排序方式： 共有108条查询结果，搜索用时 15 毫秒
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Glibert PM Azanza R Burford M Furuya K Abal E Al-Azri A Al-Yamani F Andersen P Anderson DM Beardall J Berg GM Brand L Bronk D Brookes J Burkholder JM Cembella A Cochlan WP Collier JL Collos Y Diaz R Doblin M Drennen T Dyhrman S Fukuyo Y Furnas M Galloway J Granéli E Ha DV Hallegraeff G Harrison J Harrison PJ Heil CA Heimann K Howarth R Jauzein C Kana AA Kana TM Kim H Kudela R Legrand C Mallin M Mulholland M Murray S O'Neil J Pitcher G Qi Y Rabalais N Raine R Seitzinger S Salomon PS Solomon C 《Marine pollution bulletin》2008,56(6):1049-1056
The proposed plan for enrichment of the Sulu Sea, Philippines, a region of rich marine biodiversity, with thousands of tonnes of urea in order to stimulate algal blooms and sequester carbon is flawed for multiple reasons. Urea is preferentially used as a nitrogen source by some cyanobacteria and dinoflagellates, many of which are neutrally or positively buoyant. Biological pumps to the deep sea are classically leaky, and the inefficient burial of new biomass makes the estimation of a net loss of carbon from the atmosphere questionable at best. The potential for growth of toxic dinoflagellates is also high, as many grow well on urea and some even increase their toxicity when grown on urea. Many toxic dinoflagellates form cysts which can settle to the sediment and germinate in subsequent years, forming new blooms even without further fertilization. If large-scale blooms do occur, it is likely that they will contribute to hypoxia in the bottom waters upon decomposition. Lastly, urea production requires fossil fuel usage, further limiting the potential for net carbon sequestration. The environmental and economic impacts are potentially great and need to be rigorously assessed. 相似文献
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This study presents water quality parameters such as nutrients, phytoplankton biomass and dissolved oxygen based on 11 years of water quality data in Victoria Harbor and examined how the Pearl River estuary discharge in summer and year round sewage discharge influenced these parameters. Nutrients in Victoria Harbor were strongly influenced by both the Pearl River and sewage effluent, as indicated by the high NO(3) inputs from the Pearl River in summer and higher NH(4) and PO(4) in Victoria Harbor than both its sides. N:P ratios were low in the dry season, but increased to >16:1 in the wet season, suggesting that P is potentially the most limiting nutrient in this area during the critical period in the summer. Although there were generally high nutrients, the phytoplankton biomass was not as high as one would expect in Victoria Harbor. In fact, there were high concentrations of chl near the bottom well below the photic zone. Salinity near the bottom was lower in Victoria Harbor than at the two entrances to Victoria Harbor, suggesting strong vertical mixing within Victoria Harbor. Therefore, strong vertical mixing and horizontal advection appear to play an important role in significantly reducing eutrophication impacts in Victoria Harbor. Consequently, dissolved oxygen near the bottom was low in summer, but only occasionally dipped to 2 mgL(-1) despite the high organic loading from sewage effluent. 相似文献
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剪切带中的褶皱是很普遍的,它们或者形成于被剪切带所切割的早期层理中,或者是由剪切带本身所产生的叶理所形成。褶皱既可以被动地形成也可以主动地形成(通过纵向弯曲或其它不稳定类型)。剪切带中被动型褶皱的最简单样式是由剪切带中的剪切梯度造成的“S”叶理弯曲。剪切带中的早期层理在剪切作用中是被拉伸成为石香肠还是缩短成纵弯褶皱要取决于该层理与剪切带边界的交角,Ramsay(1980,图3)曾对此进行了大量的研究。简单剪切产生的片理化糜棱叶理。如果它反映的是剪切带累积应变的XY面(X≥Y≥Z指定了主应力方面和应力大小),将会与剪切或或剪切带边界成45°夹角,并继续加强、拉伸和向着平行剪切带壁方向旋转。这绝不是流动变形领域里的缩短机制。应力很强时,叶理会变得几乎平行剪切带的边界,而这个边界在简单剪切作用中是一个非常形面。因此,剪切带内的褶皱不可能在由简单剪切所形成的叶理中。 相似文献
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熔体中固溶体端元组分的粘着(attachment)动力学可导致自组织的振荡分带发生,这一过程是通过晶体生长化学动力学相关的反馈来实现的。这种振荡分带是直接从熔体中结晶的,而没有外部施加的周期性物质状态(压力、温度或组分)干预。本文提出了一个在熔体中晶体生长的数学模型,拓扑学的证据已证明该模型可以适用于晶体的振荡分带。同时,本文还提供了若干特征类型的振荡环带剖面,业已证明,分又分析可被用于获得振荡分带存在的判据。 相似文献
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根据变斑晶中的矿物包体序列、矿物的化学分带和反应结构中的岩相解释,结合标准的关键矿物平衡所证明的反应历史的解释建立了单旋回石榴石堇青石片麻岩的P-T-t轨迹。对于每个实例来说,所研究过的岩石表现出一个平缓的“顺时针”P-T-t轨迹,而且在高温条件下被准绝热减压所扰动,接着发生了等压的冷却过程,750～800℃的峰值温度 相似文献
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