华南准静止锋暖区内降水的物理化学特征   总被引：8，自引：0，他引：8  

吴兑  甘春玲  陈位超  游积平 《气象》1994,20(2):18-24

介绍了一次华南准静止暖区内降水的物理化学特征的综合观测分析结果。主要有：①暖区内积云降水雨滴浓度不高，但滴径较大，谱型以多峰谱为主；②雨水ｐＨ值较低，平均４．４３，离子成分中ＮＯ３，Ｃｌ，ＳＯ４，ＮＨ＾＋４，Ｎａ＾＋的浓度较高；③本次降水清除了气溶胶总质量的４５％，对Ｃｌ，Ｆ，ＮＯ３的清除率较高；④由于气溶胶中阴离子被雨水清除的效率较高（主要是ＮＯ３）而阳离子的清除率低，致使雨水ｐＨ值下降，这可能  相似文献   

Reduction of friction on geological faults by weak-phase smearing     

《Journal of Structural Geology》2013

Most common crustal rock types display friction coefficients of 0.6 or higher, but some faults must be frictionally weak as they slip when the stress state is unfavourably-oriented (i.e. the resolved shear stress is low for a given normal stress across the fault surface). A role for low-friction minerals and high pore fluid pressures, either separately or in combination, is frequently invoked to explain such slip, but volume fractions of dispersed weak phases often seem to be present in fault gouge in amounts too small to produce significant mechanical weakening. By means of mechanical tests on synthetic fault gouge and microstructural study of run products, we show that the effective area of an embedded weak phase (graphite) on a slip plane can be substantially increased by mechanical smearing, and that the enlarged area of the weak phase on the slip plane follows a linear mixing law. This allows a relatively small volume fraction of the initially dispersed weak phase to have a disproportionately large effect, provided the smearing is concentrated into a narrow planar slip zone or into an interconnected network of them.  相似文献   

Vulnerability of groundwater resources under climate change in the Pannonian basin     

Mărgărit-Mircea Nistor 《地球空间信息科学学报》2013,16(4):345-358

ABSTRACT

The impact of climate change on groundwater vulnerability has been assessed in the Pannonian basin over 1961–2070. High-resolution climate models, aquifers composition, land cover, and digital elevation model were the main factors which served to perform the spatial analysis using Geographical Information Systems. The analysis reported here is focused on the long-term period, including three temporal time sets: the past period of 1961–1990 (1990s), the present period of 2011–2040 (2020s), and the future period of 2041–2070 (2050s). During the 1990s, the high and very high areas of groundwater vulnerability were identified in all the central, western, eastern, southeastern, and northern sides of the Pannonian basin. In these areas, the water availability is lower and the pollution load index is high, due to the agricultural activities. The low and very low vulnerability class was depicted in the South-West part of the basin and in few locations from the peripheral areas, mainly in the North and West. The medium groundwater vulnerability spreads over the Pannonian basin, but it is more concentrated in the central, South, and South-West. The most affected territory is Hungary, while the territories of Slovenia, Croatia, and Bosnia and Herzegovina are less affected. In the present and future periods, the very high groundwater vulnerability increased in areas by 0.74% and 0.87%, respectively. The low class area decreased between the 1990s and the 2020s by 2.33% and it is expected to decrease up to 2.97% in the 2050s. Based on this analysis and the groundwater vulnerability maps, the Pannonian basin appears more vulnerable to climate change in the present and future. These findings demonstrate that the aquifers from Pannonian basin experience high negative effect under climate conditions. In addition, the land cover contributes to this negative status of groundwater resources. The original maps of groundwater vulnerability represent an instrument for water management planning and for research.  相似文献   

节理控制的降雨入渗通道对黄土开挖边坡稳定性的影响   总被引：1，自引：0，他引：1  

王新刚  余宏明  胡斌  连宝琴 《山地学报》2013,31(4)

黄土节理控制着黄土开挖边坡地表径流的主要入渗通道,在降雨作用下黄土节理将逐步发育成大的入渗通道,加剧了黄土开挖边坡的破坏.通过野外现场地质调查,统计黄土开挖边坡的节理裂隙、入渗贯穿通道分布状况,得出不同开挖边坡高度的入渗通道间距与开挖边坡高度高斯拟合关系式;根据入渗通道分布关系式,概化建立降雨入渗通道的演化数值分析模型,利用岩土工程软件Flac3D模拟分析山西忻州河曲运煤大道黄土开挖边坡在降雨状况下入渗通道发育过程,分析了40mm/d、80mm/d、120mm/d三种降雨工况下降雨24h的入渗通道演化过程及开挖边坡破坏程度,以及降雨对黄土开挖边坡的影响;指出在降雨作用下入渗通道在坡高60m左右破坏严重,坡高高于此高度应注意入渗通道的剧烈扩展并加以防治.借用野外统计、调查结果概化建立入渗通道扩展演化数值模型,可以为工程地质条件相同黄土开挖边坡地区降雨作用下稳定破坏分析以及防治提供一种有效分析方法.  相似文献   

等效渗透原理在岩溶地下水矿坑涌水量计算中的应用     

叶凤珍  宋开本 《南方国土资源》2002,15(4):65-68

文章以德保铝土矿巴头矿段为例 ,在采用分析计算法计算矿体底板有粘性土与下伏灰岩相隔部分的矿坑涌水量时 ,尝试采用等效渗透原理 ,把粘性土底板面积等效为无粘性土相隔的灰岩底板面积计算。以此计算矿坑的涌水量能较好的反映灰岩直接底板与粘性土底板充水的差异性 ,反映粘性土底板厚度以及粘性土底板渗透性能对充水量的影响 ,并能将两种底板混杂分布时的复杂运算简单化 ,较好地解决了矿坑涌水量的计算问题 ,为矿床开采提供科学依据  相似文献   

Laboratory experimental check of a conceptual model for infiltration under complex rainfall patterns     

Florisa Melone  Corrado Corradini  Renato Morbidelli  Carla Saltalippi 《水文研究》2006,20(3):439-452

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Space weathering of silicates simulated by nanosecond pulse UV excimer laser   总被引：1，自引：0，他引：1  

R. Brunetto  F. Romano  S. Fonti  V. Orofino 《Icarus》2006,180(2):546-554

Laser irradiation experiments have been performed on powdered silicates (othopyroxene, clinopyroxene, and olivine) using a nanosecond pulse UV excimer laser (193 and 248 nm) to simulate the effects of space weathering induced on minor bodies of the Solar System by micrometeorite bombardment. We have used different fluences (from 0.05 to 2 J/cm²) to weather the samples, experimenting below and above the ablation threshold. All the irradiated materials have shown reddening and darkening of their UV-vis-NIR reflectance spectra. In addition we have found that: (1) below ablation threshold, weathering effects increase with increasing number of laser pulses, and with increasing fluence, confirming that a thermal process is active; (2) above ablation threshold, weathering is much stronger and efficient than in the previous case, and is independent on the number of pulses. We show that astrophysical time-scales, i.e. times necessary to obtain similar effects on planetary objects, are of about 10⁸ yr for both olivine and pyroxene in the case of ablation. The time grows up to 10¹⁰ yr in the case of thermal effects. We infer that micrometeorite bombardment can be rightly simulated by laser irradiation only considering congruent laser ablation.  相似文献   

Comparing the hydrology of grassed and cultivated catchments in the semi‐arid Canadian prairies     

G. van der Kamp  M. Hayashi  D. Galln 《水文研究》2003,17(3):559-575

At the St Denis National Wildlife Area in the prairie region of southern Saskatchewan, Canada, water levels in wetlands have been monitored since 1968. In 1980 and 1983 a total of about one‐third of the 4 km² area was converted from cultivation to an undisturbed cover of brome grass. A few years after this conversion all the wetlands within the area of grass dried out; they have remained dry since, whereas wetlands in adjacent cultivated lands have held water as before. Field measurements show that introduction of undisturbed grass reduces water input to the wetlands mainly through a combination of efficient snow trapping and enhanced infiltration into frozen soil. In winter, the tall brome grass traps most of the snowfall, whereas in the cultivated fields more wind transport of snow occurs, especially for short stubble and fallow fields. Single‐ring infiltration tests were conducted during snowmelt, while the soil was still frozen, and again in summer. The infiltrability of the frozen soil in the grassland is high enough to absorb most or all of the snowmelt, whereas in the cultivated fields the infiltration into the frozen soil is limited and significant runoff occurs. In summer, the infiltrability increases for the cultivated fields, but the grassland retains a much higher infiltrability than the cultivated land. The development of enhanced infiltrability takes several years after the conversion from cultivation to grass, and is likely due to the gradual development of macropores, such as root holes, desiccation cracks, and animal burrows. Copyright ©2002 Crown in the right of Canada. Published by John Wiley & Sons, Ltd.  相似文献   

济南市东湖水库地质灾害预测          下载免费PDF全文

刘建胜  盛根来  王爱民  刘春萍 《山东国土资源》2004,20(5):48-50,54

济南市东湖水库库区不具备发生崩塌、滑坡、地面塌陷、地面沉降、泥石流、地裂缝、砂土液化的地质环境条件。水库建成使用后，可能出现坝后浸没、次生盐渍化及坝体不均匀沉降等地质灾害，应采取工程措施。  相似文献   

Spectral comparison of heavily hydrated salts with disrupted terrains on Europa   总被引：1，自引：0，他引：1  

J.B. Dalton  O. Prieto-Ballesteros  C.S. Jamieson  R. Quinn 《Icarus》2005,177(2):472-490

Hydrated magnesium sulfate salts have been proposed as major components of the disrupted, reddish terrains on the surface of Europa. This is based on near-infrared reflectance spectra which contain distorted and asymmetric water absorption features typical of moderately hydrated materials such as hexahydrite (MgSO₄⋅6H₂O) and epsomite (MgSO₄⋅7H₂O). Hydrated magnesium sulfates having many waters of hydration could produce improved spectral matches. Here we present cryogenic laboratory spectra of highly hydrated sulfur-bearing salts, including hexahydrite, epsomite, bloedite (Na₂Mg(SO₄)₂⋅4H₂O), mirabilite (Na₂SO₄⋅10H₂O), sodium sulfide nonahydrate (Na₂S⋅9H₂O), supersaturated MgSO₄, NaHCO₃, and Na₂SO₄ brines, and magnesium sulfate dodecahydrate (MgSO₄⋅12H₂O). All have been measured under conditions of pressure and temperature appropriate to the surface environment of Europa. Novel methods for preparation, verification and analysis of MgSO₄⋅12H₂O, which is not stable at standard temperature and pressure (STP), are described. At 100 K, all of these materials exhibit distorted and asymmetric absorption features similar to those in the Europa observations, as well as several weaker, narrow absorptions having widths ranging from 15 to 80 nm. While the agreement with Galileo NIMS observations of dark terrains on Europa is indeed better for highly hydrated salts than for salts of lower hydration states, we conclude that none of these materials alone can account for all of the observed spectral character. As previously suggested, Europa's reddish material appears to be a complex mixture of sulfate hydrates and other materials.  相似文献