²H, coherent with field studies. Under drier conditions, stem water δ²H became progressively more enriched than soil water δ²H. Although stem water δ18O broadly reflected that of soil water, soil–stem δ²H and δ18O differences were correlated (r = 0.76) and increased with transpiration rates indicated by proxies. • Soil–stem isotopic offsets are more likely to be caused by water isotope heterogeneities within the soil pore and stem tissues, which would be masked under drier conditions as a result of evaporative enrichment, than by fractionation under root water uptake. Our results challenge our current understanding of isotopic signals in the soil–plant continuum.

Contact electrification between water and a solid surface is crucial for physicochemical processes at water–solid interfaces. However, the nature of the involved processes remains poorly understood, especially in the initial stage of the interface formation. Here we report that H₂O₂ is spontaneously produced from the hydroxyl groups on the solid surface when contact occurred. The density of hydroxyl groups affects the H₂O₂ yield. The participation of hydroxyl groups in H₂O₂ generation is confirmed by mass spectrometric detection of 18O in the product of the reaction between 4-carboxyphenylboronic acid and 18O–labeled H₂O₂ resulting from 18O₂ plasma treatment of the surface. We propose a model for H₂O₂ generation based on recombination of the hydroxyl radicals produced from the surface hydroxyl groups in the water–solid contact process. Our observations show that the spontaneous generation of H₂O₂ is universal on the surfaces of soil and atmospheric fine particles in a humid environment.

The 18O/16O of calcite fossils increased by ∼8‰ between the Cambrian and present. It has long been controversial whether this change reflects evolution in the δ18O of seawater, or a decrease in ocean temperatures, or greater extents of diagenesis of older strata. Here, we present measurements of the oxygen and “clumped” isotope compositions of Phanerozoic dolomites and compare these data with published oxygen isotope studies of carbonate rocks. We show that the δ18O values of dolomites and calcite fossils of similar age overlap one another, suggesting they are controlled by similar processes. Clumped isotope measurements of Cambrian to Pleistocene dolomites imply crystallization temperatures of 15–158 °C and parent waters having δ18OVSMOW values from −2 to +12‰. These data are consistent with dolomitization through sediment/ rock reaction with seawater and diagenetically modified seawater, over timescales of 100 My, and suggest that, like dolomite, temporal variations of the calcite fossil δ18O record are largely driven by diagenetic alteration. We find no evidence that Phanerozoic seawater was significantly lower in δ18O than preglacial Cenozoic seawater. Thus, the fluxes of oxygen–isotope exchange associated with weathering and hydrothermal alteration reactions have remained stable throughout the Phanerozoic, despite major tectonic, climatic and biologic perturbations. This stability implies that a long-term feedback exists between the global rates of seafloor spreading and weathering. We note that massive dolomites have crystallized in pre-Cenozoic units at temperatures >40 °C. Since Cenozoic platforms generally have not reached such conditions, their thermal immaturity could explain their paucity of dolomites.

The extent to which climate change causes significant societal disruption remains controversial. An important example is the decline of the Akkadian Empire in northern Mesopotamia ∼4.2 ka, for which the existence of a coincident climate event is still uncertain. Here we present an Iranian stalagmite record spanning 5.2 ka to 3.7 ka, dated with 25 U/Th ages that provide an average age uncertainty of 31 y (1σ). We find two periods of increased Mg/Ca, beginning abruptly at 4.51 and 4.26 ka, and lasting 110 and 290 y, respectively. Each of these periods coincides with slower vertical stalagmite growth and a gradual increase in stable oxygen isotope ratios. The periods of high Mg/Ca are explained by periods of increased dust flux sourced from the Mesopotamia region, and the abrupt onset of this dustiness indicates threshold behavior in response to aridity. This interpretation is consistent with existing marine and terrestrial records from the broad region, which also suggest that the later, longer event beginning at 4.26 ka is of greater regional extent and/or amplitude. The chronological precision and high resolution of our record indicates that there is no significant difference, at decadal level, between the start date of the second, larger dust event and the timing of North Mesopotamia settlement abandonment, and furthermore reveals striking similarity between the total duration of the second dust event and settlement abandonment. The Iranian record demonstrates this region’s threshold behavior in dust production, and its ability to maintain this climate state for multiple centuries naturally.

This study investigates to what extent Bronze Age societies in Northern Italy were permeable accepting and integrating non-local individuals, as well as importing a wide range of raw materials, commodities, and ideas from networks spanning continental Europe and the Mediterranean. During the second millennium BC, the communities of Northern Italy engaged in a progressive stabilization of settlements, culminating in the large polities of the end of the Middle/beginning of the Late Bronze Age pivoted around large defended centres (the Terramare). Although a wide range of exotic archaeological materials indicates that the inhabitants of the Po plain increasingly took part in the networks of Continental European and the Eastern Mediterranean, we should not overlook the fact that the dynamics of interaction were also extremely active on local and regional levels. Mobility patterns have been explored for three key-sites, spanning the Early to Late Bronze Age (1900-1100 BC), namely Sant'Eurosia, Casinalbo and Fondo Paviani, through strontium and oxygen isotope analysis on a large sample size (more than 100 individuals). The results, integrated with osteological and archaeological data, document for the first time in this area that movements of people occurred mostly within a territorial radius of 50 km, but also that larger nodes in the settlement system (such as Fondo Paviani) included individuals from more distant areas. This suggests that, from a demographic perspective, the process towards a more complex socio-political system in Bronze Age Northern Italy was triggered by a largely, but not completely, internal process, stemming from the dynamics of intra-polity networks and local/regional power relationships.

We report data on the martian meteorite Northwest Africa (NWA) 7034, which shares some petrologic and geochemical characteristics with known martian meteorites of the SNC (i.e., shergottite, nakhlite, and chassignite) group, but also has some unique characteristics that would exclude it from that group. NWA 7034 is a geochemically enriched crustal rock compositionally similar to basalts and average martian crust measured by recent Rover and Orbiter missions. It formed 2.089 ± 0.081 billion years ago, during the early Amazonian epoch in Mars' geologic history. NWA 7034 has an order of magnitude more indigenous water than most SNC meteorites, with up to 6000 parts per million extraterrestrial H2O released during stepped heating. It also has bulk oxygen isotope values of Δ 17 O = 0.58 ± 0.05 per mil and a heat-released water oxygen isotope average value of Δ 17 O = 0.330 ± 0.011 per mil, suggesting the existence of multiple oxygen reservoirs on Mars.

Analysing the nitrogen (15ε) and oxygen (18ε) isotope effects of anaerobic ammonium oxidation (anammox) is essential for accurately assessing its potential contribution to fixed-N losses in the ocean, yet the 18ε of anammox remains unexplored. Here, we determined the previously unexplored 18ε of anammox using a highly enriched culture of the marine anammox species “Ca. Scalindua sp”. Because Scalindua significantly accelerated oxygen isotope exchange between NO2− and H2O, we introduced a new rate constant for anammox-mediated oxygen isotope exchange (keq, AMX = 8.44 ~ 13.56 × 10−2 h−1), which is substantially faster than abiotic oxygen isotope exchange (keq, abio = 1.13 × 10−2 h−1), into a numerical model to estimate the 18ε during anammox. Based on our experimental results, we successfully determined the 18ε associated with: (1) conversion of NO2− to N2 (18εNO2- → N2 = 10.6 ~ 16.1‰), (2) NO2− oxidation to NO3− (18εNO2- → NO3- = −2.9 ~ −11.0‰, inverse fractionation), (3) incorporation of oxygen from water during NO2− oxidation to NO3− (18εH2O = 16.4 ~ 19.2‰). Our study underscores the possibility that unique anammox oxygen isotope signals may be masked due to substantial anammox-mediated oxygen isotope exchange between NO2− and H2O. Therefore, careful consideration is required when utilizing δ18ONO3- and δ18ONO2- as geochemical markers to assess the potential contribution of anammox to fixed-N losses in the ocean.

The outbreak of certain bacteria can trigger severe diseases, even posing a threat to public safety, leading to significant social panic and economic losses. Thus, tracing the origin of bacteria is of great significance. Stable isotope analysis technology offers a new way to determine the geographical information of bacteria, yet related research still fails to meet the application requirements of this technology in practical cases of bacterial traceability. In this study, a systematic stable isotope analysis method for bacteria and their culture conditions, based on practical geographical environments, was established for the first time. Escherichia coli and Staphylococcus aureus were cultured with water from five regions and different culture media, and the stable isotope ratios of H/O/C/N in the two bacteria and the culture media were measured to explore the relationship between bacteria and their cultivation site. The results showed that there were linear relationships between the hydrogen and oxygen stable isotopes of the two bacteria and the culture water. The combined discriminant model constructed using multi-isotope (H/O/C/N) characteristics achieved a 100% accuracy rate in identifying the types of culture media. These results indicate that research on the isotope association between bacteria and their culture water can be used to infer the cultivation region, and the specific source of bacteria can be further inferred through the multi-isotope combination discriminant model. This study can provide a relatively complete research idea for bacterial geographical traceability research, and improve the efficiency and accuracy of bacterial traceability work in practical investigations. Key points Established a systematic stable isotope analysis method for bacteria. E. coli and S. aureus have linear H/O isotope correlations with culture water. Multi-isotope discriminant model achieves 100% accuracy in identifying culture media.