Predicting catchment sediment yield in Mediterranean environments: the importance of sediment sources and connectivity in Italian drainage basins   总被引：2，自引：0，他引：2  

Joris de Vente  Jean Poesen  Paolo Bazzoffi  Anton Van Rompaey  Gert Verstraeten 《地球表面变化过程与地形》2006,31(8):1017-1034

Predicting sediment yield at the catchment scale is one of the main challenges in geomorphologic research. The application of both physics‐based models and regression models has until now not provided very satisfying results for prediction of sediment yield for medium to large sized catchments (c. >50 km²). The explanation for this lies in a combination of the large data requirements of most models and a lack of knowledge to describe all processes and process interactions at the catchment scale. In particular, point sources of sediment (e.g. gullies, mass movements), connectivity and sediment transport remain difficult to describe in most models. From reservoir sedimentation data of 44 Italian catchments, it appeared that there was a (non‐significant) positive relation between catchment area and sediment yield. This is in contrast to what is generally expected from the theory of decreasing sediment delivery rates with increasing catchment area. Furthermore, this positive relation suggests that processes other than upland erosion are responsible for catchment sediment yield. Here we explore the potential of the Factorial Scoring Model (FSM) and the Pacific Southwest Interagency Committee (PSIAC) model to predict sediment yield, and indicate the most important sediment sources. In these models different factors are used to characterize a drainage basin in terms of sensitivity to erosion and connectivity. In both models an index is calculated that is related to sediment yield. The FSM explained between 36 and 61 per cent of the variation in sediment yield, and the PSIAC model between 57 and 62 per cent, depending on the factors used to characterize the catchments. The FSM model performed best based on a factor to describe gullies, lithology, landslides, catchment shape and vegetation. Topography and catchment area did not explain additional variance. In particular, the addition of the landslide factor resulted in a significantly increased model performance. The FSM and PSIAC model both performed better than a spatially distributed model describing water erosion and sediment transport, which was applied to the same catchments but explained only between 20 and 51 per cent of the variation in sediment yield. Model results confirmed the hypothesis that processes other than upland erosion are probably responsible for sediment yield in the Italian catchments. A promising future development of the models is by the use of detailed spatially distributed data to determine the scores, decrease model subjectivity and provide spatially distributed output. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Particulate iron and manganese in the Santa Barbara Basin,California     

Alan M. Shiller  Joris M. Gieskes  N. Brian Price 《Geochimica et cosmochimica acta》1985,49(5):1239-1249

Particulate Fe and Mn may be important trace metal scavengers in the water column as well as being probable indicators of biologically mediated redox processes. A study has been made of suspended particulate composition in the Santa Barbara Basin, a shallow near-shore basin off southern California with sub-oxic conditions below sill depth. Observations have revealed several interesting phenomena relating to the geochemistry of Fe and Mn. Most striking is a profound enrichment of particulate Fe in samples from the bottom two hundred meters. These particulates have a constant Fe/P mole ratio of about three and may originate at the sediment-water interface or may be transported to the basin from local marshes. For particulate Mn, enrichments are observed both in the sub-sill waters and near the base of the euphotic zone. A consideration of particle removal rates suggests that the sub-photic zone enrichment has a biogenic origin. In the sub-sill waters, enrichment in Mn is apparently due to the precipitation of dissolved Mn diffusing from the anoxic basin sediments. A simple mass balance suggests that most of the Mn lost from the sediments is transported from the Santa Barbara Basin in dissolved form.  相似文献   

Ancient charcoal as a natural archive for paleofire regime and vegetation change in the Mayumbe,Democratic Republic of the Congo     

Wannes Hubau  Jan Van den Bulcke  Peter Kitin  Florias Mees  Geert Baert  Dirk Verschuren  Laurent Nsenga  Joris Van Acker  Hans Beeckman 《Quaternary Research》2013

Charcoal was sampled in four soil profiles at the Mayumbe forest boundary (DRC). Five fire events were recorded and 44 charcoal types were identified. One stratified profile yielded charcoal assemblages around 530 cal yr BP and > 43.5 cal ka BP in age. The oldest assemblage precedes the period of recorded anthropogenic burning, illustrating occasional long-term absence of fire but also natural wildfire occurrences within tropical rainforest. No other charcoal assemblages older than 2500 cal yr BP were recorded, perhaps due to bioturbation and colluvial reworking. The recorded paleofires were possibly associated with short-lived climate anomalies. Progressively dry climatic conditions since ca. 4000 cal yr BP onward did not promote paleofire occurrence until increasing seasonality affected vegetation at the end of the third millennium BP, as illustrated by a fire occurring in mature rainforest that persisted until around 2050 cal yr BP. During a drought episode coinciding with the ‘Medieval Climate Anomaly’, mature rainforest was locally replaced by woodland savanna. Charcoal remains from pioneer forest indicate that fire hampered forest regeneration after climatic drought episodes. The presence of pottery shards and oil-palm endocarps associated with two relatively recent paleofires suggests that the effects of climate variability were amplified by human activities.  相似文献   

The implications of data selection for regional erosion and sediment yield modelling     

Joris de Vente  Jean Poesen  Gerard Govers  Carolina Boix‐Fayos 《地球表面变化过程与地形》2009,34(15):1994-2007

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Geological and engineering characteristics of expansive soils and rocks in northern Oman   总被引：3，自引：0，他引：3  

Amer A. Al-Rawas  Ingeborg Guba  A. McGown 《Engineering Geology》1998,50(3-4):267-281

The geology and former climate of northern Oman favoured the formation of smectite clay minerals in certain materials which are implicated in ground heave problems. Investigations have shown that the smectite content of these expansive materials was developed in Oligocene, Miocene and Pliocene times. No evidence of a significant content of smectite was found in pre Eocene strata or in Quaternary strata, except for Desert Fill. It is shown that the main types of expansive materials in northern Oman are bentonitic mudstones, marls and silty mudstones, argillaceous dolomitic limestone, altered conglomerates and the desert fill derived from these. These swelling materials exist as impersistent bands within the bedrock Tertiary conglomerates and limestones. A geotechnical testing program was carried out on undisturbed samples from Sultan Qaboos University staff housing areas where building damage had occurred, to evaluate mineralogical composition, cation content and swelling characteristics. The test results characterized these soils/rocks as highly expansive type with Na-smectite as the dominant clay mineral.  相似文献   

Environmental estrogens interact with and modulate the properties of plasma sex steroid-binding proteins in juvenile Atlantic salmon (Salmo salar)     

Knut-Erik Tollefsen  Joris F. A. Meys  Jorid Frydenlund  Jrgen Stenersen 《Marine environmental research》2002,54(3-5)

Environmental chemicals may modulate the endocrine system through interaction with plasma sex steroid-binding proteins (SBP) and SBP-regulated processes. Some of these chemicals, which are known to interact with the estrogen receptor (ER), were found to bind competitively to the Atlantic salmon (Salmo salar) SBP and potentially disrupt the endocrine function of these proteins. Furthermore, both weakly acting (di-n-butyl phthalate) and potent estrogen mimics (ethynylestradiol), were able to induce a substantial up-regulation of circulating levels of SBP in vivo. Interestingly, modulation of SBP-levels was found to be a more sensitive endpoint than chemically induced interference with classical ER-mediated mechanisms for weakly acting estrogen mimics like di-(n-butyl) phthalate. Interference with the endocrine function of SBPs may thus introduce a novel mechanism for endocrine disruption, and give additional answers to the question why some weakly acting xenoestrogens are causing “estrogen-like” reproductive disturbances in developing males.  相似文献   

Effects of dietary exposure to the pyrethroid pesticide esfenvalerate on medaka (Oryzias latipes)   总被引：3，自引：0，他引：3  

Werner I  Geist J  Okihiro M  Rosenkranz P  Hinton DE 《Marine environmental research》2002,54(3-5):609-614

The pyrethroid insecticide esfenvalerate is widely used on orchard crops throughout California. In the aquatic environment, this compound is likely to accumulate in sediments, food particles and benthic organisms due to its lipophilicity and environmental persistence. This pilot project tested the hypothesis that esfenvalerate is toxic to medaka (Oryzias latipes) when taken up with the diet. For 7 days fish were fed diets, which contained esfenvalerate in three different concentrations (4, 21, 148 mg/kg, measured). Endpoints measured were mortality, fecundity, fertilization and hatching success of embryos, viability of larvae and cellular stress protein (hsp60, hsp70, hsp90) levels. The toxicity of aqueous exposure of medaka to esfenvalerate was also determined. Whereas the 96-h LC50 in the aqueous exposure was <9.4 microg/l, the dietary exposure did not cause mortality. Possible effects of dietary esfenvalerate were seen on fertilization and hatching success and the number of non-viable larvae. Expression of hsp60 and hsp90 showed a dose-dependent response pattern.  相似文献   

Depth Distribution and Abundance of Northern Adriatic Littoral Rocky Reef Blennioid Fishes (Blenniidae and Tripterygion)   总被引：3，自引：0，他引：3  

Ingeborg P. Illich  Kurt Kotrschal 《Marine Ecology》1990,11(4):277-289

Abstract. Species' depth distributions and abundances were visually assessed along 24 transects in a northern Adriatic assemblage of blennioid fishes (14 species of Blenniidae , 1 species of Triptery-giidue). Total abundance of blennioids was highest in 0.5-1 m depth, decreasing upwards and downwards. Species diversity (S hannon -W iener ) is highest at the shallowest depth (0-0.5 in). The curybathic species Parablennius incognitus, Lipophrys dalmatinus, Tripterygion tripteronotus , and Parablennius tentacularis were most abundant at all depths (relative to the species investigated). All stenobathic species were most abundant at 0-0.5 m. Depth distribution patterns and abundance ranks of species were similar at western, eastern, southern, and northern transects.  相似文献   

Acid-base and copper-binding properties of three organic matter fractions isolated from a forest floor soil solution     

Joris W.J. van Schaik  Dan B. Kleja 《Geochimica et cosmochimica acta》2010,74(4):1391-4019

Vast amounts of knowledge about the proton- and metal-binding properties of dissolved organic matter (DOM) in natural waters have been obtained in studies on isolated humic and fulvic (hydrophobic) acids. Although macromolecular hydrophilic acids normally make up about one-third of DOM, their proton- and metal-binding properties are poorly known. Here, we investigated the acid-base and Cu-binding properties of the hydrophobic (fulvic) acid fraction and two hydrophilic fractions isolated from a soil solution. Proton titrations revealed a higher total charge for the hydrophilic acid fractions than for the hydrophobic acid fraction. The most hydrophilic fraction appeared to be dominated by weak acid sites, as evidenced by increased slope of the curve of surface charge versus pH at pH values above 6. The titration curves were poorly predicted by both Stockholm Humic Model (SHM) and NICA-Donnan model calculations using generic parameter values, but could be modelled accurately after optimisation of the proton-binding parameters (pH ? 9). Cu-binding isotherms for the three fractions were determined at pH values of 4, 6 and 9. With the optimised proton-binding parameters, the SHM model predictions for Cu binding improved, whereas the NICA-Donnan predictions deteriorated. After optimisation of Cu-binding parameters, both models described the experimental data satisfactorily. Iron(III) and aluminium competed strongly with Cu for binding sites at both pH 4 and pH 6. The SHM model predicted this competition reasonably well, but the NICA-Donnan model underestimated the effects significantly at pH 6. Overall, the Cu-binding behaviour of the two hydrophilic acid fractions was very similar to that of the hydrophobic acid fraction, despite the differences observed in proton-binding characteristics. These results show that for modelling purposes, it is essential to include the hydrophilic acid fraction in the pool of ‘active’ humic substances.  相似文献   

Containment of groundwater pollution (methyl tertiary butyl ether and benzene) to protect a drinking-water production site in Belgium     

Pieter Jan Haest  Richard Lookman  Ilse Van Keer  Johan Patyn  Jan Bronders  Marjan Joris  Jan Bellon  Florimond De Smedt 《Hydrogeology Journal》2010,18(8):1917-1925

The subsurface migration of methyl tertiary butyl ether (MTBE) and benzene towards a drinking-water production site in Belgium was monitored for 9 years. A large gasoline spill at a nearby fuel station had caused a 500-m long and 50-m-wide pollution plume of MTBE (10?30 mg/L) and benzene (2?10 mg/L). In order to prevent any intrusion of pollutants into the drinking-water supply, a conceptual model was used to design a pump-and-treat system that intercepted the gasoline-contaminated groundwater emanating from the spill. The contaminated soil in the spill zone was excavated. A numerical mass transport model was developed to evaluate the ongoing plume containment. The model describes the subsurface MTBE migration and was regularly updated, based on groundwater monitoring data and the measured mass of MTBE extracted with the pump-and-treat system. With continued interception pumping, the MTBE plume can be remediated in 14 years. Without it, MTBE and benzene concentrations up to 600 μg/L could have reached the drinking-water production site and the plume would persist for 9 years longer. Source zone treatment combined with plume interception pumping is a suitable risk-based remediation strategy for the containment of MTBE and benzene groundwater pollution.  相似文献