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近似原文by loveyj613，确定是原文，我在考场上看到过这片，就好像少了最后一段。。。
Biomagnification means that the level of a toxin in animals' tissues rises as one moves up the food chain. For instance, as larvae eat algae, fish eat the larvae, and bigger fish eat smaller fish, the toxin present in the algae becomes increasingly concentrated; top predators like swordfish and polar bears end up with the highest doses in their tissues. This can happen with stable, fatsoluble (脂溶的) chemicals that aren't easily excreted in urine or feces. Biomagnification was first studied in the late 1960s in aquatic food webs, explains Frank Gobas, professor at Simon Fraser University and leader of the study. To screen chemicals, scientists began using a property known as Kow, which indicates how readily(轻易的，快捷的) a chemical dissolves (溶解，消除，消散) in water compared with fat and thus predicts how easily it will move from a fish's blood lipids into water through its gills（1）. Low-Kow, or more watersoluble(水溶的), chemicals don't build up in the fish food chain and were assumed to be safe.
KOW显示了相比脂肪来说，化学物质是很容易地溶解在水里的；而且也预测了这个化学物质是很容易从鱼的血脂里通过鳃被移到水里的。
Environmental chemists realized, however, that this assumption might not hold in food chains involving mammals and birds because their lungs are in contact with air, not water. This means that many chemicals that are relatively (相对来说地) soluble (可溶解的，易溶解的) in water and therefore don't accumulate in fish might remain in the tissues of land animals if they aren't volatile enough to easily move from the lungs into the air (predicted by a property called Koa). Supporting this idea, some organic chemicals that don't biomagnify (产生生物放大作用) in fish appeared to be doing so in other wildlife and humans. |
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发表于 2010-4-15 23:36:35
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