Biomagnification有毒化学物质在食物链各个环节中的毒性渐进 means that the level of toxin in animals' tissues rises as one moves up the food chain. For instance, as larvae eat algae, （此处有题 问algae的作用，我选的是处在食物链最低端~~不知对否~） 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因为处在食物链顶端所以毒素最高 bears end up with the highest doses in their tissues. This can happen with stable, fat-soluble脂溶性的 chemicals that aren't easily excreted in urine or feces不容易通过尿或粪便排泄出去. Biomagnification was first studied in the late 1960s in aquatic水上的 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水分配系数, which indicates how readily a chemical dissolves in water compared with fat and thus predicts how easily it will move from a fish's blood lipids into water through its gills鳃. Low-Kow, or more water soluble可溶解的, chemicals don't build up in the fish food chain and were assumed to be safe. Gobas这个人第一个发现了这种化学物质可以在水中溶解，鱼可以很容易地通过鳃来排泄。Gobas一开始认为low-Kow安全。
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 soluble 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空气分配系数). Supporting this idea, some organic chemicals that don't biomagnify in fish appeared to be doing so in other wildlife and humans. 但是，环境学家认为这个假设不对，提出哺乳动物和鸟类可能不能排泄这种化学毒素，因为它们的肺接触空气而不是水。Koa
To explore this hypothesis, Gobas and graduate student Barry Kelly and colleagues collected plant and animal tissue samples— from lichens青苔 to beluga 白鲸whales killed in Inuit hunts—in the Arctic, where, because of weather patterns and cold temperatures, organic pollutant levels are high. They tested the samples not only for known POPs but also for several chemicals with a low Kow but high Koa, which suggested they might biomagnify in air-breathing animals. The measured levels of contaminants for various animals in aquatic and land food webs were similar to those predicted from a bioaccumulation model incorporating合并一体化 Koa and Kow, suggesting the model was correct. Chemicals with low Kow and high Koa stood out as potentially risky. 最后Gobas也说Low Kow并且high Koa的有潜在危险的，证实了Biomagnification，即毒素随着食物链的增长会沉积。
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发表于 2012-3-2 00:05:02
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