Retrieval And Monitoring of Atmospheric Trace Gas Concentrations in Nadir and Limb Geometry Using the Space-Borne Sciamachy Instrument

The Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) onboard the European Envisat spacecraft performs continuous spectral observations of reflected, scattered and transmitted sunlight in various observation geometries. A unique feature of SCIAMACHY is the capability of probing the atmosphere in three different observation geometries:The nadir, limb, and occultation measurement modes. In nadir mode, column densities of trace gases are retrieved with a spatial resolution of typically 30× 60 km using the Differential Optical Absorption Spectroscopy (DOAS) technique (Platt and Perner, 1983). Alternating with the nadir measurement, vertical profiles of absorber concentration in the stratosphere are derived in limb and occultation. In this paper we present an overview over some applications of SCIAMACHY data in space-based monitoring of atmospheric pollution. The DOAS algorithms for the retrieval of total column amounts from nadir spectra are briefly described and case studies of pollution events are presented. We also illustrate the technique used to derive stratospheric concentration profiles from limb observations and show comparisons with other remote sensing systems. Special emphasis will be given to techniques, which take advantage of SCIAMACHY's different viewing geometries. In particular, we will discuss the potential and limits of strategies to infer tropospheric abundances of O₃and NO₂.     

The role of a changing Arctic Ocean and climate for the biogeochemical cycling of dimethyl sulphide and carbon monoxide

Dimethyl sulphide (DMS) and carbon monoxide (CO) are climate-relevant trace gases that play key roles in the radiative budget of the Arctic atmosphere. Under global warming, Arctic sea ice retreats at an unprecedented rate, altering light penetration and biological communities, and potentially affect DMS and CO cycling in the Arctic Ocean. This could have socio-economic implications in and beyond the Arctic region. However, little is known about CO production pathways and emissions in this region and the future development of DMS and CO cycling. Here we summarize the current understanding and assess potential future changes of DMS and CO cycling in relation to changes in sea ice coverage, light penetration, bacterial and microalgal communities, pH and physical properties. We suggest that production of DMS and CO might increase with ice melting, increasing light availability and shifting phytoplankton community. Among others, policy measures should facilitate large-scale process studies, coordinated long term observations and modelling efforts to improve our current understanding of the cycling and emissions of DMS and CO in the Arctic Ocean and of global consequences.     

High methane emissions from a littoral zone on the Qinghai-Tibetan Plateau

The littoral zones of lakes have been regarded as hotspots of methane (CH₄) fluxes through several studies. In the present study, we measured CH₄ fluxes in six kinds of littoral zones of Huahu Lake on the Qinghai-Tibetan Plateau in the peak growing season of 2006 and 2007. We found that CH₄ efflux (ranging from −0.1 to 90 mg CH₄ m⁻² h⁻¹) from the littoral zones of this lake was relatively high among those of boreal and temperate lakes. Our results also showed that emergent plant zones (Hippuris vulgaris and Glyceria maxima stands) recorded the highest CH₄ flux rate. The CH₄ flux in the floating mat zone of Carex muliensis was significantly lower than those of the emergent plant zones. CH₄ fluxes in the floating-leaved zone of Polygonum amphibium and bare lakeshore showed no significant difference and ranked last but one, only higher than that of the littoral meadow (Kobresia tibetica). Plant biomass and standing water depths were important factors to explain such spatial variations in CH₄ fluxes. No significant temporal variations in CH₄ fluxes were found due to the insignificant variations of physical factors in the peak growing season. These results may help in our understanding of the importance of the littoral zone of lakes, especially the emergent plant zone, as a hotspot of CH₄ emission.     

可燃气体(液体蒸气)爆炸测试装置的改进研究

以可燃气体(液体蒸气)爆炸测试装置改进为主线,综述国内外各种测试装置的优缺点。对不同装置、测试方法以及测试原理进行比较分析,研讨可燃气体爆炸的特点和爆炸参数测试方法以及对现有测试装置的改进方案。即对20 L爆炸测试装置的配气系统和控制系统进行了合理改进,使引射混合配气与循环混合配气相结合,使可燃气体(液体蒸气)与空气混合更均匀,控制操作更简便,还指出了今后研究工作中应注意的一些问题和研究重点。     

水稻土中半胱氨酸分解产生含硫气体的研究

在室内培养条件下,测定了水稻土中含硫气体的释放．结果表明,该土壤中有硫化氢(Ｈ２Ｓ),羰基硫(ＣＯＳ),二甲基硫(ＤＭＳ)三种气体释放．当土壤中加入半胱氨酸后,ＣＯＳ和Ｈ２Ｓ气体的浓度有了明显增加,并有ＣＳ２和ＣＨ３ＳＨ测出,而ＤＭＳ的浓度变化不大．这些结果表明半胱氨酸的分解可能是 ＣＯＳ,Ｈ２Ｓ,ＣＳ２和 ＣＨ３ＳＨ的产生源之一．在好氧(正常大气)条件下,Ｈ２Ｓ,ＣＯＳ,ＣＳ２和ＣＨ３ＳＨ的释放量低于厌氧(氮气氛围)条件下的释放量,ＤＭＳ则高于厌氧条件下．这表明水稻土中半胱氨酸分解产生 Ｈ２Ｓ,ＣＯＳ,ＣＳ２和 ＣＨ３ＳＨ需较强的还原条件,产生这四种气体的微生物需要严格的厌氧条件．产生ＤＭＳ的微生物则比前者需要高一些的含氧量．在光照条件下,各含硫气体的释放量普遍高于无光照条件下的释放量．释放含硫气体的大多数微生物适宜的含水率为５０%且对土壤的ｐＨ值有一定要求．     

Greenhouse Gases as Clues to Permanence of Farmlands

Abstract:  Farmlands are expansive, diverse, and intensively managed ecosystems. These lands, so critical to human welfare, are threatened by growing stresses as demand for food escalates, fresh water wanes, cheap fuels deplete, and other uses jostle for space. With these coming pressures, how can we foster permanence on the lands that sustain us? In this essay I contemplate the hypothesis that the greenhouse gases, because they emanate from the interwoven flows of C, N, and energy in ecosystems, can help steer us toward permanence (sustainability). Alongside other indicators these emissions may detect the ecosystem's pulse, alerting us to inefficiencies and guiding us to better practices. To be effective signals, however, the greenhouse gases will need to be considered in their local settings, monitored longer and in more "listening places," and measured across boundaries of disciplines and biomes. This approach may help reduce greenhouse gas emissions from our farmlands. But we may find that, in the long run, the main beneficiaries of our inquiry have been, not just the atmosphere, but our fragile lands, perhaps in ways we cannot yet foresee.     

甲烷-空气预混气体泄爆过程的实验研究

对甲烷-空气预混气体在球形容器和球形管道连通容器内的泄爆过程进行实验研究,根据实验结果得出在较小的泄压面积时,与密闭容器爆炸实验比较,不能降低容器内的最大压力,反而会增大容器内的最大压力。通过实验结果分析,泄爆口安装在远离点火源的位置,当发生预混气体爆炸时能较好地降低容器内的最大压力,起到保护容器的作用。     

The Potential of Soil Carbon Sequestration Through Improved Management Practices in Norway

The study was conducted to assess the potential of Norwegian agricultural ecosystems to sequester carbon (C) based on the data from some long-term agronomic and land use experiments. The total emission of CO₂ in Norway in 1998 was 41.4 million metric ton (MMT), of which agriculture contributed only 0.157 MMT, or <0.4% of the total emissions. With regards to methane (CH₄) and nitrous oxide (N₂O) gases, however, agricultural activities contributed 32.5% and 51.3% of their respective emissions in Norway. The soil organic carbon (SOC) losses associated with accelerated soil erosion in Norway are estimated at 0.475 MMTC yr^–1. Land use changes and soil/crop management practices with potential for SOC sequestration include conservation tillage methods, judicious use of fertilizers and manures, use of crop residues, diverse crop rotations, and erosion control measures. The potential for SOC sequestration is 0.146 MMTC yr^–1 for adopting conservation tillage, 0.011–0.035 MMTC yr^–1 for crop residue management, 0.026 MMTC yr^–1 for judicious use of mineral fertilizer, 0.016–0.135 MMTC yr^–1 for manure application, and 0.036 MMTC yr^–1 for adopting crop rotations. The overall potential of these practices for SOC sequestration ranges from 0.591 to 1.022 MMTC yr^–1 with an average value of 0.806 MMTC yr^–1. Of the total potential, 59% is due to adoption of erosion control measures, 5.8% to restoration of peat lands, 21% to conversion to conservation tillage and residue management, and 14% to adoption of improved cropping systems. Enhancing SOC sequestration and improving soil quality, through adoption of judicious land use and improved system of soil and crop management, are prudent strategies for sustainable management of soil, water and environment resources.Readers should send their comments on this paper to: bhaskarn ath@aol.com within 3 months of publication of this issue.     

METHANE FORMATION BY LAKE SEDIMENTS DURING IN VITRO INCUBATION1

ABSTRACT: Renewed (de novo) synthesis of methane gas was shown to occur when samples of lake sediment were dispersed on glass beads and incubated in a helium atmosphere at 23°C. Under the above conditions, sediment samples from hardwater and softwater lakes generated up to 440 nanomoles and 80 nanomoles per ml of sediment per two days, respectively. At the time of collection, sediment samples possessed approximately similar amounts of “native” methane. Nitrate, sulfate, and acetylene were shown to suppress methane synthesis by sediment incubated as described.     

Soil phytoremediation from the breakdown products of the chemical warfare agent, yperite

A plant-based bioremediation (phytoremediation) strategy has been developed and shown to be effective for the clean-up of soil contaminated by the breakdown products of the chemical warfare agent (CWA), yperite. The method involves exploiting the plant growth hormone, indole-3-acetic acid (IAA), to intensify the phytoremediation. For determination of the yperite breakdown products, gas chromatography is used. Soil and plant samples were analysed with a gas chromatograph fitted with an atomic emission detector. The method of standard-free determination was employed to identify sulphur-containing substances (SCSs). A series of soil tests was conducted, which showed that the level of SCSs decreased 4, 8, and more than 20-fold compared with that found in contaminated soil. This decrease was dependent upon the IAA concentrations used for plant treatment. The treated plants accumulated 2.7 to 2.9-fold larger amounts of the SCSs than did the untreated plants. Owing to its simplicity, environmental safety and inexpensiveness, the method can be recommended for the restoration of soil fertility in areas of storage and destruction of blister CWAs.