Increasing O2 Concentration Research Articles

Unravelling the effect of H2O and O2 in flue gas on Integrated carbon capture and dry reforming of methane

Integrated carbon capture and utilization by dry reforming of methane (ICCU-DRM) is an efficient technology for concentrating and utilizing diluted CO2 from flue gas. Significant progresses have been made in developing efficient adsorption-catalytic dual functional materials (DFMs) for ICCU-DRM. However, reaction characteristics are mainly obtained under the idealized flue gas, disregarding the presence of H2O and O2 in industrial flue gases, which may lead to notable distinctions on ICCU-DRM reactions. Herein, reaction characteristics of ICCU-DRM with the presence of single steam or O2 and their coexistence in flue gas are comprehensively investigated using a Ni-CaO DFM. Results show that steam promotes the cladding effect of CaO on catalyst, resulting in the delay of in-situ DRM. Meanwhile, the oxidation of DFM by O2 deactivates the catalyst in DFM, and the increase of O2 concentration in flue gas leads to an aggravated deactivation. With the presence of both steam and O2 in the flue gas, the delayed in-situ DRM is intensified, and O2 dominates the negative effect.

Short-term exposure to ozone may trigger the onset of Kawasaki disease: An individual-level, case-crossover study in East China

Kawasaki disease (KD) is an acute, systemic vasculitis that primarily affects children aged under the age of 5. While environmental factors have been linked to the development of KD, the specific role of ozone (O3) pollution in triggering the disease onset remains uncertain. This study aimed to examine the associations between short-term O3 exposure and KD onset in children. Utilizing a satellite-based model with a spatial resolution of 1 × 1 km, we matched 1808 KD patients (out of a total of 6115 eligible individuals) to pre-onset ozone exposures based on their home addresses in East China between 2013 and 2020. Our findings revealed a significant association of O3 exposure with KD onset on the day of onset (lag 0 day). However, this association attenuated and became statistically insignificant on lag 1 and lag 2 days. Each interquartile range (52.32 μg/m3) increase in O3 concentration at lag 0 day was associated with a 16.2% (95% CI: 3.6%, 30.3%) increased risk of KD onset. The E-R curve for O3 exhibited a plateau at low concentrations and then increased rapidly at concentrations ≥75 μg/m3. Notably, these associations were stronger in male children, younger children (<2 years of age) and patients experiencing KD onset during the warm season. This study provides novel epidemiological evidence indicating that short-term O3 exposure is associated with an increased risk of childhood KD onset. These findings emphasized the importance of considering this environmental risk factor in KD prevention strategies.

Health Burden and Driving Force Changes Due to Exposure to PM2.5 and O3 from 2014 to 2060 in a Typical Industrial Province, China

While air quality in China has improved significantly in recent years, the population is becoming increasingly vulnerable to air pollution due to the aging population. In this study, we assessed premature deaths attributable to long- and short-term exposures to PM2.5 and O3, as well as their driving forces in Shandong from 2014 to 2060 based on county-level near-real-time air pollutant concentration datasets and projected concentrations of PM2.5 and O3. We found that the concentrations of PM2.5 and O3 in most districts and counties from Shandong are still higher than the corresponding concentration limit of Grade II. Premature mortality caused by long- and short-term exposures to PM2.5 decreased by 13,045 and 8092 in 2020 compared with those in 2014, respectively. Furthermore, premature mortality attributable to short-term exposure to O3 was 36.08% higher than that due to short-term exposure to PM2.5 in 2020. The results of the driving force analysis indicate that the health benefits brought about by the improvement in air quality have been offset by the changes in population age structure. In the future, the increase in O3 concentration and population aging are the top two driving forces having adverse effects on the health burden. This study provides support for controlling the health risks of PM2.5 and O3 pollution, especially for the development of dual-pollutant concentration targets and synergistic control strategies.

NOx and SO2 emission of oxygen carrier aided combustion in fluidized bed

Oxygen carrier aided combustion (OCAC) has been established as an innovative concept for improving fuel combustion in fluidized bed (FB) combustors. OCAC uses the particles of oxygen carrier (OC) to partly or completely replace the inert bed materials within the FB, which can make the oxygen distribution in the combustor more uniform and subsequently enhance combustion efficiency. However, the fundamental study on SO2 and NOx emissions during the OCAC is still not sufficient and controversial. In this work, the OCAC of coal and petroleum coke has been evaluated under different operating conditions on a lab-scale FB combustor with a special focus on the SO2 and NOx emissions. The conversion ratios of volatile-N (XV-N) and char-N (XC-N) have been quantitatively decoupled, and the influence of operating parameters on XC-N and XV-N has been revealed. Results showed that the OCAC concept has significantly reduced CO emission, enhanced NOx emission, and increased nitrogen conversion (XN). However, the NOx emission decreased by reducing the ilmenite ore proportion in the bed materials. This was attributed to the presence of ilmenite ore, which reduced the reducing regions and weakened the NOx reduction. Under OCAC operation, the XV-N increased significantly with the increase of O2 concentration and primary air ratio (A); and the variation of A shows a most decisive effect on XV-N. However, the XC-N was insensitive to the change of O2 concentration and A, when the XC-N was in the range of 31.01–34.89 % for all OCAC operations. The significant reduction of the SO2 emission during OCAC is mainly due to the employment of the ilmenite ore as bed materials that not only can absorb S element, but also lead to more uniform distribution of both oxygen and bed temperature, thereby improving the self-desulfurization of ash and reducing the sulfate decomposition.

Insight into Secondary Inorganic Aerosol (SIA) production enhanced by domestic ozone using a machine learning technique

Taiwan has prioritized management and air pollution control of ozone in the past decade. Atmospheric ozone reacts with gaseous precursors to produce secondary inorganic aerosols (SIAs), which worsen air quality to a great extent. The present study applied a bivariate polar plot, K-means clustering, and a nonlinear autoregressive network with exogenous input neural network (NARX-NN) to identify the sources of O3 and the formation mechanism of SIAs in an urban area, aiming to facilitate the development of exposure risk assessment methods and an O3 pollution early warning system for human health protection. Results show that the present NARX-NN model could be used to capture 72 h ahead of water-soluble inorganic salts (WIS) and O3 concentrations accurately with R2 of 0.71 for NO3-, 0.72 for SO42-, 0.80 for NH4+, and 0.79 for O3 concentrations. Based on the statistical and K-means clustering analysis, the domestic high O3 hours in a year (O3 concentrations>60 ppb) account for up to 76% and 99% of the total high O3 hours in northern and southern Taiwan, respectively. Under volatile organic compounds (VOCs)-limited regime, an increase in O3 concentrations by 57.4% was found to enhance heterogeneous oxidation reaction to produce SIAs by 48.0% of NO3- and 56.6% of SO42- under prevailing northeast monsoon during winter and spring seasons. It is evident that strict control measures are still necessary for local ozone sources to maintain air quality. The source tracing framework developed in the present study is applicable for policymakers to develop early warning systems and maintain air quality during the decision-making process.

The magpie and the grapes: increasing ozone exposure impacts fruit consumption by a common corvid in a suburban environment.

The Eurasian magpie Pica pica is a resident bird species able to colonize farmlands and anthropized environments. This corvid shows a wide trophic spectrum by including fruits, invertebrates, small vertebrates and carcasses in its diet. A camera-trap experiment was carried out to test the effect of different ozone (O3) concentrations on potted Vitis vinifera plants, which resulted in different grape consumption rates by suburban birds. The test was performed at an Ozone-Free Air Controlled Exposure (FACE) facility, consisting of nine plots with three ozone (O3) levels: AA (ambient O3 concentration); and two elevated O3 levels, 1.5× AA (ambient air with a 50% increase in O3 concentration) and 2.0× AA (ambient air with a 100% increase in O3 concentration). Camera-traps were located in front of each treatment area and kept active for 24 h day-1 and for 5 days at a time over a period of 3 months to monitor grape consumption by birds. We collected a total of 38 videos. Eurasian magpies were the only grape consumers, with a total of 6.7 ± 3.3 passages per hour (mean ± SD) and no differences across the different O3 treatments. Grapes in the AA treatment were consumed significantly more quickly than those in the 1.5× AA treatment, which in turn, were consumed faster than those in the 2.0× AA treatment. At 3 days from the start of treatment, 94%, 53% and 22% berries from the AA, 1.5× AA and 2.0× AA treatments had been eaten, respectively. When the O3 was turned off, berries were consumed at the same rate among treatments. Increasing O3 concentrations limited grape consumption by magpies probably because O3 acted as a deterrent for magpies, although the lower sugar content recorded in the 2.0× AA berries did not affect the consumption when O3 was turned off. Our results provided valuable insights to mitigate human-wildlife conflicts in suburban environments. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Characterizing Ozone Sensitivity to Urban Greening in Los Angeles Under Current Day and Future Anthropogenic Emissions Scenarios

AbstractCities are simultaneously implementing urban greening and reducing anthropogenic emissions to combat climate change, but these strategies can have complex and potentially counteracting effects on regional atmospheric chemistry. Urban greening can increase emissions of volatile organic compounds (BVOCs), while climate change mitigation strategies reduce co‐emitted pollutants such as nitrogen oxides (NOx). The nonlinear relationship between ozone (O3) and BVOC and NOx concentrations makes it crucial to investigate potential interactions between urban greening and anthropogenic emissions reductions. Here, we use regional atmospheric chemistry modeling to assess O3 sensitivity to a 50% increase in urban vegetation in the Los Angeles Basin. We evaluated potential interactions between urban greening and climate change mitigation by running urban greening simulations with current day and future anthropogenic emissions that reflect renewable energy adoption and electrification in Los Angeles, CA. Our model results show that urban greening increased daily maximum 8‐hr ozone concentrations with higher increases modeled under current day anthropogenic emissions. Urban greening had complex effects on hourly O3 concentrations, with increased O3 concentrations up to 0.95 ppb during the day following increased biogenic emissions and reduced urban O3 concentrations up to 0.41 ppb at night following reduced ventilation of NOx. Under the future anthropogenic emissions scenario, reductions in NOx somewhat mitigated the daytime O3 penalties of urban greening but also dampened nighttime O3 reductions. Our results suggest that urban greening will likely have regional O3 penalties if new vegetation is high isoprene emitting, even as NOx emissions are drastically reduced following climate change mitigation.

Insights into optimal gas-ash-energy nexus: Oxy-steam combustion of spent pot lining

Altering the atmosphere type may boost the physicochemical drivers of the combustion, thus contributing to the circularity and sustainable management of hazardous wastes. This study aimed to compare the combustions of spent pot lining (SPL) in the oxy-steam and air atmospheres. The SPL combustion with 21% (Oxy21), 30% (Oxy30), and 40% (Oxy40) O2 in the oxy-steam atmosphere improved the performance indices. Weighted mean activation energy (Em) fell from 148.36 kJ/mol in the air atmosphere to 118.04 kJ/mol in Oxy21, with the lowest Em value occurring in Oxy30 (referred to as energy-saving pathway). With the temperature rise, the pattern of fluorine distributions in the air atmosphere (the oxy-steam atmosphere) exhibited 65.60 → 92.27% (65.87 → 9.08%) of fluorine in bottom ash, 7.33 → 31.84% (22.31 → 72.83%) in off-gas, and 0.4 → 2.56% (11.82 → 22.22%) in fly ash. The increased O2 concentration slightly affected the combustion characteristic indices and fluorine distributions. Steam appeared to enhance the pore expansion. The advance decomposition of Na3AlF6, the new emergence of NaAlO2, and the disappearance of CaF2 characterized the oxy-steam combustion of SPL. The gas-ash-energy nexus was jointly optimized via artificial neural network. The oxy-steam combustion destroyed the stability of both soluble and insoluble fluorine, thus greatly releasing fluorine-bearing gas.

Ozone Pollution and Acute Exacerbation of Asthma in Residents of China: An Ecological Study.

The evidence for a causal relationship between high-level ozone (O3) exposure and acute exacerbation of asthma among adults is limited, and the conclusions are less definitive. Here we collected the daily data on asthma cases, O3 exposure, and meteorological factors from 2010 to 2016 in Shijiazhuang, China. We investigated the risk of asthma exacerbation associated with high-level ozone exposure using a polynomial distributed lag model (PDLM). Using a generalized additive model (GAM), we estimated the interactive effects between O3 and other pollutants as well as meteorological factors on asthma exacerbation. A total of 7270 patients with asthma were enrolled from 22 governmental hospitals in 13 counties. Each 10 μg/m3 increase in O3 concentration on the exacerbation of asthma was associated with a 1.92% (95% CI = 0.80-3.03%) higher risk of asthma exacerbation on day lag 7. The cumulative risk of O3 on asthma exacerbation increased by 18.9% (95% CI = 12.8-25.4%) on the 14th day. High consecutive levels of O3 increase the risk of asthma exacerbation, and the interactive effect of O3 and sulfur dioxide (SO2) appears before the exacerbation onset. These findings suggested that O3 should be an important risk factor for asthma exacerbation, and health benefits in reducing asthma exacerbation risk would be gained with continued efforts to improve the air quality in China.

Investigating the impact of oxygen concentration on fire dynamics using numerical simulation with FDS

The world is experiencing an increase in demand for medical facilities due to the worsening of environmental and political conditions leading to emergencies that could suddenly increase the patients count in hospitals. The extensive use and storage of oxygen in hospitals and violation of the fire safety management practices lead to the occurrence and worsening of fire accidents. Though many researchers documented the influence of O2 enrichment on fire dynamics, there are only limited studies present. This article attempts to investigate the effects of varying oxygen concentrations - 21% (v/v), 22% (v/v), and 23% (v/v) - on fire dynamics in a hospital environment using Fire Dynamic Simulator (FDS). The changes in Mass Loss Rate (MLR), Heat Release Rate (HRR), temperature profile, flash over occurrence and thermal intensity were reported and compared with varying oxygen concentration. The results show a significant increase in MLR and HRR with the increase in O2 concentration, which directly contributed to the earlier occurrence of flashover. For oxygen concentrations of 21% (v/v), 22% (v/v), and 23% (v/v), the highest temperatures achieved were 1395 °C, 1421 °C, and 1494 °C and the thermal intensity values were found to be 966 kW.m-2, 1027 kW.m-2, and 1074 kW.m-2, respectively. The variation in peak temperature and thermal intensity at 21% (v/v) and 23% (v/v) O2 concentration, is found to be 7.1% and 11%, respectively. The findings provide a valuable insight that the oxygen concentration in a fire can impact the fire dynamics. This study can aid in the development of effective fire safety management systems for hospital environments. In addition, the process industries have a key role to play in supporting hospitals to adopt proper approaches, drawing on lessons learned from managing flammable and explosive atmospheres in chemical processes. These simulation results will give better understanding to adopt relevant safety codes for the hospitals.

Reduction potential of vehicular emission in Chengdu, China: A case study of COVID-19

The spread of coronavirus disease 2019 has significantly reduced human activities worldwide, providing a unique opportunity to assess the emission reduction potential. The impact of the lockdown on vehicular emission and traffic-related monitoring data in Chengdu, located in the Sichuan Basin, still needs to be clearly understood. In this study, we evaluated the influence of the lockdown in traffic flow, vehicular emission, and roadside environments in Chengdu based on the newly developed dynamic traffic emission inventories with high spatial and temporal resolutions and the observed pollutant concentrations at the traffic-related roadside stations. The pollutant emission intensities were highest in the central districts, and unexpectedly, the highest reduction of traffic flows and vehicular emissions occurred in the suburban areas, indicating that vehicular control in the suburban areas cannot be negligible and emission reduction in the central districts is limited. The reduction potential of vehicular CO, HC, NOx, and PM emissions in the entire Chengdu city was as high as 62%, 67%, 76%, and 71%, in which the NOx reduction potential is most significant under the extreme lockdown scenario. The vehicular emission reduction made CO, NO2, PM10, and PM2.5 concentrations decline by 57%–60%, 48%–61%, 44%–66%, and 36%–45% while O3 increase by 84%–380% at the three traffic-related roadside stations, and the increased O3 concentrations might be related to the weakened titration of NO in the VOC-limited O3 formation regime. Our study will provide novel insights into the potential of emission reduction and the development of vehicle emission control in urban areas.

Rethinking the role of transport and photochemistry in regional ozone pollution: insights from ozone concentration and mass budgets

Abstract. Understanding the role of transport and photochemistry is essential to mitigate tropospheric ozone (O3) pollution within a region. In previous studies, the O3 concentration budget has been widely used to determine the contributions of two processes to the variations of O3 concentrations. These studies often conclude that local photochemistry is the main cause of regional O3 pollution; however, they fail to explain why O3 in a targeted region is often primarily derived from O3 and/or its precursors transported from the outside regions, as reported by many studies of O3 source apportionment. Here, we present a method to calculate the hourly contributions of O3-related processes to the variations of not only the mean O3 concentration but also the total O3 mass (the corresponding budgets are noted as the O3 concentration and mass budget, respectively) within the atmospheric boundary layer (ABL) of the concerned region. Based on the modelling results of WRF-CMAQ (Weather Research and Forecasting and Community Multiscale Air Quality), the two O3 budgets were applied to comprehensively understand the effects of transport and photochemistry on the O3 pollution over the Pearl River Delta (PRD) region in China. Quantified results demonstrate the different role of transport and photochemistry when comparing the two O3 budgets: photochemistry drives the rapid increase of O3 concentrations during the day, whereas transport, especially vertical exchange through the ABL top, controls both rapid O3 mass increase in the morning and decrease in the afternoon. The diurnal changes of the transport contributions in the two O3 budgets highlight the influences of the ABL diurnal cycle and regional wind fields on regional O3 pollution. Through high contributions to the O3 mass increase in the morning, transport determines that most O3 in the PRD originates from the global background and emissions outside the region. However, due to the simultaneous rapid increase of ABL volumes, this process only has a relatively limited effect on O3 concentration increase compared to photochemistry, and transport effect on the regional sources of O3 cannot be illustrated by the O3 concentration budget. For future studies targeting O3 and other secondary pollutants with moderately long atmospheric lifetimes (e.g. fine particulate matter and some of its components), insights from both concentration and mass budgets are required to fully understand the role of transport, chemistry and other related processes.

Continuation of investigation of effect of O2 in plasma gas on parameters of nitrogen microwave-induced plasma optical emission spectrometry

We studied the effect of O2 content in the range up to 80% in plasma gas on the plasma characteristics, the analyte signal and the intensity of the molecular species in the nitrogen microwave-induced plasma (MIP). The plasma temperature decrease from 3.9·103 to 3.3·103 K with increasing O2 content. Mg (II)/Mg (I) intensity ratio decrease from 1.02 to 0.18, the electron density decrease from 6.6·1012 to 4·1011 cm−3. The intensity of N2 (1+ system), N2 (2+ system), N2+, NH, NO, and OH intensities increases to a certain content, and then decrease (NH) or remain constant (OH) when O2 is added. The effect of O2 content on the intensity of several atomic and ionic emission lines (covering Esum values from 1.6 to 14.7 eV) of 22 elements has been studied. The line intensity was suppressed over the entire energy range. It was shown that the O2 addition increased the limit of detection (LOD) by 1.2–4 for lines with Esum of 1.5–4 eV and by 50–60 times for lines with Esum of 4–15 eV.

Trends of inorganic sulfur and nitrogen species at an urban site in western Canada (2004–2018)

A 15-year (2004–2018) record of measurement data of gaseous and particulate sulfur and nitrogen pollutants in air collected at an urban site in Burnaby in western Canada was analyzed for generating their decadal trends using three different methods, including linear regression, Mann-Kendall test and Theil-Sen trend estimator (MK-TS), and ensemble empirical mode decomposition (EEMD). Annual mean concentration of SO2 and SO42− decreased by about 59% and 42%, respectively, during the 15-year period. The slower decreases of SO42− than SO2 were mainly caused by the increased O3 concentration and temperature in spring and summer, which promoted conversion of SO2 to SO42− through gas-phase reaction, and by the increased aerosol pH value and availability of H2O2 in winter, which enhanced aqueous-phase SO42− formation. Accordingly, the sulfur oxidation ratio (SOR) increased by 23% or more in spring, summer, and winter during the 15-year period. Annual mean concentrations of NO2 and NO3− declined by 36% and 38%, respectively, during this period. On seasonal basis, NO3− decreased faster than NO2 in autumn and slower in winter. The non-linear responses of NO3− to NO2 concentration decreases were more evident in winter than the other seasons, partly due to the increased particulate NO3− fraction caused by decreased temperature, increased aerosol pH value, and enhanced NO3− formation caused by increased O3 concentrations. Annual mean concentration of NH3 showed small increases due to stable NH3 emission and reduced conversion of NH3 to NH4+. NH4+ concentration decreased by 51% during the 15-year period. These results suggest that reduced oxidants levels are likely responsible for weakened formation of secondary inorganic aerosols, besides emission reductions for SO2 and NO2.

Future impacts of O3 on respiratory hospital admission in the UK from current emissions policies

Exposure to ambient ozone (O3) O3 is associated with impacts on human health. O3 is a secondary pollutant whose concentrations are determined inter alia by emissions of precursors such as oxides of nitrogen (NOx) and volatile organic compounds (VOCs), and thus future health burdens depend on policies relating to climate and air quality. While emission controls are expected to reduce levels of PM2.5 and NO2 and their associated mortality burdens, for secondary pollutants like O3 the picture is less clear. Detailed assessments are necessary to provide quantitative estimates of future impacts to support decision-makers. We simulate future O3 across the UK using a high spatial resolution atmospheric chemistry model with current UK and European policy projections for 2030, 2040 and 2050, and use UK regional population-weighting and latest recommendations on health impact assessment to quantify respiratory emergency hospital admissions associated with short-term effects of O3. We estimate 60,488 admissions in 2018, increasing by 4.2%, 4.5% and 4.6% by 2030, 2040 and 2050 respectively (assuming a fixed population). Including future population growth, estimated emergency respiratory hospital admissions are 8.3%, 10.3% and 11.7% higher by 2030, 2040 and 2050 respectively. Increasing O3 concentrations in future are driven by reduced nitric oxide (NO) in urban areas due to reduced emissions, with increases in O3 mainly occurring in areas with lowest O3 concentrations currently. Meteorology influences episodes of O3 on a day-to-day basis, although a sensitivity study indicates that annual totals of hospital admissions are only slightly impacted by meteorological year. While reducing emissions results in overall benefits to population health (through reduced mortality due to long-term exposure to PM2.5 and NO2), due to the complex chemistry, as NO emissions reduce there are associated local increases in O3 close to population centres that may increase harms to health.

Oxygen production at intermediate temperatures using Ca2AlMnO5+δ double perovskite-type oxides

Double-perovskite Ca2AlMnO5+δ exhibits promising oxygen uptake and release capacity at intermediate temperatures (400–700 °C), which makes it an interesting candidate for in situ oxygen production in an integrated gasification combined cycle (IGCC) process. Experiments were conducted at 10 bars by alternating gas feeds of air and various sweep gases to a packed bed filled with 300 g of granular oxygen carrier materials. These realistic operating conditions demonstrated that 15–20% oxygen can be introduced to the sweep gas, which is sufficient for autothermal gasification of solid fuels in IGCC. Argon performed slightly better than CO2 as a sweep gas, presumably because of some CO2 absorption or the higher O2 partial pressure of CO2 that inhibited O2 release. Further O2 concentration increases can be expected from increasing the temperature under reduction by feeding a fuel gas to combust with the released O2, but experiments with H2 did not produce the desired effect because the combustion reaction was too slow at the optimal reactor temperature (~ 600 °C). In general, the reduction stage was more prone to kinetic limitations, as illustrated by a significant decrease in O2 concentration when the sweep flowrate was increased. A longer oxidation stage to fully charge the oxygen carrier also increased O2 concentrations in the sweep, but this requires a process integration such as IGCC where the large quantity of warm depleted air can be effectively utilized. Furthermore, the enthalpy of oxidation of Ca2AlMnO5+δ was obtained from density functional theory modeling, equilibrium conditions in thermogravimetric analysis, packed bed experiments and directly from differential scanning calorimetry. The enthalpy of oxidation obtained by these techniques range from − 166 to − 196 kJ mol−1 O2.

Effects of Tropical Cyclones on Ozone Pollution in Hainan Island

Based on the 181 tropical cyclones data in the western North Pacific Ocean from 2015 to 2020, hourly ozone (O3) concentration data, and meteorological observation data of 18 cities and counties in Hainan Island, this study analyzed the impacts of tropical cyclones on ozone pollution in Hainan Island. We found that 40 (22.1%) tropical cyclones experienced O3 pollution in Hainan Island during the lifetime of tropical cyclones in the past six years. During the years with more tropical cyclones, more O3- polluted days occurred in Hainan Island. Highly polluted days, which were defined as more than or equal to three cities and counties exceeding the standard, were the most serious in 2019 with 39 (54.9%) polluted days. The tropical cyclones related to high pollution (HP) showed an increasing trend, with the trend coefficient and climatic trend rate of 0.725 (exceeding the 95% significance level) and 0.667 a-1, respectively. Tropical cyclone intensity was positively correlated with the maximum 8 h moving average (O3-8h) concentration in Hainan Island. Among them, HP-type tropical cyclones accounted for 35.4% of all samples in the typhoon (TY) intensity level. Cluster analysis of tropical cyclone paths showed that tropical cyclones from the South China Sea (type A) were the most common of the 67 (37%) and were the most likely to cause large-scale and high-concentration O3 pollution events in Hainan Island. The average number of HP tropical cyclones and ρ(O3-8h) of Hainan Island in type A were 7 and 121.90 μg·m-3, respectively. In addition, the tropical cyclone centers were located generally in the middle part of the South China Sea and the western Pacific Ocean near the Bashi Strait during the HP period. The change in meteorological conditions in Hainan Island under the influence of HP tropical cyclones was conducive to the increase in O3 concentration.

Effect of red mud additive on the combustion performance of lignite and sulfur fixation behaviors

ABSTRACT To reveal the role of red mud (RM) as the catalyst during the combustion behavior of lignite, two kinds of RM from Bayer red mud (SR) and sintering red mud (GR) were chosen to investigate the catalytic combustion behaviors of lignite under different oxygen contents, the action mechanism and the sulfur fixation performance by the thermogravimetric analysis (TGA) and fixed-bed reactor. Flynn–Wall–Ozawa (FWO) method was used to study the combustion kinetics. The results showed that RM can promote the release of pyrolysis volatiles and significantly improve the ignition performance of coal. Moreover, the improvement effect of RM becomes more noticeable with the increase of O2 content. RM decreased the ignition and burnout temperatures of the char combustion. The types of RM exert different catalytic properties owing to different compositions. Under oxygen-rich conditions, the apparent activation energy in the early stage of coal combustion can be significantly reduced by RM. In addition, RM enhances the peak temperature during constant combustion of coal, improves combustion rate, shortens the burnout time, and remarkably reduces SO2 emission in exhausted gas. About 83.7% SO2 in combustion gas produced at 700°C was reduced at the SR addition of 25 wt%, indicating RM is a potential and cheap catalyst for high-effective coal combustion.

Unraveling the O3-NOX-VOCs relationships induced by anomalous ozone in industrial regions during COVID-19 in Shanghai

The COVID-19 pandemic promoted strict restrictions to human activities in China, which led to an unexpected increase in ozone (O3) regarding to nitrogen oxides (NOx) and volatile organic compounds (VOCs) co-abatement in urban China. However, providing a quantitative assessment of the photochemistry that leads to O3 increase is still challenging. Here, we evaluated changes in O3 arising from photochemical production with precursors (NOX and VOCS) in industrial regions in Shanghai during the COVID-19 lockdowns by using machine learning models and box models. The changes of air pollutants (O3, NOX, VOCs) during the COVID-19 lockdowns were analyzed by deweathering and detrending machine learning models with regard to meteorological and emission effects. After accounting for effects of meteorological variability, we find increase in O3 concentration (49.5%). Except for meteorological effects, model results of detrending the business-as-usual changes indicate much smaller reduction (−0.6%), highlighting the O3 increase attributable to complex photochemistry mechanism and the upward trends of O3 due to clear air policy in Shanghai. We then used box models to assess the photochemistry mechanism and identify key factors that control O3 production during lockdowns. It was found that empirical evidence for a link between efficient radical propagation and the optimized O3 production efficiency of NOX under the VOC-limited conditions. Simulations with box models also indicate that priority should be given to controlling industrial emissions and vehicle exhaust while the VOCs and NOX should be managed at a proper ratio in order to control O3 in winter. While lockdown is not a condition that could ever be continued indefinitely, findings of this study offer theoretical support for formulating refined O3 management in industrial regions in Shanghai, especially in winter.

Sniffing Drones: A Promising Solution for Measuring Railroad Emissions in Urban Environments

Locomotive emissions from railroads can particularly impact air pollution, making it crucial to understand their impacts on human health and the environment and develop strategies to reduce them. The potential of drone technology equipped with a “sniffing” system for detecting air pollution emissions is promising and can be a valuable tool for assessing dynamic emissions. This research utilized sensor-equipped drones to measure gaseous emissions from cargo and passenger trains on a railway in Curitiba, Brazil. Reference equipment evaluated the accuracy of NO2, SO2, and O3 concentrations. The results showed that before the passage of trains, the average SO2 concentration was 20 µg/m³, with a maximum concentration of 110 µg/m³ detected during transit. The average increase in NO2 concentrations was from 30 µg/m³ to 120 µg/m³, and the average increase in O3 concentrations was from 80 µg/m³ to 135 µg/m³. The vertical profiles were evaluated before and after the passage of locomotives, indicating an accumulation of pollutants above the railroad. These findings demonstrate the potential of sniffing drones to measure railroad emissions in urban environments. They also highlight the need to regulate emissions from diesel-powered locomotives to minimize atmospheric pollution and its negative impact on public health in emerging and developing countries.