Chemical contamination in southwest Puerto Rico: an assessment of trace and major elements in nearshore sediments     

Pait AS  Whitall DR  Jeffrey CF  Caldow C  Mason AL  Lauenstein GG  Christensen JD 《Marine pollution bulletin》2008,56(11):1953-1956

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The coral reef crisis: The critical importance of <350 ppm CO₂     

J.E.N. Veron  O. Hoegh-Guldberg  C.R.C. Sheppard  M.G. Stafford-Smith 《Marine pollution bulletin》2009,58(10):1428-1436

Temperature-induced mass coral bleaching causing mortality on a wide geographic scale started when atmospheric CO₂ levels exceeded ∼320 ppm. When CO₂ levels reached ∼340 ppm, sporadic but highly destructive mass bleaching occurred in most reefs world-wide, often associated with El Niño events. Recovery was dependent on the vulnerability of individual reef areas and on the reef’s previous history and resilience. At today’s level of ∼387 ppm, allowing a lag-time of 10 years for sea temperatures to respond, most reefs world-wide are committed to an irreversible decline. Mass bleaching will in future become annual, departing from the 4 to 7 years return-time of El Niño events. Bleaching will be exacerbated by the effects of degraded water-quality and increased severe weather events. In addition, the progressive onset of ocean acidification will cause reduction of coral growth and retardation of the growth of high magnesium calcite-secreting coralline algae. If CO₂ levels are allowed to reach 450 ppm (due to occur by 2030-2040 at the current rates), reefs will be in rapid and terminal decline world-wide from multiple synergies arising from mass bleaching, ocean acidification, and other environmental impacts. Damage to shallow reef communities will become extensive with consequent reduction of biodiversity followed by extinctions. Reefs will cease to be large-scale nursery grounds for fish and will cease to have most of their current value to humanity. There will be knock-on effects to ecosystems associated with reefs, and to other pelagic and benthic ecosystems. Should CO₂ levels reach 600 ppm reefs will be eroding geological structures with populations of surviving biota restricted to refuges. Domino effects will follow, affecting many other marine ecosystems. This is likely to have been the path of great mass extinctions of the past, adding to the case that anthropogenic CO₂ emissions could trigger the Earth’s sixth mass extinction.  相似文献   

饱和膨润土及其与砂混合物的压缩变形特性   总被引：1，自引：0，他引：1  

孙文静  孙德安  孟德林 《岩土力学》2009,30(11):3249-3255

对用不同制样方法得到的饱和膨润土及其与砂混合物进行了压缩试验。试验结果表明,饱和膨润土的压缩曲线呈双线性,不同于普通黏土的压缩曲线。压缩试验中量测了侧向应力,由此得到的饱和膨润土的静止侧向压力系数值较一般黏土的数值要大。对膨润土与砂混合物的击实样进行了由非饱和到饱和状态的浸水试验,并得出试验过程中侧向应力的变化规律。由于浸水饱和的试样和抽真空饱和的试样在较高压力时压缩曲线趋于一致,可采用快速抽真空饱和的方法进行试验研究,以缩短非饱和混合物击实样浸水饱和所需时间。引入骨架孔隙比的概念,用来判断膨润土与砂混合物中砂骨架是否形成,得出影响混合物压缩特性的决定因素。  相似文献   

颗粒体系中的骨架及力链网络   总被引：4，自引：0，他引：4  

孙其诚  辛海丽  刘建国  金峰 《岩土力学》2009,30(Z1):83-87

颗粒物质是大量离散的固体颗粒相互作用而组成的复杂体系,具有非连续和接触耗散等基本特征,其物理机制研究是近20年科学前沿之一。砂土就是典型的颗粒物质,土体中的有效应力是作用在土体骨架上的平均应力,土体变形主要来源于骨架上的颗粒位置,但对土体骨架并没有一个清晰的物理描述。近期颗粒物质力学研究认为,体系中颗粒相互接触形成的网络结构是外荷载传递路径的物理基础,可能就是土力学所指的骨架。同时还发现,较大的力通常沿着准直线的路径传递,人们常把传递较大力、与该准直线路径对应的若干颗粒组成的链状结构,称为强力链;弱力链则传递较小力。力链结构及其演变规律的描述是颗粒物质研究的核心之一。以单轴侧限压缩数值模拟为例,对比说明了土体颗粒骨架与力链结构的关系,明确提出强力链网络决定颗粒体系的宏观力学行为。  相似文献   

动力作用下砂土的残余体变及其时域连续模型   总被引：1，自引：0，他引：1  

陈文化  门福录 《岩土力学》2003,24(6):947-951

通过对砂土动力剪切荷载作用过程中的土骨架的弹性和塑性分析,研究了土骨架接触面部分可能发生的弹性恢复和永久变形以及破碎引起的最剧烈的塑性变形;并且,提出了可以通过液化前后颗粒粒径的质量百分含量的对比试验,来验证破碎模型的合理性;为进行砂土动力非线性变形和液化的数值模拟,结合砂土的剪切非线性的本构,总结了更为简化的时域连续的函数经验公式,使得在时域内进行土壤动力特性和动力非线性反应分析,以及用剪胀性理论解释动力液化和变形问题易于进行。  相似文献   

Evaluating the influence of candidate terrestrial protected areas on coral reef condition in Fiji     

《Marine Policy》2014

In any given region, there are multiple options for terrestrial protected area networks that achieve goals for conservation of terrestrial biodiversity and ecosystem values. When deciding on the location of terrestrial protected areas, planners typically focus only on terrestrial conservation goals, ignoring potential linked benefits to marine ecosystems. These benefits include maintenance of downstream water quality, as forest protection can prevent changes in amount and composition of river runoff that negatively impacts coral reefs. This study aims to determine the benefit of different terrestrial reserve networks to the condition of coral reefs adjacent to the main islands of Fiji to support the work of Fiji's Protected Area Committee in expanding the national protected area estate through integrated land–sea planning. Options for terrestrial protected area networks were designed using six approaches, where the primary objective of each approach was to either achieve terrestrial conservation goals (e.g., represent 40% of each vegetation type) or maximize benefits to coral reefs by minimizing potential for land-based runoff. When achieving terrestrial conservation goals was the primary objective, the potential benefits to coral reef condition were 7.7–10.4% greater than benefits from the existing network of protected areas. When benefiting reefs was the primary objective, benefits to coral reefs were 1.1–2.8 times greater per unit area than networks designed to only achieve terrestrial conservation goals, but 31–44% of the terrestrial conservation goals were not achieved. These results are already being used by Fiji's Protected Area Committee to modify the boundaries of existing priority places to deliver outcomes that better meet terrestrial conservation goals while offering greater benefits to coral reef condition through prevention of run-off.  相似文献   

Relationship of Stakeholders in Protected Areas and Tourism Ecological Compensation: A Case Study of Sanya Coral Reef National Nature Reserve in China     

CHEN Haiying  HE Linsi  LI Peng  ZENG Xiaohong  YOU Changjiang 《资源与生态学报(英文版)》2018,9(2):164-173

The first step to defining the rights, responsibilities and interests of stakeholders and constructing a compensation mechanism is to identify the stakeholders and clarify their mutual relationships. Nature reserves are complex ecosystems involving nature, the economy and society. There exists a conflict between the public welfare benefits of ecological conservation and the private gains to be realized from social and economic development. There also exist in a nature reserve complex relationships among stakeholders, involving the utilization of ecological resources, ecological conservation and ecological-economic interests. The introduction of tourism brings substantial changes to the existing stakeholder benefit structure in a nature reserve. The implementation of tourism ecological compensation (tourism payment for ecological service) is a process for redefining the distribution of rights, responsibilities and profits among stakeholders and it is also an essential way to balance the interests of the stakeholders. This paper uses a case study of Sanya Coral Reef National Nature Reserve in China to examine the characteristics of stakeholders and analyze their interests. According to the method for defining basic attributes proposed by Mitchel and other scholars, in cases of tourism ecological compensation, stakeholders can be classified as definitive stakeholders, expectant stakeholders and latent stakeholders. This paper applies these classifications and then analyzes the relationships between the rights and responsibilities of these stakeholders and how these change after the implementation of compensation. Additionally, based on the impact compensation has on different stakeholders, changes in the relationships can be analyzed and the structure of the stakeholders can be modelled. This case study of the Sanya Coral Reef National Nature Reserve illustrates the operationalization of a new mechanism for tourism ecological compensation. The paper illustrates a method for coordinating the relationships among the stakeholders involved with this national-level nature reserve.  相似文献   

水文等值线图特征要素提取研究     

杨海坤  刘九夫  沈冰 《水文》2008,28(1):21-24

阐述了特征要素对水文等值线图网格化的重要性.通过比较分析两种经典的数学形态学骨架提取算法的应用效果,认为最大数字圆盘定义的骨架更接近于水文等值线图的特征要素分布.针对由最大数字圆盘算法得到的骨架线存在的一些不足,对其作消噪、粘合和细化等进一步改进处理.对相关结构元素的形状和大小给出建议.  相似文献   

珊瑚骨骼生长研究评述     

张江勇  余克服 《地质论评》2008,54(3):362-372

珊瑚骨骼生长有年、月、日周期,能够当作古生物钟来记录地质历史。块状珊瑚骨骼密度条带年周期的发现对后来的珊瑚古气候研究产生了深远的影响,随后又发现世界各热带海域的珊瑚存在多种多样的骨骼密度变化模式,起先常从珊瑚的生长环境中寻找骨骼密度变化的控制因素,但是没有成功,从80年代后期,部分学者试图从珊瑚骨骼构架本身出发、综合考虑环境因素和骨骼密度条带之间的关系来探求骨骼密度变化的机理,并提出了一个可以解释大多数块状珊瑚骨骼密度条带变化模式的骨骼生长模型。块状珊瑚软体层厚度是一个十分重要但至今仍没引起足够重视的珊瑚生长参数,它相对于骨骼线性生长率的变化影响着骨骼密度变化模式。骨骼钙化作用和虫黄藻光合作用的相互关系还存有争议,珊瑚骨骼钙化机理仍在探索中。  相似文献   

Characterization of an island aquifer from tidal response     

Pallavi Banerjee  Deepak Sarwade  V. S. Singh 《Environmental Geology》2008,55(4):901-906

Growing demand for potable water for various needs has lead to indiscriminate exploitation of groundwater resources, particularly, in the terrain where surface water resources are negligible. One such area is an island where groundwater is the only source of fresh water. Groundwater is the prime source of fresh water on most of the atolls in the world. Groundwater on these islands is in the form of thin fragile floating lens and is often vulnerable to overexploitation, draught, tidal waves, tsunami and cyclone resulting in seawater ingress. Sustainable development of this meager source of fresh groundwater for a longer time becomes a more difficult task on small atolls with a large population depending on this vital resource. To develop a sustainable management scheme and identify the vulnerable part of aquifer, characterization of the aquifer system on islands is imperative. Groundwater on an atoll is extremely vulnerable to seawater mixing through natural as well as human activities. One such natural process is the tides of the ocean. The response of sea tide to the water table on the island offers valuable data as well as cost-effective means to characterize an aquifer system. Such characterization is vital for the management of groundwater resources on an atoll. The obtained results have compared well with the parameters obtained through a conventional pumping test. Therefore, the use of tidal response to the water table, which can easily be recorded, provides a rapid and cost-effective means to characterization of the aquifer system on the island.  相似文献