Emission Rates Research Articles

Reactive species emission characteristics of a cold atmospheric pressure plasma source for biomedical applications operated in a test chamber

This study investigates the potentials and limitations of a novel methodology to characterize the reactive species emission dynamics of cold atmospheric plasma sources for biomedical applications. The time-resolved concentrations of ozone and nitrogen oxides during operation of a modified medical device are sampled in a test chamber environment equipped with a stirring fan for effective mixing of species. The interpretation of experimental data is supported by results from a numerical model solving the diffusion-convection equation. From the linear profiles of O3 and NO2 concentrations, emission rates of 1.3−6.4 μgs-1 for O3 and 0.07-0.1μgs-1 for NO2, depending primarily on plasma input power and fan volume flow rate, were determined for the plasma source. The conversion of these rates into geometry-specific source terms for use in the numerical model led to excellent agreement between experimental and numerical results thus validating the methodology. Finally, empirical equations describing the ozone emission rate dependence on the air flow velocity are presented. The outcomes of this study may stimulate new strategies for assessment of health risks associated with reactive species emission by medical devices based on cold plasma technology.Graphic

Higher-order effects and validity of the point-dipole approximation for conjugated extended molecular emitters near plasmonic nanostructures.

Rapid advancements in nanotechnology have allowed for the characterization of single molecules by placing them in the vicinity of nanoplasmonic structures that are known to confine light to sub-molecular scales. In this study, we introduce a theoretical framework that captures higher-order effects, and we explore the limits of the standard description of a molecular emitter as a point-dipole. We particularly focus on the role played by the emitter chain length and electron conjugation. Strong deviations are observed from the point-dipole approximation, demonstrating that higher-order effects are essential to fully capture the emission rate of extended molecules in the vicinity of nanoparticles. This deviation strongly depends on the orientation of the conjugated chain relative to the nanoplasmonic structure. Finally, we propose a simple rationalization that qualitatively assesses the difference from the point-dipole approximation.

Methane emissions from the Nord Stream subsea pipeline leaks.

The amount of methane released to the atmosphere from the Nord Stream subsea pipeline leaks remains uncertain, as reflected in a wide range of estimates1-18. A lack of information regarding the temporal variation in atmospheric emissions has made it challenging to reconcile pipeline volumetric (bottom-up) estimates1-8 with measurement-based (top-down) estimates8-18. Here we simulate pipeline rupture emission rates and integrate these with methane dissolution and sea-surface outgassing estimates9,10 to model the evolution of atmospheric emissions from the leaks. We verify our modelled atmospheric emissions by comparing them with top-down point-in-time emission-rate estimates and cumulative emission estimates derived from airborne11, satellite8,12-14 and tall tower data. We obtain consistency between our modelled atmospheric emissions and top-down estimates and find that 465 ± 20 thousand metric tons of methane were emitted to the atmosphere. Although, to our knowledge, this represents the largest recorded amount of methane released from a single transient event, it is equivalent to 0.1% of anthropogenic methane emissions for 2022. The impact of the leaks on the global atmospheric methane budget brings into focus the numerous other anthropogenic methane sources that require mitigation globally. Our analysis demonstrates that diverse, complementary measurement approaches are needed to quantify methane emissions in support of the Global Methane Pledge19.

Methane Emissions in the ESG Framework at the World Level

Methane is a strong green gas that has higher GWP. Methane emissions, therefore, form one of the critical focuses within climate change mitigation policy. Indeed, the present study represents a very novel analysis of methane emission within the ESG framework by using the data across 193 countries within the period of 2011–2020. Methane reduction on account of ESG delivers prompt climate benefits and thereby preserves the core environment, social, and governance objectives. In spite of its importance, the role of methane remains thinly explored within ESG metrics. This study analyzes how factors like renewable energy use, effective governance, and socioeconomic settings influence the emission rate of the study subject, as many previous ESG studies are deficient in considering methane. By using econometric modeling, this research identifies that increasing methane emissions remain unabated with the improvement of ESG performances around the world, particularly within key agricultural and fossil fuel-based industrial sectors. Renewable energy cuts emissions, but energy importation simply transfers the burdens to exporting nations. It therefore involves effective governance and targeted internationational cooperation, as socioeconomic elements act differently in different developed and developing countries to drive various emission sources. These findings strongly call for balanced, targeted strategies to integrate actions of mitigation into ESG goals related to methane abatement.

Effects of Forest Land Mulching on the Soil CO2 Emission Rate of Phyllostachys violascens Forests

This study investigates the dynamics of soil CO2 emissions during the cover period of Phyllostachys violascens and the impact of different cover measures, aiming to provide references for reducing the environmental effects of bamboo cover. An L27 (913) orthogonal experimental design was employed, setting the following variables: (1) heating materials: chicken manure, straw cake, and wheat ash; (2) thickness of husk layer: 15 cm, 25 cm, and 35 cm; (3) soil moisture levels before covering: moisture to 10 cm, 15 cm, and 20 cm. The soil CO2 emission rate showed a unimodal curve, with a significant overall increase during the cover period. Throughout the entire cover period, the average soil CO2 emission rate (25.39 μmol·m−2·s−1) was 5.1 times higher than that of the uncovered Lei bamboo forest (5.02 μmol·m−2·s−1) during the same period. Thicker husk layers (25 cm and 35 cm) corresponded to higher soil CO2 emission rates, with significant differences noted among the thicknesses. When the soil was moist to 10 cm, the CO2 emission rate was highest (62.51 μmol·m−2·s−1); moisture to 15 cm and 20 cm resulted in significantly lower emission rates. Chicken manure produced the highest peak CO2 emissions in the third week, at 70.64 μmol·m−2·s−1, while straw cake and wheat ash reached their peaks in the fifth week, at 66.56 μmol·m−2·s−1 and 57.58 μmol·m−2·s−1, respectively. The interactions between the three factors (heating materials, husk layer thickness, and moisture levels) significantly affected the soil CO2 emission rates. By optimally configuring these factors, CO2 emissions can be regulated. This study recommends using wheat ash or straw cake as heating materials, combined with a 25 cm husk layer thickness, and moistening the soil to 15 cm before covering. This approach effectively reduces the peak and total soil CO2 emissions while ensuring suitable soil temperatures for the growth of bamboo shoots in spring. This research provides a scientific basis for the environmental management of bamboo forests, aiding in the optimization of covering measures to achieve low-carbon and sustainable bamboo management.

Control optimization of air traffic emissions in a two-variable dynamic model

Since 1999, every report released by the International Panel on Climate Change has advocated a decrease in the greenhouse gas emissions associated with aviation in order to preserve the current climate. This study used a two variable differential equations model with a non-linear control term to address several aspects of the emissions stabilization issue. By optimizing the control term parameter, several management alternatives can be obtained based on the properties of the phase plane of the model solutions, as identified by a stability analysis. The system can be stabilised around an equilibrium point that maintains the present number of passengers, or maintains the emissions level or is nearest to its present state. Each of these options entails different issues of growth or reduction in the number of passengers and/or the emissions rate, directly obtained from the model results. The last option seems especially novel and promising, since only short-distance flight passengers are severely reduced, while long-distance and international passengers are allowed to growth, and their associated emissions are reduced to below 50 percent of their actual value. Moreover, in a scenario of slow growth in air traffic, these rates could improve, with fewer reductions in the number of short-distance passengers.

Potential Air Quality Side-Effects of Emitting H2O2 to Enhance Methane Oxidation as a Climate Solution.

Methane (CH4) is a greenhouse gas with a global warming potential 81.2 times higher than carbon dioxide (CO2). The intentional emission of oxidants into the atmosphere has been proposed as a geoengineering solution to accelerate the oxidation of CH4 to CO2, thereby reducing surface warming. However, there has been little consideration for competing atmospheric oxidation pathways that will reduce CH4 oxidation efficiencies and result in the formation of secondary pollutants such as ozone and particulate matter. Using a global chemical-transport model, we simulate a proposed technology to intentionally emit H2O2 into the atmosphere to elevate OH concentrations and enhance CH4 oxidation. We find that proposed emission rates of oxidants have minimal impacts on monthly average tropospheric ozone and particulate matter concentrations. However, competition for the oxidation of CH4 would necessitate widespread adoption of such technology to remove substantial concentrations of atmospheric CH4, which would in-turn cause considerable increases in regional winter-time particulate matter. Our work underscores the need to consider competing chemistry in evaluating the efficacy and side effects of proposals to enhance the atmospheric oxidation of CH4 as a climate solution.

Dynamic estimation of the soil environmental carrying capacity for Benzo(a)pyrene in an industrial city, China: Insight from both duration and rate of regional emission.

An in-depth investigation of the maximum environmental load is crucial for soil security and pollution prevention. This research focused on soil environmental carrying capacity (SECC) for different risk receptors in a Chinese industrial city. By determining risk threshold for various land use types, we integrated mass balance and iterative models to capture dynamic net input fluxes with spatial heterogeneity. This enabled quantitative characterization of Benzo(a)pyrene (BaP) SECC through top-down and bottom-up approaches (corresponding to duration (D) and rate of regional emission, respectively). The thresholds were in the order of agricultural land<residential land<forest<industrial land<park. The top-down analysis showed D increased ∼1.5x with a 5% input flux decline until 2031. The bottom-up analysis suggested industrial emissions decreased by approximately 10% as the pollution control period was extended from 20 to 50 years. Both methods showed that at maximum background values (C0), D was ∼4x and the industrial emission rate was ∼10% higher than at minimum C0. SECC values near industrial areas significantly decreased, even reaching negative values, signifying complete carrying capacity loss. This study provided an approach to the dynamics of SECC under diverse scenarios, aiding informed decision-making for sustainable land management.

Earthquakes Have Accelerated the Carbon Dioxide Emission Rate of Soils on the Qinghai-Tibet Plateau.

The Qinghai-Tibet Plateau (QTP) has an extensive frozen soil distribution and intense geological tectonic activity. Our surveys reveal that Qinghai-Tibet Plateau earthquakes can not only damage infrastructure but also significantly impact carbon dioxide emissions. Fissures created by earthquakes expose deep, frozen soils to the air and, in turn, accelerate soil carbon emissions. We measured average soil carbon emission rates of 968.53 g CO2 m-2·a-1 on the fissure sidewall and 514.79 g CO2 m-2·a-1 at the fissure bottom. We estimated that the total soil carbon emission flux from fissures caused by M ≥ 6.9 earthquakes on the Qinghai-Tibet Plateau from 326 B.C. to 2022 is 1.83 × 1012 g CO2 a-1; this value is equivalent to 0.51% ~ 1.48% and 2.34% ~ 5.14% of the increased annual average carbon sink resulting from the national ecological restoration projects targeting forest protection and grassland conservation in China, respectively. These earthquake fissures thus increased the soil carbon emission rate by 0.71 g CO2 m-2·a-1 and significantly increased the total carbon emissions. This finding shows that repairing earthquake fissures could play a very important role in coping with global climate change.

Suppressing non-radiative relaxation in a NIR single photon emitter: the impact of deuteration and temperature.

The fluorescence quantum yield of organic NIR-emitters is typically limited by internal conversion (IC), restricting their applications in imaging and quantum technology. Here, we study the impact of deuteration and temperature on the emission properties of dibenzoterrylene (DBT) by bulk and single molecule spectroscopy. Based on simple photophysical modelling, we first clarify how IC affects the single molecule emission rate. Next, we show that deuteration of DBT leads to a concomitant increase in the fluorescence lifetime and quantum yield by up to 60%. This clear deuterium isotope effect indicates a significant contribution of C-H-vibrations in the IC process. The solvent-dependent changes in the IC rate of hydrogenated and deuterated compounds were found to follow the predictions of the energy gap law in the weak coupling limit. This view is supported by the very weak temperature dependence of the IC rate between 5 and 300 K. Our results not only shed light on the non-radiative relaxation of a topical polycyclic aromatic hydrocarbon, but also pave the way for single molecule quantum emitters with high emission yields in the NIR.

Indoor air concentrations of PM2.5 quartz fiber filter-collected ionic PFAS and emissions to outdoor air: findings from the IPA campaign.

Per- and polyfluoroalkyl substances (PFAS) are prevalent in consumer products used indoors. However, few measurements of ionic PFAS exist for indoor air. We analyzed samples collected on PM2.5 quartz fiber filters (QFFs) in 11 North Carolina homes 1-3 times in living rooms (two QFFs in series), and immediately outside each home (single QFF), for 26 ionic PFAS as part of the 9 months Indoor PFAS Assessment (IPA) Campaign. All targeted PFAS, except for PFDS and 8:2 monoPAP, were detected indoors. PFBA, PFHpA, PFHxA, PFOA, PFOS, and 6:2 diPAP were detected in >50% of indoor samples. PFHxA, PFOA, and PFOS had the highest detection frequency (DF = 80%; medians = 0.5-0.7 pg m-3), while median PFBA concentrations (3.6 pg m-3; DF = 67%) were highest indoors. Residential indoor air concentrations (sum of measured PFAS) were, on average, 3.4 times higher than residential outdoor air concentrations, and an order of magnitude higher than regional background concentrations. Indoor-to-outdoor emission rate estimates suggest that emissions from single unit homes could be a meaningful contributor to PFBA, PFOA, and PFOS emissions in populated areas far from major point sources. Backup QFFs were observed to adsorb some targeted PFAS from the gas-phase, making reported values upper-bounds for particle-phase and lower-bounds for total air (gas plus particle) concentrations. We found that higher concentrations of carbonaceous aerosol were associated with a shift in partitioning of short chain PFCAs and long chain PFSAs toward the particle phase.

Climate Change: Mitigation Strategies and Need for Adaptation

Life on Earth is under increasing threat of anthropogenic greenhouse gas (GHG) emissions. The anthropogenic activities have unequivocally caused about 1.0°C of global warming above the pre-industrial level, and it is expected to increase further and reach 1.5°C between 2030 and 2052 if the existing emission rates persist. This perilous change in the Earth’s climate is causing uncontrollable wildfires, heatwaves, floods, droughts, storms, destruction of agricultural crops, biodiversity loss, and destruction of vulnerable ecosystems. If the current trend continues, Earth will become unhabitable and a hostile place to live. It becomes necessary to call for effective climate change mitigation strategies and adaptation mechanisms. In 2015, an internationally legally binding treaty called the Paris Agreement was adopted to tackle climate change and strengthen the global response to reduce GHG emissions. The agreement aims to hold the increase in global surface temperature to below 2°C above pre-industrial levels by 2100 and pursue efforts to limit the increase to 1.5°C. The aim of this study was to theoretically determine how erratic climate patterns are threatening and deteriorating the sustainability of diverse sectors worldwide. The article reviews some key climate change mitigation strategies such as conventional mitigation (reducing fossil-based CO2 emissions), negative emissions (carbon dioxide removals), and radiative forcing geoengineering (altering the Earth’s radiative energy budget to stabilize or reduce global temperatures). The significance of the synergy between climate change mitigation and climate change adaptation has also been discussed in this article.

Decoupling Relationship Analysis Between Carbon Emissions and Industry Development of Urban Rail Transit in China

AbstractAs the scale of development continues to expand, carbon emissions of urban rail transit (URT) in China have gradually increased each year, posing certain pressure on the carbon emission reduction efforts in the URT industry. To evaluate the current status of low-carbon development in the URT industry, this paper first constructs an annual carbon emission accounting model for URT that considers both the construction and operation processes. Based on this model, the annual carbon emissions of URT in China from 2015 to 2023 are calculated. Furthermore, based on decoupling theory, the relationship between carbon emissions and industry development in URT is explored from both the construction and operation aspects. The results show that: (1) From 2015 to 2023, the total carbon emissions of URT in China increased significantly from 14.425 million tons to 24.7072 million tons. The proportion of carbon emissions from construction is higher during the study period, but the growth rate of carbon emissions from operation is faster. (2) The order of carbon emissions from URT in different regions from largest to smallest is: East &gt; West &gt; Central &gt; Northeast. (3) During the study period, the carbon emissions from URT construction in China were weakly decoupled from the operational lines. (4) There was an expansive coupling relationship between carbon emissions from URT operation and passenger transport turnover in China. These findings can provide some guidance for the sustainable development of the URT industry.

Pro-environmental behaviors and behavioral spillover among bicycle tourists

This study investigates various pro-environmental behaviours and their relationships among bicycle tourists. These behaviours encompass preferences for cycling and walking, energy conservation, waste separation, and environmentally friendly tourism product purchases. Additionally, the study investigates past carbon emissions due to motorised transportation as bicycle tourists and their moderating effect on indicated behaviours. According to the results obtained from structural equation modelling, the adoption of carbon-free modes of transportation for environmental purposes is significantly related to segregation, conservation, and environmentally friendly tourism product purchases among bicycle tourists. The result shows evidence of behavioural spillover among bicycle tourists. Furthermore, the study reveals that the moderating effect of past motorised transportation usage is particularly pronounced in the case of segregation behaviour. Finally, the study calculated the minimum overall carbon emissions rate for an individual by transportation and discussed potential reasons.

Collective Interactions of Quantum-Confined Excitons in Halide Perovskite Nanocrystal Superlattices.

Collective optical properties can emerge from an ordered ensemble of emitters due to interactions between the individual units. Superlattices of halide perovskite nanocrystals exhibit collective light emission, influenced by dipole-dipole interactions between simultaneously excited nanocrystals. This coupling changes both the emission energy and rate compared to the emission of uncoupled nanocrystals. We demonstrate how quantum confinement governs the nature of the coupling between the nanocrystals in the ensemble. The extent of confinement is modified by controlling the nanocrystal size or by compositional control over the Bohr radius. In superlattices made of weakly confined nanocrystals, the collective emission is red-shifted with a faster emission rate, showing the key characteristics of superfluorescence. In contrast, the collective emission of stronger quantum-confined nanocrystals is blue-shifted with a slower emission rate. Both types of collective emission exhibit correlative multiphoton emission bursts, showing distinct photon bunching emission statistics. The quantum confinement changes the preferred alignment of transition dipoles within the nanocrystal and switches the relative dipole orientation between neighbors, resulting in opposite collective optical behaviors. Our results extend these collective effects to relatively high temperatures and provide a better understanding of exciton interactions and collective emission phenomena at the solid state.

Interactions between leaf phenological type and functional traits drive variation in isoprene emissions in central Amazon forest trees.

The Amazon forest is the largest source of isoprene emissions, and the seasonal pattern of leaf-out phenology in this forest has been indicated as an important driver of seasonal variation in emissions. Still, it is unclear how emissions vary between different leaf phenological types in this forest. To evaluate the influence of leaf phenological type over isoprene emissions, we measured leaf-level isoprene emission capacity and leaf functional traits for 175 trees from 124 species of angiosperms distributed among brevideciduous and evergreen trees in a central Amazon forest. Evergreen isoprene emitters were less likely to store monoterpenes and had tougher and less photosynthetically active leaves with higher carbon-to-nitrogen ratios compared to non-emitters. Isoprene emission rates in brevideciduous trees were higher with a higher diversity of stored sesquiterpenes and total phenolics content. Our results suggest that the way isoprene emissions relate to growth and defense traits in central Amazon trees might be influenced by leaf phenological type, and that isoprene may participate in co-regulating a chemical-mechanical defense trade-off between brevideciduous and evergreen trees. Such knowledge can be used to improve emission estimates based on leaf phenological type since, as a highly-emitted biogenic volatile organic compound (BVOC), isoprene affects atmospheric processes with implications for the Earth's radiative balance.

A Sustainable Route From Quartz to Bifunctional Material with Adsorbed Lanthanides for Enhanced Fluorescent Activation in Doxycycline Sensing

AbstractA nanosized bifunctional adsorbent with diamino and phenyl groups on its surface is synthesized through the functionalization of silica derived from quartz. The composition, morphology, and particle size of the functionalized silica are characterized using various physicochemical methods. The material demonstrates high sorption properties for La(III) and Ce(III), both found in Ni‐MH batteries, as well as Eu(III). The synthesized functionalized silica, with adsorbed lanthanides, is employed for sensor‐based detection of doxycycline in aqueous solutions. After sorbing lanthanides, the bifunctional adsorbent shows a linear response to doxycycline in the concentration range of 0.005–10.0 µm, with a detection limit of 0.15 µm L−1 and a quantification limit of 0.44 µm L−1. The increase in photoluminescence signal upon the addition of doxycycline is explained using Judd–Ofelt theory. Experimental W2 and W4 parameters of the Eu‐doped nanomatrix are determined to be 1.44 × 10−20 cm2 and 8.55 × 10−20 cm2, respectively, with these values increasing to 73.40 × 10−20 cm2 and 35.58 × 10−20 cm2 upon the addition of doxycycline. A significant increase in the radiative emission rate from 196 s−1 to 1977 s−1 is observed with doxycycline addition. It is demonstrated that the system containing the three lanthanides exhibits unique sensor properties, attributed to the co‐luminescence of the Eu(III) ion.

Engineered Miscanthus Biochar Performance as a Broiler Litter Amendment

This study investigates Miscanthus biochar’s potential to reduce ammonia (NH3) emissions in poultry production. Biochar from lignocellulosic biomass has proven a versatile tool in environmental remediation for water, soil, and air quality applications with ample opportunity for inclusion in agricultural systems. Ammonia emissions present a concern for animal/human health and the environment. The impacts of biochar production temperature (400 and 700 °C), organic acid activation (acetic acid, citric acid), and application rate (0.24 and 0.49 kg m−2) on broiler litter NH3 emissions were evaluated. Biochar production parameters, i.e., temperature, and acid type were found to significantly impact its performance as an NH3 control measure. The following factors, ranked by magnitude of impact, were found to statistically impact the NH3 emission rate: biochar application rate (p &lt; 0.001), biochar production temperature (p = 0.003), and lastly acid type (p = 0.007). The best performing biochar was produced at 400 °C, activated with acetic acid, and applied at a high addition rate (0.49 kg m−2). This treatment reduced cumulative NH3 volatilization after 2 weeks by 19.7%.

Methodology and uncertainty estimation for measurements of methane leakage in a manufactured house

Abstract. Methane emissions from natural gas appliances and infrastructure within buildings have historically not been captured in greenhouse gas inventories, leading to under-estimates, especially in urban areas. Recent measurements of these post-meter emissions have indicated non-negligible emissions within residences, with impacts on both indoor air quality and climate. As a result, methane losses from residential buildings have been included in the latest US national inventory, with emission factors determined from a single study of homes in California. To facilitate future additional studies investigating building methane emissions, we conducted a controlled experiment to document a methodology for such measurements and estimated associated uncertainties. We determined whole-house methane emission rates with a mass balance approach using near-simultaneous measurements of indoor and outdoor methane mole fractions at a manufactured house. We quantified the uncertainty in whole-house methane emission rates by varying the forced outdoor air ventilation rate of the manufactured house, measuring the outdoor air change rate using both sulfur hexafluoride and carbon dioxide tracers, and performing methane injections at prescribed rates. We found that the whole-house quiescent methane emission rate (i.e., emission rate when all gas appliances were off) in the manufactured house averaged 0.33 g d−1 with methodological errors in the calculated emission rates of approximately 19 % (root-mean-square deviation). We also measured the quiescent leakage from the manufactured house over 3 months to find 26 % (1σ) variability in emissions over two seasons. Our findings can be used to inform plans for future studies quantifying indoor methane losses downstream of residential meters using similar methods. Such quantification studies are sorely needed to better understand building methane emissions and their drivers to inform inventories and plan mitigation strategies.

Estimating Greenhouse Gas Emissions from Hydrogen-Blended Natural Gas Networks

Methane is a significant contributor to anthropogenic greenhouse gas emissions. Blending hydrogen with natural gas in existing networks presents a promising strategy to reduce these emissions and support the transition to a carbon-neutral energy system. However, hydrogen’s potential for atmospheric release raises safety and environmental concerns, necessitating an assessment of its impact on methane emissions and leakage behavior. This study introduces a methodology for estimating how fugitive emissions change when a natural gas network is shifted to a 10% hydrogen blend by combining analytical flowrate models with data from sampled leaks across a natural gas network. The methodology involves developing conversion factors based on existing methane emission rates to predict corresponding hydrogen emissions across different sections of the network, including mainlines, service lines, and facilities. Our findings reveal that while the overall volumetric emission rates increase by 5.67% on the mainlines and 3.04% on the service lines, primarily due to hydrogen’s lower density, methane emissions decrease by 5.95% on the mainlines and 8.28% on the service lines. However, when considering the impact of a 10% hydrogen blend on the Global Warming Potential, the net reduction in greenhouse gas emissions is 5.37% for the mainlines and 7.72% for the service lines. This work bridges the gap between research on hydrogen leakage and network readiness, which traditionally focuses on safety, and environmental sustainability studies on methane emission.