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991.
土壤由岩石风化而来,岩石—土壤是一个密切联系的体系,是地球系统科学中与人类关系最为密切的一部分。为调查研究地质建造单元岩石—土壤体系(简称:岩土体系)中的物质组成演化特征,我们必须选择原地风化的残积物出露区域来完成土壤垂向剖面采样。本文以海南岛区域生态地质背景调查项目的资料数据为基础,科学阐述了残积物剖面的确定方法,并依据琼北玄武岩垂向剖面地球化学数据,总结出如下结论:垂向剖面SiO2含量呈现出土壤表层A层和岩石的高,土壤B、C层含量低的“凹”字型特征,与Al2O3含量变化趋势相反(“凸”字型),两个代表性组分存在明显的负相关性,其他组分根据其亲和性,与该两种组分协同变化,部分受表层活动影响较大的元素,例如有机质、I等部分微量元素,则不具有该规律,土壤表层(A、B层)与深层(C层)、岩石中差别通常较大。 相似文献
992.
Eco-environmental problems and effective utilization of water resources in the Kashi Plain, western Terim Basin, China 总被引:4,自引:0,他引:4
Since ancient times, water resources, mainly from melting snow in the high mountains, have nourished a large area of an oasis
in the Kashi Plain in the western Terim Basin, China. In the last half-century, however, the rapid growth of population and
the overexploitation of water, soil, and biological resources have led to drought, salinization, and desertification in the
area, and consequently have hindered the development of sustainable agriculture. In this study, groundwater reservoirs with
sustainable water supplies equivalent to 44.65×108 m3/year were identified, which has made it possible to implement several projects in the area to improve the ecological and
agricultural environment. Three strategies are proposed for the integrated development and management of both surface-water
and groundwater resources in the area.
Electronic Publication 相似文献
993.
An upswing in haze weather during autumn and winter has been observed over North and Northeast China in recent years, imposing adverse impacts upon local socioeconomic development and human health. However, such an increase in the occurrence of haze events and its association with natural climate variability and climate change are not well understood. To investigate the climatology of the meteorological factors associated with haze events and their natural variability, this study uses a meteorological pollution index called PLAM (Parameter Linking Air-quality to Meteorological conditions) and ERA-Interim reanalysis data. The results suggest that high PLAM values tend to occur over southern parts of northern China, implying the weather conditions over this area are favorable for the occurrence of haze weather. For the period 1979–2014, the regional mean PLAM shows an overall increase across Beijing, Tianjin, and Hebei Province, and parts of Shanxi Province. Also, a periodicity of 28–34 months is found in the temporal variation of PLAM, which implies a potential association of PLAM with the stratospheric Quasi-Biannual Oscillation (QBO). By using the QBO index during the autumn and winter seasons in the preceding year, an increase in PLAM is found for the westerly phases of the QBO, relative to the easterly phases. An upper-tropospheric warming is also found in the westerly phases, which can induce a stable stratification that favors the increase in PLAM across the midlatitudes. The modulations of large-scale environmental factors, including moist static stability, vertical velocity, and temperature advection, also act to enhance PLAM in the westerly phases. However, the baroclinic term of moist potential vorticity at 700 hPa tends to decrease over the south, and an increase in low-level ascent is found over the north. These factors can reduce PLAM and possibly limit the statistical significance of the increased PLAM in the westerly phases of the QBO. 相似文献
994.
冬小麦生长发育的模拟模式 总被引:3,自引:0,他引:3
根据冬小麦生长发育及其与环境条件关系的机理研究,建立了模拟冬小麦发育阶段和各器官生物量变化的动态模式。其中包括3个环境要素子模式,分别计算温度、辐射和水分,5个生物学过程子模式,分别模拟冬小麦的发育、光合、呼吸、同化物分配和叶面积系数。用镇江和海安共8个播期的实测资料对模式进行验证,并对模式进行了初步数值试验应用。 相似文献
995.
996.
997.
Some annual variation characteristics for the Northern Hemispheric monthly mean precipitation fields 总被引:2,自引:0,他引:2
Tang Maocang 《大气科学进展》1989,6(2):186-201
By the utilization of monthly precipitation data from all stations in the Northern Hemisphere annexed to the “World Survey of climatology, Vol. 1-15, the distributions of the maximum precipitation months (MPM), the annual relative precipitation (ARP) and the monthly relative precipitation (percent of annual) in January and July are respectively mapped. Moreover the distributions of intermonthly relative precipitation variabilities from January to December are plotted as well. From these figures, the precipitation in the Northern Hemisphere may be classified into three types (continental, oceanic and transitional types) and 17 regions. The precipitation regime may also be divided into two patterns, the global and regional patterns. The global pattern consists of planetary front system and ITCZ and its inter-monthly variation shows the north-and-south shift of the rain belt; the regional pattern consists of the sea-land monsoon and plateau monsoon regime, in which the inter-monthly variation of rain belt shows a east- and-west shift. 相似文献
998.
河流下切带动区域地貌的演化,因此河流下切速率及其时空分布样式是解析构造、地表过程和气候变化之间广泛相互作用的关键切入点之一。根据阶地的保存状况,利用河流阶地的累积下切量和下切时间可以直接测得千年到百万年时间尺度的下切速率。鉴于此河流下切速率是链接不同时间和空间尺度上地貌侵蚀速率的关键所在,并具有较精细的时空分辨率。计算河流下切速率时,累积下切量上限是阶地基座的拔河高度,下界最优选择是低级阶地基座,而累积下切时间的最佳约束是尽量靠近阶地基座的冲洪积物的沉积时间;运用河流下切速率获得岩石抬升速率和区域构造变形量时,通常假定区域地貌处于均衡状态,河流下切速率代表着岩石抬升速率。但是由于气候变化,河流下切过程具有较强的时空不稳定性,导致这些假设经常失效。此外,河流加积和下切的转换与第四纪冰期-间冰期的变化并不一定存在时间上的一一对应关系,这可能是由于河流裂点的溯源迁移以及河流对气候变化的响应方式与强度存在差异。因此,实际工作中需要多方面获得不同时空尺度和分辨率的构造变形、气候变化以及地表过程的基本信息,借助地貌数值模拟程序,定量解析构造、气候和地表过程之间的广泛而复杂的相互作用。
相似文献1000.