硫酸盐-甲烷界面与甲烷通量及下伏天然气水合物赋存的关系

硫酸盐-甲烷界面在富甲烷和含天然气水合物的海洋沉积区已经成为一个重要的生物地球化学识别边界。在硫酸盐-甲烷界面之上,沉积物中的硫酸盐因参与分解有机质和甲烷厌氧氧化反应而被消耗,而其界面之下沉积物中的甲烷则不断生成,含量逐渐增加。根据该界面附近硫酸盐浓度和甲烷浓度的变化特征,可以判断该区甲烷流体通量的大小,从而指示下伏天然气水合物的可能赋存状况。南海北部陆坡的柱状沉积物孔隙水数据的分析显示,硫酸盐-甲烷界面埋深比较浅,表明该海域的甲烷通量较高。这种高甲烷通量很可能是由下伏的天然气水合物所引起的,并暗示着该区下伏海底可能有天然气水合物沉积层赋存。     

Inversion of multiple thermal indicators: Quantitative methods of determining paleoheat flux and geological parameters IV. Case histories using thermal indicator tomography

A quantitative tomographic method to determine simultaneously several geological, geochemical, and geothermal parameters associated with reconstruction of the geohistory and thermal history of sediments in a well is presented. Using vitrinite reflectance data from the well Inigok-1, National Petroleum Reserve of Alaska, the numerical algorithm was tested and found to be effective in delineating the variation of heat flux with time. In addition, the size and timing of a major unconformity also were bracketed. Application of tomography using apatite fission track distributions with depth as a thermal indicator enabled not only the thermal history of two wells in the NW Canning Basin of Australia to be determined, but also the chemical parameters associated with fission track annealing to be constrained. Results of both the Alaska study and the Australian study were consistent with the qualitative behavior inferred from current geological models.     

How to Reach Superequipartition Field Strengths in Solar Magnetic Flux Tubes

A number of independent arguments indicate that the toroidal flux system responsible for the sunspot cycle is stored at the base of the convection zone in the form of flux tubes with field strength close to 10⁵ G. Although the evidence for such strong fields is quite compelling, how such field strength can be reached is still a topic of debate. Flux expulsion by convection should lead to about the equipartition field strength, but the magnetic energy density of a 10⁵-G field is two orders of magnitude larger than the mean kinetic energy density of convective motions. Line stretching by differential rotation (i.e., the “Ω effect” in the classical mean-field dynamo approach) probably plays an important role, but arguments based on energy considerations show that it does not seem feasible that a 10⁵-G field can be produced in this way. An alternative scenario for the intensification of the toroidal flux system in the overshoot layer is related to the explosion of rising, buoyantly unstable magnetic flux tubes, which opens a complementary mechanism for magnetic-field intensification. A parallelism is pointed out with the mechanism of “convective collapse” for the intensification of photospheric magnetic flux tubes up to field strengths well above equipartition; both mechanisms, which are fundamentally thermal processes, are reviewed.     

风蚀影响因子的敏感性试验

 对风蚀模式的各重要影响因子进行了敏感性试验，结果表明：①随风力的增大，跃动沙粒的粒径范围迅速增大，从而会使更多、更大的尘粒因受到更强烈的撞击作用而释放于空中。但随土壤水分和植被覆盖度的增加，跃动沙粒粒径范围会变窄，较大的粒子很难被激发到空中。②各种土壤沙流通量及尘粒释放率随粒径的变化趋势Q(d)和F(d)与相应的地表土壤有效粒度分布Ps(d)具有相似的特征，说明前人用近地层沙尘粒度分布来代表地表土壤的有效粒度分布是合理的。③若以总沙流通量Q>0.5 g·m^-1·s^-1为风蚀过程开始发生的标准，在干燥、裸露的情况下，沙土、沙壤土、壤土、黏土和粉黏土表面发生风蚀的临界摩擦速度都约为0.3 m·s^-1。相同风力条件下（u*=0.6 m·s^-1），若地表干燥（w=0）并忽略小于0.1 g·m^-1·s^-1的总沙流通量，则抑制5种土壤发生风蚀的最小植被覆盖度分别约为：沙土0.35、沙壤土0.45、壤土0.45、黏土0.55、粉黏土0.55；若地表裸露，抑制风蚀发生的最小水分含量分别为：沙土0.15、沙壤土0.18、壤土0.3、黏土0.36和粉黏土0.33。④通常情况下沙土最不易起尘，它在各个粒径的尘粒释放率比其他土壤均约小3~5个量级。粉黏土最易起尘，且粒径较小，较容易传输到下游很远处。⑤总尘粒释放率F和总沙流通量Q随风力、地表条件的变化一般是同相的，即Q增大，F也会增大。⑥一般情况下F随摩擦速度u*的增大或植被覆盖度cf和土壤水分w的减小而增大；土壤拖曳系数sx和弹性压力垂直分量pye的增加会大大降低尘粒释放率。⑦通常风蚀情况下，5种土壤中粉黏土和沙壤土因聚合粒子破碎产生的尘粒释放率Fc最大，Fc随风力、地表条件变化的敏感度也最强；沙土的Fc最小，其对风力、地表条件的敏感度也最弱。     

北冰洋78°N冰站近地层参数的观测研究

利用2003年8月22日-9月3日中国北极科学考察队在北冰洋78°N浮冰站获得的近地层观测资料,采用整体输送法对北冰洋浮冰近地层特征参数进行了分析研究。结果表明,在考察期间,雪面吸收的净辐射仅为3.6 W/m2,其中以感热和潜热向大气输送的能量分别占52%和31%,向海冰深层传导的热量很少;近中性层结条件下的平均拖曳系数Cdn为1.16×10-3,略小于75°N北冰洋浮冰上近中性层结的Cdn。与1999年75°N附近冰站观测结果的对比表明,当海冰密度及冰站所在浮冰的尺度不同时,海冰与大气相互作用的热力学和动力学过程的差异显著,在研究北冰洋地区海/冰/气相互作用对气候过程影响时,应考虑这一问题。     

非对称天然沸石陶瓷膜的制备及其性能表征

利用天然沸石为主要原料,制备出具有过滤功能和重金属离子吸附功能的天然沸石非对称陶瓷膜。非对称膜中支撑体、中间层膜和顶层膜的平均孔径分别为6.6μm、0.6μm和0.1μm。非对称膜单位压力降(1 MPa)下的氮气通量和水通量分别为:24.69×103m3/(m2h)和1.87×103m3/(m2h);对重金属离子(铅离子)吸附交换能力为7.13 mg/g。     

Generic precursors to coastal earthquakes: Inferences from Denali fault earthquake

Recent research has shown evidence of strong coupling between the atmosphere and lithosphere in coastal regions, associating abnormal atmospheric phenomena to the occurrence of strong earthquakes. Surface latent heat flux (SLHF), total column water vapor (CWV), relative humidity (RH) and total ozone column (TOC), analyzed over the epicentral region of the Denali fault earthquake of November 3, 2002, exhibit anomalous behavior that could be related to the earthquake preparatory process and its occurrence. The complementary nature of the parameters provides strong support that the anomalous values were driven by lithospheric processes, rather than other atmospheric phenomena. Due to the wide availability of remote sensing observations of atmospheric parameters, the detection of anomalies can be used to mitigate the earthquake risks.     

Soil organic carbon storage and soil CO_2 flux in the alpine meadow ecosystem

High-resolution sampling,measurements of organic carbon contents and 14C signatures of selected four soil profiles in the Haibei Station situated on the northeast Tibetan Plateau,and application of 14C tracing technology were conducted in an attempt to investigate the turnover times of soil organic car-bon and the soil-CO2 flux in the alpine meadow ecosystem. The results show that the organic carbon stored in the soils varies from 22.12×104 kg C hm-2 to 30.75×104 kg C hm-2 in the alpine meadow eco-systems,with an average of 26.86×104 kg C hm-2. Turnover times of organic carbon pools increase with depth from 45 a to 73 a in the surface soil horizon to hundreds of years or millennia or even longer at the deep soil horizons in the alpine meadow ecosystems. The soil-CO2 flux ranges from 103.24 g C m-2 a-1 to 254.93 gC m-2 a-1,with an average of 191.23 g C m-2 a-1. The CO2 efflux produced from microbial decomposition of organic matter varies from 73.3 g C m-2 a-1 to 181 g C m-2 a-1. More than 30% of total soil organic carbon resides in the active carbon pool and 72.8%―81.23% of total CO2 emitted from or-ganic matter decomposition results from the topsoil horizon (from 0 cm to 10 cm) for the Kobresia meadow. Responding to global warming,the storage,volume of flow and fate of the soil organic carbon in the alpine meadow ecosystem of the Tibetan Plateau will be changed,which needs further research.     

Anomalous Emissions of SO2 During the Recent Eruption of Santa Ana Volcano, El Salvador, Central America

Santa Ana volcano in western El Salvador, Central America, had a phreatic eruption at 8:05 am (local time) on October 1, 2005, 101 years after its last eruption. However, during the last one hundred years this volcano has presented periods of quiet degassing with fumarolic activity and an acidic lake within its crater. This paper presents results of frequent measurements of SO₂ degassing using the MiniDOAS (Differential Optical Absorption Spectroscopy) system and a comparison with the volcanic seismicity prior to the eruption, during, and after the eruption. Vehicle measurements of SO₂ flux were taken every hour during the first nine days of the eruption and daily after that. The period of time reported here is from August to December, 2005. Three periods of degassing are distinguished: pre-eruptive, eruptive, and post-eruptive periods. The intense activity at Santa Ana volcano started in July 2005. During the pre-eruptive period up to 4306 and 5154 ton/day of SO₂ flux were recorded on October 24 and September 9, 2005, respectively. These values were of the same order of magnitude as the recorded values just after the October 1^st eruption (2925 ton/day at 10:01 am). Hourly measurements of SO₂ flux taken during the first nine days after the main eruptive event indicate that explosions are preceded by an increase in SO₂ flux and that this parameter reaches a peak after the explosion took place. This behavior suggests that increasing accumulation of exsolved magmatic gases occurs within the magmatic chamber before the explosions, increasing the pressure until the point of explosion. A correlation between SO₂ fluxes and RSAM (Real Time Seismic Amplitude Measurements) is observed during the complete sampling period. Periodic fluctuations in the SO₂ and RSAM values during the entire study period are observed. One possible mechanism explaining these fluctuations it that convective circulation within the magmatic chamber can bring fresh magma periodically to shallow levels, allowing increasing degasification and then decreasing degasification as the batch of magma lowers its gas content, becomes denser, and sinks to give space to a new magma pulse. These results illustrate that the measurements of SO₂ flux can provide important warning signals for incoming explosive activity in active volcanoes.