Burnt Samples Research Articles

The importance of U-series disequilibrium of sediments in luminescence dating: A case study at the Roc de Marsal Cave (Dordogne, France)

A multidisciplinary study of the Roc de Marsal Cave gave us the opportunity to re-examine the known problem posed by U-series disequilibria in sediments in the field of palaeodosimetric dating. Apart from burnt flints and heated limestones, the material being dated, THAT IS our principal concern here, is made of burnt sediment samples collected from a reddish layer that forms the very base of the Roc de Marsal Mousterian sequence (Couche B). U-series disequilibria of long life nuclides in sediments were observed: as a general trend, the activity of 238U is greater than that of 226Ra. Important discrepancies in age determination can occur according to the origin of the disequilibrium and its kinetics. To characterise these ancient modifications of radioactivity and constrain the range of possible variations of annual doses, a statistical study of 238U, 226Ra and 232Th activities, measured by gamma spectrometry, was carried out. It shows that the sediment was mainly enriched in mobile uranium. This conclusion is in accordance with the results of complementary measurements of 230Th and 234U performed by alpha spectrometry. On the kinetics side, two models of time-variation of U and daughter concentrations are compared, taking experimental data into account. A detailed presentation of the methodology and the method of calculation of dose rates, and particularly time-averaged dose rates in such a situation, is given.

Evolution of composition and content of soil carbohydrates following forest wildfires

The time evolution of the content and composition of carbohydrates was studied in the surface layer of forest soils non-affected and affected by wildfires. The low- and high-severity fires caused an immediate reduction of the C present as carbohydrates of 34% and 47–55%, respectively, which was due to the decrease of both hexoses and pentoses in two hydrolysis fractions (hydrolysate-A, non-cellulosic polysaccharides; hydrolysate-B, cellulosic polysaccharides). Carbohydrates tended to recover with time; however, values had still not reached the amounts found in the corresponding unburnt samples after 12–15 months. No difference between the unburnt and burnt samples was observed in the distribution of the neutral sugars in the hydrolysates over time. On a percentage basis, 72–92% of the total neutral sugars was extracted in hydrolysate-A (59 ± 7% hexoses; 24 ± 7% pentoses) and the rest, 8–28%, in hydrolysate-B (15 ± 5% hexoses; 2 ± 1% pentoses). The contribution of hexoses and pentoses to the neutral sugar pool was different between the two hydrolysis fractions being the hexoses/pentoses ratio higher for hydrolysate-B than for hydrolysate-A. The results also showed that the proportion of soil C present as carbohydrates-C rather than the total carbohydrates content should be used for monitoring short- and medium-term changes induced by fire in soil organic matter quality.

Study Aiming the Use of Powder Waste Reject from the Sanitary Ware Production in Mass for Red Ceramics

A procedure that comes being studied for the exploitation of powder waste rejected from the sanitary ware production is the incorporation in mass for red ceramics. Objective of this work is to present the results gotten in the incorporation of this rejects. The used clay was from ceramics industries of the Jundiai region, SP. Spherical bodies test samples had been conformed incorporating 1%, 5%, 10%, 20% and 30% of the powder waste in mass. These bodies had been evaluated on compression resistance after dried to 110°C and to color after burns to 950°C. The composition that presented better results had been conformed by extrusion in prismatic bodies test samples. Again, the dried to 110°C and burnt to 950°C bodies test samples had been evaluated on flexion resistance but to linear retraction too. It was measured the ceramic properties of the burnt bodies test samples. Results indicate that there is a great potential in the formula with 30% incorporation of powder waste in mass. Comparative assays were made being used a mixture without incorporation of the denominated white reject.

Analysis of the 1:5 soil: water extract in burnt soils to evaluate fire severity

Abstract This paper studies fire severity through changes in the composition of the 1:5 soil: water extract in burnt and unburnt samples collected after a wildfire that affected 7.1 ha of mountainous broom scrub (Teide broom, Spartocytisus supranubius L.) in Tenerife (Canary Islands). Soil samples were collected over a regular sampling grid and analysed for pH, electrical conductivity (E.C.), and soluble cations (Ca+2, Mg+2, K+, and NH4+–N) and anions (P, SO4− 2–S, and NO3−‑N). A visual estimation of fire effects on individual broom plants was also conducted. The results show significant differences between burnt and unburnt samples for pH, E.C. and soluble ions (except for P), which generally agrees with data reported in the literature. Although fire severity, as estimated from the degree of fuel combustion, correlated significantly with most of the studied parameters, the qualitative fire severity indexes failed to discriminate sample groups apparently exposed to moderate fire severity conditions. Multivariate statistical analysis (PCA) allowed extracting two main factors, capable to account for 88% of total variability, after rejecting three variables (inorganic N-forms and K+). These factors were related to fire severity and pH-dependent Ca+2 and P reactions, respectively.

Immediate effects of wildfires on water repellency and aggregate stability in Mediterranean calcareous soils

Alkaline soils are considered much less prone to developing water repellency induced by fire than acidic soils. Here we report on the persistence of water repellency present in calcareous soils immediately after wildfires in 10 burned areas in SE Spain, its distribution in different aggregate size fractions (< 2, 2–1, 1–0.5, 0.5–0.25 and < 0.25 mm) and on results from aggregate stability tests. We also distinguished between soil samples taken beneath pine (Pinus halepensis) and beneath understory vegetation. Burning appears to have increased the frequency of water repellency occurrence, with 74% of burned samples being classified as water repellent compared to 33% from unburned terrain in the composite fraction (< 2 mm). The persistence of water repellency after fire was highly variable but nevertheless showed statistical differences at p < 0.001 comparing burned vs unburned. Moreover, statistical differences in the persistence of water repellency were found in soil samples taken from beneath pine between burned and unburned, and also beneath understory vegetation. Results showed that soil beneath understory tend to have lower values of water repellency persistence than soil beneath pine. Burned soils showed higher aggregate stability. A positive tendency was observed between aggregate stability and water repellency. The observed changes in WR and AS could have implications for soil hydrological behaviour.

Influence of environment on the mechanical behaviour of mature human enamel

Objectives To investigate the role of different environments in regulating the mechanical behaviour of mature human enamel. Methods Healthy enamel samples were subjected to different environmental treatments such as ethanol dehydration, water re-hydration, desiccation at room temperature, and after heating (burnt) to 300 °C. Nanoindentation tests were done on all samples for determination of elastic modulus, hardness and indentation creep behaviour. Scanning electron microscopy (SEM) was used to observe surfaces and indentation impressions of different treated samples. Results Statistically significant differences of the mechanical properties were found following the various treatments. Burnt sample had the highest elastic modulus and hardness of ∼115 and ∼6 GPa, respectively, while the re-hydrated sample showed the lowest values of ∼95 and ∼4 GPa. The creep deformation showed the inverse response to the environment-induced elastic modulus results with negligible creep found for the burnt specimens. SEM showed that, although no significant structural changes were found for burnt samples after heating, there was much more cracking about the residual indentation impression. Conclusions Because of the chemical and thermal stability of hydroxyapatite under the experimental conditions investigated, differences of mechanical behaviour of enamel are rationalized in terms of changes to the matrix proteins and loss of water within enamel. These results indicate that matrix proteins play an important role in regulating the mechanical behaviour of enamel as a biocomposite.

Chemical composition of glass and crystalline phases in coarse coal gasification ash

A procedure has been developed for determining the chemical composition and relative abundance of the amorphous or glassy material, as well as crystalline phases, present in coarse coal gasification ash, in order to assist in predicting the behaviour of the material in cement/brick/concrete applications. The procedure is based on a combination of quantitative X-ray diffraction (XRD), chemical analysis and electron microprobe studies. XRD analysis indicates that the clinker samples contain a number of crystalline high temperature phases, including anorthite, mullite, cristobalite, quartz and diopside. Quantitative evaluation using Rietveld-based techniques has been used to determine the percentages of both the individual crystalline phases and the glass component. These data were then combined with the chemistry of the crystalline phases and the overall chemical composition of the ash to estimate the chemical composition of the glass phase, which is typically the most abundant component present in the different materials. Although there is some degree of scatter, comparison between the inferred glass composition from XRD and bulk chemistry and actual data on the glass composition using electron microprobe techniques suggest that the two approaches are broadly consistent. The microprobe further indicates that a range of compositions are present in the glassy and crystalline components of the ashes, including Si–Al-rich glass, metakaolin and Fe–Ca–Mg–Ti phases, as well as quartz, anorthite and an aluminophosphate material. Electron microprobe and XRD studies also show that pyrrhotite (FeS), representing a high temperature transformation product of pyrite, is present in some clinker and partially burnt carbonaceous shale samples.

Characteristics of burnt meat in cultured yellowtail Seriola quinqueradiata

In order to understand the characteristics of burnt meat in cultured yellowtail Seriola quinqueradiata, fish were kept at two different temperatures (13 and 30°C) and slaughtered by either spinal cord destruction (SCD) or suffocation in air (SA). Early postmortem changes during storage at 32°C were analyzed by rheological, biochemical, and histological methods. The burnt meat (with lightness parameter, L*≥55) was observed at 1-h storage in the SA 30°C group, at 2 h in SCD 30°C, and at 4 h in SA 13°C; meat was normal for the SCD 13°C group until 6h of storage. Breaking strength scores were higher for the normal meat (200 g/cm2) than burnt meat (70 g/cm2) at 4 h of storage. Expressible water content was higher for the burnt meat than for the normal meat. Adenosine triphosphate concentrations for the SCD groups were higher than for the SA counterparts. Moreover, pH decrease was much faster in the 30°C groups, showing pH 5.6 at 2 h of storage. A negative correlation between the pH and lactic acid contents in muscle (P<0.001) was found. Histological analysis evidenced a larger pericellular area (40%) in the burnt samples than in the normal samples (16%). It was confirmed that a higher fish-keeping water temperature and a stressful slaughter method (faster glycolytic process) were determinative factors that influence the occurrence of burnt muscle in yellowtail, and that the effect of the former is larger than the latter.

Establishing fire incidence in temperate soils using magnetic measurements

Natural, unburnt topsoil samples from the Cotswolds region of England and samples from archaeological contexts in the UK and Hungary, some of which are known to have been affected by burning, have been used to identify a distinctive magnetic ‘signature’ linked to the effects of fire on magnetic properties. A combination of bulk, low field ( χ lf) and frequency dependent ( χ fd) magnetic susceptibility and normalized anhysteretic remanent magnetization ( χ ARM) measurements have been used on both unburnt and experimentally burnt samples from the Cotswolds and on the archaeological samples. Complementary determinations were made for both sets of samples of the maximum potential susceptibility ( χ max) and, hence, percentage fractional conversion ( χ conv), which provides independent evidence of burning. The results show that the ferrimagnetic mineral assemblages produced as a result of fire have a significantly finer grain size than those arising from weathering and soil formation alone. Burning thus gives rise to a distinctive envelope of values on a bilogarithmic plot of χ ARM/ χ fd versus χ ARM/ χ lf. Such a diagram provides a convenient basis for identifying magnetic signatures in soils, archaeological materials and palaeosols that have arisen mainly through burning.

Temporal evolution of organic carbon and nitrogen forms in volcanic soils under broom scrub affected by a wildfire

The evolution of total N, total oxidizable C, water-soluble NH(4)(+)-N, exchangeable NH(4)(+)-N and soluble NO(3)(-)-N was studied in Canarian volcanic soils under mountainous legume scrub affected by a wildfire by June 2003. Three systematic soil samplings in the burned area and in neighbouring non-burned sampling points were carried out 3, 7 and 12 months after the fire event. The results showed an important mobilization of N (as total N and soluble and exchangeable NH(4)(+)-N) in the soil within the burned area at short term, with a simultaneous depletion of nitrates. Later on, the water-soluble NH(4)(+)-N levels remained nearly constant along the study period in the burned area, whereas the exchangeable NH(4)(+) decreased progressively. Nitrates were found to increase inside and outside the burned area, but the increase rate was much higher for the burned samples. Total N fluctuated along the year, although its levels were generally higher in the burned area. However, such a response pattern of N to fire in this environment was insufficient to prompt the recovery of the plant cover.

The Rhafas Cave (Morocco): Chronology of the mousterian and aterian archaeological occupations and their implications for Quaternary geochronology based on luminescence (TL/OSL) age determinations

The Middle Palaeolithic chronology of the Maghreb region of North Africa is poorly known because of the paucity of sites with a long stratigraphy and the limited number of available radiometric dates. In this paper, we report the age-estimates obtained by the TL and OSL methods on sediments and burnt lithic samples from the Rhafas Cave in Eastern Morocco. Our results indicate that the Mousterian is largely earlier than 100 ka, that the latest Mousterian dates to OIS 5 between 90–80 ka and the Mousterian to Aterian transition occurred about 70–80 ka, at the end of OIS 5 or during OIS 4. These dates will be most useful in the construction of a chronological framework of this unique sequence and for the interpretation of paleoenvironmental information.

Spiders, spinifex, rainfall and fire: Long-term changes in an arid spider assemblage

Understanding the spatial and temporal patterning of biota is critical to conserving biodiversity in arid regions. For mammals and reptiles, rainfall and fire are important forces determining patterns. Few studies consider these factors for invertebrates and even fewer over an extended period. Spiders were pitfall trapped over 14 years (1989–2003) as part of an experimental fire study in the Great Victoria Desert, Western Australia. Spider abundance decreased immediately after fire, but yearly variation confounded the interpretation of results. Species richness showed no clear pattern in response to fire. Spider species composition showed significant changes between sampling months and between burnt and long unburnt samples within the months of March and December, but not October. Rainfall appears the dominant driving force in this system with less pronounced fire effects. High rainfall during the previous February–April was correlated with increased spider abundance in March samples the following year. Given the highly seasonal structure of spider assemblages, favourable weather during mating and juvenile development may increase recruitment the following season. We conclude that to be successful in conserving biodiversity in arid Australia by re-instating anthropogenic fire regimes, it is vital to understand the mediating impact of rainfall.

Comparing electronic probes for volumetric water content of low‐density feathermoss

PurposeFeathermoss is ubiquitous in the boreal forest and across various land‐cover types of the arctic and subarctic. A variety of affordable commercial sensors for soil moisture content measurement have recently become available and are in use in such regions, often in conjunction with fire‐susceptibility or ecological studies. Few come supplied with calibrations suitable or suggested for soils high in organics. Aims to test seven of these sensors for use in feathermoss, seeking calibrations between sensor output and volumetric water content.Design/methodology/approachMeasurements from seven sensors installed in live, dead and burned feathermoss samples, drying in a controlled manner, were compared to moisture content measurements. Empirical calibrations of sensor output to water content were determined.FindingsAlmost all of the sensors tested were suitable for measuring the moss sample water content, and a unique calibration for each sensor for this material is presented. Differences in sensor design lead to changes in sensitivity as a function of volumetric water content, affecting the spatial averaging over the soil measurement volume.Research limitations/implicationsThe wide range of electromagnetic sensors available include frequency and time domain designs with variations in wave guide and sensor geometry, the location of sensor electronics and operating frequency.Practical implicationsThis study provides information for extending the use of electromagnetic sensors to feathermoss.Originality/valueA comparison of volumetric water content sensor mechanics and design is of general interest to researchers measuring soil water content. In particular, researchers working in wetlands, boreal forests and tundra regions will be able to apply these results.

Modeling Solid Sample Buming

Black PMMA was burned in the cone calorimeter in two orientations (horizontal and vertical), at imposed radiant heat fluxes of (0, 5, 10, 25, 50, and 75) kW/m2, and the visual appearance, flame size, heat release rate, and mass loss rate were recorded. Various other experimental parameters were varied. The topography of the burned samples was also recorded, and the heat flux to the sample was inferred from the variation of the mass loss over the surface of the sample. The burning was subsequently modeled using a computational fluid dynamics (CFD) model, and various experimental, numerical, and physical parameters were varied in the simulations. The results provide an indication of the ability of the fire model to predict the burning of a simple solid sample, and also provide guidance concerning the importance of various experimental and numerical parameters for accurate simulation.

Effects of forest fire on the level and distribution of PCDD/Fs and PAHs in soil

Forest fires are believed to produce polychlorinated dibenzo- p-dioxins and dibenzofurans (PCDD/Fs); however, there is no firm evidence supporting this conjecture. To address this issue, we investigated whether PCDD/Fs and polycyclic aromatic hydrocarbons (PAHs) are formed by forest fires. The present work takes the indirect approach of measuring the levels of PCDD/Fs and PAHs in soil and ash samples 1, 5 and 9 months after forest fires. To determine if PCDD/Fs or PAHs were formed during forest fires, the levels of PCDD/Fs and PAHs measured in the burnt soil samples were compared with those in the corresponding unburnt soil samples. One month after forest fires, the concentrations of PCDD/Fs and PAHs in burnt soils were higher than in the corresponding unburnt soils. In addition, the homologue profiles differed between the burnt and unburnt soils. Five months after forest fires, however, the concentrations of PCDD/Fs and PAHs in the burnt soils were similar to those in unburnt soils. The data presented here strongly suggest that PCDD/Fs and PAHs form during forest fires and are then introduced into the soil. The results further suggest that the ash resulting from the combustion of wood and other organic matter is the main agent influencing the concentration of PCDD/Fs and PAHs in the soil.

Detection of Burning of Plant Materials in the Archaeological Record by Changes in the Refractive Indices of Siliceous Phytoliths

The most resilient remains of plants in most archaeological sites are the siliceous phytoliths—special cells that are partially or completely silicified during the plant's life. These cells have characteristic morphologies, and thus the phytoliths can often be used to identify the taxonomic affinities of plants brought to an archaeological site. In order to determine what they were used for, other means of analysis are needed. We present here a method to distinguish burnt from unburnt phytolith assemblages. The method is based on measuring the refractive index (RI) of individual phytoliths. The phytoliths even from a single plant have a range of RI values. Burning a phytolith sample causes a shift to higher RI. Comparing burnt and unburnt samples we demonstrate that it is possible to differentiate between them based on the fraction of phytoliths with RI higher than 1·440. This serves as a basis for a simplified mode of measurement that requires only the use of a petrographic light microscope and a mineral oil of RI 1·440. We apply the simplified method to two Natufian samples from Hayonim cave (Western Galilee, Israel).

The effect of foreign ions on the reactivity of the CaO–SiO2–Al2O3–Fe2O3 system: Part II: Cations

The subject of this paper is the effect of foreign cations on the reactivity of the CaO–SiO2–Al2O3–Fe2O3 system. One reference mixture and eighteen modified mixtures, prepared by mixing the reference sample with 1% w/w of chemical grade MnO2, CuO, V2O5, PbO, CdO, ZrO2, Li2O, MoO3, Co2O3, NiO, WO3, ZnO, Nb2O5, CrO3, Ta2O5, TiO2, BaO2 and H3BO3 were studied. The effect on the reactivity is evaluated on the basis of the free lime content in samples sintered at 1200 and 1450 °C. At 1200 °C, the reactivity of the mixture is greatly increased in the presence of Cu and Li oxides. Based on their effect at 1450 °C, the added elements can be divided into three groups. W, Ta, Cu, Ti and Mo show the most positive effect, decreasing the free CaO (fCaO) content by 30–60%, compared with the pure sample. Cr and B cause an increase of fCaO content, while the rest of the elements exhibit a marginal positive effect. According to their volatility at 1450 °C, the added compounds can be subdivided into three groups of low (Ti4+, Cu2+, Mo6+, W+6, V5+, Zn2+, Zr4+), moderate (Cr6+, Co3+, Ni2+, Mn4+) and high volatility (Cd2+, Pb2+). All burned samples, analyzed by means of X-ray diffraction, have a final mineralogical composition, which corresponds to the structure of a typical clinker.

Rock-magnetic properties of TRM carrying baked and molten rocks straddling burnt coal seams

The subsurface spontaneous combustion of coal seams in Xinjiang (NW China) during Pleistocene to recent times produced large areas of thermally altered sedimentary rocks with large magnetic moments. The natural remanent magnetization (NRM) and thermoremanent magnetization (TRM) intensities and low-field susceptibilities of such combustion-metamorphic rocks range from 0.1 to 10 A/m and 100×10 −4 to 1000×10 −4 SI, respectively, which is two to three orders of magnitude higher than values typical of their sedimentary protoliths. The dominant magnetic carriers in the burnt rocks appear to include relatively pure forms of magnetite, maghemite and hematite as well as more complex spinel phases. These magnetic phases mainly occur as fine pseudo-single-domain (PSD) particles. Conspicuous is the presence of pure metallic iron (αFe) in some samples. This highly magnetic phase is inferred to appear as more or less elongated super paramagnetic and single-domain (SD) inclusions in host silicate phases, which prevent them from oxidizing. The SD αFe particles can carry a highly stable remanence, having remanent coercivities ranging 70−140 mT. The ARM and IRM stability of all burnt rock samples to alternating fields is shown to be relatively high; median destructive fields, B (1/2)A and B (1/2)I, respectively, range of 25−46 and ∼20−30 mT for dominant spinel-bearing samples, 34−36 and 47−53 mT for maghemite–hematite-bearing samples, and 48−89 and 64−84 mT for metallic iron-bearing samples. Consequently, burnt rocks are high-quality geomagnetic field recorders. Their very nature makes them useful for paleointensity determinations, although age determination is a limiting factor. Furthermore, remanence intensities and susceptibilities of these magnetically enhanced rocks are sufficient to produce observable magnetic anomalies. This property illustrates the potential to delineate the areal extent and depth of (extinct) coal fires with magnetic exploration. Such information is necessary to refine estimates of hazardous CO 2 emission and furthers our understanding of natural coal fires.

Degradation of poly(methyl methacrylate) (PMMA) with aluminum nitride and alumina

AbstractThis paper deals with the thermal and thermal‐oxidative degradation of pure poly(methyl methacrylate) (PMMA), PMMA/A1N and PMMA/Al2O3 composites. Kinetic parameters were determined from the weight loss data using non‐isothermal Thermogravimetric Analysis (TGA). The amount and morphology of the carbon residue in the burnt samples under N2 and air atmospheres were also investigated using a Leco combustion analyzer. This study also showed that the normally accepted three‐stage polymer thermal degradation, and hence three regions of Arrhenius linearity, can be treated with one value of activation energy. This is a basic departure from the normally accepted three different regions and applying the same diffusion equation (such as Jander diffusion) separately to each region. In nitrogen atmosphere, the activation energy of pure PMMA was 129.4 kJ/mol; however, the activation energies of 14% PMMA/AlN and PMMA/Al2O3 were found to be 119.5 and 118.2 kJ/mol, respectively.

Cremation practices and the survival of ancient DNA: burnt bone analyses via RAPD-mediated PCR

Numerous burial rites have been developed in different time periods of human cultural evolution. One of the most interesting burial practices was the ritual cremation of human bodies. Due to the respective cultural and religious background, brand graves are known where human remains had been buried together with burnt bones of animal origin. To date, burnt bone samples have been refractory to PCR-mediated amplification. D/L values of aspartic acid far greater than 80 x 10(-3) were measured in the samples thus indicating the presence of severely nicked and fragmented nucleic acids. In order to differentiate between burial gift of animal origin and burnt human specimens we established a highly sensitive protocol that addresses all the shortcomings connected to degraded ancient DNA. With the novel procedure it was possible to classify 4 specimens ranging from 2,000-5,000 BP on the basis of mitochondrial DNA sequences.