Terrigenous (Sc, Fe, K, Mg, Al, Ti) and anthropogenic (Pb and Cu) element fluxes were measured in a new sediment core from Lake Biel (Switzerland) and in previously well-documented cores from two upstream lakes (Lake Brienz and Lake Thun). These three large peri-alpine lakes are connected by the Aare River, which is the main tributary to the High Rhine River. Major and trace element analysis of the sediment cores by inductively coupled plasma mass spectrometry (ICP-MS) shows that the site of Lake Brienz receives three times more terrigenous elements than the two other studied sites, given by the role of Lake Brienz as the first major sediment sink located in the foothills of the Alps. Overall, the terrigenous fluxes reconstructed at the three studied sites suggest that the construction of sediment-trapping reservoirs during the twentieth century noticeably decreased the riverine suspended sediment load at a regional scale. In fact, the extensive river damming that occurred in the upstream watershed catchment (between ca. 1930 and 1950 and up to 2,300 m a.s.l.) and that significantly modified seasonal suspended sediment loads and riverine water discharge patterns to downstream lakes noticeably diminished the long-range transport of (fine) terrigenous particles by the Aare River. Concerning the transport of anthropogenic pollutants, the lowest lead enrichment factors (EFs Pb) were measured in the upstream course of the Aare River at the site of Lake Brienz, whereas the metal pollution was highest in downstream Lake Biel, with the maximum values measured between 1940 and 1970 (EF Pb > 3). The following recorded regional reduction in aquatic Pb pollution started about 15 years before the actual introduction of unleaded gasoline in 1985. Furthermore, the radiometric dating of the sediment core from Lake Biel identifies three events of hydrological transport of artificial radionuclides released by the nuclear reactor of Mühleberg located at more than 15 km upstream of Lake Biel for the time period 1970–2000. 相似文献
The Mw 6.2 Baladeh earthquake occurred on 28 May 2004 in the Alborz Mountains, northern Iran. This earthquake was the first strong shock in this intracontinental orogen for which digital regional broadband data are available. The Baladeh event provides a rare opportunity to study fault geometry and ongoing deformation processes using modern seismological methods. A joint inversion for hypocentres and a velocity model plus a surface-wave group dispersion curve analysis were used to obtain an adapted velocity model, customised for mid- and long-period waveform modelling. Based on the new velocity model, regional waveform data of the mainshock and larger aftershocks (Mw?≥3.3) were inverted for moment tensors. For the Baladeh mainshock, this included inversion for kinematic parameters. All analysed earthquakes show dominant thrust mechanisms at depths between 14 and 26 km, with NW–SE striking fault planes. The mainshock ruptured a 28° south-dipping area of 24 × 21 km along a north-easterly direction. The rupture plane of the mainshock does not coincide with the aftershock distribution, neither in map view nor with respect to depth. The considered aftershocks form two main clusters. The eastern cluster is associated with the mainshock. The western cluster does not appear to be connected with the rupture plane of the mainshock but, instead, indicates a second activated fault plane dipping at 85° towards the north. 相似文献
One effect of climate change may be increased hurricane frequency or intensity due to changes in atmospheric and geoclimatic
factors. It has been hypothesized that wetland restoration and infrastructure hardening measures may improve infrastructure
resilience to increased hurricane frequency and intensity. This paper describes a parametric decision model used to assess
the tradeoffs between wetland restoration and infrastructure hardening for electric power networks. We employ a hybrid economic
input–output life-cycle analysis (EIO-LCA) model to capture: construction costs and life-cycle emissions for transitioning
from the current electric power network configuration to a hardened network configuration; construction costs and life-cycle
emissions associated with wetland restoration; and the intrinsic value of wetland restoration. Uncertainty is accounted for
probabilistically through a Monte Carlo hurricane simulation model and parametric sensitivity analysis for the number of hurricanes
expected to impact the project area during the project cycle and the rate of wetland storm surge attenuation. Our analysis
robustly indicates that wetland restoration and undergrounding of electric power network infrastructure is not preferred to
the “do-nothing” option of keeping all power lines overhead without wetland protection. However, we suggest a few items for
future investigation. For example, our results suggest that, for the small case study developed, synergistic benefits of simultaneously
hardening infrastructure and restoring wetlands may be limited, although research using a larger test bed while integrating
additional costs may find an enhanced value of wetland restoration for disaster loss mitigation. 相似文献
A new taxon, ?Crassodontidanus gen. nov. of Hexanchiformes (cow sharks) from the Jurassic of Germany is described. It is characterized by peculiar teeth combining apomorphic (serrated mesial cutting edge of the main cusp) and plesiomorphic features (deep root with convex mesial and distal margins in labial and lingual views; protruding lingual root bulge). This character combination readily distinguishes members of the new taxon from all other known extant (Heptranchias, Hexanchus, Notorynchus) and extinct (?Gladioserratus, ?Notidanodon, ?Notidanoides, ?Pachyhexanchus, ?Paraheptranchias, ?Weltonia) hexanchiforms. Currently, two species, ?C. serratus (type species; Late Jurassic, Late Kimmeridgian of Nusplingen, South Germany) and ?C. wiedenrothi (Early Jurassic, Early Pliensbachian of Gretenberg (Hanover), North Germany) are assigned to this taxon. ?Crassodontidanus gen. nov. is member of ?Crassonotidae fam. nov. and sister to ?Notidanoides Maisey,1986 and ?Pachyhexanchus Cappetta,1990. We consider ?Notidanusamalthei Oppel,1854 from the Pliensbachian of South Germany, ?Notidanusinsignis Seguenza,1887 from the Oxfordian of Sicily (Italy) and ?Notidanuswagneri Agassiz, 1843 from the Early Tithonian of Solnhofen (South Germany) nomina dubia and nomina nuda, respectively. The family ?Crassonotidae comprises plesiomorphic hexanchiforms ranging from the Sinemurian (Early Jurassic) to the Hauterivian (Early Cretaceous). 相似文献
Diversity within distinct trophic groups is proposed to increase ecosystem functions such as the productivity of this group and the efficiency of resource use. This proposition has mainly been tested with plant communities, consumer assemblages, and multitrophic microbial assemblages. Very few studies tested how this diversity–productivity relationship varies under different environmental regimes such as disturbances. Coastal benthic assemblages are strongly affected by temporal instability of abiotic conditions. Therefore, we manipulated benthic ciliate species richness in three laboratory experiments with three diversity levels each and analyzed biomass production over time in the presence or absence of a single application of a disturbance (ultraviolet-B [UVB] radiation). In two out of three experiments, a clear positive relationship between diversity and productivity was found, and also the remaining experiment showed a small but nonsignificant effect of diversity. Disturbance significantly reduced the total ciliate biomass, but did not alter the relation between species richness and biomass production. Significant overyielding (i.e., higher production at high diversity) was observed, and additive partitioning indicated that this was caused by niche complementarity between ciliate species. Species-specific contribution to the total biomass varied idiosyncratically with species richness, disturbance, and composition of the community. We thus present evidence for a significant effect of consumer diversity on consumer biomass in a coastal ciliate assemblage, which remained consistent at different disturbance regimes. 相似文献
Hydrological and bioclimatic processes that lead to drought may stress plants and wildlife, restructure plant community type and architecture, increase monotypic stands and bare soils, facilitate the invasion of non-native plant species and accelerate soil erosion. Our study focuses on the impact of a paucity of Colorado River surface flows from the United States (U.S.) to Mexico. We measured change in riparian plant greenness and water use over the past two decades using remotely sensed measurements of vegetation index (VI), evapotranspiration (ET) and a new annualized phenology assessment metric (PAM) for ET. We measure these long-term (2000–2019) metrics and their short-term (2014–2019) response to an environmental pulse flow in 2014, as prescribed under Minute 319 of the 1944 Water Treaty between the two nations. In subsequent years, small-directed flows were provided to restoration areas under Minute 323. We use 250 m MODIS and 30 m Landsat imagery to evaluate three vegetation indices (NDVI, EVI, EVI2). We select EVI2 to parameterize an optical-based ET algorithm and test the relationship between ET from Landsat and MODIS by regression approaches. Our analyses show significant decreases in VIs and ET for both the 20-year and post-pulse 5-year periods. Over the last 20 years, EVI Landsat declined 34% (30% by EVIMODIS) and ETLandsat-EVI declined 38% (27% by ETMODIS-EVI), overall ca. 1.61 mm/day or 476 mm/year drop in ET; using PAM ETLandsat-EVI the drop was from 1130 to 654 mm/year. Over the 5 years since the 2014 pulse flow, EVILandsat declined 20% (13% by EVIMODIS) and ETLandsat-EVI declined 23% (4% by ETMODIS-EVI) with a 0.77 mm/day or a 209 mm/year 5-year drop in ET; using PAM ETLandsat-EVI the drop was from 863 to 654 mm/year. Data and change maps show the pulse flow contributed enough water to slow the rate of loss, but only for the very short-term (1–2 years). These findings are critically important as they suggest further deterioration of biodiversity, wildlife habitat and key ecosystem services due to anthropogenic diversions of water in the U.S. and Mexico and from land clearing, fires and plant-related drought which affect hydrological processes. 相似文献
Debris flows are hazardous phenomena occurring at volcanoes, and monitoring them has proved as challenging as imperative in several cases. The use of seismic instruments to measure and study the physical properties of debris flows has witnessed significant progress in the last years, with the use of improved sensors, innovative methodologies and high-resolution analysis. However, the application of such studies to the practical task of providing early warnings remains limited by the significant amount of infrastructural and technological resources commonly required for their deployment. In Ecuador, debris flows at volcanoes are detected by means of seismic instruments which are usually part of broader monitoring networks, thus requiring calibration to provide quantitative information about the flows and feed early-warning systems. In the present work, a theoretical approach based on the Buckingham Π-theorem is used to determine an expression that linearly correlates the seismic signal produced by a transiting debris flow with its discharge rate, for instruments installed in different substrata and at variable distances from the drainage. The expression is experimentally tested with Acoustic Flow Monitors and Broad-band seismometers installed in the vicinity of drainages at Tungurahua and Cotopaxi volcanoes, where actual debris flows occurred in relation to eruptive activity. The experiments consist in comparing the measured peak amplitude values of the seismic signal envelopes with the estimated peak discharge rates of several events. The results confirm the validity of the theoretical expression with linear correlations observed between the seismic amplitudes and the discharge rates, thus defining calibration expressions that can be generally applied to varied environments and instruments. The seismic instruments calibrated through this methodology can provide instantaneous and reliable predictions of debris flow discharge rates within less than an order of magnitude and only requiring limited data processing and storage. Such level of prediction could help to improve early warning systems based on seismic instruments installed in locations where more developed instrumental arrays are unavailable or unpractical.
We evaluate the relationship between the intensity of remanent magnetization and fO2 in natural and synthetic Mars meteorites. The olivine‐phyric shergottite meteorite Yamato 980459 (Y‐980459) and a sulfur‐free synthetic analog (Y‐98*) of identical major element composition were analyzed to explore the rock magnetic and remanence properties of a basalt crystallized from a primitive melt, and to explore the role of magmatic and alteration environment fO2 on Mars crustal anomalies. The reducing conditions under which Y‐980459 is estimated to have formed (QFM‐2.5; Shearer et al. 2006) were replicated during the synthesis of Y‐98*. Y‐980459 contains pyrrhotite and chromite. Chromite is the only magnetic phase in Y‐98*. The remanence‐carrying capacity of Y‐980459 is comparable to other shergottites that formed in the fO2 range of QFM‐3 to QFM‐1. The remanence‐carrying capacity of these low fO2 basalts is 1–2 orders of magnitude too weak to account for the intense crustal anomalies observed in Mars's southern cratered highlands. Moderately oxidizing conditions of >QFM‐1, which are more commonly observed in nakhlites and Noachian breccias, are key to generating either a primary igneous assemblage or secondary alteration assemblage capable of acquiring an intense remanent magnetization, regardless of the basalt character or thermal history. This suggests that if igneous rocks are responsible for the intensely magnetized crust, these oxidizing conditions must have existed in the magmatic plumbing systems of early Mars or must have existed in the crust during secondary processes that led to acquisition of a chemical remanent magnetization. 相似文献