公共英語一級閲讀文章《海水鹽度》

公共英語一級的難度不大，但是閲讀理解還是不少考生容易出錯的。下面，小編為大家送上一篇公共英語一級閲讀文章，歡迎閲讀。

The Salinity of Ocean Waters

If the salinity of ocean waters is analyzed, it is found to vary only slightly from place to place. Nevertheless, some of these small changes are important. There are three basic processes that cause a change in oceanic salinity.

One of these is the subtraction of water from the ocean by means of evaporation - conversion of liquid water to water vapor. In this manner the salinity is increased, since the salts stay behind. If this is carried to the extreme, of course, white crystals of salt would be left behind.

The opposite of evaporation is precipitation, such as rain, by which water is added to the ocean. Here the ocean is being diluted so that the salinity is decreased. This may occur in areas of high rainfall or in coastal regions where rivers flow into the ocean. Thus salinity may be increased by the subtraction of water by evaporation, or decreased by the addition of fresh water by precipitation or runoff.

Normally, in tropical regions where the sun is very strong, the ocean salinity is somewhat higher than it is in other parts of the world where there is not as much evaporation. Similarly, in coastal regions where rivers dilute the sea, salinity is somewhat lower than in other oceanic areas.

A third process by which salinity may be altered is associated with the formation and melting of sea ice. When sea water is frozen, the dissolved materials are left behind. In this manner, sea water directly beneath freshly formed sea ice has a higher salinity than it did before the ice appeared. Of course, when this ice melts, it will tend to decrease the salinity of the surrounding water. In the Weddell Sea Antarctica, the densest water in the oceans is formed as a result of this freezing process, which increases the salinity of cold water. This heavy water sinks and is found in the deeper portions of the oceans of the world.

海水鹽度

如果我們分析海水的鹽度，會發現地區間只有輕微的變化，然而有些小的變化是重要的。導致海洋的鹽度變化的基本過程有三個，其中之一是通過蒸發的方式即把液態水轉化為水蒸氣來減少海洋中的水分。這樣由於鹽留了下來，所以鹽度增大。當然，如果這種方式走向極端，將會餘下白色的鹽晶體。與蒸發相反的是降水，如降雨，由此水被加入海中，海水被稀釋，從而鹽度降低。這種情形會發生在大量降雨的地區，或江河入海岸處。因此，鹽度通過蒸發減少水分而上升或通過降水或徑流增加淡水成分而下降。一般來説，在陽光很強烈的熱帶地區，海水的鹽度略高於世界上其它沒有熱帶那樣多的蒸發的地區。同理，在江河稀釋海水的海岸地帶，海水鹽度略低於其它海區。第三個可以變更鹽度的過程與海洋中冰的形成和融化有關。海水凍結時，溶於其中的物質被留了下來。這樣，在新形成的海 水冰面的正下方的海水比在冰形成之前有更高的'鹽度。當然，當冰融化的時候，會降低周圍水中的鹽度。 在南極洲邊緣的威德爾海中，結冰過程增加低温海水的鹽度，從而形成了濃度最大的海水。這些大密度的海水下沉，可以在世界海洋的深水域發現。

附：公共英語一級解題技巧

1.細節題

這種題目是針對文章的某些情節而設置的，以考查考生理解具體細節的能力。其所使用的句型和詞語與原文相同或基本相同，因此在文中很容易找到答案。

2.是非題

這種題目是針對文中具體的某個句話而設置的，考查形式為：對所選的句子進行同義或反義的轉換。對於此類題目只要考生理解所選的句子，一般都能選出正確的答案。

3.推理題

這種題目有一定的難度，往往不能直接從文中找到答案，而必須根據上下文及其相互間的關係或對整篇文章進行深層的理解以後，才能得出答案。

4.釋義題

此類題目並非單純考查考生的詞彙，而是考查考生根據上下文猜測單詞詞義及某個單詞在具體語境中的具體含義。對於此類題目只要考生理解其所在句子所要表達的意思，就能很容易地推出該單詞的含義。

5.主旨題

要求考生在閲讀和理解全文的基礎上對文章做出歸納、概括或評價等。體現形式通常為：文章的標題(ti-de)、主題(main idea)、結論(conclusion)等。