Characterization of archaeological bones from the Al Khiday cemetery (Central Sudan): structure and microstructure of diagenetically altered bioapatite

Bone is a composite material constituted by the association of an organic matrix and bioapatite nano-crystals. Human bones, frequently recovered from archaeological contexts, represent a valuable source of information on health, demography, age, diet and mobility of ancient populations as well as on environmental conditions experienced. However the reliability of such information depends on the preservation state of bone material and its constituents, i.e. the preservation of the in vivo chemical and isotopic composition. Bone alteration is caused by taphonomic and diagenetic processes, mainly driven by environmental conditions, affecting bones since the death of the individual and during burial. Therefore, a diagenetic study on archaeological bones, aiming to accurately determine their preservation state, taking into account the archaeological and palaeoenvironmental contexts, is a fundamental step when retrieving information by chemical or isotopic analyses. Based on this perspective, this research project is mainly addressing the radiocarbon dating of the bioapatite fraction of human bones, coming from the archaeological site 16D4 – Al Khiday 2 (Sudan) and the assessment of the reliability of results. At 16D4, a multi-stratified cemetery was excavated and several burial phases were recovered. In fact, the site was used as a burial ground at different periods along almost the entire Holocene. The well-defined archaeological context provided a set of samples suitable to investigate the reliability of the radiocarbon dating of bioapatite as well as the influence of environmental/climatic changes, occurring in Central Sudan along the Holocene, on bone diagenesis. Firstly a multi-disciplinary study on bones and associated soil sediments has been carried out, in order to define the preservation state of bones as well as to provide a model for diagenetic processes taking into account pedogenic processes and changes in environmental, climatic and local burial conditions. Based in the established model for diagenetic alteration of these bones, radiocarbon dating on selected bioapatite samples was performed and reliability of results discussed. Characterization of bone samples was carried out by optical and scanning electron microscopy, X-ray computed micro-tomography, X-ray powder diffraction, Fourier transform infrared spectroscopy and micro-Raman spectroscopy. Samples of pedogenic calcrete horizon, found at the 16D4 site, were analysed by optical, cathodoluminescence, and scanning electron microscopy. Bone and calcrete samples were prepared for 14C-AMS dating. Results from this case study prove that the radiocarbon dating of bioapatite for heavily altered bone samples may not be reliable. Characterization of bones and associated soil sediments provided valuable information on the diagenetic history of bones and on the influence of changes in environmental and local burial conditions on bone preservation. Moreover, results highlight the relevance of a multi-disciplinary approach to the study of the archaeological and palaeoenvironmental context

Late Pleistocene/Early Holocene Evidence of Prostatic Stones at Al Khiday Cemetery, Central Sudan

The recovery of three stone-like ovoid objects within the burial of a pre-Mesolithic (Late Pleistocene/Early Holocene) individual at Al Khiday cemetery (Central Sudan) raises the question of the nature and origin of these objects. The position in which the objects were found in relation to the human skeleton suggested a pathological condition affecting the individual, possibly urinary bladder, kidney stones or gallstones. To solve this issue, a multi-analytical approach, consisting of tomographic, microstructural and compositional analyses, was therefore performed. Based on their microstructure and mineralogical composition, consisting of hydroxylapatite and whitlockite, the investigated stones were identified as primary (endogenous) prostatic calculi. In addition, the occurrence of bacterial imprints also indicates on-going infectious processes in the individual. This discovery of the earliest known case of lithiasis extends the appearance of prostatic stones into the Late Pleistocene/Early Holocene, a disease which therefore can no longer be considered exclusive to the modern era, but which also affected prehistoric individuals, whose lifestyle and diet were significantly different to our own

The role of nanoparticle structure and morphology in the dissolution kinetics and nutrient release of nitrate‑doped calcium phosphate nanofertilizers

Bio-inspired synthetic calcium phosphate (CaP) nanoparticles (NPs), mimicking the mineral component of bone and teeth, are emergent materials for sustainable applications in agriculture. These sparingly soluble salts show self-inhibiting dissolution processes in undersaturated aqueous media, the control at the molecular and nanoscale levels of which is not fully elucidated. Understanding the mechanisms of particle dissolution is highly relevant to the efcient delivery of macronutrients to the plants and crucial for developing a valuable synthesis-by-design approach. It has also implications in bone (de)mineralization processes. Herein, we shed light on the role of size, morphology and crystallinity in the dissolution behaviour of CaP NPs and on their nitrate doping for potential use as (P,N)-nanofertilizers. Spherical fully amorphous NPs and apatite-amorphous nanoplatelets (NPLs) in a core-crown arrangement are studied by combining forefront Small-Angle and Wide-Angle X-ray Total Scattering (SAXS and WAXTS) analyses. ­Ca2+ ion release rates difer for spherical NPs and NPLs demonstrating that morphology plays an active role in directing the dissolution kinetics. Amorphous NPs manifest a rapid loss of nitrates governed by surface-chemistry. NPLs show much slower release, paralleling that of ­Ca2+ ions, that supports both detectable nitrate incorporation in the apatite structure and dissolution from the core basal faces.Fondazione Cariplo 2016-0648FEDER/Ministerio de Ciencia, Innovacion y Universidades-Agencia Estatal de Investigacion (FEDER/MCIU/AEI, Spain) through the project NanoVIT RTI-2018-095794-A-C22FEDER/Ministerio de Ciencia, Innovacion y Universidades-Agencia Estatal de Investigacion (FEDER/MCIU/AEI, Spain) through the project NanoSmart RYC-2016-21042FEDER/MCIU/AEI within the Juan de la Cierva Program (JdC2017

Reducing Nitrogen Dosage in Triticum durum Plants with Urea-Doped Nanofertilizers

Nanotechnology is emerging as a very promising tool towards more efficient and sustainable practices in agriculture. In this work, we propose the use of non-toxic calcium phosphate nanoparticles doped with urea (U-ACP) for the fertilization of Triticum durum plants. U-ACP nanoparticles present very similar morphology, structure, and composition than the amorphous precursor of bone mineral, but contain a considerable amount of nitrogen as adsorbed urea (up to ca. 6 wt % urea). Tests on Triticum durum plants indicated that yields and quality of the crops treated with the nanoparticles at reduced nitrogen dosages (by 40%) were unaltered in comparison to positive control plants, which were given the minimum N dosages to obtain the highest values of yield and quality in fields. In addition, optical microscopy inspections showed that Alizarin Red S stained nanoparticles were able to penetrate through the epidermis of the roots or the stomata of the leaves. We observed that the uptake through the roots occurs much faster than through the leaves (1 h vs. 2 days, respectively). Our results highlight the potential of engineering nanoparticles to provide a considerable efficiency of nitrogen uptake by durum wheat and open the door to design more sustainable practices for the fertilization of wheat in fields.This research was funded by Fondazione CARIPLO (project no. 2016-0648: Romancing the stone: size-controlled HYdroxyaPATItes for sustainable Agriculture–HYPATIA) and the Spanish Ministerio de Ciencia, Innovación y Universidades (MCIU/AEI/FEDER) with the Projects NanoSmart (RYC-2016-21042) and NanoVIT (RTI-2018-095794-A-C22). GBRR also acknowledges the Spanish MICINN for her postdoctoral contract within the Juan de la Cierva Program (JdC-2017)

Characterization of archaeological bones from the Al Khiday cemetery (Central Sudan): structure and microstructure of diagenetically altered bioapatite

Bone is a composite material constituted by the association of an organic matrix and bioapatite nano-crystals. Human bones, frequently recovered from archaeological contexts, represent a valuable source of information on health, demography, age, diet and mobility of ancient populations as well as on environmental conditions experienced. However the reliability of such information depends on the preservation state of bone material and its constituents, i.e. the preservation of the in vivo chemical and isotopic composition. Bone alteration is caused by taphonomic and diagenetic processes, mainly driven by environmental conditions, affecting bones since the death of the individual and during burial. Therefore, a diagenetic study on archaeological bones, aiming to accurately determine their preservation state, taking into account the archaeological and palaeoenvironmental contexts, is a fundamental step when retrieving information by chemical or isotopic analyses. Based on this perspective, this research project is mainly addressing the radiocarbon dating of the bioapatite fraction of human bones, coming from the archaeological site 16D4 – Al Khiday 2 (Sudan) and the assessment of the reliability of results. At 16D4, a multi-stratified cemetery was excavated and several burial phases were recovered. In fact, the site was used as a burial ground at different periods along almost the entire Holocene. The well-defined archaeological context provided a set of samples suitable to investigate the reliability of the radiocarbon dating of bioapatite as well as the influence of environmental/climatic changes, occurring in Central Sudan along the Holocene, on bone diagenesis. Firstly a multi-disciplinary study on bones and associated soil sediments has been carried out, in order to define the preservation state of bones as well as to provide a model for diagenetic processes taking into account pedogenic processes and changes in environmental, climatic and local burial conditions. Based in the established model for diagenetic alteration of these bones, radiocarbon dating on selected bioapatite samples was performed and reliability of results discussed. Characterization of bone samples was carried out by optical and scanning electron microscopy, X-ray computed micro-tomography, X-ray powder diffraction, Fourier transform infrared spectroscopy and micro-Raman spectroscopy. Samples of pedogenic calcrete horizon, found at the 16D4 site, were analysed by optical, cathodoluminescence, and scanning electron microscopy. Bone and calcrete samples were prepared for 14C-AMS dating. Results from this case study prove that the radiocarbon dating of bioapatite for heavily altered bone samples may not be reliable. Characterization of bones and associated soil sediments provided valuable information on the diagenetic history of bones and on the influence of changes in environmental and local burial conditions on bone preservation. Moreover, results highlight the relevance of a multi-disciplinary approach to the study of the archaeological and palaeoenvironmental contextsIl tessuto osseo è composto principalmente da una frazione organica e una minerale, detta bioapatite. Lo studio di ossa umane, frequentemente rinvenute durante scavi archeologici, forniscono importanti informazioni sulla salute, demografia, antichità, dieta e mobilità di popolazioni vissute nel passato, nonché informazioni riguardo alle condizioni paleo-ambientali. Tuttavia, l’affidabilità di queste informazioni dipende molto dallo stato di conservazione delle ossa stesse, ed in particolare dalla conservazione della loro originale composizione chimica e isotopica. L’alterazione delle ossa è dovuta a processi tafonomici e diagenetici, principalmente influenzati dalle condizioni climatico-ambientali, che interessano le ossa dalla morte dell’individuo e durante il seppellimento. Di conseguenza, lo studio della diagenesi di ossa archeologiche, che mira a determinarne lo stato di conservazione, tenendo in considerazione il relativo contesto archeologico e paleo-ambientale, è di fondamentale importanza nell’interpretazione di risultati ottenuti da analisi chimiche e isotopiche. Sulla base di queste considerazioni si inserisce il presente progetto di ricerca, finalizzato alla datazione al radiocarbonio della bioapatite di ossa umane provenienti dal sito archeologico 16D4 – Al Khiday 2 (Sudan) e a determinarne l’affidabilità. Lo scavo del sito 16D4 ha portato alla luce un cimitero caratterizzato da diverse fasi di sepoltura, appartenenti a differenti periodi di uso cimiteriale dell’area cronologicamente distribuiti durante l’Olocene. Questo particolare contesto archeologico fornisce un interessante caso studio che permette di valutare l’affidabilità della datazione sulla bioapatite e allo stesso tempo di studiare l’influenza dei cambiamenti climatici, avvenuti in Sudan centrale durante l’Olocene, sulla diagenesi delle ossa. Prima di procedere con la datazione al radiocarbonio, campioni di ossa e di suoli (campionati sul sito) sono stati esaminati con approccio multidisciplinare al fine di determinare lo stato di conservazione delle ossa e caratterizzare la diagenesi delle ossa tenendo in considerazioni processi pedogenetici cambiamenti delle condizioni climatico–ambientali e di seppellimento. Successivamente alcuni campioni di bioapatite sono stati datati al radiocarbonio e l’affidabilità dei risultati è stata discussa. I campioni di ossa sono stati analizzati mediante microscopia ottica ed elettronica a scansione, diffrazioni a raggi X su polvere, micro-tomografia a raggi X, spettroscopia IR a trasformata di Fourier e micro-Raman. I campioni di un orizzonte carbonatico, campionati sul sito archeologico, sono stati analizzati mediante microscopia ottica, in catodoluminescenza e elettronica a scansione. Le datazione al radiocarbonio mediante spettrometria si massa con acceleratore sono state ottenute su campioni di bioapatite e di carbonati pedogenetici. I risultati ottenuti su questo caso studio dimostrano che la datazione di bioapatite di campioni molto alterati non è affidabile. Lo studio di ossa e suoli ha fornito importanti informazioni sull’ alterazione diagenetica delle ossa e sulla sua dipendenza dai cambiamenti climatici e ambientali avvenuti nella regione durante l’Olocene abbiano. Inoltre, i risultati ottenuti in questo lavoro evidenziano l’importanza di un approccio multidisciplinare allo studio di contesti archeologici e paleo-ambiental

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

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 analyse