Sources and distribution of organic carbon and nitrogen in the Tagliamento River,Italy     

Edith?KaiserEmail author  David?B.?Arscott  Klement?Tockner  Barbara?Sulzberger 《Aquatic Sciences - Research Across Boundaries》2004,66(1):103-116

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Impact of road building on gully erosion risk: a case study from the Northern Ethiopian Highlands   总被引：1，自引：0，他引：1  

Jan Nyssen  Jean Poesen  Jan Moeyersons  Edith Luyten  Maude Veyret‐Picot  Jozef Deckers  Mitiku Haile  Gerard Govers 《地球表面变化过程与地形》2002,27(12):1267-1283

Although obvious in the field, the impact of road building on hydrology and gullying in Ethiopia has rarely been analysed. This study investigates how road building in the Ethiopian Highlands affects the gully erosion risk. The road between Makalle and Adwa in the highlands of Tigray (northern Ethiopia), built in 1993–1994, caused gullying at most of the culverts and other road drains. While damage by runoff to the road itself remains limited, off‐site effects are very important. Since the building of the road, nine new gullies were created immediately downslope of the studied road segment (6·5 km long) and seven other gullies at a distance between 100 and 500 m more downslope. The road induces a concentration of surface runoff, a diversion of concentrated runoff to other catchments, and an increase in catchment size, which are the main causes for gully development after road building. Topographic thresholds for gully formation are determined in terms of slope gradient of the soil surface at the gully head and catchment area. The influence of road building on both the variation of these thresholds and the modification of the drainage pattern is analysed. The slope gradient of the soil surface at the gully heads which were induced by the road varies between 0·06 and 0·42 m m^?1 (average 0·15 m m^?1), whereas gully heads without influence of the road have slope gradients between 0·09 and 0·52 m m^?1 (average 0·25 m m^?1). Road building disturbed the equilibrium in the study area but the lowering of topographic threshold values for gullying is not statistically significant. Increased gully erosion after road building has caused the loss of fertile soil and crop yield, a decrease of land holding size, and the creation of obstacles for tillage operations. Hence roads should be designed in a way that keeps runoff interception, concentration and deviation minimal. Techniques must be used to spread concentrated runoff in space and time and to increase its infiltration instead of directing it straight onto unprotected slopes. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Fluid inclusions in charnockites from the Bjerkreim-Sokndal massif (Rogaland,southwestern Norway): fluid origin and in situ evolution     

Edith Wilmart  Robert Clocchiatti  Jean-Clair Duchesne  Jacques L. R. Touret 《Contributions to Mineralogy and Petrology》1991,108(4):453-462

Fluid inclusions and mineral associations were studied in late-stage charnockitic granites from the Bjerkreim-Sokndal lopolith (Rogaland anorthosite province). Because the magmatic and tectonic evolutions of this complex appear to be relatively simple, these rocks are a suitable case for investigation of the origin and evolution of granulitic fluids. Fluid inclusions, primarily contained in quartz, can be divided into four types: carbonic (type I), N₂-bearing (type II), CO₂+H₂O (type III) and aqueous inclusions (type IV). For each type, the role of leakage and fluid mixing are discussed from microthermometric and Raman spectrometric data. The most striking features of CO₂-rich inclusions (the predominant fluid) is the presence of graphite in numerous, trail-bound inclusions (Ib) and its absence in a few isolated, very dense (d=1.16), pure CO₂ inclusions (Ia) and in the late carbonic inclusions (Ic). Fluid chronology and mineral assemblages suggest that carbonic Ia inclusions represent the first fluid (pure CO₂) trapped at or close to magmatic conditions (T=780–830° C, fO₂=10^-15 atm and P=7.4±1 kb), outside the graphite stability field. In contrast, type Ib inclusions enclosed graphite particles from a channelized fluid during retrograde rock evolution (P=3–4 kb and T=600° C). Decreases in T-fO₂ could explain a progressive evolution from a CO₂-rich fluid to an H₂O-rich fluid in a closed C–O–H system. However, graphite destabilization observed in type Ic inclusions implies some late introduction of external water during the last stage of retrogression. The main results of this study are the following: (1) a carbonic fluid was present in an early stage of rock evolution (probably in the charnockitic magma) and (2) this granulite occurrence offers good evidence of crossing the graphite stability field during post-magmatic evolution.  相似文献   

Chemical characterization of dissolved organic matter (DOM): A prerequisite for understanding UV-induced changes of DOM absorption properties and bioavailability   总被引：8，自引：2，他引：6  

Barbara Sulzberger  Edith Durisch-Kaiser 《Aquatic Sciences - Research Across Boundaries》2009,71(2):104-126

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Fertilization and pH effects on processes and mechanisms controlling dissolved inorganic phosphorus in soils   总被引：5，自引：0，他引：5  

Nicolas Devau  Edith Le Cadre  Frédéric Gérard 《Geochimica et cosmochimica acta》2011,75(10):2980-2996

We used of a set of mechanistic adsorption models (1-pK TPM, ion exchange and Nica-Donnan) within the framework of the component additive (CA) approach in an attempt to determine the effect of repeated massive application of inorganic P fertilizer on the processes and mechanisms controlling the concentration of dissolved inorganic phosphorus (DIP) in soils. We studied the surface layer of a Luvisol with markedly different total concentrations of inorganic P as the result of different P fertilizer history (i.e. massive or no application for 40 years). Soil pH was made to vary from acid to alkaline. Soil solutions were extracted with water and CaCl₂ (0.01 M). The occurrence of montmorillonite led us to determine the binding properties of P and Ca ions for this clay mineral.Satisfactory results were obtained using generic values for model parameters and soil-specific ones, which were either determined directly by measurements or estimated from the literature. We showed that adsorption largely controlled the variations of DIP concentration and that, because of kinetic constrains, only little Ca-phosphates may be precipitated under alkaline conditions, particularly in the P fertilized treatment. The mineral-P pool initially present in both P treatments did not dissolve significantly during the course of the experiments. The adsorption of Ca ions onto soil minerals also promoted adsorption of P ions through electrostatic interactions. The intensity of the mechanism was high under neutral to alkaline conditions. Changes in DIP concentration as a function of these environmental variables can be related to changes in the contribution of the various soil minerals to P adsorption. The extra P adsorbed in the fertilized treatment compared with the control treatment was mainly adsorbed onto illite. This clay mineral was the major P-fixing constituent from neutral to alkaline pH conditions, because the repulsion interactions between deprotonated hydroxyl surface sites and P ions were sufficiently counterbalanced by Ca ions. The drastic increase of DIP observed at acid pH was due to the effect of the lower concentration of surface sites of Fe oxides and kaolinite.In addition to confirming the validity of our approach to model DIP concentrations in soils, the present investigation showed that adsorption was the predominant geochemical process even in the P fertilized soil, and that Ca ions can have an important promoting effect on P adsorption. However the influence of the dissolution of the mineral-P pool under field conditions remained questionable.  相似文献   

A speleothem record of Holocene climate variability from southwestern Mexico     

Juan Pablo Bernal  Matthew Lachniet  Graham Mortimer  Edith Cienfuegos 《Quaternary Research》2011,75(1):104-113

A paleoclimate reconstruction for the Holocene based upon variations of δ¹⁸O in a U-Th dated stalagmite from southwestern Mexico is presented. Our results indicate that the arrival of moisture to the area has been strongly linked to the input of glacial meltwaters into the North Atlantic throughout the Holocene. The record also suggests a complex interplay between Caribbean and Pacific moisture sources, modulated by the North Atlantic SST and the position of the ITCZ, where Pacific moisture becomes increasingly more influential through ENSO since ~ 4.3 ka. The interruption of stalagmite growth during the largest climatic anomalies of the Holocene (10.3 and 8.2 ka) is evidenced by the presence of hiatuses, which suggest a severe disruption in the arrival of moisture to the area. The δ¹⁸O record presented here has important implications for understanding the evolution of the North American Monsoon and climate in southwestern Mexico, as it represents one of the most detailed archives of climate variability for the area spanning most of the Holocene.  相似文献   

Climate change,intergenerational equity and international law: An introductory note     

Edith Brown Weiss 《Climatic change》1989,15(1-2):327-335

The change in the Earth's climate caused by the accumulation of greenhouse gases in the atmosphere may be the most important environmental legacy that we leave to our descendants.Global change raises difficult issues of equity between our generation and future generations, and between different communities within future generations. International law is accustomed to addressing the effects of intentional environmental change on people who are already alive. It needs to be augmented by principles of intergenerational equity. We have certain obligations to future generations to pass on a planet in no worse condition than we received it and to give them equitable access to its resources.This requires a global strategy for climate change which will prevent excessively rapid climate change, prevent or mitigate the damage caused by climate change, and help countries to adapt to climate change. We need to avoid imposing major costs on future generations for our own benefit.To implement this strategy will require enforceable norms of behavior, which should be embodied in a Declaration of Planetary Rights and Obligations to Future Generations, and implemented in appropriate treaties and national and local legislation. Agreements should be drafted in such a way that they can incorporate increases in scientific understanding, for example by the creation of scientific advisory committees.  相似文献   

Evaluating regional climate models for simulating sub-daily rainfall extremes     

Virginia Edith Cortés-Hernández  Feifei Zheng  Jason Evans  Martin Lambert  Ashish Sharma  Seth Westra 《Climate Dynamics》2016,47(5-6):1613-1628

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Incorporating Groundwater-Surface Water Interaction into River Management Models     

Allison Valerio  Harihar Rajaram  Edith Zagona 《Ground water》2010,48(5):661-673

Accurate representation of groundwater-surface water interactions is critical to modeling low river flows in the semi-arid southwestern United States. Although a number of groundwater-surface water models exist, they are seldom integrated with river operation/management models. A link between the object-oriented river and reservoir operations model, RiverWare, and the groundwater model, MODFLOW, was developed to incorporate groundwater-surface water interaction processes, such as river seepage/gains, riparian evapotranspiration, and irrigation return flows, into a rule-based water allocations model. An explicit approach is used in which the two models run in tandem, exchanging data once in each computational time step. Because the MODFLOW grid is typically at a finer resolution than RiverWare objects, the linked model employs spatial interpolation and summation for compatible communication of exchanged variables. The performance of the linked model is illustrated through two applications in the Middle Rio Grande Basin in New Mexico where overappropriation impacts endangered species habitats. In one application, the linked model results are compared with historical data; the other illustrates use of the linked model for determining management strategies needed to attain an in-stream flow target. The flows predicted by the linked model at gauge locations are reasonably accurate except during a few very low flow periods when discrepancies may be attributable to stream gaging uncertainties or inaccurate documentation of diversions. The linked model accounted for complex diversions, releases, groundwater pumpage, irrigation return flows, and seepage between the groundwater system and canals/drains to achieve a schedule of releases that satisfied the in-stream target flow.  相似文献   

Bemerkungen zur Systematik und Ökologie einiger mit Kalk inkrustierterPhormidiumarten     

Dr. Edith Kann 《Aquatic Sciences - Research Across Boundaries》1973,35(1):141-151

The lime incrusting species of the genusPhormidium (Cyanophyta) have been revised. Bibliographical data have been compared with results of microscopical examinations. The revision led to the following proposals:Phormidium incrustatum (Näg.) Gom.,Ph. umbilicatum (Näg.) Gom.,Ph. toficola (Näg.) Gom.,Ph. calcicola Gardner andPh. subincrustatum F. E. Fritsch are synonyms and should be namedPh. incrustatum. Likewise,Ph. calcareum Kütz.,Ph. pulvinatum Woron.,Ph. yellowstonense Prát andPh. crustaceaum Woron. are synonyms and should be namedPh. calcareum.  相似文献