Influence of the surface microlayer on the flux of nonconservative trace gases (CO,H2, CH4, N2O) across the ocean-atmosphere interface

Gas exchange experiments were conducted in the tropical Atlantic Ocean during a ship expedition with FS Meteor using a small rubber raft. The temporal change of the mixing ratios of CO, H₂, CH₄ and N₂O in the headspace of a floating glass box and the concentrations of these gases in the water phase were measured to determine their transfer velocities across the ocean-atmosphere interface. The ocean acted as a sink for these gases when the water was undersaturated with respect to the mixing ratio in the headspace. The transfer velocities were different for the individual gases and showed still large differences even when normalized for diffusivity. Applying the laminar film model, film thicknesses of 20 to 70 m were calculated for the observed flux rates of the different gas species. When the water was supersaturated with respect to atmospheric CO, H₂, CH₄ and N₂O, the transfer velocities of the emission process were smaller than those determined for the deposition process. In case of H₂ and CH₄, emission was even not calculable although, based on the observed gradient, the laminar film model predicted significant fluxes at the air-sea interface. The results are interpreted by destruction processes active within the surface microlayer.     

Production of N2O,CH4, and CO2 from soils in the tropical savanna during the dry season

Emissions of N₂O, CH₄, and CO₂ from soils at two sites in the tropical savanna of central Venezuela were determined during the dry season in February 1987. Measured arithmetic mean fluxes of N₂O, CH₄, and CO₂ from undisturbed soil plots to the atmosphere were 2.5×10⁹, 4.3×10¹⁰, and 3.0×10¹³ molecules cm^-2 s^-1, respectively. These fluxes were not significantly affected by burning the grass layer. Emissions of N₂O increased fourfold after simulated rainfall, suggesting that production of N₂O in savanna soils during the rainy season may be an important source for atmospheric N₂O. The CH₄ flux measurements indicate that these savanna soils were not a sink, but a small source, for atmospheric methane. Fluxes of CO₂ from savanna soils increased ninefold two hours after simulated rainfall, and remained three times higher than normal after 16 hours. More research is needed to clarify the significance of savannas in the global cycles of N₂O, CH₄, CO₂, and other trace gases, especially during the rainy season.     

The role of vibrationally excited nitrogen in the ionosphere

Theoretical and experimental aspects of the production, transformation, diffusion and loss of N₂ in the upper atmosphere are considered. The N₂-CO₂ near-resonant system in theD andE regions is taken into account. We describe our understanding of the methods necessary to find the vibrational populations of N₂ and CO₂ (asymmetric mode of CO₂). The calculations of the vibrational temperatures in theD, E, andF regions for the mid-latitude ionosphere and an aurora are presented. The connection between the excited species and the 4.26-m radiation intensities is considered. The models for the rate coefficient of the reaction of O⁺ with N₂ and the electron density decrease resulting from N₂ in the F region are discussed.     

多元统计在大洋玄武岩同位素端元识别中的应用

应用因子分析的方差最大旋转和非线性映射方法对海洋玄武岩Sr、Nd、Pb同位素数据在多维空间中的数据结构进行了分析。研究表明这些数据在多维空间中呈五角形结构,并对应5个地幔端元:大西洋中脊玄武岩(DMM),圣埃伦那(HIMU),鲸岛(EMI),萨摩亚岛(EMII)和DS(EMIII).其中DS(EMIII)是本文新识别出来的一个地幔端元,它可能是重新进入地幔的具有较高古老放射成因Pb的下地壳物质。     

祁县王村锶—偏硅酸饮用天然矿泉水

王村矿泉水为松散岩类孔隙水和碎屑岩裂隙水的混合水。它受深循环远源补给。矿泉水的动态稳定、水质优良、口感纯正，属锶—偏硅酸饮用天然矿泉水，是山西较好的饮用矿泉水源之一，有良好的开发前景。稷山南阳矿泉水是一个含锶—锌—偏硅酸等多种微量元素的重碳酸硫酸钠型饮用天然矿泉水。该矿泉水处于侯马断陷盆地内次一级断裂的复合部位，赋存于中更新统中下部的中细砂层中。水量丰富，涌水量可达８００ｍ￣３／ｄ。此矿泉水动态稳定，口感纯正，产地环境优美，无任何污染。自１９８８年发现，１９８９年开发利用至今，该矿泉水、矿泉饮料畅销不衰，是一处具有发展远景的优质矿泉水。     

临汾市东亢锌－锶－偏硅酸优质饮用天然矿泉水

东亢矿泉水处于临汾断陷盆地边缘山前地带。矿泉水赋存于石炭系、奥陶系及侵入岩体的裂隙中。单井涌水量达７１．４ｍ￣３／ｈ，水位埋深５１．０９ｍ。矿泉水中锌、锶、偏硅酸分别为０．２８９ｍｇ／Ｌ，１．２８ｍｇ／Ｌ，３３．２８ｍｇ／Ｌ，属锌锶偏硅酸－重碳酸·硫酸－钠型优质矿泉水，具有良好的开发前景。     

Simulation of flow over pool-riffle topography: A consideration of the velocity reversal hypothesis

Computer flow simulations using the HEC-2 step-backwater routine are used to demonstrate the effect of systematically varying river channel width, riffle spacing and channel roughness on the shear velocity, section-mean velocity and energy slope in fixed-bed pool-riffle sequences. Initial scaling is obtained by utilizing published information on hydraulic parameters within reaches of the River Severn. Subsequently this restriction is relaxed and the effect of varying parameter combinations within realistic limits is explored. The purpose of this exercise is to isolate those scenarios which may preclude or promote the occurrence of a competence ‘reversal’, such that pools scour at high flow whilst deposition occurs on riffles. It is concluded that rivers in which pools are hydraulically rougher than riffles are likely to demonstrate a competence reversal. For prescribed conditions, the critical discharge at which a reversal occurs is a negative function of riffle spacing and riffle width relative to pool width. Downstream variation in hydraulic roughness also has implications for the phase relationship of shear velocity maxima and minima in relation to the extremes in pool-riffle topography.