On the origin and processes controlling the elemental and isotopic composition of carbonates in hypersaline Andean lakes

H.J. and J.W.B. Rae acknowledge funding from the European Research Council under the European Union’s Horizon 2020 research and innovation program (grant agreement 805246).The Altiplano-Puna Plateau of the Central Andes hosts numerous lakes, playa-lakes, and salars with a great diversity and abundance of carbonates forming under extreme climatic, hydrologic, and environmental conditions. To unravel the underlying processes controlling the formation of carbonates and their geochemical signatures in hypersaline systems, we investigated coupled brine-carbonate samples in a high-altitude Andean lake using a wide suite of petrographic (SEM, XRD) and geochemical tools (δ2H, δ18O, δ13C, δ11B, major and minor ion composition, aqueous modelling). Our findings show that the inflow of hydrothermal springs in combination with strong CO2 degassing and evaporation plays an important role in creating a spatial diversity of hydro-chemical sub-environments allowing different types of microbialites (microbial mounds and mats), travertines, and fine-grained calcite minerals to form. Carbonate precipitation occurs in hot springs triggered by a shift in carbonate equilibrium by hydrothermal CO2 degassing and microbially-driven elevation of local pH at crystallisation. In lakes, carbonate precipitation is induced by evaporative supersaturation, with contributions from CO2 degassing and microbiological processes. Lake carbonates largely record the evaporitic enrichment (hence salinity) of the parent water which can be traced by Na, Li, B, and δ18O, although other factors (such as e.g., high precipitation rates, mixing with thermal waters, groundwater, or precipitation) also affect their signatures. This study is of significance to those dealing with the fractionation of oxygen, carbon, and boron isotopes and partitioning of elements in natural brine-carbonate environments. Furthermore, these findings contribute to the advancement in proxy development for these depositional environments.Peer reviewe

Heavy metal contents [lead and cadmium] in sets of courses served in military university dinning hall in the Czech Republic

The evaluation of the chosen sets of courses has been done in this research work. Chemical analysis of sets of courses involved the determination of the content of toxic elements such as lead and cadmium by polarographic analyzer. The determined quantity of lead as well as cadmium did not exceed acceptable limits.W niniejszej pracy oceniano wybrane zestawy dań, serwowanych w stołówce uczelni wojskowej w Republice Czeskiej. Analiza chemiczna obejmowała oznaczenie zawartości metali toksycznych - ołowiu i kadmu przy użyciu analizatora polarograficznego. Oznaczone ilości ołowiu i kadmu nie przekraczały dopuszczalnych wartości

Permian–Triassic mass extinction pulses driven by major marine carbon cycle perturbations

The Permian/Triassic boundary approximately 251.9 million years ago marked the most severe environmental crisis identified in the geological record, which dictated the onwards course for the evolution of life. Magmatism from Siberian Traps is thought to have played an important role, but the causational trigger and its feedbacks are yet to be fully understood. Here we present a new boron-isotope-derived seawater pH record from fossil brachiopod shells deposited on the Tethys shelf that demonstrates a substantial decline in seawater pH coeval with the onset of the mass extinction in the latest Permian. Combined with carbon isotope data, our results are integrated in a geochemical model that resolves the carbon cycle dynamics as well as the ocean redox conditions and nitrogen isotope turnover. We find that the initial ocean acidification was intimately linked to a large pulse of carbon degassing from the Siberian sill intrusions. We unravel the consequences of the greenhouse effect on the marine environment, and show how elevated sea surface temperatures, export production and nutrient input driven by increased rates of chemical weathering gave rise to widespread deoxygenation and sporadic sulfide poisoning of the oceans in the earliest Triassic. Our findings enable us to assemble a consistent biogeochemical reconstruction of the mechanisms that resulted in the largest Phanerozoic mass extinctio

Assessment of total polar materials in Frying fats from Czech restaurants

Deep-frying is commonly used as convenient technique for the preparation of foods. The frying oils and fats are absorbed by fried food and become a part of diet. The content of total polar materials was determined in frying oils and fats in 46 restaurants from South Moravia and the Olomouc regions. Twenty-eight samples were found with total polar materials with limit of rejection over 24%. The highest total polar materials values were observed in cooking fat; the lowest one was in vegetable shortening oil. This conclusion corresponds with frying temperatures, which were highest in cooking fat

Boron isotopes in brachiopods during the end-Permian mass extinction: constraints on pH evolution and seawater chemistry

The global biogeochemical cycling of carbon is fundamental for life on Earth with the ocean playing a key role as the largest and dynamically evolving CO2 reservoir. The boron isotope composition (commonly expressed in δ 11B) of marine calcium carbonate is considered to be one of the most reliable paleo-pH proxies, potentially enabling us to reconstruct past ocean pH changes and understand carbon cycle perturbations along Earth’s geological record (e.g. Foster et al., 2008; Clarkson et al., 2015). Brachiopods present an advantageous and largely underutilised archive for Phanerozoic carbon cycle reconstructions considering their high abundance in the geological record and its origin dating back to the early Cambrian. Moreover, their shell made of low-magnesium calcite makes these marine calcifiers more resistant to post-depositional diagenetic alteration of primary chemical signals. We have investigated the δ 11B using MC-ICP-MS (Neptune Plus) and B/Ca and other elemental ratios (Mg/Ca, Sr/Ca, Al/Ca, Li/Ca, Ba/Ca, Na/Ca and Fe/Ca) using ICP-MS-Quadrupole (Agilent 7500cx) from the same specimens in pristine brachiopod shells from two sections from northern Italy during the Late Permian. These sections cover the δ 13C excursion in excess of ∼4 h (Brand et al., 2012) and are associated with major climate and environmental perturbations that lead to the mass extinction event at the Permian-Triassic boundary. Particular emphasis will be placed on the implications of our new paleo-pH estimates on the seawater chemistry during the Late Permian

Carbon cycle perturbations and ocean acidification at the onset of the end-Permian mass extinction

The Permian-Triassic boundary-interval (PTB) witnessed the most severe environmental crisis in Earth history, which dictated the course for evolution of life until today. Current lines of evidence on causation point towards massive flood-basalt volcanism from Siberian traps, involving a combination of global warming by ˜6◦C, substantial input of relatively light carbon to the atmosphere, sporadic to widespread anoxia or euxinia, and ocean acidification, however the trigger mechanism is yet to be fully understood. In order to reconstruct potential changes in seawater chemistry during this time interval, we examined the boron isotope composition (δ11B) of pristine brachiopod shells. Although to-date hardly applied in Paleozoic settings, the δ11B of marine biogenic carbonates is considered to be one of the most reliable paleo-pH proxy. Brachiopods present an advantageous and largely underutilised archive for Phanerozoic reconstructions considering their high abundance in the geological record and its origin dating back to the early Cambrian. Moreover, their low-magnesium calcite shell renders them more resilient to post-depositional diagenetic alteration of primary chemical signals. Using carefully chosen pristine specimens (class Rhynchonellata and Strophomenata), selected δ11B to pH relationships, and bulk seawater δ11B scenarios we present a high-resolution seawater pH record for the Tethys Ocean. This interval covers the negative carbon isotope excursion in excess of 4 and is associated with major climate and environmental changes that led to the mass extinction event. Our results show a significant decline in δ11B succeeding the δ13C excursion, suggesting a substantial drop in seawater pH at the onset of the extinction event in the Late Permian related to carbon cycle perturbations. Combining our pH record with paired δ13C data and a quantitative modelling approach, we delineate the unfolding carbon cycle dynamic and budget that may have been responsible for initiating the catastrophic extinction event

Permian-Triassic mass extinction – a carbon-driven climatic and biogeochemical collapse

The Permian-Triassic mass extinction (approximately 251.9 million years ago) is the most severe environmental and biotic crisis identified in the geological record that marked the turning point for evolution of life on Earth. To date, however, its exact causes and consequences still remain highly controversial. Magmatism from the large igneous province (LIP) Siberian Traps was contemporaneous with the extinction and is thought to have played an important role, however, how a long-lived LIP could have led to such a sudden and rapid catastrophe of the observed magnitude has been challenging to reconcile. Combining new boron isotope-derived seawater pH estimates, global carbon isotope records and innovative geochemical modelling, we present a comprehensive biogeochemical reconstruction which illuminates the underlying mechanisms that resulted in the largest Phanerozoic mass extinction. We show that a LIP intrusion into organic-rich sediments led to an unprecedented CO2 release to the atmosphere, setting off a chain of profound climatic and chemical changes that ultimately made a large part of the oceans inhospitable to life [1]. [1] Jurikova H., et al. (2020), Nature Geoscience 13, 745-750, https://doi.org/10.1038/s41561-020-00646-4

Assessing ocean acidification and carbon cycle perturbations during the end-Permian extinction using boron isotopes

The Permian-Triassic mass extinction represents the most severe environmental crisis in Earth’s history, which dictated the course for evolution of life until today. Volcanism from Siberian traps played a significant role involving a substantial input of relatively light carbon into the atmosphere leading to a combination of global warming by ~6°C, sporadic anoxia or euxinia, and ocean acidification. However, its detailed manifestation and environmental impact is yet to be fully understood. This lack of knowledge also extends to a better quantification of emitted and sequestered carbon budgets (cf. Gutjahr et al., 2017). In order to reconstruct potential changes in seawater chemistry during this time interval, we examined the boron isotope composition (δ11B) of brachiopod shells. Although rarely applied to Paleozoic settings such as the Permian-Triassic (Clarkson et al., 2015), the δ11B of marine calcium carbonate is considered one of the most reliable paleo-pH proxies (e.g., Foster, 2008; Hönisch et al., 2012). The principle of the δ11B proxy is based on the speciation of boron in seawater, where it is present as boric acid [B(OH)3 −] and borate ion [B(OH)4 −], and their relative proportion is pH dependant. Furthermore, because an isotopic fractionation exists between the two species, and principally borate ion is incorporated into the crystal lattice, the δ11B composition of biogenic calcium carbonate can be used to reconstruct ancient seawater pH. Brachiopods present a rich, and largely underutilised archive for Phanerozoic reconstructions considering their high abundance in the geological record that can be traced back to the earlymakes these marine calcifiers more resilient to post-depositional diagenetic alterations of primary chemical signals. We performed δ11B analyses (together with B/Ca and other major and trace element−to−Ca ratios as additional controls on preservation and environmental conditions) on carefully chosen pristine specimens (class Rhynchonellata and Strophomenata) from Val Brutta, Sass de Putia and Tesero sections in northern Italy. These sections cover the negative δ13C excursion in excess of 4‰ (Brand et al., 2012) and are associated with major climate and environmental perturbations that led to the mass extinction event. Using selected δ11B to pH relationships and bulk seawater δ11B scenarios we reconstructed a high-resolution seawater pH record for the Paleo-Tethys Ocean. Our δ11B results show a significant decline in δ11B succeeding the δ13C excursion, suggesting a substantial drop in seawater pH at the onset of the extinction event in the Late Permian related to carbon cycle perturbations. To corroborate the extent of ocean acidification, we additionally measured several brachiopod specimens from the Shangsi section, South China (Garbelli et al., 2017). This confirms our findings from Italy, and implies that ocean acidification may have been a widespread phenomenon in the Paleo-Tethys, adversely impacting the marine life. Combining our pH record paired with δ13C data with a quantitative modelling approach we aim to delineate the unfolding carbon cycle dynamics and budget involved that may have been responsible for initiating the catastrophic extinction.Cambrian. Moreover, their shell made of low-magnesium calcit