Assessing greenhouse gas emissions in Cuban agricultural soils: Implications for climate change and rice (Oryza sativa L.) production.

Assessing the impact of greenhouse gas (GHG) emissions on agricultural soils is crucial for ensuring food production sustainability in the global effort to combat climate change. The present study delves to comprehensively assess GHG emissions in Cuba's agricultural soil and analyze its implications for rice production and climate change because of its rich agriculture cultivation tradition and diverse agro-ecological zones from the period of 1990-2022. In this research, based on Autoregressive Distributed Lag (ARDL) approach the empirical findings depicts that in short run, a positive and significant impact of 1.60 percent % in Cuba's rice production. The higher amount of atmospheric carbon dioxide (CO2) levels improves photosynthesis, and stimulates the growth of rice plants, resulting in greater grain yields. On the other hand, rice production index raising GHG emissions from agriculture by 0.35 % in the short run. Furthermore, a significant and positive impact on rice production is found in relation to the farm machinery i.e., 3.1 %. Conversely, an adverse and significant impact of land quality was observed on rice production i.e., -5.5 %. The reliability of models was confirmed by CUSUM and CUSUM square plot. Diagnostic tests ensure the absence of serial correlation and heteroscedasticity in the models. Additionally, the forecasting results are obtained from the three machine learning models i.e. feed forward neural network (FFNN), support vector machines (SVM) and adaptive boosting technique (Adaboost). Through the % MAPE criterion, it is evident that FFNN has achieved high precision (91 %). Based on the empirical findings, the study proposed the adoption of sustainable agricultural practices and incentives should be given to the farmers so that future generations inherit a world that is sustainable, and healthy.

Comparative study on the removal of 1- naphthol and 2-naphthol by ferrate (VI): Kinetics, reaction mechanisms and theoretical calculations.

In this study, the oxidation of 1-naphthol (1-NAP) and 2-naphthol (2-NAP) by Fe(VI) was investigated. The impacts of operating factors were investigated through a series of kinetic experiments, including Fe(VI) dosages, pH and coexisting ions (Ca2+, Mg2+, Cu2+, Fe3+, Cl-, SO42-, NO3- and CO32-). Almost 100% elimination of both 1-NAP and 2-NAP could be achieved within 300 s at pH 9.0 and 25 °C. Cu2+ could significantly improve the degradation efficiency of 1-NAP and 2-NAP, but the impacts of other ions were negligible. The liquid chromatography-mass spectrometry was used to identify the transformation products of 1-NAP and 2-NAP in Fe(VI) system, and the degradation pathways were proposed accordingly. Electron transfer mediated polymerization reaction was the dominant transformation pathway in the elimination of NAP by Fe(VI) oxidation. After 300 s of oxidation, heptamers and hexamers were found as the final coupling products during the removal of 1-NAP and 2-NAP, respectively. Theoretical calculations demonstrated that the hydrogen abstraction and electron transfer reaction would easily occur at the hydroxyl groups of 1-NAP and 2-NAP, producing NAP phenoxy radicals for subsequent coupling reaction. Moreover, since the electron transfer reactions between Fe(VI) and NAP molecules were barrierless and could occur spontaneously, the theoretical calculation results also confirmed the priority of coupling reaction in Fe(VI) system. This work indicated that the Fe(VI) oxidation was an effective way for removing naphthol, which may help us understand the reaction mechanism between phenolic compounds with Fe(VI).

Environmental sustainable: Biogenic copper oxide nanoparticles as nano-pesticides for investigating bioactivities against phytopathogens.

Endocrine-disrupting chemicals (EDCs) are of interest in human physiopathology and have been extensively studied for their effects on the endocrine system. Research also focuses on the environmental impact of EDCs, including pesticides and engineered nanoparticles, and their toxicity to organisms. Green nanofabrication has surfaced as an environmentally conscious and sustainable approach to manufacture antimicrobial agents that can effectively manage phytopathogens. In this study, we examined the current understanding of the pathogenic activities of Azadirachta indica aqueous formulated green synthesized copper oxide nanoparticles (CuONPs) against phytopathogens. The CuONPs were analyzed and studied using a range of analytical and microscopic techniques, such as UV-visible spectrophotometer, Transmission electron microscope (TEM), Scanning electron microscope (SEM), X-ray diffraction (XRD) and Fourier transformed infrared spectroscopy (FTIR). The XRD spectral results revealed that the particles had a high crystal size, with an average size ranging from 40 to 100 nm. TEM and SEM images were utilized to verify the size and shape of the CuONPs, revealing that they varied between 20 and 80 nm. The existence of potential functional molecules involved in the reduction of the nanoparticles was confirmed by FTIR spectra and UV analysis. Biogenically synthesized CuONPs revealed significantly enhanced antimicrobial activities at 100 mg/L concentration in vitro by the biological method. The synthesized CuONPs at 500 µg/ml had a strong antioxidant activity which was examined through the free radicle scavenging method. Overall results of the green synthesized CuONPs have demonstrated significant synergetic effects in biological activities which can play a crucial impact in plant pathology against numerous phytopathogens.

Lockdown Amid COVID-19 Ascendancy over Ambient Particulate Matter Pollution Anomaly.

Air is a diverse mixture of gaseous and suspended solid particles. Several new substances are being added to the air daily, polluting it and causing human health effects. Particulate matter (PM) is the primary health concern among these air toxins. The World Health Organization (WHO) addressed the fact that particulate pollution affects human health more severely than other air pollutants. The spread of air pollution and viruses, two of our millennium's most serious concerns, have been linked closely. Coronavirus disease 2019 (COVID-19) can spread through the air, and PM could act as a host to spread the virus beyond those in close contact. Studies on COVID-19 cover diverse environmental segments and become complicated with time. As PM pollution is related to everyday life, an essential awareness regarding PM-impacted COVID-19 among the masses is required, which can help researchers understand the various features of ambient particulate pollution, particularly in the era of COVID-19. Given this, the present work provides an overview of the recent developments in COVID-19 research linked to ambient particulate studies. This review summarizes the effect of the lockdown on the characteristics of ambient particulate matter pollution, the transmission mechanism of COVID-19, and the combined health repercussions of PM pollution. In addition to a comprehensive evaluation of the implementation of the lockdown, its rationales-based on topographic and socioeconomic dynamics-are also discussed in detail. The current review is expected to encourage and motivate academics to concentrate on improving air quality management and COVID-19 control.

Enhanced periphyton biodegradation of endocrine disrupting hormones and microplastic: Intrinsic reaction mechanism, influential humic acid and microbial community structure elucidation.

Endocrine-disrupting compounds (EDCs), as well as microplastics, have drawn global attention due to their presence in the aquatic ecosystem and persistence in wastewater treatment plants (WWTPs). In the present study, for simultaneous bio-removal of two EDCs, 17α-ethinylestradiol (EE2), bisphenol A (BPA), and a microplastic, polypropylene (PP) four kinds of periphytic biofilms were employed. Additionally, the effect of humic acid (HA) on the removal efficacy of these biofilms was evaluated. It was observed that EE2 and BPA (0.2 mg L-1 each) were completely (∼100%) removed within 36 days of treatment; and the biodegradation of EE2, BPA, and PP was significantly enhanced in the presence of HA. Biodegradation of EE2 and BPA was evaluated through Ultra-high performance liquid chromatography (UHPLC), and Gas chromatography coupled with tandem mass spectrometry (GC-MS/MS) was used to determine the mechanism of degradation. Gel permeation chromatography (GPC) and SEM had validated the biodegradation of PP (5.2-14.7%). MiSeqsequencing showed that the community structure of natural biofilm changed after the addition of HA, as well as after the addition of EDCs and PP. This change in community structure might be a key factor regarding variable biodegradation percentages. The present study revealed the potential of periphytic biofilms for the simultaneous removal of pollutants of different chemical natures, thus provides a promising new method for wastewater treatment applications.

Do soil conservation practices exceed their relevance as a countermeasure to greenhouse gases emissions and increase crop productivity in agriculture?

Globally, agriculture sector is the significant source of greenhouse gases (GHGs) emissions into the atmosphere. To achieve the goal of limiting or mitigating these emissions, a rigorous abatement strategy with an additional focus on improving crop productivity is now imperative. Replacing traditional agriculture with soil conservation-based farming can have numerous ecological benefits. However, most assessments only consider improvements in soil properties and crop productivity, and often preclude the quantitative impact analysis on GHGs emissions. Here, we conducted a meta-analysis to evaluate crop productivity (i.e., biomass, grain, total yield) and GHGs emissions (i.e., CO2, N2O, CH4) for three major soil conservation practices i.e., no-tillage, manures, and biochar. We also examined the yield potential of three major cereal crops (i.e., wheat, rice, maize) and their significance in mitigating GHGs emissions. None of the manures were able to reduce GHGs emissions, with poultry manure being the largest contributor to all GHGs emissions. However, pig-manure had the greatest impact on crop yield while emitting the least CO2 emissions. Use of biochar showed a strong coupling effect between reduction of GHGs (i.e., CH4 by -37%; N2O by -25%; CO2 by -5%) and the increase in crop productivity. In contrast, no-tillage resulted in higher GHGs emissions with only a marginal increase in grain yield. Depending on crop type, all cereal crops showed varied degrees of GHGs mitigation under biochar application, with wheat responding most strongly due to the additional yield increment. The addition of biochar significantly reduced CO2 and N2O emissions under both rainfed and irrigated conditions, although CH4 reductions were identical in both agroecosystems. Interestingly, the use of biochar resulted in a greater yield benefit in rainfed than in irrigated agriculture. Despite significant GHGs emissions, manure application contributed to higher crop yields, regardless of soil type or agroecosystem. Moreover, no-tillage showed a significant reduction in CH4 and N2O emissions under rainfed and irrigated conditions. Notably , biochar application in coarse while no-till in fine textured soils contributed to N2O mitigation. Most importantly, effectiveness of no-tillage as a countermeasure to GHGs emissions while providing yield benefits is inconsistent. Overall, the decision to use farm manures should be reconsidered due to higher GHGs emissions. We conclude that the use of biochar could be an ideal way to reduce GHGs emissions. However, further understanding of the underlying mechanisms and processes affecting GHGs emissions is needed to better understand the feedback effects in conservation agriculture.

Analytical strategies to sense water stress level: An analysis of ground water fluctuations sensing SDGs under pandemic scenario.

Groundwater fluctuation is directly linked with the consumption and wastage of water sources during the pandemic interval. That is why water resource planners directly target water resource and sanitation systems in line with the sustainable development goals (SDGs) concept. In this study, District Multan is designated as a study area with 85 distinct station points data sets from four zones taken to pursue this massive investigation. The data sets are studied analytically and graphically to explore the relationships among critical variables like population, average water consumption, groundwater elevation, water table depth, total consumption, wastage of water during the pandemic days, etc. For in-depth analysis, the statistical approaches are employed on these massive data sets to reveal the trend among each dataset point to generate predictive models. The results revealed that groundwater reservoirs and levels are continuously declining on an annual basis in the meantime, the water consumption and extraction are increasing simultaneously. The consumption during pandemic days has been increased so much at the same time the wastage and total consumption of water is rising a lot in contrast to previous daily consumption and water demand. The coefficient of determination (R-square) values vary from 0.41 to 0.93 in this investigation. It will help the utilization of developed models and water-providing organizations to forecast groundwater instabilities for the future. Moreover, the situation in the study area is very alarming in terms of water stress conditions. This study will help the decision-making agencies to produce a policy following the SDGs concept to control water consumption and higher extraction.

Can Bacterial Endophytes Be Used as a Promising Bio-Inoculant for the Mitigation of Salinity Stress in Crop Plants?-A Global Meta-Analysis of the Last Decade (2011-2020).

Soil salinity is a major problem affecting crop production worldwide. Lately, there have been great research efforts in increasing the salt tolerance of plants through the inoculation of plant growth-promoting endophytic bacteria. However, their ability to promote plant growth under no-stress and salinity-stress conditions remains largely uncertain. Here, we carried out a global meta-analysis to quantify the plant growth-promoting effects (improvement of morphological attributes, photosynthetic capacity, antioxidative ability, and ion homeostasis) of endophytic bacteria in plants under no-stress and salinity-stress conditions. In addition, we elucidated the underlying mechanisms of growth promotion in salt-sensitive (SS) and salt-tolerant (ST) plants derived from the interaction with endophytic bacteria under no-stress and salinity-stress conditions. Specifically, this work encompassed 42 peer-reviewed articles, a total of 77 experiments, and 24 different bacterial genera. On average, endophytic bacterial inoculation increased morphological parameters. Moreover, the effect of endophytic bacteria on the total dry biomass, number of leaves, root length, shoot length, and germination rate was generally greater under salinity-stress conditions than no-stress conditions. On a physiological level, the relative better performance of the bacterial inoculants under the salinity-stress condition was associated with the increase in total chlorophyll and chlorophyll-b, as well as with the decrease of 1-aminocylopropane-1-carboxylate concentration. Moreover, under the salinity-stress condition, bacterial inoculation conferred a significantly higher increase in root K+ concentration and decrease in leaf Na+ concentration than under the no-stress condition. In SS plants, bacterial inoculation induced a higher increase in chlorophyll-b and superoxide dismutase activity, as well as a higher decrease in abscisic acid content, than in ST plants. Under salinity-stress, endophytic bacterial inoculation increased root K+ concentration in both SS and ST plants but decreased root Na+ concentration only in ST plants. Overall, this meta-analysis suggests that endophytic bacterial inoculation is beneficial under both no salinity-stress and salinity-stress conditions, but the magnitude of benefit is definitely higher under salinity-stress conditions and varies with the salt tolerance level of plants.

Sustainable ferrate oxidation: Reaction chemistry, mechanisms and removal of pollutants in wastewater.

This review is intended to evaluate the use of ferrate (Fe(VI)), being a green coagulant, sustainable and reactive oxidant, to remove micro pollutants especially pharmaceutical pollutants in contaminated water. After a brief description of advanced oxidation processes, fundamental dimensions regarding the nature, reactivity, and chemistry of this oxidant are summarized. The degradation of contaminants by Fe(VI) involves several mechanisms and reactive agents which are critically evaluated. The efficiency and chemistry of Fe(VI) oxidation differs according to the reaction conditions and activation agent, such as soluble Fe(VI) processes, which involve Fe(VI), UV light, and electro-Fe(VI) oxidation. Fe(VI) application methods (including single dose, multiple doses, chitosan coating etc), and Fe(VI) with activating agents (including sulfite, thiosulfate, and UV) are also described to degrade the micro pollutants. Besides, application of Fe(VI) to remove pharmaceuticals in wastewater are intensely studied. Electrochemical prepared Fe(VI) has more wide application than wet oxidation method. Meanwhile, we elaborated Fe(VI) performance, limitations, and proposed innovative aspects to improve its stability, such as the generation of Fe(III), synergetic effects, nanopores entrapment, and nanopores capsules. This study provides conclusive direction for synergetic oxidative technique to degrade the micro pollutants.

Differential effects of sulfamethoxazole concentrations on the enzymatic dynamics of aerobic composting.

Enzymatic activities play an important role in the biological composting processing of agricultural wastes. This paper explores the effect of sulfamethoxazole (SMX) (Control, 25 mg/kg, 50 mg/kg, and 100 mg/kg) on the enzymatic activities of cellulase, protease, urease, and arylsulfatase. Compost samples were taken at three different intervals for analysis (day 0, day 25, and day 45). The findings revealed that at the start of the composting process, a strongly negative effect on enzymatic behavior was observed, and this response was significantly dependent on SMX concentrations (p < 0.05). The inhibition was consistent across all treatments. According to the results, the negative impact of SMX on community structure can result in selection pressure. Furthermore, all of the treatments had drastically improved enzymatic activity by the end of the composting process (day 45). This effect was presumably caused by the deterioration of SMX and a substantial stress reduction.

Nitrous oxide emission from agricultural soils: Application of animal manure or biochar? A global meta-analysis.

Organic amendments (animal manure and biochar) to agricultural soils may enhance soil organic carbon (SOC) contents, improve soil fertility and crop productivity but also contribute to global warming through nitrous oxide (N2O) emission. However, the effects of organic amendments on N2O emissions from agricultural soils seem variable among numerous research studies and remains uncertain. Here, eighty-five publications (peer-reviewed) were selected to perform a meta-analysis study. The results of this meta-analysis study show that the application of animal manure enhanced N2O emissions by 17.7%, whereas, biochar amendment significantly mitigated N2O emissions by 19.7%. Moreover, coarse textured soils increased [lnRR‾ = 182.6%, 95% confidence interval (CI) = 151.4%, 217.7%] N2O emission after animal manure, in contrast, N2O emission mitigated by 7.0% from coarse textured soils after biochar amendment. In addition, this study found that 121-320 kg N ha-1 and ⩽ 30 T ha-1 application rates of animal manure and biochar mitigated N2O emissions by 72.3% and 22.5%, respectively. Soil pH also played a vital role in regulating the N2O emissions after organic amendments. Furthermore, > 10 soil C: N ratios increased N2O emissions by 121.4% and 27.6% after animal and biochar amendments, respectively. Overall, animal manure C: N ratios significantly enhanced N2O emissions, while, biochar C: N ratio had not shown any effect on N2O emissions. Overall, average N2O emission factors (EFs) for animal manure and biochar amendments were 0.46% and -0.08%, respectively. Thus, the results of this meta-analysis study provide scientific evidence about how organic amendments such as animal manure and biochar regulating the N2O emission from agricultural soils.

Nexus on climate change: agriculture and possible solution to cope future climate change stresses.

The changing climate scenarios harshen the biotic stresses including boosting up the population of insect/pest and disease, uplifting weed growth, declining soil beneficial microbes, threaten pollinator, and boosting up abiotic stresses including harsh drought/waterlogging, extremisms in temperature, salinity/alkalinity, abrupt rainfall pattern)) and ulitamtely  affect the plant in multiple ways. This nexus review paper will cover four significant points viz (1) the possible impacts of climate change; as the world already facing the problem of food security, in such crucial period, climatic change severely affects all four dimensions of food security (from production to consumption) and will lead to malnutrition/malnourishment faced by low-income peoples. (2) How some major crops (wheat, cotton, rice, maize, and sugarcane) are affected by stress and their consequent loss. (3) How to develop a strategic work to limit crucial factors, like their significant role in climate-smart breeding, developing resilience to stresses, and idiotypic breeding. Additionally, there is an essence of improving food security, as much of our food is wasted before consumption for instance post-harvest losses. (4) Role of biotechnology and genetic engineering in adaptive introgression of the gene or developing plant transgenic against pests. As millions of dollars are invested in innovation and research to cope with future climate change stresses on a plant, hence community base adaptation of innovation is also considered an important factor in crop improvements. Because of such crucial predictions about the future impacts of climate change on agriculture, we must adopt measures to evolve crop.

The influence of humic and fulvic acids on Cd bioavailability to wheat cultivars grown on sewage irrigated Cd-contaminated soils.

The soil cadmium (Cd) contamination is a ubiquitous environmental problem that has resulted from intense irrigation with wastewater. This pot trial was conducted with aim to produce safe food with Cd tolerant wheat cultivar in wastewater irrigated soils. For this purpose, two wheat cultivars NARC-2011 (Cd tolerant) and Shafaq-2006 (Cd sensitive) were screened out and selected, after conducting a pilot trial of twelve local wheat cultivars against Cd stress. Both cultivars were grown in naturally contaminated soils with Cd concentrations (4.18, 3.23, 2.29 and 1.25 mg kg-1). After harvesting, NARC-2011 showed significant photosynthetic attributes, grain biochemical parameters and yield. Additionally, Cd concentrations in edible grains of NARC-2011 cultivars were found within standard limits (200 mg kg-1), in all contaminated soils. Furthermore, a marked decrease in Cd bioavailability was noted with cultivar NARC-2011, where contribution of mobile Cd fractions (exchangeable and reducible) percentage was decreased, while immobile Cd fractions percentage increased (oxidizable and residual). Fourier transform infrared (FTIR) spectroscopy reflects the maturity and stability of humic and fulvic like acid fractions and revealed that humification of these compounds after prolonged sludge enriched wastewater irrigation lowered the Cd availability. The wheat cultivar NARC-2011 (Cd tolerant) could be opted to grow on soils irrigated with wastewater for a long time, as Cd bioavailability decreased with ageing due to stabilized humic substances and varietal tolerance.

Alumina-mediated photocatalytic degradation of hexachlorobenzene in aqueous system: Kinetics and mechanism.

Five kinds of Al2O3 were characterized by SEM, TEM, FT-IR and BET surface area, and then used as carriers to investigate the photochemical removal of hexachlorobenzene (HCB) in aqueous system. The results showed that HCB coated on the surfaces of all Al2O3 could be photodegraded rapidly, and Neutral-Al2O3 presented the best performance. Meanwhile, the efficient removal of HCB in real water matrices, including tap water, river water and secondary clarifier effluent showed the potential practical application of Al2O3. EPR and theoretical calculation revealed the generation of hydroxyl radicals on Al2O3 surface under 500 W Xe lamp irradiation. Nine intermediates and a small amount of Cl- were identified by GC/MS, LC/MS and IC analysis, which was further verified by transition state calculations. These results can provide a new technique for HCB removal in water and wastewaters, and give more insights into the environmental ecological risk assessment of this pollutant.

Synthesis of Ligand Functionalized ErbB-3 Targeted Novel DNA Nano-Threads Loaded with the Low Dose of Doxorubicin for Efficient In Vitro Evaluation of the Resistant Anti-Cancer Activity.

PURPOSE: Doxorubicin (Dox) being a hydrophobic drug needs a unique carrier for the effective encapsulation with uniformity in the aqueous dispersion, cell culture media and the biological-fluids that may efficiently target its release at the tumor site. METHODS: Circular DNA-nanotechnology was employed to synthesize DNA Nano-threads (DNA-NTs) by polymerization of triangular DNA-tiles. It involved circularizing a linear single-stranded scaffold strand to make sturdier and rigid triangles. DNA-NTs were characterized by the AFM and Native-PAGE tests. Dox binding and loading to the Neuregulin1 (NRG1) functionalized DNA based nano-threads (NF-DBNs) was estimated by the UV-shift analysis. The biocompatibility of the blank NRG-1/DNA-NTs and enhanced cytotoxicity of the NF-DBNs was assessed by the MTT assay. Cell proliferation/apoptosis was analyzed through the Flow-cytometry experiment. Cell-surface binding and the cell-internalization of the NF-DBNs was captured by the double-photon confocal microscopy (DPCM). RESULTS: The AFM images revealed uniform DNA-NTs with the diameter 30 to 80 nm and length 400 to 800 nm. PAGE native gel was used for the further confirmation of the successful assembly of the strands to synthesize DNA-NTs that gave one sharp band with the decreased electrophoretic mobility down the gel. MTT assay showed that blank DNA-NTs were biocompatible to the cells with less cytotoxicity even at elevated concentrations with most of the cells (94%) remaining alive compared to the dose-dependent enhanced cytotoxicity of NF-DBNs further evidenced by the Flow-cytometry analysis. CONCLUSION: Uniform and stiffer DNA-NTs for the potential applications in targeted drug delivery was achieved through circular DNA scaffolding.

A combined experimental and computational study on the oxidative degradation of bromophenols by Fe(VI) and the formation of self-coupling products.

In this study, the degradation of eight bromophenols (BPs), including monobromophenols (2-BP, 3-BP, and 4-BP), dibromophenols (2,4-DBP, 2,6-DBP, and 3,5-DBP), a tribromophenol (2,4,6-TBP) and a pentabromophenol (PBP), by a Fe(VI) reaction process at a pH of 8.0 was systematically studied. It was concluded that their degradation rates increased with increasing Fe(VI) concentrations in solution. The removal of 2,4,6-TBP, 2-BP, and 2,6-DBP was faster than that of the other five BPs, which could be attributed to the position of the substituting Br atom. Moreover, the direct oxidation and coupling reactions greatly influenced the reactivity of the bromophenols with Fe(VI). The electron paramagnetic resonance (EPR) analysis confirmed the presence of hydroxyl radicals in present system. The oxidation reaction products of PBP and 2-BP were recognized by an electrospray time-of-flight mass spectrometer; hydroxylation, hydroxyl substitution, the cleavage of the C-C bond, direct oxidation and polymerization via an end linking mechanism were noticeably found in the reaction process, resulting in the formation of polymerization products and causing hydroxylation to occur. Theoretical calculations further determined the possible oxidation sites of 2-BP and PBP. This study may provide comprehensive and important information on the remediation of BPs by Fe(VI).

Visible light and fulvic acid assisted generation of Mn(III) to oxidize bisphenol A: The effect of tetrabromobisphenol A.

Bisphenol A (BPA) and tetrabromobisphenol A (TBBPA), endocrine disrupting compounds (EDCs), are of increasing concerns for many years. This paper presents the elimination of BPA under visible light (VL) (λ ≥ 420 nm) irradiated solutions containing fulvic acid (FA) and MnSO4 (Mn(II)), and examines the possible effects of TBBPA on the transformation of BPA. After 72 h of reaction time, the removal efficiency of BPA in the studied system was 69%. Results of different experiments to identify oxidative species suggested the dominate role of soluble manganese (III) (Mn(III)) in the conversion of BPA. The transformation of BPA by the VL/FA/Mn(II) system was through self-oligomerization in absence of co-existence of TBBPA. In the co-existence of BPA with TBBPA, the removal of BPA was largely inhibited due to the competition with available Mn(III) and the possible occurrence of cross-coupling reactions between the two EDCs. This phenomenon was further elucidated by product analyses and density functional theory (DFT) calculations. The energy difference (ΔE) for generating a cross-coupling product was calculated as -23.4 kJ mol-1, much lower than the positive values of ΔE for self-coupling products of BPA or TBBPA, demonstrating that cross-coupling reactions between BPA and TBBPA likely occurred easier than the respective self-coupling reactions. The toxicity test showed that the overall estrogenic activity of BPA reaction solution was significantly decreased by the VL/FA/Mn(II) system. In general, our study provided new insights into the transformation of co-existing EDCs by in situ formed Mn(III) in aqueous solution.

Ozonation of pentabromophenol in aqueous basic medium: Kinetics, pathways, mechanism, dimerization and toxicity assessment.

Ozonation has been identified effective technique to degrade phenolic compounds, and production of intermediate dimers are major threat. In this study, we systematically investigated the degradation of Pentabromophenol (PBP) in an aqueous medium by using two different ozone generators (sources: air and water). We studied various factors that influenced the degradation kinetics of PBP, including the pH (7.0, 8.0, and 9.0), humic acid (HA) and anions (Cl-, SO42-, NO3-, and HCO3-). PBP was efficiently degraded within 5 min (O3 source: water) and 45 min (O3 source: air) at pH 8.0 maintained by phosphate buffer. Reaction kinetics revealed 17 b y-products with five possible pathways, including dimers with their isomers and lower bromophenols. Furthermore, the frontier molecular orbital theory was employed to confirm the proposed ozonation pathways, including the breakage of the CO bond at C5 and C4 positions, and the cleavage of the CC bond at C3 and C6 position. Product P5, P14 (hydroxyl-nonabromophenyl ether) and P15 (dihydroxyl-octabromophenyl ether) were identified with isomers. Ecological Structure Activity Relationships toxicity assessment resulted into the conversion of highly toxic PBP (acute toxicity: LC50 = 0.11 mg L-1 for fish, LC50 = 0.124 mg L-1 for daphnia, and EC50 = 0.118 mg L-1 for green algae) to less harmful products aside from dimers. P14 (acute toxicity: LC50 = 1.04 × 105) found to be more toxic as compare to PBP. From these findings, we concluded that ozonation is an effective and ideal process for PBP degradation.

Understanding the ozonated degradation of sulfadimethoxine, exploration of reaction site, and classification of degradation products.

Ozonation has been demonstrated to be an efficient method of water treatment. In this study, the degradation of 20 mg/L of sulfadimethoxine (SDM) in different water matrices during ozonation was investigated. At pH 7.0, 100% removal of SDM was achieved by ozonation within 10 min. The degradation of SDM was more pronounced at acidic pH than under ambient environmental conditions, and was also dependent on different water matrices. Both direct and indirect oxidation of SDM by ozone were observed, and it was also shown that both ozone molecules and hydroxyl radicals were involved in the SDM degradation process, whereas it was found that the saturated ring of SDM made it O3-recalcitrant. Seven transformation products (TPs) were identified during SDM ozonation, allowing three degradation pathways to be proposed. Additionally, the main reaction sites, including N (7) and C (2) on the aniline ring, and the __S__N__ bond, were confirmed both experimentally and theoretically. The toxicity evolution during the degradation process was investigated, and the results showed no toxic intermediate products obtained during ozonation.