Shell mineralogy and chemistry - Arctic bivalves in a global context.

This study provided new data on shell mineralogy in 23 Arctic bivalve species. The majority of examined species had purely aragonitic shells. Furthermore, we measured concentrations of Al, Ba, Ca, Fe, K, Mg, Mn, Na, P, S, Sr and Zn in 542 shells representing 25 Arctic bivalve species. Species-related differences in concentrations of specific elements were significant and occurred regardless of locations and water depths. This observation implies the dominance of biological processes regulating elemental uptake into the skeleton over factors related to the variability of abiotic environmental conditions. Analysis of the present study and literature data revealed that the highest concentrations of metals were observed in bivalves collected in the temperate zone, with intermediate levels in the tropics and the lowest levels in polar regions. This trend was ascribed mainly to the presence of higher anthropogenic pressure at temperate latitudes being a potential source of human-mediated metal pollution.

Evidence for the cooking of fish 780,000 years ago at Gesher Benot Ya'aqov, Israel.

Although cooking is regarded as a key element in the evolutionary success of the genus Homo, impacting various biological and social aspects, when intentional cooking first began remains unknown. The early Middle Pleistocene site of Gesher Benot Ya'aqov, Israel (marine isotope stages 18-20; ~0.78 million years ago), has preserved evidence of hearth-related hominin activities and large numbers of freshwater fish remains (>40,000). A taphonomic study and isotopic analyses revealed significant differences between the characteristics of the fish bone assemblages recovered in eight sequential archaeological horizons of Area B (Layer II-6 levels 1-7) and natural fish bone assemblages (identified in Area A). Gesher Benot Ya'aqov archaeological horizons II-6 L1-7 exhibited low fish species richness, with a clear preference for two species of large Cyprinidae (Luciobarbus longiceps and Carasobarbus canis) and the almost total absence of fish bones in contrast to the richness of pharyngeal teeth (>95%). Most of the pharyngeal teeth recovered in archaeological horizons II-6 L1-7 were spatially associated with 'phantom' hearths (clusters of burnt flint microartifacts). Size-strain analysis using X-ray powder diffraction provided evidence that these teeth had been exposed to low temperature (<500 °C), suggesting, together with the archaeological and taphonomic data, that the fish from the archaeological horizons of Area B had been cooked and consumed on site. This is the earliest evidence of cooking by hominins.

Polymorphism of CaCO3 and the variability of elemental composition of the calcareous skeletons secreted by invertebrates along the salinity gradient of the Baltic Sea.

Biomineralization is of great importance in ecosystem functioning and for the use of carbonate skeleton as environmental proxies. Skeletal formation is controlled to different degrees by environmental parameters and biological mechanisms. While salinity is one of the most important factors affecting ecological processes and ocean physiochemistry, the goal of this investigation was to identify how salinity influences the mineral type and the concentrations of chemical elements in the whole skeleton of invertebrates from the Baltic Sea. In this model system, the surface salinity decreases from marine values (27.2) to almost fresh water (6.1). The selected organisms, mussels (Mytilus spp.), bryozoans (Einhornia crustulenta, Cribrilina cryptooecium, Cryptosula pallasiana, Electra pilosa, Escharella immersa), barnacles (Amphibalanus improvisus, Semibalanus balanoides), and polychaetes (Spirorbis tridentatus), precipitated skeleton composed of calcite and aragonite, most likely as a result of various interacting environmental and biological factors. The concentrations of all elements in bulk skeleton were highly variable between species from the same location, underlining the role of the biological mechanisms in skeletal formation. The concentration of Ca, Mg, Sr, and Na increased in the bulk skeleton of stenohaline organisms with increasing salinity, while in the bulk skeleton of euryhaline species, only the concentration of Na increased with increasing salinity. The concentrations of Mn, Ba, Cu, Pb, Y, V, Cd, and U in the skeleton of euryhaline species generally decreased at higher salinities, most likely reflecting the lower bioavailability of elements at higher salinity. However, the concentrations of elements in the skeleton of stenohaline organisms were highly variable with no clear salinity impact. This study suggests that, although the composition of skeleton of calcifying organisms along the salinity gradient of the Baltic Sea is to a large extent affected by biological mechanisms, it also reflects the responses to environmental conditions.

Skeletal carbonate mineralogy of Scottish bryozoans.

This paper describes the skeletal carbonate mineralogy of 156 bryozoan species collected from Scotland (sourced both from museum collections and from waters around Scotland) and collated from literature. This collection represents 79% of the species which inhabit Scottish waters and is a greater number and proportion of extant species than any previous regional study. The study is also of significance globally where the data augment the growing database of mineralogical analyses and offers first analyses for 26 genera and four families. Specimens were collated through a combination of field sampling and existing collections and were analysed by X-ray diffraction (XRD) and micro-XRD to determine wt% MgCO3 in calcite and wt% aragonite. Species distribution data and phylogenetic organisation were applied to understand distributional, taxonomic and phylo-mineralogical patterns. Analysis of the skeletal composition of Scottish bryozoans shows that the group is statistically different from neighbouring Arctic fauna but features a range of mineralogy comparable to other temperate regions. As has been previously reported, cyclostomes feature low Mg in calcite and very little aragonite, whereas cheilostomes show much more variability, including bimineralic species. Scotland is a highly variable region, open to biological and environmental influx from all directions, and bryozoans exhibit this in the wide range of within-species mineralogical variability they present. This plasticity in skeletal composition may be driven by a combination of environmentally-induced phenotypic variation, or physiological factors. A flexible response to environment, as manifested in a wide range of skeletal mineralogy within a species, may be one characteristic of successful invasive bryozoans.

Manganese translocation and concentration on Quercus cerris decomposing leaf and wood litter by an ascomycetous fungus: an active process with ecosystem consequences?

Decomposing fungi translocate manganese (Mn) as demonstrated by the fact that Mn has been found to accumulate on decomposing leaves associated with individual fungal hyphae forming insoluble Mn(III,IV) oxides that remain concentrated in diffuse patches. Here, we studied Mn translocation and precipitation by the saprophytic fungus Alternaria sp. strain FBL507 both on naturally decomposing oak leaves and in vitro experiments. Manganese was translocated and precipitated in beads and encrustations along the fungal hyphae. The combination of X-ray diffraction and scanning electron microscopy-energy dispersive X-ray spectroscopy chemical data showed that the precipitates found on leaves were rhodochrosite (MnCO3), birnessite ([Na, Ca, K]Mn2O4× 1.5H2O) and possibly Mn oxalate. The precipitates on wood were an amorphous Mn-O compound, probably MnO. Thus, Mn oxidation state in the precipitates spanned from +2 to +4, with +3 and +4 only in the birnessite on the leaves. In vitro experiments showed that Mn precipitates formed in living hyphae, suggesting the possibility that Mn precipitation is actively produced by the fungus. Such a possibility raises interesting questions regarding the role of readily available Mn in the activity of saprophytic fungi and other soil microorganisms, such as would result in a large involvement of Mn in the cycles of the major nutrient elements.

The Search for Hesperian Organic Matter on Mars: Pyrolysis Studies of Sediments Rich in Sulfur and Iron.

Jarosite on Mars is of significant geological and astrobiological interest, as it forms in acidic aqueous conditions that are potentially habitable for acidophilic organisms. Jarosite can provide environmental context and may host organic matter. The most common extraction technique used to search for organic compounds on the surface of Mars is pyrolysis. However, thermal decomposition of jarosite releases oxygen into pyrolysis ovens, which degrades organic signals. Jarosite has a close association with the iron oxyhydroxide goethite in many depositional/diagenetic environments. Hematite can form by dehydration of goethite or directly from jarosite under certain aqueous conditions. Goethite and hematite are significantly more amenable than jarosite for pyrolysis experiments employed to search for organic matter. Analysis of the mineralogy and organic chemistry of samples from a natural acidic stream revealed a diverse response for organic compounds during pyrolysis of goethite-rich layers but a poor response for jarosite-rich or mixed jarosite-goethite samples. Goethite units that are associated with jarosite, but do not contain jarosite themselves, should be targeted for organic detection pyrolysis experiments on Mars. These findings are extremely timely, as exploration targets for Mars Science Laboratory include Vera Rubin Ridge (formerly known as "Hematite Ridge"), which may have formed from goethite precursors. Key Words: Mars-Pyrolysis-Jarosite-Goethite-Hematite-Biosignatures. Astrobiology 18, 454-464.

Novel Multi-isotope Tracer Approach To Test ZnO Nanoparticle and Soluble Zn Bioavailability in Joint Soil Exposures.

Here we use two enriched stable isotopes, 68Znen and 64Znen (>99%), to prepare 68ZnO nanoparticles (NPs) and soluble 64ZnCl2. The standard LUFA 2.2 test soil was dosed with 68ZnO NPs and soluble 64ZnCl2 to 5 mg kg-1 each, plus between 0 and 95 mg kg-1 of soluble ZnCl2 with a natural isotope composition. After 0, 1, 3, 6, and 12 months of soil incubation, earthworms (Eisenia andrei) were introduced for 72 h exposures. Analyses of soils, pore waters, and earthworm tissues using multiple collector inductively coupled plasma mass spectrometry allowed the simultaneous measurement of the diagnostic 68Zn/66Zn, 64Zn/66Zn, and 68Zn/64Zn ratios, from which the three different isotopic forms of Zn were quantified. Eisenia andrei was able to regulate Zn body concentrations with no difference observed between the different total dosing concentrations. The accumulation of labeled Zn by the earthworms showed a direct relationship with the proportion of labeled to total Zn in the pore water, which increased with longer soil incubation times and decreasing soil pH. The 68Znen/64Znen ratios determined for earthworms (1.09 ± 0.04), soils (1.09 ± 0.02), and pore waters (1.08 ± 0.02) indicate indistinguishable environmental distribution and uptake of the Zn forms, most likely due to rapid dissolution of the ZnO NPs.

Size effect on the mineralogy and chemistry of Mytilus trossulus shells from the southern Baltic Sea: implications for environmental monitoring.

Mussels have the ability to control biomineral production and chemical composition, producing shells with a range of functions. In addition to biological control, the environment also seems to influence the process of biomineralization; thus, shells can be used as archives of ambient water parameters during the calcium carbonate deposition. Past and present environmental conditions are recorded in the shells in the form of various proxies including Mg/Ca or Sr/Ca ratios. For such proxies to be accurate and robust, the influence of biological effects including the size of studied organism must be examined and eliminated or minimized, so that the environmental signal can be efficiently extracted. This study considers mineralogy and elemental composition of shells representing four size classes of Mytilus trossulus from the Baltic Sea. Obtained results suggest that mineralogy and chemical composition change throughout the shell development due to most likely a combination of environmental and biological factors. The content of aragonite increases with increasing shell size, while the bulk concentrations of Na, Cd, Cu, U, V, Zn and Pb were found to decrease with increasing height of the shells. Therefore, using mussels for environmental monitoring requires analysis of individuals in the same size range.

Local geology controlled the feasibility of vitrifying Iron Age buildings.

During European prehistory, hilltop enclosures made from polydisperse particle-and-block stone walling were exposed to temperatures sufficient to partially melt the constituent stonework, leading to the preservation of glassy walls called 'vitrified forts'. During vitrification, the granular wall rocks partially melt, sinter viscously and densify, reducing inter-particle porosity. This process is strongly dependent on the solidus temperature, the particle sizes, the temperature-dependence of the viscosity of the evolving liquid phase, as well as the distribution and longevity of heat. Examination of the sintering behaviour of 45 European examples reveals that it is the raw building material that governs the vitrification efficiency. As Iron Age forts were commonly constructed from local stone, we conclude that local geology directly influenced the degree to which buildings were vitrified in the Iron Age. Additionally, we find that vitrification is accompanied by a bulk material strengthening of the aggregates of small sizes, and a partial weakening of larger blocks. We discuss these findings in the context of the debate surrounding the motive of the wall-builders. We conclude that if wall stability by bulk strengthening was the desired effect, then vitrification represents an Iron Age technology that failed to be effective in regions of refractory local geology.

Sulfate minerals: a problem for the detection of organic compounds on Mars?

The search for in situ organic matter on Mars involves encounters with minerals and requires an understanding of their influence on lander and rover experiments. Inorganic host materials can be helpful by aiding the preservation of organic compounds or unhelpful by causing the destruction of organic matter during thermal extraction steps. Perchlorates are recognized as confounding minerals for thermal degradation studies. On heating, perchlorates can decompose to produce oxygen, which then oxidizes organic matter. Other common minerals on Mars, such as sulfates, may also produce oxygen upon thermal decay, presenting an additional complication. Different sulfate species decompose within a large range of temperatures. We performed a series of experiments on a sample containing the ferric sulfate jarosite. The sulfate ions within jarosite break down from 500 °C. Carbon dioxide detected during heating of the sample was attributed to oxidation of organic matter. A laboratory standard of ferric sulfate hydrate released sulfur dioxide from 550 °C, and an oxygen peak was detected in the products. Calcium sulfate did not decompose below 1000 °C. Oxygen released from sulfate minerals may have already affected organic compound detection during in situ thermal experiments on Mars missions. A combination of preliminary mineralogical analyses and suitably selected pyrolysis temperatures may increase future success in the search for past or present life on Mars.

The α-ß phase transition in volcanic cristobalite.

Cristobalite is a common mineral in volcanic ash produced from dome-forming eruptions. Assessment of the respiratory hazard posed by volcanic ash requires understanding the nature of the cristobalite it contains. Volcanic cristobalite contains coupled substitutions of Al3+ and Na+ for Si4+; similar co-substitutions in synthetic cristobalite are known to modify the crystal structure, affecting the stability of the α and ß forms and the observed transition between them. Here, for the first time, the dynamics and energy changes associated with the α-ß phase transition in volcanic cristobalite are investigated using X-ray powder diffraction with simultaneous in situ heating and differential scanning calorimetry. At ambient temperature, volcanic cristobalite exists in the α form and has a larger cell volume than synthetic α-cristobalite; as a result, its diffraction pattern sits between ICDD α- and ß-cristobalite library patterns, which could cause ambiguity in phase identification. On heating from ambient temperature, volcanic cristobalite exhibits a lower degree of thermal expansion than synthetic cristobalite, and it also has a lower α-ß transition temperature (∼473 K) compared with synthetic cristobalite (upwards of 543 K); these observations are discussed in relation to the presence of Al3+ and Na+ defects. The transition shows a stable and reproducible hysteresis loop with α and ß phases coexisting through the transition, suggesting that discrete crystals in the sample have different transition temperatures.

Up-cycling waste glass to minimal water adsorption/absorption lightweight aggregate by rapid low temperature sintering: optimization by dual process-mixture response surface methodology.

Mixed color waste glass extracted from municipal solid waste is either not recycled, in which case it is an environmental and financial liability, or it is used in relatively low value applications such as normal weight aggregate. Here, we report on converting it into a novel glass-ceramic lightweight aggregate (LWA), potentially suitable for high added value applications in structural concrete (upcycling). The artificial LWA particles were formed by rapidly sintering (<10 min) waste glass powder with clay mixes using sodium silicate as binder and borate salt as flux. Composition and processing were optimized using response surface methodology (RSM) modeling, and specifically (i) a combined process-mixture dual RSM, and (ii) multiobjective optimization functions. The optimization considered raw materials and energy costs. Mineralogical and physical transformations occur during sintering and a cellular vesicular glass-ceramic composite microstructure is formed, with strong correlations existing between bloating/shrinkage during sintering, density and water adsorption/absorption. The diametrical expansion could be effectively modeled via the RSM and controlled to meet a wide range of specifications; here we optimized for LWA structural concrete. The optimally designed LWA is sintered in comparatively low temperatures (825-835 °C), thus potentially saving costs and lowering emissions; it had exceptionally low water adsorption/absorption (6.1-7.2% w/wd; optimization target: 1.5-7.5% w/wd); while remaining substantially lightweight (density: 1.24-1.28 g.cm(-3); target: 0.9-1.3 g.cm(-3)). This is a considerable advancement for designing effective environmentally friendly lightweight concrete constructions, and boosting resource efficiency of waste glass flows.