UPLAND EROSION MODELING WITH CASC2D-SED

1 INTRODUCTION Erosion and sedimentation embody the processes of detachment, transport, and deposition of soil particles. Erosion and subsequent deposition can cause major problems. Erosion reduces productivity of cropland, sediment degrades water quality and may carry soil adsorbed polluting chemicals. Deposition in irrigation canals, stream channels and reservoirs reduces structural capacity and requires costly removal. Ideally, an erosion model should describe the physical processes…     

新丰江水库消涨带岸坡侵蚀研究

水库消涨带是随水库水位涨落不时出没的库岸，坡面裸露，泥沙侵蚀强度大，生态环境恶劣。本研究采用野外点定观测方法，研究了新丰江水另消涨带花岗风化泥沙侵蚀机理，实测各类坡面的侵蚀模数，估算了总侵蚀量，并把塌岸与陆上花岗岩石风化壳的崩岗和滑坡发生机理作比较。     

Einflußfaktoren auf die Freisetzung von DOC und AOX unter ehemaligen Abwasserversickerungsflächen

Factors Influencing the Release of DOC and AOX out of Former Wastewater Infiltration Soils The influence of soil and of infiltration water quality on the release of dissolved organic carbon (DOC) and adsorbable organic halogens (AOX) from two former wastewater infiltration sites was investigated in laboratory column studies. Desorption was the most important factor influencing release processes. It depends on the amount of sorbent and sorbate and the strength of binding. Therefore, for constant irrigation rates a higher soil organic carbon content coincided with higher DOC-contents of the column effluent, while the irrigation water quality was of minor importance. Within one system the dependencies of AOX release and DOC mobilization were found to be similar. Transferring these dependencies on other systems has its limitations because of a different binding quality between sorbent and sorbate.     

Parameters determination for a linearly inhomogeneous half-space using characteristics of the time-harmonic surface waves

The paper presents a study of time-harmonic surface waves in a linearly inhomogeneous half-space. The study is based on the solution of that problem for an arbitrary (from 0 to 1/2) value of Poisson's ratio. Vertical vibrations due to a vertical harmonic force, which at large distances from the force represent Rayleigh-type waves, and transverse horizontal vibrations due to a horizontal force, which at large distances form waves of Love's type, are considered in detail. Material damping is taken into consideration. Inhomogeneity significantly affects relationships connecting wave characteristics and the frequency of vibration, and it is shown in the paper how this fact can be used for determining material properties (surface shear modulus, degree of inhomogeneity, damping ratio) with the help of experimental results concerning wave propagation over the surface of the half-space. It is shown that for forced waves the relationship between the wave phase angle and distance can significantly differ from a straight line, i.e. the wave number varies with distance. Therefore, it is desirable to relate experimental and theoretical results to such parts of wave propagation line, which correspond to same phase angle intervals. Copyright © 2000 John Wiley & Sons, Ltd.     

Suspended sediment in rapid subsurface stormflow on a large field plot

The occurrence of rapid movement of suspended sediment in subsurface stormflow on a large field plot in California is described. Concentrations of over 1000mgl^?1 were recorded in storms of only low to moderate intensity. The observed sediment was composed of uniformly fine-sized particles 4 to 8 μm in diameter. The mode of transport seems different from processes previously reported. Differences in sediment concentrations in different events, levels of ¹³⁷Cs on the sediment, and several other types of evidence indicate that the sediment was detached and entrained at the ground surface by raindrop impact and that the water and sediment flow occurred mainly through macropores in the soil. As conditions similar to those at the study site are not uncommon, it seems probable that the phenomenon may occur in many regions.     

土壤水溶性有机物吸着系数及其影响因素研究

测定了中国中、东部地区17种土类45个表土样品中水溶性有机物的吸着系数、分子量分布、腐殖酸含量、粘土含量以及土壤pH值，分析了水溶性有机物吸着系数的分布、地域分异和影响吸着系数的主要因素。结果表明，中国中、东部主要天然土壤类型A层水溶性有机物吸着系数在0．0014－0．0284L/g，中位数为0．0062L/g；研究区吸着系数具有自北向南和自西向东递降的一般趋势。水热的地域分异是影响土壤A层Ks地域分异的根本因素，pH和WSOC分子量分布是直接影响Ks值的两个重要因素。     

小兴安岭针叶凋落物的分解与土壤动物的作用

应用不同网孔分解样袋、排除不同类型土壤动物的作用的方法,对比研究土壤动物对针对凋落物的分解作用,结果表明,在各类土壤动物作用下的大孔网袋样品的分解速度明显快于只有中小型土壤动物作用的中孔网的分解样品,快于尽量排除土壤动物作用条件下的小孔网袋的分解洋;凋落物分解过程中,凋落物失重量与土壤动物个体数量之间的相关性不明显,土壤动物对质地较软的凋落物作用程度较质地较硬的凋落物高;土壤动物的多样性指数分析表明,土壤动物的多样性随样品分解时间的增长无明显的规律性变化。     

盐分对土体干缩开裂的影响

我国是一个盐碱地大国, 在广大西部和北部地区, 土壤盐碱化异常严重, 导致土体工程性质显著劣化。为了研究干旱气候条件下土体中盐浓度对水分蒸发过程及裂隙发育过程的影响, 配置了浓度分别为0moLL-1、1moLL-1、2moLL-1和3mol,L-1的NaCl溶液, 并加入土体中搅拌均匀制成初始饱和的泥浆试样, 在室内条件下使试样蒸发失水., 在整个干燥过程中, 定时测量试样的含水率变化并用相机记录裂隙发生及演化过程, 利用数字图像处理技术对所获得裂隙图像进行定量分析, 从而得到表面裂隙率、节点个数、块区个数、分形维数等裂隙量度指标。结果表明:土体中盐分的含量对干缩开裂过程有重要影响, 随着NaCl溶液浓度的增加, 土体的蒸发速率有递减趋势, 干燥过程中裂隙出现时间逐渐延迟, 对应开裂时的临界含水率逐渐减小。此外, 含盐越多的试样表面裂隙发育程度越低, 裂隙宽度、长度、分形维数等也随盐分含量的增加而不断减小。这些现象与盐分-黏土颗粒相互作用及黏土双电层变化有关。     

Floral ecology and insect visitation in riparian Tamarix sp. (saltcedar)

Climate change projections for semiarid and arid North America include reductions in stream discharge that could adversely affect riparian plant species dependent on stream-derived ground water. In order to better understand this potential impact, we used a space-for-time substitution to test the hypotheses that increasing depth-to-groundwater (DGW) is inversely related to Tamarix sp. (saltcedar) flower abundance (F) and nectar production per flower (N). We also assessed whether DGW affected the richness or abundance of insects visiting flowers. We examined Tamarix floral attributes and insect visitation patterns during 2010 and 2011 at three locations along a deep DWG gradient (3.2–4.1 m) on a floodplain terrace adjacent to Las Vegas Wash, an effluent-dominated Mojave Desert stream. Flower abundance and insect visitation patterns differed between years, but no effect from DGW on either F or N was detected. An eruption of a novel non-native herbivore, the splendid tamarisk weevil (Coniatus splendidulus), likely reduced flower production in 2011.