Fractional CO2 Research Articles

Women with Genitourinary Syndrome of Menopause Treated with Vaginal Estriol, Microablative Fractional CO2 Laser and Microablative Fractional Radiofrequency: A Randomized Pilot Study

Women with Genitourinary Syndrome of Menopause Treated with Vaginal Estriol, Microablative Fractional CO₂ Laser and Microablative Fractional Radiofrequency: A Randomized Pilot Study

Machine learning for underground gas storage with cushion CO2 using data from reservoir simulation

Underground natural gas storage (UNGS) is a means to store energy temporarily for later recovery and use. In such storage operations, carbon dioxide (CO2) can be injected as cushion gas to improve the operating efficiency of the working gas and then be permanently stored in the same reservoir. A potential obstacle for widespread use of this technology is that the mixing of the different gases can lead to undesired CO2 production. Herein, we use a two-component flow model to simulate injection and withdrawal periods of methane (CH4) in idealized reservoirs containing CO2. First, we simulate cases with a single well for both CH4 injection and production. From 1200 simulations with systematic variation of reservoir temperature, porosity, permeability, height, and injection time, we find that the reservoir height and permeability have the most significant impact on the production time until the well stream reaches 1% mole fraction of CO2. In another set of simulations, we investigate the impact of well spacing in seasonal gas storage scenarios with separate wells for CH4 injection and production, while CO2 injection occurs from a third well. Based on the simulated data we construct artificial neural networks (ANNs) that describe the relations between the varied input parameters and the production time of CH4, well-block mole fraction and pressure. We conclude that trained and validated ANN models are useful tools to optimize important parameters for UNGS operations, including well positioning, with the aim at maximizing the amounts of delivered gas.

Efficacy of pharmacological and non-pharmacological treatment of patients with cystocele

In patients with cystocele, the effectiveness of conservative therapy is contradictory and does not allow making recommendations for clinical practice. The aim of the study was to evaluate the efficacy of combination therapy for patients with cystocele based on electrical stimulation of the pelvic floor muscles with biofeedback and fractional photothermolysis with a CO2‑laser, alone or in combination with medications (antimuscarinics and selective β3‑agonist). The prospective randomized study included 105 patients, of whom 60 had cystocele. The patients were divided into three groups: group 1 included the patients who underwent a course of electrical stimulation of the pelvic floor muscles and photothermolysis (with fractional CO2 laser) (Physiotherapy group); in group 2, the patients received a combination of physiotherapeutic exposure and pharmacological treatment (Combination group); in group 3, the patients received only pharmacological treatment (Pharmacology group). The stimulation of the pelvic floor muscles was carried out for 10 days, the fractional CO2‑laser was used 2 times, and pharmacological treatment continued for 3 months. The bladder diary was analyzed. In group 1 there were 25 patients with cystocele, in group 2–10 patients, in group 3–25 patients with cystocele. The indicators of the bladder diary improved significantly in all groups. Increasing the urinary flow rate was more effective with physiotherapy treatment, and reducing the frequency of urination was more efficient with drug therapy. The combination therapy was the most effective. The OAB-q SF score after 3 months may be a predictor of urination frequency less than 8 times per day 6 months after therapy, and the urinary flow rate greater than 14.5 ml / sec before treatment may be a predictor of a high urinary flow rate after 3 months of therapy. Thus, in women with cystocele, the effectiveness of physiotherapy is comparable to drug therapy, and the combination therapy contributes to a better result.

A nonlinear data-driven approach to bias correction of XCO2 for NASA's OCO-2 ACOS version 10

Abstract. Measurements of column-averaged dry air mole fraction of CO2 (termed XCO2) from the Orbiting Carbon Observatory-2 (OCO-2) contain systematic errors and regional-scale biases, often induced by forward model error or nonlinearity in the retrieval. Operationally, these biases are corrected for by a multiple linear regression model fit to co-retrieved variables that are highly correlated with XCO2 error. The operational bias correction is fit in tandem with a hand-tuned quality filter which limits error variance and reduces the regime of interaction between state variables and error to one that is largely linear. While the operational correction and filter are successful in reducing biases in retrievals, they do not allow for throughput or correction of data in which biases become nonlinear in predictors or features. In this paper, we demonstrate a clear improvement in the reduction in error variance over the operational correction by using a set of nonlinear machine learning models, one for land and one for ocean soundings. We further illustrate how the operational quality filter can be relaxed when used in conjunction with a nonlinear bias correction, which allows for an increase in sounding throughput by 14 % while maintaining the residual error in the operational correction. The method can readily be applied to future Atmospheric CO2 Observations from Space (ACOS) algorithm updates, to OCO-2's companion instrument OCO-3, and to other retrieved atmospheric state variables of interest.

Influence of inner wall roughness of supersonic separator on non-equilibrium condensation of CO2 benefiting flue gas decarbonization

Supersonic separators are energy efficient and environmental separation device. Recent work has demonstrated the potential of supersonic separators to separate CO2 from flue gas. Because the supersonic flows in the separator is accompanied by shock waves and non-equilibrium condensation, the current cognition level on flow behavior in the separator is low. This work establishes a numerical model to describe the high-speed two-phase flows in the separator and the non-equilibrium condensation of CO2 during carbon capture process, and clarify the influence of inner wall roughness on carbon capture process. The results show that the rapid expansion of gas pushes the thermodynamic system to non-equilibrium state and promotes the spontaneous condensation of CO2. Wall roughness has obvious influence on normal shock wave position, non-equilibrium condensation and normal shock wave intensity. When the roughness height increases by 0.1 mm, the maximum droplet radius in the separator decreases by 17.4%, liquid CO2 fraction decreases by 49.1%, and radial range of liquid phase decreases by 46.3%.

Fractional CO 2 Laser Combined With Autologous Nanofat Injection Versus Fractional CO 2 Laser Combined With Platelet-Rich Plasma in the Treatment of Atrophic Acne Scars: A Split-Face Comparative Study With Optical Skin Imaging.

Atrophic acne scarring is a common problem. If left untreated, its implications can impair the quality of life. Various treatments, with differing degrees of success, are used to alleviate atrophic scars. To assess the efficacy of nanofat versus platelet-rich plasma (PRP) as an adjuvant therapy to fractional CO 2 laser (FCL) for atrophic acne scars. This study included 35 patients with atrophic acne scars who received 3 sessions of FCL at 1-month intervals on both sides of the face, followed by intradermal PRP injection on the left side. A single session of nanofat was injected into the right side of the face 2 weeks before the laser sessions. The evaluation was conducted 3 months after the final treatment session. After treatment, the right side of the face showed a significant reduction in Goodman scores and the indentation index of the Antera camera. The left side showed a significant difference in Goodman scores, yet the Antera camera showed a nonsignificant improvement. Nonetheless, the difference between the 2 sides was statistically insignificant. Atrophic acne scars improved with both modalities. As a result, cotreatment with these techniques may synergistically affect atrophic acne scars in efficacy and safety.

Fractional CO2 Laser with Platelet-Rich Plasma Versus Fractional CO2 Laser with Topical Insulin in The Treatment of Postacne Atrophic Scars

Background: Postacne atrophic scars (PAS) are a common acne consequence. When paired with a fractional CO2 laser, topical insulin and PRP may both help. Objective: To compare the effectiveness of a fractional CO2 laser plus PRP versus a fractional CO2 laser with TI in the management of PAS. Methods: This research was conducted on 20 patients suffering from PA atrophic scars. Enrolled patients received four sessions of FCL plus topical PRP in addition to FCL+ topical insulin on left as well as right sides of the face, respectively, at monthly intervals. One month following the fourth session, the last assessment was completed. Side effects were recorded. Patients were encouraged to use photoprotective precautions. Results: There was a statistically significant difference of acne scar grade post treatment between right and left side. Higher improvement is detected among right side treatment than left side. There was a statistically considerable difference between studied groups regarding improvement degree between both sides. For right side 10% excellent improvement, 65% good and 25% fair improvement versus 75% fair improvement and 25% good improvement for left side (P=0.001*). Conclusions: In PAS of skin-of-color populations, TI and PRP coupled with Fractional CO2 laser may both provide improvement with an excellent safety profile. However, the ease of access, low cost, and noninvasive characteristics of TI make it preferable to PRP. The degree of improvement was statistically considerably greater with TI than with PRP (P=0.001*).

Impact of skin hydration on patterns of microthermal injury produced by fractional CO2 laser.

The impact of skin hydration on patterns of thermal injury produced by ablative fractional lasers (AFLs) is insufficiently examined under standardized conditions. Using skin with three different hydration levels, this study assessed the effect of hydration status on microchannel dimensions generated by a fractional CO2 laser. A hydration model (hyperhydrated-, dehydrated- and control) was established in ex vivo porcine skin, validated by changes in surface conductance and sample mass. After, samples underwent AFL exposure using a CO2 laser (10,600 nm) at two examined pulse energies (10 and 30 mJ/mb, fixed 10% density, six repetitions per group). Histological assessment of distinct microchannels (n = 60) determined three standardized endpoints in H&E sections: (1) depth of microthermal treatment zones (MTZs),(2) depth of microscopic ablation zones (MAZs), and (3) coagulation zone (CZ) thickness. As a supplemental in vivo assessment, the same laser settings were applied to hyperhydrated- (7-h occlusion) and normohydrated forearm skin (no pretreatment) of a human volunteer. Blinded measurement of MAZ depth (n = 30) was performed using noninvasive optical coherence tomography (OCT). Modest differences in microchannel dimensions were shown between hyperhydrated, dehydrated and control skin at both high and low pulse energy. Compared to controls, hyperhydration led to median reductions in MTZ and MAZ depth ranging from 5% to 8% (control vs. hyperhydrated at 30 mJ/mb; 848 vs. 797 µm (p < 0.003) (MAZ); 928 vs. 856 µm (p < 0.003) (MTZ)), while 14%-16% reductions were shown in dehydrated skin (control vs. dehydrated at 30 mJ/mb; MAZ: 848 vs. 727 µm (p < 0.003); MTZ: 928 vs. 782 µm (p < 0.003)). The impact of skin hydration on CZ thickness was in contrast limited. Corresponding with ex vivo findings, hyperhydration was similarly associated with lower ablative depth in vivo skin. Thus, median MAZ depth in hydrated skin was 10% and 14% lower than in control areas at 10 and 30 mJ/mb pulse energy, respectively (10 mJ: 210 vs. 180 µm (p < 0.001); 30 mJ: 335 vs. 300 µm (p < 0.001)). Skin hydration status can exert a minimal impact on patterns of microthermal injury produced by fractional CO2 lasers, although the clinical implication in the context of laser therapy requires further study.

A Study Protocol of Micro-Ablative Fractional CO2 Laser in Postmenopausal Women With Overactive Bladder Syndrome

A Study Protocol of Micro-Ablative Fractional CO2 Laser in Postmenopausal Women With Overactive Bladder Syndrome

18 Combination treatment with adipose stem cell exosomes (ASCE) and fractional co2 laser for acne scars: a 12-week prospective, double-blind, randomized, split-face study

18 Combination treatment with adipose stem cell exosomes (ASCE) and fractional co2 laser for acne scars: a 12-week prospective, double-blind, randomized, split-face study

Exploring the Efficacy of Fractional Carbon Dioxide Laser as an Add-on Combination to Conventional Therapies for Treatment-Resistant Vitiligo (A Review Article).

Introduction: Vitiligo, a dermatological disorder that leads to depigmented skin patches, presents a significant challenge, particularly in resistant areas such as acral regions. Fractional CO2 laser therapy holds promise as an adjunct to conventional treatment, enhancing repigmentation. This review comprehensively explores its efficacy and safety in resistant-to-treatment vitiligo. Methods: We conducted extensive database searches in PubMed, Embase, and Cochrane, focusing on English-language literature published between 2012 and 2023. We included comparative studies that met the following criteria: (1) Participants had non-segmental vitiligo, with resistant-to-treatment localization engagement; (2) The treatment involved the use of fractional CO2 laser in combination with conventional therapies; and (3) Outcomes were assessed based on the repigmentation ratio or significant difference. We excluded studies from which data from published results could not be extracted. Results: After extensive screening of 52 articles, we finally selected five studies. The results showed that fractional CO2 laser therapy, when combined with other treatments, often shows promise in vitiligo treatment in refractory cases. Although individual responses varied, overall efficacy and safety were promising, with minimal adverse effects and no severe complications. Conclusion: The fractional CO2 laser, when used in conjunction with conventional therapies, emerges as a promising option for treating refractory vitiligo. Large-scale randomized trials and a deeper understanding of the underlying mechanisms are vital for future progress in optimizing treatment protocols, case selection, and safety.

Лазерна корекція у поєднанні з перинеопластикою для підвищення сексуального задоволення

After vaginal delivery and improper episiotomy suturing about 40% of women complaint from wide vagina and defect in pelvic support which will lead to loss of satisfaction in sexual relationship with the partner. In recent years many different methods were used for solve the complaint for many of these ladies of wide vagina and loss of satisfaction in their sexual relationship, which was either surgical or non-surgical ways.The objective: to confirm that the fractional CO2 laser was emergency noninvasive modalities to solve problem with or without simple perineoplasty could be needed to restore pelvic support and improve sexual function of women.Materials and methods: 101 women took part in this prospective study. All women were old from 22 to 45 years. The degree of vaginal laxity severity was evaluated by vaginal examination in each patient. Perineal length, vaginal orifice length were measured and female sexual function index questionnaire was used to assess sexual satisfaction score. The women had different degree of vaginal laxity and underwent fractional CO2 laser from 2 to 3 sessions with or without simple perineoplasty and follow up them for gain vaginal tightness and improvement of their sexual function.Results. There was significant correlation between increase body mass index and parity with decrease sexual function of the women as the P values equal to 0.0001 and 0.029 consequently. Regarding the anatomical variation of the genital tract that occurs to women before and after doing the laser sessions and simple perineoplasty, our study show very significant correlation between partner satisfaction and anatomical variation were P value equal the following consequently 0.003, 0.035 and 0.57. Conclusion. The degree of vaginal laxity should be clinically evaluated and accordingly the use of only fractional CO2 laser with or without simple surgical perineoplasty to achieve vaginal tightness and improve in sexual function.

Experimental investigation on using CO2/H2O emulsion with high water cut in enhanced oil recovery

CO2 emulsions used for EOR have received a lot of interest because of its good performance on CO2 mobility reduction. However, most of them have been focusing on the high quality CO2 emulsion (high CO2 fraction), while CO2 emulsion with high water cut has been rarely researched. In this paper, we carried out a comprehensive experimental study of using high water cut CO2/H2O emulsion for enhancing oil recovery. Firstly, a nonionic surfactant, alkyl glycosides (APG), was selected to stabilize CO2/H2O emulsion, and the corresponding morphology and stability were evaluated with a transparent PVT cell. Subsequently, plugging capacity and apparent viscosity of CO2/H2O emulsion were measured systematically by a sand pack displacement apparatus connected with a 1.95-m long capillary tube. Furthermore, a high water cut (40 vol%) CO2/H2O emulsion was selected for flooding experiments in a long sand pack and a core sample, and the oil recovery, the rate of oil recovery, and the pressure gradients were analyzed. The results indicated that APG had a good performance on emulsifying and stabilizing CO2 emulsion. An inversion from H2O/CO2 emulsion to CO2/H2O emulsion with the increase in water cut was confirmed. CO2/H2O emulsions with lower water cuts presented higher apparent viscosity, while the optimal plugging capacity of CO2/H2O emulsion occurred at a certain water cut. Eventually, the displacement using CO2/H2O emulsion provided 18.98% and 13.36% additional oil recovery than that using pure CO2 in long sand pack and core tests, respectively. This work may provide guidelines for EOR using CO2 emulsions with high water cut.

Comparison of Atmospheric Carbon Dioxide Concentrations Based on GOSAT, OCO-2 Observations and Ground-Based TCCON Data

Carbon dioxide (CO2) is one of the most significant greenhouse gases, and its concentration and distribution in the atmosphere have always been a research hotspot. To study the temporal and spatial characteristics of atmospheric CO2 globally, it is crucial to evaluate the consistency of observation data from different carbon observation satellites. This study utilizes data from the Total Carbon Column Observing Network (TCCON) to verify the column-averaged dry air mole fractions of atmospheric CO2 (XCO2) retrieved by satellites from October 2014 to May 2016, specifically comparing the XCO2 distributions from the Greenhouse Gases Observing Satellite (GOSAT) and Orbiting Carbon Observatory 2 (OCO-2). Our analysis indicates a strong correlation between the TCCON and both the GOSAT (correlation coefficient of 0.85) and OCO-2 (correlation coefficient of 0.91). Cross-validation further reveals that the measurements of the GOSAT and OCO-2 are highly consistent, with an average deviation and standard deviation of 0.92 ± 1.16 ppm and a correlation coefficient of 0.92. These differences remain stable over time, indicating that the calibration in the data set is reliable. Moreover, monthly averaged time-series and seasonal climatology comparisons were also performed separately over the six continents, i.e., Asia, North America, Europe, Africa, South America, and Oceania. The investigation of monthly XCO2 values across continents highlights greater consistency in Asia, North America, and Oceania (standard deviation from 0.15 to 0.27 ppm) as compared to Europe, South America, and Africa (standard deviation from 0.45 to 0.84 ppm). A seasonal analysis exhibited a high level of consistency in spring (correlation coefficient of 0.97), but lower agreement in summer (correlation coefficient of 0.78), potentially due to cloud cover and aerosol interference. Although some differences exist among the datasets, the overall findings demonstrate a strong correlation between the satellite measurements of XCO2. These results emphasize the importance of continued monitoring and calibration efforts to ensure the accurate assessment and understanding of atmospheric CO2 levels.

A novel combined technology for treating hypertrophic scars: adipose tissue extract combined with fractional CO2 laser.

Introduction: Owing to the need for liposuction and its unsuitability for allogeneic transplantation, the clinical application of stromal vascular fraction gel (SVF-gel) combined with fractional CO2 laser for scar treatment is limited. Adipose tissue extract (ATE), rich in cytokines and growth factors, offers a more convenient option for clinical practice as it can be easily prepared using purely physical methods and has low immunogenicity. We aimed to evaluate the effectiveness of ATE combined with fractional CO2 laser in the treatment of hypertrophic scars. Methods: ATE was prepared using discarded liposuction fluid from patients undergoing liposuction. A rabbit ear hypertrophic scar model was established and treated with ATE, fractional CO2 laser, or a combination. PBS was used as a control. The scar appearance and histological changes were observed. The immunohistochemistry method was used to evaluate the expression of α-SMA, while perilipin was detected using immunofluorescence. Additionally, the level of adipogenic signal C/EBPα and PPARγ mRNA was studied. Results: Following treatment, the volume of hypertrophic scar decreased, resulting in a softer texture and thinner dermis. Additionally, there was a decrease in the infiltration of inflammatory cells, and the collagen arrangement became looser and more regular, and the expression of α-SMA also decreased, with the combination of ATE and fractional laser showing the most significant improvement. Moreover, the combination group was found to promote subcutaneous fat regeneration and increase the expression of adipogenic signals C/EBPα and PPARγ. Conclusion: The combination of ATE and fractional CO2 laser treatment has been shown to inhibit the development of hypertrophic scars. This effect may be attributed to the enhancement of adipogenesis and decrease in collagen deposition.

Ash Deposition Triggers Phytoplankton Blooms at Nishinoshima Volcano, Japan

AbstractVolcanoes that deposit eruptive products into the ocean can trigger phytoplankton blooms near the deposition area. Phytoplankton blooms impact the global carbon cycle, but the specific conditions and mechanisms that facilitate volcanically triggered blooms are not well understood, especially in low nutrient ocean regions. We use satellite remote sensing to analyze the chlorophyll response to an 8‐month period of explosive and effusive activity from Nishinoshima volcano, Japan. Nishinoshima is an ocean island volcano in a low nutrient low chlorophyll region of the Northern Pacific Ocean. From June to August 2020, during explosive activity, satellite‐derived chlorophyll‐a was detectable with amplitudes significantly above the long‐term climatological value. After the explosive activity ceased in mid‐August 2020, these areas of heightened chlorophyll concentration decreased as well. In addition, we used aerial observations and satellite imagery to demonstrate a spatial correlation between blooms and ash plume direction. Using a sun‐induced chlorophyll‐a fluorescence satellite product, we confirmed that the observed chlorophyll blooms are phytoplankton blooms. Based on an understanding of the nutrients needed to supply blooms, we hypothesize that blooms of nitrogen‐fixing phytoplankton led to a 1010–1012 g drawdown of carbon. Thus, the bloom could have significantly mediated the output of carbon from the explosive phase of the eruption but is a small fraction of anthropogenic CO2 stored in the ocean or the global biological pump. Overall, we provide a case study of fertilization of a nutrient‐poor ocean with volcanic ash and demonstrate a scenario where multi‐month scale deposition triggers continuous phytoplankton blooms across 1,000s of km2.

Intelligent pointing increases the fraction of cloud-free CO2 and CH4 observations from space

For most CO2 and CH4 satellites, only a small percentage (∼10%) of observations yield successful retrievals, with the remaining ∼90% rejected, primarily due to the effects of clouds. Discarding this large fraction of data is an inefficient strategy worth reconsidering due to the costs involved in developing, launching and operating the satellites to make these observations. However, if real-time cloud data are available together with pointing capability, cloud data can guide the instrument pointing in an “intelligent pointing” strategy for cloud avoidance. In this work, multiple intelligent pointing simulations were conducted, demonstrating the significant advantages of this approach for satellites in a highly elliptical orbit (HEO), from which nearly the whole Earth disk can be observed. Multiple factors are shown to contribute to intelligent pointing efficiency such as the size and shape (or aspect ratio) of the field of view (FOV). For the current baseline orbit and Imaging Fourier Transform Spectrometer (IFTS) observing characteristics for the proposed Arctic Observing Mission (AOM), the monthly fraction of cloud-free observations is roughly a factor of 2 (ranging from ∼1.5–2.5) more than obtained with standard pointing (in which cloud information is not used). A similar efficiency is expected in a geostationary orbit (GEO) with an IFTS, however, for a dispersive instrument in HEO or GEO, the gain is more modest. This result is primarily attributed to the ∼1:1 aspect ratio of the IFTS FOV, since it is more efficient for cloud avoidance and scanning irregularly-shaped land masses than the long and narrow slit projection of a typical dispersive spectrometer. These results have implications for the design of future CO2 or CH4 monitoring satellites and constellation architectures, as well as other fields of satellite earth observation in which clouds significantly impact observations.

Global Evaluation and Intercomparison of XCO2 Retrievals from GOSAT, OCO-2, and TANSAT with TCCON

Accurate global monitoring of carbon dioxide (CO2) is essential for understanding climate change and informing policy decisions. This study compares column-averaged dry-air mole fractions of CO2 (XCO2) between ACOS_L2_Lite_FP V9r for Japan’s Greenhouse Gases Observing Satellite (GOSAT), OCO-2_L2_Lite_FP V10r for the USA’s Orbiting Carbon Observatory-2 (OCO-2), and IAPCAS V2.0 for China’s Carbon Dioxide Observation Satellite (TANSAT) collectively referred to as GOT, with data from the Total Carbon Column Observing Network (TCCON). Our findings are as follows: (1) Significant data quantity differences exist between OCO-2 and the other satellites, with OCO-2 boasting a data volume 100 times greater. GOT shows the highest data volume between 30–45°N and 20–30°S, but data availability is notably lower near the equator. (2) XCO2 from GOT exhibits similar seasonal variations, with lower concentrations during June, July, and August (JJA) (402.72–403.74 ppm) and higher concentrations during December, January, and February (DJF) (405.74–407.14 ppm). XCO2 levels are higher in the Northern Hemisphere during March, April, and May (MAM) and DJF, while slightly lower during JJA and September, October, and November (SON). (3) The differences in XCO2 (ΔXCO2) reveal that ΔXCO2 between OCO-2 and TANSAT are minor (−0.47 ± 0.28 ppm), whereas the most significant difference is observed between GOSAT and TANSAT (−1.13 ± 0.15 ppm). Minimal differences are seen in SON (with the biggest difference between GOSAT and TANSAT: −0.84 ± 0.12 ppm), while notable differences occur in DJF (with the biggest difference between GOSAT and TANSAT: −1.43 ± 0.17 ppm). Regarding latitudinal variations, distinctions between OCO-2 and TANSAT are most pronounced in JJA and SON. (4) Compared to TCCON, XCO2 from GOT exhibits relatively high determination coefficients (R2 &gt; 0.8), with GOSAT having the highest root mean square error (RMSE = 1.226 ppm, &lt;1.5 ppm), indicating a strong relationship between ground-based observed and retrieved values. This research contributes significantly to our understanding of the spatial characteristics of global XCO2. Furthermore, it offers insights that can inform the analysis of differences in the inversion of carbon sources and sinks within assimilation systems when incorporating XCO2 data from satellite observations.

Full-coverage mapping high-resolution atmospheric CO2 concentrations in China from 2015 to 2020: Spatiotemporal variations and coupled trends with particulate pollution

Understanding the spatiotemporal dynamics of atmospheric carbon dioxide (CO2) is crucial for achieving carbon neutrality and safeguarding planetary well-being. Satellite-based carbon monitoring is increasingly instrumental in studying atmospheric CO2 changes, offering a broad spatial view. However, current research lacks a comprehensive exploration of both day-to-day variations in atmospheric CO2 at a finer-resolution grid and its coupled relationship with particulate pollution, owing to a substantial number of missing values in satellite-retrieved CO2 data. To address these issues, this study presents an enhanced regression-based machine learning model, reconstructing full-coverage daily atmospheric CO2 concentrations in China from 2015 to 2020 at a 0.01° spatial resolution. Utilizing spatiotemporal high-resolution column-averaged dry-air mole fraction of CO2 (XCO2) data from the Orbiting Carbon Observatory 2 (OCO-2) as the dependent variable and multi-source environmental factors as independent variables, we achieved overall, spatial, and temporal cross-validation R2 [RMSE] results of 0.98 [0.74 ppm], 0.95 [1.15 ppm], and 0.93 [1.44 ppm], respectively. The resulting full-coverage estimates revealed significant spatial heterogeneity over time, with the highest CO2 levels primarily in spring in the North China Plain, and the lowest in summer in northern China and autumn in the Qinghai-Tibet Plateau and the south. National weekend averages of mean symmetrized residuals in XCO2 surpassed weekday averages. Within megacities such as Shanghai and Wuhan, industry-intensive areas exhibited higher XCO2 values compared to other urban areas within the same cities. Despite spatial and seasonal fluctuations, the country-average XCO2 increased from 2015 to 2020 but has decelerated recently. A moderate correlation was observed between the spatial pattern of long-term CO2 concentrations and particulate aerosols, viewed from the total atmospheric column perspective, with some regional discrepancies. The present modeling method advances carbon monitoring techniques, and the predictive data foster an enriched understanding of the carbon cycle, climate change, and sustainable development.

New coefficients of the weighted-sum-of-gray-gases model for gas radiation characteristics of hydrogen/natural gas blends combustion

To achieve carbon neutrality, hydrogen/natural gas blends are gaining momentum as a clean low-carbon fuel for the future. In order to accurately carry out the CFD numerical simulation of hydrogen/natural gas blends combustion, it is imperative to establish a precise model for gas radiation characteristics. The existing weighted-sum-of-gray-gases model (WSGGM) is not suitable for high hydrogen content fuels, such as hydrogen/natural gas blends. Hence, new coefficients of WSGGM is formulated specifically for the combustion of hydrogen/natural gas blends, drawing upon the groundwork established by the statistical narrow-band model (SNB model). This model is specifically designed to be applicable within the ambient pressures, encompassing the temperature regime of 400–2500 K, a path-length range of 0.001–60 m, and a hydrogen blending ratio of 20%–70%. The radiative heat transfer characteristics of the sum of the molar fraction of H2O and CO2 at 0.9, 0.6, and 0.3 were studied according to application conditions. The WSGGM is implemented to compute the radiative heat transfer in non-isothermal and non-homogeneous gas mixtures. When compared to the benchmark model, the deviation of the wall heat flux does not surpass 5.20%. The results demonstrate the excellent adaptability of the WSGG coefficients in simulating the radiative heat transfer during hydrogen/natural gas blends combustion.