怀安盆地北缘断裂东段土壤气体地球化学特征

活动断裂带的土壤气体地球化学测量在活动断裂危险性评价方面起着重要作用。 本文讨论了怀安盆地北缘断裂东段的土壤气体地球化学特征及其构造意义。 我们于2012年7月和2013年6月在怀安盆地北缘断裂东段的羊窖沟以及张家窑两地现场测量了土壤气体组分的浓度和通量。 测量结果表明: ① 断裂带土壤气H₂、 Rn、 CO₂和Hg浓度空间分布曲线呈现双峰模式, 且断裂下盘土壤气的Rn、 CO₂和Hg浓度较上盘的高; H₂、 Rn、 CO₂和Hg浓度平均值分别是4.61 ppm、 4.81 k Bqm^-3、 0.38%和9 ngm^-3; 土壤气Rn和CO₂的通量平均值分别是6718 Bqm^-2d^-1和49.83 gm^-2d^-1; ② 土壤气Rn和CO₂在两个测区脱气强烈, 羊窖沟地区土壤气CO₂、 Rn和Hg浓度平均值以及土壤气Rn和CO₂通量值较张家窑地区高。 这些结果可能是两个测区断裂活动性差异引起的。     

川滇块体边界断裂的CO2释放及其来源

川滇块体边界断裂沿线及附近地区有大量的CO_2泉出露,其分布与1900年以来强震震中的分布大体一致,这表明该区CO_2释放可能与现代地震活动有直接关联。稳定碳、氧同位素证据表明,现代活动断裂释放的CO_2绝大部分来自地壳深部,并有两种主要的释放机制。现代活动断裂既可以直接产生大量的热动力变质成因CO_2,又可以作为通道释放来自下地壳甚至上地慢的CO_2组分。连续监测深源CO_2的释放动态有可能获得反映震源物理化学变化的地震前兆信息。     

滇池东北岸生态修复区的环境效应——Ⅱ.污染净化效应

研究了滇池东北沿岸带生态修复区去除水体中污染物和营养盐的能力．对修复区在重富营养水体迎风岸、无陆源污染情况下通过收获水生植物和促进悬浮物沉降方式去除的湖泊内源污染物质进行了定量的监测分析．结果显示,修复区对外来的悬浮物质具有强大的凝集、固定作用,植被区内每平方米湖面平均年沉积量达118．9 kg(干重),其中的氮、磷、有机碳含量分别达120 g／(m2·a)、70 g／(m2·a)、1080 g／(m2·a):修复区内的底质环境得到明显改善,表层沉积物中氮和有机碳含量比原初提高了4倍以上;修复区内水生植被具有极高的生产能力,仅2002年修复区就收割打捞水生植物113t(干重),由此去除氮、磷分别为30．0 g／(m2·a)和4．8 g／(m2·a).因此,沿岸带生态修复完全可以作为湖泊内源污染净化的一项工程措施在滇池东北沿岸或类似重污染水体推广应用．     

土层分层参数不确定时对二维工程场址地震动影响分析

工程场地地震安全性评价中计算二维复杂场地地震反应分析时,如采用一维等效线性化分析模型会带来较大的误差,而直接采用二维的非线性模型在技术上还存在一定的困难和不合理性。目前工程中多采用对一维分析结果进行二维修正的思想给出设计地震动及反应谱。然而在建立二维分析模型时,由于勘测条件的限制使模型建立出现很多不确定性。基于以往提出的二维复杂工程场址设计地震动的修正分析思想,建立了几种可能且工程认可的二维复杂场地模型,主要研究不同分层特征模型及土层剪切波速这一物理参数不确定时对设计地震动的影响,进一步考虑不同场地类别下,不同二维分层模型及土体物理参数对地震动的影响。根据分析结果提出了不同类别场地下,方便且合理建立二维复杂场地地震动分析模型的方法,为实际工程中模型的建立及参数的选取提供一些参考。     

Modelling the effects of changes in the Earth's magnetic field from 1957 to 1997 on the ionospheric hmF2 and foF2 parameters

We have modelled the effects of changes in the Earth's magnetic field on the ionosphere as have occurred from 1957 to 1997 using the NCAR Thermosphere–Ionosphere–Electrodynamics General Circulation Model. Previous studies that attempted to quantify these effects used a constant wind field, so that any electro-dynamical coupling processes could not be accounted for. Using TIE-GCM we can account for these processes. We find substantial changes in the F2 layer peak height hmF2 (up to ±20 km) and critical frequency foF2 (up to ±0.5 MHz) over the Atlantic Ocean and South America, purely due to changes in the Earth's magnetic field (i.e. unrelated to greenhouse gas cooling effects, which are often held responsible for long-term trends in hmf2 and fof2). These would make up a significant contribution to observed long-term trends in these areas and therefore must be taken into account in their interpretation. Modelled trends of hmF2 and foF2 exhibit a strong seasonal and diurnal variation, highlighting the importance of separating data with respect to season and local time. Most of the modelled changes in hmF2 and foF2 can be related to changes in plasma transport up or down magnetic field lines driven by neutral winds, changes, which are mostly caused by changes in the inclination of the field, though changes in declination and neutral wind also play a role. Changes in the vertical component of the E×B drift seem to have little effect on hmF2 and foF2.     

Variations in <Emphasis Type="Italic">foF</Emphasis>2 at the end of the 1990s and the beginning of the 2000s according to the SPIDR system data

Variations in the critical frequency of the F2 layer at 22 ionospheric stations within the period 1990–2010 according to the SPIDR system data are considered. A confirmation of the negative trends in foF2 for seven stations considered by one of the authors earlier on the basis of median data is obtained. It is found that both negative (a decrease in foF2 with time) and positive (growth in foF2 with time) trends of the critical frequency are observed. During the later part of the considered period (after 1997), negative trends dominate. This fact manifests itself, apparently, in an increase in the role of the decrease in the thermospheric neutral temperature in the formation of foF2 trends.     

晚喜山期以来四川盆地构造-热演化模拟

四川盆地位于扬子板块西缘,是我国重要的含油气盆地之一.25 Ma以来的晚喜山期是四川盆地构造-热演化的重要时期,此时,盆地大部分区域受到挤压处于隆升剥蚀的构造动力学环境.本文采用有限元数值模拟方法,基于二维瞬态热传导(含平流项)的基本方程,并引入修正的Airy均衡理论模型,通过覆盖全盆地的八条剖面模拟研究了晚喜山期以来四川盆地的构造-热演化特征,且利用现今大地热流对模拟结果进行了有效约束.模拟结果显示在晚喜山期(~25 Ma)川中地区地表热流较高,为60~64 mW/m²;川西南地区次之,为60~62 mW/m²;川东北地区最低,为50~54 mW/m².该期基底热流,也是川中隆起区热流高,川东北强烈剥蚀区热流低.热流的空间分布特征揭示了四川盆地深部动力学机制.四川盆地晚喜山期以来,抬升剥蚀作用降低了其地表热流和基底热流,其降低幅度与对应的剥蚀速率相关,即剥蚀速率越大,这种降低作用越明显.     

2014年四川康定双震震源的勒夫波分析

2014年11月22日在四川省康定县发生了M_S6.3地震(M1),3天后几乎在同一地点又发生了M_S5.8地震(M2),本文称其为"康定双震".首先,利用逆时成像技术对康定双震以及用作经验格林函数事件的一次M_L4.8地震(G1)进行了重定位,并利用广义极性振幅技术反演了三次地震的震源机制;然后,借助于G1的记录,利用经验格林函数技术分别提取了M1和M2的勒夫波视震源时间函数,并利用视震源时间函数的方位依赖性分析了M1和M2的优势破裂方向;最后,利用视震源时间函数反演方法反演了M1和M2的震源破裂过程.重定位结果表明,G1与M1和M2震源位置比较接近,分别相距~40 km和~50 km.震源机制反演结果表明,G1与M1和M2具有类似的机制,均为陡倾角左旋走滑.视震源时间函数的方向性分析表明,M1的破裂优势方向为276°,而M2的破裂优势方向为336°.破裂过程反演结果表明,M1持续时间~11 s,主要破裂区沿断层面朝北西以及浅表拓展,最大位错~0.52 m;M2持续时间~7 s,破裂区沿着断层面也朝北西以及浅部拓展,最大位错~0.33 m.     

三江平原沼泽地主养鲤鱼塘能量转换效率研究

对1988～1992年三江平原沼泽地泥炭池主养鲤鱼生态系统的能量转换效率进行了研究分析。结果表明,一个生长期浮游植物毛初级生产力对太阳辐射能的转换效率为0.204～0.308％;鲢鳙净产量对浮游植物净产量的转换效率为1.195～4.815％;太阳能转换为鱼类总净产量的生态学效率为0.067～0.123％。总辅助能、总生物能和饲料辅助能转换为鱼类总净产量的效率分别为8.91～14.05％、10.96～17.20％和11.06～17.57％.在2500kg/hm~2、3500kg/hm~2及5000kg/hm~2三个净产量级型池塘中,以5000kg/hm~2产量级的能量转换效率为最佳型。     

Very low-grade metamorphism of the Meso-Neoproterozoic and the Lower Paleozoic along the profile from Huangtudian to Xianxi in the central-northern part of Hunan Province,China

The Lengjiaxi and Banxi groups of the Meso-Neoproterozoic and the Sinian to the Lower Paleozoic occur along the profile from Huangtudian to Xianxi in the central-northern Hunan Province, China. Previous studies on the metamorphism around the area did not …     

Variations in <Emphasis Type="Italic">foF</Emphasis>2 and <Emphasis Type="Italic">hmF</Emphasis>2 at the end of the 1990s and the beginning of the 2000s

This article considers sparse available data on variations in the main parameters of the ionospheric F2 layer foF2(ss + 2) and hmF2(ss + 2) at the end of the 1990s and the beginning of 2000s. It is shown that the monotonous behavior of hmF2(ss + 2) obtained in earlier publications for the period after 1980 is violated. The hmF2(ss + 2) behavior obtains a more complicated nature by time with a tendency towards a decrease in hmF2(ss + 2) at the beginning of a new century. A statistically significant relationship between foF2(ss + 2) and hmF2(ss + 2) is discovered confirming the Rishbeth statement that during the first hours after sunset, the critical frequency foF2 is governed by dynamical processes via changes in the F2-layer height. It is found that at the end of the interval in question, there is a tendency towards deviations from the above-mentioned dependence. The latter could be a manifestation of the fact that changes in the aeronomical parameters caused by the general cooling and contraction of the thermosphere begin influencing the foF2 value. It is found that in the summer months, the foF2(ss + 2) value demonstrated a systematic decline tendency from the “boundary date” towards the beginning of the 2000s.     

水平螺旋度与沙尘暴的动力学关系研究

应用2002～2006年高空流场和地面观测资料,计算近地面至500 hPa水平螺旋度的大小.结果表明：水平螺旋度负值中心值越大,500 hPa到近地面风速越大,西风增强,风速垂直切变越大,辐合上升运动越强,形成沙尘暴的强度就越强.水平螺旋度负值中心常常在河西走廊附近最强,导致其下游东南方发生沙尘暴.水平螺旋度负值中心与其下游沙尘暴发生强度有一致的对应关系：当水平螺旋度负值中心≤-200 m²/s²时,未来24小时内该区下游将有沙尘天气出现,当≤-600 m²/s²时,6小时内该区下游将有能见度小于500 m的强沙尘暴天气出现,当≤-1000 m²/s²时,6小时内该区下游将有能见度小于50 m的特强沙尘暴天气出现.     

Atmospheric carbon dioxide and the long-term control of the Earth’s climate

A CO₂-weathering model has been used to explore the possible evolution of the Earth’s climate as the Sun steadily brightened throughout geologic time. The results of the model calculations can be described in terms of three, qualitatively different, “Megaclimates”. Mega-climate 1 resulted from a period of rapid outgassing in the early Archean, with high, but declining, temperatures caused by the small weathering rates on a largely water-covered planet. Mega-climate 2 began about 3 Gyear ago as major continental land masses developed, increasing the weathering rate in the early Proterozoic and thereby depleting the atmospheric CO₂ concentration. This process produced the first Precambrian glaciations about 2.3 Gyear ago. During Mega-climate 2, evolutionary biological processes increased the surface weatherability in incremental steps and plate tectonics modulated the CO₂ outgassing rate with an estimated period of 150 Myear (approximately one-half the period for the formation and breakup of super continents). Throughout Mega-climate 2 the surface temperature was controlled by variations in the atmospheric CO₂ level allowing transitions between glacial and non-glacial conditions. The results of the model for Mega-climate 2 are in agreement with the occurrence (and absence) of glaciations in the geologic record. Extending the model to the future suggests that CO₂ control of the Earth’s temperature will no longer be able to compensate for a solar flux that continues to increase. The present level of atmospheric CO₂ is so small that further reduction in CO₂ cannot prevent the Earth from experiencing Mega-climate 3 with steadily increasing surface temperatures caused by the continued brightening of the Sun. During Mega-climate 3, the main danger to the biosphere would come not from an increasing temperature but from a decreasing (rather than an increasing) CO₂ level which could, in time, fall below 0.5 PAL, causing serious damage to the biosphere. Fortunately, the rates of change due to solar brightening are slow enough that Mega-climate 3 appears to pose no threat to the biosphere for the next 0.5-2 Gyear.     

Behavior of parameters of the ionospheric F2 layer at the turn of the Centuries: 1. critical frequency

The available massifs of experimental data on the critical frequency of the ionospheric F2 layer, foF2, covering the first decade of the new century, are considered. On the basis of studying these massifs, a conclusion is drawn that the scatter of foF2 values (measured by the standard deviation (SD)) relative to the dependence on solar activity has grown substantially over recent decades as compared to the period 1958–1979. The possible causes of the SD increase are considered. It is shown that the foF2 values for the period 1998–2010 decreased as compared to the period 1958–1979 by an average of 0.6 MHz which gives an estimate of the foF2 trend of ～-0.03 MHz per year. Linear trends in foF2 for some ionospheric stations are analyzed. It is obtained that, in spite of the scatter in the data, it is possible to obtain statistically significant trends for each considered situation (day and postsunset period in summer and winter). At the same time, the winter negative trends (～-0.052 MHz per year) are approximately a factor of 2 higher than the summer ones (～-0.024 MHz per year). Comparisons with the trends obtained for earlier periods show that the negative trend in foF2 increased substantially towards the first decade of our century.     

Optimization of the Sampling Technique for the Determination of Dissolved Hydrogen in Groundwater

In this study a field‐sampling technique for dissolved hydrogen (H₂) in groundwater will be presented which allows the transport of gaseous samples into the laboratory for further analysis. The method consists of transferring the headspace trapped in a gas‐sampling bulb which is continuously purged by groundwater into previously evacuated vials using a gas‐tight syringe. Three transfer steps with preceding evacuation of the vial led to a H₂‐recovery of 100 % in laboratory experiments. The method has been applied to determine H₂ concentrations in an aquifer contaminated with chlorinated solvents. Tests concerning the effect of different pumping techniques on H₂ concentrations revealed that most reliable values were obtained with a bladder pump, while an electrically driven submersible pump generated considerable amounts of hydrogen due to electrochemical interactions with the sampled water. Concentrations of dissolved hydrogen in field and laboratory samples were about two orders of magnitude higher when sampling was performed with the electrically driven submersible pump compared to sampling with the bladder pump and a peristaltic pump. Lab experiments with a Plexiglas reservoir to produce H₂‐enriched water were used to study the effect of two tubing materials (PVC, polyamide) on H₂ losses. PVC tubing turned out to allow transfer of H₂‐enriched water over 25 m without significant losses, while PA‐tubing was not suitable for sampling of H₂.     

Behavior of parameters of the ionospheric F2 layer at the edge of the centuries: 2. Height of the layer

The trends in the height of the ionospheric F2 layer, hmF2, for the period from the end of the 1990s to the beginning of the 2010s are considered. It is shown that for a majority of the considered situations (time of the day plus season) negative trends are obtained for all stations for which series of initial data satisfying the requirements were found. They vary from ?1.2 to ?3.1 km per year. The trends in the daytime are slightly higher than in the postsunset period which apparently manifests the influence of the contraction of the upper atmosphere on changes in the hmF2 value.     

地球重力场恢复中的位旋转效应

分析了地球自转引起的位旋转效应公式中采用近似速度的影响. 对一组GFZ的快速科学轨道、一组TUM的约化动力法轨道以及一组GFZ的事后科学轨道，计算了星历提供的速度与只有地球引力场对卫星产生作用时的卫星速度的差值，其中参考重力场模型分别采用EGM96、EIGEN2和EIGEN_CG01C. 通过比较得出：轨道数据与EIGEN2地球重力场模型的自恰性优于EGM96和EIGEN_CG01C地球重力场模型. 速度差各分量的变化具有很明显的周期性且与卫星轨道的运行周期相吻合. 当要求在卫星轨迹处获得1m2/s2精度的扰动位时，也即要求位旋转效应公式中卫星速度的近似精度小于2mm/s时，GFZ的快速科学轨道、TUM的约化动力法轨道只需要剔除那些速度精度不满足要求的卫星轨迹点；当要求在卫星轨迹处获得05m2/s2精度的扰动位时，应当重新估算上述轨道的速度信息，或采用精度更高的GFZ事后科学轨道.     

New insights into the spatial variability of the surface water carbon dioxide in varying sea ice conditions in the Arctic Ocean

In the summer of 2005, continuous surface water measurements of fugacity of CO₂ (fCO₂^sw), salinity and temperature were performed onboard the IB Oden along the Northwest Passage from Cape Farwell (South Greenland) to the Chukchi Sea. The aim was to investigate the importance of sea ice and river runoff on the spatial variability of fCO₂ and the sea–air CO₂ fluxes in the Arctic Ocean. Additional data was obtained from measurements of total alkalinity (A_T) by discrete surface water and water column sampling in the Canadian Arctic Archipelago (CAA), on the Mackenzie shelf, and in the Bering Strait. The linear relationship between A_T and salinity was used to evaluate and calculate the relative fractions of sea ice melt water and river runoff along the cruise track. High-frequency fCO₂^sw data showed rapid changes, due to variable sea ice conditions, freshwater addition, physical upwelling and biological processes. The fCO₂^sw varied between 102 and 678 μatm. Under the sea ice in the CAA and the northern Chukchi Sea, fCO₂^sw were largely CO₂ undersaturated of approximately 100 μatm lower than the atmospheric level. This suggested CO₂ uptake by biological production and limited sea–air CO₂ gas exchange due to the ice cover. In open areas, such as the relatively fresh water of the Mackenzie shelf and the Bering Strait, the fCO₂^sw values were close to the atmospheric CO₂ level. Upwelling of saline and relatively warm water at the Cape Bathurst caused a dramatic fCO₂^sw increase of about 100 μatm relative to the values in the CAA. At the southern part of the Chukchi Peninsula we found the highest fCO₂^sw values and the water was CO₂ supersaturated, likely due to upwelling. In the study area, the calculated sea–air CO₂ flux varied between an oceanic CO₂ sink of 140 mmol m⁻² d⁻¹ and an oceanic source of 18 mmol m⁻² d⁻¹. However, in the CAA and the northern Chukchi Sea, the sea ice cover prevented gas exchange, and the CO₂ fluxes were probably negligible at this time of the year. Assuming that the water was exposed to the atmosphere by total melting and gas exchange would be the only process, the CO₂ undersaturated water in the ice-covered areas will not have the time to reach the atmospheric CO₂ value, before the formation of new sea ice. This study highlights the value of using high-frequency measurements to gain increased insight into the variable and complex conditions, encountered on the shelves in the Arctic Ocean.     

Sedimentary geochemistry and provenance of the Lower and Middle Devonian Laojunshan Formation,the North Qilian Orogenic Belt

The Laojunshan Formation is a suite of molasse formed during the rapid uplift of the North Qilian Orogenic Belt (NQOB). Forty-one samples of sandstone have been collected from the Sunan and Minle sections in the western sector and the Gulang and Jingyuan sections in the eastern sector of the NQOB belt. Geochemical analyses of those samples indicated: 1) The MgO+Fe2O3T and Al2O3/SiO2 values are higher, and K2O/Na2O ratios are lower in the western sector than those in the eastern sector. 2) All of them are de...     

The CO2 Discharge in the Boundary Fault Areas of the Sichuan-Yunnan Block and Its Sources

A large number of CO2 springs outcrop along the boundary faults of the Sichuan-Yunnan block and in their neighboring areas.These springs are of a roughly similar distribution as the epicenters of strong earthquakes since 1900.This similarity indicates that the CO2 discharges could be directly related to the modern seismic activity in that area.The evidences of stable carbon and oxygen isotopes indicate that an overwhelming majority of the CO2 released from modern active faults is derived from the deep earth crust.There are 2 main mechanisms of CO2 discharge.Modern active faults are able both to produce directly a lot of CO2 due to thermodynamic metamorphism and to provide passages for the CO2 constituent coming from the lower crust or upper mantle.By continuously monitoring the dynamic changes of CO2 discharges,it would be possible to obtain the information of earthquake precursors that reflect the physical and chemical changes of the earthquake sources.