Increase In Atmospheric Carbon Dioxide Research Articles

Advancements in covalent organic framework‐based nanocomposites: Pioneering materials for CO2 reduction and storage

AbstractThe persistent increase in atmospheric carbon dioxide (CO2) concentration poses a significant contemporary challenge. Contemporary chemistry is heavily focused on sustainable solutions, particularly the photo‐/electrocatalytic reduction of CO2 and its utilization for energy storage. Despite promising prospects, efficient chemical CO2 conversion faces obstacles such as ineffective CO2 uptake/activation and catalyst mass transport. Covalent organic frameworks (COFs) have emerged as potential catalysts due to their precise structural design, functionalizable chemical environments, and robust architectures. COF‐based materials, especially those incorporating diverse active sites like single metal sites, metal nanoparticles, and metal oxides, hold promise for CO2 conversion and energy storage. This review sheds light on CO2 photoreduction/electroreduction and storage in Li‐CO2 batteries catalyzed by COF‐based composites, focusing on recent advancements in integrating COFs with nanoparticles for CO2 reduction. It discusses design principles, synthesis methods, and catalytic mechanisms driving the enhanced performance of COF‐based nanocomposites across various applications, including electrochemical reduction, photocatalysis, and lithium CO2 batteries. The review also addresses challenges and prospects of COF‐based catalysts for efficient CO2 utilization, aiming to steer the development of innovative COF‐based nanocomposites, thus advancing sustainable energy technologies and environmental stewardship. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.

Changes in litter and nitrogen deposition differentially alter forest soil organic matter biogeochemistry

Global climate change has altered forest productivity across the globe. Although extreme drought and temperature have lowered forest productivity in some regions, increased productivity has been observed in many forests over the last few decades due to increases in atmospheric carbon dioxide, temperature, and nitrogen (N) deposition. These factors can lead to changes in both the quantity and quality of litterfall and root inputs to soil. Additionally, few studies have investigated multifactorial treatments (e.g., detrital changes and N deposition), on soil carbon (C) sequestration. To investigate the long-term compositional changes to soil organic matter (SOM) in response to litter and N inputs, soil samples were collected from the University of Michigan Biological Station (UMBS) Detrital Input and Removal Treatment (DIRT) site after 15 years of experimental treatments. The samples were characterized using elemental analysis, targeted SOM compound analyses, nuclear magnetic resonance spectroscopy and microbial biomass and community composition measurements. The exclusions of C inputs (litter and/or roots) resulted in molecular-level biogeochemical changes, however, the soils at UMBS are seemingly more resistant to losses in soil C compared to other DIRT studies. Although the addition treatments (Double Litter, Double Wood, Double Litter + N, and N) led to increased soil C concentrations at UMBS, we found evidence for enhanced SOM decomposition occurring with litter additions. Notably, the observations made from the concurrent treatment of Double Litter + N demonstrated that the responses of individual treatments are not representative of simultaneous applications. Collectively, these results demonstrate that soil C biogeochemistry is sensitive to fluctuations in C and N deposition and overall, these processes are dictated by site-specific ecological properties.

Exploring the Responses of Teak and Eucalyptus to Elevated Carbon Dioxide in a Changing Atmosphere

Global warming plays a major role in climate change that is mainly caused by the increase of atmospheric carbon dioxide (CO2) and other greenhouse gases (GHGs) such as Methane (CH4), Nitrous oxide(N2O) and Chloro Fluoro Carbons (CFC) level in the last two decades. These greenhouse gases partially absorb long wave radiation remitted by the earth’s warm surface and re-emit the same resulting in warming up in the atmosphere. Climate change can be identified by changes in mean and variability of its properties. Climate changes are operated by the increase of (Green House gases) of them Carbon dioxide (CO2) is one of the most important greenhouse gases because of which influence the growth and morphology of industrially important tree species in tropics. Teak and Eucalyptus are the economically important tree species grown throughout the world in current study found that morphological, physiological and biochemical changes under elevated CO2 conditions. Forests, comprising diverse ecosystems and housing a plethora of plant species, play a critical role in mitigating climate change by acting as carbon sinks. Among the key contributors to this dynamic, Teak and Eucalyptus, as prominent tropical tree species, have been identified for their potential to sequester carbon dioxide (CO2) and influence ecosystem dynamics. Understanding how these trees respond to elevated CO2 levels is imperative for predicting the resilience and adaptability of forest ecosystems in the face of ongoing climate change. As we navigate a changing climate, unraveling the intricacies of how these vital tree species interact with elevated CO2 provides crucial insights for informed forest management and conservation practices.

Recent developments in ionophore-based potentiometric electrochemical sensors for oceanic carbonate detection

The increasing oceanic absorption of atmospheric CO2 decreases the ocean's carbonate and pH levels, harming marine life. This review covers carbonate electrochemical sensors based on ionophores for the advancement of ocean acidification research.

Progress in Post-Combustion Technology for Carbon Dioxide Capture

In the face of climate change and global warming caused by the increase in atmospheric carbon dioxide released by the combustion of fossil fuels, carbon capture technologies become pivotal for mitigating greenhouse gas emissions, particularly carbon dioxide. Among these carbon capture technologies, post-combustion capture has gained widespread application. In this article, the absorption and adsorption methods in post-combustion carbon capture technology, including the mechanism of the chemical and physical aspects of both methods as well as the absorbents and adsorbent materials used in them, will be specifically introduced. Moreover, the current and potential applications in the field of emissions reduction are also elaborated. These post-combustion carbon capture methods are expected to reduce environmental harm while maintaining energy efficiency, providing an effective solution to the problem of global warming.

Effects of Ocean Acidification on the Marine Organisms

Climate change is a severe environmental issue which can mainly be caused by anthropogenic activities like deforestation. It can cause another severe environmental issue called ocean acidification. It is worth seeking how ocean acidification occurs and how ocean acidification affects marine organisms including marine animals, marine plants and marine microorganisms. The increase of atmospheric carbon dioxide can be a dominant driver of ocean acidification. Ocean acidification can adversely influence marine animals like oysters. It can also either cause positive or negative impacts on marine plants. Marine microorganisms and marine biodiversity can also be sensitive to ocean acidification. Multiple strategies can be implemented to mitigate ocean acidification such as atmospheric carbon dioxide removal, growing of coastal seagrass, educational activities, and cultivation of marine submerged aquatic vegetation. However, the effectiveness and efficiency of mitigation strategies still need to be tracked in the long term. The quality of data collection for implementing the mitigation strategies is essential to determine and predict the response of the ocean towards to mitigation of ocean acidification.

Impact of Heavy Metals on the Climate Change

One of the most significant issues facing decision-makers who are committed to achieving the Sustainable Development Goals as outlined in the 2030 Agenda for Sustainable Development is climate change. The effects of climate change are already being seen, including rising temperatures, altered precipitation patterns, changes in ocean currents, melting of ice sheets, rising sea levels, and an increase in the frequency and severity of sea level events. Other effects include melting permafrost, retreating glaciers and ice sheets, an increase in fire-friendly weather, and an increase in the frequency and severity of extreme weather events. This has caused the climate change, including an increase in atmospheric carbon dioxide, along with other climate gasses. Increased frequency and severity of extreme weather events, such as hurricanes, cyclones, and heavy rain, which may affect water quantity and quality, are among them. The primary releases of hazardous chemicals like heavy elements have increased, and this has had an impact on the climate. Keywords: Heavy metals; climate change, Air pollution, water pollution, soil pollution, sediment pollution, measure control pollution.

Geostrophic and Mesoscale Eddy Contributions to the Atlantic Meridional Overturning Circulation Decline under CO2 Increase in the GFDL CM2-O Model Suite

Abstract The pattern and magnitude of the Atlantic meridional overturning circulation (AMOC) in response to an increase in atmospheric carbon dioxide (CO2) concentration greatly differ across climate models in particular due to differences in the representation of oceanic processes. Here, we investigate the response of the AMOC to an idealized climate change scenario, along with the drivers of this response, in the three configurations of a coupled climate model suite with varying resolutions in the ocean (1°, 0.25°, 0.10°). In response to the CO2 increase, the AMOC shows a reduction of similar magnitude in the low and high resolutions, while a muted response is found in the medium resolution. A decomposition of the AMOC into its geostrophic and residual components reveals that most of the AMOC reduction is due to a weakening of the geostrophic streamfunction driven by temperature anomalies, partly opposed by a strengthening of the geostrophic streamfunction driven by salinity anomalies. Changes in the AMOC due to the mesoscale eddy streamfunction contribute to 13% and 17% of the AMOC decline in the low and high resolutions, respectively, but induce very little change in the medium resolution. The similar response of the AMOC strength in the low and high resolutions hides important differences in the contribution and pattern of the geostrophic and eddy streamfunctions. The lack of sensitivity of the medium resolution to the CO2 forcing is due to a weak connection between the deep water formation regions in the northern subpolar gyre and the Deep Western Boundary Current. Significance Statement The Atlantic meridional overturning circulation (AMOC) is a major system of ocean currents in the Atlantic that contributes to shaping the climate at regional and global scales, notably through the transport of heat from the low to the high latitudes. A major slowdown of the AMOC over the twenty-first century is predicted by current climate models in response to increasing greenhouse gases. Yet, the magnitude and timing of this slowdown are uncertain. The purpose of this study is to investigate the expected weakening of the AMOC using state-of-the-art numerical climate models that include higher resolutions than typically used in climate change assessments. Our results provide insights into the mechanisms driving the weakening of the AMOC and into differences arising from model resolutions.

Anthropogenic acidification of surface waters drives decreased biogenic calcification in the Mediterranean Sea

Anthropogenic carbon dioxide emissions directly or indirectly drive ocean acidification, warming and enhanced stratification. The combined effects of these processes on marine planktic calcifiers at decadal to centennial timescales are poorly understood. Here, we analyze size normalized planktic foraminiferal shell weight, shell geochemistry, and supporting proxies from 3 sediment cores in the Mediterranean Sea spanning several centuries. Our results allow us to investigate the response of surface-dwelling planktic foraminifera to increases in atmospheric carbon dioxide. We find that increased anthropogenic carbon dioxide levels led to basin wide reductions in size normalized weights by modulating foraminiferal calcification. Carbon (δ13C) and boron (δ11B) isotopic compositions also indicate the increasing influence of fossil fuel derived carbon dioxide and decreasing pH, respectively. Alkenone concentrations and test accumulation rates indicate that warming and changes in biological productivity are insufficient to offset acidification effects. We suggest that further increases in atmospheric carbon dioxide will drive ongoing reductions in marine biogenic calcification in the Mediterranean Sea.

Nutrient management: as a panacea to improve the caryopsis quality and yield potential of durum wheat (Triticum turgidum L.) under the changing climatic conditions.

The increasing human population and the changing climate, which have given rise to frequent drought spells, pose a serious threat to global food security, while identification of high-yielding drought-tolerant genotypes coupled with nutrient management remains a proficient approach to cope with these challenges. An increase in seasonal temperature, recurring drought stress, and elevated atmospheric CO2 are alarmingly affecting durum wheat production, productivity, grain quality, and the human systems it supports. An increase in atmospheric carbon dioxide can improve wheat grain yield in a certain amount, but the right amount of nutrients, water, and other required conditions should be met to realize this benefit. Nutrients including nitrogen, silicon, and sulfur supply could alleviate the adverse effects of abiotic stress by enhancing antioxidant defense and improving nitrogen assimilation, although the effects on plant tolerance to drought stress varied with nitrogen ionic forms. The application of sewage sludge to durum wheat also positively impacts its drought stress tolerance by triggering high accumulation of osmoregulators, improving water retention capacity in the soil, and promoting root growth. These beneficial effect of nutrients contribute to durum wheat ability to withstand and recover from abiotic stress conditions, ultimately enhance its productivity and resilience. While these nutrients can provide benefits when applied in appropriate amounts, their excessive use can lead to adverse environmental consequences. Advanced technologies such as precision nutrient management, unmanned aerial vehicle-based spraying, and anaerobic digestion play significant roles in reducing the negative effects associated with nutrients like sewage sludge, zinc, nanoparticles and silicon fertilizers. Hence, nutrient management practices offer significant potential to enhance the caryopsis quality and yield potential of durum wheat. Through implementing tailored nutrient management strategies, farmers, breeders, and agronomists can contribute to sustainable durum wheat production, ensuring food security and maintaining the economic viability of the crop under the changing climatic conditions.

Energy-efficient storage of methane and carbon dioxide capture in the form of clathrate hydrates using a novel non-foaming surfactant: An experimental and computational investigation

In recent decades, both rising energy demand and increasing population have led to a significant increase in atmospheric carbon dioxide (CO2). Natural gas, the primary source of energy, and carbon capture and storage must therefore be managed efficiently. Gas hydrates have considerable potential for CO2 capture and energy storage since they can selectively absorb gas molecules and provide a large storage capacity. However, the slow kinetics of the hydrate formation constrained their commercial usage. Although surfactants have been investigated as effective additives to accelerate the rate of gas hydrate formation, intense foaming during the gas hydrate dissociation adversely affects the gas recovery factor. In this study, a novel anionic surfactant based on aconitic acid (ASA) was developed to improve the kinetics of methane and CO2 hydrates formation. The methane hydrate experiments indicated that, even at low concentrations, ASA significantly enhanced the kinetics of methane hydrate formation. The maximum water-to-hydrate conversion of 97 % and the highest storage capacity of 174 v/v were achieved using 50 ppm of ASA. Additionally, 99.1 v/v of storage capacity was achieved for CO2 hydrate in the solution containing 1000 ppm of ASA. Moreover, molecular dynamics simulation revealed that self-assembly behavior of ASA molecules increased the solubility of the gas molecules in the solution, provided more gas molecules for growing hydrate interface, and increased gas hydrate growth. Furthermore, no foam formation occurred in the ASA solution, even at high concentrations. These results show that ASA can be applied as an efficient and foamless gas hydrate promoter for methane storage and CO2 capture applications.

AI-based carbon emission forecast and mitigation framework using recycled concrete aggregates: A sustainable approach for the construction industry

<abstract> <p>The cement industry's carbon emissions present a major global challenge, particularly the increase in atmospheric carbon dioxide (CO<sub>2</sub>) levels. The concrete industry is responsible for a significant portion of these emissions, accounting for approximately 5–9% of the total emissions. This underscores the urgent need for effective strategies to curb carbon emissions. In this work, we propose to use artificial intelligence (AI) to predict future emission trends by performing a detailed analysis of cement industry's CO<sub>2</sub> emissions data. The AI predictive model shows a significant increase in overall carbon emissions from the cement sector which is attributed to population growth and increased demand for housing and infrastructure. To address this issue, we propose a framework that emphasizes on implementing carbon sequestration through reuse of construction and demolition (C & D) waste by using recycled aggregates. The paper proposes a framework addressing carbon sequestration through use of C & D waste. The framework is applied specifically to Maharashtra State in India to calculate the potential reduction in carbon emissions by construction industry resulting from recycled aggregates. The study reveals a projected saving of 24% in carbon emissions by adopting the suggested framework. The process and outcomes of the study aim to address the concerns of climate change through reduced carbon emissions in the construction industry promoting recycle and reuse of construction waste.</p> </abstract>

The differential ability of two species of seagrass to use carbon dioxide and bicarbonate and their modelled response to rising concentrations of inorganic carbon.

Seagrass meadows are one of the most productive ecosystems on the planet, but their photosynthesis rate may be limited by carbon dioxide but mitigated by exploiting the high concentration of bicarbonate in the ocean using different active processes. Seagrasses are declining worldwide at an accelerating rate because of numerous anthropogenic pressures. However, rising ocean concentrations of dissolved inorganic carbon, caused by increases in atmospheric carbon dioxide, may benefit seagrass photosynthesis. Here we compare the ability of two seagrass from the Mediterranean Sea, Posidonia oceanica (L.) Delile and Zostera marina L., to use carbon dioxide and bicarbonate at light saturation, and model how increasing concentrations of inorganic carbon affect their photosynthesis rate. pH-drift measurements confirmed that both species were able to use bicarbonate in addition to carbon dioxide, but that Z. marina was more effective than P. oceanica. Kinetic experiments showed that, compared to Z. marina, P. oceanica had a seven-fold higher affinity for carbon dioxide and a 1.6-fold higher affinity for bicarbonate. However, the maximal rate of bicarbonate uptake in Z. marina was 2.1-fold higher than in P. oceanica. In equilibrium with 410 ppm carbon dioxide in the atmosphere, the modelled rates of photosynthesis by Z. marina were slightly higher than P. oceanica, less carbon limited and depended on bicarbonate to a greater extent. This greater reliance by Z. marina is consistent with its less depleted 13C content compared to P. oceanica. Modelled photosynthesis suggests that both species would depend on bicarbonate alone at an atmospheric carbon dioxide partial pressure of 280 ppm. P. oceanica was projected to benefit more than Z. marina with increasing atmospheric carbon dioxide partial pressures, and at the highest carbon dioxide scenario of 1135 ppm, would have higher rates of photosynthesis and be more saturated by inorganic carbon than Z. marina. In both species, the proportional reliance on bicarbonate declined markedly as carbon dioxide concentrations increased and in P. oceanica carbon dioxide would become the major source of inorganic carbon.

Massive Natural Gas Hydrate Dissociation During the Penultimate Deglaciation (~130 ka) in the South China Sea

There is widespread and growing scientific interest in the impact of massive gas hydrate dissociation on the global environment and climate in geological history. Based on that a global negative excursion of carbon isotopic compositions in marine (foraminifera) and terrestrial (the organic carbon and calcite) sedimentary records occurred during the penultimate deglaciation (~130 ka), we believe that methane released by hydrate dissociation may play a role in accelerating the initial increase of atmospheric methane. In order to prove that massive natural gas hydrate dissociation occurred in this period, we aim to seek for evidence of gas hydrate dissociation from seep carbonate. Here, X-ray diffraction, carbon and oxygen isotopic compositions, trace elements, and U-Th dating analyses were conducted on the deeply-buried authigenic carbonate obtained by drilling in the northern continental slope of the South China Sea. Authigenic carbonate formed at ~130 ka showed obvious characteristics of negative excursion of carbon isotope, positive excursion of oxygen isotope, and enrichment of redox sensitive elements such as Mo, U and As. These results, in particular the high oxygen isotopic compositions of carbonate, point to massive gas hydrate dissociation in the northern continental slope of the South China Sea during the penultimate deglaciation. It is further speculated that massive gas hydrate dissociation might have also occurred on a global scale, contributing to the increase of atmospheric carbon dioxide and methane concentrations during the penultimate deglaciation, and may eventually cause global carbon isotope negative excursion.

Blue Carbon Ecosystems in Brazil: Overview and an Urgent Call for Conservation and Restoration

In this article, we discuss knowledge and gaps regarding blue carbon ecosystems (BCEs) in Brazil, considering the urgency to apply protection actions and policies to safeguard their biodiversity and associated ecosystem services. We also indicate areas of further research to improve carbon stocks and sequestration rate estimates. We call attention to the shortage of studies on Brazilian BCEs relative to the growing knowledge on the Blue Carbon Framework accumulated worldwide over the last decade. Considering the extensive Brazilian Economic Exclusive Zone (known as “Blue Amazon”), knowledge concerning blue carbon stocks is vital at regional and global scales for mitigating global increases in atmospheric carbon dioxide (CO2). The Blue Amazon has at least 1,100,000 ha of vegetated and non-vegetated coastal ecosystems (mangroves, salt marshes, seagrass meadows, and hypersaline tidal flats) that collectively contain vast amounts of stored carbon, making Brazil an ideal place to test mechanisms for evaluating, conserving, and restoring BCEs. Other poorly understood potential sinks and sources of carbon are macroalgal and rhodolith beds, mudflats, continental shelf sediments, and marine animal forests in shallow, mesophotic, and deep waters. The carbon fluxes between diverse environmental compartments, such as soil–air, soil–water, groundwater–water–surface water, air–water, and land–ocean, in BCEs across the Blue Amazon must be studied. We emphasize the importance of assessing the total carbon stock and the recent dismantling of environmental laws that pose great risks to these important BCEs. The conservation and recovery of these areas would enhance the carbon sequestration capacity of the entire country. Furthermore, we highlight priorities to improve knowledge concerning BCEs and their biogeochemical cycles in the Blue Amazon and to provide information to assist in the reduction of atmospheric levels of CO2 for the United Nations Decade of Ocean Science (2021–2030).

COASTAL OCEAN ACIDIFICATION IN BRAZIL: A BRIEF OVERVIEW AND PERSPECTIVES

This perspective paper aims at presenting the current knowledge on the processes of ocean acidification (OA) and coastal acidification (CA) in the Brazilian coastal ocean. We define and differentiate the processes of OA and CA: the first driven by the actual global increase of atmospheric carbon dioxide (CO2); the second driven by a combination of ocean uptake of atmospheric CO2 and other local/regional chemical additions or subtractions in aquatic ecosystems at the land-ocean interface. Regarding OA, we have centered our analysis on the data available for the main water masses along the Brazilian coast: South Atlantic Central Water (SACW), Tropical Water (TW), and Coastal Water (CW). The few data available for the shallow coastal waters (< 200 m depth) of the continental shelf reveal an increase in the anthropogenic component of the total dissolved inorganic carbon (DIC) pool in the SACW, with a decline in the ocean pH (over two decades; 1993-2013), and in the saturation state of calcium carbonate (CaCO3) minerals. We could not find OA trends for TW and CW because no data was available. Overall, the colder water masses (SACW, Plata Plume) have lower buffering capacity and simulations show that will potentially experience earlier negative OA impacts than the warmer waters masses (TW, Amazon Plume). Regarding CA, we have identified some local/regional studies investigating the carbonate chemistry in nearshore/estuarine ecosystems, particularly on the quantification of sources and sinks of CO2 , and determining short-term variabilities. Apparently, spreading coastal eutrophication in Brazil can enhances or reduces the process of OA, depending on the net ecosystem metabolism in combination with other chemical alterations. However, we could not find medium-long term acidification trends due to the limited data. There is a limited capacity to produce long time-series of carbonate chemistry parameters in key ecosystems and regions along the Brazilian coast. This lack of past information hinders and impairs the scientific community for identifying potential patterns of acidification along the Brazilian coast. We call for an urgent action in Brazil, with emphasis on the establishment of moored buoys/stations and/or scientific programs in the long term with continuous, real-time measurements of the main carbonate chemistry parameters.
 Keywords: ocean acidification, coastal acidification, coastal eutrophication, continental shelf, Southwestern Atlantic Ocean

Terrestrial carbon sinks in China and around the world and their contribution to carbon neutrality

<p indent="0mm">Enhancing the terrestrial ecosystem carbon sink (referred to as terrestrial C sink) is an important way to slow down the continuous increase in atmospheric carbon dioxide (CO₂) concentration and to achieve carbon neutrality target. To better understand the characteristics of terrestrial C sinks and their contribution to carbon neutrality, this review summarizes major progress in terrestrial C budget researches during the past decades, clarifies spatial patterns and drivers of terrestrial C sources and sinks in China and around the world, and examines the role of terrestrial C sinks in achieving carbon neutrality target. According to recent studies, the global terrestrial C sink has been increasing from a source of (−0.2±0.9) Pg C yr⁻¹ (1 Pg=<sc>10¹⁵ g)</sc> in the 1960s to a sink of (1.9±1.1) Pg C yr⁻¹ in the 2010s. By synthesizing the published data, we estimate terrestrial C sink of 0.20–0.25 Pg C yr⁻¹ in China during the past decades, and predicted it to be 0.15–0.52 Pg C yr⁻¹ by 2060. The terrestrial C sinks are mainly located in the mid- and high latitudes of the Northern Hemisphere, while tropical regions act as a weak C sink or source. The C balance differs much among ecosystem types: forest is the major C sink; shrubland, wetland and farmland soil act as C sinks; and whether the grassland functions as C sink or source remains unclear. Desert might be a C sink, but the magnitude and the associated mechanisms are still controversial. Elevated atmospheric CO₂ concentration, nitrogen deposition, climate change, and land cover change are the main drivers of terrestrial C sinks, while other factors such as fires and aerosols would also affect ecosystem C balance. The driving factors of terrestrial C sink differ among regions. Elevated CO₂ concentration and climate change are major drivers of the C sinks in North America and Europe, while afforestation and ecological restoration are additionally important forcing factors of terrestrial C sinks in China. For future studies, we recommend the necessity for intensive and long-term ecosystem C monitoring over broad geographic scale to improve terrestrial biosphere models for accurately evaluating terrestrial C budget and its dynamics under various climate change and policy scenarios.

Spatiotemporal variations of carbon dioxide (CO2) at Urban neighborhood scale: Characterization of distribution patterns and contributions of emission sources

• Spatiotemporal distributions were analyzed for urban CO 2 concentration via field study. • CO 2 in urban neighborhoods exhibited notable daily and seasonal variations. • The CO 2 showed a gradual decrease in roadside, residential, and green space areas. • Random Forest and eXtreme Gradient Boosting were used for source contribution analysis. • Traffic source had the largest contribution to the CO 2 followed by green space. The gradual increase in atmospheric carbon dioxide (CO 2 ) concentrations has attracted worldwide attention for its strong relationships with global climate change. Considerable efforts are being undertaken to characterize spatiotemporal variations of CO 2 at a city, regional and national level, aiming at providing pipelines for carbon emission reduction. However, there is scarce knowledge of how CO 2 at the urban neighborhood scale is produced and distributed in the context of time and space, which is useful to accurately target source contributions from the ground up and reduce carbon emissions at a fine-grained scale. In this study, mobile measurements of CO 2 concentrations were made in a 2 km × 2 km urban area covering different land use types to separately characterize the spatiotemporal distribution patterns of CO 2 in roadside, residential and green space areas. The results show that CO 2 concentrations in the late afternoon (Local time, UTC+8, LT 17–18) were higher than those at noon (LT 11–12), and that CO 2 concentrations in winter were higher than those in summer. The roadside areas exhibited the highest CO 2 concentration level of 452.66 ± 20.59 ppm, followed by residential areas (436.34 ± 27.02 ppm) and green space areas (428.98 ± 20.49 ppm). The result indicates that traffic sources brought more carbon emissions and contributed to a significant increase in CO 2 concentrations, while urban greenery caused more carbon absorptions and reduced CO 2 concentrations. This can be further confirmed by the observations that CO 2 concentrations in the roadside neighborhood showed a strong positive correlation (R 2 = 0.86) with ambient traffic flow. Then two machine learning models, i.e., Random Forest and eXtreme Gradient Boost, were developed to quantify the individual contribution from different carbon emission sources to the CO 2 distributions, including traffic flow, greening rate, and domestic energy consumption. The results show that traffic-related carbon emissions were the most important influencing factor and accounted for approximately 60% of ambient CO 2 concentrations, followed by greening rate (20%) and domestic energy consumption (10%). These findings can provide insights into spatiotemporal distributions and source contributions of CO 2 in urban neighborhoods and show huge potentials for reducing urban carbon emissions at a fine-grained scale.

Terrestrial carbon sinks in China and around the world and their contribution to carbon neutrality.

Enhancing the terrestrial ecosystem carbon sink (referred to as terrestrial C sink) is an important way to slow down the continuous increase in atmospheric carbon dioxide (CO2) concentration and to achieve carbon neutrality target. To better understand the characteristics of terrestrial C sinks and their contribution to carbon neutrality, this review summarizes major progress in terrestrial C budget researches during the past decades, clarifies spatial patterns and drivers of terrestrial C sources and sinks in China and around the world, and examines the role of terrestrial C sinks in achieving carbon neutrality target. According to recent studies, the global terrestrial C sink has been increasing from a source of (-0.2±0.9) Pg C yr-1 (1 Pg=1015 g) in the 1960s to a sink of (1.9±1.1) Pg C yr-1 in the 2010s. By synthesizing the published data, we estimate terrestrial C sink of 0.20-0.25 Pg C yr-1 in China during the past decades, and predict it to be 0.15-0.52 Pg C yr-1 by 2060. The terrestrial C sinks are mainly located in the mid- and high latitudes of the Northern Hemisphere, while tropical regions act as a weak C sink or source. The C balance differs much among ecosystem types: forest is the major C sink; shrubland, wetland and farmland soil act as C sinks; and whether the grassland functions as C sink or source remains unclear. Desert might be a C sink, but the magnitude and the associated mechanisms are still controversial. Elevated atmospheric CO2 concentration, nitrogen deposition, climate change, and land cover change are the main drivers of terrestrial C sinks, while other factors such as fires and aerosols would also affect ecosystem C balance. The driving factors of terrestrial C sink differ among regions. Elevated CO2 concentration and climate change are major drivers of the C sinks in North America and Europe, while afforestation and ecological restoration are additionally important forcing factors of terrestrial C sinks in China. For future studies, we recommend the necessity for intensive and long term ecosystem C monitoring over broad geographic scale to improve terrestrial biosphere models for accurately evaluating terrestrial C budget and its dynamics under various climate change and policy scenarios.

Carbon sequestration potential and CO2 fluxes in a tropical forest ecosystem

Carbon (C) is a key product of forests, but not widely studied for available C stock, and biomass of tree species in typical forest ecosystems of India. Therefore, it is useful to estimate C stock at national and regional levels for establishing forest-based policies and developing roadmap for long-term plans and strategies to reduce the rate of increase of atmospheric carbon dioxide (CO2). Hence, present investigation was conducted to assess C storage and CO2 fluxes in tropical dry deciduous forest ecosystems of Jhumpa and Kairu in the southern Haryana, India. The C stock of trees in above ground biomass (AGB) was calculated by assuming the C content at 50% of the total biomass. Concentration of C in composite samples of shoots and roots of shrubs and herbs was estimated by the ash method. Soil C storage was determined on the basis of C concentration and soil bulk density up to 60 cm depth. The AGB of trees ranged from 33.1 to 75.8 Mg ha−1; the belowground biomass from 9.0 to 18.5 Mg ha−1 and total plant C storage from 24.3 to 53.9 Mg C ha−1. The total biomass of shrubs was 16.2 Mg ha−1 for the Salvadora oleoides forest at Jhumpa compared with 8.4 Mg ha−1 for the Acacia senegal-Acacia tortilis forest at Kairu. Net primary productivity of various components of trees in these forest ecosystems ranged from 8.1 to 9.6 Mg ha−1 y−1 and net flux of C from 4.6 to 5.8 Mg C ha−1 y−1. The annual litter fall in two forest ecosystems ranged from 3356 to 4498 Kg ha−1. S. oleoides contributed 50.0% and 47.3% towards the above ground and below ground C pools corresponding to the 17.9 Mg C ha−1and 4.1 Mg C ha−1, respectively. S. oleoides played a dominant role in biomass production and C assimilation in S. oleoides-A. tortilis forest at Jhumpa, while Prosopis juliflora and A. senegal were the highest contributors in A. senegal-A. tortilis forest at Kairu because of a high girth class and high density of trees, respectively. The cumulative soil organic carbon (SOC) stock up to 60 cm depth was more in A. senegal-A. tortilis forest at Kairu (16.3 Mg C ha−1) than that in the SO-AT forest at Jhumpa (12.9 Mg C ha−1). The results of this study revealed that S. oleoides and P. juliflora are key species as they sequester more C under a range of disturbances. Carbon sequestration potential of the studied forest ecosystems was 3.55 to 4.35 Mg C ha−1 y−1 which indicates a high C sequestration potential of these ecosystems.