Unsaturated alcohols are important components in complex mixtures of oxygenated volatile organic compounds,and...
XU ZhiFang~(1,2),LIU Ze~2,GE MaoFa~(2*) & WANG WeiGang~2 1 Key Laboratory of Engineering Geomechanics,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China
Gas chromatography equipped with an electron capture detector （GC-ECD） has been widely used for measuring atmospheric N2O,but nonlinear response and the influence of atmospheric CO2 have been recognized as defects for quantification.An original GCECD method using N 2 as carrier gas was improved by introducing a small flow rate of CO2 makeup gas into the ECD,which could well remedy the above defects.The N2O signal of the improved method was 4-fold higher than that of the original method and the relative standard deviation was reduced from 〉 1% to 0.31%.N2O concentrations with different CO2 concentrations （172.2×10-6-1722×10-6mol/mol） measured by the improved GC-ECD method were in line with the actual N2O concentrations.However,the N2O concentrations detected by the original method were largely biased with a variation range of-4.5%～7%.The N2O fluxes between an agricultural field and the atmosphere measured by the original method were greatly overestimated in comparison with those measured by the improved method.Good linear correlation （R2=0.9996） between the response of the improved ECD and N2O concentrations （93×10-9-1966×10-9mol/mol） indicated that atmospheric N2O could be accurately quantified via a single standard gas.Atmospheric N2O concentrations comparatively measured by the improved method and a high precision GC-ECD method were in good agreement.
The reaction of a typical unsaturated alcohol,3-methyl-3-buten-1-ol(MBO331),with Cl atoms,was investigated for the first time.The reaction was investigated using discharged flow-tube coupled with electron impact mass spectrometer.The experiments were performed over the temperature range of 248 K―298 K and at pressure of 1 torr in He as the bath gas.The obtained kinetic data were used to derive the Arrhenius expression:k1 =(3.47 ± 1.21) × 10-11 exp[(599 ± 69)/T] cm3 molecule-1 s-1.Finally,atmospheric lifetimes of the MBO331 with respect to OH radicals,NO3 radicals and Cl atoms have been calculated and the atmospheric implications are considered briefly.
Multiphase acid-catalyzed oxidation by hydrogen peroxide has been suggested to be a potential route to secondary organic aerosol formation from isoprene and its gas-phase oxidation products, but the lack of kinetics data significantly limited the evaluation of this process in the atmosphere. Here we report the first measurement of the uptake of isoprene, methacrylic acid and methyl methacrylate into aqueous solutions of sulfuric acid and hydrogen peroxide. Isoprene cannot readily partition into the solution because of its high volatility and low solubility, which hinders its further liquid-phase oxidation. Both methacrylic acid and methyl methacrylate can enter the solutions and be oxidized by hydrogen peroxide, and steady-state uptake was observed with the acidity of solution above 30 wt.% and 70 wt.%, respectively. The steady-state uptake coefficient of methacrylic acid is much larger than that of methyl methacrylate for a solution with same acidity. These observations can be explained by the different reactivity of these two compounds caused by the different electron-withdrawing conjugation between carboxyl and ester groups. The atmospheric lifetimes were estimated based on the calculated steady-state uptake coefficients. These results demonstrate that the multiphase acid-catalyzed oxidation of methacrylic acid plays a role in secondary organic aerosol formation, but for isoprene and methyl methacrylate, this process is not important in the troposphere.
The electronic structures of six mono-terpenoids and two of their oxygenated derivatives were studied by He I photoelectron spectroscopy(PES).The observed bands were interpreted on the basis of empirical arguments and theoretical calculations.The first vertical ionization potentials for β-pinene,α-terpinene,terpinolene,γ-terpinene,limonene,myrcene,citral,and terpinene-4-ol were determined to be 8.73,7.57,8.26,8.30,8.53,8.68,8.71,and 8.77 eV,respectively.Most of these values have not been determined by PES before.The correlations of the first vertical ionization potentials of these compounds to the natural logarithms of rate constants for their reactions with the radicals OH,NO3,and O3 were determined.The correlation coefficients for their reactions with OH,NO3,and O3 were 0.97,0.91,and 0.95,respectively.This method is a powerful technique for predicting the rate constants for the atmospheric oxidation reactions of terpenoids.
WANG XiaoPeng TONG ShengRui GE MaoFa WANG WeiGang WANG DianXun
Using an improved smog chamber system,the temperature dependence of OH radical reaction with EMS was investigated over the temperature range of 297-346 K at 1.01×105 Pa pressure of air. The Arrhenius expression of the reaction was obtained for the first time. The mechanism of the reaction was also investigated.
Nitrous oxide （N 2 O） emissions from a maize field in the North China Plain （Wangdu County,Hebei Province,China） were investigated using static chambers during two consecutive maize growing seasons in the 2008 and 2009.The N 2 O pulse emissions occurred with duration of about 10 days after basal and additional fertilizer applications in the both years.The average N 2 O fluxes from the CK （control plot,without crop,fertilization and irrigation）,NP （chemical N fertilizer）,SN （wheat straw returning plus chemical N fertilizer）,OM- 1/2N （chicken manure plus half chemical N fertilizer） and OMN （chicken manure plus chemical N fertilizer） plots in 2008 were 8.51,72.1,76.6,101,107 ng N/（m 2 ·sec）,respectively,and in 2009 were 33.7,30.0 and 35.0 ng N/（m 2 ·sec） from CK,NP and SN plots,respectively.The emission factors of the applied fertilizer as N 2 O-N （EFs） were 3.8% （2008） and 1.1% （2009） for the NP plot,3.2% （2008） and 1.2% （2009） for the SN plot,and 2.8% and 2.2% in 2008 for the OM-1/2N and OMN plots,respectively.Hydromorphic properties of the investigated soil （with gley） are in favor of denitrification.The large differences of the soil temperature and water-filled pore space （WFPS） between the two maize seasons were suspected to be responsible for the significant yearly variations.Compared with the treatments of NP and SN,chicken manure coupled with compound fertilizer application significantly reduced fertilizer loss rate as N 2 O-N.
