出人意料的是这棵幸存的树中年轮的木质中每公斤仅含2.3毫克汞。
More surprising still, the rings of the other two trees were mercury-free, despite there beingmercury in nearby soil.
更让人大跌眼镜的是,其他两棵书的年轮中汞含量为零,尽管其附近的土壤中含有汞。
Tree rings are made of tissue called xylem.
构成年轮的组织被称为木质部。
This is a set of channels that carry water and minerals from the soil to the leaves, so itscomposition might be expected to reflect what is in the soil.
这是从土壤中将水合矿物质输送至叶片的一组通道,所以其组分应该能够反映出土壤中的组分。
A second set of channels, the phloem, found just under a tree s bark, carries the products ofphotosynthesis to the roots.
第二组通道叫韧皮部,就长在树皮之下,它将光合作用的产物输送到树的根部。
This tissue, however, is not preserved from year to year.
然而该组织每年都会更新。
When Dr Rodriguez Martin sampled the phloem of the trees he had chopped down, he found itmuch richer in mercury than their xylem.
罗德里格斯马丁博士对被他砍倒的树的韧皮部采样后,他发现韧皮部的汞含量比木质部的要高。
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