An integrative physical,mineralogical and ichnological approach to characterize underfilled lake-basins     

Adriana C. Mancuso  Veronica Krapovickas  Cecilia A. Benavente  Claudia A. Marsicano 《Sedimentology》2020,67(6):3088-3118

Lakes are particularly sensitive to environmental fluctuations, which are recorded in their facies and stratigraphy. Ephemeral lakes reveal their sensitivity to palaeoenvironmental changes in the overprinting of the sedimentary features in every single bed. Tetrapod-track taphonomic-modes and ichnological taphonomic-pathways can be used as sensitive indicators of environmental conditions of the track-bearing beds during deposition and imprinting. The Middle Triassic Cerro de las Cabras succession (Cuyana Basin, Argentina) provides an excellent opportunity to these environmental indicators in an underfilled palaeolake. A model of ichnological preservation for underfilled lake systems is proposed and the role of the ichnology record in the sequence stratigraphy analysis is evaluated, based on the integration of tetrapod-track modes, taphonomic-pathways of playa-lake ichnofauna, mineralogy and physical data. Soft-ground suites include those dominated by invertebrate grazing traces and arthropod locomotion traces (Suite 1), and those overprinted by horizontal-vertical dwelling burrows with tetrapod tracks preserved in taphonomic modes B and C (Suite 2). The firm-ground suite (Suite 3) comprises tetrapod-tracks with the best preservation styles (modes A and B) along less abundant invertebrate dwelling and feeding traces as found in Suite 2. Clay mineralogy (dominated by illite with subordinate smectite) suggests low plasticity of the layers, in agreement with low-relief deformation structures observed in tetrapod-track taphonomic-modes. The well-preserved track tetrapod features documented in the Cerro de las Cabras succession, together with the absence of pedogenic disturbance, trampling obliterating the footprints, and/or evidence of strong disturbance by wind, desiccation and/or precipitation, supports short periods of exposure of the imprinted surface particular to this succession. An integrated multiproxy approach is proposed to evaluate the evolutionary interpretation and identification of autogenic versus allogenic controls in underfilled lake-basin histories. The observed aggradational-trend suggests an equilibrium between rates of accommodation change and sediment supply, and that the basin-centre did not experience prolonged sediment-starved conditions.  相似文献   

Plate motions and the viscosity structure of the mantle — Insights from numerical modelling     

Claudia Stein  Ulrich Hansen 《Earth and Planetary Science Letters》2008,272(1-2):29-40

We use sulfur (S) isotope signatures within ancient sediments and a photochemical model of sulfur dioxide (SO₂) photolysis to interpret the evolution of the atmosphere over the first half of Earth's history. A decrease in mass-independent sulfur isotope fractionation has been reported in Archean rocks deposited between ~ 2.7 Ga and ~ 3.2 Ga, and is reinforced by new S isotope data that we report here. This pattern has been interpreted by some as evidence that atmospheric oxygen (O₂) was elevated during this time. In this paper, we argue against that conclusion, and show that it is inconsistent with other geochemical data. In its place, we propose a new model that can explain the sulfur isotope record that can also avoid conflicts with independent constraints on O₂ and account for concurrent glacial deposits. Specifically, we suggest that prior to the rise of O₂ excursions in the sulfur isotope record were modulated by the thickness of an organic haze. This haze would have blocked the lower atmosphere from the UV fluxes responsible for the anomalous sulfur photochemistry and would have caused an anti-greenhouse effect that triggered the glaciations. We used a photochemical model to verify that a haze could have affected the isotopic signal in this manner, and to examine how changes in atmospheric methane (CH₄) and carbon dioxide (CO₂) concentrations could have controlled haze thickness. Finally, we combined the resulting relationships with climate models and sulfur isotope and glacial records to deduce a new evolutionary sequence for Archean climate, surface chemistry, and biology.  相似文献   

Inversion of magnetotelluric data in the presence of strong bathymetry/topography   总被引：1，自引：0，他引：1  

Shenghui Li  John R. Booker  Claudia Aprea 《Geophysical Prospecting》2008,56(2):259-268

We describe an algorithm for inverting magnetotelluric (MT) data in the presence of strong bathymetry or topography. Instead of correcting distortions due to bathymetry or topography we incorporate them directly into the inversion. To achieve a high accuracy in computing MT responses we use finite‐difference approximations that permit sloping discrete boundaries inside model elements. The same approach is applicable to any seafloor electromagnetic calculation and can also be used to incorporate steep topography on land. We test our approach on various topographic features and compare our results to that of a finite element approach. Finally, we present inversion examples that illustrate the effectiveness of our inversion algorithm in recovering true subsurface structures in the presence of strong bathymetry and topography.  相似文献   

The glutathione antioxidant system as a biomarker suite for the assessment of heavy metal exposure and effect in the grey mangrove, Avicennia marina (Forsk.) Vierh   总被引：1，自引：0，他引：1  

Caregnato FF  Koller CE  MacFarlane GR  Moreira JC 《Marine pollution bulletin》2008,56(6):1119-1127

Alterations in the glutathione antioxidant system and lipid peroxidation in Avicennia marina were studied under laboratory and field conditions. The activity of glutathione peroxidase (GPx) was found to respond to Zn exposure, and a significant positive relationship between leaf Zn concentration and GPx activity was observed after 96 h and 8 weeks. Lipid hydroperoxides increased proportionally with increasing leaf Zn concentration after 2 and 8 weeks, while no changes in total glutathione were observed. Induction of GPx at 96 h predicted effects at the individual level at a later time interval (reduced biomass at 8 weeks). Results from the field revealed that increasing leaf metal concentration (Zn, Cu or Pb) produced a proportional increase in GPx activity whereas lipid hydroperoxides and total glutathione were not affected. The utility of GPx as an early warning biomarker is suggested, since GPx activity increases in a dose-dependant fashion in response to accumulated leaf metals, and is predictive of later effects on growth.  相似文献   

Holocene environmental history of thermokarst lakes on Richards Island, Northwest Territories, Canada: Theocamoebians as paleolimnological indicators     

Audrey Dallimore  Claudia J. Schröder-Adams  Scott R. Dallimore 《Journal of Paleolimnology》2000,23(3):261-283

Richards Island, Northwest Territories, Canada, is characterized by thermokarst lakes which record Holocene limnological change. This study is the first report of thecamoebian assemblages and continuous annual lake water temperatures from these Arctic lakes. Ecological environments on Richards Island are influenced by a climatic gradient resulting from the contrasting influences of the cold Beaufort Sea to the north and the warm waters of the Mackenzie Delta to the east and west. This climatic gradient in turn influences modern thecamoebian assemblages, and is an indication of the complexity involved in interpreting past conditions from core material in this area.Population abundance and species diversity of thecamoebian assemblages on Richards Island are not significantly different from those reported from temperate and semi-tropical latitudes. However, certain assemblage characteristics, such as large and coarse agglutinated tests, dominance of assemblages by one or two species and low morphological variation are interpreted to be diagnostic of Arctic conditions. Thecamoebian assemblages in core material from the area indicate that the local paleolimnological conditions may have changed within the last 3 ka, and this is unrecorded in previously reported pollen data.Paleoenvironmental interpretations in a permafrost landscape have to take into account morphological instability of thermokarst lakes, which can be the cause of paleolimnological and consequently faunal change. In this area ecosystem development is clearly related to geomorphology and local climatic effects and is not exclusively controlled by regional climate change.  相似文献   

Using new remote sensing satellites for assessing water quality in a reservoir     

Matias Bonansea  Micaela Ledesma  Claudia Rodriguez  Lucio Pinotti 《水文科学杂志》2019,64(1):34-44

Water quality monitoring could benefit from information derived from the newest generation of medium-resolution Earth observation satellites. The main objective of our study was to assess the suitability of both Landsat 8 and Sentinel-2A satellites for estimating and mapping of Secchi disk transparency (SDT), a common measurement of water clarity, in Cassaffousth Reservoir (Córdoba, Argentina). Ground observations and a dataset of four Landsat 8 and four Sentinel-2A images were used to create and validate models to estimate SDT in the reservoir. The selected algorithms were used to obtain graphic representations of water clarity. Slight differences were found between Landsat 8 and Sentinel-2 estimations. Thus, we demonstrated the suitability of both satellites for estimating and mapping water quality. This study highlights the importance of free and readily available satellite datasets in monitoring water quality, especially in countries where conventional monitoring programmes are either lacking or unsatisfactory.  相似文献   

Bioremediation Management Reduces Mass Discharge at a Chlorinated DNAPL Site          下载免费PDF全文

Brett R. Baldwin  Dora Taggart  Yunzhou Chai  David Wandor  Anita Biernacki  Kerry L. Sublette  John T. Wilson  Claudia Walecka‐Hutchison  Camillo Coladonato  Bryan Goodwin 《Ground Water Monitoring & Remediation》2017,37(2):58-70

Adaptive site management and aggressive bioremediation in the source zone of a complex chlorinated dense nonaqueous phase liquid (DNAPL) site reduced total chlorinated hydrocarbon mass discharge by nearly 80%. Successful anaerobic bioremediation of chlorinated hydrocarbons can be impaired by inadequate concentrations of electron donors, competing electron acceptors, specific inhibitors such as chloroform, and potentially by high contaminant concentrations associated with residual DNAPL. At the study site, the fractured bedrock aquifer was impacted by a mixture of chlorinated solvents and associated daughter products. Concentrations of 1,1,2,2‐tetrachloroethane (1,1,2,2‐TeCA), 1,1,2‐trichloroethane (1,1,2‐TCA), and 1,2‐dichloroethane (1,2‐DCA) were on the order of 100 to 1000 mg/L. Chloroform was present as a co‐contaminant and background sulfate concentrations were approximately 400 mg/L. Following propylene glycol injections, concentrations of organohalide‐respiring bacteria including Dehalococcoides and Dehalogenimonas spp. increased by two to three orders of magnitude across most of the source area. Statistical analysis indicated that reaching volatile fatty acid concentrations greater than 1000 mg/L and depleting sulfate to concentrations less than 50 mg/L were required to achieve a Dehalococcoides concentration greater than the 10⁴ cells/mL recommended for generally effective reductive dechlorination. In a limited area, chloroform concentrations greater than 5 mg/L inhibited growth of Dehalococcoides populations despite the availability of electron donor and otherwise appropriate geochemical conditions. After implementing a groundwater recirculation system targeting the inhibited area, chloroform concentrations decreased permitting significant increases in concentrations of Dehalococcoides and vinyl chloride reductase gene copies.  相似文献   

Hybrid Neoliberalism: Implications for Sustainable Development     

Claudia Baldwin  Graham Marshall  Helen Ross  Jim Cavaye  Janet Stephenson  Lyn Carter 《社会与自然资源》2019,32(5):566-587

Neoliberalism is frequently blamed for challenges in achieving sustainable development; consequently some also question if sustainability is still a useful concept. Neoliberal influence on natural resource management has evolved over the last 30?years to a hybrid form that seeks to compensate for its negative social and environmental externalities. Through review of literature and critical analysis of three case studies of resource development in Australia and New Zealand, we argue that, in spite of modifications under hybrid approaches, neoliberalism still tests achievement of sustainability goals, due to privileging industry and shifting risk and costs to future generations, through inadequate regulation, neglect of public consultation, lack of transparency, and weak impact assessment. We suggest that while neoliberal approaches bring both benefits and disadvantages, sustainability principles must continue to be kept at the forefront of legislation, regulation and management.  相似文献   

Hydrological regimes in different slope environments and implications on rainfall thresholds triggering shallow landslides     

Fusco  Francesco  Bordoni  Massimiliano  Tufano  Rita  Vivaldi  Valerio  Meisina  Claudia  Valentino  Roberto  Bittelli  Marco  De Vita  Pantaleone 《Natural Hazards》2022,114(1):907-939

Natural Hazards - Assessing hazard of rainfall-induced shallow landslides represents a challenge for the risk management of urbanized areas for which the setting up of early warning systems, based...  相似文献   

Climate change mitigation strategies for agriculture: an analysis of nationally determined contributions,biennial reports and biennial update reports     

Susanna Esther Hönle  Claudia Heidecke  Bernhard Osterburg 《Climate Policy》2019,19(6):688-702

The role of agriculture in the context of climate change is a complex issue. On the one hand, concerns about food security highlight the need to prioritize adaptation; on the other hand, the target of the Paris Agreement (keeping global temperature rise well below 2°C) cannot be achieved without a significant decrease in agricultural emissions. Various analyses of nationally determined contributions (NDCs) submitted under the Paris Agreement show how countries intend to prioritize the needs for adaptation and mitigation in the agricultural sector. This paper focuses on 46 countries that contribute 90% of global agricultural emissions and asks how they are addressing the agricultural sector in their climate mitigation policies. It takes into account that conditions and circumstances in countries vary significantly but might also indicate similar patterns. The analysis is based on information provided by countries in their NDCs, as well as their Biennial Reports (BRs) or Biennial Update Reports (BURs) under the UN Framework Convention on Climate Change (UNFCCC). It further includes data on national agricultural emissions. By applying a mixed methods approach, which combines qualitative content analysis and comparative cluster analysis, we find that countries vary in their progress on agriculture and climate mitigation for many different reasons. These reasons include the national perception of the problem, divergent starting points for climate policy, particularities of the agricultural sector and, correspondingly, the availability of cost-effective mitigation technologies.

Key policy insights

• While for many countries the NDCs signify the beginning of their climate policy, UNFCCC biennial reports can be used to learn more about the policies that countries have already implemented.

• Mitigation action in the agricultural sector is emphasized most prominently in cases where co-benefits are possible and production is not impacted negatively.

• Policies and measures in the agricultural sector often do not align with the UNFCCC system of monitoring, reporting and verification (MRV). In addition to improving MRV-systems, it seems equally important to exchange national experiences with implemented measures and policies.

• The Koronivia Joint Work on Agriculture could take into account the problem of different definitions of sector boundaries and thus the importance of different mitigation measures.

  相似文献