Soil degradation: a global problem endangering sustainable development

Soil degradation, defined as lowering and losing of soil functions, is becoming more and more serious worldwide in recent decades, and poses a threat to agricultural production and terrestrial ecosystem. It is estimated that nearly 2 billion ha of soil resources in the world have been degraded, namely approximately 22% of the total cropland, pasture, forest, and woodland. Globally, soil erosion, chemical deterioration and physical degradation are the important parts amongst various types of soil degradation. As a natural process, soil degradation can be enhanced or dampened by a variety of human activities such as inappropriate agricultural management, overgrazing, deforestation, etc. Degraded soil means less food. As a result of soil degradation, it is estimated that about 11.9-13.4% of the global agricultural supply has been lost in the past five decades. Besides, soil degradation is also associated with off-site problems of sedimentation, climate change, watershed functions, and changes in natural habitats leading to loss of genetic stock and biodiversity. Therefore, it is essential to combat soil degradation at different levels and scales worldwide, not only for food security and ecological health, but also for the guarantee of global sustainable development.     

从本土到全球网络化的人地关系思维范式转型

早期地理学关于人地关系的研究多基于本土思维,秉持“一方水土养育一方人”的理念。在严重依赖自然资源的传统农业社会,这一理念及其指导下的区域地理研究和区域管理实践,对于促进人与自然的协调发展起到积极作用。随着系统开放程度的增加,规模不等、层级不同的地域系统形成了一个相互依赖、相互耦合的地理网络。每个地域都是这个网络上的节点,地域问题的产生与解决与网络上其他节点有密切关联、与地域系统内外因素紧密相关,地域外因素有时甚至起主导作用。虚拟水、生态足迹、贸易隐含碳排放、资源纽带关系及人地关系远程耦合等概念和方法的提出,标志着人地关系研究范式从本土思维向全球网络化思维转型。依照新的理念和研究范式,传统的本土思维范式及建立在此范式上的相关研究主题（如区域承载力）应该受到重新审视。     

湖南水口山铅锌金银矿床地球化学特征

根据湘南区域地球化学特征,结合水口山矿区地质矿床特征,分别从地层、岩性,构造类型及热岩系的微量元素地球化学特征,对两大不同成岩、成矿系列中不同微量元素组合可引起的原、次生晕异常特征作了较为深入研究、讨论。     

基于生态适宜性评价的西南丘陵区土地整治工程布局研究

如何科学合理地识别土地整治工程的生态适宜性,是评判当前土地整治工程是否实现“有利生产,方便生活,兼顾生态”目标的重要依据,更是土地整治理论与规划亟待解决的重要命题。选取川东平行岭谷区的垫江县为研究区,立足146个土地整治项目,借助生态位思想进行土地整治工程生态适宜性评价,计算土地生态整治工程布局潜力指数,对土地整治工程生态化布局进行定向。结果表明：① 土地整治工程生态适宜性指标影响显示出显著异质性,其中耕地连片度、坡度、灌溉保证率是开展土地整治工程生态适宜性评价的首选因素。② 土地整治项目中单项工程的生态适宜性水平差异较大,其中土地平整和灌排系统的生态适宜性低于临界水平,田间道路和生态景观工程的生态适宜性高于临界水平。③ 土地整治项目整体工程的生态适宜性程度差异显著,各项目土地整治工程生态适宜性均值为0.72,处于生态适性的临界水平。适宜等涉及土地整治面积7434 hm²,占9%。临界适宜等涉及土地整治面积54530 hm²,占67%。不适宜等涉及土地整治面积18845 hm²,占24%。④ 研究区土地整治工程生态适宜性布局整体呈多样化格局,Ⅰ等潜力区主要位于研究区中西部,布局方向为发展多功能农业,应注意如何保证其经济价值实现的同时不损害其生态价值。Ⅱ等潜力区分布范围较广,布局方向为发展大宗粮油产业,应思考在保证其粮食生产的同时尽量避免对农田生态系统的破坏。Ⅲ等潜力区主要位于鹤大台地区,布局方向为发展生态立体农业,应强调如何在保证生态环境不受破坏的前提下发展具有山区特色的生态农业。     

怒江小流域土地利用变化及人文驱动力分析--以茶山小流域为例

通过实地调查和两期土地利用现状数据对比以及对农户的访谈,分析研究怒江茶山小流域土地利用现状及时空变化特征,从人文地理视角研究人地关系地域系统,分析导致土地利用变化的驱动力,为确立可持续发展背景下土地利用优化模式及产业结构的优化提供重要前提和科学依据。     

THE FINE CRUSTAL STRUCTURE OF THE SOUTHERN MARGIN OF NORTH CHINA BLOCK REVEALED BY DEEP SEISMIC REFLECTION PROFILE

The study area is located at the junction of the northern margin of the Qinling orogenic belt and the southern margin of the North China Block. In order to study the fine crustal structure and the deep-shallow structural features of faults in this area, we conducted deep seismic reflection profiling with the seismic profile of 100km long, directing NE-SW in Zhumadian City, Henan Province, and got clear lithospheric structure images along the profile. As regards the data acquisition, we applied the geometry of 25m group interval, 1000 recording channels and more than 60 folds. Seismic wave exploding applies the 30kg shots of dynamite source with the borehole depth of 25m. The shot interval is 200m. In data processing, we focused on improving the signal-to-noise ratio. Data processing methods mainly include first break removal, tomographic static correction, abnormal amplitude elimination, amplitude compensation, pre-stack denoising, surface consistent deconvolution, velocity analysis, several iterations of the residual static correction, dip moveout, post-stack time migration and post-stack denoising, etc. The profile with high signal-to-noise ratio was obtained. The reflection wave group characteristics is obvious in the crust, which reflects abundant information about geological structure. Along the profile, the crust is characterized by double-layer reflection structure, and the Moho surface is composed of a series of laminated arc-shaped strong reflections. The thickness of the upper crust is about 14.8~20.7km, and the total thickness of the crust is about 32.0~35.1km. The upper crust is dominated by the inclined, densely stratified or arc-shaped reflections. The lower crust is dominated by arc-shaped and inclined reflection, and there is a reflective transparent zone under the Moho surface. The reflection sequences with different directions and shapes in the upper crust constitute the nappe structure in southwest segment and the structural model of two concaves with one uplift in NE segment, which correspond to the north Qinling nappe, Zhumadian-Huaibin depression, Pingyu-Xiping uplift and a secondary depression, respectively. There are abundant arc-shaped reflection sequences in the lower crust, which may represent multi-stage magmatic activities. The deep seismic reflection profile shows that faults in the upper crust are well developed. According to the characteristics of reflected wave field in the profile, four groups of fault structure which contain ten faults with different scales are interpreted. Among them, faults F_P1, F_P2 and F_P3 constitute the thrust fault system in the northern margin of Qinling Mountains, and F_P5 and F_P7 are boundary faults of Zhumadian-Huaibin depression. These faults are all developed within the upper crust. In addition, the Fault F_PM is a large fault that cuts through the lower crust and Moho surface. The deep seismic reflection profile reveals the crustal structure and deep-shallow structural features of faults at the junction of the northern margin of the Qinling orogenic belt and the southern margin of the North China block, which provides seismological evidence for the analysis of structural differences, the deep earth's interior processes and deep-shallow structural relationships between the Qinling-Dabie orogenic belt and the southern margin of the North China block. The lower crust of the study area is divided into two parts by deep faults that dislocate the Moho surface. These two parts have distinct reflective structures, suggesting that the area has experienced intense complex tectonic movements. The faults in the upper crust control the formation of basin-mountain structure and stratigraphic deposition of this area. And deep faults in the crust that disrupt Moho surface create conditions for the upwelling and energy exchange of deep materials. All of these have regulated the composition of material and the distribution of energy in the crust. The deep faults cutting through the lower crust and Moho surface and the south-dipping arc-shaped and inclined strong reflection sequences developed in the lower crust should indicate the large-scale subduction of the southern margin of the North China block towards the south-trending Qinling orogenic belt.     

定量风险评估在导管架海上安装工程中的应用

定量风险评估是风险评估发展的主要趋势。论文基于TOPS IS和神经网络响应面法,提出一种定量风险分析方法,并运用此方法对导管架海上安装过程进行深入分析,以及时查找并消除各方面的事故隐患。首先找出潜在的风险事件及相关风险因素,然后对风险事件的模糊概率和损失程度后果进行量化,最后依据风险评价结果对需要控制的风险事件给出控制措施。实例表明,该方法是一种实用而有效的定量风险评估方法。     

含有腐蚀缺陷海底管道极限载荷分析

利用有限元弹塑性分析方法,对含有腐蚀缺陷的海底管道进行材料非线性和几何非线性分析,探讨了确定管道极限载荷的准则。在此基础上,给出含有腐蚀缺陷的海底管道的极限载荷,研究腐蚀长度、深度和宽度对海底管道极限载荷的影响,提出了含有腐蚀缺陷的受内压的海底管道的极限载荷计算公式,并与试验结果进行了比较,证明该方法是有效的。     

基于长基线系统深海采矿ROV精确定位

对于深海采矿集矿机ROV的定位,采用传统的长基线水声定位系统通常存在较大误差。对此提出了一种新的算法模型,首先通过比较集矿机测量位置与前一次修正位置的几何关系,对当前集矿机的位置进行修正,然后利用新的集矿机位置修正声速的数值,并得出重新修正后的集矿机测量位置。这样反复的多重迭代使得在某一时刻集矿机ROV的测量位置逐步趋近其理想位置,实现长基线系统的水声精确的三维立体定位。通过数值仿真分析,结果显示与传统的长基线水声定位方法相比,通过该方法获得的集矿机行驶轨迹能更好地趋近其理想行驶曲线,表明该算法的有效性。