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题库 / Prep2007E2-RC-14
Solar ponds are bodies of water in which circulation is incomplete and there is a very high salt concentration that increases with depth. This vertical change in salinity serves to trap heat because concentrated brine in the lowest water level acts as a collector and storage area for solar heat, while the less saline, lighter water at the upper levels provides insulation. Heat is thus retained in the depths.
An artificial pond of this type has been constructed on the western shore of the Dead Sea in Israel in order to test its suitability as a source of low-grade heat for conversion into electricity. An immediate threat to the success of the venture was the growth of algae. Water in solar ponds must be kept maximally transparent to allow penetration of light to the deep storage area. Therefore, any particles of matter in the water, such as algae cells, that scatter or absorb light will interfere with the collection of heat.
One proposed method of controlling the algae was the application of an algicide. However, the Dead Sea is a closed body of water without any outlet and as such is very easily contaminated. Extensive use of chemicals in numerous future full-scale solar ponds would lead to such contamination of the Dead Sea, which now enjoys a lucrative tourist trade.
A recent experiment has supplied a more promising method for controlling the algae. To repress the algae cells' capacity for accommodating themselves to environmental changes, the water in the solar pond was first made more saline through evaporation and then diluted by a rapid inflow of fresh water. This shock reduced the cells' ability to regulate the movement of water through their membranes. They rapidly absorbed water, resulting in distortions of shape, increase in volume, and impairment to motility. Their buoyancy adversely affected, the cells sank to the bottom of the pond, where they encountered the hot waters of the storage layer and were destroyed. This method allows for effective control of nuisance algae while leaving solar ponds as one of the cleanest technologies providing energy for human use.
According to the passage, the growth of algae was considered a threat to the success of the artificial pond near the Dead Sea because the algae
produce excess oxygen that lowers the water temperature in the pond
restrict the circulation of water within the pond
enable heat to escape through the upper level of the pond
prevent light from penetrating to the lowest levels of the pond
prevent accurate measurement of the heat collected in the pond
题目分析：
题目释义：
细节题目
考点：
支持主题（Supporting ideas）
旨在考察我们对文章细节的认知
根据题设很容易定位在第二段，简单的说就是因为藻类细胞挡光了，没光就没热，自然就没有能源发电了。
选项分析：
A选项：产生过多的氧气降低了池塘的温度。文中没有提到这点，不能根据自己的常识解题。
B选项：阻止了在池塘中的水循环。作者提到水循环时是在说明为什么不能用药来杀死藻类细胞时，和藻类细胞本身的威胁没有关系。
C选项：让热量有能力从上层水中丧失。文中没有提到这点。
D选项：Correct. 阻止光渗透过池中最低一层的水。定位在“Water in solar ponds must be kept maximally transparent to allow penetration of light to the deep storage area. Therefore, any particles of matter in the water, such as algae cells, that scatter or absorb light will interfere with the collection of heat”。
E选项：阻止准确的对池中的热度的测量。整篇文章均没有提到要测量水的热度。
前一句Water in solar ponds must be kept maximally transparent to allow penetration of light to the deep storage area
Therefore, any particles of matter in the water, such as algae cells, that scatter or absorb light will interfere with the collection of heat.
Therefore, any particles of matter in the water, such as algae cells, that scatter or absorb light will interfere with the collection of heat.