The tin content of lead inclusions in ancient tin-bronze artifacts: a time-dependent process?

In antiquity, Pb was a common element added in the production of large bronze artifacts, especially large statues, to impart fluidity to the casting process. As Pb does not form a solid solution with pure Cu or with the Sn-Cu alloy phases, it is normally observed in the metal matrix as globular droplets embedded within or in interstitial positions among the crystals of Sn-bronze (normally the α phase) as the last crystallizing phase during the cooling process of the Cu-Sn-Pb ternary melt. The disequilibrium Sn content of the Pb droplets has recently been suggested as a viable parameter to detect modern materials [Shilstein, Berner, Feldman, Shalev & Rosenberg (2019). STAR Sci. Tech. Archaeol. Res. 5, 29-35]. The application assumes a time-dependent process, with a timescale of hundreds of years, estimated on the basis of the diffusion coefficient of Sn in Pb over a length of a few micrometres [Oberschmidt, Kim & Gupta (1982). J. Appl. Phys. 53, 5672-5677]. Therefore, Pb inclusions in recent Sn-bronze artifacts are actually a metastable solid solution of Pb-Sn containing ∼3% atomic Sn. In contrast, in ancient artifacts, unmixing processes and diffusion of Sn from the micro- and nano-inclusions of Pb to the matrix occur, resulting in the Pb inclusions containing a substantially lower or negligible amount of Sn. The Sn content in the Pb inclusions relies on accurate measurement of the lattice parameter of the phase in the Pb-Sn solid solution, since for low Sn values it closely follows Vegard's law. Here, several new measurements on modern and ancient samples are presented and discussed in order to verify the applicability of the method to the detection of modern artwork pretending to be ancient.

Industrial by-products-derived binders for in-situ remediation of high Pb content pyrite ash: Synergistic use of ground granulated blast furnace slag and steel slag to achieve efficient Pb retention and CO2 mitigation.

Ordinary Portland cement (OPC) is a cost-effective and conventional binder that is widely adopted in brownfield site remediation and redevelopment. However, the substantial carbon dioxide emission during OPC production and the concerns about its undesirable retention capacity for potentially toxic elements strain this strategy. To tackle this objective, we herein tailored four alternative binders (calcium aluminate cement, OPC-activated ground-granulated blast-furnace slag (GGBFS), white-steel-slag activated GGBFS, and alkaline-activated GGBFS) for facilitating immobilization of high Pb content pyrite ash, with the perspectives of enhancing Pb retention and mitigating anthropogenic carbon dioxide emissions. The characterizations revealed that the incorporation of white steel slag efficiently benefits the activity of GGBFS, herein facilitating the hydration products (mainly ettringite and calcium silicate hydrates) precipitation and Pb immobilization. Further, we quantified the cradle-to-gate carbon footprint and cost analysis attributed to each binder-Pb contaminants system, finding that the application of these alternative binders could be pivotal in the envisaged carbon-neutral world if the growth of the OPC-free roadmap continues. The findings suggest that the synergistic use of recycled white steel slag and GGBFS can be proposed as a profitable and sustainable OPC-free candidate to facilitate the management of lead-contaminated brownfield sites. The overall results underscore the potential immobilization mechanisms of Pb in multiple OPC-free/substitution binder systems and highlight the urgent need to bridge the zero-emission insights to sustainable in-situ solidification/stabilization technologies.

Lead isotopes of prehistoric copper tools define metallurgical phases in Late Neolithic and Eneolithic Italy.

The diffuse presence of small copper ore deposits in the Alpine area, mostly exploited since Late Medieval times, led most scholars to assume that these deposits may actually be active much earlier and that many of the circulating prehistoric metal objects found in the area were produced with local copper sources. This assumption was recently validated for the Recent Bronze Age through the use of lead isotope tracers, and well supported by the archaeometallurgical evidences found in the South-Eastern Alps. However, the scarcity of available lead isotope data for pre-Bronze Age metals precluded to date the reconstruction of the metal flow through the Late Neolithic and Eneolithic (or Copper Age). Based on 49 new analyses of important archaeological objects from the Alpine region, the Po River Valley and Central Italy, mostly axes dated from the Late Neolithic to the Late Eneolithic, here we show that the diffusion of copper in Northern Italy (approximately 4500-2200 BC) includes three major periods of metal use and/or production, each related to specific ore sources. The South Alpine copper was massively used only starting from the middle of the 3rd millennium BC, in connection or slightly earlier than the Beaker event.

A Bronze Age lip-paint from southeastern Iran.

A small chlorite vial, discovered among numerous artifacts looted and recovered in the Jiroft region of Kerman province, southeastern Iran, contains a deep red cosmetic preparation that is likely a lip-coloring paint or paste. Through analytical research involving XRD (X-ray diffraction), SEM-EDS (scanning electron microscopy-energy-dispersive spectroscopy), and HPLC-MS (high-performance liquid chromatography-mass spectrometry) analyses, the mineral components of the reddish substance were identified as hematite, darkened with manganite and braunite, and traces of galena and anglesite, mixed with vegetal waxes and other organic substances. The mixture, thus observed, bears a striking resemblance to the recipes of contemporary lipsticks. We also report the first radiocarbon date ever obtained from a Bronze age cosmetic in the ancient Near East: results place the pigment in the early 2nd millennium BCE, a date compatible with several mentions of the powerful eastern-iranian civilization of Marhasi in coeval cuneiform texts of Mesopotamia, as well as with its currently emerging archaeological picture.

A fresh perspective on infrared spectroscopy as a prescreening method for molecular and stable isotopes analyses on ancient human bones.

Following the development of modern genome sequencing technologies, the investigation of museum osteological finds is increasingly informative and popular. Viable protocols to help preserve these collections from exceedingly invasive analyses, would allow greater access to the specimens for scientific research. The main aim of this work is to survey skeletal tissues, specifically petrous bones and roots of teeth, using infrared spectroscopy as a prescreening method to assess the bone quality for molecular analyses. This approach could overcome the major problem of identifying useful genetic material in archaeological bone collections without resorting to demanding, time consuming and expensive laboratory studies. A minimally invasive sampling of archaeological bones was developed and bone structural and compositional changes were examined, linking isotopic and genetic data to infrared spectra. The predictive model based on Infrared parameters is effective in determining the occurrence of ancient DNA (aDNA); however, the quality/quantity of aDNA cannot be determined because of the influence of environmental and local factors experienced by the examined bones during the burial period.

Mechanistic insights into Pb and sulfates retention in ordinary Portland cement and aluminous cement: Assessing the contributions from binders and solid waste.

Identifying immobilization mechanisms of potentially toxic elements (PTEs) is of paramount importance in the field application of solidification/stabilization. Traditionally, demanding and extensive experiments are required to better access the underlying retention mechanisms, which are usually challenging to quantify and clarify precisely. Herein, we present a geochemical model with parametric fitting techniques to reveal the solidification/stabilization of Pb-rich pyrite ash through conventional (ordinary Portland cement) and alternative (calcium aluminate cement) binders. We found that ettringite and calcium silicate hydrates exhibit strong affinities for Pb at alkaline conditions. When the hydration products are unable to stabilize all the soluble Pb in the system, part of the soluble Pb may be immobilized as Pb(OH)2. At acidic and neutral conditions, hematite from pyrite ash and newly-formed ferrihydrite are the main controlling factors of Pb, coupled with anglesite and cerussite precipitation. Thus, this work provides a much-needed complement to this widely-applied solid waste remediation technique for the development of more sustainable mixture formulations.

Retention of phosphorus and fluorine in phosphogypsum for cemented paste backfill: Experimental and numerical simulation studies.

The solidification/stabilization of phosphogypsum using cemented paste backfill (OCPB) provides a low-cost and alternative in-situ technique for recycling phosphogypsum stockpiles. But the OCPB is far from obtaining steady states in which the pollutants would redistribute as a response to dynamic environmental conditions. Further, the associated chemical interactions and the mineralogy information of the solubility-controlling phases of contaminants (fluorine and phosphorus) have not been thoroughly studied or fully understood. In this study, a framework coupling the chemical, mineralogical, and morphological analyses is used to determine the fluoride and phosphate retention mechanisms of immobilized OCPB. Then the pH-dependent leaching tests and numerical simulation is applied as a useful tool to identify the minerals controlling stabilized OCPB leaching behavior. The overall findings proved that aluminate-rich calcium silicate hydrates play an essential role in fluoride and phosphate retention. Both experimental and simulational acid neutralization and leaching curves indicate that the cementitious matrix works as a strong buffering material ensuring high pH conditions that are necessary for fluorine and phosphorus retention. Although discrepancies were observed in absolute fluorine and phosphorus leaching values at highly acidic conditions, the simulations are able to describe highly amphoteric leaching behavior. The simulation suggests that the aluminum species and calcium phosphates governed the solubility of fluorine and phosphorus, respectively. The results of this work would have implications for predicting the leaching behavior of OCPB in detrimental and multiple environments.

Innovative Calcium Carbonate-Based Products to Repair Cracked Cement Mortars.

The durability of Portland cement mortars is often affected by environmental factors, which can cause physicochemical and mechanical degradation processes. In this study, the performance of three products, calcium acetoacetate and calcium tetrahydrofurfuryloxide dissolved in two different solvents developed and tested as stone consolidants, was evaluated in terms of crack filling or sealing and consolidation. Realistic cracks were induced in quasibrittle cement mortar prisms using a custom-designed test rig. The effectiveness and the performance of the considered treatments, investigated on specimens, were evaluated by optical and scanning electron microscopy, colourimetry, water absorption rate, ultrasonic pulse velocity, and surface hardness measurements. Results revealed that, in the examined conditions, the products were more suitable as surface consolidants than as crack fillers.

Integrated multi-analytical screening approach for reliable radiocarbon dating of ancient mortars.

Radiocarbon dating of the carbonate binder of historical mortars is a strategic research topic not lacking in complexities. The critical step is the separation of anthropogenic CaCO3-binder from other carbonate sources that could severely affect the resulting dates. Here we present a complete procedure for the processing and characterization of difficult mortars and of the separated binder fractions in order to assess a priori the chances of positively dating the mortar, and produce a binder fraction yielding the most reliable radiocarbon dates possible. Two complex architectural case studies from Northern Italy are presented and discussed in detail: the churches of Santa Maria Maggiore (Lomello, Pavia) and Santa Maria (Torba, Varese). The results support that both the reliability assessment and the successful radiocarbon dating are possible through a multi-analytical approach encompassing mineralogical and petrographic characterization, X-ray powder diffraction, scanning electron microscopy, measurement of carbon and oxygen stable isotopes, and optical cathodoluminescence.

An Atomistic Model Describing the Structure and Morphology of Cu-Doped C-S-H Hardening Accelerator Nanoparticles.

Calcium silicate hydrate (C-S-H) is the main binding phase in Portland cement. The addition of C-S-H nanoparticles as nucleation seeds has successfully been used to accelerate the hydration process and the precipitation of binding phases either in conventional Portland cement or in alternative binders. Indeed, the modulation of the hydration kinetics during the early-stage dissolution-precipitation reactions, by acting on the nucleation and growth of binding phases, improves the early strength development. The fine-tuning of concrete properties in terms of compressive strength and durability by designed structural modifications can be achieved through the detailed description of the reaction products at the atomic scale. The nano-sized, chemically complex and structurally disordered nature of these phases hamper their thorough structural characterization. To this aim, we implement a novel multi-scale approach by combining forefront small-angle X-ray scattering (SAXS) and synchrotron wide-angle X-ray total scattering (WAXTS) analyses for the characterization of Cu-doped C-S-H nanoparticles dispersed in a colloidal suspension, used as hardening accelerator. SAXS and WAXTS data were analyzed under a unified modeling approach by developing suitable atomistic models for C-S-H nanoparticles to be used to simulate the experimental X-ray scattering pattern through the Debye scattering equation. The optimization of atomistic models against the experimental pattern, together with complementary information on the structural local order from 29Si solid-state nuclear magnetic resonance and X-ray absorption spectroscopy, provided a comprehensive description of the structure, size and morphology of C-S-H nanoparticles from the atomic to the nanometer scale. C-S-H nanoparticles were modeled as an assembly of layers composed of 7-fold coordinated Ca atoms and decorated by silicate dimers and chains. The structural layers are a few tens of nanometers in length and width, with a crystal structure resembling that of a defective tobermorite, but lacking any ordering between stacking layers.

A Fresh View on Limestone Calcined Clay Cement (LC3) Pastes.

In this work, the factors controlling the fresh state properties of limestone calcined clay cement (LC3) are assessed and compared to Portland and binary cements, extending the scope of previous research by combining rheological measurements with setting time determination and the evaluation of plastic shrinkage by a novel method. Yield stress and elastic modulus are considered indicators for the structural build-up/breakdown process when stress is applied to the system. On the other hand, plastic shrinkage occurs from the mixing to the setting of fresh paste and plays an important role in governing microstructural changes due to settlement and evaporation. Evaluation of the rheological properties with time was appropriate to give an overview of the influence and behavior of different added materials. The elastic modulus of all binders (clinker, LC3, clinker-limestone, and clinker-calcined clay) was increased from mixing to 60 min of curing as follows: 5.27 × 103 to 9.50 × 105 Pa, 5.94 × 103 to 9.87 × 105 Pa, 6.89 × 103 to 5.62 × 105 Pa and 7.85 × 103 to 1.27 × 106 Pa, respectively. Moreover, during the first three hours of curing, LC3 exhibited a reduction of plastic shrinkage by more than a factor of 2 compared to clinker cement. The use of calcined clay with clinker increases the elastic modulus of the system due to the flocculation effect and increased water absorption, while a dilution effect is contributed due to deflocculation and a free-water increase in the system when a high fraction of limestone is present in the binary cement. The combination of limestone and calcined clay with clinker can induce additional chemical reactions, which control the early age properties, such as plastic shrinkage. The obtained results can contribute to optimizing the fresh state properties of ternary blends of OPC, calcined clay, and limestone through a knowledge-based approach.

Cement-stabilized contaminated soil: Understanding Pb retention with XANES and Raman spectroscopy.

Cement-based stabilization is a widespread technique used for the treatment of contaminated soils. Despite its established application, the mechanisms involved in the stabilization of contaminants are not fully understood yet. This work aims to elucidate the fate of a real Pb contaminated soil amended with different binders, by studying Pb local environment prior and after the stabilization process. The study of a complex historically contaminated soil was coupled with the investigation of simplified artificial systems, developed to model Pb local structure in the unknown newly formed hybrid systems of soil and binders. The use of synchrotron-based element-specific X-ray absorption spectroscopy (XAS) permitted to probe the actual transformation of Pb environment in the real contaminated soil after the stabilization process. With the support of the model systems, we can propose as the main mechanism involved in Pb retention in sulfated soil treated with cement, the incorporation and/or adsorption of Pb on calcium silicate hydrates and ettringite.

The use of the laser confocal scanning microscopy to measure resin remnants on customized lingual bracket.

BACKGROUND: The study aimed to evaluate the permanence of resin and enamel remains on lingual brackets at the end of orthodontic treatment and after the debonding procedure. The evaluation of resin remnants on customized lingual brackets bases has never done before in other studies because they are curved, and traditional techniques are not applicable. METHODS: The sample consisted of 100 lingual brackets (25 incisors, 25 canines, 25 premolars, 25 molars) scanned with a confocal laser microscope (OLS4000). We measured the brackets' surface and the area of resin remnants with the software of the microscope. Median and quartiles were presented to describe the data. ARI calculation was indirect for each tooth, measuring the resin remnants to the total surface of the bracket. The Kruskal-Wallis test and Fisher test were applied respectively to compare the percentages of remnants and the frequencies of the ARI between the four groups. RESULTS: After the analyses, 13 brackets had no adhesive remnants (ARI 0), 29 brackets had less than 50% of resin remnants (ARI 1), 50 brackets had more than 50% of resin remnants (ARI 2), and 8 brackets had 100% of adhesive (ARI 3). Canines brackets presented the lower amount of resin followed by premolars, incisors, and molars. CONCLUSION: Lingual brackets showed a high frequency of ARI = 2. The median percentage of the bracket surface covered by resin was 41%. We observed a slight tendency of more resin remnants on molar brackets, due to half-pad configuration. The authors suggest paying attention during the debonding procedure of molar brackets since a stronger connection between the adhesive and the bracket mesh means a higher risk of enamel damage.

Copper to Tuscany - Coals to Newcastle? The dynamics of metalwork exchange in early Italy.

The paper discusses results of an interdisciplinary research project integrating lead isotope, chemical, and archaeological analysis of 20 early metal objects from central Italy. The aim of the research was to develop robust provenance hypotheses for 4th and 3rd millennia BC metals from an important, yet hitherto neglected, metallurgical district in prehistoric Europe, displaying precocious copper mining and smelting, as well as socially significant uses of metals in 'Rinaldone-style' burials. All major (and most minor) ore bodies from Tuscany and neighbouring regions were characterised chemically and isotopically, and 20 Copper Age axe-heads, daggers and halberds were sampled and analysed. The objects were also reassessed archaeologically, paying special attention to find context, typology, and chronology. This multi-pronged approach has allowed us to challenge received wisdom concerning the local character of early metal production and exchange in the region. The research has shown that most objects were likely manufactured in west-central Italy using copper from Southern Tuscany and, quite possibly, the Apuanian Alps. A few objects, however, display isotopic and chemical signatures compatible with the Western Alpine and, in one case, French ore deposits. This shows that the Copper Age communities of west-central Italy participated in superregional exchange networks tying together the middle/upper Tyrrhenian region, the western Alps, and perhaps the French Midi. These networks were largely independent from other metal displacement circuits in operation at the time, which embraced the north-Alpine region and the south-eastern Alps, respectively.

Stabilization of lead contaminated soil with traditional and alternative binders.

The application of an innovative solidification/stabilization (S/S) process was investigated for the remediation of Pb contaminated soil. The performance of Pb stabilization was evaluated by comparing the use of calcium aluminate cement (CAC) and an alkali activated metakaolin binder vs the Ordinary Portland Cement (OPC). The phase composition of the stabilized products was investigated by XRD and correlated to the internal microstructure obtained by SEM-EDX imaging. Leaching tests were performed to ascertain the effectiveness of the proposed binders in the S/S of the contaminated soil, and Pb release was evaluated for each binding system. The overall results proved that multiple mechanisms are involved in Pb retention and that key parameters regulating the stabilization performance are strongly dependent on the type of applied binder system. Pb was found to be associated to C-S-H in the case of OPC, whereas ettringite played a key role in the retention of this contaminant using the CAC binder. The use of a NaOH activated metakaolin resulted in almost total retention of Pb, despite a lack of solidification, highlighting the importance of pH in the regulation of the leaching behavior.

Consecutive thermal and wet conditioning treatments of sedimentary stabilized cementitious materials from HPSS® technology: Effects on leaching and microstructure.

Soil and sediment contamination is recognised as one of the most relevant environmental problems caused by past industrial activities and unsustainable waste disposal practices, highlighting the need to develop or improve effective remediation techniques to support sustainable management strategies. In this context, the remediation of sediments dredged from the Mincio river (Italy) contaminated by mercury and heavy hydrocarbons (C12-40) was carried out by applying and implementing the High Performance Solidification/Stabilization technology, aimed at producing safe and reusable cement-based granular materials. The technology was improved by decreasing both the temperature and time of the thermal desorption treatment (from 280 to 110 °C and from 4-16 h to 70 min, respectively) and by including a wet conditioning step to the process. Temperature and time reduction allowed to diminish the degradation of the cementitious phases of the granules (usually related to the high temperatures employed in the process), while the wet conditioning step allowed to improve their mechanical properties, as well as to further reduce the leaching of contaminants. The physical-chemical properties of the granules and contaminant leaching in water were investigated by Inductively Coupled Plasma Mass and Optical Emission Spectrometry, Ultraviolet-Visible spectroscopy, Gas Chromatography, X-Ray Powder Diffraction, and Scanning Electron Microscopy, in order to identify the optimal parameters for both thermal and wet conditioning processes. The overall results showed that the use of consecutive thermal and wet conditioning treatment on sedimentary cementitious materials from the High Performance Solidification/Stabilization technology led to the removal of volatile pollutants and to the improvement of granule quality, thus providing a final material that satisfied all the Italian regulatory requirements for reuse. Therefore, the findings obtained in this study may contribute to the development of sustainable management strategies for contaminated soils and sediments, leading to their valorisation through the transformation into reusable materials.

Archaeological assessment reveals Earth's early transformation through land use.

Environmentally transformative human use of land accelerated with the emergence of agriculture, but the extent, trajectory, and implications of these early changes are not well understood. An empirical global assessment of land use from 10,000 years before the present (yr B.P.) to 1850 CE reveals a planet largely transformed by hunter-gatherers, farmers, and pastoralists by 3000 years ago, considerably earlier than the dates in the land-use reconstructions commonly used by Earth scientists. Synthesis of knowledge contributed by more than 250 archaeologists highlighted gaps in archaeological expertise and data quality, which peaked for 2000 yr B.P. and in traditionally studied and wealthier regions. Archaeological reconstruction of global land-use history illuminates the deep roots of Earth's transformation and challenges the emerging Anthropocene paradigm that large-scale anthropogenic global environmental change is mostly a recent phenomenon.

A universal curve of apatite crystallinity for the assessment of bone integrity and preservation.

The reliable determination of bioapatite crystallinity is of great practical interest, as a proxy to the physico-chemical and microstructural properties, and ultimately, to the integrity of bone materials. Bioapatite crystallinity is used to diagnose pathologies in modern calcified tissues as well as to assess the preservation state of fossil bones. To date, infrared spectroscopy is one of the most applied techniques for bone characterisation and the derived infrared splitting factor (IRSF) has been widely used to practically assess bioapatite crystallinity. Here we thoroughly discuss and revise the use of the IRSF parameter and its meaning as a crystallinity indicator, based on extensive measurements of fresh and fossil bones, virtually covering the known range of crystallinity degree of bioapatite. A novel way to calculate and use the infrared peak width as a suitable measurement of true apatite crystallinity is proposed, and validated by combined measurement of the same samples through X-ray diffraction. The non-linear correlation between the infrared peak width and the derived ISRF is explained. As shown, the infrared peak width at 604 cm-1 can be effectively used to assess both the average crystallite size and structural carbonate content of bioapatite, thus establishing a universal calibration curve of practical use.

Raman hyperspectral imaging as an effective and highly informative tool to study the diagenetic alteration of fossil bones.

Retrieving the pristine chemical or isotopic composition of archaeological bones is of great interest for many studies aiming to reconstruct the past life of ancient populations (i.e. diet, mobility, palaeoenvironment, age). However, from the death of the individual onwards, bones undergo several taphonomic and diagenetic processes that cause the alteration of their microstructure and composition. A detailed study on bone diagenesis has the double purpose to assess the preservation state of archaeological bones and to understand the alteration pathways, thus providing evidence that may contribute to evaluate the reliability of the retrieved information. On these bases, this research aims to explore the effectiveness of Raman hyperspectral imaging to detect types, extent and spatial distribution of diagenetic alteration at the micro-scale level. An early-Holocene bone sample from the Al Khiday cemetery (Khartoum, Sudan) was here analysed. Parameters related to the collagen content, bioapatite crystallinity and structural carbonate content, and to the occurrence of secondary mineral phases were calculated from Raman spectra. The acquired data provided spatially-resolved information on both the preservation state of bone constituents and the diagenetic processes occurring during burial. Given the minimal sample preparation, the easy and fast data acquisition and the improvement of system configurations, micro-Raman spectroscopy can be extensively applied as a screening method on a large set of samples in order to characterise the preservation state of archaeological bones. This technique can be effectively applied to identify suitable and well preserved portions of the analysed sample on which perform further analyses.

Correction: Long-distance connections in the Copper Age: New evidence from the Alpine Iceman's copper axe.

[This corrects the article DOI: 10.1371/journal.pone.0179263.].