撒哈拉沙尘对形成巴哈马群岛起主要作用
文章来源:未知 文章作者:enread 发布时间:2014-07-26 07:28 字体: [ ]  进入论坛
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A new study suggests that Saharan dust played a major role in the formation of the Bahamas islands. Researchers from the University of Miami (UM) Rosenstiel School of Marine1 and Atmospheric2 Science showed that iron-rich Saharan dust provides the nutrients3 necessary for specialized4 bacteria to produce the island chain's carbonate-based foundation. UM Rosenstiel School Lewis G. Weeks Professor Peter Swart and colleagues analyzed5 the concentrations of two trace elements characteristic of atmospheric dust -- iron and manganese(锰) -- in 270 seafloor samples collected along the Great Bahama Bank over a three-year period. The team found that the highest concentrations of these trace elements occurred to the west of Andros Island, an area which has the largest concentration of whitings, white sediment-laden bodies of water produced by photosynthetic6 cyanobacteria(蓝藻细菌).
 
"Cyanobacteria need 10 times more iron than other photosynthesizers because they fix atmospheric nitrogen," said Swart, lead author of the study. "This process draws down the carbon dioxide and induces the precipitation of calcium7 carbonate, thus causing the whiting. The signature of atmospheric nitrogen, its isotopic8 ratio is left in the sediments9."
 
Swart's team suggests that high concentrations of iron-rich dust blown across the Atlantic Ocean from the Sahara is responsible for the existence of the Great Bahama Bank, which has been built up over the last 100 million years from sedimentation10 of calcium carbonate. The dust particles blown into the Bahamas' waters and directly onto the islands provide the nutrients necessary to fuel cyanobacteria blooms, which in turn, produce carbonate whitings in the surrounding waters.
 
Persistent11 winds across Africa's 3.5-million square mile Sahara Desert lifts mineral-rich sand into the atmosphere where it travels the nearly 5,000-mile northwest journey towards the U.S. and Caribbean. The paper, titled "The fertilization of the Bahamas by Saharan dust: A trigger for carbonate precipitation?" was published in the early online edition of the journal Geology. The paper's authors include Swart, Amanda Oehlert, Greta Mackenzie, Gregor Eberli from the UM Rosenstiel School's Department of Marine Geosciences and John Reijmer of VU University Amsterdam in the Netherlands.


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1 marine 77Izo     
adj.海的;海生的;航海的;海事的;n.水兵
参考例句:
  • Marine creatures are those which live in the sea. 海洋生物是生存在海里的生物。
  • When the war broke out,he volunteered for the Marine Corps.战争爆发时,他自愿参加了海军陆战队。
2 atmospheric 6eayR     
adj.大气的,空气的;大气层的;大气所引起的
参考例句:
  • Sea surface temperatures and atmospheric circulation are strongly coupled.海洋表面温度与大气环流是密切相关的。
  • Clouds return radiant energy to the surface primarily via the atmospheric window.云主要通过大气窗区向地表辐射能量。
3 nutrients 6a1e1ed248a3ac49744c39cc962fb607     
n.(食品或化学品)营养物,营养品( nutrient的名词复数 )
参考例句:
  • a lack of essential nutrients 基本营养的缺乏
  • Nutrients are absorbed into the bloodstream. 营养素被吸收进血液。 来自《简明英汉词典》
4 specialized Chuzwe     
adj.专门的,专业化的
参考例句:
  • There are many specialized agencies in the United Nations.联合国有许多专门机构。
  • These tools are very specialized.这些是专用工具。
5 analyzed 483f1acae53789fbee273a644fdcda80     
v.分析( analyze的过去式和过去分词 );分解;解释;对…进行心理分析
参考例句:
  • The doctors analyzed the blood sample for anemia. 医生们分析了贫血的血样。 来自《简明英汉词典》
  • The young man did not analyze the process of his captivation and enrapturement, for love to him was a mystery and could not be analyzed. 这年轻人没有分析自己蛊惑著迷的过程,因为对他来说,爱是个不可分析的迷。 来自《简明英汉词典》
6 photosynthetic 1f9a8b17a4e53d9a4fd0ed5147e2f5bd     
adj.光合的,促进光合作用的
参考例句:
  • In some plants photosynthetic products are stored in the form polyfructosans. 在有些植物中,光合作用产物是以多聚果糖的形式储藏。
  • Chlorotic or necrotic lesions were evidence of decreased photosynthetic tissues. 缺绿的或坏死的侵蚀斑便是减少了光合组织的证据。
7 calcium sNdzY     
n.钙(化学符号Ca)
参考例句:
  • We need calcium to make bones.我们需要钙来壮骨。
  • Calcium is found most abundantly in milk.奶含钙最丰富。
8 isotopic 7ad2ece915960e8c295e01a4d04cc192     
adj.同位素的,合痕的
参考例句:
  • The isotopic signatures of most ancient limestones indicated the same process. 大多数古代石灰岩的同位素特征说明了同样的过程。 来自辞典例句
  • Isotopic discrimination is not likely. 同位素甄别是不可能的。 来自辞典例句
9 sediments 8b3acb612b624abdf2c2881bc6928565     
沉淀物( sediment的名词复数 ); 沉积物
参考例句:
  • When deposited, 70-80% of the volume of muddy sediments may be water. 泥质沉积物沉积后,体积的70-80%是水。
  • Oligocene erosion had truncated the sediments draped over the dome. 覆盖于穹丘上的沉积岩为渐新世侵蚀所截削。
10 sedimentation msEyJ     
n.沉淀,沉积
参考例句:
  • Sedimentation, the damage of a breach are problems, too. 而且沉积和决口的问题,也是存在的。 来自英语晨读30分(高二)
  • Sedimentation and denudation play a role in exceptional cases. 沉积和剥蚀作用的影响只在特殊情况下起作用。
11 persistent BSUzg     
adj.坚持不懈的,执意的;持续的
参考例句:
  • Albert had a persistent headache that lasted for three days.艾伯特连续头痛了三天。
  • She felt embarrassed by his persistent attentions.他不时地向她大献殷勤,使她很难为情。
TAG标签: island dust Bahama
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