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991.
A comparative study of nutrient transfer via surface runoff from two small agricultural catchments in north China 总被引:1,自引:0,他引:1
A field study was conducted to determine the effect of landscape spatial pattern and micro-topography on nutrient transfer
via runoff from two catchments into Yuqiao Reservoir in north China. The surface runoff discharge was measured during rainfall
events and water samples were analyzed in 2004 and 2005. The mean annual total nitrogen (TN) and total phosphorus (TP) exports
per unit area from Caogezhuang catchment (C catchment) were 1.048 and 0.561 kg ha−1 year−1, respectively, while the TN and TP exports from Taohuasi catchment (T catchment) were 0.158 and 0.027 kg ha−1 year−1. In both catchments, village and vineyard shared the highest nutrient export ability due to the accumulated animal waste
and heavy application of fertilizer and manure. In T catchment, the distance of village and vineyard was about 1,500 m away
from the receiving water and in between were woodland and cropland. In the hydrological pathway, there were sink landscape
structures of small stone dams, roadside swale, vegetated filter strip and dry ponds, which could detain water and nutrients.
In C catchment, the distance between the village and the receiving water was about 200 m, and the hydrological pathway was
compacted roads and ditches with no sink structures. It is suggested that the distance between the pollution source area and
the receiving water and the micro-topographical features were the main factors to control the great difference in nutrient
export rates. 相似文献
992.
Assessing pollutions of soil and plant by municipal waste dump 总被引:1,自引:0,他引:1
Changli Liu Yun Zhang Feng’e Zhang Sheng Zhang Miying Yin Hao Ye Hongbing Hou Hua Dong Ming Zhang Jianmei Jiang Lixin Pei 《Environmental Geology》2007,52(4):641-651
Research is few in the literature regarding the investigation and assessment of pollutions of soil and plant by municipal
waste dumps. Based upon previous work in seven waste dumping sites (nonsanitary landfills) in Beijing, Shanghai and Shijiazhuang,
this study expounds the investigation and assessment method and report major pollutants. Using relative background values,
this study assesses soil pollution degree in the seven dumping sites. Preliminary conclusions are: (1) pollution degrees are
moderate or heavy; (2) pollution distance by domestic waste that is dumped on a plane ground is 85 m; (3) the horizontal transport
distance of pollutants might be up to 120 m if waste leachates are directly connected with water in saturated soils; (4) vertical
transport depth is about 3 m in unsaturated silty clayey soils. Furthermore, using relative background values and hygiene
standards of food and vegetable this study assesses the pollutions of different parts of reed, sorghum, watermelon and sweet-melon.
It is found: (1) in comparison with the relative background values in a large distance to the waste dumping sites, domestic
wastes have polluted the roots and stems of reed and sorghum, whereas fine coal ash has polluted the leaves, rattans and fruits
of watermelon and sweet-melon; (2) domestic wastes and fine coal ash have heavily polluted the edible parts of sorghum, water
melon and sweet-melon. As, Hg, Pb and F have far exceeded standard values, e.g., Hg has exceeded the standard value by up
to 650–1,700 times and Cd by 120–275 times, and the comprehensive pollution index is up to 192.9–369.7; (3) the polluted sorghum,
watermelon and sweet-melon are inedible. 相似文献
993.
本文探讨了GPS RTK定位技术在大面积1:1000航测成图高程测量方案中的实施,对布网方案进行了研究与探讨,并对GPS RTK用于高程测量的精度进行了分析,对其应用前景作出评价。 相似文献
994.
Coseismic water level oscillation and correlated deep water temperature changes have been observed in a water well at Tangshan City by high sensitivity measurement. Amount of water temperature changes depend on ampli-tude of water level oscillation. Coseismic water temperatures always decrease as water level oscillates, drop of temperature ranges from 0.001 °C to 0.01 °C corresponding to amplitude of water level oscillation from several centimeters to about one meter. Temperatures usually recover one to several hours after the oscillation. We suggest that the temperature drop is produced by dispersive transfer of heat as the water oscillates, and follow-up thermal conduction makes temperature recovery. Our finite element calculations support quantitatively the idea. High ac-curacy measurements of water temperature at different depths in the future may test our interpretation. 相似文献
995.
Optical dating of Holocene sand dune activities in the Horqin sand-fields in inner Mongolia, China, using the SAR protocol 总被引:4,自引:0,他引:4
The Horqin sand-field in northeastern Inner Mongolia, China, had been the fertile grassland in North China, but desertification and sand-dust storm have increasingly occurred in the past decades [Zhu and Wang, 1992. Theory and practice of sandy desertification in China (in Chinese with English abstract). Quaternary Sciences 2, 97]. To understand the Holocene sand dune activities in this region, five sand dune profiles were investigated, and 32 coarse grain quartz samples were dated by OSL using the single-aliquot regenerative-dose (SAR) protocol [Murray and Wintle, 2000. Luminescence dating of quartz using an improved single-aliquot regenerative-dose protocol. Radiation Measurements 32, 57–73]. For cross-checking, six organic-rich samples from the paleosols and sandy peat/mud were dated by both 14C and quartz OSL. With one exception, 14C and quartz OSL dating results show good agreements. Based on the consistent results of five sand dune profiles, a chronology of Holocene dune activity in Horqin sand-field is established as follows: (i) active sand dunes built up widely before 10 ka; (ii) dunes semi-stabilized between 10 and 7.5 ka ago; (iii) the dunes solidify and chernozem soils developed between 7.5 and 2.0 ka ago; and (iv) partially re-mobilization of dunes occurred since about 2.0 ka ago. 相似文献
996.
在缺乏其他资料的情况下,地脉动常常用做确定地震动对地表介质产生影响效应的简便手段。本文以银川市区为研究对象,根据地震勘探资料有目的的选取5条测线在银川市区进行地脉动观测,观测点共141个。用Nakamura提出的HV谱比法解析观测数据,在给定地下构造剪切波速度(VS)的基础上,由H/V比值曲线中的基本频率推测盆地深层地下构造。通过理论计算进一步验证了解析结果。结合前人地震勘探资料推测了银川市区脉动基本频率分布特征,并给出2D和3D银川市基底构造变化情况,对比分析表明,HV谱比法得到的脉动基本频率值可以反映银川盆地基底变化情况。 相似文献
997.
Yin‐Nan Huang Andrew S. Whittaker Michael C. Constantinou Sanjeev Malushte 《地震工程与结构动力学》2007,36(12):1741-1761
Numerical models of a sample nuclear power plant (NPP) reactor building, both conventionally constructed and equipped with seismic protective systems, are analysed for both safe shutdown and beyond‐design‐basis earthquake shaking at two coastal sites in the United States. Seismic demands on secondary systems are established for the conventional and seismically isolated NPPs. The reductions in secondary‐system acceleration and deformation demands afforded by the isolation systems are identified. Performance spaces are introduced as an alternate method for evaluating demands on secondary systems. The results show that isolation systems greatly reduce both the median and dispersion of seismic demands on secondary systems in NPPs. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
998.
Hurricanes produce mixing and flow divergences (and convergences) that alter the upper-ocean heat content (OHC), which in turn affects the storm. Ocean observations under a hurricane are rare, making it difficult to validate forecast models. Past research have mainly focused on OHC-changes by vertical mixing and tacitly assumed that horizontal transports are slowly varying. Moreover, effects of coastal boundaries on ocean responses to hurricanes are generally omitted. This work uses satellite data to detect and verify forecast isopycnal motions under hurricane Wilma (Oct/16–26/2005) in the Caribbean Sea and the Gulf of Mexico. The model is then used to show that Wilma-induced convergences in northwestern Caribbean Sea produce increased Yucatan-Channel transport into the Gulf ahead of the storm, and the Yucatan–Loop Current front diverts most of this heat around the Loop. This response is distinct from that of an ocean without the Loop, for which warming is widespread north of the channel. These intricate ocean responses can impact hurricane predictions. 相似文献
999.
采用1956-2006年漯河市观测站资料,运用一元回归分析漯河市降水的气候变化特征,讨论了3类降水云系与降水量的关系,为科学实施人工增雨(雪)作业和提高天气预报水平提供参考。 相似文献
1000.