CONTROL OF GULLY EROSION USING STIFF GRASSES

Concentrated flow can cause gully formation on sloping lands and in riparian zones. Current practice for riparian gully erosion control involves blocking the gully with a structure comprised of an earthen embankment and a metal or plastic pipe. Measures involving native vegetation would be more attractive for habitat recovery and economic reasons. To test the hypothesis that switchgrass （Panicum virgatum L.） hedges planted at 0.5-m vertical intervals within a gully would control erosion, a series of hedges was established in four concentrated flow channels. Two of the channels were previously eroded trapezoidal channels cut into compacted fill in an outdoor laboratory. The other two channels were natural gullies located at the edge of floodplain fields adjacent to an incised stream. While vegetation was dormant, artificial runoff events were created in the two laboratory gullies and one of the natural gullies using synthetic trapezoidal-shaped hydrographs with peak discharge rates of approximately 0.03, 0.07, and 0.16 m3/s. During these tests flow depth, velocity, turbidity, and soil pore water pressures were monitored. The fourth gully was subjected to a series of natural runoff events over a five-month period with peaks up to 0.09 m3/s. Flow depths in all tests were generally 〈 0.3 m, and flow velocities varied spatially and exceeded 2.0 m/s at the steepest points of the gullies. Erosion rates were negligible for controlled flow experiments, but natural flows in the fourth gully resulted in 1 m ofthalweg degradation, destroying the central portions of the grass hedges, most likely due to the highly erodible nature of the soils at this site. Geotechnical modeling of soil steps reinforced with switchgrass roots showed factors of safety 〉 1 for step heights 〈 0.5 m, but instability was indicated for step heights 〉1 m, consistent with the experimental observations.     

电磁和电离层监测的短期地震预报系统

最近科学界确定和公认这样一个事实：在大地震（火山喷发）之前的几天或几小时,在强震和火山活动区的地壳和对流层中存在电磁耦合过程,在电离层内存在异常变化。解释这一现象的一批物理模型出现了。其中最可能的模型基于大气边界层地壳发射物（氡、惰性气体和金属气溶胶）的化学反应。这些发射物改变了边界层的电导率,从而改变了活动区域内的大气电场值。根据实验测量,在大地震前几天或几小时,地表的地震感应的垂直电场强度可达到1至几个kV／m,而在无干扰情况下该值为100v／m。异常电场渗透到电离层引起了不同种类的变化（离子成分、电子密度、标高、电子温度等的变化）,这些变化用实验方法可以从地面及人造卫星上测量到。这样的变化被称作地震的电离层前兆。电离层前兆的优点在于电离层把活动区域作为一个整体,而不只是事件在地面上发生的一个点进行测量。这就避免了导致地面测量的物理和地球化学前兆中出现错误的前兆镶嵌式特征。第二个优点是与其他前兆比较电离层前兆的出现有稳定的时间尺度,这使它在短临地震预报中更具实用价值。因为对所有IASPEI需求的响应,我们现有的知识水平使得电离层前兆的短期地震预报成为可能。逼近震中的位置可以从电离层前兆沿磁力线到地面的投影估计出来。要预报的地震震级可以由电离层中被改变区域的大小估计出来。发震时间可以从电离层前兆出现的时间估计出来。考虑到提议的短临预报系统是第一次创建,地震参数测定的精确度将在系统测试阶段加以确定。作为第一步,这些参数可在理论上估计出来。项目任务阐明如下：（1）在墨西哥Guerrem州创建连续的电磁和电离层监测系统包括基于地面的电离层测高仪,IGEF UNAM和INEGI的GPS接收仪网络,电场探测器网络,监测P．H脉冲的高频（HF）接收仪,甚低频（VLF）接收仪,高频（HF）多普勒装置,氧元素的557．7nm和630nm谱线的光学测量法,磁力仪网络。（2）测试系统的质量,用实验的方法确定虚报和错报的概率及地震参数测定的精确度。（3）如果结果没有问题,就在墨西哥Guerrero州和墨西哥的所有地震活动区应用该系统。（4）把该体系推荐给其他遭受地震灾害的国家,使其在他们的地域内应用。部分已创建的体系和所使用的技术受专利保护。     

塔里木盆地下古生界碳酸盐岩热液岩溶的特征及地质模型

随着塔中地区下古生界碳酸盐岩油气勘探地持续深入,分别在野外露头,塔中地区相关探井奥陶系储层中发现有萤石、闪锌矿、天青石、重晶石、硬石膏、焦沥青及热液石英等一系列热液矿物及其组合,越来越多的地质资料表明热液岩溶储层可能是塔里木盆地下古生界碳酸盐岩油气勘探中被忽视的一个重要储层类型。〖JP2〗通过总结近6年大量的针对野外露头热液岩溶现象地实地观察测量,以及通过对塔中82井区—24井区奥陶系储层发育段大量的岩石薄片观察、矿物能谱测定、地层水锶同位素测试,断裂性质的分析,深入研究热液溶蚀流体的活动特点以及对形成优质储层的控制作用,最终建立了热液岩溶储层的地质模型。研究表明,热液矿物主要沿断裂伴生的构造溶蚀缝和溶蚀孔洞发育,断裂是热液运移的主要通道,是形成优质储层的重要控制因素。塔中地区沿海西期走滑断裂附近的奥陶系灰岩将广泛发育热液溶蚀改造形成的储层,为塔中西部上奥陶统沿走滑断裂向内带拓展油气勘探打下了基础。     

Glass and Mineral Chemistry of Northern Central Indian Ridge Basalts:Compositional Diversity and Petrogenetic Significance

Abstract: The glass and mineral chemistry of basalts examined from the northern central Indian ridge (NCIR) provides an insight into magma genesis around the vicinity of two transform faults: Vityaz (VT) and Vema (VM). The studied mid-ocean ridge basalts (MORBs) from the outer ridge flank (VT area) and a near-ridge seamount (VM area) reveal that they are moderately phyric plagioclase basalts composed of plagioclase (phenocryst [An60–90] and groundmass [An35–79]), olivine (Fo81–88), diopside (Wo45–51, En25–37, Fs14–24), and titanomagnetite (FeOt ~63.75 wt% and TiO2 ~22.69 wt%). The whole-rock composition of these basalts has similar Mg# [mole Mg/mole(Mg+Fe2+)] (VT basalt: ~0.56–0.58; VM basalt: ~0.57), but differ in their total alkali content (VT basalt: ~2.65; VM basalt: ~3.24). The bulk composition of the magma was gradually depleted in MgO and enriched in FeOt, TiO2, P2O5, and Na2O with progressive fractionation, the basalts were gradually enriched in Y and Zr and depleted in Ni and Cr. In addition, the SREE of magma also increased with fractionation, without any change in the (La/Yb)N value. Glass from the VM seamount shows more fractionated characters (Mg#: 0.56–0.57) compared to the outer ridge flank lava of the VT area (Mg#: 0.63–0.65). This study concludes that present basalts experienced low-pressure crystallization at a relatively shallow depth. The geochemical changes in the NCIR magmas resulted from fractional crystallization at a shallow depth. As a consequence, spinel was the first mineral to crystallize at a pressure >10 kbar, followed by Fe-rich olivine at <10 kbar pressure.     

People’s perception and socioeconomic determinants of soil erosion:A case study of Samanalawewa watershed,Sri Lanka

Though soil erosion is an important concern in Sri Lanka, there is a dearth of baseline information on soil erosion in many ofits watersheds, which obstructs monitoring of soil erosion and mitigating its effects. In order to assess soil erosion in a critical watershed and to identify its determinants, the Samanalawewa watershed, which contains one of the main hydropower generating reservoirs in Sri Lanka, was selected for this study. Remote-sensing (RS) and geographic information system (GIS) based modeling...     

育空中南部小萨蒙湖地区不连续多年冻土中的滑坡

随着不连续多年冻土发育区的日益增多,人们日益关注边坡灾害评价。为应对马贡迪河滑坡——大规模流动型滑动的发生,启动了目前的研究项目,其目的旨在鉴别和描述育空中部小萨蒙湖地区的边坡灾害。在研究区,通过地形评估研究确定了超过35个过去和现在的滑坡区。2004年夏季完成了调查工作,获得了地形评估的地形情况以及进一步描述最主要和最活跃的滑坡。本文概述了该研究项目,总结了小萨蒙湖地区发现的四种截然不同的滑坡情况。四种情况分别为：泥石流;岩石滑塌;双重流和多级牵引式滑塌。     

澳大利亚寒武系生物地层研究新进展(英文)

澳大利亚寒武系集中分布在一南北向分布的从澳大利亚的北部、中部直到南澳大利亚克拉通地块上,少量寒武纪地层分布在新南威尔士、维多利亚和塔斯马尼亚。寒武系的底在中澳大利亚的Amadeus盆地出露得最好。下寒武统(大致相当于纽芬兰统和第二统)在澳大利亚北部大多数是不含化石的火山岩,而在澳大利亚中部和南澳大利亚的盆地中,其中最有名的是南澳大利亚的Arrowie和Stansbury盆地则是各种含化石的巨厚沉积序列。澳大利亚的下寒武统没有分阶方案,尽管在生物地层研究上最近取得很大进展,现在可以利用疑源类、遗迹化石、古杯类、三叶虫、腕足类、软体动物和其他小壳化石进行化石带的划分。很长一段时间内澳大利亚中部和北部的Ord-ian阶被认为是中寒武世最早期的,现在证明它可能相当于第二统的全部或者一部分;含化石的中寒武统和芙蓉统(或上寒武统)在Georgina盆地东部发育非常完整,在中澳大利亚、新南威尔士、维多利亚和塔斯马尼亚也可见到,都可以划分到阶。芙蓉统的底大致与Idamean阶的底相当。化石带的建立主要综合考虑球接子三叶虫、多节类三叶虫,自Iverian期晚期起再加上牙形类化石。寒武系的顶大致相当于Warendan阶的底,相关地层在Georgina盆地东部发育得很好。     

Use of exposure time and life expectancy in models for toxicity to aquatic organisms

The exposure time is a variable which is usually not incorporated into models for toxicity. However, with persistent organic pollutants (POPs) exhibiting a nonspecific mode of action and lipophilic properties this variable can be modeled by the usage of the internal concentrations as a measure of the toxicity with fish. The bioconcentration process with fish is a relatively well understood and predictable process which allows the calculation of the internal lethal concentration. When the exposure time is relatively short the critical internal lethal concentrations are relatively constant for the group of POPs whereaas the LC50 measured in the ambient water is quite variable. When the exposure time is relatively long, results on the measurement of the critical internal concentration with fish over different exposure times has demonstrated that the internal lethal concentration falls with increasing exposure times in a consistent and predictable manner. This reduction in life expectancy can be described in a model which can be used to estimate the critical internal concentration for any exposure time. It also provides information useful in assessing the risk to fish and potentially other species due to the occurrence of residues of POPs in natural aquatic systems. It is suggested that these relationships can be extended to other groups of organisms and chemicals.     

Geochemical tracers to evaluate hydrogeologic controls on river salinization

The salinization of rivers, as indicated by salinity increases in the downstream direction, is characteristic of arid and semiarid regions throughout the world. Historically, salinity increases have been attributed to various mechanisms, including (1) evaporation and concentration during reservoir storage, irrigation, and subsequent reuse; (2) displacement of shallow saline ground water during irrigation; (3) erosion and dissolution of natural deposits; and/or (4) inflow of deep saline and/or geothermal ground water (ground water with elevated water temperature). In this study, investigation of salinity issues focused on identification of relative salinity contributions from anthropogenic and natural sources in the Lower Rio Grande in the New Mexico-Texas border region. Based on the conceptual model of the system, the various sources of water and, therefore, salinity to the Lower Rio Grande were identified, and a sampling plan was designed to characterize these sources. Analysis results for boron (delta(11)B), sulfur (delta(34)S), oxygen (delta(18)O), hydrogen (delta(2)H), and strontium ((87)Sr/(86)Sr) isotopes, as well as basic chemical data, confirmed the hypothesis that the dominant salinity contributions are from deep ground water inflow to the Rio Grande. The stable isotopic ratios identified the deep ground water inflow as distinctive, with characteristic isotopic signatures. These analyses indicate that it is not possible to reproduce the observed salinization by evapotranspiration and agricultural processes alone. This investigation further confirms that proper application of multiple isotopic and geochemical tracers can be used to identify and constrain multiple sources of solutes in complex river systems.     

Esterases activities and lipid peroxidation levels in muscle tissue of the shanny Lipophrys pholis along several sites from the Portuguese Coast

This study is part of a project aiming to validate the use of the intertidal shanny Lipophorys pholis as a sentinel species in pollution monitoring in NW European marine ecosystems. To this end, a characterisation of acethylcholin (AChE), butyrylcholin (BChE) and propionylcholin (PrChE) esterases in L. pholis muscle was performed and the results indicated that AChE was predominant. Furthermore, the use of eserine sulphate and BW284c51 (0.64–800 μM), and iso-OMPA (0.08–16 mM), confirmed the measurement of true cholinesterases (ChEs) as well as the presence of pseudocholinesterases. The field application of these markers to L. pholis, sampled in seven locations along the Portuguese coast, revealed that fish were likely to be affected by neurotoxic compounds. This was indicated by the significant depletion of AChE (p < 0.05) in animals collected at urban and industrialised sites, compared with those from reference locations. The inclusion of a marker of effect, measured as lipid peroxidation levels in muscle tissue, also revealed the existence of site differences. Overall, the study further validates the utility of L. pholis in pollution monitoring studies.