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1997年在爱尔兰共和国进行了一项湖泊调查活动,本活动是确定并则绘临界负载的一个国家项目的一部分内容.共选取了200个湖泊作为调查的对象,约占湖泊总数的3.3‰.这个国家中的多数湖泊位于沿海岸带边缘的偏僻、高海拔、对酸具有敏感性的地区.在湖泊化学中来自海洋的物质的输入占据了主导地位.由于在大部分集水区中存在有机土壤,约有一半的湖泊中溶解有机碳(DOC)的含量大于5mg/L.在一半的湖泊中,非海洋硫酸盐的浓度处于背景水平上(<20μeq/L).在7‰的抽查湖泊(13个湖泊)中发现临界负载超量.但由于海盐和有机酸之间的相互干扰,对临界负载的计算仍存在着不稳定性.在这种情况下如果进行精确的估计,就需要借助于长期的湖泊与沉积化学.  相似文献   
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The effects of acute and subchronic aqueous hydrocarbon exposures in the ppb range (0.2-127microg/L total PAH) on the immune system in Pacific herring (Clupea pallasi) were examined through specific immunocompetency assays and a host resistance model using Listonella anguillarum. Short-term hydrocarbon exposure at the highest concentration significantly enhanced respiratory burst activity (RBA) in macrophages and decreased plasma lysozyme concentrations, however, subchronic exposure (4-57d) reduced RBA. Fish in the high exposure group were also less susceptible to the pathogen L. anguillarum following acute hydrocarbon exposure; however, this group was the most susceptible following subchronic exposures. These results are explained by a measured transient physiological stress response and long-term effects on ionoregulation. This study illustrates that hydrocarbon-elicited effects are dynamic and that toxic outcomes with respect to the teleost immune system depend on chemical concentrations and composition, exposure durations and the specific pathogen challenge.  相似文献   
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The use of lead poses significant hazardous occupational exposure to workers in the electronics industry, and also causes environmental challenges at the end of product life. For the past decade, there has been a global effort in the electronics industry to initiate a move towards using lead-free materials for the production of printed circuit boards. However, there are technical and economic challenges, such as long term reliability and rework capability, that remain to hinder the universal implementation of lead-free materials. As a result, many electronics products are still currently manufactured and assembled using materials containing lead.The costs for investigating and evaluating the various lead-free electronics materials and manufacturing processes can be cost prohibitive for an individual company to undertake alone. Consequently, the New England Lead-free Electronics Consortium was formed as a collaborative effort of New England companies spanning the electronics supply chain to help move the industry towards lead-free electronics. The Consortium is a working collaboration of industry, government, and academia. For the past several years, the Consortium has conducted research and testing for using various lead-free materials for the manufacture of printed circuit boards. The Consortium has been successful in identifying lead-free materials and processes to address the challenges of assembly and rework. The Consortium is currently conducting research to address the long-term reliability challenge of lead-free electronics.  相似文献   
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Semi-arid Mediterranean regions are highly susceptible to desertification processes which can reduce the benefits that people obtain from healthy ecosystems and thus threaten human wellbeing. The European Union Biodiversity Strategy to 2020 recognizes the need to incorporate ecosystem services into land-use management, conservation, and restoration actions. The inclusion of ecosystem services into restoration actions and plans is an emerging area of research, and there are few documented approaches and guidelines on how to undertake such an exercise. This paper responds to this need, and we demonstrate an approach for identifying both key ecosystem services provisioning areas and the spatial relationship between ecological processes and services. A degraded semi-arid Mediterranean river basin in north east Spain was used as a case study area. We show that the quantification and mapping of services are the first step required for both optimizing and targeting of specific local areas for restoration. Additionally, we provide guidelines for restoration planning at a watershed scale; establishing priorities for improving the delivery of ecosystem services at this scale; and prioritizing the sub-watersheds for restoration based on their potential for delivering a combination of key ecosystem services for the entire basin.  相似文献   
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This paper concerns the effects on biodiversity of depletion of the South African abalone Haliotis midae, which is a long-lived species with a large corrugated shell that provides a habitat for diverse benthic organisms. We compared community structure on H. midae shells with that on adjacent rock at three sites (Cape Point and Danger Point sites A and B) and at two different times of the year at one of these sites. Shells of H. midae consistently supported communities that were distinctly different from those on rock. In particular, three species of non-geniculate (encrusting) corallines, Titanoderma polycephalum, Mesophyllum engelhartii and Spongites discoideus, were all found either exclusively or predominantly on shells, whereas another non-geniculate coralline, Heydrichia woelkerlingii, occurred almost exclusively on adjacent rock. The primary rocky substratum, however, supported a higher number of species than abalone shells. Possible reasons for the differences between the two substrata include the relative age, microtopography and hardness of the substrata; the abundance of grazers on them; and the relative age of different zones of the abalone shell, which support communities at different stages of succession. Diversity on shells was lowest in zones that were either very young or very old, in keeping with the intermediate disturbance hypothesis. The distinctiveness of shell epibiota will increase β diversity despite having a lower α diversity than that of adjacent rock. Decimation of H. midae by overfishing therefore has implications for biodiversity conservation.  相似文献   
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Abandoning fossil fuels and increasingly relying on low-density, land-intensive renewable energy will increase demand for land, affecting current global and regional rural–urban relationships. Over the past two decades, rural–urban relationships all over the world have witnessed unprecedented changes that have rendered their boundaries blurred and have lead to the emergence of “new ruralities.” In this paper, we analyze the current profiles of electricity generation and consumption in relation to sociodemographic variables related to the use of time and land across the territory of Catalonia, Spain. Through a clustering procedure based on multivariate statistical analysis, we found that electricity consumption is related to functional specialization in the roles undertaken by different types of municipalities in the urban system. Municipality types have distinctive metabolic profiles in different sectors depending on their industrial, services or residential role. Villages’ metabolism is influenced by urban sprawl and industrial specialization, reflecting current “new ruralities.” Segregation between work activity and residence increases both overall electricity consumption and its rate (per hour) and density (per hectare) of dissipation. A sustainable spatial organization of societal activities without the use of fossil fuels or nuclear energy would require huge structural and sociodemographic changes to reduce energy demand and adapt it to regionally available renewable energy.  相似文献   
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