Product study of the reaction of OH radicals with isoprene in the atmosphere simulation chamber SAPHIR     

M. Karl  H.-P. Dorn  F. Holland  R. Koppmann  D. Poppe  L. Rupp  A. Schaub  A. Wahner 《Journal of Atmospheric Chemistry》2006,55(2):167-187

Atmospheric oxidation of isoprene and its oxidation products methacrolein (MACR) and methyl vinyl ketone (MVK) have an important impact on the photochemical activity in the boundary layer, in particular in forested areas. The oxidation of isoprene by OH radicals was investigated in chamber experiments conducted under tropospheric conditions in the atmosphere simulation chamber SAPHIR at the Research Center Jülich. The aim was to determine the product yield of MVK and MACR in the OH-induced isoprene oxidation and the rate constant of their reaction with OH under real atmospheric conditions. The recently published updated degradation scheme for isoprene from Geiger et al. (2003) was used to determine rate constants and product yields. The fractional yields in the isoprene peroxy radical reaction with NO were found to be 0.41±0.03 for MVK and 0.27±0.03 for MACR. The rate coefficient for MACR with OH was found to be in very good agreement with the recommended value of IUPAC Atkinson (Atkinson et al., 2005). while the rate coefficient for MVK with OH was 27% lower.  相似文献   

土性指标和地层性质对水泥搅拌桩成桩质量的影响     

符学兵 《江苏地质》2007,31(4):370-372

从水泥土的固化机理出发,结合水泥搅拌桩桩身标准贯入试验和水泥土配合比试验,分析讨论了土性指标、土质条件和地层性质对水泥搅拌桩成桩质量的影响。  相似文献   

小口子泉水氡映震范围及能级研究     

訾少刚  延海军  梅浩  吕俊强  赵静 《内陆地震》2007,21(4):342-347

介绍了银川基准台小口子泉的概况以及水氡观测情况。研究了自1990以来银川台小口子泉周边地区300 km范围内ML4.0以上地震与银川台水氡资料的映震情况。通过对典型震例深入研究,总结了小口子泉水氡与周边地区地震活动的对应关系,探讨了小口子泉水氡对周边地区地震的对应范围和对应的震级范围。小口子泉水氡异常对该泉点西北方向的地震反映灵敏,且都是低值异常。  相似文献   

四川水氡测值突跳异常与地震     

官致君 《四川地震》2006,(4):32-36

在四川开展水氡前兆观测的初期,部分水氡点的水氡测值突跳异常很好地对应了其可预测范围内的中强以上地震。水氡测值突跳异常曾作为松潘—平武和盐源—宁蒗等地震预报的重要依据。但在水氡观测至今的完整时间段内,水氡突跳异常总体表现出对应率低,漏报率高的现象。多次预报攻关研究结果显示,水氡观测的异常表现是多种多样的,水氡测值突跳异常只是其中的表现之一。在今后四川及邻区的中强以上地震预报实践中,水氡测值突跳异常仍可作为地震短临预报的重要参考。  相似文献   

土氡测量在海口市活动断层探测中的初步应用   总被引：4，自引：0，他引：4  

王志成 《华南地震》2006,26(4):61-66

运用土壤氡射气(土氡)测量方法对海口市的六条隐伏断层进行探测,检验土壤氡射气(土氡)测量在海口市地区的有效性,结果表明,土氡测量探测晚更新世(Q3)和全新世(Q4)隐伏断层具有较好的效果,可以作为海口市活动断层探测一种有效手段。  相似文献   

Relationships between three dispersion measures used in flood frequency analysis     

I. Markiewicz  W. G. Strupczewski  K. Kochanek  V. P. Singh 《Stochastic Environmental Research and Risk Assessment (SERRA)》2006,20(6):391-405

Three dispersion measures of a random variable, i.e., the standard deviation, the mean deviation (MD) about the mean and the second L-moment, are analyzed in terms of their properties and mutual relationships. Emphasis is placed on the MD, as it is less recognized than two other dispersion measures. The relationships between the dispersion measures are derived for distributions commonly applied in flood frequency analysis (FFA). For distributions that are unbounded, there is a distribution-dependent constant value of the ratio of dispersion measures, or equivalently of respective coefficients of variation. For two-parameter distributions that are lower-bounded, the relationship between the coefficients of variation is also distribution dependent and is not linear. For lower-bounded three-parameter distributions, the dispersion measure ratios, or equivalently the ratios of coefficients of variation, depend on the coefficient of skewness and show a strong distributional dependence. For selected distributions, the three dispersion measures are compared both in terms of the robustness to the largest samples element and the accuracy of upper quantile estimation. The MD statistics may be highly competitive to the two other dispersion measure statistics if applied in FFA for parameters estimation.  相似文献   

Impact of climate change on wetland ecosystems: A critical review of experimental wetlands     

《Chemie der Erde / Geochemistry》2007

Climate change is identified as a major threat to wetlands. Altered hydrology and rising temperature can change the biogeochemistry and function of a wetland to the degree that some important services might be turned into disservices. This means that they will, for example, no longer provide a water purification service and adversely they may start to decompose and release nutrients to the surface water. Moreover, a higher rate of decomposition than primary production (photosynthesis) may lead to a shift of their function from being a sink of carbon to a source. This review paper assesses the potential response of natural wetlands (peatlands) and constructed wetlands to climate change in terms of gas emission and nutrients release. In addition, the impact of key climatic factors such as temperature and water availability on wetlands has been reviewed. The authors identified the methodological gaps and weaknesses in the literature and then introduced a new framework for conducting a comprehensive mesocosm experiment to address the existing gaps in literature to support future climate change research on wetland ecosystems. In the future, higher temperatures resulting in drought might shift the role of both constructed wetland and peatland from a sink to a source of carbon. However, higher temperatures accompanied by more precipitation can promote photosynthesis to a degree that might exceed the respiration and maintain the carbon sink role of the wetland. There might be a critical water level at which the wetland can preserve most of its services. In order to find that level, a study of the key factors of climate change and their interactions using an appropriate experimental method is necessary. Some contradictory results of past experiments can be associated with different methodologies, designs, time periods, climates, and natural variability. Hence a long-term simulation of climate change for wetlands according to the proposed framework is recommended. This framework provides relatively more accurate and realistic simulations, valid comparative results, comprehensive understanding and supports coordination between researchers. This can help to find a sustainable management strategy for wetlands to be resilient to climate change.  相似文献   

2003～2004年岷县-卓尼地震与甘肃东部地区水化异常的关系探讨     

张昱  陈瑶  李春燕 《高原地震》2007,19(3):17-20

分析了2003年11月13日岷县-卓尼5．2级地震以及2004年9月7日5．0级地震前甘肃地区水氡观测点和2个气体观测点的资料变化情况，发现地震前礼县水氡、西和水氡、武山I号泉水氡、清水温泉水氡以及武山2个气体观测点的几种气体存在不同程度的异常变化。  相似文献   

Magmatic structures in the Krkonoše–Jizera Plutonic Complex,Bohemian Massif: evidence for localized multiphase flow and small-scale thermal–mechanical instabilities in a granitic magma chamber     

Jiří Žák  Josef Klomínský 《Journal of Volcanology and Geothermal Research》2007

The present paper examines magmatic structures in the Jizera and Liberec granites of the Krkonoše–Jizera Plutonic Complex, Bohemian Massif. The magmatic structures are here interpreted to preserve direct field evidence for highly localized magma flow and other processes in crystal-rich mushes, and to capture the evolution of physical processes in an ancient granitic magma chamber. We propose that after chamber-wide mixing and hybridization, as suggested by recent petrological studies, laminar magma flow became highly localized to weaker channel-like domains within the higher-strength crystal framework. Mafic schlieren formed at flow rims, and their formation presumably involved gravitational settling and velocity gradient flow sorting coupled with interstitial melt escape. Local thermal or compositional convection may have resulted in the formation of vertical schlieren tubes and ladder dikes whereas subhorizontal tubes or channels formed during flow driven by lateral gradients in magma pressure. After the cessation or deceleration of channel flow, gravity-driven processes (settling of crystals and enclaves, gravitational differentiation, development of downward dripping instabilities), accompanied by compaction, filter pressing and melt segregation, dominated in the crystal mush within the flow channels. Subsequently, magmatic folds developed in schlieren layers and the magma chamber recorded complex, late magmatic strains at high magma crystallinities. Late-stage magma pulsing into localized submagmatic cracks represents the latest events of magmatic history of the chamber prior to its final crystallization. We emphasize that the most favorable environments for the formation and preservation of magmatic structures, such as those hosted in the Jizera and Liberec granites, are slowly cooling crystal-rich mushes. Therefore, where preserved in plutons, these structures may lend strong support for a “mush model” of magmatic systems.  相似文献   

一个观测冰核的15 L混合云室   总被引：1，自引：0，他引：1       下载免费PDF全文

杨绍忠  楼小凤黄庚 酆大雄 《应用气象学报》2007,18(5):716-721

小型混合云室常用于自然冰核浓度的观测和人工冰核成核率的检测。使用表明:由于受云室容积、造雾方法和操作程序等因素的影响, 检测结果有很大差异, 难以相互比较。为提高检测数据的可信性, 设计并制作了15 L混合云室。云室由F22压缩机系统制冷, 最低能达到-28℃。为减小云室温度的波动, 在云室外围设计有装满乙二醇-水溶液的夹套。在溶液中, 安装了1个1 kW的电加热器, 接通后可使云室升温。在夹套外, 采用发泡技术形成约10 cm厚的绝热层, 以使云室与外界绝热。云室运行时, 可通过控制压缩机和电加热器得到实验温度。此外, 为拓宽检测冰核浓度的检测范围, 设计了玻璃片接取显微镜读数和糖盘接取目测读数两种可供选择使用的冰晶观测方法, 前者在冰晶浓度高时使用 (人工冰核), 后者在低浓度时使用 (自然冰核)。另一个重要改进是:先由一个超声雾化器产生常温雾, 而后使常温雾穿过一个低温狭缝进行预冷, 当雾温等于或低于云室温度后再进入云室。这一措施不仅避免了瞬时高度过饱和, 而且还减小了对云室温度的扰动。该云室在弹载催化剂成核率的改进实验中发挥了重要作用, 曾用它对多个人工冰核复合配方进行了检测和对比。结果表明:云室具有较好的稳定性和重复性, 整体性能优于以往的同类云室。这一结果是由于改进了提供过冷雾的设计和冰晶接取方法得到的。  相似文献