Ox Concentration Research Articles

Impact of photochemistry on wintertime haze in the Southern Sichuan Basin, China

Nitrate and organic matters (OM) have become dominant components in fine particles (PM2.5) during winter haze in recent years. Based on continuous observations of gaseous pollutants, the chemical composition of PM2.5, and other relevant data collected over a one-month period (December 1-31, 2021), we investigated the main controlling factors contributing to the formation of wintertime haze in Yibin, located in the southern Sichuan Basin. Our observations reveal that two major haze episodes occurred during the campaign. Nitrate and OM were the dominant components in PM2.5, with an overall contribution of more than 50%. Nitrate and OM concentrations nearly quadrupled and more than tripled, respectively, from the non-pollution phase to the pollution phase. Furthermore, the mixing ratios of high-activity VOCs also noticeably increased during the pollution period, particularly OVOCs mixing ratios increased by 123.83%. PM2.5 concentrations were positively correlated with Ox concentrations, with a stronger relationship observed when Ox concentrations exceeded 80 μg m–3. There were also significant positive correlations between nitrate and Ox concentrations, as well as between OVOCs and OM concentrations. Furthermore, the pollution period showed a much higher degree of photochemical aging compared to the non-pollution period. Potential Source Contribution Function (PSCF) analysis revealed that, in addition to local emissions, regional transport, particularly air pollutants from Chengdu and Chongqing, significantly contributed to winter haze in Yibin. Our findings suggest that intense atmospheric photochemical oxidation and pronounced photochemistry contributed greatly to the occurrence of severe winter haze events.

The oxytocin-oxytocin receptors system — a new pathogenetic mechanism in the development of diabetic phenotype of heart failure with preserved ejection fraction in women

Aim. To determine the pathogenetic role of the oxytocinergic system in the development of myocardium structural and functional changes in women with heart failure with preserved ejection fraction (HFpEF) associated with type 2 diabetes mellitus (DM2T) (diabetic phenotype of HFpEF).Material and methods. The study included 60 women aged 67.0±4.9 years with HFpEF stage I-IIA, FC I-III, 30 of them had DM2T who were admitted for elective coronary artery bypass grafting. The development of HFpEF is caused by coronary artery disease (CAD) and arterial hypertension (AH). Prior to surgery, all patients underwent a standard examination, blood levels of NT-proBNP, oxytocin (Ox), echocardiography were determined to find the types of left ventricular (LV) myocardial remodeling and diastolic dysfunction (DD). Myocardium biopsies of the right atrium auricle obtained during coronary bypass surgery were studied by microscopy, morphometry and immunohistochemistry (the expression of oxytocin receptors (OxR), a marker of proliferation ki-67).Results. According to echocardiography, eccentric LV hypertrophy (46.7/36.7%) and DD type 2 (47/17%, p=0.003) prevailed in the group of women with the diabetic phenotype of HFpEF. A higher content of NT-proBNP (480.72±241.87/434.46±282.78 ng/ml, p=0.06) and a lower concentration of Ox (102.11±35.89/320.37±294.71 pg/ml, p=0.0016) in blood serum were established, as well as an increase in the number of cardiomyocytes (CMC) with a high expression level OxR (63.69±19.47/12.16±23.09%, p=0.000) in patients with the diabetic phenotype of HFpEF. Negative associations were determined between the blood level of Ox and the CMC diameter (r=-0.10, p=0.020), the area of their cytoplasm (r=-0.16, p=0.000) and the area of the nuclei (r=-0.11, p=0.015) in patients of both groups. A decrease in Ox concentration in the blood of patients with diabetic phenotype of HFpEF was accompanied by an increase in the number of CMCs with a high level of OxR expression (r=-0.63, p=0.000).Conclusion. The study has shown the important involvement of oxytocinergic signaling pathways in the HFpEF pathogenesis. HFpEF associated with DM2T in women was characterized by more unfavorable structural and functional changes in the myocardium, a significant increase in the number of hypertrophied CMCs with a high level of OxR expression and Ox decrease in blood serum. The mechanisms of the first-established significant increase in the content of Ox in the blood of patients with HFpEF without diabetes and its significant decrease in patients with diabetic phenotype of HFpEF leading to more pronounced structural and functional changes in the myocardium, require further study.

Pollution characteristics and transformation mechanisms of secondary inorganic components during winter heavy pollution in Handan city in 2018–2020

The mechanism of secondary transformation of nitrate and sulfate under different relative humidity (RH), and different atmospheric oxidizing conditions is still controversial. This study focuses on the winter heavy pollution process in Handan city from 2018 to 2020, and the following results were obtained: The average concentration of PM2.5 showed a decreasing trend from year to year, but the SNA (SO42−, NO3− and NH4+) showed an increasing trend from year to year, and the concentration of nitrate exceeded that of sulfate. During the haze formation period from 2018 to 2020, a significant disparity was observed in NO2 and SO2 emissions, with NO2 emissions surpassing those of SO2. Mobile sources were found to contribute more emissions than fixed sources, particularly during the haze persistence period (HP). However, sulfate conversion outweighed nitrate conversion. HighRH and photochemical reactions induced by ozone favored the formation of nitrate and sulfate, which formated heavy haze. When 40% ≤ RH ≤ 70%, atmospheric oxidants (Ox = O3 + NO2) concentration was the highest, nitrogen oxidation ratio (NOR) and sulfur oxidation ratio (SOR) increased rapidly, and nitrate was mainly generated by photochemical reactions during daytime. When RH > 70% and the concentration of Ox was low, RH will weaken the photochemical intensity. Therefore, the liquid-phase oxidation reaction of N2O5 contributed significantly to atmospheric nitrate at night, and the liquid-phase oxidation reaction of sulfate was faster than the gas-phase one. Local emissions contributed significantly to particulate matter pollution during heavy pollution in 2018–2020, and the main sources were secondary conversion, coal combustion, biomass burning, and road dust.

A portable instrument for measurement of atmospheric Ox and NO2 based on cavity ring-down spectroscopy

Atmospheric Ox (nitrogen dioxide (NO2) + ozone (O3)) can better reflect the local and regional change characteristics of oxidants compared to O3 alone, so obtaining Ox accurately and rapidly is the basis for evaluating the O3 production rate. Furthermore, Ox has proved to be a more representative indicator and can serve as a reflection of pollution prevention efficacy. A portable instrument for measuring atmospheric Ox and NO2 based on cavity ring-down spectroscopy (Ox/NO2-CRDS) was developed in this work. The NO2 concentration is accurately measured according to its absorption characteristic at 407.86 nm. Ambient O3 is converted into NO2 by chemical titration of high concentrations of nitrogen oxide (NO), and the O3 conversion efficiencies obtained are nearly 99%. The detection limit of the Ox/NO2-CRDS system for Ox is 0.024 ppbv (0.1 s), and the overall uncertainty of the instrument is ± 6%. Moreover, the Kalman filtering technique was applied to improve the measurement accuracy of Ox/NO2-CRDS. The system was applied in a comprehensive field observation campaign at Hefei Science Island from 26 to 30 September 2022, and the time concentration series and change characteristics of Ox and NO2 were obtained for five days. The measured Ox concentrations were compared with those of two commercial instruments, and the consistency was good (R2 = 0.98), indicating that this system can be deployed to accurately and rapidly obtain the concentrations of atmospheric Ox and NO2. It will be a useful tool for assessing the atmospheric oxidation capacity and controlling O3 pollution.摘要大气Ox (二氧化氮(NO2)+臭氧(O3))相比于O3能够更好的反应区域氧化剂的变化特征, Ox也是反应大气污染防治效果的一个关键指标. 本研究基于腔衰荡光谱技术研发了一套大气Ox和NO2同步测量系统 (Ox/NO2-CRDS). NO2浓度是利用其在407.86 nm处的特征吸收获取, 环境大气的O3通过高浓度的NO被转化为NO2进行间接测量, O3转化效率高于99%, Ox/NO2-CRDS的系统探测限为0.024 ppbv (0.1 s), 系统总不确定度为± 6%. 该Ox/NO2-CRDS系统成功应用于2022年9月26日–30日的合肥市科学岛综合外场观测中, 获取了连续5天的NO2和Ox的时间浓度序列和变化特征, 并将Ox的测量结果与商业化的设备进行了对比验证, 二者具有较好的一致性 (R2 = 0.98), 表明Ox/NO2-CRDS能够被应用于大气Ox和NO2的高灵敏探测. 未来该系统也将会变成评估大气氧化性以及控制臭氧污染的重要工具.

Atmospheric Oxidation Capacity and Its Impact on the Secondary Inorganic Components of PM2.5 in Recent Years in Beijing: Enlightenment for PM2.5 Pollution Control in the Future

In recent years, the concentrations of PM2.5 in urban ambient air in China have been declining; however, the strong atmospheric oxidation capacity (AOC) represents challenges to the further reduction of PM2.5 concentration and the continuous improvement of ambient air quality in China in the future, since the overall AOC is still at a high level. For this paper, based on ground observation data recorded in Beijing from 2016 to 2019, the variation in AOC was characterized according to the concentration of odd oxygen (OX = O3 + NO2). The concentrations of the primary and secondary components of PM2.5 were analyzed using empirical formulas, the correlation between AOC and the concentrations of secondary PM2.5 and the secondary inorganic components (SO42−, NO3−, NH4+, and SNA) in Beijing were explored, the impact of atmospheric photochemical reaction activity on the generation of atmospheric secondary particles was evaluated, and the impact of atmospheric oxidation variations on PM2.5 concentrations and SNA in Beijing was investigated. The results revealed that OX concentrations reached their peak in 2016 and reached their lowest point in 2019. The OX concentrations followed a descending seasonal trend of summer, spring, autumn, and winter, along with a spatial descending trend from urban observation stations to suburban stations and background stations. The degree of photochemical activity and the magnitude of the AOC have a large influence on the production of atmospheric secondary particles. When the photochemical reaction was more active and the AOC was stronger, the mass concentrations of the secondary generated PM2.5 fraction were higher and accounted for a higher proportion of the total PM2.5 mass concentrations. In the PM2.5 fraction, SNA accounted for 50.7% to 94.4% of the total mass concentrations of water-soluble inorganic ions in the field observations. Higher concentrations of the atmospheric oxidant OX in ambient air corresponded to a higher sulfur oxidation ratio (SOR) and nitrogen oxidation ratio (NOR), suggesting that the increase in AOC could promote the increase of PM2.5 concentration. Based on a relationship analysis of SOR, NOR, and OX, it was inferred that the relationship between OX and SOR and the relationship between OX and NOR were both nonlinear. Therefore, when establishing PM2.5 control strategies in Beijing in the future, the impact of the AOC on PM2.5 generation should be fully considered, and favorable measures should be taken to properly regulate the AOC, which would be more effective when carrying out further control measures regarding PM2.5 pollution.

Secondary aerosol formation drives atmospheric particulate matter pollution over megacities (Beijing and Seoul) in East Asia

Atmospheric particulate matter (PM) pollution in Beijing and Seoul is an urgent concern because of the dense population and the role of the capital city. This study aimed to understand haze formation over East Asia during winter by simultaneously measuring the in situ aerosol chemical composition in the two megacities. During the sampling period, a similar pollution situation characterized by extremely low SO2 (approximately 1 ppbv) and high NOx (approximately 20 ppbv) concentrations and secondary inorganic aerosol (SIA)-dominated PM was found in both cities. Nitrate dominated the inorganic components in the submicron particles in both cities and was more pronounced in Seoul than in Beijing. The enhanced SIA mass concentrations during pollution episodes were observed to be associated with an increased local atmospheric oxidation capacity (indicated by O3+NO2=Ox concentration) and ambient relative humidity under similar stagnant weather conditions. Regarding the thermodynamic equilibrium, abundant aerosol liquid water promoted the partitioning of gaseous HNO3 into its particle phase when pollution events occurred. This result emphasized the importance of local secondary aerosol formation for atmospheric PM pollution in East Asian megacities. The box model simulation of nitrate formation indicated that the homogeneous oxidation of NO2 by OH radicals was the major nitrate formation pathway in both megacities. The downward transport of nitrate from the residual layer also significantly contributed to nitrate concentrations. NOx and volatile organic compounds (VOCs) exhibited a non-linear relationship with nitrate formation. Reducing VOCs concentrations was an efficient approach to mitigate nitrate in both megacities. A reduction of more than 50% in NOx concentrations was required for the effective reduction of nitrate. This study highlighted that Beijing and Seoul were experiencing similar PM pollution situations, and nitrate reduction should be considered to improve their air quality.

Relationship of Surface Ozone (O3) with its precursors and meteorological parameters over New Delhi, India

In the present study, continuous measurements of Surface Ozone (O3), Oxides of Nitrogen (NOx (NO+ NO2)), and carbon monoxide (CO), monitored at five different locations in Delhi National Capital Region have been studied for the period 2013 – 2019. The five monitoring locations used are namely IMD Lodi Road, IGI Airport Palam, CV Raman Dheerpur, CRRI Mathura Road, and NCMRWF Noida. The average hourly concentration of O3, NO, NO2, CO, NOx (NO + NO2), and OX(NO2 +O3) are found in the range of 32.44 ppb to 36.57 ppb, 19.46 to 28.09 ppb, 20.83 to 26.89 ppb,1.67 to 1.89 ppm,43.04 to 54.99 ppb, and 54.06 to 60.99 ppb respectively during the study period. Diurnal variation of NOx and CO Concentrations show higher values during the morning (0600-0900h) and late evening (1900-2400h) hours while the highest concentrations of ozone have been observed during afternoon hours. The relationship between NO, NO2, and surface O3 as a function of NOx has also been examined during daylight hours (0500hrs IST to 1900 hrs IST) and chemical coupling of the three species i.e. NO, NO2 and O3 have been studied. The ground-level concentration of Ozone has been found to decrease with increasing NOx concentration during the daytime. The variations in concentrations of oxidants (NO2 + O3) with the concentration of [NOx] have been studied to examine the contributing pollution sources of oxidants at all the study sites. The average rate of change of O3 concentrations (dO3/dt) has been examined at all five locations. The monthly and diurnal variation of oxidants [OX] at all the study locations has shown a strong positive correlation with temperature whereas a negative correlation with humidity.

Size distributions, mixing state, and morphology of refractory black carbon in an urban atmosphere of northeast Asia during summer

Black carbon (BC) exerts profound impacts on air quality, human health, and climate. Here, we investigated concentrations and size distributions of refractory BC (rBC) and mixing state and morphology of rBC-containing particles in urban Seoul for 2019 summer. Mass concentrations of rBC ranged from 0.02 μgm−3 to 2.89 μgm−3, and daily maximums of rBC mass, daily minimums of rBC mass median diameter (MMD) (110–130 nm), and shell-to-core ratio (Rshell/core) occurred with NO2 maximums during morning rush hour. As the first report of ground observations on rBC mixing state, these results indicate that vehicle emission is a major local source of rBC in Seoul. MMDs of 127–146 nm and the greatest mass loadings of ≥1 μg m−3 were accompanied by high O3 and PM2.5 concentrations, in contrast to the largest MMDs (135–165 nm) associated with transport from upstream regions.The average Rshell/core was 1.25 for the rBC mass-equivalent diameter (DrBC) of 140–220 nm. Rshell/core increased gradually through the day and was positively correlated with Ox concentration, indicating photochemical aging of rBC particles. Co-emissions of rBC and volatile organic compounds from vehicles facilitated internal mixing during the daytime. However, Rshell/core tended to be low at temperature >∼30 °C, while 58 % of rBC particles with Rshell/core exceeding 1.25 were found at nighttime under relative humidity >75 %. These results demonstrate that the mixing state of freshly-emitted rBC particles was altered through coating by photochemically oxidized vapors during the day and hygroscopic growth at night. Additionally, the delay-time approach revealed rBC morphological characteristics, the most common being the bare type (74 %), and the attached type (6 %) was relatively large in numbers during morning rush hour. Therefore, it is suggested that during summer, rBC particles from traffic emissions should be considered in parallel to winter pollution mitigation strategies in urban atmosphere of northeast Asia.

Abstract 1069: OBT076, a clinical-stage ADC, displays synergy with oxaliplatin and cisplatin in preclinical gastric cancer models

Abstract CD205 is a transmembrane glycoprotein, robustly expressed in malignancies from varied histotypes, making it an ideal target for Antibody Drug Conjugate (ADC) therapy. OBT076 is a novel and selective clinical stage ADC with potent activity against CD205-positive liquid and solid tumors. We explored the cellular cytotoxicity profile of combination chemotherapy with OBT076 and two standard-of-care platinum-based compounds, Oxaliplatin (Ox) and Cisplatin (Cis), in preclinical gastric, pancreatic and colorectal cancer models. A panel of gastric cancer and other solid tumor cell lines were selected, based on mRNA data, for CD205 expression. This was confirmed using flow cytometry. The cell lines were assessed for susceptibility to monotherapy with OBT076, Ox and Cis. Cells lines displaying positive cytotoxic responses were assessed for susceptibility to combination chemotherapy by first treating cells with a single dose of OBT076 for 72 hours, leading to 20% growth inhibition (IC20), and subsequently with either Ox or Cis for 48 hours (OBT-Ox and OBT-CIS, respectively). The ATP-dependent fluorescence-based cellular viability system cell titer-glo was used as the cytotoxic readout. In our preclinical gastric cancer model, pre-treatment with OBT076 followed by either Ox or Cis displayed synergistic combination effects, reducing the half-maximal inhibitory concentration (IC50) of Ox and Cis by 40- and 10-fold respectively. The resultant cellular cytotoxicity of OBT-Ox and OBT-Cis combination therapy was higher compared to monotherapy with either agent. Moreover, while monotherapy with Ox was less potent than with Cis, OBT-Ox achieved similar potency to OBT076-Cis. For colorectal and pancreatic cancer models, the effects were less pronounced: OBT076-combination therapy increased Platinum sensitivity by 2 to 5 times. No synergistic effects were observed when the treatment order was reversed. These results and those from ongoing in vivo studies in gastric cancer models will be discussed. In summary OBT076, a clinical stage ADC displays synergistic anti-tumor effects in preclinical gastric cancer models, when used in combination with Ox or Cis. OBT076 is currently being evaluated in the gastric clinical population where Platinum-based therapies remain the mainstay of treatment. Citation Format: Arnima Bisht, Murray Cox, Chander Sekhar Peddaboina, Michael Crocamo, Abderrahim Fandi, Christian Rohlff. OBT076, a clinical-stage ADC, displays synergy with oxaliplatin and cisplatin in preclinical gastric cancer models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1069.

Impact of regional transport on total OX (NO2+ O3) concentrations observed at a tropical rural location

In general, local emissions and long-range transport will dictate the pollution levels over a given place. The former source will be based on the location whether it is urban/rural but there are no boundaries to the latter source. During most of the time in a year, long-range transport will decide the pollution levels. Here we present the experimental evidence for regional (long-range) transport impacts on the total OX (NO2 + O3) concentration at a tropical rural location. Two major independent events of the year 2020 in India, the COVID-19 lockdown and Deep depression in Bay of Bengal (BoB2) have been used to demonstrate the known fact of mixing of aged and freshly emitted ozone precursors on the total OX concentration and their influence on observed total OX. COVID-19 lockdown event happened in the summer season whereas, the BoB2 event happened during the post-monsoon period. Air mass transport during these events at the observational site is completely different which brings the regional transport influence. Further, total OX observed has no local contribution and is controlled entirely by the regional contribution. These observations have been well supported by the CWT analysis and wind circulation patterns during the events. This study provides a clear demonstration of the regional pollution transport influence on the total OX at a rural environment (which control the oxidative capacity of the rural atmosphere). Thus, caution is advised in designating the location as rural/urban based on local emissions alone.

Comparisons of Combined Oxidant Capacity and Redox-Weighted Oxidant Capacity in Their Association with Increasing Levels of COVID-19 Infection

Background: Ozone (O3) and nitrogen dioxide (NO2) are substances with oxidizing ability in the atmosphere. Only considering the impact of a single substance is not comprehensive. However, people’s understanding of “total oxidation capacity” (Ox) and “weighted average oxidation” (Oxwt) is limited. Objectives: This investigation aims to assess the impact of Ox and Oxwt on the novel coronavirus disease (COVID-19). We also compared the relationship between the different calculation methods of Ox and Oxwt and the COVID-19 infection rate. Method: We recorded confirmed COVID-19 cases and daily pollutant concentrations (O3 and NO2) in 34 provincial capital cities in China. The generalized additive model (GAM) was used to analyze the nonlinear relationship between confirmed COVID-19 cases and Ox and Oxwt. Result: Our results indicated that the correlation between Ox and COVID-19 was more sensitive than Oxwt. The hysteresis effect of Ox and Oxwt decreased with time. The most obvious statistical data was observed in Central China and South China. A 10 µg m−3 increase in mean Ox concentrations were related to a 23.1% (95%CI: 11.4%, 36.2%) increase, and a 10 µg m−3 increase in average Oxwt concentration was related to 10.7% (95%CI: 5.2%, 16.8%) increase in COVID-19. In conclusion, our research results show that Ox and Oxwt can better replace the single pollutant research on O3 and NO2, which is used as a new idea for future epidemiological research.

Seasonality and reduced nitric oxide titration dominated ozone increase during COVID-19 lockdown in eastern China

With improving PM2.5 air quality, the tropospheric ozone (O3) has become the top issue of China’s air pollution control. Here, we combine comprehensive observational data analysis with models to unveil the contributions of different processes and precursors to the change of O3 during COVID-19 lockdown in the Yangtze River Delta (YRD), one of the most urbanized megacity regions of eastern China. Despite a 44 to 47% reduction in volatile organic compounds (VOCs) and nitrogen oxides (NOx) emissions, maximum daily 8-h average (MDA8) ozone concentrations increase from 28 ppbv in pre-lockdown to 43 ppbv in lockdown period. We reproduce this transition with the WRF-Chem model, which shows that ~80% of the increase in MDA8 is due to meteorological factors (seasonal variation and radiation), and ~20% is due to emission reduction. We find that daytime photochemistry does not lead to an increase but rather a decrease of daytime O3 production during the lockdown. However, the reduced O3 production is overwhelmed by the weakened nitric oxide (NO) titration resulting in a net increase of O3 concentration. Although the emission reduction increases O3 concentration, it leads to a decrease in the Ox (O3 + NO2) concentration, suggesting reduced atmospheric oxidation capacity on a regional scale. The dominant effect of NO titration demonstrates the importance of prioritizing VOCs reduction, especially from solvent usage and the petrochemical industry with high emission ratios of VOCs/NOx.

The low-cost and high-efficient photoreduction of Cr(VI) by oxalic acid synergized with the iron-loaded rice straw

In the view of the possible synergy between the Fe(III)-induced photochemical reduction and the photocatalytic role of agriculture waste rice straw(RS), the iron-loaded rice straw (Fe-RS) was firstly prepared and successfully used in the photoreduction removal of Cr(VI) by oxalic acid (Ox). 1 mM of Cr(VI) in aqueous solution was completely removed in 6 min in Fe-RS/Ox/UV system. The Cr(VI) removal of Fe-RS/Ox/UV system was investigated through the effect of Ox concentration, initial Cr(VI) concentration, Fe-RS dosage and reusability of Fe-RS. The Cr(VI) removal mechanism of Fe-RS/Ox/UV system was discussed in detail, and the role of Fe-RS in Fe-RS/Ox/UV system was further revealed. The results showed that Fe-RS significantly enhanced the Cr(VI) photoreduction by Ox, and the loaded Fe component and the contained Si components on Fe-RS played an important synergized photocatalytic action for Cr(VI) removal in Fe-RS/Ox/UV system. The continuously photo-generated Fe(II) and CO2·- in the system reduced most Cr(VI). The separated electron (e-) and the produced CO2·- from the oxidation of Ox by hole (h+), which was due to the photocatalyzed SiO2 on Fe-RS, reduced some Cr(VI).

Toward a better understanding of ferric-oxalate complex photolysis: The role of the aqueous/air interface of droplet

In this work, the photo reactivity of ferric oxalate (Fe(III)-Ox) complex in atmospheric particles was investigated. Raman spectroscopy was used to explore the mechanism and kinetics of Fe(III)-Ox photolysis occurring at the aqueous/gas interface, inside the droplet and in bulk solution. Ferrous carbonate (FeCO3) was detected indicating that carbonate ion (CO32−) formed inside the droplets would compete with oxalate ligands for iron complexation. A higher concentration of photoproduct Fe(II)-Ox was observed at the surface and inside of the droplets than in bulk solution. In particular, Fe(III)-Ox on the droplet surface was quickly reduced with light and Fe(II)-Ox concentration gradually decreased with irradiation time. The evolution of Fe(II)-Ox concentration was similar inside the droplet and in bulk solution with a trend of first increasing and then gradually decreasing during irradiation time. Although FeCO3 would hinder Fenton intermediate reaction, the photolysis rate of Fe(III)-Ox in droplets was almost two orders of magnitude times faster than that observed during bulk experiment. In general, the photolysis mechanism and kinetics of Fe(III)-Ox in aqueous/air interface, inside of droplet and bulk solution were distinct, and the production of oxide species from the atmospheric Fe(III)-Ox droplets was underestimated.

The highly enhanced Cr(VI) photoreduction removal by oxalic acid coordinated with iron-loaded waste Loofah

In order to remove high toxic Cr(VI) from the water with low cost and high efficiency, iron-loaded Loofah (Loofah-Fe) was prepared from agriculture waste Loofah and was applied in the Cr(VI) photoreduction remvoal by oxalic acid (Ox). The Cr(VI) removal of Loofah-Fe/Ox/UV system were investigated by the effect of initial Cr(VI) concentration, Ox concentration and Loofah-Fe dosage. The Cr(VI) removal mechanism in Loofah-Fe/Ox/UV system were discussed through the study of initial pH, the change (pH, Ox concentration, Fe(II) and Fe(III) concentration) in solution during the reaction, and the free radicals scavenging test. The role of Loofah-Fe in Loofah-Fe/Ox/UV system was further deduced by the analysis of XPS, EIS and Mott-Schottky. The results showed that Loofah-Fe remarkably enhanced the Cr(VI) photoreduction by Ox, 1 mM of Cr(VI) in aqueous solution was completely removed in 30 min by Loofah-Fe/Ox/UV system at pH = 3.0. The loaded Fe(III) and the contained SiO2 on Loofah-Fe played an important synergized photocatalytic role for Cr(VI) removal in Loofah-Fe/Ox/UV system. Fe(II) and CO2·-, which was continuously generated by photoactive Fe(III)-(C2O4)3 formed between Ox and Fe(III) dissolved from Loofah-Fe, reduced a large amounts of Cr(VI) in solution. The separated electron (e−) and the produced CO2·-, generated from the oxidized Ox by the hole (h+) through photoactive SiO2 on Loofah-Fe, also reduced part of Cr(VI).

Contrasting Trends of Surface PM2.5, O3, and NO2 and Their Relationships with Meteorological Parameters in Typical Coastal and Inland Cities in the Yangtze River Delta.

The contrasting trends of surface particulate matter (PM2.5), ozone (O3), and nitrogen dioxide (NO2) and their relationships with meteorological parameters from 2015 to 2019 were investigated in the coastal city of Shanghai (SH) and the inland city of Hefei (HF), located in the Yangtze River Delta (YRD). In both cities, PM2.5 declined substantially, while O3 and NO2 showed peak values during 2017 when the most frequent extreme high-temperature events occurred. Wind speed was correlated most negatively with PM2.5 and NO2 concentrations, while surface temperature and relative humidity were most closely related to O3. All of the studied pollutants were reduced by rainfall scavenging, with the greatest reduction seen in PM2.5, followed by NO2 and O3. By contrast, air pollutants in the two cities were moderately strongly correlated, although PM2.5 concentrations were much lower and Ox (O3 + NO2) concentrations were higher in SH. Additionally, complex air pollution hours occurred more frequently in SH. Air pollutant concentrations changed more with wind direction in SH. A more effective washout effect was observed in HF, likely due to the more frequent strong convection and thunderstorms in inland areas. This research suggests pertinent air quality control measures should be designed accordingly for specific geographical locations.

Long-term trend of ozone in southern China reveals future mitigation strategy for air pollution

The 14-year trends of surface ozone were examined using observations from 12 urban sites and 4 regional sites over the Pearl River Delta (PRD) region in China over the 2006–2019 period. Surface ozone exhibits upward trends in the range of 0.28–1.02 ppb yr−1 at urban sites and mixed trends in the range of −0.29 – 0.21 ppb yr−1 at regional sites. Meanwhile, surface Ox (Ox = O3+NO2) mixing ratios exhibit downward trends at 9 urban sites and 3 regional sites in the range of −0.01 to −0.54 ppb yr−1, revealing that the ozone rise at urban sites is predominantly attributed to the reduced titration effect by nitric oxide (NO). The further decline of surface NO2 mixing ratios could drive the decreases in Ox mixing ratios and the increases in ozone mixing ratios at urban sites. In addition, surface Ox concentrations show a good correlation with aerosol concentrations, implying the dominant contributions of secondary production to aerosol and the consistent control strategies of ozone and aerosol pollution in PRD. For the abatement of ozone pollution, our results highlight the synergistic control of key precursors including nitrogen oxides and volatile organic compounds to counteract the reduced NO titration effect by inhibiting the photochemical production of ozone. At last, we also highlight the importance of establishing more regional sites in comprehensively assessing spatiotemporal changes in surface air pollutants in China.

Solar energy conversion to electricity by Tris (2,2′-bipyirdyl) ruthenium (II) chloride hexahydrate-diethyl ammonium tetrachloroferrate-oxalic acid photogalvanic cell: Statistical analysis

Surfactants are commonly used in photogalvanic cells (PGC) while few studies have reported on the application of ionic liquids (IL), although it is considered as green solvents. In this work, diethyl ammonium tetrachloroferrate (DATF) was synthesized by two-step method. The chemical structure of the DATF was studied using FTIR and 1H NMR spectra. PGC can be pronounced as an electrochemical cell in which the change in both voltage and current produced from photochemical changes in the solutions during the oxidation-reduction reaction. A new system of synthetic solution contains Tris (2,2′-bipyridyl) Ruthenium (II) chloride hexahydrate (TBRC) photosensitizer dye, Oxalic acid (OX) reductant, and DATF was used under artificial illumination. The used system shows electrical cell performance of maximum power (PPP) 96.2 μW, short-circuit current (iSC) 370 μA, open circuit potential (VOC) 650 mV, conversion efficiency (η) 1.9 %, and fill factor (FF) 0.4. The storage capacity (t0.5) of the cell has recorded 105 min in dark. Different parameters affect the cell performance as were studied. The cell parameters and a preliminary mechanism of the production of electrical energy in PGC were also proposed. Response surface methodology (RSM) approach was used to optimize the process parameters and identifying the optimal conditions of the effect of pH, TBRC, DATF, and OX concentrations. Central composite experimental design (CCD) with response surface and optimization was used to predict the photopotential, photocurrent, Ppp and η. Statistical analysis of variance (ANOVA) was carried out to identify the adequacy of the developed model and revealed good agreement between the experimental data and proposed model. The observed R2 value, adj. R2, pred. R2, and “F-values” indicate that the developed models are significant.

Impacts of synoptic circulations on summertime ozone pollution in Guanzhong Basin, northwestern China

The Guanzhong Basin (GZB) has long been considered the most polluted city cluster in northwestern China with exposure to unhealthy levels of ozone (O3) in summer, which is strongly associated with adverse meteorological conditions and massive percussor emissions. In this study, four typical synoptic circulation types (CTs) were identified in the summers of 2014–2019 via the T-mode PCA classification method, including two polluted (southeast high and northeast ridge), one lightly polluted (east high), and one clean (northwest high) type. The impact of CTs on the atmospheric transport and diffusion conditions gradually weakened with decreasing altitude, while local circulation played a critical role near the ground, resulting in dominant northeast and southwest surface winds, high proportions of stagnation conditions (>50%). In particular, the meteorological conditions under the southeast high-type were marked by increasing influences of southerly airflow, high temperatures, low humidities, and the worst diffusion conditions, all of which were favorable for the local production of O3. While, the northeast ridge-type was characterized by easterly airflows in the upper air, which transported O3 and its precursors from upwind polluted areas. The regional transport model CAMx was applied to quantify the O3 sources over the GZB. The heaviest O3 pollution occurred under the southeast high-type, associated with the fast chemical formation rates and significant contributions from local emissions. The enhanced atmospheric oxidative capacity under the southeast high-type was suggested by elevated O3 and Ox (O3 + NO2) concentrations in the atmospheric boundary layer. Although the northeast ridge- and east high-type circulations led to similar chemical productions of O3, the cross-regional transport of O3 was increased under the northeast ridge-type and resulted in severe O3 pollution. This would serve to maximize regional O3 reduction under varying synoptic circulation conditions.

Intrapartum transfer of oxytocin across the human placenta: An ex vivo perfusion experiment

IntroductionInvestigation of the maternal to fetal transfer of oxytocin across the dually perfused term human placenta. MethodsHuman placentae obtained from term singleton pregnancies were utilized in a dual recirculating model of ex vivo placental perfusion. Six placentae from women delivering by elective cesarean at term were perfused, one blank and five with the test substance synthetic oxytocin (0.8 ng/mL) (OX) added to the maternal perfusate for 180 min. Antipyrine was used as positive control to validate overlap of the maternal and fetal circuits. The concentration of OX was determined by radioimmunoassay. ResultsA fall in maternal concentration of OX was seen throughout the experiment. At 90 min of perfusion a state of equilibrium was reached between maternal and fetal concentrations; however after 180 min the fetal concentration of OX was higher than that of the maternal. 31 % of the test substance was accounted for at the end of the experiment - suggesting OX protein binding and a high degree of oxytocinase activity. DiscussionThe ex vivo perfusion experiments revealed low transfer of OX to the fetal circuit below physiologically relevant concentrations.