High Atmospheric Levels Research Articles

Evolutionarily conserved bacterial effectors hijack abscisic acid signaling to induce an aqueous environment in the apoplast

High atmospheric humidity levels profoundly impact host-pathogen interactions in plants by enabling the establishment of an aqueous living space that benefits pathogens. The effectors HopM1 and AvrE1 of the bacterial pathogen Pseudomonas syringae have been shown to induce an aqueous apoplast under such conditions. However, the mechanisms by which this happens remain unknown. Here, we show that HopM1 and AvrE1 work redundantly to establish an aqueous living space by inducing a major reprogramming of the Arabidopsis thaliana transcriptome landscape. These effectors induce a strong abscisic acid (ABA) signature, which promotes stomatal closure, resulting in reduced leaf transpiration and water-soaking lesions. Furthermore, these effectors preferentially increase ABA accumulation in guard cells, which control stomatal aperture. Notably, a guard-cell-specific ABA transporter, ABCG40, is necessary for HopM1 induction of water-soaking lesions. This study provides molecular insights into a chain of events of stomatal manipulation that create an ideal microenvironment to facilitate infection.

Active biogeochemical cycles during the Marinoan global glaciation

Termination of the Marinoan global glaciation (650–635 million years ago, Ma) was immediately followed by the diversification of eukaryotes and possible occurrence of animals, suggesting the potential linkage between biological evolution and global glaciation. It is proposed that the post-glacial eukaryote evolution might have been triggered by environmental stress imposed by the extreme pan-glacial condition. However, how life survived through the global glaciation remains speculative. Neither is known about the habitability when the ocean was completely or mostly frozen. In this study, we explore the marine carbon and sulfur biogeochemical cycles during the Nantuo (Marinoan) glaciation (650–635 Ma) in South China. Both organic carbon (δ13Corg) and pyrite sulfur isotopes (δ34Spy) show significant stratigraphic variations, suggesting active biogeochemical cycles in the pan-glacial condition. By coupling both δ13Corg and δ34Spy data, we develop numerical models to constrain marine productivity and redox conditions during the Nantuo glaciation. The marine primary productivity showed a sharp decline in the onset of glaciation and recovered right before the cap carbonate precipitation. An episodic recovery of primary productivity was observed in the non-glacial interval between the two glacial episodes. In contrast, the marine productivity was still suppressed in initial deglaciation, during which the continental weathering was intense, presumably indicating high atmospheric CO2 level and low seawater pH value. The final recovery of marine primary productivity occurred in the topmost of Nantuo Formation, when the weathering intensity was already low. Therefore, the active biogeochemical cycle implies a sustained habitability, warranting the survivorship in the pan-glacial ocean, while the persistently low and delayed recovery of marine productivity might have imposed environmental stress for tens of million years, paving the way for the evolution of animals.

Influences of COVID-19 on Environment

Abstract: This study aims to show the positive and negative effects of COVID-19 on the environment and test how individual mobility is affected by the spread of local diseases and homeopathic regulations. During the COVID-19 epidemic. Since solitary confinement can affect mental health, this study aims to quantify the occurrence of sadness, nervousness, and sleep illnesses in world during incarceration. I associate educated air pollution levels with unusually high atmospheric precipitation levels in different parts of the world. Electricity demand has been significantly abridged because of the current COVID-19 epidemic. Administrations worldwide are being forced to cut business operations in comeback to reducing the hazard of coronavirus. This continuing condition because of COVID-19 has altered the way of life around the world as people live at home and work at home when possible. Therefore, there is a noteworthy rise in the claim for real estate while there is a considerable reduction in trade and manufacturing loads. This dire situation poses new challenges to the power sector's practical and economic services, which is why many resources around the world have embarked on a disaster risk management program to address these ongoing challenges/threats. Satellite data has shown declining air pollution levels in many areas. Of the earth. This review purposes to examine the global cOVID-19 conditions worldwide.

A methodical approach to assessing if an existing dwelling has ‘Adequate Ventilation’

Every year, especially during what has become colloquially referred to as ‘condensation season’, thousands of dwellings around the UK have their ventilation assessed. This Ventilation Assessment is sometimes referred to as a ‘Ventilation Survey’. The assessment is frequently in response to occupants’ concerns over living in homes suffering from condensation and mould growth. Ventilation assessments are carried out by a variety of ‘specialists’ including independent surveyors, ventilation equipment manufacturers/suppliers and contractors. Very often, following the assessment, the specialist will recommend that additional ventilation equipment be installed to contribute towards providing Adequate Ventilation in the dwelling. In many cases, the primary function of the additional ventilation measures proposed will be to control high internal atmospheric moisture levels that can be associated with condensation and mould, while neglecting indoor air pollutants commonly found in homes, which also have to be controlled if a healthy internal environment is to be provided for the occupants. It is the author’s view that there will often be an unintentional lack of appropriate methodology used in the Ventilation Assessment and the subsequent recommendations such specialists make may not therefore be appropriate for the dwelling. This is not surprising given that there is limited industry guidance on the subject in relation to existing dwellings and the fact that even the term ‘Adequate Ventilation’ can mean different things to different people. This paper discusses all of the aforementioned and proposes benchmarks against which Adequate Ventilation in existing dwellings can be measured, along with an overview of a methodology that could be used to assess the existing purpose-provided ventilation measures in a home to determine if they are adequate or not.

Evaluation of air pollution tolerance index and anticipated performance index of six plant species, in an urban tropical valley: Medellin, Colombia.

High atmospheric pollution levels in urban areas have become a global problem that threatens both human health and urban ecosystems. Trees that grow near areas with vehicular and industrial emissions can be highly affected, since they constitute the main barrier for emitted pollutants, with trees being either tolerant or sensitive to them. Different methodologies worldwide have been implemented to evaluate the tolerance and sensitivity of tree species to atmospheric pollutants. In this research, the air pollution tolerance index (APTI) and the anticipated performance index (API) are evaluated in order to determine both the degree of tolerance or sensitivity of trees to pollutants in the air and their performance in urban areas. To this end, six tree species found in four biomonitoring zones in the city of Medellín, Colombia, were selected: Mangifera indica, Tabebuia chrysantha-rosea, Erythrina fusca, Jacaranda mimosifolia, Fraxinus uhdei, and Spathodea campanulata. A total of 54 individual trees were evaluated by means of the APTI and API, and it was determined that the species with the highest tolerance (APTI≥16) and the best performance (81<API<90) was Mangifera indica, which highlights the importance of this species in urban areas with air quality problems. On the other hand, it was determined that the most sensitive species (APTI≤11) are Tabebuia chrysantha-rosea, Erythrina fusca, and Spathodea campanulata, while the species with poor performance (41<API<50) are Tabebuia chrysantha-rosea, Erythrina fusca, and Jacaranda mimosifolia. These values, therefore, can be used to classify which species can be planted as pollutant sinks and which as air quality bioindicators and thus highlight the importance of urban forests and trees for environmental management and planning in big cities with air quality problems.

Evidence for widespread wildfires and their environmental impact in the Late Cretaceous Canadian Arctic

Wildfires are important in modern ecology but the complex interplay between wildfires and vegetation or climate is less well understood in ancient environments, in particular those of the Arctic regions. This includes the impacts of paleo-wildfires on surrounding marine basins by affecting sedimentation rates and nutrient input via soil degeneration and intensification of continental run-off. The Late Cretaceous was an important time of global climate shift, with the rise of angiosperm vegetation marking a turning point in global flora, and globally abundant wildfires due to high atmospheric oxygen levels and elevated temperatures. This study investigates Late Cretaceous samples from the Canadian Arctic Islands to examine the evidence for widespread wildfires and how these wildfires may have influenced or been influenced by contemporaneous climate and vegetation shifts. Organic geochemical, and organic petrological data show evidence of enhanced wildfires beginning in the Turonian, including increases in semi-fusinite macerals and pyrogenic PAH (polycyclic aromatic hydrocarbon) indicators of natural combustion. This increasing wildfire influence corresponds with a rise in broad-leafed Arctic forests, as evidenced by angiosperm-derived terpenoid biomarkers, with both wildfire and angiosperm abundances peaking in the Early Campanian. Additionally, geochemical and petrographic data shows a shift in the type of organic matter deposited over time, correlating to the evidence of increased wildfire activity. This study proposes that the distance between wildfire region and marine depocenter is assessed via a new provenance method based on the degree of photo-oxic degradation of selected PAH isomers upon airborne transport. The increasing effects of wildfires on the Arctic ecosystem over the Turonian-Campanian were likely driven by relatively warm temperatures, elevated atmospheric oxygen, volcanism related to the High Arctic Large Igneous Province (HALIP), and abundant fuel availability. Widespread wildfires are proposed to have fostered the expansion of angiosperm vegetation into the Canadian Arctic in the Late Cretaceous by allowing them to outcompete gymnosperms in post-fire regrowth. Intensified erosion and continental run-off associated with the destruction of the vegetation cover by wildfires is thought to have acted as a driving force in the increasing terrigenous organic matter deposition in the Sverdrup Basin during the Late Cretaceous. Taken together, the results of this study suggest that increasing wildfires related to global climatic conditions in the Late Cretaceous contributed to the expansion of angiosperm flora in the Arctic, and had a substantial impact on the deposition of sediments in the surrounding Sverdrup Basin.

Ubiquitous atmospheric production of organic acids mediated by cloud droplets

Atmospheric acidity is increasingly determined by carbon dioxide and organic acids1–3. Among the latter, formic acid facilitates the nucleation of cloud droplets4 and contributes to the acidity of clouds and rainwater1,5. At present, chemistry–climate models greatly underestimate the atmospheric burden of formic acid, because key processes related to its sources and sinks remain poorly understood2,6–9. Here we present atmospheric chamber experiments that show that formaldehyde is efficiently converted to gaseous formic acid via a multiphase pathway that involves its hydrated form, methanediol. In warm cloud droplets, methanediol undergoes fast outgassing but slow dehydration. Using a chemistry–climate model, we estimate that the gas-phase oxidation of methanediol produces up to four times more formic acid than all other known chemical sources combined. Our findings reconcile model predictions and measurements of formic acid abundance. The additional formic acid burden increases atmospheric acidity by reducing the pH of clouds and rainwater by up to 0.3. The diol mechanism presented here probably applies to other aldehydes and may help to explain the high atmospheric levels of other organic acids that affect aerosol growth and cloud evolution.

Diel Transcriptional Oscillations of a Plastid Antiporter Reflect Increased Resilience of Thalassiosira pseudonana in Elevated CO2

Acidification of the ocean due to high atmospheric CO2 levels may increase the resilience of diatoms causing dramatic shifts in abiotic and biotic cycles with lasting implications on marine ecosystems. Here, we report a potential bioindicator of a shift in the resilience of a coastal and centric model diatom Thalassiosira pseudonana under elevated CO2. Specifically, we have discovered, through EGFP-tagging, a plastid membrane localized putative Na+(K+)/H+ antiporter that is significantly upregulated at &amp;gt;800 ppm CO2, with a potentially important role in maintaining pH homeostasis. Notably, transcript abundance of this antiporter gene was relatively low and constant over the diel cycle under contemporary CO2 conditions. In future acidified oceanic conditions, dramatic oscillation with &amp;gt;10-fold change between nighttime (high) and daytime (low) transcript abundances of the antiporter was associated with increased resilience of T. pseudonana. By analyzing metatranscriptomic data from the Tara Oceans project, we demonstrate that phylogenetically diverse diatoms express homologs of this antiporter across the globe. We propose that the differential between night- and daytime transcript levels of the antiporter could serve as a bioindicator of a shift in the resilience of diatoms in response to high CO2 conditions in marine environments.

Evaluating the effect of heat waves on early melting of snow covers of Karkheh catchment in Iran

The present study aims to evaluate the effect of heat waves on the early melting of snow cover in the Karkheh catchment of Iran. After collecting daily data on the maximum temperature of meteorological stations in the catchment during the statistical period (2000–2019), three indices of WSDI, Baldi, and ocular method were used to determine the threshold of days with heat wave. By extracting the hot waves and applying programming, the snow cover maps were drawn in the Google Earth Engine system and the area of ​​snow cover zones was calculated in the Model Builder. Finally, the atmospheric data were received from the NCEP/NCAR site and their generating patterns were examined after drawing in Grads software environment after determining the atmospheric synoptic patterns. The results indicated that the slope trend of hot waves is increasing at the catchment level. The average annual frequency of heat waves extracted for the snow cover growth period (November–May) was equal to 24 days of hot waves during the year. Regarding the ground pressure conditions and synoptic conditions of high atmospheric levels, two dominant synoptic patterns of heat waves were identified in the region as follows: (1) The Siberian high-pressure synoptic pattern at the ground level and the Saudi-African high-pressure ridge at high atmospheric levels. This synoptic pattern reduces snow cover area by an average of 40% in the Karkheh catchment and the highest frequency of the occurrence of this synoptic pattern is in February and March. (2) Pakistan-Africa low-pressure synoptic pattern at ground level and Saudi-African high-pressure ridge at high atmospheric levels, the frequency of the occurrence of which is higher in April and May months and reduces the snow cover area in the Karkheh catchment by an average of more than 55%.

Coal petrology of the Yimin Formation (Albian) in the Hailar Basin, NE China: Paleoenvironments and wildfires during peat formation

Coal seams preserve continuous and high-resolution records of paleoenvironments and wildfire events during peat accumulation. In order to elucidate wildfire characteristics and terrestrial climate changes during the time of peat accumulation, petrographic characteristics of coals in the Lower Cretaceous Yimin Formation (Albian) in the Jiuqiao Sag, Hailar Basin, NE China were studied. Coal petrology analysis shows that the studied coal seams are characterized by dominant huminite (average 80.0 vol.%, mmf-mineral matter free), secondary inertinite (average 19.9 vol.%, mmf), and a very low mineral content (average 0.8 vol.%). These results suggest that the coal developed under waterlogged conditions in raised, ombrotrophic mires. The occurrence of moderate inertinite values in the coals implies that wildfires were frequent during the Albian. Burning temperature, ranging from 273 to 379 °C inferred from inertinite reflectances, indicates that wildfires during the Albian were ground fires because of low plant heights. Vertical trends in inertinite and huminite compositional changes within the coal seams may reflect local-scale, cyclic fluctuations in wildfire occurrence during the development of the peat mires. The likely cause of these fluctuations was changes in temperature and rainfall. The presence of significant levels of inertinite in the coals and inferred high atmospheric oxygen levels suggest that the Albian was a highly fire-prone period in the Hailar Basin. The recurrent occurrences of palaeo-wildfires events in the studied succession in the Hailar Basin reinforce that fire was an important element affecting wetland biodiversity during the Albian, while diversification and spread of angiosperms was taking place globally. Increased surface runoff and erosion after the palaeo-wildfires in the Jiuqiao Sag during the Albian may have enhanced the flux and availability of nutrients and sediments washing into the fluvial, lacustrine, and marine systems, further contributing to the Albian dysoxic-anoxic events.

Impacts of the Madden‐Julian Oscillation on the intensity and spatial extent of heavy precipitation events in northern Northeast Brazil

AbstractThis paper investigates the spatiotemporal variability of Contiguous Extreme Precipitation Events (CEPE) related to Madden‐Julian Oscillation (MJO) activity during the pre‐wet season and wet season in northern Northeast Brazil for 30 years (1979–2010). Inherent differences in rainy season regimes are associated with northern Northeast Brazil precipitation systems; these are isolated during pre‐wet and wet season and analyse the intensity and the spatial area covered by the CEPE. A daily index of MJO activity and its life cycle were used to identify activity phases during heavy rainfall events. Composite analysis was performed for days with CEPE during the most frequent MJO phases in the pre‐wet and wet seasons. The analysis shows the influence of the MJO on the occurrence of CEPE in northern Northeast Brazil. In the pre‐wet season, the MJO phases 8‐1‐2 affect the occurrence of heavy rainfall events, modifying the atmospheric circulation and water vapour transport over northern South America. Indications of Rossby wave propagation over the South Pacific associated with MJO were found, suggesting tropic‐extratropic teleconnection during occurrences of CEPE in the pre‐wet season. In the wet season, CEPE events are more frequent during MJO phases 8‐2‐3. Conversely, no wave propagation over the South Pacific is observed in the wet season, changes in wind anomalies at high and low atmospheric levels only point to the influence of the MJO via tropical teleconnection. This study may help monitoring and forecasting of very heavy rainfall events in northern Northeast Brazil in pre‐wet season and wet season.

Background Concentration of Copper and Cadmium in Water from a High Industrialized and Urban Coastal System (Baixada Santista, Brazil)—Contribution to a Monitoring Program

The Baixada Santista coastal region is well known in the context of the high atmospheric, soil and aquatic pollution levels derived from port, industrial, domestic and urban activities existent there, mainly in function of the Cubatão industrial pole and port of Santos. The contamination by trace metals in this region is rarely measured in water column when compared with metal determinations in sediment studies. This study aims to evidence the levels of dissolved copper and total cadmium concentrations in estuarine and seawater waters using electrochemical analysis as a chronopotentiometric stripping polarography, which could improve the environmental monitoring program. The study was performed in the Bay of Santos reaching two estuarine channels (Santos and São Vicente Channels) in two tide periods in summer 2001. This region is influenced by terrestrial and anthropogenic inputs of trace metals to seawater. The results showed that dissolved copper and total cadmium in water presented the maxima concentrations of 45.4 nM and 2.6 nM respectively. They not reached the limits proposed by Brazilian Environmental Law (CONAMA), that indicate, as reference, a maximum of 123 nM and 350 nM for dissolved copper and total cadmium, respectively and, considering seawater coastal system (salinity > 30, class 2) and also brackish water (class 2). Although the values were under the maximum recommended for each metal, the concentrations were not negligible in relation to the other polluted areas in the world. The values distribution along the system showed a progressive increase in direction to the inner part of the system that naturally compromises the local biota whose is more exposed to the bioaccumulation processes, and this data corresponds to an important reference preterit value to the monitoring program. The trace metal bioaccumulation by mangrove vegetation and by the biota in the internal part of the estuarine channels increase the risk of the poorly population that living in the internal part of the estuary, used to the seafood consumption. The contribution of this study is important to guide the protective policies destined to recuperate the natural conditions of this system, mainly considering that in the decade 1980, there was a case of toxic contamination, causing hydrocephaly in newborns. It proves the existence of risks to the human health and to the balance of the ecosystem, even with the decrease of pollution after that, the environmental evaluation needs to know the background values to guide environmental protection.

Harsh or balmy weathering conditions onto the first continent surface?

The weathering conditions prevailing during Proterozoic times differ likely from Present-day ones mainly because of the climate conditions driven by high CO2 atmospheric levels. The question of weathering intensity onto one of the first continent surface, so-called “Columbia”, is here addressed using the combination of a thermochemical and climatic model. Based on the dissolution of a mix of silicates representative of the presumed fresh rocks and the precipitation of secondary phases, the plausible reaction pathways of weathering seem to indicate that approximately 10% of initial silicates minerals should be dissolved to explain the measured high Chemical Index of Alteration (CIA), classically measured in the rocks belonging to this geological period. In addition, global climatic simulations were performed to evaluate the respective contributions of pCO2, pluviometry, temperature and topographic parameters upon the weathering intensity. This finding could suggest the weathering intensity have been, at the very most, two orders of magnitude greater than tropical present-day one over the Paleoproterozoic era: the runoff seemed to be similar whereas the dissolution reaction extent was enhanced. These calculations are confronted with the geological record of weathering conditions, namely well-preserved sandstone deposits belonging to the 1.9 Ga Roraima Supergroup in the Guiana Shield, Brazil. The field data indicating very high Chemical Index of Alteration are in line with the model calculations.

Atmospheric mercury pollution caused by fluorescent lamp manufacturing and the associated human health risk in a large industrial and commercial city.

Although already eliminated in most industrial processes, mercury, as an essential ingredient in all energy-efficient lighting technologies, is still used in fluorescent lamp manufacturing. This study was conducted to investigate the atmospheric pollution caused by fluorescent lamp production and assess the associated public health risk in a large industrial and commercial city of south China, Zhongshan, which is a major production hub of lighting products. Concentrations of total gaseous mercury (TGM) in the atmosphere were measured over a total of 342 sites in the industrial, commercial, and residential areas. The average levels of TGM in the industrial, commercial, and residential areas prior to the landing of a typhoon were 12±11, 3.6±2.1, and 2.7±1.3ng⋅m-3, respectively. TGM concentrations in the industrial areas exhibited significant diurnal variation, with levels in the working hours being much higher than those in the non-working hours, which indicates that the high atmospheric mercury concentrations were contributed by local emissions, instead of regional transport. Most fluorescent lamp manufacturing activities in the city were shut down during a typhoon event, which resulted in a significant reduction in the average TGM level (down to 1.6±1.8ng⋅m-3) and rendered the difference in the average TGM levels in the industrial areas no longer significant between the working and non-working hours. Elevated TGM levels (up to 49ng⋅m-3) were found near clusters of small-scale fluorescent lamp workshops in both industrial and commercial areas, which is indicative of significant emissions of mercury vapor resulting from obsolete equipment and production technologies. No significant non-carcinogenic risk was found for the general residents in the sampling area over the study period, while the risk for the workers in the fluorescent lamp manufacturing facilities and workshops could be higher. These findings indicate that fluorescent lamp manufacturing in the developing countries is a major source of atmospheric mercury.

The effects of climate change on respiratory allergy and asthma induced by pollen and mold allergens.

The impact of climate change on the environment, biosphere, and biodiversity has become more evident in the recent years. Human activities have increased atmospheric concentrations of carbon dioxide (CO2 ) and other greenhouse gases. Change in climate and the correlated global warming affects the quantity, intensity, and frequency of precipitation type as well as the frequency of extreme events such as heat waves, droughts, thunderstorms, floods, and hurricanes. Respiratory health can be particularly affected by climate change, which contributes to the development of allergic respiratory diseases and asthma. Pollen and mold allergens are able to trigger the release of pro-inflammatory and immunomodulatory mediators that accelerate the onset the IgE-mediated sensitization and of allergy. Allergy to pollen and pollen season at its beginning, in duration and intensity are altered by climate change. Studies showed that plants exhibit enhanced photosynthesis and reproductive effects and produce more pollen as a response to high atmospheric levels of carbon dioxide (CO2 ). Mold proliferation is increased by floods and rainy storms are responsible for severe asthma. Pollen and mold allergy is generally used to evaluate the interrelation between air pollution and allergic respiratory diseases, such as rhinitis and asthma. Thunderstorms during pollen seasons can cause exacerbation of respiratory allergy and asthma in patients with hay fever. A similar phenomenon is observed for molds. Measures to reduce greenhouse gas emissions can have positive health benefits.

Atmospheric dimethyl sulfide and its significant influence on the sea-to-air flux calculation over the Southern Ocean

Our understanding about the atmospheric dimethyl sulfide (DMS) and its influence to sea-to-air flux calculation in the Southern Ocean is still limited due to insufficient investigations. Herein, high-resolution shipboard underway simultaneous surface seawater and atmospheric DMS measurements were conducted in the Southern Ocean from February 23 to March 31, 2018. A larger variation of DMS levels was found in atmosphere compared with that in seawater. Remarkably, a large-scale area with high seawater and atmospheric DMS concentrations up to 27.9 nM and 3.92 ppbv, respectively, was investigated outside of Ross Sea sector. Atmospheric DMS levels were strongly impacted by wind speed and air mass convection. The relationship between atmospheric DMS and air mass exposure to oceanic chlorophyll varied greatly depending on the area of investigation. Some other regions with high DMS production capacity were examined as well beside those along the cruise tracks based on the results of positive correlations with high slopes and back trajectories. Moreover, significant uncertainty of sea-to-air DMS flux over the Southern Ocean could be caused by follows: (1) the selecting of different gas transfer coefficients; (2) the negative flux values calculated under high atmospheric DMS levels together with low seawater DMS concentrations; and (3) the greatly overestimated flux, approximately 47.1–76.9%, without considering the atmospheric DMS. This study highlights the urgent demand of high-resolution observations of atmospheric DMS over the Southern Ocean to estimate DMS emission with high accuracy.

Continental weathering intensity during the termination of the Marinoan Snowball Earth: Mg isotope evidence from the basal Doushantuo cap carbonate in South China

The Neoproterozoic global glaciations (720–635 Ma) represent the most severe icehouse climatic conditions in Earth's history, collectively known as the ‘Snowball Earth events’. The ‘Snowball Earth’ hypothesis (Hoffman et al. 1998) proposed that the termination of the global glaciation was driven by the extremely high atmospheric pCO2 level (300 times of present atmospheric level, PAL) that was accumulated during the global glaciation by volcanic degassing for tens of million years. Because of extremely high temperature, the deglaciation might associate with intense continental weathering that brought abundant bicarbonate and alkaline earth metals (Mg, Ca) to the ocean, resulting in the rapid precipitation of cap carbonate all over the world. Thus, cap carbonate precipitation marks the termination of global glaciation. The deglacial intense continental weathering has been recently supported by Mg isotopes. However, the Mg isotope data also indicate that the deglaciation might have significantly predated the cap carbonate precipitation, and limited data suggest that the weathering intensity was already low during the cap carbonate precipitation. In order to further test whether the cap carbonate precipitation was associated with low weathering intensity, here we analyzed Mg isotopic composition of siliciclastic component (δ26Mgsil) of the Doushantuo cap carbonate in the Yangtze Block, South China. Four cap carbonate sections (the Tongle (TL) drill core, the Fanyang (FY) section, the Wuluo (WL) drill core, and the Jiulongwan (JLW) section), spanning from shelf to basin environments, were analyzed. δ26Mgsil ranges from −0.43‰ to +0.39‰ (n = 10), from −0.31‰ to +0.48‰ (n = 9), from −0.06‰ to +0.10‰ (n = 7), and from −1.42‰ to −0.03‰ (n = 8) for the JLW, FY, WL, and TL samples, respectively. There are negative correlations between Mg/Al and δ26Mgsil in JLW, WL, and TL. The geochemical data indicate that the variation of δ26Mgsil might be attributed to authigenic clay formation during the cap carbonate precipitation. The binary mixing model indicates that the isotopic compositions of terrestrial clays range from 0‰ to +0.3‰, comparable to the values of modern soil clays but significantly lower than the values of the upper Nantuo Formation (up to ~ + 0.90‰), suggesting the moderate to low weathering intensity during the cap carbonate deposition. Our study suggests low atmospheric pCO2 level during cap carbonate precipitation probably due to the consumption by intense continental weathering

Optimal grid resolution for the detection lead time of cyclogenesis in the North Indian ocean

Early detection of disturbances in the atmospheric column, its spatio-temporal behavior and evolution prior to tropical cyclogenesis over warm ocean surface is a challenging problem. High-resolution atmospheric models help to better understand the atmospheric dynamical conditions and instability mechanism triggered by intense air-sea interaction leading to the formation of tropical cyclogenesis. Present study performed a series of model-based sensitivity experiments to evaluate tropical cyclogenesis lead detection time for five cyclone cases with varying grid resolutions ranging between 27 km and 12 km in the north Indian Ocean. High-resolution Weather Research and Forecast (WRF) model examined the evolution of pre-cyclonic eddy vortices in the vertical atmospheric column associated with Aila, Thane, Mora, Ockhi, and the recent Vayu cyclones. Detection technique was based on Okubo-Weiss (OW) parameter that is very sensitive to varying grid resolutions. Study examined the sensitivity of pre-cyclogenesis lead detection time to WRF model grid resolutions. Significant findings from the study indicate a good skill in genesis prediction with approximately four days (~90 h) lead time in all cases irrespective of pre- and post-monsoon seasons and the domain size. First part of this study reveals characteristic difference in the eddy detection between pre- and post-monsoon cyclones and its lead detection time. The lead detection time using a grid resolution of 27 km resulted in a lag-time of nearly one day (~24 h) for pre-monsoon cyclogenesis as compared to the post-monsoon cases. Interestingly, the pre-cyclonic eddies are detected at higher atmospheric levels (450–650 hPa) for the pre-monsoon unlike post-monsoon developing cases in the lower tropospheric levels (800–950 hPa). Secondly, a 15 km grid resolution with OW technique would suffice early tropical cyclogenesis detection found optimum in context to lead detection time (~15 h) that better resolves the structure of pre-cyclonic eddies useful for advanced prediction.

Unusual Atmospheric‐River‐Like Structures Coming From Africa Induce Extreme Precipitation Over the Western Mediterranean Sea

AbstractLong filaments of high integrated water vapor transport (IVT) content, widely known as atmospheric rivers (ARs), play a relevant role in the water cycle being also associated to many extreme flooding events worldwide. In this work we inspect whether similar structures can be found over the western Mediterranean. The methodology used here to detect these AR‐like structures is based on standard ARs detection methods but imposing a strong IVT advection westward component. The ERA5 global reanalysis and Spain02 high‐resolution gridded observational data set are used covering the period 1979–2017 to analyze the composites of mesoscale features and associated impacts on rainfall. Results show that AR‐like structures over the Mediterranean (abbreviated here Med‐ARs) have an approximately once‐per‐year frequency, but they are associated with extreme orographic precipitation contributing to more than 40% to the annual precipitation in some cases. During Med‐AR, IVT increases due to high horizontal winds and water vapor contents. Med‐ARs are associated to a cutoff cyclone with a cold core over northwestern Africa and warmer air mass over northern Europe. The vertical structure of Med‐ARs suggests an occluded front with a low level jet in the warmer front where Med‐ARs reside and moisture penetrating into high atmospheric levels where cold and warm front intersect. In conclusion, long filaments of IVT can be found over the western Mediterranean Sea playing a relevant role on hydrometeorological impacts. Although these structures share some features with ARs over the Pacific/Atlantic Ocean, they may not be considered the same meteorological phenomenon.

Influence of fly ash on concrete – A systematic review

Climate change is one of the most concerning issues existing. Carbon dioxide, which is a significant contributor to the greenhouse effect, is at the highest atmospheric levels ever recorded. The construction industry contributes to around 40% of carbon emissions produced all over the world. By consuming large amounts of non-renewable energy, the construction sector delivers infrastructure and buildings to society. This consumption consequently causes significant carbon dioxide emissions. The manufacture of cement contributes to greenhouse gasses both directly by producing carbon dioxide when calcium carbonate decomposes thermally, producing lime and carbon dioxide, and also by using electricity, especially from the combustion of fossil fuels. This paper focuses on studying the properties of fly ash and its impact on the characteristics and performance of concrete. Fly ash is a by-product that is obtained by the combustion of coal; thus, it is a waste product. The incorporation of this pozzolanic material which requires no manufacturing process like cement, as a replacement, contributes to sustainability by reducing the amount of cement used and also taking care of the disposal of fly-ash.