Measurement of CO,HCN,and NO productions in atmospheric reaction induced by femtosecond laser filament

It is proved that the chemical reaction induced by femtosecond laser filament in the atmosphere produces CO,HCN,and NO,and the production CO and HCN are observed for the first time.The concentrations of the products are measured by mid-infrared tunable laser absorption spectroscopy.In the reduced pressure air,the decomposition of CO_(2) is enhanced by vibration excitation induced by laser filament,resulting in the enhanced production of CO and HCN.At the same time,the CO and HCN generated from the atmosphere suffer rotation excitation induced by laser filament,enhancing their absorption spectra.It is found that NO,CO,and HCN accumulate to 134 ppm,80 ppm,and 1.6 ppm in sealed air after sufficient reaction time.The atmospheric chemical reaction induced by laser filament opens the way to changing the air composition while maintaining environmental benefits.

Review of heterogeneous photochemical reactions of NOy on aerosol-A possible daytime source of nitrous acid (HONO) in the atmosphere

As an important precursor of hydroxyl radical, nitrous acid （HONO） plays a key role in the chemistry of the lower atmosphere. Recent atmospheric measurements and model calculations show strong enhancement for HONO formation during daytime, while they are inconsistent with the known sources in the atmosphere, suggesting that current models are lacking important sources for HONO. In this article, heterogeneous photochemical reactions of nitric acid/nitrate anion and nitrogen oxide on various aerosols were reviewed and their potential contribution to HONO formation was also discussed. It is demonstrated that HONO can be formed by photochemical reaction on surfaces with deposited HNO3 , by photocatalytic reaction of NO2 on TiO2 or TiO2 -containing materials, and by photochemical reaction of NO2 on soot, humic acids or other photosensitized organic surfaces. Although significant uncertainties still exist in the exact mechanisms and the yield of HONO, these additional sources might explain daytime observations in the atmosphere.

Mechanism and kinetics study on the ozonolysis reaction of 2,3,7,8-TCDD in the atmosphere

The ozonolysis of 2,3,7,8-tetra-chlorodibenzo-p-dioxin （2,3,7,8-TCDD） is an efficient degradation way in the atmosphere. The ozonolysis process and possible reactions path of Criegee Intermediates with NO and H2O are introduced in detail at the method of MPWB1K/6-31＋G（d,p）//MPWB1K/6- 311＋G（3df,2p） level. In ozonolysis, H2O is an important source of OH radical formation and initiated the subsequent degradation reaction. The Rice-Ramsperger-Kassel-Marcus （RRKM） theory was applied to calculate rate constants with the temperature ranging from 200 to 600 K. The rate constant of reaction between 2,3,7,8-TCDD and 03 is 4.80 × 10^-20 cm3/（mole.sec） at 298 K and 760 Tort. The atmospheric lifetime of the reaction species was estimated according to rate constants, which is helpful for the atmospheric model study on the degradation and risk assessment of dioxin.

Preparation of high water-retaining biochar and its mechanism of alleviating drought stress in the soil and plant system

To explore the effect of biochar on alleviating plant drought stress after being applied to soil,we prepared biochar using rice straw as raw material according to different pyrolysis temperatures(400,600 and 800°C)and reaction atmosphere(CO_(2)and N_(2)).The effect of different pyrolysis conditions on the water retention performance of biochar was studied.The early high water-retaining biochar materials were selected and wheat seeds were selected for the verification experiment of returning to the field in pots.Biochar with high porosity(specific surface area and total pore volume)and more surface hydrophilic functional groups(mainly-OH and-COOH)can indeed improve soil water retention performance.It is mainly reflected in the increase in the dry weight and fresh weight of wheat and the soil moisture content in the treatment group with the addition of biochar water retention agent.Among them,the growth rates of fresh weight and dry weight of wheat in the C800 treatment group were 11.51%and 10.64%,and the soil moisture content increased by 1.89%.It is worth noting that the application of biochar cannot completely alleviate the impact of drought stress on plants,but it can reduce the amount of water irrigation to a certain extent.Considering the quality of biochar,the biochar material(C800)prepared under the pyrolysis temperature of 800°C and the reaction atmosphere of CO_(2)has high water retention performance.

Release Behavior of Sulfur during Fluidized Bed Gasification

During fluidized bed gasification,sulfur in coal will be released,which will lead to environmental pollution.The release behavior of sulfur in fluidized bed gasification has not been fully studied,although fluidized bed gasification technology has a promising prospect.Thus the release behaviors of sulfur during fluidized bed gasification were investigated comprehensively through two aspects:temperature and reaction atmosphere.During air gasification,the main gaseous sulfur is H_(2)S,followed by COS,and the yield of SO_(2)and CS_(2)is low.With the increase of temperature,both of the released sulfur and the percentage of inorganic sulfur in gas phase increase.Under the same working condition,the distributions of sulfur forms in gasification residues are analogous.Organic sulfur is the dominate sulfur forms in the gasification residues.Sulfate in residues increases while organic sulfur decreases with increasing temperature.Among three reaction atmospheres(CO_(2)/steam/air)studied,the yield of H_(2)S is the most among the above four kinds of gaseous sulfur.The percentage of H_(2)S in gaseous sulfur(H_(2)S/Sg)is the highest in the process of steam gasification,while most sulfur is released during air gasification.The sequencing of H_(2)/CO is the same as that of H_(2)S/Sg,while the trend of sulfur release rate is consistent with that of carbon conversion rate.The distributions of sulfur species in the fly ash of CO_(2)gasification and steam gasification are similar,while the sulfate content in the fly ash of air gasification is the highest.

Mechanism and kinetic properties of NO_3-initiated atmospheric degradation of DDT

In this article, the NO3 radical-initiated atmospheric oxidation degradation of DDT was theoretically investigated using molecular orbital theory calculations. All the calculations of intermediates, transition states and products were performed at the MPWB1K/6-311＋G（3df,2p）//MPWB1K/6- 31＋G（d,p） level of theory. Several energetically favorable reaction pathways were revealed. The formation mechanisms of secondary pollutants were presented and discussed. The rate constants were deduced over the temperature range of 273-333 K using canonical variational transition-state （CVT） theory with the small curvature tunneling （SCT） method. Our study shows that H abstraction from the alkyl group and NO3 addition to the Ca atom of the benzene ring are the dominant reaction pathways. The rate-temperature formula of the overall rate constants is k（T）（DDT＋NO3） = （7.21 ~ 10-15）exp（-153.81/T） cm3/（mol.sec） over the possible atmospheric temperature range of 273-333 K. The atmospheric lifetime of DDT determined by NO3 radical is about 52.5 days, which indicates that it can be degraded in the gas phase within several months.