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31、**Tree 释放 VOC 31、**Tree 释放 VOC
植物释放有毒气体那篇.这篇是最后一篇,当时还有20几分钟,所以看得还比较仔细---by imfred760
P1一开始说植物会释放有毒气体VOC,其中举了两个例子,说释放出来的有毒气体会结合hexyl(一种碱)并以气态或液态存在(haze).然后作者说其实植物不仅仅能释放所知的那几种有毒气体。
P2为了证明是否有释放出未知的气体,科学家们做了一个实验:在树木的顶上放含有那种碱的瓶子,然后发现碱被中和的速度超出了预测的范围!(题目Q2)然后作者说尽管有两个影响因素,但是实验的准确性是可以得到证明的。这两个因素是:(1)可能会有风把工业区的毒气吹过来;但是作者说在工业区,马路附近,森林里面所测得的数据都相近,所以这个因素被排除。(2)树木在白天释放的毒气会超过夜晚所释放的毒气;但是作者说在白天跟晚上hexyl的消耗率都超出了预期,所以这个因素也被排除了。
题目
Q1、哪项least useful to achieve the government's proposal?(问government的做法中哪一个是对于减轻毒气影响最没用的)
A(问except哪个方式都可以减少Haze,我选的是Vehicle那道,因为后面写汽车emission VOC,明显不对。--by yolanda227750 Q51 V41)
(preserve emitting这些物质的forest in urban vicinity,near emitting这些物质的工厂【760】)
(一开始以为760和750两人的选项是不同的组合,但今天发现似乎是在一起的。由于这是lz最后一篇,没多少时间了,所以就选了个preserve。--by waiting1 690)
Q2、第二段里说decrease的速度比实际想象的要快,作者用了一个词an……(highlight)来形容,问用这个词有什么用意
A(问了文中提到的一个a开头的单词说明了啥,根据上下文推断那个词应该是“惊讶”,"unexpected“或者”矛盾“的意思,所以这个词说明,除了已知的之外,还有其他的unknown的物质。by suya 710)
Q3有一道主旨题应该是选第二段给第一段中科学家的怀疑提供了证据。不长,题目有点绕...
-----by camelo777 760
疑似原文,和jj描述很像 The chemical reactions taking place just above a northern Michigan forest hint that trees there and elsewhere may be emitting highly reactive gases that scientists haven't yet identified or directly detected.
Many plants release large quantities of volatile organic compounds (VOCs). Some of those substances destroy ground-level ozone, says William H. Brune of Pennsylvania State University in State College . In another type of reaction, VOCs combine with hydroxyl radicals and other atmospheric constituents to produce the aerosol particles in haze (SN: 12/7/02, p. 360).
In the Michigan experiments, which took place within equipment mounted on a tower about 10 meters above 20-m-high treetops, Brune and his colleagues found that the concentration of hydroxyl radicals added to air samples during the experiments dropped much faster than the team could account for by the measured concentrations of 42 known VOCs and other atmospheric gases.
Several lines of evidence suggest that the hydroxyl radicals disappeared when they reacted with unknown VOCs, the researchers suggest in the April 30 Science. For example, concentrations of hydroxyl added to air samples during tests dropped at the same rate, regardless of whether prevailing winds were bringing clean air from Canada or polluted air from urban areas. Therefore, the phantom VOCs probably hadn't been produped by human activity, says Brune.
Also, the air samples' effect on hydroxyl during the tests varied according to the prevailing temperature. Other scientists have found that atmospheric concentrations of known tree-emitted VOCs, such as isoprene and terpenes, vary similarly. Because the anomalous effects occurred both day and night, the phantom VOCs probably aren't related to isoprene, which is emitted by vegetation only during daylight hours.
So far, chemical analyses of air samples haven't turned up any candidates for the unidentified gases. "We're not sure what these compounds are, but they're definitely there," says Brune.
The new research is "beautiful confirmation" of the notion that trees emit more types of highly reactive VOCs than are generally acknowledged, says Allen H. Goldstein, an atmospheric chemist at the University of California, Berkeley. His previous studies of the amounts of ozone absorbed by trees in a California pine forest also suggest the presence of unidentified VOCs. He proposes that they're related to terpenes.
Brune and his colleagues' arguments are "reasonably compelling," agrees Roger Atkinson of the University of California, Riverside. The work gives scientists a new group of atmospheric chemicals to look for, he says. The new data suggest that atmospheric concentrations of the purported VOCs above forests are about 1 part in 2 billion. |
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