Remote sensing and transect-based retrieval of spatial soil and terrain (SOTER) information in semi-arid Niger

A methodology for retrieval and mapping of spatial soil and terrain data based on the SOTER approach has been developed for semi-arid Niger. Remote sensing technics and detailed ground transect investigations are used, and the collected data are integrated into a SOTER database and a Geographic Information System. Transect selection, their realization and the related problems with transect-based calculations are discussed. The method permits estimations of soil type coverages, present land use and soil degradation at different scale levels. The significant dynamics of soil redistribution are pointed out and attributed to present and past erosion events.     

Dynamics and sustainable utilization of rangeland ecosystems in arid and semi-arid climates of southern Africa

This review examines the conservation, risk, productivity, viability and acceptability of range management technology as it relates to sustaining rangeland ecosystems specifically in arid and semi-arid climates. The efficiency, cost effectiveness and risk with which rainfall is converted into plant production, and eventually gross farming income, without deterioration of natural resources form the essence of sustainability of rangeland ecosystems in these areas. Range and soil degradation can dramatically influence soil water balance, nutrient cycling, soil loss, production and the economics of a farm unit. Management for long-term sustainability often requires sacrifice of short-term welfare. With respect to deterioration and loss of productivity of natural vegetation, a co-ordinated approach is needed towards establishing a comprehensive inventory of the condition of national vegetation resources on a geographically and scientifically sound basis.     

Stepwise chemical degradation of immature S-rich kerogens from Vena del Gesso (Italy)

Stepwise chemical degradation involving cleavage of ester bonds (KOH/MeOH), sulfide and remaining ester bonds (Li/EtNH₂), ether bonds (HI/LiAlH₄) and sub-units linked to aromatic moieties (RuO₄) has been carried out on the kerogens of two immature sulfur-rich marls (IV-1.4 and 1.8, TOC ca. 1.5%) from evaporitic cycle IV of the Gesosso-solfifera Formation (Messinian, Vena del Gesso, Italy). Up to 80% of the organic matter was converted to solvent-soluble material, with the greatest proportion released by Li/EtNH₂. The majority by far of the extracts comprises polar macromolecular material which is thought to correspond to high molecular weight sub-units of the kerogen. Quantification of the small amounts (<1%) of the released GC-amenable components indicates that diagenetic sulfurization was more important in the case of kerogen IV-1.4 but that the extent of oxygen sequestration was similar in both cases; the distributions of biomarkers released by ether cleavage of the desulfurized residue and polar fraction showed differences which reveal heterogeneity in the building blocks making up different macromolecular fractions.     

Seismic energy dissipation in deteriorating systems through low‐cycle fatigue

Energy dissipation characteristics of structural members which exhibit both strength and stiffness deterioration under imposed displacement reversals are investigated. In the experimental part, 17 reinforced concrete beam specimens were tested under constant and variable amplitude inelastic displacement cycles. The constant‐amplitude tests were employed to determine the low‐cycle fatigue behaviour of specimens where the imposed displacement amplitude was the major variable. A two‐parameter fatigue model was developed in order to express the variation of dissipated energy with the number of displacement cycles. This model was then used to predict the energy dissipation of test specimens subjected to variable‐amplitude displacement cycles simulating severe seismic excitations. It has been demonstrated that the remaining energy dissipation capacity in a forthcoming displacement cycle is dependent on the energy dissipated along the completed displacement path. Moreover, it is observed that total energy dissipation is dependent on the length of the displacement path. Copyright © 2003 John Wiley & Sons, Ltd.     

天然锰钾矿氧化降解水体中的苯胺研究

天然锰钾矿去除水体中苯胺的影响因素及其机制的研究表明，酸度是影响苯胺降解反应的主要因素，温度、振荡速度、矿物用量、矿物粒径及电介质浓度都不同程度地影响苯胺的降解；当介质pH值为3．0时，160～200目锰钾矿用量为10g／L、反应温度为25℃、振荡速度为200r／min、反应4h可以使50mL浓度为20mg／L的苯胺去除95％，达到工业废水一级排放标准；天然锰钾矿在酸性条件下具有强氧化性。可以使苯胺逐步降解为无机物质。以上结果都说明天然锰钾矿降解苯胺废水是一种经济有效的方法。     

APPLICATION OF A QUASI-2D HYDRO-MORPHOLOGICAL MODEL TO THE ARGENTINEAN PARAN(A) RIVER

Herein a simplified quasi-two dimensional horizontal hydro-morphological mathematical model is presented. The governing equations for the quasi-2D horizontal time-depending flow field are represented by the well-known approach of interconnected cells. New discharge laws between cells are incorporated. The model is capable of predicting temporal changes in water depth, velocity distribution,sediment transport, bed elevation, as well as water and suspended sediment exchanges between main stream and flood plains. An application of the model to the middle reach of the Argentinean Parana River is presented. Satisfactory results were obtained during model calibration, validation and application.     

Forms of bluffs degraded for different lengths of time in emmet county,Michigan, U.S.A.

Distinct differences in morphology are found among bluffs cut and abandoned by Glacial Lake Algonquin and by the Nipissing Great Lakes in Emmet County, Michigan and modern, active bluffs presently being eroded by Lake Michigan in Mason and Manistee Counties, Michigan. The Algonquin, Nipissing, and modern bluffs are all composed of a sandy, morainic material. Because the composition and mode of formation of the three sets of bluffs are similar, it is assumed that the abandoned bluffs had the same initial configuration as the modern bluff. The morphologic differences are likely a function of the different periods of time each bluff has degraded. With time, the angle of the bluff midsection decreased, the extent of the convex crest and the concave base increased, and the angle of the crest increased. This course of hillslope degradation is believed similar to that occurring elsewhere on heavily vegetated hillslopes underlain by cohesionless material and situated in temperate, humid climates. The morphologic changes may be understood in terms of an analytical model which assumes that the rate of change in elevation at a point on a hillslope profile is proportional to the profile curvature at that point.     

Desertification in reverse? Observations from northern Burkina Faso

The idea of degradation of arid and semi-arid lands, often termed desertification in its irreversible form, due to human impact and/or climatic change has been much debated since the mid-1970s. From the time of the United Nation's Conference On Desertification in Nairobi, 1976, certain areas of northern Burkina Faso have been pointed out as examples of severe desertification. Several studies demonstrated that revitalization of a series of E–W oriented fossille dunes in the Oudalan province was ongoing. The present study includes an analysis of the trends of vegetation development in the region, covering the period 1955 to 1994, with emphasis on the fossile dunes. It is demonstrated that desertification and revitalization of dunes were phenomena associated with the period between the early 1970s and the mid-1980s, and that the decline in vegetation cover on the dunes seems to have been reversed in recent years. The analysis is based upon time series of aerial photos and satellite images, field studies of vegetation, interviews with local people and review of relevant literature. The findings are discussed with reference to the debate concerning desertification and land degradation, as well as to the current revisions of the ‘range management paradigm’. The observations indicate that the environmental history of the region is complex and cannot be boiled down to ‘human-induced irreversible degradation’. Rather they support the idea of semi-arid cultural landscapes undergoing constant change in response to both human impact and climatic trends and fluctuations.