CO2 Accumulation Research Articles

Tourism’s Influence on Economic Growth and Environment in Saudi: Present and Future

Reports from the World Tourism Organization indicate that tourism activity has been increasingly booming; this sector is essential for economic growth and may affect the environment. Tourism is one of the key strategic sectors for planned growth in Saudi Arabia’s Vision 2030. This study is designed to evaluate the long-termning association between tourist arrivals, growth domestic product (GDP), and CO2 emissions in the Kingdom of Saudi Arabia (KSA). The data related to these variables were assessed for the period 2010 to 2020. The autoregressive distributed lag (ARDL) bounds results revealed that there are long-established relations between tourist arrivals and growth domestic product and tourist arrivals and CO2 emissions. The dynamic ordinary least squares (DOLS) and fully modified ordinary least squares (FMOLS) model outcomes were compatible with the outcomes of the ARDL model. In reference to the Granger causality test, tourist arrivals cause (affect) the GDP. Such a result confirms the conception that tourism encourages economic growth. No causality runs from tourist arrivals towards CO2 accumulation. This result may reflect the governmental effort to reduce CO2 accumulation and/or to perform tourism activities in a sustainable way. The results predicted that the growth rate of tourist arrivals, GDP, and CO2 accumulation equal 0.0023, 0.048, and 0.0169, respectively, during the forecast period (2021–2030), which appeared to be increasing for tourist arrivals and GDP and decreasing for CO2 accumulation. The study recommended that, to increase economic growth, tourist arrivals should be increased alongside performing tourism activities in a sustainable way. These findings point to the benefits of governance in ensuring effective policies to decarbonize the environment, and policy proposals are put forward accordingly.

Progress in carbon dioxide capture, storage and monitoring in geological landform

Carbon Capture and Storage (CCS) is recognized as a potent strategy for managing the accumulation of human-generated CO2 in the atmosphere, helping to alleviate climate change’s effects. The CO2 gas is captured from the point source through methods such as pre-treating fossil fuels, oxy-fuel combustion, or post-combustion capture; thereafter; it is transported to a storage location and injected into geological formations. This article provides an overview of carbon dioxide capture and sequestration, focusing on its key principles, technologies, associated risks, and challenges. Direct Air Capture (DAC) and Scalable Modelling, Artificial intelligence (Al), Rapid Theoretical calculations SMART technologies are detailed as emerging and promising approaches to CO2 capture. Numerous pilot and commercial projects commissioned to manage carbon dioxide emissions are presented. Additionally, the paper explores approaches combining geological, geophysical, geochemical, and environmental monitoring techniques to ensure the secure and sustainable storage of CO2 underground. These are essential to address uncertainties, minimize risks, and build public confidence in CCS as a viable climate mitigation strategy. The successful deployment of these technologies on a global scale will require continued innovation, particularly in the areas of monitoring, risk management, and public engagement. Emerging technologies such as AI and SMART systems could play a crucial role in enhancing the efficiency and safety of CCS operations. However, the integration of these advancements with existing infrastructure and regulatory frameworks remains a challenge. Ultimately, a multi-disciplinary approach, combining technological, economic, and regulatory perspectives, will be vital to realizing the full potential of CCS in combating climate change.

Assessment of Waste Animal Fats (WAFS) Biodiesel Production Potential as an Alternative Fuel for Zambia: A Case Study of Southern Province

The volatility in global fuel prices and the desire to reduce energy dependency on fossil fuels has necessitated the speeding up of alternative energy supply sources. Coupled to this is the global urgent need to reduce the accumulation of CO2 and green house gas (GHG) emissions as a result of fossil fuels production and use. Further, the mandate by united nations to move towards sustainably produced energy for the transportation, and power generation demands that we seek energy solutions that meet reduced negative impact on the environment. It is in this regard that this study seeks alternatives in waste animal fats (WAFs) biodiesel as an option that could meet the ever increasing demand for fossil fuel in the transport sector and power generation. For the transport sector and power generation , the biodiesel maybe blended with the fossil diesel in the approved ratios as stipulated by the Energy Regulation Board and the Zambia Bureau of Standards to help mitigate the net GHG and CO2 emissions. The biodiesel production in this study was based on the modified two-step process. These two steps involved passing the feedstock through esterification using sulphuric acid as catalyst and there after base catalysed using sodium hydroxide in a process referred to as transesterification. The resulting products in the esterification process are the esters and water whilst in the transesterification are the biodiesel and glycerol. The feedstock used are those of waste animal fats (WAFs) of cattle, pig and chicken that has been discarded from meat processing and animal slaughter houses. The feedstocks have been carefully selected based on the animals raised in the country with a bigger slaughtered population as well as reared. The population of animals reared and slaughtered annually are obtained from the Zambia Ministry of Agriculture animal population census records. Based on these records, the preferred feedstock sources where obtained. The study further 1. explored the economic potential of the biodiesel production for the Zambian government and beyond. 2. compared some of the characteristics of WAF biodiesel to that of imported fossil diesel 3. affirmed that WAF biodiesel has a very good impact in reducing environmental pollution as WAF dumping to land fills and the cost of disposal is reduced. Also,WAF biodiesel is bio-degradable. Thus, moving closer to an effective sustainable development as required by the united nations sustainability goals if full scale production is implemented in Zambia.

Interannual and seasonal variability of the air–sea CO2 exchange at Utö in the coastal region of the Baltic Sea

Abstract. Oceans alleviate the accumulation of atmospheric CO2 by absorbing approximately a quarter of all anthropogenic emissions. In the deep oceans, carbon uptake is dominated by aquatic phase chemistry, whereas in biologically active coastal seas the marine ecosystem and biogeochemistry play an important role in the carbon uptake. Coastal seas are hotspots of organic and inorganic matter transport between the land and the oceans, and thus they are important for the marine carbon cycling. In this study, we investigate the net air–sea CO2 exchange at the Utö Atmospheric and Marine Research Station, located at the southern edge of the Archipelago Sea within the Baltic Sea, using the data collected during 2017–2021. The air–sea fluxes of CO2 were measured using the eddy covariance technique, supported by the flux parameterization based on the pCO2 and wind speed measurements. During the spring–summer months (April–August), the sea was gaining carbon dioxide from the atmosphere, with the highest monthly sink fluxes typically occurring in May, being −0.26 µmol m−2 s−1 on average. The sea was releasing the CO2 to the atmosphere in September–March, and the highest source fluxes were typically observed in September, being 0.42 µmol m−2 s−1 on average. On an annual basis, the study region was found to be a net source of atmospheric CO2, and on average, the annual net exchange was 27.1 gC m−1 yr−1, which is comparable to the exchange observed in the Gulf of Bothnia, the Baltic Sea. The annual net air–sea CO2 exchanges varied between 18.2 (2018) and 39.1 gC m−1 yr−1 (2017). During the coldest year, 2017, the spring–summer sink fluxes remained low compared to the other years, as a result of relatively high seawater pCO2 in summer, which never fell below 220 µatm during that year. The spring–summer phytoplankton blooms of 2017 were weak, possibly due to the cloudy summer and deeply mixed surface layer, which restrained the photosynthetic fixation of dissolved inorganic carbon in the surface waters. The algal blooms in spring–summer 2018 and the consequent pCO2 drawdown were strong, fueled by high pre-spring nutrient concentrations. The systematic positive annual CO2 balances suggest that our coastal study site is affected by carbon flows originating from elsewhere, possibly as organic carbon, which is remineralized and released to the atmosphere as CO2. This coastal source of CO2 fueled by the organic matter originating probably from land ecosystems stresses the importance of understanding the carbon cycling in the land–sea continuum.

Seasonal Variations of Ice-Covered Lake Ecosystems in the Context of Climate Warming: A Review

The period of freezing is an important phenological characteristic of lakes in the Northern Hemisphere, exhibiting higher sensitivity to regional climate changes and aiding in the detection of Earth’s response to climate change. This review systematically examines 1141 articles on seasonal frozen lakes from 1991 to 2021, aiming to understand the seasonal variations and control conditions of ice-covered lakes. For the former, we discussed the physical structure and growth characteristics of seasonal ice cover, changes in water environmental conditions and primary production, accumulation and transformation of CO2 beneath the ice, and the role of winter lakes as carbon sources or sinks. We also proposed a concept of structural stratification based on the differences in physical properties of ice and solute content. The latter provided an overview of the ice-covered period (−1.2 d decade−1), lake evaporation (+16% by the end of the 21st century), the response of planktonic organisms (earlier spring blooming: 2.17 d year−1) to global climate change, the impact of greenhouse gas emissions on ice-free events, and the influence of individual characteristics such as depth, latitude, and elevation on the seasonal frozen lakes. Finally, future research directions for seasonally ice-covered lakes are discussed. Considering the limited and less systematic research conducted so far, this study aims to use bibliometric methods to synthesize and describe the trends and main research points of seasonal ice-covered lakes so as to lay an important foundation for scholars in this field to better understand the existing research progress and explore future research directions.

Reconstructing CO2 uptake capacity and pH dynamics in the Middle Ordovician Taebaeksan Basin, Korea

This study presents the first continuous carbonate boron isotope (δ11Bcarb) record from Middle Ordovician carbonate rocks, focusing on the Taebaek section in Korea. The δ11Bcarb values analyzed from the Makgol, Jigunsan, and Duwibong formations range between 7.5 ‰ and 17.8 ‰, falling within the published Paleozoic range. Samples exhibit minimal diagenetic alteration, as evidenced by weak correlations between isotopic factors and elemental ratios (δ11Bcarb, δ13Ccarb, δ15Nbulk, B/Ca, Mn/Sr, and Na/Ca) as well as mineralogical observations used to select unaltered micrite portions. Using the δ11Bcarb data, we reconstruct pH levels (8.4 to 9.1) which suggest that this shallow shelf environment acted as a CO2 sink during the Middle Darriwilian, despite periods of acidification coinciding with sea level rise and expansion of anoxic zones. Weakening of the basin's CO2 uptake capacity via reduced CaCO3 precipitation and photosynthesis accompanied these oceanographic changes. Our findings provide new insights into the dynamics of CO2 accumulation and pH in Middle Ordovician shallow marine settings in relation to sea level fluctuations. This work lays the foundation for further research into ocean chemistry and carbon cycle perturbations during this important period in Earth's history.

Winter CH4 and CO2 Accumulation from a Permafrost Peatland Pond is Critical to Spring thaw Carbon Emissions

Winter CH4 and CO2 Accumulation from a Permafrost Peatland Pond is Critical to Spring thaw Carbon Emissions

Influence of Biomass Amendments on Soil CO2 Concentration and Carbon Emission Flux in a Subtropical Karst Ecosystem

Soil in karst areas is rare and precious, and karst carbon sinks play an important role in the global carbon cycle. Therefore, the purpose of karst soil improvement is to improve soil productivity and a carbon sink effect. Biomass amendment experiments in this study included three schemes: filter mud (FM), filter mud + straw + biogas slurry (FSB), and filter mud + straw + cow manure (FSC). The characteristics of soil CO2 production, transport, and the effect on soil respiration carbon emissions in two years were compared and analyzed. The results were as follows: 1. The rate, amount, and depth of CO2 concentration were affected by the combinations with biogas slurry (easy to leach) or cow manure (difficult to decompose). 2. The diurnal variation curves of soil respiration in the FSB- and FSC-improved soils lagged behind those in the control soil for three hours. While the curves of FM-improved soil and the control soil were nearly the same. 3. Soil–air carbon emissions increased by 35.2 tCO2/(km2·a−1) under the FM scheme, decreased by 212.9 tCO2/(km2·a−1) under the FSB scheme, and increased by 279.5 tCO2/(km2·a−1) under the FSC scheme. The results were related to weather CO2 accumulation in the deep or surface layers under different schemes.

Model-driven design and validation of glucose supply control in a tubular photobioreactor operated under oxygen-balanced mixotrophy

Scaling up bioprocesses remains challenging due to the partially unpredictable and suboptimal behavior of microbes during scale transition. Mathematical modelling serves as a valuable tool in navigating these challenges. In this study, we developed and validated a kinetic model based on the tank-in-series approach for a novel bioprocess known as oxygen-balanced mixotrophy with the microalga Galdieria sulphuraria. This model aims to facilitate the design of an effective glucose feeding control strategy tailored for two-phase tubular photobioreactors (TPBRs). The residence time distribution of our reference reactor was investigated by means of a tracer experiment. Qualitative analysis of the results indicated that our system was optimally represented by simulations with a 100 stirred-tank reactors (STRs).The controlled variable, oxygen concentration in the gas phase, showed a downward trend in simulations with simplified conditions: fixed oxygen production and balanced glucose supply. The decrease was caused by dominant net heterotrophic activity and accumulation of CO2 in the gas phase. Different configurations of a proportional-integral-derivative (PID) controller were designed by means of the ultimate gain method and compared under these simplified conditions. The most effective PID controller was implemented and refined in simulations with outdoor weather conditions. The model was validated successfully by simulating over time in a lab-scale STR the spatial fluctuations happening in a TPBR. The empirical oxygen consumption and production were faster and steeper than in the model, probably due to inaccuracies in parameter estimation or biomass adaptation.

Examination of the use of binderless zeolite blend as backfill materials to enhance CO2 adsorption in coal mine working face

The release and accumulation of CO2 in the working face of the coal mine is a major safety concern and requires an effective means to avoid the incidence of the mine. This present study therefore sought to develop a self-CO2 adsorbing backfill (SCAB) material to remove CO2 from the working environment, and simultaneously mitigate the movements of the surrounding rock layers. SCAB was formulated using coal mine solid waste activated with an alkali activator, and binderless 4 A zeolite was embedded in the backfill body. The total CO2 adsorption capacity was investigated using a CO2 flow-through method under ambient pressure and temperature conditions. The adsorption plateau was found in stages II and III respecting the predetermined curing time and zeolite contents. The maximum adsorption capacity was 143.8 mg-CO2/g-SCAB, resulting in an increase of up to 82 % in UCS compared to reference samples. The underlying mechanism was discovered in morphological analyses.1) The well distribution of zeolite in the SCAB body provided as diffusive pathways and adsorption sites for CO2 after standard curing. 2) The adsorbed CO2 underwent a desorption stage when the CO2 concentration decreased and reacted to the cementitious matrix of the SCAB body. 3) More CaCO3 crystals were generated and filled in the micro spaces of the SCAB body, which contributed to an increase in compressive strength. This study developed an effective approach to remove CO2 gas from the working face of the coal mine during backfilling. Adsorbed CO2 improved the strength of the material, provided as a novel multi-function backfill mining for sustainable green coal mining technology.

The influence of N95 and surgical masks on carbon dioxide levels: A comprehensive systematic review and meta-analysis

ObjectivesThis study aimed to assess the impact of wearing N95 and surgical masks on carbon dioxide (CO2) concentrations during various activity levels, to understand the implications for mask use in different settings, especially in light of the COVID-19 pandemic. Study designSystematic Review and Meta-Analysis. MethodsA systematic review was conducted, retrieving 6798 articles from PubMed, Web of Science, and Scopus databases. Twenty-nine articles met the inclusion criteria. Mask types were categorized into N95 and surgical masks, while activities were classified as low, medium, and high. ResultsThe meta-analysis revealed CO2 concentrations (mmHg) for different scenarios: No mask (37.91, 95 % CI: 36.46, 39.35), N95-low (36.83, 95 % CI: 33.57, 40.10), N95-moderate (37.85, 95 % CI: 36.51, 39.20), N95-high (39.51, 95 % CI: 38.00, 41.02), N95 with exhalation valve (35.82, 95 % CI: 32.89, 38.75), N95 without exhalation valve (38.45, 95 % CI: 37.10, 39.81), surgical mask-low (38.31, 95 % CI: 34.48, 42.14), surgical mask-moderate (35.05, 95 % CI: 31.12, 38.97), surgical mask-high (36.07, 95 % CI: 34.18, 37.96). ConclusionsOur findings indicate that N95 masks lead to higher CO2 accumulation during various activities compared to surgical masks. Moreover, surgical masks exhibit higher CO2 concentrations during low activity compared to moderate and high activities. Notably, CO2 concentrations are higher in N95 masks without an exhalation valve compared to those with a valve. No significant difference was observed between not wearing a mask and wearing either N95 or surgical masks in terms of CO2 accumulation. These results provide important insights for mask selection and usage recommendations in different scenarios.

Influence of Human Activity on Radon Concentration, Indoor Air Quality, and Thermal Comfort in Small Office Spaces.

This article focuses on the influence of occupants on the concentration of contaminants (radon Rn-222 and CO2) as well as the thermal comfort parameters. A series of sensors were placed to measure the concentration of the contaminants, temperature, and relative humidity in the test room at the Institute of Nuclear Physics PAN in Krakow (IFJ PAN), Poland. The test room is an office that is typical of the offices used in the facility. The occupants that used the space kept a detailed diary of their entry, exit, and number of people entering. The results showed that the accumulation of contaminants in such spaces may be severe and risks the health and safety of occupants. The accumulation of CO2 was extremely noticeable and did not diminish to the background level between the re-entry of the occupants to the office. The same was consistent for the radon concentration. The study shows how ventilation methods and small changes in occupant work strategy may influence the contaminant concentration within a test zone.

Increasing dissolved oxygen concentration of irrigation water is beneficial to nitrogen uptake of cotton under mulched drip irrigation

ContextEnhancing crop nitrogen absorption is crucial for improving nitrogen fertilizer utilization efficiency. Soil oxygen conditions play a vital role in influencing crop nutrient uptake. However, the impact of dissolved oxygen concentration in irrigation water on cotton’s nitrogen absorption remains unknow under mulched drip irrigation conditions. RESEARCH QUESTION: This study aimed to investigate whether the dissolved oxygen concentration in irrigation water affects cotton’s nitrogen uptake. METHODS: Urea was utilized as the nitrogen fertilizer, and 5 dissolved oxygen concentration of irrigation water were set in the experiment by adding sodium percarbonate (CK: 3.9 mg L−1, CO1: 9.2 mg L−1, CO2: 13.3 mg L−1, CO3: 17.3 mg L−1, CO4: 25.5 mg L−1). RESULTS: The results showed that increasing the dissolved oxygen concentration in irrigation water could increase the soil urease activity and bacterial operational taxonomic units (OTU), which may be beneficial to the urea decomposition and nitrogen cycling function. Towards the end of the cotton growth period, oxygenation irrigation led to an increase in nitrate nitrogen and ammonium nitrogen content in the soil. The average nitrate nitrogen content in the 0–60 cm soil layer of CO1, CO2, CO3 and CO4 increased by 12.4 %, 14.7 %, 15.9 % and 17.3 % respectively compared with CK. Similarly, the average ammonium nitrogen content of CO1, CO2, CO3 and CO4 in the 0–40 cm soil layer increased by 8.9 %, 11.7 %, 12.0 % and 11.6 % respectively compared with CK. Increasing the dissolved oxygen concentration in irrigation water resulted in elevated dry matter accumulation in cotton. The total dry matter of CO1, CO2, CO3 and CO4 increased by 9.5 %, 12.6 %, 14.6 % and 16.8 % respectively compared with CK. Additionally, the nitrogen concentration in each cotton organ also exhibited an increase. The total nitrogen accumulation of CO1, CO2, CO3 and CO4 increased by 26.1 %, 36.2 %, 48.2 % and 53.1 % respectively compared with CK. Furthermore, increasing the dissolved oxygen concentration in irrigation water also facilitated nitrogen migration to cotton bolls (boll shell + seed + fiber). The cotton boll nitrogen accumulation of CO1, CO2, CO3 and CO4 increased by 1.8 %, 3.4 %, 4.2 % and 4.2 % (absolute value) compared with CK (reached significant level). Finally, the lint yield and fiber quality parameters (micronaire, fiber elongation, fiber breaking strength) exhibited further improvement with the increase in dissolved oxygen concentration in irrigation water. CONCLUSIONS: Increasing the dissolved oxygen concentration in irrigation water promotes nitrogen absorption in cotton, facilitates nitrogen accumulation in cotton bolls, and enhances nitrogen fertilizer utilization efficiency. Moreover, it positively impacts cotton lint yield and fiber quality.

High thermodynamical sensitivity of CO2 emissions from a large oligotrophic-hardwater lake (Nam Co) on the Tibetan Plateau

The Tibetan Plateau (TP) has the world's largest distribution of high-alpine and saline (generally hardwater) lakes, which are expected to affect regional carbon cycling profoundly. However, the variability, and especially underlying factors controlling CO2 dynamics, across widespread hardwater lakes is poorly understood on the TP. Here, we present year-round records of surface water pCO2 from a representative hardwater lake (Nam Co) on the TP, and analyze relationships between ambient variables and pCO2 during open water (i.e., ice-free) and ice-covered months. Surface pCO2 (233.3 μatm on average) was a little oversaturated to atmosphere (219 μatm on average) during the open water season. As a CO2 source, Nam Co emitted 8.73 ± 1.06 Gg C annually, but this flux only accounted for 0.53 ± 0.06 ‰ of its total dissolved inorganic carbon pool (1.64 × 1013 g C). Regression results indicate that, during open water months, both seasonal and diurnal varying patterns of surface pCO2 were influenced predominantly by water temperature, in a quasi-marine mode, by controlling gas solubility and dissolved carbonate equilibria. Therefore, CO2 evasion was elevated during summer months, despite the lake being autotrophic (i.e., CO2 consumption via photosynthesis). By contrast, during ice-covered months the surface pCO2 was strongly related to under-ice thermodynamics, and declined nonlinear with increased inversed stratification. In the hypolimnion, as a result of extremely weak metabolism (as indicated by low dissolved oxygen depletion rates) and a combined high carbonate buffering effect, accumulation of CO2 was negligible, leading to an absence of peak effluxes of CO2 during turnover periods, compared to eutrophic freshwater lakes. We argue that, under future global warming scenarios, consideration of the impact of gradually warming lake water on thermodynamics and dissolved carbonate equilibria are vital in order to understand the future CO2 dynamics of these widespread high-altitude oligotrophic-hardwater lakes situated across the TP.

CO2 Concentration Assessment for Infection Monitoring and Occupancy Analysis in Tanzanian COVID-19 Isolation Centers

Monitoring of IAQ is one of the foundations of the preventative actions prompted by the worldwide recognition of COVID-19 transmission. The measurement of CO2 has emerged as one of the most popular, dependable, and easy ways to indirectly evaluate the state of indoor air renewal. Reducing the risk of respiratory diseases transmitted by aerosols is attainable through implementing and validating prevention measures made possible by CO2 control. Isolation centers are like health facilities in that they are linked to IAQ, and the presence of natural ventilation can significantly improve the circulation of fresh air, which speeds up the removal of contaminants. This is true even though healthcare facilities are among the environments with the highest rate of COVID-19 propagation. Our investigation revealed, however, that no substantial critical data on air quality in Tanzanian isolation centers is presently available. The process of metabolic CO₂ creation and accumulation within health isolation center cubicles was investigated in this study. Crucially, we suggest comparing settings under various conditions using the indicator ppm/patient. In this research, we experimentally assessed the value of changing a few HVAC system characteristics. We looked at the data to see how well the filtration system worked concerning the submicron particle concentration. Study recommendations for CO2 detectors and ways to reduce infection risk in shared isolation center cubicles are provided. We also show the correlation between particle size and CO2 concentration, the correlation between CO2 concentration derivatives and air volume presented per patient in isolation cubicles, the correlation between patient occupancy and CO2 concentration levels in isolation cubicles, and how to improve air quality by adjusting the patient’s bed position. The study also found that for exposure lengths of two to three hours, a typical hospital cubicle with fifty to one hundred people should have an average interior CO₂ value of less than 900 ppm. Carers’ length of stay in the hospital substantially impacted the permissible CO2 concentration. By establishing a connection between indoor air monitoring and healthcare goals, this study will aid in determining the feasibility of establishing regulations for interior CO2 content depending on occupancy settings, strengthening preventive efforts against COVID-19. In the post-pandemic era, it will be essential to find ways to make health facilities air cleaner so that infectious diseases cannot spread in the future.

Carbon Cycle Instability for High-CO2 Exoplanets: Implications for Habitability

Implicit in the definition of the classical circumstellar habitable zone (HZ) is the hypothesis that the carbonate-silicate cycle can maintain clement climates on exoplanets with land and surface water across a range of instellations by adjusting atmospheric CO2 partial pressure (pCO2). This hypothesis is made by analogy to the Earth system, but it is an open question whether silicate weathering can stabilize climate on planets in the outer reaches of the HZ, where instellations are lower than those received by even the Archean Earth and CO2 is thought likely to dominate atmospheres. Since weathering products are carried from land to ocean by the action of water, silicate weathering is intimately coupled to the hydrologic cycle, which intensifies with hotter temperatures under Earth-like conditions. Here, we use global climate model simulations to demonstrate that the hydrologic cycle responds counterintuitively to changes in climate on planets with CO2-H2O atmospheres at low instellations and high pCO2, with global evaporation and precipitation decreasing as pCO2 and temperatures increase at a given instellation. Within the Maher & Chamberlain (or MAC) weathering formulation, weathering then decreases with increasing pCO2 for a range of instellations and pCO2 typical of the outer reaches of the HZ, resulting in an unstable carbon cycle that may lead to either runaway CO2 accumulation or depletion of CO2 to colder (possibly snowball) conditions. While the behavior of the system has not been completely mapped out, the results suggest that silicate weathering could fail to maintain habitable conditions in the outer reaches of the nominal HZ.

Weathering, redox proxies and carbon isotope data from the Maokou Formation, Upper Yangtze, South China: Implications for the Guadalupian P3 glaciation of the Late Paleozoic Ice Age

Late Paleozoic Ice Age (LPIA) was a key climate event of the deep-time earth evolution system. Although the sedimentary successions from eastern Australia have well constrained the timeframe of the glacial-nonglacial intervals, the link between these glaciations and coeval geological events is still being explored. The Guadalupian (Middle Permian) P3 glaciation was the prelude to the upcoming end of LPIA, which is a key window to examine the uncertainty of the climatic transition from icehouse to greenhouse and linkages with the geological and biological events. This study focuses on the marine sedimentary succession of the Shangsi outcrop located in the low-latitude Yangtze block, investigating the carbon/strontium isotopes, redox proxy, and chemical index of alteration (CIA). Multiple weathering indices revealed climatic fluctuations during the Guadalupian, corresponding to the onset and demise of the high-latitude P3 glaciation. The high level of CIA following the Kungurian-age Large Igneous Provinces (LIPs) event indicates that the weathering of basic rocks caused the positive 13C drift, which was the main factor for the onset of the P3 glaciation. Then the breakup of Pangea, enhanced ocean oxidation, and a series of volcanic activities including Emeishan LIP could contribute to the accumulation of CO2 and consequently cause the demise of the P3 glaciation in middle Capitanian. Enhanced continental weathering was synchronous with the eruption surge of the volcanic activities, indicating a following global warming event, which may play a crucial role in triggering the Mid-Capitanian extinction event.

Anthropogenic CO2, air–sea CO2 fluxes, and acidification in the Southern Ocean: results from a time-series analysis at station OISO-KERFIX (51° S–68° E)

Abstract. The temporal variation of the carbonate system, air–sea CO2 fluxes, and pH is analyzed in the southern Indian Ocean, south of the polar front, based on in situ data obtained from 1985 to 2021 at a fixed station (50°40′ S–68°25′ E) and results from a neural network model that reconstructs the fugacity of CO2 (fCO2) and fluxes at monthly scale. Anthropogenic CO2 (Cant) is estimated in the water column and is detected down to the bottom (1600 m) in 1985, resulting in an aragonite saturation horizon at 600 m that migrated up to 400 m in 2021 due to the accumulation of Cant. At the subsurface, the trend of Cant is estimated at +0.53±0.01 µmol kg−1 yr−1 with a detectable increase in the trend in recent years. At the surface during austral winter the oceanic fCO2 increased at a rate close to or slightly lower than in the atmosphere. To the contrary, in summer, we observed contrasting fCO2 and dissolved inorganic carbon (CT) trends depending on the decade and emphasizing the role of biological drivers on air–sea CO2 fluxes and pH inter-annual variability. The regional air–sea CO2 fluxes evolved from an annual source to the atmosphere of 0.8 molC m−2 yr−1 in 1985 to a sink of −0.5 molC m−2 yr−1 in 2020. Over 1985–2020, the annual pH trend in surface waters of -0.0165±0.0040 per decade was mainly controlled by the accumulation of anthropogenic CO2, but the summer pH trends were modulated by natural processes that reduced the acidification rate in the last decade. Using historical data from November 1962, we estimated the long-term trend for fCO2, CT, and pH, confirming that the progressive acidification was driven by the atmospheric CO2 increase. In 59 years this led to a diminution of 11 % for both aragonite and calcite saturation state. As atmospheric CO2 is expected to increase in the future, the pH and carbonate saturation state will decrease at a faster rate than observed in recent years. A projection of future CT concentrations for a high emission scenario (SSP5-8.5) indicates that the surface pH in 2100 would decrease to 7.32 in winter. This is up to −0.86 lower than pre-industrial pH and −0.71 lower than pH observed in 2020. The aragonite undersaturation in surface waters would be reached as soon as 2050 (scenario SSP5-8.5) and 20 years later for a stabilization scenario (SSP2-4.5) with potential impacts on phytoplankton species and higher trophic levels in the rich ecosystems of the Kerguelen Islands area.

Wind as a Driver of Peat CO2 Dynamics in a Northern Bog.

The online version contains supplementary material available at 10.1007/s10021-024-00904-1.

Preliminary tests on carbon and nitrogen emissions and nutrients availability upon application of algal-bacterial granules to arid and low fertility soil

To remediate arid and low fertility soil and explore the feasibility of controlling its carbon (C) and nitrogen (N) emissions, algal-bacterial aerobic granular sludge (AGS) was applied as soil additives and compared with bacterial AGS and cyanobacteria during 14 days’ incubation. Results show that algal-bacterial AGS as additives possesses a higher potential in terms of fertility recovery and soil physicochemical properties conservation. The additives may change the soil characteristics by decreasing soil pH (within 0.6) and water content (0.8–2.5 %) with increased electrical conductivity during the 14 days’ incubation. As for soil fertility, due to the high available phosphorus (P) content in algal-bacterial AGS, the soil available P content was significantly increased from 50 % to 170 % after incubation under different application rates or gaseous environments. N was also accumulated in the soil matrix with increased inorganic forms and less or acceptable N emission. The contents of soluble organic substances and extracellular polymeric substances (EPS) were significantly increased after incubation. Under ambient air and moderately elevated CO2 like 10 % conditions, carbon mineralization in the soil samples was lower than 15 % at low additives dosages; while under an elevated CO2 content (25 %) condition, a higher additives dosage may cause a rapid CO2 accumulation within 2 days with a substantial O2 consumption, leading to an anaerobic/anoxic environment corresponding to a higher C mineralization and/or N loss.