考古求确认！31、Tree 释放 VOC

Miley0119

15. 树木分解有害气体

　　By luciole(690)还有一篇感觉有点难，是研究树木对一种有害气体的分解作用，因为有一种物质还没分析出来，于是科学家猜想那个是有效降低两种废气的东西，但并未得到证实。

　　By haoz0001一种理论说树木可以exhale一种气体H，在某种情况下或者一定温度下这种气体可以跟两种污染气体结合产生一种雾(haze). 好像还列举了一对其他因素。这种结合好像跟风也有关(忘记了是有影响还是没影响)。一个research对这种雾进行研究，发现haze的量要大于预期。所以得出结论，某些具有H相似功能的气体还未被发现。有问main idea,还有为了减少污染影响，haze形成，什么措施最没用。

　　byansonchan(Q50 V44)第四篇是变态。。最后几题还剩11分钟的时候突然出来一篇一屏半的，我那时候都觉得要放弃了。是树木分解有害气体的那篇。非常难!一堆专业词汇……我没背词汇就直接冲og了。。所以看得不是很懂。但是有一点是大概清晰的。说什么一开始以为有害气体怎么怎么样了，但是后来科学家发现还有一些有害气体，没被发现的。后来用一个实验说明了这些unknown气体的存在(但是第二段我没细看了，没时间了)。第一题的题目就五行了，我那时候就要崩溃了～问你政府要怎么怎么样的话，以下哪种措施最不可行。

　　bydemonj(760)应该是树木放射有毒气体。这篇真没咋看懂……到最后了有点慌……不过不长，大家镇定一下应该能看懂。第一题是问采取下面哪个措施来减少有毒气体影响会受到最小的作用。大家看的时候注意一下。还有第二段里说decrease的速度比实际想象的要快，作者用了一个词an……来形容，问用这个词有什么用意

　　bylovepiao第一段就是树的VONS这个东西~释放一种HD~举例比如I和T(都是不认识的单词)产生haze(这句没看懂，不知道是不是污染)~但是还有一些与VONS类似的物质没分析出来

　　第二段是讲为什么怀疑有其他类似物质的存在。First因为与风向无关、Second因为I和T(就是第一段提的例子)I只能daytime怎么着~而HD是daytime和nighttime都可以~

　　题目忘记了。。。~就记得有一道题题干巨长!看完我都疯了~先是介绍了某个情况没看懂。。~之后问下面哪项least useful to achieve the government's proposal?A说限制排放那个HD~C貌似是说工厂怎么着~选项D是说患哮喘的人应该多呆在indoor~我瞎选的E就是和风向有关的选项

mavis77

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.

cutie0829

刚在q里跟一个9。30的孩子聊，她说voc这篇他遇到了，考古基本都对，但是不全，是三段

didai1314

有没有能确认的

gogogmat800

ding

思之如狂

UPPP!

cutie0829

up

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