A RIFFLE STABILITY INDEX TO EVALUATE SEDIMENT LOADING TO STREAMS1

ABSTRACT: Riffles in moderately entrenched stream reaches with gradients of 2 percent to 4 percent that have received excessive sediment from upstream have a distinctly different and higher proportion of smaller mobile particles than riffles in systems that are in dynamic equilibrium. The mobile fraction on the riffle can be estimated by comparing the relative abundance of various particle sizes present on the riffle with the dominant large particles on an adjacent bar. Riffle particles smaller than the dominant large particles on the bar are interpreted as mobile. The mobile percentile of particles on the riffle is termed “Riffle Stability Index” (RSI) and provides a useful estimate of the degree of increased sediment supply to riffles in mountain streams. The RSI addresses situations in which increases in gravel bedload from headwaters activities is depositing material on riffles and filling pools, and it reflects qualitative differences between reference and managed watersheds. The RSI correlates well with other measures of stream channel physical condition, such as V and the results of fish habitat surveys. Thus, it can be used as an indicator of stream reach and watershed condition and also of aquatic habitat quality.     

大气污染与平流层气溶胶

本文简述了大气污染与气溶胶的关系，论述了平流层气溶胶对地球辐射收支的影响，从而说明平流层气溶胶的光学性质的变化将影响全球大气环境，在此基础上，计算了不同背景平流层气溶胶的光学常数和光学特性参数。并使用模式光学常数计算了３种火山模工气溶胶的光学特性参数。同时，考察了这些特性参数对光学常数的敏感性。结果表明，后向散射系数对光学常数的变化最敏感，对于某些波长，它的相对变化可比光学常数的相对变化大一个数量     

南山铁矿风场及扩散规律风洞模拟研究

以风洞模拟方式研究中性层结条件下南山铁矿凹山采场地域边界层风场特征,并以示踪气体扩散摸拟方法给出该地域大气扩散参数的实验结果。     

Species Specificity of the Cytogenetic Stability of Fish in a Eutrophic Water Body

The micronucleus test of peripheral blood erythrocytes was used to study cytogenetic stability in bream (Abramis brama L.), perch (Perca fluviatilis L.), roach (Rutilus rutilus L.), and pike (Esox lucius L.) from a eutrophic water body not affected by anthropogenic factors. The dependence of the rate of spontaneous micronucleus formation on fish age was estimated. The effect of natural variation in abiotic environmental factors on the cytogenetic stability of species was analyzed.     

Watershed scale assessment of nitrogen and phosphorus loadings in the Indian River Lagoon basin,Florida

There is a growing evidence that the ecological and biological integrity of the lagoon has declined during the last 50 years, probably due to the decline in water quality. Establishment of a watershed scale seagrass-based nutrient load assessment is the major aim of water quality management in the Indian River Lagoon (IRL). Best estimate loadings incorporate wet and dry deposition, surface water, groundwater, sediment nutrient flux, and point source effluent discharge data. On the average, the IRL is receiving annual external loadings of 832, 645 and 94,476kg of total nitrogen (TN) and total phosphorus (TP), respectively, from stormwater discharges and agricultural runoff. The average internal cycling of TN and TP from sediment deposits in the IRL was about 42,640kg TN and 1050kg TPyr(-1). Indirect evidence suggests that atmospheric deposition has played a role in the ongoing nutrient enrichment in the IRL. The estimated total atmospheric deposition of TN and TP was about 32,940 and 824kgyr(-1), while groundwater contribution was about 84,920 and 24,275kgyr(-1), respectively, to the surface waters of the IRL. The estimated annual contribution of point effluent discharge was about 60,408kg TN and 7248kg TP. In total, the IRL basin is receiving an annual loading of about 1,053,553kg TN and 127,873kg TP. With these results, it is clear that the current rate of nutrient loadings is causing a shift in the primary producers of the IRL from macrophyte to phytoplankton- or algal-based system. The goal is to reverse that shift, to attain and maintain a macrophyte-based estuarine system in the IRL.     

地震作用下结构失稳诱发的塌陷和地裂缝机理分析

分析了地震诱发的地表塌陷和地裂缝机制。通过地裂缝微观机理分析研究发现:(1)地震造成了大量的地裂缝和塌陷,这些破坏的出现与地震发生时造成的瞬间应力变化和结构破坏密切相关;(2)利用结构突变失稳理论来研究岩土体内部结构是可行的。当应力状态满足孔隙结构失稳判别式时,结构元的变形状态将产生一个“跳跃”;(3)地震情况下岩土体颗粒之间有效接触力的增加,使得结构的变形能增大;同时导致颗粒间连接刚度的降低,导致结构的失稳,这些变化又是在瞬间发生和完成的,这就造成了在地震发生时总是伴随着大量的裂缝和塌陷的出现。     

岩溶地基土洞塌陷评价及处理

地下水(地表水)产生的渗透潜蚀作用、崩解作用等是土洞形成和发展的重要原因。对工程实例中的土洞,采用极限平衡法和压力拱分析法进行了稳定性判别。在土洞中充填砼,然后采用压力灌浆,灌浆所采用的水灰比为1∶1~1∶1.5,灌浆压力一般为0.15~0.30 MPa,地基处理效果好。     

Structural-temporal organization of a rodent community in the Teletskaya Taiga,Altai Mountains

The structural-temporal organization of a murine rodent community in the taiga has been studied near Lake Teletskoe, Mountain Altai. The results show that the long-term dynamics of indices characterizing community diversity depend mainly on changes in the structure of dominance rather than on the population dynamics of species. The distribution of species in the factor space corresponds to their preference for certain biotopes, from dry to relatively moist. An analysis of relationships within the rodent community has revealed the synchronous dynamics of species abundance and antiphase pattern of changes in the structural indices of dominant species.     

确定岩体斜坡滑动面抗剪强度的动态反分析方法

滑动结构面的抗剪强度在岩体滑坡的稳定性计算中是最重要的参数,也是最难以确定的。基于岩体抗剪强度是多种因素影响下的随机变量这一认识前提下,本文以西柏坡“中共中央解放军总部”旧址滑坡为例提出了确定岩体斜坡滑动面抗剪强度的动态反分析方法,并对该方法获得的抗剪强度的实用性进行了分析。结果表明,反分析方法是获得岩体斜坡滑动面抗剪强度的最经济、合理的途径。