High Levels Of Carbon Dioxide Research Articles

Assessing biological soil crusts as agents of Ca–Mg silicate dissolution and CO2 sequestration

ABSTRACT Biological soil crusts (BSCs) monitored over a 25-year period enhance the dissolution of the Ca-silicate plagioclase and the Mg-silicate olivine at Sonoran Desert and Colorado Plateau, USA, study sites. This first measured biological enhancement of weathering (BEW) for plagioclase is a mean of 2.3±0.4 and 3.0±0.4 for the Organic Pipe, Arizona and Moab, Utah study sites; and it is 4.9±0.8 and 3.9±0.3 for olivine at these respective sites. These BEWs are low compared to other biological agents such as lichens, tree roots, termites and especially ants. If these modern BEW for BCSs reflect the magnitude of BEW in Archean soil crusts, then the presence of abundant BSCs covering an Archean Earth surface would not contradict available evidence for no substantial atmospheric CO2 decline in Earth’s early atmosphere. The relatively low BEW value for BCSs indicates that BSCs would not be a useful geoengineering solution to high levels of atmospheric carbon dioxide.

Elevated extracellular CO<sub>2</sub> level affects the adaptive transcriptional response and survival of human peripheral blood mononuclear cells toward hypoxia and oxidative stress

BACKGROUND High carbon dioxide (CO2) level from indoor environments, such as classrooms and offices, might cause sick building syndrome. Excessive indoor CO2 level increases CO2 level in the blood, and over-accumulation of CO2 induces an adaptive response that requires modulation of gene expression. This study aimed to investigate the adaptive transcriptional response toward hypoxia and oxidative stress in human peripheral blood mononuclear cells (PBMCs) exposed to elevated CO2 level in vitro and its association with cell viability.
 METHODS PBMCs were treated in 5% CO2 and 15% CO2, representatives a high CO₂ level condition for 24 and 48 hours. Extracellular pH (pHe) was measured with a pH meter. The levels of reactive oxygen species were determined by measuring superoxide and hydrogen peroxide with dihydroethidium and dichlorofluorescin-diacetate assay. The mRNA expression levels of hypoxia-inducible factor (HIF)-1α, HIF-2α, nuclear factor (NF)-κB, and manganese superoxide dismutase (MnSOD) were analyzed using a real-time reverse transcriptase-polymerase chain reaction (qRT-PCR). Cell survival was determined by measuring cell viability.
 RESULTS pHe increased in 24 hours after 15% CO₂ treatment, and then decreased in 48 hours. Superoxide and hydrogen peroxide levels increased after the 24- and 48-hour of high CO₂ level condition. The expression levels of NF-κB, MnSOD, HIF-1α, and HIF-2α decreased in 24 hours and increased in 48 hours. The increased antioxidant mRNA expression in 48 hours showed that the PBMCs were responsive under high CO2 conditions. Elevated CO2 suppressed cell viability significantly in 48 hours.
 CONCLUSIONS After 48 hours of high CO₂ level condition, PBMCs showed an upregulation in genes related to hypoxia and oxidative stress to overcome the effects of CO2 elevation.

Influence of Industrial and Agricultural by-Products as Cementitious Blends in Self-Compacting Concrete – A Review

Globally, the annual generation of industrial and agricultural by-products is exceeding a thousand million tons and forecasted to tremendously inflate in the future. The by-products are usually either landfilled or incinerated causing environmental impacts. Many waste products are effectively utilized in the development of eco-friendly concrete. This study targets the adoption of generated by-products as an alternative to cement in the production of self-compacting concrete (SCC) based on the existing literature. SCC is majorly composed of high cement content, aggregates, chemical admixtures, and water. On the other hand, the cement production emits high levels of carbon dioxide causing environmental hazards and could be reduced to a certain extent by implementing these by-products as cement blends. The by-products are examined for its suitability by the material characterization, physical and chemical properties to match the pozzolanic behavior. This paper reviews comprehensively on the effect of utilizing industrial and agricultural by-products on the workability, strength, permeability, and microstructural performance when blended with SCC. This study summarizes the advantages of utilizing by-products towards the production methodology of a more sustainable and environmentally friendly SCC.

A review of hydrogen production from anaerobic digestion

Recent advances in the utilization of hydrogen as an alternative fuel source to conventional fossil fuels have led to a search for a renewable process of producing hydrogen. Most hydrogen today is produced from hydrocarbons in a process that also releases high levels of carbon dioxide and carbon monoxide, two established greenhouse gasses; because of this harmful means of production, research has been directed toward using anaerobic digestion to produce useful levels of hydrogen gas. Anaerobic systems have been shown to produce a biogas that is easily used in producing energy, but certain processes can be performed to further enhance the concentrations of hydrogen. These processes include the inhibition of microorganisms that lower hydrogen concentrations and the constant removal of hydrogen to promote hydrogen-producing bacteria. Experimental designs and large-scale applications have shown this process to be environmentally viable with limited, but promising, economic potential. With a constant increase for the need of hydrogen gas, the sustainable production of hydrogen is becoming more important. This review explores some of the recent research on this topic and explores the processes behind using anaerobic digestion for hydrogen production.

Venous blood gas analysis in patients with COVID-19 symptoms in the early assessment of virus positivity

Abstract Objectives Coronavirus disease 2019 (COVID-19) is currently a worldwide major health threat. Recognizing hypoxia in patients early on can have a considerable effect on therapy success and survival rate. Methods We collected data using a standard blood gas analyzer from 50 patients and analyzed measurements of partial pressure of carbon dioxide-pCO2, partial pressure of oxygen-pO2 and oxygen saturation-sO2, bicarbonate concentrations-HCO3− as well as ionized calcium concentrations. We further examined PCR test results for SARS-CoV-2 of the patients and analyzed differences between patients tested positive and those tested negative for the virus. Results Venous pCO2 was significantly higher whereas pO2 and sO2 were significantly lower in patients who tested positive for SARS-CoV-2. The pH, and ionized calcium concentrations of patients tested positive for the virus were significantly lower than in those tested negative. Conclusions Symptomatic SARS-CoV-2-positive patients upon admission to the emergency room exhibit lower venous blood levels of oxygen, pH, and calcium and higher levels of carbon dioxide compared to symptomatic SARS-CoV-2-negative patients. This blood gas analysis constellation could help in identifying SARS-CoV-2-positive patients more rapidly and identifying early signs of hypoxia.

Human responses to high levels of carbon dioxide and air temperature.

In this study, 30 subjects were exposed to different combinations of air temperature (Ta : 24, 27, and 30°C) and CO2 level (8000, 10000, and 12000ppm) in a high-humidity (RH: 85%) underground climate chamber. Subjective assessments, physiological responses, and cognitive performance were investigated. The results showed that as compared with exposure to Ta =24°C, exposure to 30°C at all CO2 levels caused subjects to feel uncomfortably warm and experience stronger odor intensity, while increased mental effort and greater intensity of acute health symptoms were reported. However, no significant effects of Ta on task performance or physiological responses were found. This indicated that subjects had to exert more effort to maintain their performance in an uncomfortably warm environment. Increasing CO2 from 8000 to 12000ppm at all Ta caused subjects to report higher rates of headache, fatigue, agitation, and feeling depressed, although the results were statistically significant only at 24 and 27°C. The text typing performance and systolic blood pressure (SBP) decreased significantly at this exposure, whereas diastolic blood pressure (DBP) and thermal discomfort increased significantly. These effects suggest higher arousal/stress. No significant interaction effect of Ta and CO2 concentration on human responses was identified.

Recovery of viscous and heavy oil by CO2-saturated brine

Fast economic growth in Oman coupled with its climatic conditions have led to an energy-intensive lifestyle that has resulted in high levels of carbon dioxide (CO2) emissions. The injection of CO2 produced by cement plants into oil reservoirs combined with carbon capture is seen as an option to reduce CO2 in the air in order to curb climate change. The potential of CO2-saturated brine to recover oil is investigated using two samples of viscous oil (13 and 21 cP) and one sample of heavy oil (1471 cP) from Oman in water flooding experiments followed by CO2-saturated brine injection at 25 °C and 3.45 MPa. CO2 solubility in oil and brine, changes of their viscosity and density, oil swelling and other parameters are investigated.Irrespective of early water breakthrough, the greatest incremental recovery of 25.6% after injection of CO2-saturated brine through oil saturated core is obtained for heavy oil, as compared to 8.2% and 15% for viscous oils. Higher recovery from heavy oil sample is explained by the greater viscosity reduction in addition to the density reduction of CO2-saturated oil that is similar for all three types of oil of about 50% on average. The greatest reduction of oil viscosity of 87% is obtained for the heavy oil and 59% on average for viscous oil samples. Thus, different mechanisms contribute more into the oil recovery: density reduction due to oil swelling for viscose oil and viscosity reduction for heavy oil.The injection of CO2-saturated brine demonstrates a great potential in addressing both issues, curbing of climate change and energy supply by enhanced recovery of viscous and heavy oil.

Experimental investigation of the effects of low-temperature phase change material on single-slope solar still

Conventional desalination plants mostly require high energy levels, which could produce high levels of carbon dioxide, if provided by fossil fuels. While this energy could be efficiently provided by solar energy, this energy's intermittent nature is an excellent barrier to this approach. Incorporating phase change materials (PCM) in desalination units could help achieve a more prolonged desalination process. In this experimental study, a PCM-enhanced single-slope solar still is investigated regarding the effect of low-temperature PCM on the overall productivity and efficiency and basin temperature parameters. For this purpose, a commercial salt hydrate low-temperature PCM with the melting point of 28 °C and latent heat of fusion of 225 kJ/kg was selected as a novel approach in this field. Three test cases, including still without PCM, still with 3 kg of PCM, and still with 6 kg of PCM were investigated. During each experiment, the operational temperature, hourly and cumulative productivities, and desalination efficiency were measured and calculated. It was found that adding 6 kg of PCM could enhance the overall productivity by 30.3% while increasing the desalination efficiency from 28.13% to 36.42%. The results show that low-temperature PCMs could be efficiently utilized to improve the solar stills' performance.

Stomatal conductance influences interannual variability and long-term changes in regional cumulative plant uptake of ozone

Ambient ozone uptake by plant stomata degrades ecosystem and crop health and alters local-to-global carbon and water cycling. Metrics for ozone plant damage are often based solely on ambient ozone concentrations, overlooking the role of variations in stomatal activity. A better metric is the cumulative stomatal uptake of ozone (CUO), which indicates the amount of ozone entering the leaf over time available to cause physiological damage. Here we apply the NOAA GFDL global earth system model to assess the importance of capturing interannual variations and 21st century changes in surface ozone versus stomatal conductance for regional mean CUO using 20-year time-slice simulations at the 2010s and 2090s for a high-warming climate and emissions scenario. The GFDL model includes chemistry-climate interactions and couples atmospheric and land components through not only carbon, water, and energy exchanges, but also reactive trace gases—in particular, ozone dry deposition simulated by the land influences surface ozone concentrations. Our 20-year time slice simulations hold anthropogenic precursor emissions, well-mixed greenhouse gases, and land use distributions fixed at either 2010 or 2090 values. We find that CUO responds much more strongly to interannual and daily variability in stomatal conductance than in ozone. On the other hand, long-term changes in ozone explain 44%–90% of the annual CUO change in regions with decreases, largely driven by the impact of 21st century anthropogenic NOx emission trends on summer surface ozone. In some regions, increases in stomatal conductance from the 2010s to 2090s counteract the influence of lower ozone on CUO. We also find that summertime stomatal closure under high carbon dioxide levels can offset the impacts of higher springtime leaf area (e.g. earlier leaf out) and associated stomatal conductance on CUO. Our findings underscore the importance of considering plant physiology in assessing ozone vegetation damage, particularly in quantifying year-to-year changes.

Facile synthesis of cubic cuprous oxide for electrochemical reduction of carbon dioxide

High level of atmospheric carbon dioxide (CO2) concentration is considered one of the main causes of global warming. Electrochemical conversion of CO2 into valuable chemicals and fuels has promising potential to be implemented into practical and sustainable devices. In order to efficiently realize this strategy, one of the biggest efforts has been focused on the design of catalysts which are inexpensive, active and selective and can be produced through green and up-scalable routes. In this work, copper-based materials are simply synthesized via microwave-assisted process and carefully characterized by physical/chemical/electrochemical techniques. Nanoparticle with a cupric oxide (CuO) surface as well as various cuprous oxide (Cu2O) cubes with different sizes is obtained and used for the CO2 reduction reaction. It is observed that the Cu2O-derived electrodes show enhanced activity and carbon monoxide (CO) selectivity compared to the CuO-derived one. Among various Cu2O catalysts, the one with the smallest cubes leads to the best CO selectivity of the electrode, attributed to a higher electrochemically active surface area. Under applied potentials, all Cu2O cubes undergo structural and morphological modification, even though the cubic shape is retained. The nanoclusters formed during the material evolution offer abundant and active reaction sites, leading to the high performance of the Cu2O-derived electrodes.Graphic abstract

Evaluation of Mechanical and Environmental Properties of Engineered Alkali-Activated Green Mortar.

Currently, alkali-activated binders using industrial wastes are considered an environmentally friendly alternative to ordinary Portland cement (OPC), which contributes to addressing the high levels of carbon dioxide (CO2) emissions and enlarging embodied energy (EE). Concretes produced from industrial wastes have shown promising environmentally-friendly features with appropriate strength and durability. From this perspective, the compressive strength (CS), CO2 emissions, and EE of four industrial powder waste materials, including fly ash (FA), palm oil fly ash (POFA), waste ceramic powder (WCP), and granulated blast-furnace slag (GBFS), were investigated as replacements for OPC. Forty-two engineered alkali-activated mix (AAM) designs with different percentages of the above-mentioned waste materials were experimentally investigated to evaluate the effect of each binder mass percentage on 28-day CS. Additionally, the effects of each industrial powder waste material on SiO2, CaO, and Al2O3 contents were investigated. The results confirm that adding FA to the samples caused a reduction of less than 26% in CS, whereas the replacement of GBFS by different levels of POFA significantly affected the compressive strength of specimens. The results also show that the AAM designs with a high volume FA provided the lowest EE and CO2 emission levels compared to other mix designs. Empirical equations were also proposed to estimate the CS, CO2 emissions, and EE of AAM designs according to their binder mass compositions.

Administration of sodium bicarbonate during cardiopulmonary resuscitation increases the frequency of cardiac gas on postmortem CT estimated to be CO2

• Hypercapnia increases the frequency of cardiac gas (CG) on postmortem CT (PMCT). • CG on PMCT was frequently found in the sodium bicarbonate (SB) administration group. • Administraton of SB may generate extra carbon dioxide during resuscitation. Cardiac gas (CG) on immediate postmortem computed tomography (PMCT) after cardiopulmonary resuscitation (CPR) is associated with high blood carbon dioxide (CO 2 ) levels. This study investigated whether administration of sodium bicarbonate (SB) during CPR generates extra blood CO 2 , judging from CG findings on immediate PMCT. We enrolled 210 nontraumatic cardiopulmonary arrest (CPA) patients (101 men, 109 women) who were transported to our hospital and could not be resuscitated. They underwent arterial blood gas analysis (BGA) during CPR and immediate PMCT after failed resuscitation and were assigned to a CG-negative or a CG-positive group based on the PMCT findings. CG on immediate PMCT was detected in 106 patients (50.4%). Significant differences were not observed in the demographic variables between the CG-negative and CGpositive groups. Both pH and the partial pressure of arterial oxygen were significantly lower in the CG-positive group than in the CG-negative group, and the partial pressure of arterial carbon dioxide was significantly higher in the CG-positive group than in the CG-negative group. Among the administered infusions and medications, only SB demonstrated a significant difference in the frequency of administration between the CG-negative and CG-positive groups. The positive CG rate in the SB group (44/67, 66%) was significantly higher than that in the non-SB group (62/143, 43%). The administration of SB during CPR was associated with an increased frequency of CG on immediate PMCT, suggesting that administration of SB during CPR generates extra blood CO 2 .

A Fiber Bragg Grating (FBG)-Based Sensor System for Anaerobic Biodigester Humidity Monitoring

An operational, Fiber Bragg Grating (FBG)-based sensing system, specifically designed to monitor conditions in a harsh industrial environment is reported. The sensors used were placed inside tanks with high levels of methane (CH4), carbon dioxide (CO2) and hydrogen sulphide (H2S) gases and high relative humidity in the North Head sewage treatment plant in Sydney, Australia. The sensor system was developed primarily to monitor the effect of >98% relative humidity and temperature changes on the corrosion rates of various materials inside the tanks. Data have been obtained from the use of the system for eight months: these have been correlated with key climate data including the changing weather conditions experienced during the continued monitoring activity. The sensor system specifically developed has been shown to be sufficiently robust to work well, and safely, in such a harsh environment (due to the gaseous H2S and CH4 present) with no signs of deterioration of the sensors or of the signals obtained from the system. The remote operation through flexible data transmission has allowed continuous and up-to-date monitoring of the conditions inside the tanks.

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.

High CO2 Levels Impair Lung Wound Healing.

Delayed lung repair leads to alveolopleural fistulae, which are a major cause of morbidity after lung resections. We have reported that intrapleural hypercapnia is associated with delayed lung repair after lung resection. Here, we provide new evidence that hypercapnia delays wound closure of both large airway and alveolar epithelial cell monolayers because of inhibition of epithelial cell migration. Cell migration and airway epithelial wound closure were dependent on Rac1-GTPase activation, which was suppressed by hypercapnia directly through the upregulation of AMP kinase and indirectly through inhibition of injury-induced NF-κB-mediated CXCL12 (pleural CXC motif chemokine 12) release, respectively. Both these pathways were independently suppressed, because dominant negative AMP kinase rescued the effects of hypercapnia on Rac1-GTPase in uninjured resting cells, whereas proteasomal inhibition reversed the NF-κB-mediated CXCL12 release during injury. Constitutive overexpression of Rac1-GTPase rescued the effects of hypercapnia on both pathways as well as on wound healing. Similarly, exogenous recombinant CXCL12 reversed the effects of hypercapnia through Rac1-GTPase activation by its receptor, CXCR4. Moreover, CXCL12 transgenic murine recipients of orthotopic tracheal transplantation were protected from hypercapnia-induced inhibition of tracheal epithelial cell migration and wound repair. In patients undergoing lobectomy, we found inverse correlation between intrapleural carbon dioxide and pleural CXCL12 levels as well as between CXCL12 levels and alveolopleural leak. Accordingly, we provide first evidence that high carbon dioxide levels impair lung repair by inhibiting epithelial cell migration through two distinct pathways, which can be restored by recombinant CXCL12.

Why carbon dioxide makes stellarators so important

The increasing level of atmospheric carbon dioxide has driven public discourse throughout the world. An immediate implementation of carbon-free energy sources is demanded with little discussion of costs, technical constraints on the sources, or implications of high residual levels of carbon dioxide. Residual carbon-dioxide can be removed from the air, but the cost to remove the carbon-dioxide produced by human activity during a year is thought to be trillions of dollars—otherwise it remains in the atmosphere for centuries. Economic considerations may limit wind and solar sources to less than 40% of the electricity production. Fission or fusion may be the only choice for most of the rest. Development costs are orders of magnitude smaller than implementation costs, which are tens of trillions of dollars for fission. A needless delay in the development of fusion has enormous financial implications. As will be shown, stellarators are better positioned than any other concept for a fast path to fusion. A computationally derived conceptual design for a stellarator reactor may allow final design and construction to be initiated without the delay of intermediate generations of experiments. The most urgent issue is the development of conceptual designs.

Temperate rainforests near the South Pole during peak Cretaceous warmth.

The mid-Cretaceous period was one of the warmest intervals of the past 140millionyears1-5, driven by atmospheric carbon dioxide levels of around 1,000parts per million by volume6. In the near absence of proximal geological records from south of the Antarctic Circle, it is disputed whether polar ice could exist under such environmental conditions. Here we use a sedimentary sequence recovered from the West Antarctic shelf-the southernmost Cretaceous record reported so far-and show that a temperate lowland rainforest environment existed at a palaeolatitude of about 82°S during the Turonian-Santonian age (92 to 83millionyearsago). This record contains an intact 3-metre-long network of in situ fossil roots embedded in a mudstone matrix containing diverse pollen and spores. A climate model simulation shows that the reconstructed temperate climate at this high latitude requires a combination of both atmospheric carbon dioxide concentrations of 1,120-1,680parts per million by volume and a vegetated land surface without major Antarctic glaciation, highlighting the important cooling effect exerted by ice albedo under high levels of atmospheric carbon dioxide.

In-vehicle carbon dioxide and adverse effects: An air filtration-based intervention study

Drowsiness is considered a potential risk for traffic accidents. Exposure to high carbon dioxide (CO2) levels in vehicles may result in unpleasant feeling, fatigue, drowsiness or lethargy among drivers and passengers. However, little is known about whether reducing CO2 levels in vehicles by air filtration can relieve adverse effects among human subjects during driving. We recruited a panel of 84 healthy participants to drive a vehicle equipped with a CO2 filtration system for 1 h on a coastal road in a Northern Taiwan rural area. The operation modes of the CO2 filtration system, including fresh air from open windows without a CO2 filtration system (Control-mode), fresh air from an air conditioning (AC) system with closed windows and a false CO2 filtration system in operation (Off-mode) or a true CO2 filtration system in operation (On-mode), were examined. The repeated measurements of heart rate (HR), blood pressure (BP), CO2, total volatile organic compounds (TVOCs), particulate matter ≤2.5 μm in aerodynamic diameter (PM2.5) and a simple question about drowsiness were obtained for each participant in three different modes. We found that decreased HR, systolic BP (SBP) and diastolic BP (DBP) and increased drowsiness were associated with increased levels of in-vehicle CO2. The effects of in-vehicle CO2 on adverse effects were highest in the Off-mode during driving. In the On-mode, the participants showed slight decreases in HR, SBP and DBP and slight increases in drowsiness. We concluded that the utilization of a CO2 filtration system can reduce in-vehicle CO2 levels and modify the effect of in-vehicle CO2 on HR, BP and drowsiness among human subjects during driving.

Defects in nanosilica catalytically convert CO2 to methane without any metal and ligand

Active and stable metal-free heterogeneous catalysts for CO2 fixation are required to reduce the current high level of carbon dioxide in the atmosphere, which is driving climate change. In this work, we show that defects in nanosilica (E' centers, oxygen vacancies, and nonbridging oxygen hole centers) convert CO2 to methane with excellent productivity and selectivity. Neither metal nor complex organic ligands were required, and the defect alone acted as catalytic sites for carbon dioxide activation and hydrogen dissociation and their cooperative action converted CO2 to methane. Unlike metal catalysts, which become deactivated with time, the defect-containing nanosilica showed significantly better stability. Notably, the catalyst can be regenerated by simple heating in the air without the need for hydrogen gas. Surprisingly, the catalytic activity for methane production increased significantly after every regeneration cycle, reaching more than double the methane production rate after eight regeneration cycles. This activated catalyst remained stable for more than 200 h. Detailed understanding of the role of the various defect sites in terms of their concentrations and proximities as well as their cooperativity in activating CO2 and dissociating hydrogen to produce methane was achieved.

Anthropogenic global shifts in biospheric N and P concentrations and ratios and their impacts on biodiversity, ecosystem productivity, food security, and human health.

The availability of carbon (C) from high levels of atmospheric carbon dioxide (CO2 ) and anthropogenic release of nitrogen (N) is increasing, but these increases are not paralleled by increases in levels of phosphorus (P). The current unstoppable changes in the stoichiometries of C and N relative to P have no historical precedent. We describe changes in P and N fluxes over the last five decades that have led to asymmetrical increases in P and N inputs to the biosphere. We identified widespread and rapid changes in N:P ratios in air, soil, water, and organisms and important consequences to the structure, function, and biodiversity of ecosystems. A mass-balance approach found that the combined limited availability of P and N was likely to reduce C storage by natural ecosystems during the remainder of the 21st Century, and projected crop yields of the Millennium Ecosystem Assessment indicated an increase in nutrient deficiency in developing regions if access to P fertilizer is limited. Imbalances of the N:P ratio would likely negatively affect human health, food security, and global economic and geopolitical stability, with feedbacks and synergistic effects on drivers of global environmental change, such as increasing levels of CO2 , climatic warming, and increasing pollution. We summarize potential solutions for avoiding the negative impacts of global imbalances of N:P ratios on the environment, biodiversity, climate change, food security, and human health.