Low Ozone Research Articles

Oxidation and degradation of nitrobenzene by ozone micro-nano bubbles

The remediation of ozone oxidation to nitrobenzene (NB) contaminated groundwater has limitations such as low ozone solubility and poor gas transmission capacity. In this paper, we combine the ozone oxidation and the micro-nano bubbles (MNBs) and investigate the oxidation of the degradation of NB using a semi-continuous experimental approach. The experimental results show that the degradation efficiency of NB by ozone MNBs system (98.69%) is significantly higher than that of traditional ozone oxidation. The presence of MNBs significantly increase the rate of ·OH, ·O2– and 1O2 production compared to large bubbles produced by ozone aeration. This is due to OH– adsorbed at the interface will accelerate the conversion of ozone to ·OH during bubble rupture. And conversion between O3,·OH, ·O2– and 1O2。 The degradation of NB in ozone MNBs could be described by quasi-first-order kinetics. The degradation kinetics of ozone MNBs are obviously affected by the initial concentration of NB, the initial pH of the reaction system, salinity, gas species and flow rate. Oxidative degradation products (p-benzoquinone, phenol, o-nitrophenol, p-nitrophenol, aniline, acetic acid, NO3–, etc.) have been identified by GC–MS, IC, UV–Vis. They show that the degradation results from the attack of the aromatic ring and –NO2 of NB through nitrification, free radicals and O3. This research introduces a novel approach for degrading NB and offers crucial insights into the degradation of organic substances using MNBs.

Ozone Detector Based on Ultraviolet Observations on the Martian Surface

Ozone plays a key role in both atmospheric chemistry and UV absorption in planetary atmospheres. On Mars, upper-tropospheric ozone has been widely characterized by space-based instruments. However, surface ozone remains poorly characterized, hindered by the limited sensitivity of orbiters to the lowest scale height of the atmosphere and challenges in delivering payloads to the surface of Mars, which have prevented, to date, the measurement of ozone from the surface of Mars. Systematic measurements from the Martian surface could advance our knowledge of the atmospheric chemistry and habitability potential of this planet. NASA’s Mars 2020 mission includes the first ozone detector deployed on the Martian surface, which is based on discrete photometric observations in the ultraviolet band, a simple technology that could obtain the first insights into total ozone abundance in preparation for more sophisticated measurement techniques. This paper describes the Mars 2020 ozone detector and its retrieval algorithm, including its performance under different sources of uncertainty and the potential application of the retrieval algorithm on other missions, such as NASA’s Mars Science Laboratory. Pre-landing simulations using the UVISMART radiative transfer model suggest that the retrieval is robust and that it can deal with common issues affecting surface operations in Martian missions, although the expected low ozone abundance and instrument uncertainties could challenge its characterization in tropical latitudes of the planet. Other space missions will potentially include sensors of similar technology.

Ozone: complicated effects in central nervous system diseases.

Oxidative stress is closely related to various diseases. Ozone can produce redox reactions through its unique response. As a source of the oxidative stress response, the strong oxidizing nature of ozone can cause severe damage to the body. On the other hand, low ozone concentrations can activate various mechanisms to combat oxidative stress and achieve therapeutic effects. Some animal experiments and clinical studies have revealed the potential medical value of ozone, indicating that ozone is not just a toxic gas. By reviewing the mechanism of ozone and its therapeutic value in treating central nervous system diseases (especially ischemic stroke and Alzheimer's disease) and the toxic effects of ozone, we find that ozone inhalation and a lack of antioxidants or excessive exposure lead to harmful impacts. However, with adequate antioxidants, ozone can transmit oxidative stress signals, reduce inflammation, reduce amyloid β peptide levels, and improve tissue oxygenation. Similar mechanisms to those of possible new drugs for treating ischemic stroke and Alzheimer's disease indicate the potential of ozone. Nevertheless, limited research has restricted the application of ozone. More studies are needed to reveal the exact dose-effect relationship and healing effect of ozone.

Low ozone concentrations do not exert cytoprotective effects on tamoxifen-treated breast cancer cells in vitro.

Medical treatment with low ozone concentrations proved to exert therapeutic effects in various diseases by inducing a cytoprotective antioxidant response through the nuclear factor erythroid derived-like 2 (Nrf2) transcription factor pathway. Low ozone doses are increasingly administered to oncological patients as a complementary treatment to mitigate some adverse side-effects of antitumor treatments. However, a widespread concern exists about the possibility that the cytoprotective effect of Nrf2 activation may confer drug resistance to cancer cells or at least reduce the efficacy of antitumor agents. In this study, the effect of low ozone concentrations on tamoxifen-treated MCF7 human breast cancer cells has been investigated in vitro by histochemical and molecular techniques. Results demonstrated that cell viability, proliferation and migration were generally similar in tamoxifen-treated cells as in cells concomitantly treated with tamoxifen and ozone. Notably, low ozone concentrations were unable to overstimulate the antioxidant response through the Nfr2 pathway, thus excluding a possible ozone-driven cytoprotective effect that would lead to increased tumor cell survival during the antineoplastic treatment. These findings, though obtained in an in vitro model, support the hypothesis that low ozone concentrations do not interfere with the tamoxifen-induced effects on breast cancer cells.

Enhancing ozonation technology: A case study on full-scale airlift reactor upgrades in the existing wastewater treatment plant's ozonation tank using CFD

Traditional pneumatic bubble column reactors (PBCRs) in wastewater treatment often have limitations in ozone distribution and disinfection efficacy. This study introduces an optimized Airlift Reactor (ALR) design, enhanced with Computational Fluid Dynamics (CFD), to improve ozone contact time and uniform distribution. Tailored for the SONATRACH GP1/Z Complex in Bethioua, Algeria, the ALR addresses the treatment needs of the facility's WWTP Phase-1, handling domestic wastewater. The study is unique for its full-scale implementation of the ALR, as previous research focused on lab-scale cases. Advanced CFD simulations optimized the ALR design, focusing on baffle configurations to enhance ozone disinfection. The upgraded One Side Baffled Airlift (OS-BALR) variant achieved a Total Coliform inactivation rate of 94.52 %, compared to 74 % with the traditional design. The OS-BALR also demonstrated a lower ozone mass transfer coefficient (KLa) of 0.0048 s−1, improving treatment efficiency and reducing energy consumption. While the Baffled Bubble Column (BBC) reactor showed a higher KLa of 0.0055 s−1 and a microbial removal efficacy of 96.12 %, it is more energy-intensive. This study advances wastewater treatment by bridging innovation with industrial application, contributing to sustainable wastewater management practices globally.

Preserving the Aromatic Profile of Aged Toma Piemontese PDO Cheese with Gaseous Ozone Technology: A Quality Assessment via SPME-GC–MS/E-Nose

The efficacy of low gaseous ozone concentrations (300 ppb and 400 ppb) in controlling spoilage microflora and preserving the quality of the aged Toma Piemontese PDO cheese was explored. The research integrates consumer tests, Gas Chromatography-Mass Spectrometry (GC-MS) with Solid phase Microextraction (SPME) fiber and Electronic Nose (e-nose) analysis to conduct a detailed assessment of the cheese's aromatic composition. Results indicate that low ozone concentrations significantly affected spoilage microflora, preserving the overall quality. Through GC-FID (Flame Ionization Detection) analysis, 22 of all identified compounds by GC-MS were quantified, including ethyl acetate (sweety), diacetyl and acetoin (buttery). Compared with the untreated sample, ozone treatments maintained the distinctive characteristics of Toma Piemontese PDO cheese, reducing the formation of off-flavors-related compounds (i.e., ethanol). Moreover, ozone-treated samples correlated with positive aroma scores given by consumers. However, sensory perception involves complex interactions among aroma compounds, highlighting the importance of advanced approaches. The utilization of a 12-sensor Quartz Microbalance (QMB) e-nose played a crucial role in identifying subtle differences in aroma, contributing to a more nuanced understanding of ozone treatments on the cheese's sensory profile. In conclusion, this research demonstrates the potential of ozone technology as a viable and effective method for improving the quality of aged Toma Piemontese PDO cheese.

Characterization and effectiveness of a miniaturized dielectric barrier discharge module for air disinfection

Effective inactivation of airborne pathogens is crucial for air quality control and the prevention of infectious diseases, especially in indoor human-living environments. In this work, a novel air disinfector based on surface dielectric barrier discharge (DBD) plasma was proposed. The discharge characteristics and the disinfection performance of the disinfector were investigated under different applied voltages, airflow rates, and humidity. The used DBD mainly works in the O3-dominant product mode with a discharge power of 1–3 W. The decreases in N2(C-B) emission intensity, ozone, discharge power, and discharge current with the increasing airflow humidity were observed. Humidity was found to be the most pronounced factor promoting the single-pass disinfection efficiency. The Z value reached 0.32 l/J for relative humidity of 70%–80%. Additionally, ozone and ions were found to play a minor role in plasma-mediated bacterial inactivation. The antibacterial effectiveness of the disinfector was also validated by 2-h circulating disinfection experiments. Efficiency was maintained above the disinfection level (>99.9%) after a 5000-h continuous running. Meanwhile, the ozone emission was below the standard limit requirements. The proposed air disinfector is promising for household use with the advantages of small size, bacterial inactivation capability, low ozone emission, and high perceptibility.

Retrieval of upper stratospheric ozone profiles from SCIAMACHY Hartley-Huggins limb scatter spectra using WMART

ABSTRACT The hyperspectral SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) instrument, launched by Envisat in March 2002, measures atmospheric scattered radiance within the ultraviolet (UV) to near infrared range and has three geometric observation modes: nadir, occultation, and limb. This study describes a retrieval scheme to obtain middle and upper stratospheric ozone profiles from SCIAMACHY limb-scattered solar radiance. Owing to the low ozone concentration at high altitudes and rapid changes in ozone absorption cross-sections in the Hartley – Huggins band, a fundamental objective of this study was to establish a simple and effective retrieval scheme to derive reliable ozone profiles at high altitudes from UV spectral bands. In this study, short UV wavelengths of 302, 312, and 322 nm and a long wavelength of 331 nm were used for wavelength pairing to simplify the retrieval algorithm. Moreover, we employed the weighted multiplicative algebraic reconstruction technique (WMART), which is straightforward to understand, and easy to implement, combined with a radiative transfer model (i.e. SCIATRAN), and produced stable results. The retrieval error estimates for the upper stratosphere were provided, and the total retrieval error of the ozone profile was usually < 18% in the altitude range of 30–53 km. The results were compared with the SCIAMACHY v3.5 product and validated against profiles derived from Optical Spectrometer and InfraRed Imaging System (OSIRIS) v7.1, and Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) v4.0 for 30–53 km altitude. The retrieved ozone profiles agreed with data from SCIAMACHY v3.5 within − 10%–5%, except at an altitude of 45 km, where the bias became larger (approximately −15%). The comparison of retrieved profiles with OSIRIS v7.1 showed differences within ± 10% for 30–53 km altitude. The errors were mostly less than − 5% below 43 km compared with ACE-FTS v4.0, but there was a large negative deviation in the upper stratosphere.

Optical study on the effect of ozone addition on a diesel/ammonia dual fuel engine with pilot injection

Influenced by the concept of carbon neutrality, ammonia is gaining widespread attention in the transport sector as a zero-carbon fuel. Diesel/ammonia dual fuel engines can achieve stable combustion of ammonia and reduce carbon emissions. To further enhance the low load combustion performance of a diesel/ammonia dual fuel engine, the effect of ozone addition on in-cylinder combustion and flame development was investigated based on an optical engine. Beyond that, ozone addition on pure diesel was also tested to understand the effect of ozone addition on diesel combustion enhancement in diesel/ammonia reactivity controlled compression ignition (RCCI) mode. The results show that the addition of ozone significantly advances the ignition phase, increases the flame area and brightness, and results in a growth in flame luminescence intensity along the radial length and closer to the center of the view field for diesel/ammonia RCCI combustion. In addition, chemical kinetic analysis shows that diesel/ammonia combustion requires higher ozone concentrations to overcome the inhibitory effect of ammonia to reach the upper limit of the promotional effect on the ignition phase and indicated mean effective pressure (IMEP), due to the large amount of OH consumed by ammonia compared to pure diesel. The promotional effect of added ozone on IMEP is similar for different pilot injection ratios (PIRs). At a low PIR and high ozone concentration, the diesel/ammonia RCCI engine achieves the highest IMEP, indicating that ozone addition combined with optimization of diesel injection parameters contributes to improve the performance of the diesel/ammonia RCCI engine at low loads.

Self-enhanced oxidation of resistant monocyclic aromatic compounds during ozone treatment: Applicability in groundwater remediation

The Peroxone process—which utilizes a combination of ozone and hydrogen peroxide to generate hydroxyl radicals—is frequently used in groundwater remediation to effectively remove ozone-resistant contaminants. However, some monocyclic aromatic compounds with low ozone reactivity have been found to be removed by ozone solely (without the need for hydrogen peroxide) through a self-enhanced mechanism. This self-enhanced removal occurs when the interaction of ozone with hydroxide ion generates sufficient amount of hydroxyl radicals, initiating a radical reaction that subsequently propagates through the degradation intermediates. This study leverages the self-enhanced degradation mechanism for the treatment of ozone-resistant compounds during groundwater remediation. Key environmental conditions, including water alkalinity and contaminant concentration, were investigated for their effect on the self-enhanced degradation of para-chloro benzoic acid (pCBA), which served as a model for ozone-resistant compounds. High pCBA removal was observed during ozonation in the concentration range of 0.5–5 μM, where the decay kinetics of pCBA and ozone significantly dependent on the initial pCBA concentration. Furthermore, decreased pCBA removal was noted in water matrices with increased alkalinity, largely due to the scavenging of OH radicals by carbonate species. Finally, pCBA removal was investigated in natural groundwater, where co-existing substances acted as ozone/radical scavengers, leading to reduced pCBA removal. Overall, this study highlights the importance of the self-enhanced removal mechanism of monocyclic aromatic contaminants when treating water with high contamination levels and low-to-moderate alkalinities.

Impacts of stratosphere-to-troposphere transport on tropospheric ozone in southeastern China: insights from ozonesonde observations

Tropospheric ozone pollution poses a major environmental challenge in China. As its primary natural source, Stratosphere-to-Troposphere Transport (STT) has been recognized as a significant contributor to tropospheric ozone in western, northeastern, and eastern China. However, the extent of STT’s influence on southeastern China has been less studied due to data limitations. Using a recently available one-year dataset of ozonesonde observations from a regional background station, we find that STT contributes significantly to tropospheric and surface ozone elevation in southeastern China. Our results show that STT plays a more substantial role in shaping tropospheric ozone during spring than previously believed, accounting for over 30% of ozone concentrations above 4 km. Without the stratospheric contribution, the spring seasonal peak almost disappears. STT can also significantly influence ozone concentrations at the surface. For example, a distinct ozone profile was observed on 4 May 2022, with a notable increase in tropospheric ozone. This tropospheric ozone increase was caused by a STT event triggered by a robust horizontal trough and subsequent southward movement of subtropical jets in the upper troposphere. According to a stratospheric tracer derived from an atmospheric chemistry model, this STT event contributed to 25%–30% of the surface ozone increase. Overall, this study highlights the important role of STT in driving tropospheric ozone variations, even in regions with comparatively lower ozone levels in southeastern China.

Methods of Improving Thermal Performance of Vapour Compression Based Refrigeration System Through Eco Friendly Refrigerants to Reduce Their Environmental Impact

Tetrafluoroethane (CF3CH2F), an HFC refrigerant, is also known as R134a. It is safe for normal handling because it is neither poisonous, flammable, nor corrosive. After it was discovered recently that R-134a contributes to global warming, the European Union forbade its use in brand-new automobiles starting in 2011. Worked on a vapour compression-based refrigeration system, utilised hydrocarbon (HC) refrigerants which were examined for their energetic and exergetic performance. In this investigation, pure Tetrafluoroethane (CF3CH2F) from the R134a family of HFCs was used for a theoretical analysis, along with other refrigerants which were eco-friendly and had a lower environmental impact( low Global Warming Potential and Ozone Depletion Potential) :trans-1,3,3,3- Tetrafluoroprop -1-ene( R1234 ze (Z), R1234ze (E), (Z)-1-Chloro-2,3,3,3-Tetrafluoropropane (R1224YD (Z)), Fluoroethene (R1141),3,3,3-Trifluoroprop-1-ene (R1243 ZF).The thermodynamic equations of the refrigerants were solved for analysis using the Engineering equation solver application. It was concluded that R1234ZE (Z) is the most effective refrigerant.

Synthetically impacts of the topography and typhoon periphery on the atmospheric boundary layer structure and special regional pollution pattern of O3 in North China Plain

Westerly warm advection from the Loess Plateau to the over layer of North China Plain (NCP) suppresses the mixed layer during the daytime in summer, having already be confirmed as an important formation mechanism of regional O3 pollution all over NCP. However, when NCP was simultaneously affected by the westerly warm advection from the Loess Plateau and the typhoon periphery airflow from the Western Pacific tropical cyclone system, a rare pollution pattern of surface O3 was detected, characterized by a very low ozone pool in Beijing (LOP-BJ) contrast to much higher O3 in surrounding areas. To explore the causes and deep formation mechanism to this special pollution phenomenon, regional pollution characteristics of O3, characteristics of the atmospheric boundary layer (ABL) structure and vertical airflows affected by different weather systems were analyzed based on the analysis of observations and three dimensional simulations. It was found that the synthetic impacts of the topography and the typhoon peripheral flow promoted the stabilization of the ABL and introduced a nearly isolated air mass in terms of both thermodynamic and dynamic structures within ABL in Beijing region. In the stable and isolated ABL air masses, the significant lower ozone near the ground was primarily attributed to the strong loss by NO titration consumption from local excessive emissions and extremely weak transport contributions from surrounding areas. The conclusion was also confirmed by the integrated process rate (IPR) analysis results of contributions from chemistry tendency (CHEM) and total transport tendency (TRAN) to surface ozone. Our work insight the understanding of the formation mechanism of regional ozone pollution and improve the forecasting capabilities under comprehensive weather conditions over NCP.

Distribution of ozone, carbon monoxide and oxides of nitrogen over an urban location in the foothills of the North-Western Himalayas

Increasing anthropogenic activities and biomass burning events over the Northern Indian region severely affect the pristine environment of North-Western Himalayas. To investigate their influence in this data sparse region, continuous monitoring of O3, CO and NOx are made during January 2018 to December 2019 over Dehradun, an urban location in the foothills of North-western Himalayas. Ozone shows daytime broad peak and CO and NOx show two peaks during morning and evening hours. The maximum daytime ozone is observed during spring with 58.2 ± 2.0 ppbv (56.2 ± 2.7 ppbv) during 2018 (2019). CO and NOx show maximum value during winter and minimum during summer-monsoon. Their concentrations are found to be influenced from stubble burning and forest fire emissions during late spring. WRF-Chem simulations are made with and without biomass burning emissions to quantify the contribution of these emissions on the variability of these gases over Dehradun. Sensitivity simulations reveal that biomass burning over northern Indian region contributed 43 ppbv, 79 ppbv and 1.2 ppbv increase in O3, CO and NOx mixing ratios over Dehradun. In addition, dust storm event in June 2018 contributed for lower ozone levels in 2018 (16.1 ± 9.3 ppbv) and stratosphere troposphere exchange process enhanced surface ozone in June 2019 (53.6 ± 22.3 ppbv).

Low temperature (002)-oriented zinc oxide films prepared using ozone-based spatial atomic layer deposition

In this study, ZnO films are prepared at a low temperature of 150 °C by using spatial atomic layer deposition (sALD) with diethylzinc and ozone as precursor and oxidant. The ozone flow rate is varied to systematically investigate its effect on optical, structural and electrical properties. The experimental results show that the self-limiting surface reactions can occur at the low ozone flow rate of 200 sccm, confirming ALD growth mode. All the ozone flow rates lead to ZnO (002) crystalline orientation, which is difficult to be obtained for conventional water-based ALD ZnO films at the low temperature. The increased ozone flow rate results in an increased amount of oxygen vacancies, enhanced carrier concentration and a reduced stress. The resistivity and carrier concentration can be tuned in the range of 4.75–0.08 Ω-cm and (1.1–5.5) × 1018 cm−3. Finally, the sALD ZnO film on polyethylene terephthalate reveals a high stability in the film property against bending. This study is beneficial for the utilization of ZnO films in optoelectronic devices that demand the (002) preferred orientation, especially under low-temperature conditions.

Antarctic Vortex Dehydration in 2023 as a Substantial Removal Pathway for Hunga Tonga‐Hunga Ha'apai Water Vapor

AbstractThe January 2022 eruption of Hunga Tonga‐Hunga Ha'apai (HTHH) injected a huge amount (∼150 Tg) of water vapor (H2O) into the stratosphere, along with small amount of SO2. An off‐line 3‐D chemical transport model (CTM) successfully reproduces the spread of the injected H2O through October 2023 as observed by the Microwave Limb Sounder. Dehydration in the 2023 Antarctic polar vortex caused the first substantial (∼20 Tg) removal of HTHH H2O from the stratosphere. The CTM indicates that this process will dominate removal of HTHH H2O for the coming years, giving an overall e‐folding timescale of 4 years; around 25 Tg of the injected H2O is predicted to still remain in the stratosphere by 2030. Following relatively low Antarctic column ozone in midwinter 2023 due to transport effects, additional springtime depletion due to H2O‐related chemistry was small and maximized at the vortex edge (10 DU in column).

Comparison of the Climatic Characteristics of Ozone Valley Over the Tibetan Plateau and the Rocky Mountains

AbstractThis study compares the ozone valleys over the Tibetan Plateau (TP) and the Rocky Mountains (RM) using the ERA5 reanalysis data set. The dynamical transport of the ozone over these two regions is analyzed using the Lorenz circulation decomposition method. The ozone content valley over TP is observed around 200–50 hPa (upper troposphere and lower stratosphere, or UTLS), and that over RM is around 300–100 hPa. It is shown that the TP ozone content is smaller than that over RM. By analyzing the spatiotemporal distribution of the ozone content and the general circulation, the anticyclone over Southern Asian (SAH) plays a significant role in existence of the TP ozone valley, and the ozone content flux reaches its maximum in July. Large‐scale terrain and related general circulation determine the ozone valley appearance. Further analysis suggests that stationary transport has a larger impact on the ozone valley formation than the transient transport. The transport by the zonal circulation nearly cancels out most of that by the meridional circulation, due to the fact that the zonal transport magnitude is nearly equal to the meridional transport. The transport center over the RM is much weaker than that over the TP. Furthermore, the contrasts between transient and stationary transports are less evident over RM than over TP. The eddy‐driven stationary ozone transport flux significantly impacts the development of the two low ozone centers across these large terrains.

Interactions between aerosols and surface ozone in arid and semi-arid regions of China.

Atmospheric aerosols affect surface ozone concentrations by influencing radiation, but the mechanism and dominant factors are unclear. Therefore, this paper analyses the changes in aerosol-radiative-surface ozone in China's arid and semi-arid regions with the help of the Atmospheric Radiative Transfer (SBDART) model. The results suggest that Aerosol Optical Depth (AOD) and coarse Particulate Matter (PM10) have the same trend, with high values in spring and winter and low values in summer and autumn. Surface ozone is high in spring and summer and low in autumn and winter. Surface ozone is higher in spring and summer and lower in autumn and winter. In winter, mainly secondary pollutants are dominated by high pollution levels. In the rest of the seasons, a mixture of dust, motor vehicle exhaust, and soot is dominated by low pollution levels. Surface ozone is positively correlated with fine particles and negatively correlated with coarse particles. Temperature is positively correlated with surface ozone in all seasons and negatively correlated with PM10 in summer, autumn, and winter. Precipitation negatively correlates with PM10 each season and surface ozone in winter and spring. Analysis of surface ozone and PM10 sources in the more polluted city of Hohhot based on the back-line trajectory model showed that airflow trajectories mainly transported surface ozone and PM10 pollution from northwestern Inner Mongolia and western Mongolia. During dusty solid weather, the decrease in radiation reaching the Earth's surface and the cooling effect of aerosols lead to lower temperatures, which slows down the rate of chemical reactions of precursors of surface ozone, resulting in lower ozone concentrations at the surface. This study can provide a theoretical reference for aerosol and surface ozone control in arid and semi-arid areas of China.

NO and H2S Contribute to Crop Resilience against Atmospheric Stressors.

Atmospheric stressors include a variety of pollutant gases such as CO2, nitrous oxide (NOx), and sulfurous compounds which could have a natural origin or be generated by uncontrolled human activity. Nevertheless, other atmospheric elements including high and low temperatures, ozone (O3), UV-B radiation, or acid rain among others can affect, at different levels, a large number of plant species, particularly those of agronomic interest. Paradoxically, both nitric oxide (NO) and hydrogen sulfide (H2S), until recently were considered toxic since they are part of the polluting gases; however, at present, these molecules are part of the mechanism of response to multiple stresses since they exert signaling functions which usually have an associated stimulation of the enzymatic and non-enzymatic antioxidant systems. At present, these gasotransmitters are considered essential components of the defense against a wide range of environmental stresses including atmospheric ones. This review aims to provide an updated vision of the endogenous metabolism of NO and H2S in plant cells and to deepen how the exogenous application of these compounds can contribute to crop resilience, particularly, against atmospheric stressors stimulating antioxidant systems.

Remediation of oil-drilling cuttings by ozonation in a bubble flow reactor

Oil-drilling cuttings (ODCs) are the major wastes generated during oil/gas exploration and extraction. In the present work, a new method based on ozonation is suggested for the remediation of ODCs at ambient conditions, without pre-drying. During the ozonation process, the pressure drop across the gas phase along with the pH, redox potential, and temperature of liquid phase are monitored with the aid of built-in sensors. Occasionally, solid and liquid samples are collected to measure the total organic carbon (TOC) of each phase as a function of time, while the concentration of the total petroleum hydrocarbons (TPH) is measured before and after the completion of treatment. The maximum TOC removal efficiency for the solid phase reached ∼60% and that of TPH ∼ 40% whereas the energy efficiency was ∼ 0.1 kWh/g-TOC. The main mechanisms of ODC remediation are the mass-transfer of organic species from the solid to aqueous phase, and the direct oxidation by dissolved ozone, whereas their synergistic action is reflected in fluctuations of TOC concentration in liquid phase. The TOC removal efficiency of the solid phase increases with the flow rate decreasing, the ozone concentration increasing, and the mass ratio of ODC to seawater (SW) increasing. Ozonation in the liquid phase after its separation from treated ODC proceeds very fast through the direct oxidation by ozone. The process energy efficiency is favoured for low ozone concentration, low gas flow rate, high ODC to SW mass ratio, oxygen as feed gas, and without the addition of sodium dodecyl sulphate (SDS) as surfactant.