Why the Earth’s Oceans Are Salty
為什麼海水是鹹的？
─ Bruce, Angela, Wesley
First, the good news. Water, the source of all life on Earth, is abundant. Now, the bad news. Most of it is undrinkable.
首先，有個好消息。水 ―― 地球上所有生命的源泉 ―― 非常豐富。接著，有個壞消息。大部分的水是不可飲用的。
Ninety-seven percent of the water on our planet is salty and 2% is frozen as ice at the poles, leaving a measly 1% for people to use. How is it, you may wonder, that so much of the liquid water on our planet is salty?
地球上 97% 的水是鹹的，2% 的水在兩極結凍成冰，只剩下少少的 1% 供人們使用。你可能會想知道：究竟地球上怎麼這麼多液態水都是鹹的？
Water is a compound of two hydrogen atoms and one oxygen atom: H2O. When water on the Earth’s surface evaporates as water vapor, it picks up tiny amounts of two gases found in the Earth’s atmosphere, carbon dioxide and sulphur dioxide. When this vapor forms raindrops, this “fresh” water is actually slightly acidic.
水是由兩個氫原子和一個氧原子組成的化合物：H2O。當地球表面的水蒸發成水蒸氣時，它會微量吸收存在於地球大氣中的兩種氣體：二氧化碳和二氧化硫。當這種水蒸氣形成雨滴時，這種「淡」水實際上是微酸性。
As it falls on the ground, the acid dissolves small amounts of mineral salts, which end up in the water, a process known as weathering. These tiny amounts of salts have built up for billions of years, producing our salty oceans. Volcanic activity also contributes to the saltiness of the ocean in similar ways.
當雨水落到地面時，裡頭的酸會溶解少量的礦物鹽類，最後流入水中，此過程稱為侵蝕。這些微量的鹽類已累積數十億年，造就了我們的鹹海洋。火山活動也以類似的方式促成了鹹海洋。
Most of us have accidentally gulped a bit of sea water and tasted its salt. You wouldn’t want that to happen while floating or swimming in the Dead Sea—its water is nearly 10 times as salty as that* found in the ocean!
我們大多數人都曾不小心吞下一點海水並嚐過其鹹度。你不會希望在死海中漂浮或游泳時發生這種狀況 ―― 其水的鹽分幾乎是海水的十倍！
Only a few microbes can stand so much salinity. Still, all those minerals are supposed to be good for healthy skin. We can’t drink it, but we can still bathe and swim in it.
僅有少數微生物能承受如此高的鹽度。儘管如此，所有那些礦物質應該都對健康的皮膚有益。我們不能喝它，但仍可以在其中沐浴及游泳。
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