Kinetic Characteristic of Photooxidation of Cypermethrin by Organic Peroxy Radical

The kinetic characteristic of photolysis of cypermethrin (CPM) sensitized by acetophenone (AP) and the effect of probe substance 2,6-Di-tert-butyl-4-methylphenol and tetralin is studied in this report. It showed that the photolysis rate of CPM increases slightly with the increase of AP concentration; photolysis rate of CPM has no relationship with [CPM] itself; The more dipolar moment the solvent has, the more the interaction between radical and solvent has, and the slower the photolysis of CPM is. The addition of radical probe substance confirms that ROO·is more than RO·. The steady-state concentration of ROO·is about 10?8 mol·L?1.

Role of Hydrogen Migrations in Carbonyl Peroxy Radicals in the Atmosphere

Carbonyl peroxy radicals (RC(O)O2) are the ubiquitous radical intermediates in the atmospheric oxidation of volatile organic compounds. In this work, theoretical studies are carried out to explore the role of the unimolecular H-migration in the carbonyl peroxy radicals by using quantum chemistry and kinetics calculations. The results showed that H-migration could be significant in the atmosphere at least in CH3CH2CH2C(O)O2 and (CH3)2CHCH2C(O)O2 with rates of ∽0.012 and -0.58^-1 at 298 K. Subsequent reactions of CH3CHCH2C(O)OOH would lead to the products with multi-functional groups, which might affect the aerosol formation process;while (CH3)2CCH2C(O)OOH would transform to formaldehyde and acetone in a few steps. These processes would be important for the atmospheric modelling of volatile organic compounds under low-NOx conditions.

Theoretical investigation on reaction mechanism and kinetics of m-xylene bicyclic peroxy radical with HO_(2)

M-xylene bicyclic peroxy radical(M-BPR)is an important atmospheric intermediate formed by the oxidation of m-xylene,which plays an important role in the new particle formation and growth of secondary organic aerosol.In this work,the reaction mechanism,thermodynamic analysis,and kinetics of the reaction between M-BPR and HO_(2)were investigated at the CCSD(T)/cc-pVDZ//B3LYP/6-311G(d,p)level of theory coupled with transition state theory.The calculated results indicate that the title reaction can occur on both singlet and triplet potential energy surfaces,and the formation of hydroperoxides and 3O_(2)via triplet state is the main reaction channel,while the other four singlet product channels are negligible due to the higher barrier heights.Additionally,the reaction rate constants are estimated by using the transition state theory over the temperature range of 258 K to 378 K,and reaction rate constants arc found to be negatively correlated with temperature.At 298 K,the total rate constant for the title reaction is 1.86×10^(-11)cm^(3)·molecule^(-1)·s^(-1).The calculated rate constants over the studied temperature range were used to fit the data and the three-parameter Arrhenius ex-studied is obtainted to be k(T)=4.22×10^(-15)·(T/300)^(1.44)·exp(2505/T)⁠.

Water effect on peroxy radical measurement by chemical amplification: Experimental determination and chemical mechanism

The water effect on peroxy radical measurement by chemical amplification was determined experimentally for HO2 and HO2+OH, respectively at room temperature (298±2) K and atmospheric pressure (1×105 Pa). No significant difference in water effect was observed with the type of radicals. A theoretical study of the reaction of HO2·H2O adduct with NO was performed using density functional theory at CCSD(T)/6-311 G(2d, 2p)//B3LYP/6-311 G(2d, 2p) level of theory. It was found that the primary reaction channel for the reaction is HO2·H2O+NO→HNO3+H2O (R4a). On the basis of the theoretical study, the rate constant for (R4a) was calculated using Polyrate Version 8.02 program. The fitted Arrenhnius equation for (R4a) is k = 5.49×107 T 1.03exp(?14798/T) between 200 and 2000 K. A chemical model incorporated with (R4a) was used to simulate the water effect. The water effect curve obtained by the model is in accordance with that of the experiment, suggesting that the water effect is probably caused mainly by (R4a).

Development and deployment of an instrument for measurement of atmospheric peroxy radical by chemical amplification

An instrument for measurement of peroxy radical by chemical amplification (PERCA) has been devel- oped at Peking University (PKU) and deployed in several field campaigns. PKU PERCA measures per- oxy radical via amplification of NO2 by peroxy radical in the presence of NO and CO through a chain reaction. The amount of amplified NO2 is detected by a NO2-luminal chemiluminescence detector. The chain length (CL) of 75±20 (1σ ) was determined routinely during field campaigns using a HO2 source from photolysis of water vapor at 185 nm in air. The detection limit for peroxy radical measurement was (1-5)×10?12 (volume ratio) with integration time of 1 min, mainly relying on the variation of the ambient O3 and NO2. The systematic uncertainty in the measurement of peroxy radical was estimated to be ±60%. The effect of water vapor on PKU PERCA was observed and determined in the laboratory. The meas- urements of peroxy radical during the Program of Regional Integrated Experiments of Air Quality over Pearl River Delta 2006 (PRIDE-PRD2006) campaign are presented to show the performance of the PERCA instrument and the behavior of the observed peroxy radical is discussed briefly.

Nighttime peroxy radicals chemistry at Rishiri Island during the campaign RISFEX 2003

Peroxy radicals （ROx） concentrations were measured by Peroxy Radical Chemical Amplifier （PERCA） technique during the field campaign RISFEX 2003 （RiShifi Fall Experiment 2003）, which was performed in September 2003 at Rishiri island （45.07 N, 141.12 E, and 35 m asl） in the sea of Japan. The concentrations of nighttime ROx radicals had temporal variations around an average of 7.9±5.8 （1σ） pptv and showed a positive correlation with the summed mixing ratio of four monoterpene species. Model calculations suggested that local nighttime ROx radicals were dominated by the reactions of monoterpene with ozone （03） and nitrate radical （NO3）, contributing ca. 76% and 19%, respectively. The comparisons between the observed ROx and ones modeled had implied that the current model may be overestimated the yields of peroxy radicals from the reactions of monoterpenes with ozone and an important source of peroxy radicals was possibly missed. Abnormal high concentrations of observed ROx radicals were found during high relative humidity （RH） period （especially 〉 95%）, and the possible explanation was that the humidity correction of ROx radicals under high RH conditions may be inaccurate and overestimates ROx concen-

Field measurement of the organic peroxy radicals by the low-pressure reactor plus laser-induced fluorescence spectroscopy

A low-pressure reactor(LPR) was developed for the measurement of ambient organic peroxy(RO2)radicals with the use of the laser-induced fluorescence(LIF) instrument.The reactor converts all the RO_(x)(=RO2+HO2+RO+OH) radicals into HO2 radicals.It can conduct different measurement modes through altering the reagent gases,achieving the speciated measurement of RO2 and RO2^#(RO2 radicals derived from the long-chain alkane,alkene and aromatic hydrocarbon).An example of field measurement results was given,with a maximum concentration of 1.88 × 10^(8) molecule/cm^(3) for RO2 and 1.18×10^(8) molecule/cm^(3) for RO2^(#).Also,this instrument quantifies the local ozone production rates directly,which can help to deduce the regional ozone control strategy from an experimental perspective.The new device can se rve as a potent tool for both the explo ration of frontier chemistry and the diagnosis of the control strategies.

From Where Did the Water Come That Filled the Earth’s Oceans? A Widely Overlooked Redox Reaction

Though two-thirds of Earth’s surface is covered by oceans, measurements of hydroxyl concentrations in upper mantle minerals, specifically in olivine, reportedly provide surprisingly low values. This has been interpreted to mean that there is little dissolved H2O in the Earth’s mantle. By inference, when Earth formed, there might not have been able enough water to fill the oceans through volcanic degassing. It has therefore been proposed that the missing water was delivered to Earth from space, through comets and other impacting bodies. However, the reported low hydroxyl concentrations in olivine and similar mineralsis probably based on a profound misunderstanding of a solid state reaction that converts hydroxyls into something more difficult to detect. There is indeed a redox reaction that converts, during cooling, solute hydroxyls in the matrix of minerals into peroxy plus H2. This widely overlooked redox conversion takes place under thermodynamic non-equilibrium conditions. Its significance is that any mineral and any rock available for collection at the Earth surface has gone through a process that causes hydroxyls, the telltale sign of dissolved H2O, to change into peroxyplusH2. The H2 molecules are diffusively mobile and may leave even structurally dense mineral grains. The remaining peroxy thus become the memory of the “true” solute H2O content, besides a few residual hydroxyls. Though first described over 30 years ago, this redox conversion has been largely ignored. As a result it is unknown how much H2O is contained in the Earth’s upper mantle but it is certainly much more than has been assumed until now on the basis of analysis of residual hydroxyls.

Photochemical Method to Evaluate Oxidation Levels in Heat-Treated Vegetable Oil： Comparison with Peroxide-Value and Acid-Value

To determine the degree of oxidation in vegetable oil, a photochemical method using the electron spin resonance （ESR） spin trapping technique was developed, and the results were compared with those obtained using conventional peroxide-value （PV） and acid-value （AV） methods. Vegetable oil heat-treated were subjected to short UV illumination, and the produced alkyl-oxyl radicals were identified and quantified using the ESR spin trapping technique. ESR signal intensity was used as an indicator of oil oxidation, which monotonically increased as a function of the heat-treatment time. Commercially, available oils were selected and analyzed. The results were compared with those obtained using the PV and AV methods. The present method displayed some analogies with the PV method at least in the early stage of heating. Overall, the present method had highly sensitive and capable of detecting early-stage oxidation in vegetable oil.

Lactobacillus plantarum B7 inhibits Helicobacter pylori growth and attenuates gastric inflammation

AIM:To determine the anti-Helicobacter property of Lactobacillus plantarum B7(L.plantarum)B7 supernatants in vitro and the protective effects of L.plantarum B7 on serum tumor necrosis factor-alpha(TNF-?),gastric malondialdehyde(MDA)level,apoptosis,and histopathology in Helicobacter pylori(H.pylori)-induced gastric inflammation in rats. METHODS:In vitro,the inhibition of H.pylori growth was examined using L.plantarum B7 supernatants at pH 4 and pH 7 and at the concentration of 1×,5×and 10×on plates inoculated with H.pylori.The inhibitory effect of H.pylori was interpreted by the size of the inhibition zone.In vitro,male Sprague-Dawley rats were randomly divided into four groups including group 1(control group),group 2(H.pylori infected group), group 3(H.pylori infected with L.plantarum B7 106 CFUs/mL treated group)and group 4(H.pylori infected with L.plantarum B7 1010 CFUs/mL treated group).One week after H.pylori inoculation,L.plantarum B7 106 CFUs/mL or 10 10 CFUs/mL were fed once daily to group 3 and group 4,respectively,for one week.Blood and gastric samples were collected at the end of the study. RESULTS:In vitro,at intact pH 4,mean inhibitory zone diameters of 8.5 mm and 13 mm were noted at concentrations of 5×and 10×of L.plantarum B7 supernatant disks,respectively.At adjusted pH 7, L.plantarum B7 supernatants at concentrations of 5 ×and 10×yielded mean inhibitory zone diameters of 6.5 mm and 11 mm,respectively.In the in vitro study, in group 2,stomach histopathology revealed mild to moderate H.pylori colonization and inflammation.The level of gastric MDA and epithelial cell apoptosis were significantly increased compared with group 1.The serum TNF-??level was significant decreased in group 3 compared with group 2(P<0.05).In addition,L.plantarum B7 treatments resulted in a significant improvement in stomach pathology,and decreased gastric MDA level and apoptotic epithelial cells. CONCLUSION:L.plantarum B7 supernatant inhibits H.pylori growth.This inhibition was dose-dependent and greater at pH 4.Moreover,L.plantarum B7 attenuated H.pylori-induced gastric inflammation.

Oxidation Mechanism and Toxicity Evolution of Linalool,a Typical Indoor Volatile Chemical Product

Linalool,a high-reactivity volatile chemical product(VCP)commonly found in cleaning products and disinfectants,is increasingly recognized as an emerging contaminant,especially in indoor air.Understanding the gas-phase oxidation mechanism of linalool is crucial for assessing its impact on atmospheric chemistry and human health.Using quantum chemical calculations and computational toxicology simulations,we investigated the atmospheric transformation and toxicity evolution of linalool under low and high NO/HO_(2)·levels,representing indoor and outdoor environments.Our findings reveal that linalool can undergo the novel mechanisms involving concerted peroxy(RO_(2)·)and alkoxy radical(RO·)modulated autoxidation,particularly emphasizing the importance of cyclization reactions indoors.This expands the widely known RO_(2)·-dominated H-shift-driven autoxidation and proposes a generalized autoxidation mechanism that leads to the formation of low-volatility secondary organic aerosol(SOA)precursors.Toxicological analysis shows that over half of transformation products(TPs)exhibited higher carcinogenicity and respiratory toxicity compared to linalool.We also propose time-dependent toxic effects of TPs to assess their long-term toxicity.Our results indicate that the strong indoor emission coupled with slow consumption rates lead to significant health risks under an indoor environment.The results highlight complex indoor air chemistry and health concerns regarding persistent toxic products during indoor cleaning,which involves the use of linalool or other VCPs.

The production of formaldehyde and hydroxyacetone in methacrolein photooxidation: New insights into mechanism and effects of water vapor

Methacrolein（MACR） is an abundant multifunctional carbonyl compound with high reactivity in the atmosphere. In this study, we investigated the hydroxyl radical initiated oxidation of MACR at various NO/MACR ratios（0 to 4.04） and relative humidities（＆lt; 3% to80%） using a flow tube. Meanwhile, a box model based on the Master Chemical Mechanism was performed to test our current understanding of the mechanism. In contrast to the reasonable predictions for hydroxyacetone production, the modeled yields of formaldehyde（HCHO） were twice higher than the experimental results. The discrepancy was ascribed to the existence of unconsidered non-HCHO forming channels in the chemistry of CH3-UC（=CH2）OO, which account for approx. 50%. In addition, the production of hydroxyacetone and HCHO were affected by water vapor as well as the initial NO/MACR ratio. The yields of HCHO were higher under humid conditions than that under dry condition. The yields of hydroxyacetone were higher under humid conditions at low-NOx level, while lower at high-NOxlevel. The reasonable explanation for the lower hydroxyacetone yield under humid conditions at high-NOx level is that water vapor promotes the production of Umethacrolein nitrate in the reaction of HOCH2 C（CH3）（OO）CHO with NO due to the peroxy radical-water complex formation, which was evidenced by calculational results. And the minimum equilibrium constant of this water complex formation was estimated to be 1.89 × 10 （-18） cm3/molecule. These results provide new insights into the MACR oxidation mechanism and the effects of water vapor.

Lipase catalyzed synthesis of epoxy-fatty acids

Lipase catalyzed synthesis of epoxy-fatty acids from unsaturated carboxylic acids was investigated. Under mild condition unsaturated carboxylic acids were converted to peroxycarboxylic acids by lipase with hydrogen peroxide, then the unsaturated peroxycarboxylic acids epoxidised the C = C bond of themselves.