Absorption, concentration and determination of trace amounts of air pollutants by flow injection method coupled with a chromatomembrane cell system: application to nitrogen dioxide determination

The concentration distribution of an analyte in a chromatomembrane cell (CMC) was examined by using various air samples of different air pollutant (NO₂) concentrations and volumes, and the results obtained could be explained by a proposed principle of the concentration distribution of the analyte in the CMC. This principle was for the first time proved experimentally in the present study. On-line preconcentration and continuous determination of the air pollutant (NO₂) in air samples were realized by coupling a three-hole CMC with a flow injection analysis (FIA) system, where a triethanolamine (TEA) aqueous solution (2 g l⁻¹) was used as an absorbing solution for NO₂ in the air samples. A calibration method with standard nitrite aqueous solutions was developed for the determination of NO₂ in the air samples. Concentrations of NO₂ in indoor air and its diluted air samples were determined by the proposed CMC/FIA method. The volume of air sample necessary for the measurement was decreased to only 5 ml. The measuring time for one sample was about 5–6 min even when a 20 ml air sample was used.     

Acoustic remote sensing of the atmosphere

I.IntroductionBy\"remotesensing*ismeantatechniquefordctectingand/ormeasuringthelocation,shapc,featuresandstatcsofanobjcctfarbcyondbyaspecifiedtool.Andby\"acousticremotescnsingoftheatmosphcre'isthusmeantthctechniquefordetcctingthcstatesoftheatmos-phercandvariousphenomenainitbysoundwavcsasatoo1farbeyond.Itisintcrcstingtonotethattheword\"sound'means\"acousticwaves'whenuscdasanoun,andhasthemeaningof\"toexamine\"or\"toprobe'whenusedasatransitiveverb.ThcreIYomonecanscethecloserc1ationshipbetwccn\"acoustic…     

Quantification of VOC emission rates from the biosphere

Determining which volatile organic compounds (VOCs) are synthesized by plants and emitted into the atmosphere and at what rates is a critical component of our understanding of the Earth system, as is understanding how these emissions respond to environmental controls and how they may change in the future. Here, we review the methods used to sample biogenic VOC emissions, from the leaf scale to the regional scale, and focus on the challenges that this task presents.     

大气环境中硫化氢的测定——亚甲基蓝比色法

通过条件实验，利用大气采样器，采集大气中的硫化氢样品，用碱性锌氨络盐吸收藏吸收后，在三氯化铁存在下，与对氨基二甲基苯胺生成亚甲基蓝，比色法定量测定。结果表明，双管连接比单管效果好，吸收液量以每管10mL、采样时间30～40min、采样流量0．5～0．8L／min为佳。     

常压程序升温热解-质谱系统在煤脱羧过程中的应用

设计了在线监测煤和其它含高挥发分组份样品的热解气体的反应器,将此反应器与商品型质谱(MS)联用,建立了常压程序升温热解-质谱(AP-TPP-MS)系统。用模型化合物和真实样品检验了该系统的可靠性和重复性,并探讨了通过预处理前后煤热解时CO2的逸出情况来反映煤脱羧效果的可行性。结果表明,此系统用于模型化合物热解时能获得响应好、重叠拖尾少、对称性好的气体逸出峰;用于氧化煤时能清晰可辨地显示同一热解气体的多个逸出峰;系统的稳定性和重复性较好。可利用此系统监测CO2的逸出情况,反映预处理对煤的脱羧效果。     

Numerical and laboratory prediction of smoke lofting in the atmosphere over large area fires

We analyze the lofting of aerosol in the atmosphere over a large scale fire. According to the well-known theory of “nuclear winter”, soot, rising in the atmosphere, may spread in the stratosphere and screen sun rays, which may in turn result in long-term catastrophic consequences for the climate. The height reached by the soot is critical for the climate modeling because long-term global consequences can only be caused by a significant quantity of soot injected into the stratosphere. Most of the studies in the present literature are devoted to long-term modeling. The study of the initial (pyrocumulus) stage of the problem has attracted much less attention with the amount of the soot injected into the mid-latitude stratosphere often being postulated. The amount of smoke that enters the stratosphere is crucial for climate consequences. It is therefore important to predict accurately the active stage of a large-scale fire, which is accompanied by the development of convective columns. The paper is devoted to the analysis of different approaches to the prediction of the altitude of smoke lofting over large scale fires. Some numerical, laboratory and analytical methods are considered. The latter two approaches are based on the theory of similarity. The results obtained by different techniques are compared with each other. Special attention is given to high resolution simulations, which accurately enough resolve gravity waves.     

New measurements of the water vapor continuum in the region from 0.3 to 2.7 THz

We present a spectroscopic study of the water vapor continuum absorption in the far-IR region from 10 to 90 cm⁻¹ (0.3-2.7 THz). The experimental technique combines a temperature-stabilized multipass absorption cell, a polarizing (Martin-Puplett) interferometric spectrometer, and a liquid-He-cooled bolometer detector. The contributions to the absorbance resulting from the structureless H₂O-H₂O and H₂O-N₂ continua have been measured in the temperature range from 293 to 333 K with spectral resolution of 0.04-0.12 cm⁻¹. The resonant water vapor spectrum was modeled using the HITRAN04 database and a Van Vleck-Weisskopf lineshape function with a 100 cm⁻¹ far-wing cut-off. Within experimental uncertainty, both the H₂O-H₂O and H₂O-N₂ continua demonstrate nearly quadratic dependencies of absorbance on frequency with, however, some deviation near the 2.5 THz window. The absorption coefficients of 3.83 and 0.185 (dB/km)/(kPa THz)² were measured for self- and foreign-gas continuum, respectively. The corresponding temperature exponents were found to be 8.8 and 5.7. The theoretically predicted foreign continuum is presented and a reasonable agreement with experiment is obtained.     

T-FTIR研究大气颗粒物表面非均相反应

大气颗粒物表面发生的非均相反应已成为目前大气科学领域的研究热点.由于现有的研究手段存在很多不足,目前人们对大气中痕量气体物质在颗粒物表面非均相反应动力学和机理了解得还很有限.文章开发了基于透射傅里叶变换红外光谱(T-FTIR)的研究颗粒物表面反应的方法,可以从分子水平观测颗粒物表面的物理化学变化.通过对一个大气模型反应体系即常温常压下甲基丙烯醛(MAC)在二氧化硅颗粒物表面反应的表征,验证了该方法可以有效地定性和定量表征颗粒物上的非均相反应过程.研究结果显示,反应过程的红外谱图信号清晰,表征灵敏;红外光能量较低,不会损害样品,可以实现对反应的原位观测.经HPLC分析结果证明,T-FTIR表征结果的重现性和准确性好,即使在湿度存在条件下其定性和定量也是可靠的.该方法为实验室模拟研究实际大气条件下的非均相反应提供了一种有效手段.     

Qualifying IMG tropical spectra for clear sky

The problem of cloud detection for the Interferometric Monitoring of Greenhouse Gases spectrometer has been addressed by considering a set of thresholding tests which takes full advantage of the high spectral resolution of the sensor. The methodology has been applied to a case study consisting of spectra recorded in the tropics on sea surface, although the scheme may be easily extended to other latitudes. The algorithm is very efficient because it uses only the observed spectrum and no on-line radiative transfer calculation is needed. Based on this cloud detection scheme a set of clear-sky tropical spectra have been identified to be used by the scientific community for further studies such as retrieval of atmospheric properties and high spectral resolution radiative transfer modeling.