Middle Holocene Organic Carbon and Biomarker Records from the South Yellow Sea: Relationship to the East Asian Monsoon

The East Asian monsoon system influences the sedimentation and transport of organic matter in East Asian marginal seas that is derived from both terrestrial and marine sources. In this study, we determined organic carbon (OC) isotope values, concentrations of marine biomarkers, and levels of OC and total nitrogen (TN) in core YSC-1 from the central South Yellow Sea (SYS). Our objectives were to trace the sources of OC and variations in palaeoproductivity since the middle Holocene, and their relationships with the East Asian monsoon system. The relative contributions of terrestrial versus marine organic matter in core sediments were estimated using a two-end-member mixing model of OC isotopes. Results show that marine organic matter has been the main sediment constituent since the middle Holocene. The variation of terrestrial organic carbon concentration (OCter) is similar to the EASM history. However, the variation of marine organic carbon concentration (OCmar) is opposite to that of the EASM curve, suggesting OCmar is distinctly influenced by terrestrial material input. Inputs of terrestrial nutrients into the SYS occur in the form of fluvial and aeolian dust, while concentrations of nutrients in surface water are derived mainly from bottom water via the Yellow Sea circulation system, which is controlled by the East Asian winter monsoon (EAWM). Variations in palaeoproductivity represented by marine organic matter and biomarker records are, in general, consistent with the recent EAWM intensity studies, thus, compared with EASM, EAWM may play the main role to control the marine productivity variations in the SYS.     

Linear Analysis of Longshore Currents Instability over Mild Slopes

Longshore current instability is important to nearshore hydrodynamic and sediment transport. This paper investigates the longshore current instability growth model based experimental data with different velocity profiles of slopes 1:100 and 1:40 by adopting a linear shear instability model with the bottom friction effects. The results show that: (1) Only backshear mode exists in the instability of longshore current for slope 1:40 and frontshear and backshear modes may exist slope 1:100. (2) The peaks of linear instability growth mode for slope 1:100 correspond to three cases: the dominant peak is formed by the joint action of both frontshear and backshear, or by backshear alone without the existence of the smaller peak or formed by either the frontshear or backshear. (3) Bottom friction can decrease the corresponding unstable growth rate but it cannot change the unstable fluctuation period. The results of fluctuation period, wavelength and spatial variation obtained by the analysis of linear shear instability are in good agreement with experimental results.     

Review of Rapid Transformation of Floodplain Wetlands in Northeast China: Roles of Human Development and Global Environmental Change

Northeast China is the region with the largest area of wetlands in China. The Sanjiang Plain and the Songnen Plain are large freshwater marsh distribution regions that are affected by climate warming and by the increasing frequency and density of extreme weather and are the regions most subject to disturbances by human activities in Northeast China. The wetlands of the Sanjiang Plain and the Songnen Plain have shrunk severely in the past 60 years, and wetland functions have been reduced substantially because of climate change, unreasonable land use, fire episodes, engineering and construction works and urbanization. Large-scale agricultural development started in the 1950s has been the most important driving factor for wetland loss and degradation in the Sanjiang Plain. Water shortage has been the most important factor for degradation and fragmentation of wetlands in the Songnen Plain. To mitigate wetland degradation and better protect wetlands, special regulations, long-term mechanisms and technical support of wetland protection should be established. A wetland compensation program should be implemented, and technologies for increasing the adaptive capacity of wetlands should be developed. Moreover, it is most important to find the balanced threshold between agricultural development and wetland protection.     

Determination of the absolute32S/34S ratio of IAEA-S-1 reference material and V-CDT sulfur isotope standard

The absolute³²S/³⁴S ratios of IAEA-S-1 reference material and V-CDT standard are determined. For cross-checking, two sets of synthetic isotope mixtures are prepared from high purity³²S and³⁴S-enriched materials in different forms: the first set is prepared from BaSO₄ whereas the second is prepared from Ag₂S. The sulfur isotope analyses are done by using SF₆ method with a MAT-251 EM mass spectrometer. The resulting³²S/³⁴S ratio of IAEAS-1 reference material is 22. 656 4 ±0.006 0, and that of V-CDT is 22.649 6 ± 0.006 0. Project supported by the National Natural Science Foundation of China (Grant No. 86020341).     

岔西地区浊积岩的发现及其油气勘探意义

通过对岔河集西部地区东三段的骨架砂岩分布特征、岩性组合、岩芯观察、粒度分析和地震反射特征等研究,认为储油砂体主要为浊流成因。浊积岩的形成与控凹断层-牛东断裂的发生、发展直至消亡的全过程密切相关。经分析该区东三段存在雄古1岔39、岔76及岔107雄21三个浊积扇,由于后期差异压实作用形成三个对应的鼻状构造,均已获得工业油流,对于油田的增储上产来讲,是进行滚动勘探的有利地区。     

合成淀粉磷酸单酯影响因素的探讨

以木薯淀粉为原料,探讨了应用于造纸行业中具有一定取工的淀粉磷酸单酯合成的最佳工艺条件。     

喀斯特峡谷成因及数学模型研究——以猫跳河、六冲河为例

喀斯特峡谷,是喀斯特地区由河流的侵蚀、溶蚀和崩塌作用共同塑造的一种特殊地貌类型,它的发生与发展,与岩石性质、河床水力比降、流量等各因素密切相关。峡谷的发育和存在,对水利水电建设具有重要意义。本文主要从水文地貌物理场观点出发,分析喀斯特峡谷形态与上述各因素的相关关系,并建立一定的数学模型,为喀斯特峡谷的研究尝试一种新的研究途径      

喀斯特地貌发育的时空演化问题初论

当前对喀斯特地貌发育机理及演化规律的讨论,不仅涉及复杂的学术问题,而且也涉及到认识论问题。喀斯特地貌发育的各种内外因素十分复杂。在地质结构等条件相同的情况下,新构造运动及河流排水基准面,对喀斯特地貌的发育和演化起着重要的控制作用。笔者提出喀斯特地貌发育的“时空演化论”,其主要内涵是:喀斯特地貌发育和演化是在自然界一定的时间和空间领域内进行的,它具有由量变到质变的阶段性,同时又具有空间有序的分带性。喀斯特地貌的时态及形态有一定的演化和配置规律。      

水库岩溶渗漏地质模型和数学模型的初步研究

笔者通过分析研究10座岩溶水库的14条岩溶渗漏量动态曲线(即渗漏量与库水头关系曲线),初步建立了6种岩溶渗漏地质模型和数学模型。      

中国大陆地壳形变GNSS站网简述及数据产品应用现状

自20世纪80年代中期以来,GNSS技术在高精度地壳运动观测与构造形变研究中取得了丰硕的成果,为大地测量、地球动力学研究和防震减灾等诸多领域的业务深化和应用拓展提供了强大的技术支撑。本文在回顾中国大陆地壳形变GNSS站网发展历程的基础上,阐述该网络产出的中国大陆长期构造运动速度场、中国大陆应变率场、位移时间序列、基线时间序列和多边形应变时间序列等几类基础产品,分析这些产品在中国大陆构造运动动态趋势和地震预测分析中的应用情况以及所面临的瓶颈问题,最后展望未来GNSS在高精度地壳运动监测应用中的发展方向。以中国大陆构造环境监测网络为基础,大力推进国内海量GNSS观测数据的共享,提升GNSS多系统融合定位精度,将产出更为精细的科学产品,更好地服务于中国大陆地壳运动和地震预测分析等研究。