Observations of the Nitrate Radical in the Marine Boundary Layer

A study of the nitrate radical (NO3) has been conducted through a series of campaigns held at the Weybourne Atmospheric Observatory, located on the coast of north Norfolk, England. The NO3 concentration was measured in the lower boundary layer by the technique of differential optical absorption spectroscopy (DOAS). Although the set of observations is limited, seasonal patterns are apparent. In winter, the NO3 concentration in semi-polluted continental air masses was found to be of the order of 10 ppt, with an average turnover lifetime of 2.4 minutes. During summer in clean northerly air flows, the concentration was about 6 ppt with a lifetime of 7.2 minutes. The major loss mechanisms for the radical were investigated in some detail by employing a chemical box model, constrained by a suite of ancillary measurements. The model indicates that during the semi-polluted conditions experienced in winter, the major loss of NO3 occurred indirectly through reactions of N2O5, either in the gas-phase with H2O, or through uptake on aerosols. The most important direct loss was via reactions of NO3 with a number of unsaturated nonmethane hydrocarbons. The cleaner air masses observed during the summer were of marine origin and contained elevated concentrations of dimethyl sulfide (DMS), which provided the major loss route for NO3. The box model was then used to investigate the conditions in the remote marine boundary layer under which DMS will be oxidised more rapidly at night (by NO3) than during the day (by OH). This should occur if the concentration of NO2 is more than about 60% that of DMS.     

海泡石中水的红外光谱及其结构稳定性的指示作用

在仔细分析海泡石中水的约外谱图特点的基础上,本文其结构水（ＯＨ）结晶水（ＯＨ２）沸石水（Ｈ２Ｏ）吸收带进行了逐个归属,并对比分析了热液型和沉积型海泡石谱图的差异,通过分析处理海泡石样品红外谱图,发现热处理过程中谱图的变化特征与热相变过程能很好地吻合,论证了海泡石中水的红外光谱具有指示结构稳定性的作用。     

钝顶螺旋藻藻胆蛋白的纯化及其清除氧自由基的作用

本文对钝顶螺旋藻藻胆蛋白的分离工艺进行了研究,建立经细胞破碎,硫酸铵沉淀蛋白,羟基磷灰石柱分离工尼凝胶电泳,吸收光谱,荧光光谱和量热分析等研究,证明Ｃ－ＰＣ由大小两个亚基组成,分子量分别为１７２００ｕ和１４９００ｕ;ＡＰＣ由一个亚基组成,分子量为１３４００ｕ。     

Radiocarbon tracer measurements of atmospheric hydroxyl radical concentrations

Radiochemical techiques have many untapped applications in atmospheric chemistry, especially when great sensitivity is required. We describe the application of these techniques to the measurement of hydroxyl radical concentrations in the troposphere.     

Estimation of hydroxyl radical concentrations in the marine atmospheric boundary layer using a reactive atmospheric tracer

Hydroxyl radical (OH) concentrations in the atmospheric boundary layer over a number of remote ocean locations are calculated from the measured diurnal variation in atmospheric dimethylsulfide (DMS). By using averaged DMS data sets from extended periods, the calculation yields OH concentrations averaged over periods from several days to weeks. These average OH concentrations range from 7×10⁵ to 2.9×10⁶ molecules cm^-3, corresponding to midday maxima of 3 to 12×10⁶ molecules cm^-3. The lowest values correspond to studies with the lowest light intensity (Antarctic summer and South Atlantic winter), and the highest values to regions with probable anthropogenic influence. In addition to the long term averages, daily average OH levels can be calculated for most days in a two week period from a cruise in the tropical eastern Pacific. These calculations are in good argeement with global average OH levels derived from other tracers, and are consistent with model OH calculations when allowance is made for variation in ambient ozone levels between the studies. Estimates of gas exchange made from the diurnal variation of DMS suggest that either the gas exchange coefficient of DMS or the boundary layer mixing depth may have been overestimated in past analyses.     

海洋固体颗粒主要无机组份表面羟基形态分布特征

本文根据海洋固体颗粒主要无机组份表面羟基的酸碱特性，描述了其表面羟基存在形态随ＰＨ变化特征，并研究了据零电荷点定义直接由表面羟基分布曲线测定颗粒零电荷点ＰＨｐｚｃ的新方法。     

Intercomparison of Two Hydroxyl Radical Measurement Techniques at the Atmosphere Simulation Chamber SAPHIR

At the atmosphere simulation chamber SAPHIR in Jülich both Laser-Induced Fluorescence Spectroscopy (LIF) and Long-Path Differential Optical Laser Absorption Spectroscopy (DOAS) are operational for the detection of OH radicals at tropospheric levels. The two different spectroscopic techniques were compared within the controlled environment of SAPHIR based on all simultaneous measurements acquired in 2003 (13 days). Hydroxyl radicals were scavenged by added CO during four of these days in order to experimentally check the calculated precisions at the detection limit. LIF measurements have a higher precision (σ= 0.88×10⁶ cm^–3) and better time resolution (Δt = 60 s), but the DOAS method (σ= 1.24×10⁶ cm^–3, Δt = 135 s) is regarded as primary standard for comparisons because of its good accuracy. A high correlation coefficient of r = 0.95 was found for the whole data set highlighting the advantage of using a simulation chamber. The data set consists of two groups. The first one includes 3 days, where the LIF measurements yield (1 – 2) ×10⁶ cm^–3 higher OH concentrations than observed by the DOAS instrument. The experimental conditions during these days are characterized by increased NO_x concentration and a small dynamic range in OH. Excellent agreement is found within the other group of 6 days. The regression to the combined data of this large group yields unity slope without a significant offset.     

A Study of the Reaction of OH Radicals with N-Methyl Pyrrolidinone,N-Methyl Succinimide and N-Formyl Pyrrolidinone

A study of the oxidation mechanism of N-methyl pyrrolidinone (C₅H₉NO, NMP) initiated by hydroxyl radicals was made at EUPHORE at atmospheric pressure (1000 ± 10) mbar of air and ambient temperature (T = 300 ± 5 K). The main products were N-methyl succinimide (NMS) (52 ± 4)% and N-formyl pyrrolidinone (FP) (23 ± 9)%. The relative rate technique was used to determine the rate constants of OH with NMP, NMS and FP, the measured values were (in units of cm³ molecule ^{− 1} s^{− 1}): k_NMP = (2.2 ± 0.4) × 10^{− 11}, k_NMS = (1.4 ± 0.3) × 10^{− 12} and k_FP = (6 ± 1) × 10^{− 12}. The results are presented and discussed in terms of the atmospheric impact.