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971.
We present new palynological information from the anoxic Cariaco Basin, off Venezuela, that provides insight into the response of northernmost South American vegetation to rapid climate changes between 68 and 28 ka, specifically during North Atlantic Heinrich events (HEs) and Dansgaard/Oeschger cycles. We defined three different vegetation modes: (1) an interstadial mode characterized by the highest pollen concentration and the maximum extension of semi-deciduous and evergreen forests; (2) a stadial mode characterized by increases of salt marshes, herbs, and montane forests; and (3) a Heinrich event mode characterized by the lowest pollen concentrations, abrupt increases of salt marshes, and decreased forest abundance. Similarly, indices of C4/C3 plants show increases during stadials with clear peaks during the onset of HEs, though grasslands did not become dominant during these periods. We alternatively propose that these expansions of C4 plants are associated with the expansion of coastal salt marshes. Our vegetation record suggests the prevalence of humid conditions during interstadials, dry and cold conditions during stadials, and dry and cold conditions together with changes in sea level during HEs. This new palynological evidence supports previous interpretations that main environmental changes in northernmost South America were driven by latitudinal displacements of the Intertropical Convergence Zone and sea-level changes.  相似文献   
972.
以煤与海相泥岩的块状样品为研究对象进行多升温速率下的排烃模拟实验,借助生烃动力学方法处理实验模拟结果,对煤与海相泥岩的残留烃特征进行了研究。结果表明:海相泥岩残留烃在Ro为1.0%时达到高峰,然后逐渐降低,而煤中残留烃在Ro为1.0%时达到高峰后便基本上保持稳定。煤吸附能力比海相泥岩的强,其残留烃量也比海相泥岩大。成熟作用对于煤及海相泥岩残留烃都有很大的影响。高过成熟阶段海相地层中烃类构成以油藏或输导层中原油裂解气为主,源岩中的残余液态烃也有一定的贡献,而煤在排烃结束以后煤中分散液态烃对裂解气的贡献更大些。煤中残留烃主要是前期形成的烃类由于排烃效率不高而聚集起来的,而海相残留烃基本上随着残余生烃潜力的降低而降低,这一方面说明海相残留烃受生烃作用的影响,另一方面也受排烃效率的影响。模拟样品中的残留烃及残余生烃潜力均可以与自然样品对比,表明了该方法的实用性。  相似文献   
973.
川东北天然气单体烃氢同位素组成特征   总被引:1,自引:0,他引:1  
采用气-水平衡法及同位素分馏平衡方程技术标定工作标准气,测定样品的氢同位素比值,使误差控制在5‰以内。采取川东北、鄂西和川西三个地区的天然气样品,分别测定它们的单体烃氢同位素比值。分析表明,川东北普光气田海相成因天然气甲烷氢同位素δD平均值为-126‰(SWOM),比新疆塔河油田海相环境生成的天然气甲烷氢同位素δD平均值-164‰重约40‰。对比研究认为,这与其共存地层水的δD值密切相关,也与这些天然气的成熟度有直接关系。  相似文献   
974.
曾庆存  程雪玲  吴琳 《大气科学》2018,42(3):448-462
对我们在南海海域建立的大气边界层观测站的资料进行分析表明,在冷涌和热带气旋(包括强台风)过境的大风期间,在边界层底层10 min平均的水平风速u基本不随高度而变,甚至大都伴随有明显的上升气流w。而且风场脉动中含有强相干性的阵风扰动( v g,频率位于1/60~1/600 Hz频段),以及近于随机性的高频湍流脉动( v t,频率大于1/60 Hz),它们的特性以及w都可以很好地用水平风速u来参数化表示。取实测的(u,w)和脉动 v '= v g+ v t,或取实测的u与参数化的 v g、 v t和w,应用拉格朗日随机模式作数值模拟,结果表明:由破头浪发射出来的浪花和飞沫水滴(半径rp为10~500 μm)有相当大的一部分可以飞离大气底层而进入100 m高以上的大气中,继而对进入大气中的海盐气溶胶通量有重要贡献,不可以被忽略。在水滴的垂直传输过程中,阵风扰动起了极重要的作用,而在w>0且较显著时w更起重要作用。我们对上扬率(可上升至100 m以上高度的水滴数与由海面发射出的水滴数之比)作出了初步的参数化公式,有很高的精度,主要的参量是无量纲量u2/(rqg),其中rp和g分别是水滴半径和重力加速度。  相似文献   
975.
海陆相蒸发岩硫同位素值变化和地球化学应用   总被引:2,自引:1,他引:1  
硫同位素作为一种稳定的同位素,几乎遍布各种自然环境,出现于地质上所能跨越的所有温度范围。自然界中,不同环境下δ~(34)S值的差别可达180‰。研究表明,蒸发沉积硫酸盐的δ~(34)S值可以代表相应水体的δ~(34)S值,通过研究蒸发岩中的δ34S值,结合其它指标,可判断沉积环境,示踪成矿物质来源,研究成矿作用过程,为重建古地理古环境提供依据。在前人研究基础上总结了硫同位素分馏的影响因素及其在地球化学方面的应用;分析了陆相盆地蒸发咸化过程中水体δ~(34)S值的变化特征;对比研究了部分海陆相盆地硫酸盐δ~(34)S值特征,并指出对陆相盆地,不同类型的水体中δ~(34)S值变化趋势仍需进一步研究。  相似文献   
976.
Q methodology provides a novel, quantitative approach to reveal stakeholder perspectives and was used to assess social acceptance of Marine Protected Areas (MPAs) with fisheries and conservation management goals using the Devon & Severn region, UK as a case study site. Participants sorted a set of statements (n=42) into a forced-choice frequency distribution and centroid analysis revealed three factors for interpretation: (1) ‘pro-conservation’, characterised by views that conservation should be prioritised over commercial and economic interests; (2) ‘pro-fisheries’ who saw fishing as the priority and expressed concerns over the uncertainty of management measures and the number of planned MPAs; and (3) ‘win–win’ who felt that the current approach to marine management using MPAs would allow both fisheries and conservation goals to be met. Despite some differences in opinion, social acceptability of MPAs was identified across all three discourses, but was limited by the knock-on effects of the exclusion of stakeholders from the implementation of MPAs and the development of management measures. This resulted in disenfranchisement and uncertainty over the future of their activities. The results suggest that social acceptability of MPAs is generated by effective and ongoing stakeholder engagement, transparency and honesty relating to the costs and benefits of designations and a certainty that once sites are in place the resources exist for their effective management. Understanding social acceptability will guide adaptive management and increase the chances of MPA success and the meeting of global targets.  相似文献   
977.
A decade of international discussion on marine biological diversity beyond areas of national jurisdiction (BBNJ) culminated in 2015 with a United Nations General Assembly Resolution to establish an international legally-binding instrument on the conservation and sustainable use of BBNJ. Proponents of the new instrument therefore consider it as an opportunity to eliminate gaps in the current legal regime and promote better coordination. As the next step in the negotiations begins, substantial lessons can be drawn from the 1995 UN Fish Stocks Agreement (UNFSA), which has faced many of the same challenges related to gaps in scientific knowledge, uneven governance and regulatory capacities, and inherent unpredictability, both ecologically and in terms of anthropogenic drivers of change. For BBNJ, however, such challenges are far more complex due to the diversity of stakeholder communities and the diversity of resources involved, including fish and mineral resources with tangible economic values, marine genetic resources of unknown value, and the culturally-specific values attached to charismatic species and conservation in general. Drawing on lessons from UNFSA, it is argued that the establishment of marine protected areas (MPAs) under the BBNJ instrument would be particularly well served by a similar regional approach aligned with existing international agreements. In this regard, it is recommended that the capacity building under the new international instrument on BBNJ should focus inter alia on the secretariats of the regional fishery management organizations in order to enhance intra-regional and inter-regional cooperation and sharing of best practices.  相似文献   
978.
Imposex incidence and biometric parameters were investigated in six muricid species along of 1200 km of Ecuadorian shore and in Galapagos archipelago. The obtained data, were compared to previous studies performed in the same area in 2009. The results showed that moderate imposex levels still occur in coastal areas of Ecuador, even after global TBT ban. However, a reduction in imposex parameters was detected in the sampled sites, indicating probably relationship to the global TBT ban issued by IMO at 2008. On the other hand, the levels currently reported in present study indicates that TBT environmental concentrations are still high enough to produce biological effects in studied areas. In addition, imposex incidence in four muricid species from Galapagos islands were detected suggesting that this marine protected area is under threat of antifouling contamination. These findings, after TBT global ban, denotes that current regulations and conservation plans still need to address such an issue and incorporate more restrictive management rules, particularly in complex coastal areas, vulnerable and unique systems such as the Galapagos Islands.  相似文献   
979.
Marine Spatial Planning (MSP) has experienced vigorous growth on the international scale in recent years, and several practices has emerged from different countries. The demand for specific training in the preparation and implementation of marine planning has therefore already shown itself to be quite relevant on a global scale. Educational initiatives related to MSP have to respond to the increased complexity of MSP, which integrates environmental and economic perspectives on marine resources and maritime sectors, considering governance framework as well as maritime affairs and legislation.This paper aims at addressing the educational and training needs for the development of both academic education and professional training in MSP. Learning skills, contents and methods of an ‘ideal’ MSP course are depicted from widely accepted operative guides on MSP and from the EU Framework Directive on MSP (2014/89/EU). They are considered for the analysis of the current educational offer around MSP, performed in a sample of countries that have already undergone a process of implementation of MSP by Law. As result, beside the great variety of courses, it emerges that MSP education seems to be often regarded from an environmental perspective – in continuity with Integrated Coastal Management education – while planning theory and experiences in MSP are the least represented contents. Results are discussed in relation to three major challenges: i) how educational offer reflects on transdisciplinarity, ii) the role of theory in MSP courses, and iii) the enforceability of Plans as major concern in MSP.  相似文献   
980.
Despite increasing attention paid to the value of marine resources, in particular marine protected areas (MPAs), their economic valuation focuses mainly on use values of ecosystem services such as fishery and tourism. Furthermore, most MPA related studies are carried out for coastal ecosystems, especially tropical coral reefs. The valuation of remote marine ecosystems is rare. The main objective of this paper is to estimate public willingness to pay (WTP) for alternative management regimes of a network of offshore MPAs in the North Sea under the Marine Strategy Framework Directive (MSFD). In a baseline valuation study carried out just before the adoption of the MSFD, beach visitors and a random sample of coastal and non-coastal residents were asked for their preferences for two alternative management options of three remote, ecologically sensitive areas with multiple use conflicts. Despite the lack of public awareness and familiarity with the offshore marine areas, a majority of 70% is willing to pay extra tax for their protection. Using a conservative value elicitation procedure, Dutch households are willing to pay on average maximum 0.25% of their annual disposable income to ban access and economic use. This serves as an indicator of what a network of remote MPAs in the MSFD is allowed to cost according to the Dutch tax payer.  相似文献   
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