Carbon Isotope Stratigraphy of the Cambrian System in the Eastern Tarim Basin, China

The ultra-deep Cambrian System in the Tarim Basin is an important field for petroleum exploration, while fine division of the Cambrian strata remains controversial. In recent years, carbon isotope stratigraphy of the Cambrian System has been established and widely used. Here, we report an integrated profile of carbonate and organic carbon isotopic values (δ13Ccarb and δ13Corg) from cuttings of the Tadong2 Well in the eastern Tarim Basin. Three carbon isotope anomalies of BACE, ROECE and SPICE were recognized on the δ13Ccarb profile. Three apogees and a nadir on the δ13Corg profile and the onset of ROECE on the δ13Ccarb profile were suggested as boundaries of the present four series of the Cambrian System. Suggested boundaries are easily identifiable on the gamma logging profile and is consistent with the previous division scheme, based on biostratigraphic evidence in outcrop sections. Abnormal carbon cycle perturbations and organic carbon burials during the BACE and SPICE events might be related to the reduction and expansion of a huge dissolved organic carbon reservoir in the deep ocean of the ancient Tarim Basin.     

动荷载作用下地下洞室楔形体稳定性分析

通过楔形体破坏的3个基本假定建立了地下洞室楔形体物理模型,提出了楔形体稳定性分析的极限平衡方法。该方法得出了楔形体稳定系数计算表达式,并结合几何分析判断楔形体的稳定状态,进一步探讨了楔形体在爆破施工荷载作用下的楔形体稳定性响应。案例分析表明,楔形体在自重作用下处于稳定状态,施加初始爆破荷载时增加了楔形体的稳定性;工程爆炸作用力远远大于楔形体自重荷载,爆破荷载对楔形体稳定性起主导作用;当爆炸荷载反射时楔形体稳定性显著降低,且沿楔形体①面发生单面滑动破坏。     

Identification of a locking segment in a high-locality landslide in Shidaguan,Southwest China

Natural Hazards - Identification of a locking segment is crucial to assess the potential runout risk and the overall stability of a high-locality landslide. However, it is difficult to...     

灌木植被分布区阻力特性理论及试验研究

为探明河道灌木植被分布区阻水规律，对灌木植被主干、分枝产生的水流阻力特性及其定量特征进行研究。提出原型植被体积修正系数和灌木植被水力半径确定方法，理论推导灌木植被阻力系数计算公式，并结合水槽试验建立植被阻力系数与植被水力半径为特征长度的植被雷诺数之间的关系式。研究结果表明：引入原型植被体积修正系数和灌木植被水力半径使灌木植被阻力计算更为准确；植被阻力系数与植被雷诺数之间呈指数函数关系，随植被雷诺数的增加呈单调减小的趋势，与水槽试验结果吻合很好。     

Seasonal variability and dynamics of coastal sea surface temperature fronts in the East China Sea

Ocean Dynamics - Fronts in coastal oceans are important mesoscale processes that relate to regional dynamics and can impact ecosystems. The daily distribution of a sea surface temperature (SST)...     

内江市景观格局对地质灾害易发性的影响分析

为探讨地表土地景观格局对地质灾害易发性的影响,丰富地质灾害易发性评价体系,以内江市为研究区域,选取高程、坡度、降雨量、植被指数、地层岩性和距构造距离为评价指标,利用层次分析法进行地质灾害易发性评价,以乡镇为统计单元,运用空间滞后模型进行回归分析,定量地探讨了景观格局对地质灾害易发性的影响.结果表明:地质灾害易发性和平均斑块面积、景观蔓延度和香农多样性指数显著正相关.地质灾害易发性与部分景观格局指数存在显著的相关性,景观格局可以在一定程度上反映地质灾害易发性的空间分布,可以在今后的地质灾害评价中将景观格局作为评价指标进行考虑,同时也为实现生态保护和防灾减灾的综合治理提供科学参考.     

一种陆地卫星影像厚云阴影检测方法

针对现有的遥感影像厚云阴影监测方法存在过程复杂、精度不高等问题,该文提出一种TM影像厚云阴影检测方法:通过阈值分割提取影像中的所有阴影;对比一幅近时相的无云影像,分离出厚云的阴影,即云阴影为"有云"影像比"无云"影像多出的阴影;最后将提取结果与人机交互、云阴影增强模型法提取的结果进行对比分析。实验结果表明该方法提取精度较高,可以快速、准确地提取TM影像中的厚云阴影。     

适合共享的面向对象的地理数据模型

讨论了地理信息的特点,提出了一个解决地理信息共享的面向对象的数据模型。     

The optical and molecular signatures of DOM under the eutrophication status in a shallow,semi-enclosed coastal bay in southeast China

We applied stable carbon isotopes, ultraviolet-visible absorption(UV-Vis), fluorescence excitation-emission matrices spectroscopy(EEMs), and Fourier transform ion cyclotron resonance mass spectrometry(FT-ICR-MS) to investigate the chemical composition and sources of the dissolved organic matter(DOM) in both the water column and pore water in Xiangshan Bay, a representative semi-enclosed and eutrophic bay in Zhejiang Province, China. One protein-like fluorescent component(C1) and two humic-like fluorescent components(C2 and C3) were identified by PARAFAC modeling. The concentration of dissolved organic carbon(DOC), the relative intensities of C2, C3, and black carbon-like compounds are all negatively correlated with salinity, indicating that there is a dilution effect of terrestrial signals by seawater in Xiangshan Bay. The differences in light penetration ability of Xiangshan Bay cause different degrees of photo-degradation, which may play an important role in the transformation of organic matter in Xiangshan Bay. The weak correlation between the C1 fluorescent component and salinity indicates that autochthonous sources cannot dominate the protein-like FDOM in the Xiangshan Bay drainage area. Multiple sources(such as anthropogenic inputs and release of pore water) also affect the distribution of the protein-like fluorescent component under eutrophication conditions. The relative proportion of the protein-like fluorescent component in Xiangshan Bay is on a medium level in China and anthropogenic inputs may be a significant source of DOM in coastal bays.     

Advances in Study of Phytolith Carbon Sequestration in Terrestrial Ecosystems of China

Phytolith-Occluded Carbon (PhytOC), a relatively stable carbon fraction, plays an important role in biogeochemical carbon cycle and mitigation of global warming. The formation mechanisms of PhytOC, the influence factors of phytolith carbon sequestration, the advances in study of phytolith carbon sequestration, and the management for enhancing the potential of phytolith carbon sequestration in terrestrial ecosystems of China were summarized in this review. Finally, future researches on phytolith carbon sequestration in terrestrial ecosystems of China were prospected. Climates, vegetation types, soil circumstances, the chemical compositions of the phytoliths and other factors will directly or indirectly affect the potential of phytolith carbon sequestration. In China, the PhytOC production quantity in grassland, cropland, forest, wetland and shrub ecosystems is (0.6±0.1)×10⁶,(4.9±1.7)×10⁶,(1.9±0.4)×10⁶,(0.6±0.5)×10⁶ and (1.3±0.3)×10⁶ t CO₂/a, respectively. Application of silicon-containing fertilizer, cultivation of high-silicon plant, and traditional enhancement of the plant net primary productivity can significantly improve the potential of phytolith carbon sequestration in terrestrial ecosystems of China. Future studies should focus more on ①the mechanisms of phytolith formation in different plants, ②the phytolith carbon sequestration in underground parts of plants from different terrestrial ecosystems, ③the quantification of soil PhytOC in different terrestrial ecosystems. Furthermore, more comprehensive, economical and reasonable management practices of improving the potential of phytolith carbon sequestration should also be further studied in different terrestrial ecosystems.