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61.
Regional Environmental Change - Plausible scenarios of future land use derived from model projections may differ substantially from what is actually desired by society, and identifying such...  相似文献   
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The human communities and ecosystems of island and coastal southeast Africa face significant and linked ecological threats. Socioecological conditions of concern to communities, governments, nongovernmental organizations, and researchers include declining agricultural productivity, deforestation, introductions of non-native flora and fauna, coastal erosion and sedimentation, damage to marine environments, illegal fishing, overfishing, waste pollution, salinization of freshwater supplies, and rising energy demands, among others. Human–environment challenges are connected to longer, often ignored, histories of social and ecological dynamics in the region. We argue that these challenges are more effectively understood and addressed within a longer-term historical ecology framework. We reviewed cases from Madagascar, coastal Kenya, and the Zanzibar Archipelago of fisheries, deforestation, and management of human waste to encourage increased engagement among historical ecologists, conservation scientists, and policy makers. These case studies demonstrate that by widening the types and time depths of data sets we used to investigate and address current socioecological challenges, our interpretations of their causes and strategies for their mitigation varied significantly.  相似文献   
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This study investigates the strategic antecedents of operational agility in humanitarian logistics. It began by identifying the particular actions to be taken at the strategic level of a humanitarian organisation to support field‐level agility. Next, quantitative data (n=59) were collected on four strategic‐level capabilities (being purposeful, action‐focused, collaborative, and learning‐oriented) and on operational agility (field responsiveness and flexibility). Using a quantitative analysis, the study tested the relationship between organisational capacity building and operational agility and found that the four strategic‐level capabilities are fundamental building blocks of agility. Collectively they account for 52 per cent of the ability of humanitarian logisticians to deal with ongoing changes and disruptions in the field. This study emphasises the need for researchers and practitioners to embrace a broader perspective of agility in humanitarian logistics. In addition, it highlights the inherently strategic nature of agility, the development of which involves focusing simultaneously on multiple drivers.  相似文献   
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Multitracers were used to study water mixing in the Paraíba do Sul River estuary region in August 2007 (dry season) and March 2008 (rainy season) and to evaluate the reach of the river plume in the direction of the open ocean. Two sampling campaigns were carried out, each in a different season. Based on these results, it was possible to conclude that the multitracers used in this study (salinity, Si, Ba and U, as well as the radium isotopes 223Ra, 224Ra, 226Ra and 228Ra) presented satisfactory results toward defining the plume reach and determining the residence time and water-mixing processes in the estuary. A strong correlation was observed between tracers and the distance to the coast. During the low river water discharge period, the riverine water took about 10 days to reach open ocean waters (salinity ∼ 35). During the rainy period this value decreased to 6 days. Based on the radium results, it was possible to calculate diffusion coefficients (Kh) of 23 km2 d−1 and 38 km2 d−1 for 224Ra and 223Ra, respectively, during the dry season (winter). Values of 65 km2 d−1 and 68 km2 d−1 for 223Ra and 224Ra, respectively, were found for the rainy period (summer).  相似文献   
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Polycyclic aromatic hydrocarbons (PAHs) are widespread fused-ring contaminants formed during incomplete combustion of almost all kind of organic materials from both natural and anthropogenic sources. Some PAHs have been shown to be carcinogenic to humans, and a wide range of PAHs are found in wildlife all around the globe including avian species. The purpose of this project was to assess the effects of a standard mixture of 16 PAHs (United States Environmental Protection Agency) on the hepatic fatty acid β-oxidation in chicken embryos (Gallus gallus domesticus) exposed in ovo. The hepatic β-oxidation was measured using a tritium release assay with [9,10-3H]-palmitic acid (16:0) as substrate. Treated groups were divided into groups of 0.05, 0.1, 0.3, 0.5, and 0.8 mg PAHs/kg egg weight. The hepatic β-oxidation was reduced after exposure in ovo to the 16 PAHs mixture compared to control. The mechanisms causing reduced fatty acid oxidation in the present study are unclear, however may be due to deficient membrane structure, the functionality of enzymes controlling the rate of fatty acid entering into the mitochondria, or complex pathways connected to endocrine disruption. To the best of our knowledge, this is the first time a PAH-caused reduction of hepatic β-oxidation of fatty acids in avian embryos has been observed. The implication of this finding on risk assessment of PAH exposure in avian wildlife remains to be determined.  相似文献   
69.
Only a few studies have assessed the joint incorporation of heavy metals into agricultural systems based on the range of agrochemicals used on a specific agricultural crop. This study was conducted to assess the heavy metals input through application of the main agrochemicals used in Brazilian tobacco fields. A total of 56 samples of different batches of 5 fertilizers, 3 substrates, 8 insecticides, 3 fungicides, 2 herbicides, and 1 growth regulator commonly used in the cultivation of tobacco in Brazil’s Southern Region were collected from 3 warehouses located in the States of Rio Grande do Sul, Santa Catarina, and Paraná. The total As, Cd, Co, Cr, Cu, Hg, Fe, Mn, Ni, Pb, and Zn content of the samples was then determined and compared with the regulations of different countries and information found in the available literature. The fertilizers were identified as the primary source of heavy metals among the agrochemicals used. Application of pesticides directly to the shoots of tobacco plants contributed very little to the supply of heavy metals. The agrochemicals used in Brazilian tobacco fields provide lower inputs of the main heavy metals that are nonessential for plants than those registered in the international literature for the majority of crop fields in different regions of the world.  相似文献   
70.
The aim of this work was to determine the concentrations and isotopic compositions of plutonium and uranium in environmental samples for safeguards purposes. An analytical method was developed with a plutonium and uranium separation procedure based on extraction chromatography (using 2 mL TEVA and UTEVA columns) and detection with a quadrupole ICP-MS applying an ultra-sonic nebulizer coupled with a membrane desolvation system. Starting from blank swipes, the background equivalent concentration (BEC) was 8 fg for 239Pu and 1 ng 238U. The method was successfully applied to certified reference materials as well as to round robin samples obtained in the framework of the inter-laboratory exercise program, promoted by the Brazilian–Argentine Agency for Accounting and Control of Nuclear Materials (ABACC), together with the US Department of Energy (USDOE). After the introduction of an additional ion-exchange separation step, the methodology was applied to the IAEA-384 sediment reference sample with precise and accurate total plutonium and uranium, 240Pu/239Pu, 241Pu/239Pu, 234U/238U and 235U/238U atomic ratio results.  相似文献   
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