Was southern Sweden ice free at 19–25 ka, or were the post LGM glacifluvial sediments incompletely bleached?     

Helena Alexanderson  Andrew S. Murray 《Quaternary Geochronology》2007,2(1-4):229-236

Glacifluvial deposits along an ice-marginal zone in Småland, southern Sweden, have been dated using post-IR blue OSL. To test for incomplete bleaching, we adopted two strategies: analysis of modern analogues and small-aliquot dose distributions. Samples of modern fluvial sediments show no significant incomplete bleaching; they yield equivalent doses of only 0.5–2 Gy (0.25–4% of our glacifluvial sediment doses). Small-aliquot dose distributions do not provide any evidence for incomplete bleaching.

The sediments are believed to have been deposited during deglaciation and appear to fall into two age groups: 19–25 ka (mainly sandur sediments) and 33–73 ka (mainly deltaic sediments). Compared to the expected ages (13–15 ka), even the younger glacifluvial OSL ages appear up to 10 000 years (25 Gy) too old. The ages are nevertheless stratigraphically consistent and correspond between sites; we deduce that the 19–25 ka ages are true deposition ages. For glacifluvial sedimentation to take place on the South Swedish Upland at this time either a very early deglaciation is required, or alternatively ice-free conditions just prior to the LGM. The deltaic sediments (33–73 ka) were most likely not significantly bleached during deposition and thus they date events prior to the latest ice advance.  相似文献   

Catchment scale hydrology of an irrigated cropping system under soil conservation practices          下载免费PDF全文

Patricio Cid  Helena Gómez‐Macpherson  Hakim Boulal  Luciano Mateos 《水文研究》2016,30(24):4593-4608

Soil erosion by water is a pressing environmental problem caused and suffered by agriculture in Mediterranean environments. Soil conservation practices can contribute to alleviating this problem. The aim of this study is to gain more profound knowledge of the effects of conservation practices on soil losses by linking crop management and soil status to runoff and sediment losses measured at the outlet of a catchment during seven years. The catchment has 27.42 ha and is located in a commercial farm in southern Spain, where a package of soil conservation practices is an essential component of the farming system. The catchment is devoted to irrigated annual crops with maize–cotton–wheat as the primary rotation. Mean annual rainfall‐induced runoff coefficient was 0.14 and mean annual soil loss was 2.4 Mg ha^?1 y^?1. Irrigation contributed to 40% of the crop water supply, but the amount of runoff and sediment yield that it generated was negligible. A Principal Components Analysis showed that total soil loss is determined by the magnitude of the event (rainfall and runoff depths, duration) and by factors related to the aggressiveness of the events (rainfall intensity and preceding soil moisture). A third component showed the importance of crop coverage to reduce sediment losses. Cover crops grown during autumn and early winter and crop residues protecting the soil surface enhanced soil conservation notably. The role of irrigation to facilitate growing cover crops in Mediterranean environments is discussed. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Integrating GRASS GIS and Jupyter Notebooks to facilitate advanced geospatial modeling education     

Caitlin Haedrich  Vaclav Petras  Anna Petrasova  Stefan Blumentrath  Helena Mitasova 《Transactions in GIS》2023,27(3):686-702

Open education materials are critical for the advancement of open science and the development of open-source software. These accessible and transparent materials provide an important pathway for sharing both standard geospatial analysis workflows and advanced research methods. Computational notebooks allow users to share live code with in-line visualizations and narrative text, making them a powerful interactive teaching tool for geospatial analytics. Specifically, Jupyter Notebooks are quickly becoming a standard format in open education. In this article, we introduce a new GRASS GIS package, grass.jupyter , that enhances the existing GRASS Python API to allow Jupyter Notebook users to easily manage and visualize GRASS data including spatiotemporal datasets. While there are many Python-based geospatial libraries available for use in Jupyter Notebooks, GRASS GIS has extensive geospatial functionality including support for multi-temporal analysis and dynamic simulations, making it a powerful teaching tool for advanced geospatial analytics. We discuss the development of grass.jupyter and demonstrate how the package facilitates teaching open-source geospatial modeling with a collection of Jupyter Notebooks designed for a graduate-level geospatial modeling course. The open education notebooks feature spatiotemporal data visualizations, hydrologic modeling, and spread simulations such as the spread of invasive species and urban growth.  相似文献   

Relative risk assessment of cruise ships biosolids disposal alternatives   总被引：1，自引：0，他引：1  

Avellaneda PM  Englehardt JD  Olascoaga J  Babcock EA  Brand L  Lirman D  Rogge WF  Solo-Gabriele H  Tchobanoglous G 《Marine pollution bulletin》2011,62(10):2157-2169

A relative risk assessment of biosolids disposal alternatives for cruise ships is presented in this paper. The area of study encompasses islands and marine waters of the Caribbean Sea. The objective was to evaluate relative human health and ecological risks of (a) dewatering/incineration, (b) landing the solids for disposal, considering that in some countries land-disposed solids might be discharged in the near-shore environment untreated, and (c) deep ocean disposal. Input to the Bayesian assessment consisted of professional judgment based on available literature and modeling information, data on constituent concentrations in cruise ship biosolids, and simulations of constituent concentrations in Caribbean waters assuming ocean disposal. Results indicate that human health and ecological risks associated with land disposal and shallow ocean disposal are higher than those of the deep ocean disposal and incineration. For incineration, predicted ecological impacts were lower relative to deep ocean disposal before considering potential impacts of carbon emissions.  相似文献   

Ammonium,nitrate and phytoplankton interactions in a freshwater tidal estuarine zone: potential effects of cultural eutrophication   总被引：2，自引：0，他引：2  

Rita B. Domingues  Ana B. Barbosa  Ulrich Sommer  Helena M. Galvão 《Aquatic Sciences - Research Across Boundaries》2011,73(3):331-343

Nitrate and ammonium are the most important nitrogen sources for phytoplankton growth. Differential utilization of inorganic nitrogenous compounds by phytoplankton has been observed and may have significant impacts on primary productivity at local scales. We used enrichment experiments with natural phytoplankton populations from the freshwater tidal zone of the Guadiana estuary, a coastal ecosystem increasingly subjected to anthropogenic influences, to study the effects of nitrate and ammonium on N-consumption and phytoplankton growth. In addition, we used combined additions of nitrate and ammonium to understand the inhibitory effect of ammonium over nitrate uptake. Ammonium concentrations in the freshwater tidal reaches of the Guadiana estuary throughout the sampling period were too low to exert an inhibitory effect on nitrate uptake or a toxic effect on phytoplankton growth. Nitrate was clearly the main nitrogen source for phytoplankton at the study site. Overall, nitrate seemed to become limiting at concentrations lower than 20 μM and N-limitation was particularly significant during summer. A trend of decreasing nitrate uptake with increasing ammonium concentrations and uptake suggested an overall preference for ammonium. However, preference for ammonium was group-specific, and it was observed mainly in green algae and cyanobacteria. In fact, cyanobacteria relied only on ammonium as their N-source. On the contrary, diatoms preferred nitrate, and did not respond to ammonium additions. The increasing eutrophication in the Guadiana estuary and particularly increased inputs of nitrogen as ammonium due to urban waste effluents may result in a shift in phytoplankton community composition, towards a dominance of cyanobacteria and green algae.  相似文献   

Corrigendum to ‘Pathogenic fungi: An unacknowledged risk at coastal resorts? New insights on microbiological sand quality in Portugal’ [Mar. Pollut. Bull. 62 (2011) 1506–1511]     

Raquel Sabino  Cristina Veríssimo  Maria Ana Cunha  Bela Wergikoski  Filipa C. Ferreira  Raquel Rodrigues  Helena Parada  Leonor Falcão  Laura Rosado  Catarina Pinheiro  Eleonora Paixão  João Brandão 《Marine pollution bulletin》2011,62(12):2880

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GM trees on trial in a field: Reductionism, risks and intractable biological objects     

Helena Valve 《Geoforum》2011,42(2):222-230

Identification of GM plants with their internal molecular-genetic qualities serves transformation of living organisms into identifiable commodities and objects of regulation. From molecular reductionist assumptions it also follows that scientific research is to be based on experiments that allow analysis of genetic influence in isolation. In this paper, I analyse molecular reductionism ‘in action’ by means of an ethnographic case study, focusing on the practices and transformations through which a field trial of transgenic trees created understanding of the risks or risklessness of the trees. The results show how the mobilisation of the field trial design, choosing of key analytical scales and formation of the research team stabilised the paths that experimentation was to follow. The scientists took the emerging inconsistencies and surprises calmly, indicating that unexpected events are an essential part of a scientific process. However, surprises could matter only in relation to the testing arrangements. Therefore, what could become visible and what could make a difference for the constitution of risk/risklessness were the fluctuations that the particular analytical assemblages defined as significant from the outset. Meanwhile, it was impossible to treat the trees and the field ecosystem as mutually constitutive. Nevertheless, there is no reason to think of knowledge production concerning transgenic organisms in deterministic terms. First, scientists are bound to be complexly engaged with the ecosystems that they are supposed to sort out. Second, consideration of the public lessons of experiments may elicit problems and limitations of molecular reductionism.  相似文献   

Mercury, copper and zinc contamination in soils and fluvial sediments from an abandoned gold mining area in southern Minas Gerais State, Brazil     

Ricardo Cesar  Silvia Egler  Helena Polivanov  Zuleica Castilhos  Ana Paula Rodrigues 《Environmental Earth Sciences》2011,64(1):211-222

Mercury, zinc and copper contamination was evaluated in soils and fluvial sediments from an abandoned gold mining site at Descoberto Municipality (southern Minas Gerais State, Brazil). Metals bioavailability and potential mobility were studied through physical, chemical and mineralogical characterization, geoaccumulation indexes calculations, mercury speciation and determination of potentially bioavailable contents of zinc and copper. Values of pH were in the neutral range, while organic matter concentrations were very low. Mineralogical characterization, in the total samples, indicated the presence of quartz, kaolinite and gibbsite for all samples. Total mercury, zinc and cooper concentrations were higher than the limits recommended by Brazilian documents. Geoaccumulations indexes revealed that most of the sediment samples were low to moderately polluted by zinc and copper, while just one sample was very strongly polluted by mercury. Mercury speciation revealed the predominance of the elementary form for all samples, and low concentrations for exchangeable, strongly bound and residual fractions. Zinc and copper behavior was strongly controlled by iron and aluminum concentrations, while their bioavailable contents were very low in comparison with the total concentrations.  相似文献   

Light as a driver of phytoplankton growth and production in the freshwater tidal zone of a turbid estuary   总被引：2，自引：0，他引：2  

Rita B. Domingues  Tnia P. Anselmo  Ana B. Barbosa  Ulrich Sommer  Helena M. Galvo 《Estuarine, Coastal and Shelf Science》2011,91(4):282

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Ecosystem-based marine spatial management: Review of concepts, policies, tools, and critical issues   总被引：1，自引：0，他引：1  

Stelios Katsanevakis  Vanessa Stelzenmüller  Andy South  Thomas Kirk Sørensen  Peter J.S. Jones  Sandy Kerr  Fabio Badalamenti  Christos Anagnostou  Patricia Breen  Guillem Chust  Giovanni D’Anna  Mike Duijn  Tatiana Filatova  Fabio Fiorentino  Helena Hulsman  Kate Johnson  Aristomenis P. Karageorgis  Ingrid Kröncke  Simone Mirto  Carlo Pipitone  Susan Portelli  Wanfei Qiu  Henning Reiss  Dimitris Sakellariou  Maria Salomidi  Luc van Hoof  Vassiliki Vassilopoulou  Tomás Vega Fernández  Sandra Vöge  Anke Weber  Argyro Zenetos  Remment ter Hofstede 《Ocean & Coastal Management》2011,54(11):807-820

Conventional sectoral management and piecemeal governance are considered less and less appropriate in pursuit of sustainable development. Ecosystem based marine spatial management (EB-MSM) is an approach that recognizes the full array of interactions within an ecosystem, including human uses, rather than considering single issues, species, or ecosystem services in isolation. Marine spatial planning and ocean zoning are emerging concepts that can support EB-MSM. EB-MSM is driven by high-level goals that managers aim to achieve through the implementation of measures. High-level goals and objectives need to be translated into more operational objectives before specific targets, limits and measures can be elaborated.Monitoring, evaluation and adaptation are necessary to ensure that marine management measures are both effective and efficient. Solid monitoring frameworks are the foundation of adaptive management, as they provide the necessary information to evaluate performance and the effectiveness of management actions. Marine protected areas (MPAs) - possibly set up in networks - constitute a key component in EB-MSM policies and practises and have been applied as a cornerstone in conservation of marine biodiversity, management of fish populations, development of coastal tourism, etc. Moreover, MPA experiences have provided methods and concepts (such as zoning) to a wider EB-MSM context. The assignment of values to biophysical features of the marine environment allows the direct assessment of related management choices and may assist EB-MSM.A range of monetary valuation techniques have been proposed to reduce attributes of goods and services to a single metric. However, in the marine environment such an approach is often over simplistic, and thus less reductive techniques may be necessary. Rather than producing a single metric, the results of non-monetary assessments guide policy allowing weight to be given as necessary to potential areas of conflict and consensus.Strategies to take into account climate change effects and geohazard risks in EB-MSM have been applied or proposed worldwide. EB-MSM regimes must be alert to such risks and flexible to account for changes.  相似文献