文章来源:未知 文章作者:meng 发布时间:2010-01-22 00:24 字体: [ ]  进入论坛

Springtime ozone1 levels above western North America are rising primarily主要地,根本上 due to air flowing eastward2 from the Pacific Ocean, a trend that is largest when the air originates in起源于,发生于 Asia. Such increases in ozone could make it more difficult for the United States to meet Clean Air Act standards for ozone pollution at ground level, according to a new international study. Published online today in the journal Nature, the study analyzed4 large sets of ozone data captured since 1984.

"In springtime, pollution from across the hemisphere, not nearby sources, contributes to the ozone increases above western North America," said lead author Owen R. Cooper, of the NOAA-funded Cooperative Institute for Research in Environmental Sciences at the University of Colorado at Boulder5. "When air is transported from a broad region of south and east Asia, the trend is largest."

The study focused on springtime ozone in a slice of the atmosphere from two to five miles above the surface of western North America, far below the protective ozone layer but above ozone-related, ground-level smog烟雾 that is harmful to human health and crops. Ozone in this intermediate中间的,中级的 region constitutes组成,构成 the northern hemisphere background, or baseline, level of ozone in the lower atmosphere. The study was the first to pull together and analyze3 nearly 100,000 ozone observations gathered in separate studies by instruments on aircraft, balloons and other platforms.

Combustion6 of fossil fuels矿物燃料,化学燃料 releases pollutants污染物 like nitrogen oxides氧化氮 and volatile8爆炸性的,挥发性的 organic compounds, or VOCs, which react in the presence of sunlight to form ozone. North American emissions9 contribute to global ozone levels, but the researchers did not find any evidence that these local emissions are driving the increasing trend in ozone above western North America.

Cooper and colleagues from NOAA's Earth System Research Laboratory in Boulder and eight other research institutes used historical data of global atmospheric10 wind records and sophisticated computer modeling to match each ozone measurement with air-flow patterns for several days before it was recorded. This approach essentially11 let the scientists track ozone-producing emissions back to a broad region of origin.

This method is like imagining a box full of 40,000 tiny weightless balls at the exact location of each ozone measurement, said Cooper. Factoring in winds in the days prior to先前,居先 the measurement, the computer model estimates which winds brought the balls to that spot and where they originated.

When the dominant12 airflow came from south and east Asia, the scientists saw the largest increases in ozone measurements. When airflow patterns were not directly from Asia, ozone still increased but at a lower rate, indicating the possibility that emissions from other places could be contributing to the ozone increases above North America.

The study used springtime ozone measurements because previous studies have shown that air transport from Asia to North America is strongest in spring, making it easier to discern识别,领悟 possible effects of distant pollution on the North American ozone trends.

Ozone-measuring research balloons and research aircraft collected a portion of the data. Commercial flights equipped with ozone-measuring instruments also collected a large share of the data through the MOZAIC program, initiated13 by European scientists in 1994. The bulk of大多数,大部 the data was collected between 1995 and 2008, but the team also included a large ozone dataset from 1984.

The analysis shows an overall significant increase in springtime ozone of 14 percent from 1995 to 2008. When they included data from 1984, the year with the lowest average ozone level, the scientists saw a similar rate of increase from that time through 2008 and an overall全部的,全体的 increase in springtime ozone of 29 percent.

"This study did not quantify量化,定量 how much of the ozone increase is solely14 due to Asia," Cooper said. "But we can say that the background ozone entering North America increased over the past 14 years and probably over the past 25 years."

The influence of ozone from Asia and other sources on ground-level air quality is a question for further study, Cooper said. Scientists will need to routinely measure ozone levels close to the surface at several locations along the West Coast to see whether similar trends are impacting ground-level air quality.


1 ozone omQzBE     
  • The ozone layer is a protective layer around the planet Earth.臭氧层是地球的保护层。
  • The capacity of ozone can adjust according of requirement.臭氧的产量可根据需要或调节。
2 eastward CrjxP     
  • The river here tends eastward.这条河从这里向东流。
  • The crowd is heading eastward,believing that they can find gold there.人群正在向东移去,他们认为在那里可以找到黄金。
3 analyze RwUzm     
vt.分析,解析 (=analyse)
  • We should analyze the cause and effect of this event.我们应该分析这场事变的因果。
  • The teacher tried to analyze the cause of our failure.老师设法分析我们失败的原因。
4 analyzed 483f1acae53789fbee273a644fdcda80     
v.分析( analyze的过去式和过去分词 );分解;解释;对…进行心理分析
  • The doctors analyzed the blood sample for anemia. 医生们分析了贫血的血样。 来自《简明英汉词典》
  • The young man did not analyze the process of his captivation and enrapturement, for love to him was a mystery and could not be analyzed. 这年轻人没有分析自己蛊惑著迷的过程,因为对他来说,爱是个不可分析的迷。 来自《简明英汉词典》
5 boulder BNbzS     
  • We all heaved together and removed the boulder.大家一齐用劲,把大石头搬开了。
  • He stepped clear of the boulder.他从大石头后面走了出来。
6 combustion 4qKzS     
  • We might be tempted to think of combustion.我们也许会联想到氧化。
  • The smoke formed by their combustion is negligible.由它燃烧所生成的烟是可忽略的。
7 pollutants 694861490fe64672170a0da250a277c7     
污染物质(尤指工业废物)( pollutant的名词复数 )
  • Pollutants are constantly being released into the atmosphere. 污染物质正在不断地被排放到大气中去。
  • The 1987 Amendments limit 301(g) discharges to a few well-studied nonconventional pollutants. 1987年的修正案把第301条(g)的普通排放限制施加在一些认真研究过的几种非常规污染物上。 来自英汉非文学 - 环境法 - 环境法
8 volatile tLQzQ     
  • With the markets being so volatile,investments are at great risk.由于市场那么变化不定,投资冒着很大的风险。
  • His character was weak and volatile.他这个人意志薄弱,喜怒无常。
9 emissions 1a87f8769eb755734e056efecb5e2da9     
排放物( emission的名词复数 ); 散发物(尤指气体)
  • Most scientists accept that climate change is linked to carbon emissions. 大多数科学家都相信气候变化与排放的含碳气体有关。
  • Dangerous emissions radiate from plutonium. 危险的辐射物从钚放散出来。
10 atmospheric 6eayR     
  • Sea surface temperatures and atmospheric circulation are strongly coupled.海洋表面温度与大气环流是密切相关的。
  • Clouds return radiant energy to the surface primarily via the atmospheric window.云主要通过大气窗区向地表辐射能量。
11 essentially nntxw     
  • Really great men are essentially modest.真正的伟人大都很谦虚。
  • She is an essentially selfish person.她本质上是个自私自利的人。
12 dominant usAxG     
  • The British were formerly dominant in India.英国人从前统治印度。
  • She was a dominant figure in the French film industry.她在法国电影界是个举足轻重的人物。
13 initiated 9cd5622f36ab9090359c3cf3ca4ddda3     
n. 创始人 adj. 新加入的 vt. 开始,创始,启蒙,介绍加入
  • He has not yet been thoroughly initiated into the mysteries of computers. 他对计算机的奥秘尚未入门。
  • The artist initiated the girl into the art world in France. 这个艺术家介绍这个女孩加入巴黎艺术界。
14 solely FwGwe     
  • Success should not be measured solely by educational achievement.成功与否不应只用学业成绩来衡量。
  • The town depends almost solely on the tourist trade.这座城市几乎完全靠旅游业维持。
TAG标签: air ozone America Asia