Hypnosis and nitrous oxide impact on the school aged patients' anxiety and cooperation candidate for tooth extraction: A randomized clinical trial.

Background: This randomized clinical trial (RCT) investigated whether hypnosis would lead to favorable outcomes in reducing anxiety, enhancing cooperation, and improving physiological responses in school-aged children undergoing tooth extraction compared to nitrous oxide/oxygen (N2O/O2) and conventional behavior guidance (CBG). Methods: Sixty-six school-aged children (mean age: 7.87 ± 1.18 years) who needed one posterior primary tooth extraction were included. Children with low-to-moderate anxiety were randomly divided into three groups (n = 22 each): hypnosis, N2O/O2, and CBG. Anxiety levels during and after anesthetic injection and tooth extraction were assessed using the Venham Clinical Anxiety Scale (VCAS) and the Venham Picture Test (VPT). Changes in heart rate (HR) and oxygen saturation (SpO2) were monitored. Children's cooperation levels were measured using the Venham Clinical Cooperation Scale (VCCS). Results: The VPT scores were significantly higher in the CBG group than in the N2O/O2 and hypnosis groups (p < 0.001). The VCAS scores in the N2O/O2 group were lower than those in the CBG group (p < 0.05) and were comparable to those in the hypnosis group. The VCCS scores were significantly higher in the CBG group than in the N2O/O2 and hypnosis groups (p < 0.05). HR changes in the N2O/O2 group were significantly lower than in the hypnosis and CBG groups (p < 0.05). No significant difference in pain was observed between the groups the day after the intervention. Conclusion: N2O/O2 inhalation and hypnosis are effective in reducing self-reported and observed anxiety and improving cooperation levels in pediatric patients during dental extraction. Moreover, the frequency of reported pain was lower in the hypnosis group compared to the other groups.

Recreational Nitrous Oxide Causing Deep Vein Thrombosis and Subacute Combined Degeneration: Whip It Real Good.

Nitrous oxide (N2O) has been thought to be a harmless recreational substance by public perception, but it has been linked to subacute combined degeneration (SACD) due to induction of a functional vitamin B12 deficiency via oxidation and inactivation of the cobalt ion in its molecular structure. N2O has been rising in popularity due to several factors including accessibility, low cost, and low perceived risk, leading otherwise healthy people to develop what used to be a neurological disease experienced by select patient populations with dietary restrictions or medical conditions leading to low levels of vitamin B12. Vitamin B12 plays a crucial role in many cellular processes, and loss of functional vitamin B12 cannot be detected by measuring it directly. Substrates from its metabolic pathways such as homocysteine and methylmalonic acid must be measured to check its functional status. Vitamin B12 deficiency also leads to a hypercoagulable state due to the build-up of homocysteine in the blood. We present the case of a 26-year-old male who had reportedly used N2O for six months leading to SACD and a popliteal deep vein thrombosis. The options for treatment are abstaining from substance use and vitamin B12 supplementation; however, full recovery after SACD develops is unlikely and patients may be left with permanent neurological dysfunction from N2O use.

New insights into N2O emission and electron competition under different chemical oxygen demand to nitrogen ratios in a biofilm system.

Nitrous oxide (N2O) is a greenhouse gas that could accumulate during the heterotrophic denitrification process. In this study, the effects of different chemical oxygen demand to nitrogen ratio (COD/N) on N2O production and electron competition was investigated. The electron competition was intensified with the decrease of electron supply, and Nos had the best electron competition ability. The model simulation results indicated that the degradation of NOx-Ns was a combination of diffusion and biological degradation. As reaction proceeding, N2O could accumulate inside biofilm. A thinner biofilm and a longer hydraulic retention time (HRT) might be an effective way to control N2O emission. The application of mathematical model is an opportunity to gain deep understanding of substrate degradation and electron competition inside biofilm.

Correlations between sewage sludge composting physicochemical parameters and emissions of greenhouse gases and ammonia: A statistical analysis.

Mitigating the environmental impact of composting by the reduction of greenhouse gases (N2O, CH4) and ammonia (NH3) emissions is a major challenge. To meet this challenge, the understanding of the relationships between composted substrates initial physicochemical parameters and gas emissions is essential. From a long-term perspective, it will allow to guide the recipe formulation of the initial mixture to be composted, with a view to reducing gas emissions during composting. This study gathered literature data targeting sewage sludge composting and performed statistical correlation analyses between cumulative gas emissions and the following parameters: sewage sludge, bulking agent and composted mixture initial physicochemical parameters (pH, dry matter, total carbon, total nitrogen, C/N), the dry mass ratio of sewage sludge to bulking agent and the duration of composting. The average values of cumulative emissions show a large variability: 1.37 ± 2.71 gC.kg initial mix DM-1, 0.13 ± 0.17 gN.kg initial mix DM-1 and 2.23 ± 2.79 gN.kg initial mix DM-1 for CH4, N2O and NH3 emissions respectively. Although the correlation analysis highlighted some significant interesting correlations between initial physicochemical parameters and gas emissions (p.value < 0.05), reliable multiparametric model could not fit the data, meaning that the actual literature data are not sufficient to explain most part of gas emissions. Among the most interesting relationships, the study showed that the dry matter of the composted mixture is negatively correlated to N2O emissions, while the ratio of sewage sludge to bulking agent and the duration of composting are positively correlated to N2O emissions. It was also shown that the pH of the bulking agent is positively correlated to NH3 emissions. Considering the large part of the emission variability that is not explained and the difficulty to link the correlation with their causality, it will be interesting to improve composting gas emissions knowledge in future research by analyzing free air space, bulking agent adsorption capacity and available and biodegradable organic matter. These parameters are of particular interest in solving the main problems associated with sewage sludge composting, namely porosity and nitrogen retention. This study also highlighted the necessity to extend the duration of the composting studies over 40 days in order to measure possible N2O late release and better identify parameters influencing N2O emissions.

The distribution of particulate organic matter in the heterogeneous soil matrix - Balancing between aerobic respiration and denitrification.

Denitrification, a key process in soil nitrogen cycling, occurs predominantly within microbial hotspots, such as those around particulate organic matter (POM), where denitrifiers use nitrate as an alternative electron acceptor. For accurate prediction of dinitrogen (N2) and nitrous oxide (N2O) emissions from denitrification, a precise quantification of these microscale hotspots is required. The distribution of POM is of crucial importance in this context, as the local oxygen (O2) balance is governed not only by its high O2 demand but also by the local O2 availability. Employing a unique combination of X-ray CT imaging, microscale O2 measurements, and 15N labeling, we were able to quantify hotspots of aerobic respiration and denitrification. We analyzed greenhouse gas (GHG) fluxes, soil oxygen supply, and the distribution of POM in intact soil samples from grassland and cropland under different moisture conditions. Our findings reveal that both proximal and distal POM, identified through X-ray CT imaging, contribute to GHG emissions. The distal POM, i.e. POM at distant locations to air-filled pores, emerged as a primary driver of denitrification within structured soils of both land uses. Thus, the higher denitrification rates in the grassland could be attributed to the higher content of distal POM. Conversely, despite possessing compacted areas that could favor denitrification, the cropland had only small amounts of distal POM to stimulate denitrification in it. This underlines the complex interaction between soil structural heterogeneity, organic carbon supply, and microbial hotspot formation and thus contributes to a better understanding of soil-related GHG emissions. In summary, our study provides a holistic understanding of soil-borne greenhouse gas emissions and emphasizes the need to refine predictive models for soil denitrification and N2O emissions by incorporating the microscale distribution of POM.

Enhanced nitrous oxide emission factors due to climate change increase the mitigation challenge in the agricultural sector.

Effective nitrogen fertilizer management is crucial for reducing nitrous oxide (N2O) emissions while ensuring food security within planetary boundaries. However, climate change might also interact with management practices to alter N2O emission and emission factors (EFs), adding further uncertainties to estimating mitigation potentials. Here, we developed a new hybrid modeling framework that integrates a machine learning model with an ensemble of eight process-based models to project EFs under different climate and nitrogen policy scenarios. Our findings reveal that EFs are dynamically modulated by environmental changes, including climate, soil properties, and nitrogen management practices. Under low-ambition nitrogen regulation policies, EF would increase from 1.18%-1.22% in 2010 to 1.27%-1.34% by 2050, representing a relative increase of 4.4%-11.4% and exceeding the IPCC tier-1 EF of 1%. This trend is particularly pronounced in tropical and subtropical regions with high nitrogen inputs, where EFs could increase by 0.14%-0.35% (relative increase of 11.9%-17%). In contrast, high-ambition policies have the potential to mitigate the increases in EF caused by climate change, possibly leading to slight decreases in EFs. Furthermore, our results demonstrate that global EFs are expected to continue rising due to warming and regional drying-wetting cycles, even in the absence of changes in nitrogen management practices. This asymmetrical influence of nitrogen fertilizers on EFs, driven by climate change, underscores the urgent need for immediate N2O emission reductions and further assessments of mitigation potentials. This hybrid modeling framework offers a computationally efficient approach to projecting future N2O emissions across various climate, soil, and nitrogen management scenarios, facilitating socio-economic assessments and policy-making efforts.

Reevaluating the Drivers of Fertilizer-Induced N2O Emission: Insights from Interpretable Machine Learning.

Direct nitrous oxide (N2O) emissions from fertilizer application are the largest anthropogenic source of global N2O, but the factors influencing these emissions remain debated. Here, we compile 1134 observations of fertilizer-induced N2O emission factor (EF) from 229 publications, covering various regions and crops globally. We then employ an interpretable machine learning model to investigate the driving factors of fertilizer-induced N2O emissions. Our results reveal that pH, soil organic carbon, precipitation, and temperature are the most influential factors, overweighing the impacts of management practices. Nitrogen application rate has a positive impact on the EF, but the effect diminishes as nitrogen application rate increases, which has been overestimated in previous studies. Soil pH has three-stage influence on EF: positive when 7.3 ≤ pH ≤ 8.7, significantly negative between 6.8 and 7.3, and insignificant at lower pH levels (4.7 ≤ pH ≤ 6.8). Moreover, we confirm the nonlinear contributions of temperature and precipitation to EF, which may cause an unexpected increase in N2O emission under climate change. Our research provides crucial insights for global N2O modeling and mitigation strategies.

Acute psychotic and vitamin B12 deficiency in patient with nitrous oxide misuse: A case report.

Nitrous oxide, also called nitrous monoxide, or nitrous oxide, is a colorless and odorless gas, without toxicological effect, but it can be asphyxiating at high concentration, its misuse is increasing especially among young people. Chronic use of N2O may cause psychiatric complications, including depression, hypomania, and paranoid psychosis with visual and auditory hallucinations. We present a case of nitrous oxide abuse "laughing gas" in 25 years old woman with bizarre behavior delusions and hallucinations with a normal neurological examination. The patient had low levels of vitamin B12 (135 pmol/L). Treatment with antipsychotics and vitamin B12 (cobalamin) resolved her psychosis. In addition to the hematological and neurological effects, rare cases of acute psychosis, especially in young people with or without psychiatric history, use varies from 1 month to years. Clinicians are increasingly in need of knowledge regarding the misuse of nitrous oxide.

Unraveling the genetic potential of nitrous oxide reduction in wastewater treatment: insights from metagenome-assembled genomes.

This study explores the genetic landscape of nitrous oxide (N2O) reduction in wastewater treatment plants (WWTPs) by profiling 1,083 high-quality metagenome-assembled genomes (HQ MAGs) from 23 Danish full-scale WWTPs. The focus is on the distribution and diversity of nitrous oxide reductase (nosZ) genes and their association with other nitrogen metabolism pathways. A custom pipeline for clade-specific nosZ gene identification with higher sensitivity revealed 503 nosZ sequences in 489 of these HQ MAGs, outperforming existing Kyoto Encyclopedia of Genes and Genomes (KEGG) module-based methods. Notably, 48.7% of the total 1,083 HQ MAGs harbored nosZ genes, with clade II being predominant, accounting for 93.7% of these genes. Taxonomic profiling highlighted the prevalence of nosZ-containing taxa within Bacteroidota and Pseudomonadota. Chloroflexota exhibited unexpected affiliations with both the sec and tat secretory pathways, and all were found to contain the accessory nosB gene, underscoring the importance of investigating the secretory pathway. The majority of non-denitrifying N2O reducers were found within Bacteroidota and Chloroflexota. Additionally, HQ MAGs with genes for dissimilatory nitrate reduction to ammonium and assimilatory nitrate reduction frequently co-occurred with the nosZ gene. Traditional primers targeting nosZ often focus on short-length amplicons. Therefore, we introduced custom-designed primer sets targeting near-full-length nosZ sequences. These new primers demonstrate efficacy in capturing diverse and well-characterized sequences, providing a valuable tool with higher resolution for future research. In conclusion, this comprehensive analysis enhances our understanding of N2O-reducing organisms in WWTPs, highlighting their potential as N2O sinks with the potential for optimizing wastewater treatment processes and mitigating greenhouse gas emissions. IMPORTANCE: This study provides critical insights into the genetic diversity of nitrous oxide reductase (nosZ) genes and the microorganisms harboring them in wastewater treatment plants (WWTPs) by exploring 1,083 high-quality metagenome-assembled genomes (MAGs) from 23 Danish full-scale WWTPs. Despite the pivotal role of nosZ-containing organisms, their diversity remains largely unexplored in WWTPs. Our custom pipeline for detecting nosZ provides near-full-length genes with detailed information on secretory pathways and accessory nos genes. Using these genes as templates, we developed taxonomically diverse clade-specific primers that generate nosZ amplicons for phylogenetic annotation and gene-to-MAG linkage. This approach improves detection and expands the discovery of novel sequences, highlighting the prevalence of non-denitrifying N2O reducers and their potential as N2O sinks. These findings have the potential to optimize nitrogen removal processes and mitigate greenhouse gas emissions from WWTPs by fully harnessing the capabilities of the microbial communities.

Combined Treatment of Uterine Arteriovenous Malformation Using a 16 Fr Miniresectoscope in an Office Setting Without Anesthesia: A Case Report.

Arteriovenous malformations (AVMs) are abnormal connections between arteries and veins that bypass the capillary system. Among AVMs, uterine ones are very rare, and it is not possible to have clear data on their incidence, as a good part of the patients remain clinically asymptomatic. Uterine AVMs consist of abnormal communications between branches of the uterine artery and the myometrial venous plexus. They can lead to significant bleeding, resulting in severe anemia and the need for transfusions. Both medical and surgical therapeutic approaches are described in the literature; as regards surgical treatments, the hysteroscopic excision of the endometrial mass represents a conservative and minimally invasive approach. However, there are no reported cases in the literature of AVMs treated using a hysteroscopic approach under local anesthesia and in an office setting. In this article, we propose the case of a young woman diagnosed with postpartum uterine AVM, treated using a 16 Fr miniresectoscope (GUBBINI system; Tontarra Medizintechnik®, Tuttlingen, Germany) in an office setting with a pain control protocol (pericervical infiltration and nitrous oxide via bucconasal mask). No complications occurred, and the woman was discharged immediately after the procedure. Finally, the patient was asked how tolerable and acceptable the procedure was compared to expectations; the woman defined the procedure as very bearable and well tolerated. The outpatient treatment, with an adequate pain control protocol, proved to be less invasive for the woman, did not require narcosis and hospital admission, but was equally therapeutic and effective compared to the treatment performed in the operating room.

Long-Term Use of Nitrous Oxide Resulting in Vitamin B12 Deficiency Causing Cervical Myelopathy.

Nitrous oxide, commonly known as laughing gas, gained popularity in the medical field as an anesthetic. It also causes euphoria and acts as an anxiolytic in the human body. However, there is limited information available on its toxicity, particularly its neurotoxicity, which has been emerging in younger populations using it for recreational purposes. Here, we present a case of a young patient with subacute combined degeneration secondary to vitamin B12 deficiency from chronic use of nitrous oxide.

Impact of nitrous oxide use on parturient recall of neuraxial analgesia risks.

STUDY OBJECTIVE: Nitrous oxide affects memory and recall. We aimed to determine if using nitrous oxide during labor affected patients' ability to learn and recall the risks and benefits of neuraxial analgesia. DESIGN: Single-center, prospective cohort study. SETTING: Labor and delivery unit in a large academic medical center. PATIENTS: Nulliparous patients with spontaneous or planned induction of labor. INTERVENTIONS: Parturients chose whether to use nitrous oxide during labor. At the discussion for epidural consent, 4 risks were described: headache, infection, nerve damage, bleeding. MEASUREMENTS: Labor pain score, time from nitrous oxide discontinuation, and cervical dilation were documented at the discussion of epidural risks. Patients were assessed for unprompted recall and prompted recall of epidural risks on postpartum day 1 and unprompted recall at postpartum week 6. The number and proportion of patients who indicated each true risk (unprompted and prompted recall) or distractor (prompted recall only) were summarized by treatment group and results compared using Pearson χ2 tests. MAIN RESULTS: Of the 403 enrolled patients, 294 (73%) did not use nitrous oxide, and 109 (27%) did. The 2 groups were similar except women who used nitrous oxide were more likely to be cared for by midwives and had higher pain scores at their epidural request. Scores for unprompted or prompted recall of epidural risks were not different between women who received or did not receive nitrous oxide. All 4 risks were recalled unprompted by only 3% in the nitrous oxide group and by 6% in the group not receiving nitrous oxide (P = .18). CONCLUSIONS: The use of nitrous oxide for labor analgesia does not adversely influence a parturient's ability to recall the risks of epidural placement. Patients who receive nitrous oxide for labor analgesia should be considered eligible to provide consent for subsequent procedures.

Long-term hypothermic storage of oocytes of the European common frog Rana temporaria at various pressure regimes in gas mixtures based on oxygen, carbon monoxide, and nitrous oxide.

In recent years, the challenge of preserving amphibian biodiversity has increasingly been addressed through technologies for the short-term storage of unfertilized spawn at low positive temperatures. Previously the possibility of using a 6.5 atm gaseous mixture of carbon monoxide and oxygen for prolonged hypothermic preservation of unfertilized oocytes for more than 4 days was shown. This study aimed to investigate the viability of oocytes R. temporaria preserved under conditions of hypothermia at 2.5, 3 and 6.5 excess atm pressure in the various gas mixture compositions (CO, N2O, O2) and pure oxygen. The use of pressure up to 3 excess atmospheres was significantly beneficial compared to 6.5 atm at the 7 days storage period. The results indicate that oxygen pressure is a critical factor in maintaining oocyte viability. Admixing CO or N2O to oxygen reduced variability in the results but did not significantly affect the measured indicators (fertilization, hatching) in the experimental groups. The composition CO+O2 (0.5/3.5 ratio, 3 excess atm) reliably extended the shelf life of viable oocytes, indistinguishable from native controls by fertilization and hatching rates, to 4 days. After 7 days, oocytes exhibited fertilization and hatching rates that were 79% and 48% compared to native control. Reducing the pressure of the preserving gas mixture to 3 atm, as utilized in this study, simplifies the practical implementation of gas preservation technology for maintaining endangered amphibian species during breeding in laboratory conditions.

Suitable fermentation temperature of forage sorghum silage increases greenhouse gas production: Exploring the relationship between temperature, microbial community, and gas production.

Silage is an excellent method of feed preservation; however, carbon dioxide, methane and nitrous oxide produced during fermentation are significant sources of agricultural greenhouse gases. Therefore, determining a specific production method is crucial for reducing global warming. The effects of four temperatures (10 °C, 20 °C, 30 °C, and 40 °C) on silage quality, greenhouse gas yield and microbial community composition of forage sorghum were investigated. At 20 °C and 30 °C, the silage has a lower pH value and a higher lactic acid content, resulting in higher silage quality and higher total gas production. In the first five days of ensiling, there was a significant increase in the production of carbon dioxide, methane, and nitrous oxide. After that, the output remained relatively stable, and their production at 20 °C and 30 °C was significantly higher than that at 10 °C and 40 °C. Firmicutes and Proteobacteria were the predominant silage microorganisms at the phylum level. Under the treatment of 20 °C, 30 °C, and 40 °C, Lactobacillus had already dominated on the second day of silage. However, low temperatures under 10 °C slowed down the microbial community succession, allowing, bad microorganisms such as Chryseobacterium, Pantoea and Pseudomonas dominate the fermentation, in the early stage of ensiling, which also resulted in the highest bacterial network complexity. According to random forest and structural equation model analysis, the production of carbon dioxide, methane and nitrous oxide is mainly affected by microorganisms such as Lactobacillus, Klebsiella and Enterobacter, and temperature influences the activity of these microorganisms to mediate gas production in silage. This study helps reveal the relationship between temperature, microbial community and greenhouse gas production during silage fermentation, providing a reference for clean silage fermentation.

Assessment and optimization of wastewater treatment plant in terms of effluent quality, energy footprint, and greenhouse gas emissions: An integrated modeling approach.

Wastewater treatment plants (WWTPs) can benefit from utilizing digital technologies to reduce greenhouse gas (GHG) emissions and to comply with effluent quality standards. In this study, the GHG emissions and electricity consumption of a WWTP were evaluated via computer simulation by varying the dissolved oxygen (DO), mixed liquor recirculation (MLR), and return activated sludge (RAS) parameters. Three different measures, namely, effluent water quality, GHG emissions, and energy consumption, were combined as water-energy-carbon coupling index (WECCI) to compare the effects of the parameters on WWTPs, and the optimal operating condition was determined. The initial conditions of the A2O process were set to 4.0 mg/L of DO, 100 % MLR, and 90.7 % RAS. Eighty scenarios with various DO, MLR, and RAS were simulated under steady-state condition to optimize the biological treatment process. The optimal operating conditions were found to be 1.5 mg/L of DO, 190 % MLR, and 90.9 % RAS, which had the highest WECCI of 2.40 when compared to the WECCI of the initial condition (1.07). This optimal condition simultaneously reduced GHG emissions by 1348 kg CO2-eq/d and energy consumption by 11.64 MWh/d. This implies that controlling DO, MLR, and RAS through sensors, valves, and pumps offers a promising approach to operating WWTPs with reduced electricity consumption and GHG emissions while attaining effluent quality standards. Additionally, the nitrous oxide stripping rate exhibited linear relationships with the effluent total ammonia and nitrite concentrations in the aerobic reactor, suggesting that monitoring dissolved nitrogen compounds in the effluent and reactor could be a viable strategy to control MLR and DO in the biological reactor. The digital-based assessment and optimization tools developed in this study are expected to hold promise for application in broader environmental management efforts.

Multidisciplinary rehabilitation following recreational nitrous oxide (N2O) misuse: evaluating service provision and rehabilitation outcomes in a cohort with serious disability.

Purpose: Recreational nitrous oxide (N2O) misuse is increasing globally. Chronic misuse can cause neurological impairments that require rehabilitation, though literature characterising rehabilitation is limited. This study aimed to evaluate rehabilitation service provision for impairments resulting from N2O misuse. Methods: A retrospective audit of hospitalised patients referred for rehabilitation for N2O toxicity was conducted between 2015 and 2022 at a single metropolitan hospital. Data were collected via medical record audit and analysed via descriptive and non-parametric statistics. Results: 16 eligible cases were identified, aged 18-43 years (50% female/male), with increasing case frequency. 12 cases received inpatient rehabilitation episodes for multifactorial sensorimotor, cognitive and psychosocial impairments. Cases articulated diverse rehabilitation goals and received intervention from a median of 6 clinical disciplines. All cases required assistance to mobilise or perform self-care activities on admission. Functional Independence Measure (FIM) scores significantly improved with rehabilitation (median FIM 84[75-93] to 117[112-123], p < .001). Despite gains in independence, all cases required referral for ongoing rehabilitation post-discharge. Conclusions: Demand for inpatient rehabilitation for disabling N2O toxicity appears to be increasing. In this series, cases were young, exhibited serious impairments, and had multidisciplinary rehabilitation needs. Inpatient rehabilitation led to significant functional improvements, though ongoing disability was evident post-discharge.

There appears to be rising demand for multidisciplinary rehabilitation to manage neurological disabilities from recreational Nitrous Oxide (N₂O) misuse.Heavy N₂O misuse can cause serious impairments and activity limitations across sensorimotor, cognitive and psychosocial domains.Intensive, multidisciplinary rehabilitation can improve functional independence for people with disabling N₂O toxicity; specialist rehabilitation services should be involved in optimising care of this population.Ongoing disability and the need for longer-term rehabilitation and support following hospital discharge were evident in severe cases of N₂O toxicity.

[N2O Emission Factors from Wastewater Treatment Plants Based on Literature Statistics and Model Fitting].

The emission of nitrous oxide （N2O） during wastewater treatment cannot be ignored. The analysis of statistical data from literature based on 126 empirical studies revealed that the geographical factors of wastewater treatment plants （WWTPs） had a significant impact on N2O emission factors. However, the N2O emission factors of WWTPs in all regions of the world were generally lower than the Intergovernmental Panel on Climate Change （IPCC） recommended values. In China, the N2O emission factors （in N2O-N/Ninfluent） of WWTPs were approximately 0.000 35-0.065 20 kg·kg-1. Meanwhile, the N2O emission factors of different wastewater treatment processes were also significantly different, especially since the sequencing batch reactor （SBR） process had higher emissions. The use of uniform default emission factors for accounting was prone to overestimate N2O emissions, and it is recommended that countries conduct actual monitoring or modeling studies to develop categorical emission factors suitable for local conditions. In addition, the N2O emission factor based on total nitrogen （TN） removal was weakly negatively correlated with TN removal in 126 empirical data, which was more in line with bioprocessing stoichiometry and could provide an accurate accounting method for N2O. To this end, a digital twin model was developed to dynamically simulate a case anaerobic-anoxic-aerobic （AAO） WWTP to comprehensively quantify the dynamic emission behavior of N2O, which demonstrated that N2O emissions had significant seasonal and daily variability and were only equivalent to 11% of the calculated value of the emission factor based on the IPCC recommendation. Comparing the scatter linear fitting and categorical mean exponential fitting methods, it was found that the latter could more accurately reflect the negative correlation between the N2O emission factors and the TN removal rate, and an exponential regression equation between the average N2O emission factor based on the amount of TN removed and the TN removal rate was further developed to predict the N2O emission. The dynamic simulation and categorical index fitting methods provided in this study are important references for the accurate accounting of N2O emissions in similar WWTPs and provide help for understanding and responding to the N2O emission problems.

Effects of aeration control strategies on nitrous oxide emissions in alternating anoxic-oxic sequencing batch reactor systems.

Reducing N2O emissions is key to controlling greenhouse gases (GHG) in wastewater treatment plants (WWTPs). Although studies have examined the effects of dissolved oxygen (DO) on N2O emissions during nitrogen removal, the precise effects of aeration rate remain unclear. This study aimed to fill this research gap by investigating the influence of dynamic aeration rates on N2O emissions in an alternating anoxic-oxic sequencing batch reactor system. The emergence of DO breakthrough points indicated that the conversion of ammonia nitrogen to nitrite and the release of N2O were nearly complete. Approximately 91.73 ± 3.35% of N2O was released between the start of aeration and the DO breakthrough point. Compared to a fixed aeration rate, dynamically adjusting the aeration rates could reduce N2O production by up to 48.6%. Structural equation modeling revealed that aeration rate and total nitrogen directly or indirectly had significant effects on the N2O production. A novel regression model was developed to estimate N2O production based on energy consumption (aeration flux), water quality (total nitrogen), and GHG emissions (N2O). This study emphasizes the potential of optimizing aeration strategies in WWTPs to significantly reduce GHG and improve environmental sustainability.