Geochemistry of soil gas in the seismic fault zone produced by the Wenchuan Ms 8.0 earthquake, southwestern China   总被引：2，自引：0，他引：2  

Xiaocheng Zhou  Jianguo Du  Zhi Chen  Jianwu Cheng  Yi Tang  Liming Yang  Chao Xie  Yueju Cui  Lei Liu  Li Yi  Panxin Yang  Ying Li 《Geochemical transactions》2010,11(1):1-10

The spatio-temporal variations of soil gas in the seismic fault zone produced by the 12 May 2008 Wenchuan Ms 8.0 earthquake were investigated based on the field measurements of soil gas concentrations after the main shock. Concentrations of He, H₂, CO₂, CH₄, O₂, N₂, Rn, and Hg in soil gas were measured in the field at eight short profiles across the seismic rupture zone in June and December 2008 and July 2009. Soil-gas concentrations of more than 800 sampling sites were obtained. The data showed that the magnitudes of the He and H₂ anomalies of three surveys declined significantly with decreasing strength of the aftershocks with time. The maximum concentrations of He and H₂ (40 and 279.4 ppm, respectively) were found in three replicates at the south part of the rupture zone close to the epicenter. The spatio-temporal variations of CO₂, Rn, and Hg concentrations differed obviously between the north and south parts of the fault zone. The maximum He and H₂ concentrations in Jun 2008 occurred near the parts of the rupture zone where vertical displacements were larger. The anomalies of He, H₂, CO₂, Rn, and Hg concentrations could be related to the variation in the regional stress field and the aftershock activity.  相似文献   

Relationships between carbon isotope evolution and variation of microbes during the Permian–Triassic transition at Meishan Section, South China     

Genming Luo  Junhuang Huang  Shucheng Xie  Paul B. Wignall  Xinyan Tang  Xianyu Huang  Hongfu Yin 《International Journal of Earth Sciences》2010,99(4):775-784

This paper investigates kerogen carbon isotopes, the difference between carbonate and kerogen carbon isotopes (Δ¹³C_carb-kero = δ ¹³C_carb − δ ¹³C_kero) and the difference between carbonate and n-C₁₉ alkane compound-specific carbon isotopes (Δ¹³C_carb-n-C19 = δ ¹³C_carb − δ ¹³C _n-C19) during the Permian–Triassic transition at Meishan, South China. The results show that kerogen carbon isotopes underwent both gradual and sharp shifts in beds 23–25 and 26–29, respectively. The differences between carbonate and organic carbon isotopes, both the Δ¹³C_carb-kero and Δ¹³C_carb-n-C19, which are mainly affected by CO₂-fixing enzyme and pCO₂, oscillated frequently during the Permian–Triassic transition. Both the variations of Δ¹³C_carb-n-C19 and Δ¹³C_carb-kero coupled with the alternation between cyanobacteria and green sulfur bacteria indicated by biomarkers. The episodic low values of Δ¹³C_carb-n-C19 corresponded to episodic blooms of green sulfur bacteria, while the episodic high values of Δ¹³C_carb-n-C19 corresponded to episodic blooms of cyanobacteria. The relationships between the variation of carbon isotopes and biota show that the microbes which flourished after the extinction of macroorganism affected the carbon isotope fractionation greatly. Combining the carbon isotope compositions and the pattern of size variation of the conodont Neogondolella, this paper supposes that anoxia of the photic zone at bed 24 was episodic and it would be caused by the degradation of terrigenous organic matters by sulfate reducing bacteria in the upper water column. Considered together with results from previous research, the high resolution variation of the biogeochemistry presents the sequence of the important geo-events during the Permian–Triassic crisis.  相似文献   

我国近30年龙卷风研究进展   总被引：5，自引：3，他引：2  

郑峰  谢海华 《气象科技》2010,38(3):295-299

从3方面总结了龙卷风研究成果:①研究概况,最初的龙卷风灾后调查到开展天气气候特征分析至近年来开展龙卷风本体结构、产生机制的探讨,获得了丰硕成果;②研究方法提高,从事实调查到利用统计方法,从利用台站常规观测资料到运用卫星、多普勒雷达、风廓线仪等非常规资料开展分析,近年数值模式WRF、ARPS等也被用来研究龙卷风,研究的方法手段不断得到改进;③龙卷风研究、预报面临的困难和未来展望。  相似文献   

Moisture transport from the Atlantic to the Pacific basin and its response to North Atlantic cooling and global warming     

Ingo Richter  Shang-Ping Xie 《Climate Dynamics》2010,35(2-3):551-566

Atmospheric moisture transport from the Atlantic to the Pacific basin plays an important role in regulating North Atlantic salinity and thus the strength of the thermohaline circulation. Potential changes in the strength of this moisture transport are investigated for two different climate-change scenarios: North Atlantic cooling representative of Heinrich events, and increased greenhouse gas (GHG) forcing. The effect of North Atlantic cooling is studied using a coupled regional model with comparatively high resolution that successfully simulates Central American gap winds and other important aspects of the region. Cooler North Atlantic sea surface temperature (SST) in this model leads to a regional decrease of atmospheric moisture but also to an increase in wind speed across Central America via an anomalous pressure gradient. The latter effect dominates, resulting in a 0.13 Sv (1 Sv = 10⁶ m³ s^?1) increase in overall moisture transport to the Pacific basin. In fresh water forcing simulations with four different general circulation models, the wind speed effect is also present but not strong enough to completely offset the effect of moisture decrease except in one model. The influence of GHG forcing is studied using simulations from the Intergovernmental Panel on Climate Change archive. In these simulations atmospheric moisture increases globally, resulting in an increase of moisture transport by 0.25 Sv from the Atlantic to Pacific. Thus, in both scenarios, moisture transport changes act to stabilize the thermohaline circulation. The notion that the Andes effectively block moisture transport from the Atlantic to the Pacific basin is not supported by the simulations and atmospheric reanalyses examined here. This indicates that such a blocking effect does not exist or else that higher resolution is needed to adequately represent the steep orography of the Andes.  相似文献   

Warming and drying trends on the Tibetan Plateau (1971–2005)   总被引：1，自引：0，他引：1  

Hong Xie  Jiansheng Ye  Xiuming Liu  Chongyi E 《Theoretical and Applied Climatology》2010,101(3-4):241-253

Annual and seasonal trends in maximum and minimum temperatures, precipitation and vapour pressure deficit (VPD) were examined with the goal of understanding trends in temperature and moisture across the Tibetan Plateau, using meteorological data (1971–2005) collected at 63 stations. Trends in pan evaporation (PE; 1971–2001, 68 stations) and runoff (1971–2002) in the headwater of the Yellow River were also analysed. Positive trends in maximum and minimum temperatures were observed across the Tibetan Plateau. The highest increases were observed during winter, with results from the majority of stations statistically significant at the 95% level. A decrease trend in diurnal temperature range (DTR) was also observed. Trends in annual and seasonal precipitation and VPD were positive, while the trend in PE was negative. However, the increase in precipitation was not as pronounced as the increase in temperature. Although PE decreased during the time series, actual evaporation probably increased because of the warming across the Tibetan Plateau, where the annual potential water loss measured as PE is three to four times the annual water supply by precipitation. Warming was expected to increase evapotranspiration, causing more water vapour to escape into the atmosphere, thus counteracting or even exceeding the slight increase in precipitation. The increases in annual and seasonal VPD trends indicated a drying tendency and were further substantiated by the observed decrease in runoff in the headwater catchment of the Yellow River. The results provided insight into recent climatic changes across the Tibetan Plateau.  相似文献   

Chemical character of precipitation and related particles and trace gases in the North and South of China     

Mingqun Huo  Qian Sun  Yuhua Bai  Peng Xie  Zhaorong Liu  Jinlong Li  Xuesong Wang  Sihua Lu 《Journal of Atmospheric Chemistry》2010,67(1):29-43

Rainwater samples were collected at four sites, including Beijing and Mazhuang Town in the north of China, Shenzhen and Mangdang Mountain in the south of China. Character of atmospheric particles and gases were also measured at Mazhuang Town and Mangdang Mountain. Both of Beijing and Shenzhen are urban sites; Mazhuang Town and Mangdang Mountain are rural and remote sites respectively. The atmospheric pollution at rural plain site in the north of China was more serious than that at remote mountain site in the south of China. At Beijing, Mazhuang Town, Shenzhen and Mangdang Mountain the average pH values in rainwater were 6.02, 5.97, 4.72 and 4.81, respectively and the concentrations of total ions in rainwater were 1454, 1125, 187 and 191 μeq/l, respectively. While the acidity of the rain was higher in the south than that in the north, the rainwater in the north of China was more severely polluted than that in the south. The major acidic ion in the rainwater is SO₄^2-, and NH₄⁺ is the most important neutralizing ion in rainwater at the four sites, followed by Ca²⁺. The amounts of organic acid in precipitation were compared with other sites in the world. The ratios of organic acid to total free acid in rainwater at Mangdang Mountain was 13.8% and the influence of organic acid on acidity of rainwater at mountain site in the south of China is more important. The variation of atmospheric particles, gases and components in rainwater and cloud-fog water during special rain and cloud-fog events was discussed. The importance of washout process varied with atmospheric species. The impacts of rainfall, rain duration time and wind speed on wash-out process were estimated by regression analysis.  相似文献   

A study on one‐dimensional consolidation of layered structured soils          下载免费PDF全文

Kang‐He Xie  Chang‐Qing Xia  Ran An  Hong‐Wei Ying  Hao Wu 《国际地质力学数值与分析法杂志》2016,40(7):1081-1098

The governing equations for one‐dimensional consolidation of layered structured soils under time‐dependent loading are established. Using simplified k‐σ′ and m_v‐σ′ models, n‐layered structured soils are transformed into (n + 1) or (n + 2)‐layered soils in which the thickness of upper and lower layers are gradually changing. The approximate solutions for the governing equations are then obtained under two types of boundary conditions, and the computer program is developed. Based on the solutions and computer program, the consolidation behavior of layered structured soils with soft interlayer is studied. It is shown that the permeability and compressibility of the soft interlayer have the greatest influences on the rate of settlement and rate of the dissipation of excess pore water pressure. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

A range-dependent echo-association algorithm and its application insplit-beam sonar tracking of migratory salmon in the Fraser Riverwatershed     

Xie  Y. 《Oceanic Engineering, IEEE Journal of》2000,25(3):387-398

Fish sonars have long been used to survey and monitor migratory salmon in rivers and at sea. However, research has been lacking in the development of algorithms to extract fish tracks from data collected in a riverine or oceanic environment. Current fish trackers, based on a pulse-to-pulse tracking method, only work well under ideal conditions when targets are well separated and the signal-to-noise ratio is high. Fisheries biologists often have to identify fish traces visually from raw echograms. This approach is both labor-intensive and time-consuming, limiting the usefulness of hydroacoustic techniques for fisheries management. This paper presents a fish-tracking algorithm which sorts randomly distributed echoes into coherent fish traces. Fish counts obtained with the algorithm compare well with visual counts at two quite different sites in the Fraser River watershed. The key features of the algorithm are: (1) the linking mechanisms among sequential fish echoes are range-dependent; (2) the growth echo for a developing track depends not only on its space-time relation with the previous track echo (the pulse-to-pulse statistics) but also on its relation to the entire track being constructed; (3) there are a total of only five echo-association criteria in the algorithm; (4) the simplicity of the algorithm structure provides a convenient platform for implementing specific and sophisticated tracking criteria to meet specific needs; and (5) the user can fully control the performance of the algorithm by choosing values for the 11 well-defined tracking parameters  相似文献   

超压释放及其对油气运移和聚集的意义   总被引：22，自引：5，他引：22  

刘晓峰  解习农 《地质科技情报》2001,20(4):51-56

从增压作用和减压作用相互关系的角度，探讨了超压释放的定义－超压趋向于静水压力降低的作用，根据超压释放的结果，超压释放可分为不完全释压和完全释压，依突破压力封闭的动力，超压释放可分为主动释压和被动释压。有两类不同的成因的超压释放通道，分别是自振通道和它拓普通，超压释放的主要机制有断裂活动，水力压裂，底辟作用，渗透性岩层输导作用，渗透作用，剥蚀作用和人为作用。超压释放提供了油气运移的现实动力，开拓了油气运移的通道，促进了生烃作用，有利于超压系统内的油气成藏，影响油气的分布。超压释放分析为探讨超压与油气的运聚提供了有效的方法。  相似文献   

Changes in lead concentration in Antarctic penguin droppings during the past 3,000 years     

Liguang Sun  Zhonqing Xie 《Environmental Geology》2001,40(10):1205-1208

Anthropogenic lead (Pb) has been found in Antarctic seawater, surface snow and ice-cores. Here, we analyzed a 3,000-year record of lead concentration in lake sediments affected by penguin droppings. We found that lead concentration in penguin droppings has significantly increased during the last 200 years, especially in the last 50 years, as compared to low and stable lead levels prior to the Industrial Revolution. This clearly indicates that global environmental pollution has influenced the Antarctic ecological system. Heavy metal (Pb) may find its way into the food web, bioaccumulate, and be passed along the chain to penguins.  相似文献