Search Results (1,392)

Catalytic oxidation is one of the most effective technologies for controlling atmospheric pollutants like carbon monoxide (CO), volatile organic compounds (VOCs), and diesel soot. Catalyst performance is governed by the interplay between reaction mechanisms, physicochemical properties, and catalyst architecture. This review provides a comprehensive overview of the fundamental oxidation pathways, including Langmuir–Hinshelwood, Eley–Rideal, and Mars–van Krevelen mechanisms, highlighting their relationship with oxygen mobility, oxygen vacancies, redox behavior, and metal–support interactions. The catalytic roles of noble metals and transition metal oxides are comparatively discussed, with emphasis on the contribution of lattice oxygen and defect chemistry to oxidation activity. The review also examines recent advances in structured catalysts designed to improve heat and mass transfer, catalyst accessibility, and practical reactor performance. Particular attention is given to biomorphic fibers, electrospun nanofibers, catalytic ceramic papers, conventional monoliths, and additively manufactured (3D-printed) monolithic structures as emerging platforms for environmental catalysis. Unlike previous reviews focused primarily on catalyst composition or individual oxidation reactions, this review integrates oxidation mechanisms, catalyst chemistry, and emerging structured catalyst architectures to provide a unified perspective on the design of efficient, durable, and scalable catalytic systems for environmental oxidation applications, while identifying key challenges and future research directions. Full article

Decarbonization of district heating (DH) systems requires practical solutions that can reduce greenhouse-gas (GHG) emissions while utilizing existing infrastructure. Therefore, the study experimentally evaluates hydrogen–methane-based gas co-combustion in a real urban DH installation in Riga, Latvia, using a 6.3 MW hot-water boiler operating under commercial conditions without equipment modification. Experiments were conducted under steady-state operating conditions by blending hydrogen with the baseline methane-based gas at volumetric fractions of 0%, 10%, and 20%. Thermal performance and emissions (CO₂, NO_x, and CO) were monitored during 30 min measurement periods, and three independent experiments were performed for each hydrogen blending level. The experimental data were analyzed using one-way analysis of variance (ANOVA) to evaluate the statistical significance of the observed changes. Stable ignition, flame anchoring, and load-following performance were maintained under all investigated conditions, and no flashback or blow-off events occurred. Boiler efficiency remained essentially constant at approximately 92% (92.1–91.9%), while thermal output was maintained at 6.3 MW. When CO₂ emissions were normalized to useful thermal energy output (kg CO₂/MWh), the specific CO₂ emission intensity decreased from 202 kg/MWh for pure methane-based gas operation to 161 kg/MWh at 20 vol.% hydrogen addition, corresponding to an approximately 20% reduction in the carbon intensity of delivered heat under the investigated operating conditions. Carbon monoxide (CO) emissions remained low (~6–7 mg/kWh) and particulate matter concentrations remained below 1 mg/m³. Nitrogen oxide emissions increased moderately from approximately 40 mg/kWh to 52 mg/kWh due to enhanced combustion temperatures but remained within applicable regulatory limits. No degradation of safety systems, fuel metering equipment, or infrastructure and no leakage events were observed during the experiments. The results demonstrate that hydrogen blending up to 20 vol.% can achieve substantial reductions in the carbon intensity of heat generation while preserving boiler performance and operational safety, confirming hydrogen co-combustion as a practical transitional decarbonization pathway for existing DH systems. They also uncover the potential of hydrogen blending to support the sustainable decarbonization of DH systems by reducing GHG emissions while preserving existing infrastructure and operational reliability. Full article

This study investigates carbon monoxide (CO) emission potential and kinetics in two biowaste composting facilities, one of which implements process hermetization in a closed hall, in accordance with the Best Available Techniques (BAT) for Waste Treatment, representing a more sustainable waste management approach due to the reduction in uncontrolled gaseous emissions to the environment. The flux chamber method was used to measure cumulative CO concentrations before and after compost turning across 10 compost piles located either indoors or outdoors. Maximum cumulative CO concentrations (C_COmax) and CO production rate constants (k) were calculated. Results indicate that indoor composting leads to significantly higher net CO emissions, both before and after pile turning. In all indoor piles, cumulative CO concentrations exceeded the United States Environmental Protection Agency (EPA) 1 h and 8 h exposure limits. Post-turning cumulative CO levels reached over 3000 mg CO·m⁻³, with averages ranging from above 15 to over 70 mg CO·m⁻³. These levels pose a serious health risk, potentially causing headaches, collapse, or even loss of consciousness in workers after approximately two hours of exposure. Additionally, compost turning in closed systems resulted in slower CO production, prolonging exposure. The study demonstrated that, although BAT-compliant enclosed systems are beneficial for the environment and support sustainable waste management practices, they may create hazardous conditions for workers. Therefore, continuous monitoring of gas concentrations is essential in closed composting facilities to ensure that environmentally sustainable waste treatment technologies are implemented together with adequate occupational safety measures, supporting a more comprehensive and balanced approach to sustainability. Full article

Nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H₂S) were once regarded solely as toxic environmental gases. However, accumulating evidence over the past several decades has established them as the three principal endogenous gasotransmitters that regulate a wide spectrum of physiological and pathological processes. Unlike conventional signaling molecules, gasotransmitters diffuse freely across biological membranes and exert potent biological effects through receptor-independent mechanisms, including redox-sensitive post-translational modifications and modulation of heme-containing proteins. Although the individual functions of NO, CO, and H₂S have been extensively reviewed, emerging studies indicate that these gaseous mediators rarely operate in isolation. Instead, they form a highly integrated signaling network characterized by direct chemical interactions, reciprocal enzymatic regulation, and convergence upon common downstream pathways. In this mini-review, we propose the concept of a “Gasotransmitter Trio Network,” emphasizing the molecular crosstalk among NO, CO, and H₂S as a fundamental determinant of cellular homeostasis. We first summarize the biosynthetic pathways and major signaling mechanisms of the gasotransmitter trio, including S-nitrosylation, persulfidation, and heme-dependent regulation. We then discuss recent advances revealing how interactions among these gases generate novel bioactive intermediates and coordinate redox signaling. Particular attention is given to the emerging roles of gasotransmitters in regulating ferroptosis, autophagy, and mitophagy by modulating iron metabolism, lipid peroxidation, mitochondrial quality control, and antioxidant defense systems. These findings support a unified framework in which gasotransmitters function as master regulators of cellular fate under conditions of physiological and pathological stress. Finally, we highlight recent progress in stimuli-responsive donors, CO-releasing molecules (CORMs), NO-releasing materials (NORMs), H₂S donors, and advanced nanoplatforms that enable spatiotemporally controlled gas delivery. We propose that future therapeutic strategies will increasingly rely on programmable multi-gas systems that recapitulate endogenous gasotransmitter networks. Collectively, this review provides a systems-level perspective on gasotransmitter biology and outlines emerging opportunities for the development of precision gas medicine in cardiovascular, neurodegenerative, inflammatory, metabolic, and malignant diseases. Full article

Traditional fossil-fuel-based industries, including electric power generation and petrochemical production, are plagued by their inherent carbon dioxide emissions. Current efforts to minimize CO₂ discharge tend to focus on costly capture and sequestration rather than utilizing the process energy and products to produce profitable chemicals. This work describes a concept and design strategy for a comprehensive facility to convert natural gas and air to carbon monoxide, which could be further used to synthesize desirable compounds and fuels. The basic components of the process are an improved supercritical carbon dioxide (sCO₂) electric power plant for driving solid-oxide electrolysis cell (SOEC) reduction in CO₂ to CO. This study examines opportunities for integrating a sCO₂ process with an associated air separation unit (ASU) and an SOEC, including material recycling and heat integration. A Life Cycle Assessment (LCA) is expected to show more positive results than for separate processes. Preliminary economic evaluations provide a profitable process and product route for the combined process, suggesting that carbon emission reduction could be good business. Full article

Diesel-powered equipment is widely used in underground coal mines for auxiliary transportation, material handling, and equipment relocation because of its long operating endurance, convenient refueling, and strong adaptability to complex operating conditions. However, carbon monoxide (CO) emissions from such equipment can accumulate locally under restricted ventilation, idling, and frequent start–stop operation, thereby threatening occupational health and mine safety. This review focuses on CO purification technologies for diesel-powered mining equipment. The operating characteristics and influencing factors are analyzed, and different technical routes are compared, including in-cylinder control, wet scrubbing, adsorption, non-thermal plasma (NTP), and catalytic oxidation. Recent advances in noble-metal catalysts, transition-metal and CeO₂-based reducible oxide catalysts, and single-atom catalyst (SAC) design strategies are summarized. Research progress in exhaust aftertreatment systems is also discussed. Overall, CO purification for diesel-powered mining equipment requires coordinated optimization of low-temperature activity, safety-oriented thermal management, flow resistance, and long-term operational stability. Future research should focus on structured catalytic units, durability under coupled exhaust conditions, online monitoring, and field validation to improve the compatibility of CO purification systems with underground mining conditions. Full article

Objective: The association of smoking with sleep apnea is often based on subjective data. This study quantified the effects of smoking on sleep architecture using exhaled carbon monoxide (eCO) and polysomnography (PSG). Methods: A total of 183 patients with suspected obstructive sleep apnea (OSA) were included in this prospective study. Following full-night PSG, eCO was measured within 10 min. Data were analyzed using the Generalized Linear Model (GLM). Results: Although initial unadjusted analyses showed an inverse correlation between eCO levels and central apnea count, GLM revealed that male gender was the only independent predictor for central apnea, negating the effect of eCO. GLM analyses, adjusted for age, gender, BMI, and alcohol and drug use, revealed that cumulative smoking load (pack-years) was independently associated after multivariable adjustment with reduced REM sleep duration (B = −0.345, 95% CI [−0.571; −0.119], p = 0.003) and REM sleep percentage (B = −0.099, 95% CI [−0.158; −0.040], p = 0.001). Similarly, smoking duration (years) significantly predicted decreased REM sleep duration (B = −0.426, 95% CI [−0.724; −0.128], p = 0.005) and REM percentage (B = −0.119, 95% CI [−0.197; −0.041], p = 0.003). Formal interaction analyses did not detect a statistically significant interaction with body mass index (BMI) (p > 0.05 for all interaction terms). Conclusions: In OSA, smoking is independently associated with alterations in REM sleep architecture rather than respiratory events. Cumulative smoking load and smoking duration are independently associated with alterations in REM sleep after adjusting for any other major clinical comorbidities. Full article

Greenhouse gas emissions and air pollution are closely interconnected environmental challenges with major implications for human health and global sustainability. Many of the activities that drive climate change also release pollutants such as nitrogen dioxide, sulphur dioxide, carbon monoxide, and particulate matter, which directly affect air quality and population health. This review synthesises current evidence on the main sources of greenhouse gas emissions and atmospheric pollutants, the atmospheric processes that influence air quality, and the epidemiological evidence linking air pollution exposure to adverse health outcomes. The paper also discusses the public health co-benefits of climate mitigation strategies, including the transition to cleaner energy systems, sustainable transport policies, and urban environmental interventions. Finally, the review places air pollution and climate change within the broader framework of human security, highlighting their implications for health security, environmental stability, food systems, and economic resilience. By integrating perspectives from environmental epidemiology, public health, and global environmental governance, this review provides a multidisciplinary overview of the links between greenhouse gas emissions, air quality, and human well-being, and underscores the importance of coordinated policy responses to address these interconnected challenges. Full article

Quintero is a Chilean coastal city located 40 km north of Valparaiso. In the surroundings of Quintero, there are a number of industries that generate high levels of atmospheric pollutants such as sulfur dioxide (SO₂), nitrogen oxides (NO_x), carbon monoxide (CO) and non-methane hydrocarbons (NMHCs). These compounds may also be generated during oil handling in storage facilities in this area. Quintero Bay has a port that is being used mainly for oil and copper transportation. Since 2010, there have been reports of events producing nausea, vomiting and abdominal pain in the residents of Quintero, and some previous studies have correlated these medical events with high concentrations of SO₂ and NMHCs. One of the main sources of SO₂ in the area was identified to be the Ventanas copper foundry. Following public pressure, the government stopped the operation of the foundry by mid-2023, which led to a significant decrease in SO₂ levels. However, reports of health problems persisted to some extent. In this work, delayed cross-correlation, trajectory and dispersion analyses indicate that an upwind source of air pollution impacting Quintero originates near the oil refinery in Concón, located 20 km to the south. This source of air pollution could provide a background of NMHCs, over which local emissions add up to attain very high concentrations in Quintero. Our analysis shows that there is evidence of the transport of NMHCs from the Concón refinery to the Quintero area. In 2022, of the 20 days with NMHC concentrations greater than 200 ppvb, 50% of them were associated with prevalent southwest winds. Using trajectory and dispersion analyses for eight episodes in Quintero, it has been found that an approximate fraction of pollution generated in Concón that could arrive in Quintero is between 2 and 24%. Full article

In the context of growing attention to environmental sustainability, emission reduction efforts increasingly involve all sectors, including agriculture. European “Stage” regulations (from Stage I in 2002 to Stage V in 2019) have progressively reduced regulated pollutants such as hydrocarbons (HC), nitrogen oxides (NO_x), particulate matter (PM), and carbon monoxide (CO). However, carbon dioxide (CO₂) emissions from agricultural tractors are not currently subject to specific legislation. This study assesses CO₂ emissions through their direct relationship with fuel consumption. Hourly and specific CO₂ emissions (g/kWh) were estimated using power and fuel consumption data from 877 tractors tested under OECD Code 2 procedures from the 1960s to the present. The same tractors were analyzed under two operating conditions: power take-off (PTO) dynamometer bench tests and drawbar tests, considering maximum power and rated engine speed. The four testing conditions were compared to assess differences in delivered power, fuel consumption, and CO₂ emissions. Fuel consumption was modeled through linear regression using power as the independent variable, while specific fuel consumption and fuel productivity were estimated using a nonlinear regression approach. The comparison between test conditions shows a reduction in delivered power of 21.2% when moving from the PTO dynamometer test at maximum power to the drawbar test at rated engine speed, accompanied by an 18.9% increase in specific CO₂ emissions. These findings indicate that operating conditions significantly influence tractor carbon emissions and suggest that assessments accounting for traction-related losses provide a more realistic estimate of tractor environmental performance than PTO dynamometer tests alone. The proposed approach may support the development of carbon-oriented mitigation strategies and future greenhouse gas reduction policies for agricultural mechanization. Full article

Background: Acute carbon monoxide (CO) poisoning can cause delayed neuropsychiatric sequelae (DNS) after a latent period, yet its pathophysiology remains poorly understood because of the lack of reproducible experimental models. Methods: We established a rat model of DNS using acute CO poisoning (6500 ppm for 25 min). Behavioral assessments evaluated cognition, locomotion, sensorimotor function, exploratory behavior, and reward responsiveness. Histopathological analyses assessed brain injury, and regional monoamine concentrations were quantified using high-performance liquid chromatography. Results: CO-exposed rats developed delayed and progressive behavioral abnormalities, including impaired spatial working memory, reduced locomotor activity, sensorimotor dysfunction, and diminished exploratory behavior. At 4 weeks, CO-exposed rats showed reduced Y-maze alternation (49.3% vs. 72.2%, p < 0.0001), complete loss of tape-removal success (0% vs. 100%, p < 0.001), reduced digging behavior (10.1 ± 6.9 vs. 27.4 ± 3.9, p < 0.01), and decreased locomotor activity (330.5 ± 172.1 vs. 730.5 ± 139.5 cm, p < 0.01). In contrast, olfactory discrimination, sucrose preference, and grip strength were preserved. Histopathology demonstrated persistent neuronal and inflammatory alterations. Dopamine concentrations were significantly reduced in the cortex and basal ganglia, whereas thalamic serotonin levels were increased following CO poisoning. Conclusion: Acute CO poisoning induces a reproducible DNS characterized by progressive behavioral impairment, persistent histopathological abnormalities, and regional monoaminergic dysregulation. These findings support the concept that DNS is an evolving neuropathological process and identify dopaminergic pathways as potential therapeutic targets. Full article

Carbon monoxide (CO) is a gasotransmitter generated by heme oxygenase (HO) isoforms during heme catabolism. The inducible HO-1 produces CO under conditions of redox imbalance, such as oxidative stress and inflammation. On the other hand, HO-2 constitutively generates CO, primarily during the physiological turnover of heme. Extensive evidence indicates that CO exerts autocrine effects by targeting hemoproteins, including soluble guanylyl cyclase, cyclooxygenase, and cytochromes. Furthermore, CO regulates many biological processes within the brain, including mitochondrial biogenesis, potassium channel activity, mitogen-activated protein kinase and phosphatidylinositol-3-kinase/Akt signaling. It also controls the activity of transcription factors, such as hypoxia-inducible factor-1 and peroxisome proliferator-activated receptor-γ. Through these mechanisms, CO modulates inflammatory gene expression, promotes anti-apoptotic signaling, and contributes to local stress responses. Conversely, CO produced in the hypothalamus inhibits the stress-induced release of corticotropin-releasing hormone and arginine vasopressin under pro-inflammatory conditions, resulting in reduced adrenocorticotropin hormone release and cortisol secretion from the anterior pituitary and adrenal cortex, respectively. Moreover, hypothalamic CO acts in a paracrine manner to modulate glucocorticoid release during psychological stress, including restraint or water deprivation. Together, these findings support the view that endogenous CO is a key modulator of the stress axis, exerting pleiotropic effects that integrate neuroendocrine, immune, and metabolic responses. Full article

The facet-dependent catalytic behavior of MgO in non-thermal plasma (NTP)-driven CO₂ decomposition is systematically investigated by combining experimental measurements and density functional theory (DFT) calculations. Three MgO catalysts with dominant exposure of the (100), (110), and (111) facets are synthesized. CO₂ temperature-programmed desorption (CO₂-TPD) shows that CO₂ adsorption capacity follows the order MgO(110) > MgO(111) > MgO(100), consistent with DFT-derived adsorption energies. DFT energy profiles reveal that although MgO(110) binds CO₂ most strongly, it suffers from excessively strong CO adsorption (5.84 eV), inhibiting product desorption. In contrast, MgO(111) offers a favorable CO₂ adsorption energy combined with a remarkably low CO desorption energy (0.71 eV), enabling rapid turnover. Electronic structure analyses demonstrate substantial charge transfer from MgO(111) to CO₂ (up to 1.76 |e|) and pronounced orbital hybridization near the Fermi level, which are further enhanced under plasma conditions. Plasma-catalytic tests at 0.8 W show that MgO(111) achieves the highest CO₂ conversion (60.7%) with excellent selectivity toward CO (95.3%) and O₂ (94.4%), outperforming MgO(110) and MgO(100). Increasing the input power from 0.8 to 2.5 W raises conversion to 78.1% but reduces energy efficiency due to increased gas heating or non-productive pathways. Overall, the (111)-enriched MgO is identified as an efficient and selective catalyst for NTP-based CO₂ splitting, owing to its optimal balance of adsorption strength, facile CO desorption, strong charge transfer, and plasma–catalyst synergy. This work highlights the importance of facet engineering and power optimization for designing oxide-based plasma catalysts toward energy-efficient CO₂ utilization. Full article

Wildland firefighters play a critical role in protecting communities and natural resources, yet comparatively little research has examined the occupational health risks associated with repeated smoke exposure. This narrative review analyzed documented health effects, contributing exposure determinants, and mitigation strategies across 38 studies meeting pre-specified inclusion criteria. Included studies were predominantly quantitative field investigations evaluating pulmonary, cardiovascular, metabolic, and chemical exposure outcomes. Consistent findings documented decreased lung function, elevated oxidative stress, increased carbon monoxide (CO) exposure, and cumulative cardiovascular risk. Wildland firefighters were associated with polycyclic aromatic hydrocarbon (PAH) levels 2.2–26.7 times higher than controls. Prescribed burns produced CO concentrations 233% higher than off-fire-line days. Cardiovascular disease accounts for approximately 45% of annual line-of-duty fatalities among U.S. firefighters. Contributing factors included career duration, fire type, and operational role. Altogether, these findings underscore the severe, multi-system health risks faced by wildland firefighters and highlight a pressing need for modern mitigation strategies and firefighter-specific protective technologies to safeguard long-term health. Full article

This study presents a comparative analysis of energy consumption and gaseous emissions from a compressed natural gas (CNG)-fueled vehicle under real driving emissions (RDE) conditions and values predicted using machine learning (ML) models developed from chassis dynamometer data. The analyzed components included energy consumption (EC) as well as carbon dioxide (CO₂), carbon monoxide (CO), total hydrocarbons (HC), methane (CH₄), and nitrogen oxides (NO_X). The models were trained using a limited set of easily accessible predictors, namely vehicle speed and acceleration. A hybrid modelling approach was proposed, combining laboratory data with validation under real-world conditions. Additionally, road load power (P_rl) was introduced as a novel predictor representing vehicle operating load. The results demonstrate that the models effectively capture emission trends, with the highest agreement obtained for CO, CO₂. The inclusion of P_rl improved prediction accuracy, which increased from approximately 64% to 71% for CO and from 57% to 61% for HC. For CO₂, the model achieved about 80–82% agreement with RDE measurements, with analogous levels obtained for EC. A key advantage of the proposed methodology is its reliance on a limited number of input variables, which enhances practical applicability while maintaining satisfactory accuracy. Furthermore, the use of precise laboratory data improves model robustness, and the approach enables the estimation of methane (CH₄), which is typically not measured by standard portable emissions measurement systems (PEMSs). The results confirm the effectiveness of the hybrid ML framework and highlight the importance of incorporating load-related parameters in real-world emissions and energy consumption modeling. Full article