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111.
本文利用遥感技术通过典型区的分析,对黄土高原土地退化现状及其成因过程进行了深入研究。结果表明,黄土高原地区由于特殊的自然条件,加以长期人类活动影响,土地退化十分严重,并处于不断发展之中,主要表现为水土流失和土地沙化等。 相似文献
112.
钱春林 《云南地理环境研究》1993,5(2):41-45
引滦工程后滦河三角洲水文过程发生很大变化,滦河入海水量骤减河海动力平衡破坏,海洋作用相对增强,滦河口盐度增加,盐水入侵长度增大,三角洲地下水含盐量增高,土壤盐渍化的面积扩大。 相似文献
113.
The local subduction geometry at a site south of Puget Sound in western Washington is investigated using teleseismicP-waveforms recorded on a three-component event triggered seismograph. The data are processed using source equalization deconvolution in order to isolate locally convertedP-to-S arrivals and stacked to improve the signal-to-noise ratio. Stable arrivals in the radial component indicate an oceanic Moho within the subducted slab at a depth of about 53 km beneath the station. Observed amplitude variations with azimuth in the radial data, as well as qualitative aspects of the tangential data, are used to establish a slab dip of 16° to the southeast. Our results are compatible with previous results from a site 60 km to the west, and further confirm a substantial warp in the regional geometry of the subducted Juan de Fuca plate. 相似文献
114.
喀拉通克铜镍硫化矿区二、三号矿床的两个岩体为隐伏的中-基性岩体,受北西向断裂的控制,侵位于石炭统南明水组上段之下部地层中,为岩浆熔离型铜镍硫化矿床。矿物成分以磁黄铁矿、镍黄铁矿、黄铜矿为主。有用元素除铜、镍外,尚伴生有金、银、铂、色、钴、硫可综合利用。它国内外同类型矿床相比,具有成岩、成矿时代新,岩体基性程度低、铜大于镍等特点,因而又具有新的地质找矿意义。 相似文献
115.
在计算反应谱及土层反应时,发现反应谱的形态和大小只受时程的主要部分控制,由此给出主时段的定义和确定主时段的方法。主时段的应用不仅可以大大缩短计算时间,而且能够成为持时的一种有物理意义的度量。 相似文献
116.
SOILSHEARSTRENGTH:ANINDICATORFORERODIBILITYOFTHELOESSSOILSWANGGuiping;WEIZhongpingandZHANGZhiguoAbstract:FieldexperimentSunde... 相似文献
117.
A screening method for heavy metals in aqueous extracts of soil is presented which is based on inhibition of the enzymes urease and alcohol dehydrogenase. The method is suitable to detect cupric and mercury ions in concentrations below 0.01 mg/L and several other heavy metal ions in 1000 fold higher concentration. It is shown that the test may be used for screening of mercury ion concentrations exceeding 0.03 mg/L in aqueous solution when copper chelators are added to the test system. The usefulness of the presented tests to detect heavy metals eluted from soil was verified with samples from ore mining waste. The concentration of copper, lead, and zinc eluted from these samples to different amount was determined by atomic absorption spectrometry and was in good agreement with the enzyme inhibition data obtained with these samples. 相似文献
118.
J. M. Roels 《地球表面变化过程与地形》1985,10(6):587-595
The paper is prompted by apparent deficiencies in the design of plot studies in regional erosion surveys. The principal shortcomings of observational erosion research have been poor sampling design and inadequate analyses of data. The paper identifies various sources of bias which must be taken into account before plot data can be extrapolated to land units in a regional survey. Judging from soil loss data of a case-study in the Ardèche rangelands one may conclude that even accurate plot measurements can still be rather a rough basis for regional erosion assessment. Finally, the paper highlights strategies that might be used to improve erosion sampling. 相似文献
119.
120.
Changes in the rate of soil erosion in lake catchments can be identified from changes in the rate of sediment accumulation in lakes. Here we compare recently afforested sites with non-afforested sites in the Galloway area of Southwest Scotland. We show that lakes with non-afforested catchments have slow, constant sediment accumulation rates, whereas lakes with recently afforested catchments have changes in accumulation that parallel the known history of afforestation. For Loch Grannoch the sediment accumulation rate increases from 0.1 cm yr?1 to over 2 cm yr?2 during the disturbance period. Data from L. Skerrow, however, suggest that the rate might decline to predisturbance levels after approximately 10 years as the forest canopy closes and drainage channels stabilize. 相似文献