Climate change impact on extreme precipitation and peak flood magnitude and frequency: observations from CMIP6 and hydrological models     

Meresa  Hadush  Tischbein  Bernhard  Mekonnen  Tewodros 《Natural Hazards》2022,111(3):2649-2679

Natural Hazards - Changes in climate intensity and frequency, including extreme events, heavy and intense rainfall, have the greatest impact on water resource management and flood risk management....  相似文献   

Aspects of U-Th fractionation in Tertiary limestones and calcretes of Dhofar,southern Oman     

Bernhard Pracejus  Narasimman Sundararajan  Salah Al-Khirbash  Talal Al-Hosni  A. Ebrahimi  Shakil Al-Bulushi  Ali Al-Lazki  Musadem Al-Maashani 《Chemie der Erde / Geochemistry》2018,78(4):479-489

This paper presents findings from a comprehensive geochemical and geophysical re-examination of known radiogenic anomalies in Tertiary limestones and (sub-)recent calcretes of southwestern Dhofar in the Sultanate of Oman. U-Th-enrichments seem to be associated with deep-rooted fault systems that cross-cut C_org-rich shales at depths of some 800–1000?m, which generally show elevated gamma-ray levels in southern Oman and act as the initial geochemical trap. Metals and radiogenic elements, such as K (max?1945?ppm), U (max?44?ppm), and Th (max?26?ppm) mobilised from these rocks and emplaced higher up in the faults must have constituted radiogenic lineaments at and near the surface (observed in a different but difficult to access location). However, successive weathering partially obscured such anomalies through further re-mobilisation/-mineralisation processes within the calcretes that also enriched Sr and V. In these carbonates, uranium correlates positively with Sr but not very well with V, while thorium shows moderate positive correlations with Sr and V. Both U and Th are also not present (i.e., below the detection limits of a few ppm) in a second sample group that represents background conditions. Being much more immobile than U, Th remained closer to the original western fault positions of the examined site (outlined by magnetics and VLF-EM during the surveys), while uranium moved down-dip over the plateau and through underlying sub-horizontal strata towards the eastern fault system. Here, supergene Sr-enriched calcite preferentially incorporated U, thus reflecting the observed U-Th fractionation.  相似文献   

Linking watershed disturbance with nearshore sedimentation and the shell beds of Lake Tanganyika (Mahale Mountains,Tanzania)     

James Busch  Michael Soreghan  Kirsten de Beurs  Michael McGlue  Ismael Kimirei  Andrew Cohen  Emily Ryan 《Environmental Earth Sciences》2018,77(13):514

Extensive deposits of shell-rich sediments in the nearshore environment of Lake Tanganyika, Africa, form a unique habitat for a diverse group of endemic gastropods, crustaceans, fish and sponges, among other organisms. Anthropogenic alteration of the lake’s hinterland from deforestation, fires, and agriculture threaten this crucial habitat through sediment pollution of the littoral environment. This study examines the sedimentology of these nearshore shell beds along a study area north of the Mahale Mountains (Tanzania) to test whether varying levels of watershed disturbance, determined by analysis of satellite imagery, within three moderately sized watersheds (>?100 km²) results in sedimentological differences offshore. The results show that shell beds adjacent to disturbed watersheds (Lagosa and Rukoma) contain more fine-grained sediment compared to shell beds offshore of the undisturbed watershed (Katumbi). Widespread burning, clearance, and land cultivation, and rains of the wet season are causal factors that result in significant differences in fine-grained sedimentation, larger sediment plumes offshore, and increased shoreline progradation. In areas most affected by sedimentation, sponges are largely absent, and shell coverage, which is a measure of fish-nesting capabilities, is lower. The discovery of a small population of live Neothauma tanganyicense offshore of the Katumbi river suggests that the presence of shell-bed forming gastropods in front of a relatively low disturbance watershed, and their conspicuous absence offshore of the other two watersheds, could be related to recent watershed disturbance and increased sedimentation. The increased fine-grained sedimentation and limited shell production by the reduced modern gastropod populations may signal that the shell-bed ecosystem of Lake Tanganyika is at risk.  相似文献   

Application of multiple-isotope and groundwater-age data to identify factors affecting the extent of denitrification in a shallow aquifer near a river in South Korea     

Dugin Kaown  Eun-Hee Koh  Bernhard Mayer  Heejung Kim  Dong Kyu Park  Byeong-Hak Park  Kang-Kun Lee 《Hydrogeology Journal》2018,26(6):2009-2020

The extent of denitrification in a small agricultural area near a river in Yangpyeong, South Korea, was determined using multiple isotopes, groundwater age, and physicochemical data for groundwater. The shallow groundwater at one monitoring site had high concentrations of NO₃-N (74–83 mg L^?1). The δ¹⁵N-NO₃ values for groundwater in the study area ranged between +9.1 and +24.6‰ in June 2014 and +12.2 to +21.6‰ in October 2014. High δ¹⁵N-NO₃ values (+10.7 to +12.5‰) in both sampling periods indicated that the high concentrations of nitrate in the groundwater originated from application of organic fertilizers and manure. In the northern part of the study area, some groundwater samples showed elevated δ¹⁵N-NO₃ and δ¹⁸O-NO₃ values, which suggest that nitrate was removed from the groundwater via denitrification, with N isotope enrichment factors ranging between ?4.8 and ?7.9‰ and O isotope enrichment factors varying between ?3.8 and ?4.9‰. Similar δD and δ¹⁸O values of the surface water and groundwater in the south appear to indicate that groundwater in that area was affected by surface-water infiltration. The mean residence times (MRTs) of groundwater showed younger ages in the south (10–20 years) than in the north (20–30 years). Hence, it was concluded that denitrification processes under anaerobic conditions with longer groundwater MRT in the northern part of the study area removed considerable amounts of nitrate. This study demonstrates that multi-isotope data combined with physicochemical data and age-dating information can be effectively applied to characterize nitrate contaminant sources and attenuation processes.  相似文献   

Geochemistry and eruptive behaviour of the Finca la Nava maar volcano (Campo de Calatrava,south-central Spain)     

Matthias Bernhard Lierenfeld  Hannes B. Mattsson 《International Journal of Earth Sciences》2015,104(7):1795-1817

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Erratum to: The Alpine nappe stack in western Austria: a crustal-scale cross section     

Hannah Pomella  Hugo Ortner  Michael Zerlauth  Bernhard Fügenschuh 《International Journal of Earth Sciences》2015,104(3):747-748

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Triggering an Eruptive Flare by Emerging Flux in a Solar Active-Region Complex     

Rohan E. Louis  Bernhard Kliem  B. Ravindra  Georgios Chintzoglou 《Solar physics》2015,290(12):3641-3662

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Addressing uncertainty upstream or downstream of accounting for emissions reductions from deforestation and forest degradation     

Johanne Pelletier  Jonah Busch  Catherine Potvin 《Climatic change》2015,130(4):635-648

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Hygroscopic properties of aerosol particles in the north‐eastern Atlantic during ACE‐2     

Erik Swietlicki  Jingchuan Zhou  David S. Covert  Kaarle Hämeri  Bernhard Busch  Minna Väkeva  Ulrike Dusek  Olle H. Berg  Alfred Wiedensohler  Pasi Aalto  Jyrki Mäkelä  Bengt G. Martinsson  Giorgos Papaspiropoulos  Besim Mentes  Göran Frank  Frank Stratmann 《Tellus. Series B, Chemical and physical meteorology》2000,52(2):201-227

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Isotope hydrology of the Oldman River basin,southern Alberta,Canada     

Luc Rock  Bernhard Mayer 《水文研究》2007,21(24):3301-3315

The partially semi-arid Oldman River basin (OMRB), located in southern Alberta (Canada), has an area of 28 200 km², is forested in its western headwater part, and is used for agriculture in its eastern part. Hydrometric measurements indicate that flow in the Oldman River has decreased by ∼34% between 1913 and 2003, and it is predicted that water withdrawals will increase in the next 20 years. The objective of this study was to determine whether isotope ratio measurements can provide further insight into the water dynamics of the Oldman River and its tributaries. Surface water samples were collected monthly between December 2000 and March 2003. Groundwater samples were taken from 58 wells during one-time sampling trips. Runoff within the OMRB is currently about 70 mm year⁻¹, with a corresponding runoff ratio of 0·18. Seasonal flow characteristics are markedly different upstream and downstream of the Oldman River reservoir. Upstream, sharp increases in flow in late spring and early summer are followed by a rapid decrease to base flow levels. Downstream, a prolonged high flow peak is observed due to the storage effect of the Oldman River reservoir. The seasonal variation in the isotopic composition of surface water from upstream sites is small. This suggests that peak runoff is not predominantly generated by melting snow accumulated during the preceding winter, but mainly by relatively well-mixed young groundwater. A significant increase in the δ¹⁸O and δ²H values in the downstream part of the basin was observed. The increase in the isotopic values is partly due to surface water and groundwater influx with progressively higher δ¹⁸O and δ²H values in the eastern part, and partly due to evaporation. Hence, the combination of hydrometric data with isotope measurements yields valuable insights into the water dynamics in the OMRB that may be further refined with more intensive measurement programmes in the future. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献