High Atmospheric Levels Research Articles

Surface water oxygenation and low bioproductivity during deposition of iron formation of the Jacadigo Group (Brazil): Insights from combined cadmium – Chromium isotopes

The Banda Alta Formation (Urucum district, Mato Grosso do Sul, Brazil) comprises ∼600 Ma Fe and Mn deposits, which are among the world's youngest and largest Neoproterozoic sedimentary Fe and Mn formations (IF; MnF). These have been deposited in a redox-stratified, marine sub-basin (Jacadigo Basin), which was strongly influenced by glacial advance/retraction cycles with temporary influx of continental freshwater and upwelling of metal-enriched deep anoxic seawater. Cr and Cd isotopes measured on meticulously separated hematite mesobands from drill core samples are relatively homogenous throughout the ca. 325 m thick sequence sampled in the Banda Alta Fm., with average authigenic δ53Cr values of +0.93 ± 0.24 ‰ (2σ; n = 23) and δ114Cd values of −0.14 ± 0.14 ‰ (2σ; n = 15). The significant enrichment of Cr, in parallel with the strong enrichments of other redox sensitive elements (U, Mo), attests for effective and efficient reduction removal processes in the surface waters during cycles where upwelling Fe2+-rich waters reached the oxygenated surface layer exposed to the atmosphere during episodic glacier retreat stages. Assuming a similar quantitative and efficient removal pathway of dissolved Cd by iron oxyhydroxides, the so-inferred average δ114Cd signature of −0.14 ± 0.14 ‰ in the Jacadigo Basin surface water is significantly lower than signatures of modern ocean surface waters with a range of δ114Cd of ca. ∼0.4 to ∼1 ‰ and even lower than the signature of modern ocean deep waters with δ114Cd of ∼0.3 ‰. It possibly attests to reduced primary production levels and lower nutrient utilization rates during deposition of the Late Neoproterozoic Jacadigo Group, compared to today. This despite the inferred oxidized surface water layer that must have prevailed during this time, as implied by the strongly positively fractionated Cr isotope signatures and pronouncedly negative Ce-anomalies recorded in the seawater-like, shale-normalized Rare Earth Element and Yttrium (REY) patterns exhibited by the hematite mesobands. Data presented herein speak for: (1) a stable, isotopically heavy Cr input to the Jacadigo Basin at the time of deposition, implying high atmospheric O2 levels in the Late Neoproterozoic (2) likely quantitative, reductive incorporation / adsorption processes of dissolved Cr and Cd, respectively, into/onto precipitating iron oxyhydroxides, and (3) the prevalence of low nutrient concentrations and utilization rates in the Jacadigo Basin during glacier retreat cycles. Banded iron formations are considered suitable archives for reconstructing redox and bioproductivity levels in past marine depositional basin, including those prevalent in Neoproterozoic glacial conditions, via employing the CrCd isotope double tracer to iron-rich mesobands.

Electrochemical reconstruction of a 1D Cu(PyDC)(H2O) MOF into in situ formed Cu-Cu2O heterostructures on carbon cloth as an efficient electrocatalyst for CO2 conversion.

Electrochemical carbon dioxide (CO2) conversion has enormous potential for reducing high atmospheric CO2 levels and producing valuable products simultaneously; however the development of inexpensive catalysts remains a great challenge. In this work, we successfully synthesised a 1D Cu-based metal-organic framework [Cu(PyDC)(H2O)], which crystallizes in an orthorhombic system with the Pccn space group, by the hydrothermal method. Among the different catalysts utilized, the heterostructures of cathodized Cu-Cu2O@CC demonstrate increased efficiency in producing CH3OH and C2H4, achieving maximum FE values of 37.4% and 40.53%, respectively. Also, the product formation rates of CH3OH and C2H4 reach up to 667 and 1921 μmol h-1 cm-2. On the other side, Cu-Cu2O/NC-700 carbon composites simultaneously produced C1-C3 products with a total FE of 23.27%. Furthermore, a comprehensive study involving detailed DFT simulations is used to calculate the energetic stability and catalytic activity towards the CO2 reduction of Cu(111), Cu2O(111), and Cu@Cu2O(111) surfaces. During the early phase of electrochemical treatment, Cu(II) carboxylate nodes (Cu-O) in the Cu(PyDC)(H2O) MOF were reduced to Cu and Cu2O, with a possible synergistic enhancement from the PyDC ligands. Thus, the improved activity and product enhancement are closely associated with the cathodized reconstruction of Cu-Cu2O@CC heterostructures on carbon cloth. Hence, this study provides efficient derivatives of Cu-based MOFs for notable electrocatalytic activity in CO2 reduction and gives valuable insights towards the advancement of practical CO2 conversion technology.

Fire activities and their impacts on local ecosystems in the southern Ordos Basin during the Middle Jurassic: Evidence from pyrogenic PAHs and petrography of inertinite-rich coal

The high frequency of fires during the formation of some mire systems in the Jurassic is thought to have influenced how terrestrial ecosystems evolved. Ancient mires, now present as coal seams, contain high-resolution paleoenvironmental and paleoclimatic records. Thus, the analysis of coal beds provides valuable, insightful, and practical knowledge on the changes in paleoclimate and, in this case, fire prevalence. Using petrographic, carbon isotopic, mercury content, and polycyclic aromatic hydrocarbon (PAH) determinations, the Middle Jurassic No. 4 coal from the Binchang region in the Ordos Basin was examined in order to understand the nature of fire during the formation of the mires. The results show that the No. 4 coal exhibits a high content of inertinite (average content 70%). Notably, the correlation coefficient (r = 0.79) between the concentration of PAHs (with >3 rings) and the proportion of inertinite indicates that the high content of inertinite was predominantly the result of fire. The presence of natural char and coke in the coals further indicates the frequent incidence of fires during the Middle Jurassic in the southern Ordos Basin. High frequency of fires can be attributed to the availability of fuel (i.e., the buildup of organic material), high atmospheric oxygen levels, and intermittent dry climatic conditions. The random reflectance of inertinite (specifically, fusinite and semifusinite) in the No. 4 coal bed ranges from 1.25% to 2.45%, which, with the presence of pyrogenic PAHs, suggests that their formation may have been predominantly affected by low- and moderate-temperature fires. The high frequency of fires is thought to have significant impacts on terrestrial and hydrological ecosystems. These effects may have included the circulation of atmospheric mercury, as well as the possible occurrence of anoxic events in the lakes.

PEMETAAN KOROSIFITAS ATMOSFER MENGGUNAKAN LOGAM BAJA KARBON RENDAH DAN KARBON TINGGI PADA WILAYAH KOTA SURABAYA

Corrosion of metals is inevitable. One of the factors that affect corrosion is environmental conditions that contain pollutants like SO2, NO2, and Cl- which are found in many industrial and seaside areas. Surabaya is an area that has 2 types of conditions. In addition, Surabaya is the capital of the province where infrastructure development is running rapidly. Thus, this study maps the level of atmospheric corrosion in five areas in Surabaya by collecting corrosion rate data for 4 months with weight loss method using AISI 1020 Steel and SK5 Steel as test metals. XRD and SEM-EDX tests were conducted to compare the corrosion results. The average corrosion rate of low carbon steel was 0,6561 mpy and high carbon steel was 1,2523 mpy. The results concluded that the high level of atmospheric corrosivity of low carbon steel is in Sukomanunggal, Bulak, Rungkut, Pakal, Krembangan, and Bubutan sub-districts. The medium level is in Tegalsari, Gubeng, Tenggilis Mejoyo, Karang Pilang, Jambangan, Sawahan, and Dukuh Pakis sub-districts. The low level is in Lakarsantri, Mulyorejo, Simokerto, Sambikerep, Genteng, and Wonokromo sub-districts. Meanwhile, high atmospheric corrosivity levels for high carbon steel are in Krembangan, Karang Pilang, Bulak, Tenggilis Mejoyo, Pakal, and Jambangan sub-districts. The medium level is in Rungkut, Sawahan, Bubutan, Wonokromo, Tegalsari, Sukomanunggal, and Lakarsantri sub-districts. The level is in Dukuh Pakis, Genteng, Gubeng, Simokerto, Sambikerep, and Mulyorejo sub-districts. This mapping is based on the level of corrosion in each sub-district which is influenced by the presence of industry and its geographical location.

Re-Os, Sr-Nd isotopic and PGE elemental constraints for the formation of mid-Proterozoic ironstones in North China Craton: Implications for the atmospheric oxygen level

The origin (hydrothermal vs. continental Fe source) and environmental implications in particular for the atmospheric oxygen level of mid-Proterozoic ironstones have been widely studied, but remain highly debated. Here, we present Re-Os, Sr-Nd isotopic and PGE elemental data for ironstones from the ∼1.7 Ga Yunmengshan (YMS) Formation in south margin of the North China Craton to address the controversy. The initial 87Sr/86Sr ratios of the YMS ironstones are ∼0.7063, which are roughly comparable with seawater values around that period, suggesting a seawater signal with minor/minimal direct contributions from submarine hydrothermal fluids. The Nd isotopic compositions (εNd(t): −6.6 to −6.0) indicate a dominantly continental crustal signal for the formation of the ironstones. The PGE patterns of the YMS ironstones are distinctly similar to those of hydrogenous Fe-Mn crusts/nodules in modern ocean, also suggesting deposition from normal seawater conditions. Importantly, the YMS ironstones give initial 187Os/188Os ratios of ∼0.6 at ∼1.7 Ga, providing critical constraints for contemporaneous seawater values. This seawater 187Os/188Os value of ∼0.6 strongly suggests a result of oxidative weathering and transportation of Os in continental crust into the ocean, implying a relatively high atmospheric oxygen level at ∼1.7 Ga.

Strong positive fractionation of chromium isotopes in iron formation of the Jacadigo Group (Brazil) – A link to enhanced atmospheric oxygenation during the Late Neoproterozoic

Cr isotopes recorded in iron formations (IF) are considered to have the potential to reflect the isotope signatures in respective ambient surface seawater. The ∼600 Ma Fe and Mn deposits pertaining to the Banda Alta Formation (Urucum district, Mato Grosso do Sul, Brazil), comprise the world’s youngest and largest Neoproterozoic sedimentary Fe and Mn formations (MnF). Shale normalized Rare Earth Element and Yttrium (REY) patterns of drillcore samples show flat, positively sloped patterns with absent Europium anomalies and near- to supra-chondritic Yttrium-Holmium ratios with negative Cerium anomalies, which imply intermittent mixing of freshwater with seawater. Redox sensitive element enrichment factors (MoEF, UEF, CrEF) show positive correlation, indicating varying redox conditions across the Jacadigo Basin, with ephemeral euxinic conditions. The Cr isotope signatures across the Urucum IF (δ53Crauth at: Morraria Grande + 0.93 ± 0.34 ‰, 2σ, n = 28; Morro do Rabichão + 0.5 ± 0.4 ‰, 2σ, n = 3; and Morro do Urucum ca. + 0.64 ‰, n = 1) are statistically indistinguishable from previously published surface outcrop samples at Morro do Urucum. Our new data support: (1) a stable supply of oxidized Cr potentially from continental sources at the time of deposition, implying high atmospheric O2 levels in the Late Neoproterozoic; (2) insignificant alteration of the authigenic Cr isotope signals by tropical weathering despite surface iron up-concentration and leaching of carbonates, and (3) lack of isotope effects that would be associated with non-quantitative reduction processes and accompanying particulate transport to the chemical sediments in the Jacadigo Basin. The combined information from (isotope)geochemical data presented herein speak for a deposition of the Urucum IFs in restricted, periodically ice-covered and stratified sub-basins with partial connection to the open ocean, and for the presence of a sufficiently oxidative atmosphere which promoted a continuous supply of the surface waters with isotopically heavy Cr from the weathering landmasses at this time.

The origin of cap carbonate after the Ediacaran glaciations

Cap carbonate is the most unique component of a Snowball Earth glaciation, i.e., two Cryogenian global glaciations. In the canonical model, cap carbonate precipitation requires a deglacial extremely high atmospheric pCO2 level, which is unique for a Snowball Earth glaciation but did not occur in other non-Snowball Earth glaciations. However, some Ediacaran glacial successions also have a carbonate unit directly overlying the glacial deposits, although the Ediacaran glaciation is widely accepted to be a non-Snowball Earth ice age. Therefore, occurrence of Ediacaran glacial cap carbonate is counterintuitive, challenging the traditional model of cap carbonate precipitation. Here, we investigate two Ediacaran glacial cap carbonates, i.e. the Zhoujieshan cap carbonate above the Hongtiegou glacial deposits in the Chaidam Block, and the Hankalchough cap carbonate overlying the Hankalchough glacial deposits in the Tarim Block. The Zhoujieshan cap carbonate shows a transitional contact with the underlying glacial deposits, and has a nearly invariant carbonate carbon isotope value (δ13Ccarb) of ∼ + 1‰. The Hankalchough cap carbonate from the Luobupo section has a persistent δ13Ccarb value of ∼ − 5‰, but display a ∼ 15‰ spatial isotopic gradient in the Quruqtagh area. Combining with other occurrences, the Ediacaran glacial cap carbonate differs from the Snowball Earth cap carbonate in paleogeographic distributions, sedimentary structures, and mineralogical and geochemical compositions. We noticed that the Ediacaran glacial cap carbonates were restricted at ∼30–50° N/S, which may reflect a rapid transition from glaciation to carbonate deposition in subtropics. Thus, we speculate that the Ediacaran glaciation might have extended to latitude low enough, while the subsequent deglaciation and global warming may associate with an expansion of carbonate precipitation toward higher latitudes. Thus, the Ediacaran glacial cap carbonate precipitation occurred when carbonate precipitation and glaciation spatially overlapped in subtropics. Alternatively, considering paleomagnetic evidence for a ∼ 90° reorientation of all continents due to the Ediacaran true polar wander (TPW) event, some Ediacaran glacial cap carbonates could also be driven by glaciated continents moving into lower latitudes, where glacier melt and carbonate precipitated. Either way, a typical Snowball Earth glaciation may lead to global cap carbonate depositions, while most of Phanerozoic glaciations are characterized by glacial deposits in mid- to high-latitude and carbonate precipitation in tropics, i.e., showing no spatial overlapping of glaciation and carbonate precipitation. Thus, the enigmatic cap carbonate precipitation after the Ediacaran glaciations imply a unique climatic condition that differs from either a Snowball Earth glaciation or a Phanerozoic ice age.

Status of atmospheric air pollution in Ukraine prior to the full-scale russian invasion. Part 1: ground-level content of pollutants

The paper is dedicated to examination of atmospheric air pollution in Ukraine that is aimed at establishing basic air quality conditions prior to the full-scale Russian invasion. Analyses cover five air pollutants (dust, sulfur dioxide (SO2), carbon monoxide (CO), nitrogen dioxide (NO2), and formaldehyde (CH2O)) across 126 monitoring stations in 39 cities. It was found that the most dangerous excess of air pollution levels in cities was associated with dust, NO2, and CO. At the same time, SO2 content usually did not reach dangerous levels. The highest frequency of exceeding the threshold one-time levels was common for the cities with well-developed industrial facilities. Dangerous air pollution was observed in 15–60% of cases, depending on a pollutant. Dust and NO2 concentrations of the most polluted cities were 10 times higher than their concentrations in smaller cities having no significant industrial emissions. The difference in average CO, SO2, and CH2O concentrations among monitoring stations constituted 3-5 times. We studied the patterns of pollutants' seasonal variability recorded at the monitoring stations. Normally, no significant seasonality except for CH2O and dust was observed. The interannual variability of pollutants, emissions, and their trends were analyzed for the period since 2008. We identified a certain discrepancy in trends between pollutants’ concentrations and emission data over the last years. Pollutant content often continued to grow concurrently with emission reductions. The impact of atmospheric phenomena and wind parameters was studied mainly in terms of its role in formation of high and low atmospheric pollution levels. The analysis indicated a crucial role of local conditions in the formation of an atmospheric pollution field next to monitoring stations. Varying atmospheric pollution values across different monitoring stations within a specific city can be different even under the influence of the same atmospheric phenomena. The wind impact also formed different patterns of atmospheric pollution within same city. 12% to 22% of all monitoring stations (depending on a pollutant) indicated a prevailing impact of a single emission source (or a combined impact of a group of sources). At the same time, air pollution at other monitoring stations was highly variable, with elevated pollution levels being transported from numerous directions. The analysis of the air pollution-affected condition presented in the paper could be used as a basis for comparing ground-level pollution and assessing the warfare consequences in Ukraine. The research emphasizes the importance of updating the information about ground-based monitoring stations.

Vertical extrapolation of Advanced Scatterometer (ASCAT) ocean surface winds using machine-learning techniques

Abstract. The increasing demand for wind energy offshore requires more hub-height-relevant wind information, while larger wind turbine sizes require measurements at greater heights. In situ measurements are harder to acquire at higher atmospheric levels; meanwhile the emergence of machine-learning applications has led to several studies demonstrating the improvement in accuracy for vertical wind extrapolation over conventional power-law and logarithmic-profile methods. Satellite wind retrievals supply multiple daily wind observations offshore, however only at 10 m height. The goal of this study is to develop and validate novel machine-learning methods using satellite wind observations and near-surface atmospheric measurements to extrapolate wind speeds to higher heights. A machine-learning model is trained on 12 years of collocated offshore wind measurements from a meteorological mast (FINO3) and space-borne wind observations from the Advanced Scatterometer (ASCAT). The model is extended vertically to predict the FINO3 vertical wind profile. Horizontally, it is validated against the NORwegian hindcast Archive (NORA3) mesoscale model reanalysis data. In both cases the model slightly over-predicts the wind speed with differences of 0.25 and 0.40 m s−1, respectively. An important feature in the model-training process is the air–sea temperature difference; thus satellite sea surface temperature observations were included in the horizontal extension of the model, resulting in 0.20 m s−1 differences with NORA3. A limiting factor when training machine-learning models with satellite observations is the small finite number of daily samples at discrete times; this can skew the training process to higher-/lower-wind-speed predictions depending on the average wind speed at the satellite observational times. Nonetheless, results shown in this proof-of-concept study demonstrate the limited applicability of using machine-learning techniques to extrapolate long-term satellite wind observations when enough samples are available.

The effects of atmospheric dust and solar radiation on the dayside ionosphere of Mars derived from 17 years of Mars Express radio science observations

This work combines 17 years of Mars Express radio science (MaRS) observations with proxies for insolation and local/global atmospheric dust to investigate the combined and individual effects on the dayside ionosphere of Mars from the top down to the ionospheric base.The increase in insolation from orbital apocenter to pericenter in combination with Mars‘ dust cycle causes an average rise of the whole photochemically dominated region of the dayside ionosphere, ranging from 13 km at the ionospheric base up to 22 km above the main peak during conditions without a global dust storm. The declining phase of the 2018 global dust storm was observed by MaRS on the southern hemisphere and close to pericenter. The observed lifting effect on the whole photochemically dominated region of the ionosphere from the increased insolation and the high local and global atmospheric dust levels exceeds that seen by MaRS from similar seasons during years without a global dust storm.The average ionospheric peak altitude at the subsolar point rises for increasing levels of local atmospheric dust until a maximum elevation is reached. This maximum depends on the available insolation at the top of the planetary atmosphere. Further increases of the local atmospheric dust levels do not lead to a further rise of the average ionospheric peak altitude in the investigated data set. This indicates a limit for the warming/expansion of the lower neutral atmosphere and the consecutive lifting of the ionosphere based on the available insolation and explains why regional dust storms can cause a similar lifting of the ionospheric main peak region as global dust storms.

The soil−air exchange of OCPs and PCBs in the Tibetan Plateau: Emphasis on episodic transport of unintentionally produced PCBs

Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in paired ambient and surface air fugacity samples were measured in the Tibetan Plateau (TP) from 2019 to 2022. The air concentrations of previously intentionally produced chemicals like dichlorodiphenyltrichloroethane (DDT) and hexachlorocyclohexane (HCH) declined. Their soil−air exchange direction ranged from equilibrium to volatilization, suggesting that the TP is acting as a secondary source of most OCPs and PCBs with the pollution alleviation. However, considerably high atmospheric levels of PCB-11, an indicator of unintentionally produced PCBs (UP-PCBs), were recorded in the southern TP. Strong episodic long-range atmospheric transport (LRAT) and deposition of PCB-11 events took place mostly in summer. Those events associated with winds from potential sources and less rainfall interception along the air mass transport routes accounted for a significant fraction of overall atmospheric deposition in the TP. Meanwhile, cryoturbation and plowing are suspected to be important factors contributing to the reemission of PCB-11 from surface soil. The high abundance of PCB-11 and strong deposition/evaporation events highlights potential environmental and health risks of UP-POPs in the TP.

Proxy‐Based Preformed Phosphate Estimates Point to Increased Biological Pump Efficiency as Primary Cause of Last Glacial Maximum CO2 Drawdown

AbstractUpwelling deep waters in the Southern Ocean release biologically sequestered carbon into the atmosphere, contributing to the relatively high atmospheric CO2 levels during interglacial climate periods. Paleoceanographic evidence suggests this “CO2 leak” was lessened during the last glacial maximum (LGM), potentially due to increased stratification, weaker and equatorward‐shifted winds, and/or enhanced biological carbon export. The collective influences of these mechanisms on the ocean's biological pump efficiency and amount of atmospheric CO2 can be quantified by determining preformed phosphate of deep waters. We quantify preformed PO4 (Ppre,AOU) and preformed () of LGM bottom waters using a compilation of published paleo‐temperature, nutrient and oxygen estimates from benthic foraminifera. Our results show that preformed phosphate of the Pacific and Indian deep oceans was reduced by about −0.53 ± 0.13 μM and suggest that much (64 ± 28 ppmv) of the Glacial‐Interglacial CO2 drawdown resulted from changes in the ocean's biological pump efficiency. Once carbonate compensation is accounted for, this can explain the entire CO2 drawdown (87 ± 40 ppmv). Preformed shows similar results. The reconstructed LGM Ppre,AOU and oxygen are qualitatively consistent with the changes produced by a suite of numerical sensitivity experiments that roughly simulate three proposed mechanisms for an increase in LGM biological pump efficiency: an increase in biological activity, a decrease in wind‐driven upwelling, and an increase in stratification in the Southern Ocean.

Paleozoic Extinctions in Cosmoclimatological Context: ‘Non-Bolide’ Extraterrestrial Causes for Global Chilling

The Paleozoic Era experienced 4 major mass extinctions; i.e., end-Ordovician, Late Devonian, end-Guadalupian, and end-Permian episodes. As a cause of significant biodiversity decline, non-biological environmental change on global scale was inevitable; nonetheless, popular claims of bolide impact and/or large igneous province (LIP) with too many ad-hoc assumptions have not yet been accepted as common/universal explanations for the Paleozoic extinctions. Recent research on extinction causes evolved through two stages; i.e., the heyday of the bolide impact scenario in the 1980s, and the overtaking by a LIP-mantle plume scenario in the 1990–2000s. Lately, we may sense a return trend to extraterrestrial causes since the late 2000s, which is not a simple revival of the old bolide-impact model but a new proposal for a cosmoclimatological scenario relevant to extra-solar processes; i.e., supernovae explosions and relevant migration of dark clouds over the Solar System. This short article reviews the current status of extinction-related research, which emphasizes two key issues; i.e., the categorization of extinction causes and new perspectives on non-bolide extraterrestrial causes. The categorizing of extinction causes at four distinct levels is effective in separating “global triggers” on the Earth's surface from more essential “ultimate cases” within the Earth and/or on outside of the planet. Causes of extinction can be grouped into four distinct categories in a hierarchy, from small to large scale: i.e., Category 1 – direct kill mechanism for each local biota, Category 2 – background change in global environment, Category 3 – major geological phenomenon on the planet's surface, and Category 4 – ultimate cause from the interior and exterior of the planet. Recent advances in He isotope analysis for extinction-related sedimentary records suggest extraterrestrial causes, not of bolide impact but of the encounter with a dark cloud (nebula). Emerging new perspectives of cosmoclimatology leads to an alternative extinction scenario; e.g. 1) increased flux of galactic cosmic radiation (GCR) with extensive cloud cover and 2) passage of a dark cloud (nebula) enriched with micro-dusts (IDPs) enveloping the Solar System. Both meteoric cloud coverage and IDP-screen can induce lowering/shutdown of solar irradiance, which may drive global cooling and sea-level drop associated with biodiversity decline. The past star-burst events detected in the Milky Way Galaxy apparently coincide in timing with the cooling episodes associated with major extinctions of the Paleozoic, i.e., at the end-Ordovician, Late Devonian, and Late Permian. Given such astronomical processes associated with global cooling in the past, much older global freezing episodes, i.e., Proterozoic snowball Earth events developed under high atmospheric CO2 levels, can be likewise explained. The study of mass extinctions on the Earth is entering a new stage under new astrobiological perspectives.

Quality control of total carbon dioxide (CO2) in serum or plasma using the Abbott Architect is affected by environmental pCO2 concentrations.

Introduction: Total CO2, or bicarbonate, is a parameter in clinical chemistry often applied to assess the metabolic status of a patient. This article discusses the observations and interventions during an episode of assay instability on an Abbott Architect routine chemistry analyser.Results: The Levey-Jennings plot of QC data showed a circadian pattern, having an overestimation of total CO2 during periods of high personnel attendance. A qualitative analysis revealed a correlation between atmospheric CO2 in the lab environment and the acquired total CO2 value in a quality control sample. Assessment of total CO2 is hence influenced by the equilibrium between atmospheric CO2, dissolved CO2 and bicarbonate. The effect is more pronounced on samples containing low concentrations of total CO2. The bias related to environmental CO2 is also noticeable on patient samples, patient means between periods with high and low atmospheric CO2 levels differed by 2mmol/L.Discussion: Passive ventilation of the laboratory environment is proven insufficient during weather conditions in which the lab is not exposed to wind. Consistent reduction of atmospheric CO2 could only be guaranteed with an active ventilation infrastructure. Systematic closure of analyser lids also reduced analyser variance.Conclusion: The lab environment is an important source of parameter variance. Both environmental and infrastructural aspects must be considered when assessing the potential cause of the instability.

Early or late? The role of genotype phenology in determining wheat response to drought under future high atmospheric CO2 levels.

The combination of a future rise in atmospheric carbon dioxide concentration ([CO2 ]) and drought will significantly impact wheat production and quality. Genotype phenology is likely to play an essential role in such an effect. Yet, its response to elevated [CO2 ] and drought has not been studied before. Here we conducted a temperature-controlled glasshouse [CO2 ] enrichment experiment in which two wheat cultivars with differing maturity timings and life cycle lengths were grown under ambient (aCO2 approximately 400 μmol mol-1 ) and elevated (eCO2 approximately 550 μmol mol-1 ) [CO2 ]. The two cultivars, bred under dry and warm Mediterranean conditions, were well-watered or exposed to drought at 40% pot holding capacity. We aimed to explore water × [CO2 ] × genotype interaction in terms of phenology, physiology, and agronomic trait response. Our results show that eCO2 had a significant effect on plants grown under drought. eCO2 boosted the booting stage of the late-maturing genotype (cv. Ruta), thereby prolonging its booting-to-anthesis period byapproximately 3 days (p < 0.05) while unaffecting the phenological timing of the early-maturing genotype (cv. Zahir). The prolonged period resulted in a much higher carbon assimilation rate, particularly during pre-anthesis (+87% for Ruta vs. +22% for Zahir under eCO2 ). Surprisingly, there was no eCO2 effect on transpiration rate and grain protein content in both cultivars and under both water conditions. The higher photosynthesis (and transpiration efficiency) of Ruta was not translated into higher aboveground biomass or grain yield, whereas both cultivars showed a similar increase of approximately 20% in these two traits at eCO2 under drought. Overall, Zahir, the cultivar that responded the least to eCO2, had a more efficient source-to-sink balance with a lower sink limitation than Ruta. The complex water × [CO2 ] × genotype interaction found in this study implies that future projections should account for multifactor interactive effects in modeling wheat response to future climate.

High atmospheric CO2 levels in the early Mesoproterozoic estimated from paired carbon isotopic records from carbonates from North China

It is hypothesized that the Mesoproterozoic was characterized by a prevailing warm climate and a high atmospheric pCO2 level. However, quantitative constraints on Mesoproterozoic atmospheric pCO2 are scarce. Here, we report high-resolution organic and inorganic carbon isotope records from sediment samples aged ∼1.6 Ga, collected from Hebei Province in North China. The δ13Corg values of these Mesoproterozoic samples vary from −28.4‰ to −34.3‰, and the δ13Ccarbonate values range from −2.1‰ to 0.4‰. The paired carbonate and organic carbon isotope records can be used as a proxy to quantify the atmospheric CO2 concentration during the Mesoproterozoic. According to the calibration between the photosynthetic isotopic effect and atmospheric CO2, atmospheric CO2 concentrations are estimated to be within the range of 910–18,800 ppmv, ∼2–50 times greater than the present atmospheric level. The results support the previous hypothesis which suggests that high levels of atmospheric CO2 prevailed in the Early Mesoproterozoic. High atmospheric pCO2 levels could have played an important role in compensating for the possible lower solar luminosity and maintaining the temperature of the Mesoproterozoic Earth's surface.

Sustained high atmospheric Hg level in Beijing during wet seasons suggests that anthropogenic pollution is continuing: Identification of potential sources

Gaseous elemental Hg (GEM), particulate bound Hg (PBM), and gaseous oxidized Hg (GOM) were monitored at an urban site in Beijing, China during wet seasons (July–November) of 2021. The mean (± standard deviation) GEM, PBM, and GOM concentrations were 3.45 ± 1.27 ng m−3, 48.2 ± 88.6 pg m−3, and 13.7 ± 55.0 pg m−3, respectively. GEM level was stable (generally 3.0–4.0 ng m−3) and the average concentration was about twice that of the background level in Beijing, while the occasionally very high PBM and GOM concentrations (>1000 pg m−3) suggest pollution events. Moreover, GEM, CO, and NO2 exhibit a conspicuous similar diurnal trend with lower values during daytime compared to nighttime under the combined influence of anthropogenic emissions and meteorological factors, and the significantly positive relationship between them indicates that they had similar or common sources. However, the diurnal pattern of reactive Hg (i.e., RM = PBM + GOM) was not pronounced. Both cluster and potential source contribution function analyses show that southern Beijing, Tianjin, as well as central and east Hebei provinces were the dominant source regions for elevated GEM at this monitoring site. The dominant reason for the elevated GEM level (generally >3.5 ng m−3) during pollution event is that majority of air masses originated from the southern polluted regions of this sampling site and traveled at low heights, while the long-range transport of upper clean air masses and continuous high traveling heights were attributed to the low GEM level (<2.0 ng m−3) during clean event. Positive matrix factorization results reveal that regional transport of coal fired air pollutants and local vehicle emissions were the dominant contributors to elevated GEM level, while RM mainly originated from local sources.

Gaseous Mercury Exchange from Water-Air Interface in Differently Impacted Freshwater Environments.

Gaseous exchanges of mercury (Hg) at the water–air interface in contaminated sites strongly influence its fate in the environment. In this study, diurnal gaseous Hg exchanges were seasonally evaluated by means of a floating flux chamber in two freshwater environments impacted by anthropogenic sources of Hg, specifically historical mining activity (Solkan Reservoir, Slovenia) and the chlor-alkali industry (Torviscosa dockyard, Italy), and in a pristine site, Cavazzo Lake (Italy). The highest fluxes (21.88 ± 11.55 ng m−2 h−1) were observed at Solkan, coupled with high dissolved gaseous mercury (DGM) and dissolved Hg (THgD) concentrations. Conversely, low vertical mixing and saltwater intrusion at Torviscosa limited Hg mobility through the water column, with higher Hg concentrations in the deep layer near the contaminated sediments. Consequently, both DGM and THgD in surface water were generally lower at Torviscosa than at Solkan, resulting in lower fluxes (19.01 ± 12.65 ng m−2 h−1). However, at this site, evasion may also be limited by high atmospheric Hg levels related to dispersion of emissions from the nearby chlor-alkali plant. Surprisingly, comparable fluxes (15.56 ± 12.78 ng m−2 h−1) and Hg levels in water were observed at Cavazzo, suggesting a previously unidentified Hg input (atmospheric depositions or local geology). Overall, at all sites the fluxes were higher in the summer and correlated to incident UV radiation and water temperature due to enhanced photo production and diffusivity of DGM, the concentrations of which roughly followed the same seasonal trend.

The spatial distribution of surface ocean primary productivity in the wake of Marinoan global glaciation

Termination of the Marinoan global glaciation (~650–635 Ma) was followed by the diversification of eukaryotes (e.g., early animals) and oxygenation of deep oceans in the early Ediacaran Period. Previous studies indicate the recovery of marine primary productivity immediately before the cap carbonate precipitation but after melting of the Marinoan global glaciation. Pyrite concretions from the topmost Nantuo Formation in the Yangtze Block, South China, decrease in abundance from shelf to basin facies, while their high positive sulfur (S) isotope values argue the development of oceanic euxinia, which require ample supply of organic matter, presumably reflecting the recovery of marine productivity. However, pyrite contents and pyrite S isotopes alone cannot uniquely constrain the extent and spatial distribution of surface ocean organic matter production. In this study, we conducted in situ analyses of pyrite iron (Fe) (δ56Fepy) and S isotopes (δ34Spy) of pyrite concretions collected from four sections of the Nantuo Formation, spanning from shelf to basin environments. Pyrite from different facies has distinct δ34Spy and δ56Fepy values. In general, δ34Spy values display an increasing trend from shelf to basin, whereas δ56Fepy values demonstrate an opposite trend with the lowest value in the basin sections. The opposite δ34Spy and δ56Fepy shelf-basin gradients strongly argue against the hydrothermal origin, yet verify the diagenetic precipitation of Nantuo pyrite in sediment porewater. Numerical models were developed to quantify the microbial sulfate reduction (MSR), microbial iron reduction (MIR) and pyrite precipitation processes. The modeling results provide an explanation for the shelf-basin decrease of δ56Fepy values, indicating that both the fraction of MIR (fMIR) and the fraction of Fe2+ consumed by pyrite precipitation (fpy) increase from shelf to basin sections. In addition, high δ34Spy values and pyrite contents in the basin sections also imply more intense MSR and higher supplies of H2S from sulfidic seawater. Both MSR and MIR were fueled by organic matter, thus suggesting that the surface ocean primary productivity displayed an unusual increasing trend toward the open ocean, which was different from the higher productivity in modern near-shore regions. We speculate that the reversed shelf-basin gradient of surface ocean primary productivity might be attributed to high P concentration in the post-glacial ocean. Terrestrial riverine P supply, on the contrary, might have diluted seawater P concentration in the near-shore regions. Therefore, our result indicates that the recovery of marine productivity in the aftermath of the Marinoan global glaciation may be not controlled by the availability of nutrients, instead, the immediate recovery of productivity might have been prohibited by, e.g., low seawater pH at a high atmospheric pCO2 level in the initial melting of the Marinoan global glaciation. The marine primary productivity did not recover until a substantive rise of seawater pH, during which deglacial intense continental weathering delivered abundant P into the ocean and accordingly elevated the seawater P concentration.

Clumped isotope evidence for Early Jurassic extreme polar warmth and high climate sensitivity

Abstract. Periods of high atmospheric CO2 levels during the Cretaceous–early Paleogene (∼ 140 to 34 Myr ago) were marked by very high polar temperatures and reduced latitudinal gradients relative to the Holocene. These features represent a challenge for most climate models, implying either higher-than-predicted climate sensitivity to atmospheric CO2 or systematic biases or misinterpretations in proxy data. Here, we present a reconstruction of marine temperatures at polar (&gt; 80∘) and middle (∼ 40∘) paleolatitudes during the Early Jurassic (∼ 180 Myr ago) based on the clumped isotope (Δ47) and oxygen isotope (δ18Oc) analyses of shallow buried pristine mollusc shells. Reconstructed calcification temperatures range from ∼ 8 to ∼ 18 ∘C in the Toarcian Arctic and from ∼ 24 to ∼ 28 ∘C in Pliensbachian mid-paleolatitudes. These polar temperatures were ∼ 10–20 ∘C higher than present along with reduced latitudinal gradients. Reconstructed seawater oxygen isotope values (δ18Ow) of −1.5 ‰ to 0.5 ‰ VSMOW and of −5 ‰ to −2.5 ‰ VSMOW at middle and polar paleolatitudes, respectively, point to a significant freshwater contribution in Arctic regions. These data highlight the risk of assuming the same δ18Osw value for δ18O-derived temperature from different oceanic regions. These findings provide critical new constraints for model simulations of Jurassic temperatures and δ18Osw values and suggest that high climate sensitivity has been a hallmark of greenhouse climates for at least 180 Myr.