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“嗅探空气”技术揭秘臭氧杀手

更新时间:2018-9-4 20:07:51 来源:纽约时报中文网 作者:佚名

The detectives hunting ozone-killing chemicals
“嗅探空气”技术揭秘臭氧杀手

It was a research station on the side of a volcano, 4,000 metres above sea level, that picked up the key signal: despite an international ban, someone, somewhere, was emitting an ozone-damaging pollutant.

一座位于火山一侧,海拔4,000米的研究站监测到了一个重要信息:尽管有国际禁令,某处有人正在排放对臭氧有害的污染物。

Stephen Montzka of the US’s National Oceanic and Atmospheric Administration (NOAA) was the first to notice. He had been analysing data collected at various sites since 2013. The measurements suggested that the decline of a dangerous chemical in the atmosphere, CFC-11, had been unexpectedly slowing down. “The finding was so surprising I had to be sure it was real,” he recalls.

美国国家海洋和大气管理局(NOAA)的蒙扎克(Stephen Montzka)是第一个注意到此状况的。自2013年以来,他一直在分析于不同地点收集的空气数据。测量结果表明,大气中危险化学品氟利昂(CFC11, 多年前被广泛运用于制冷剂和发泡剂,因对臭氧产生破坏而被禁用)的消退速度减缓了,这与科学家的预期不相符合。"这一发现令人感到惊讶,我决定要进一步确认。"他回忆时说道。

But it was the Mauna Loa data that convinced him. Since the 1950s, the Mauna Loa Observatory on the giant Hawaiian volcano of the same name has continuously monitored air as it wafts across the Pacific Ocean. In May 2018, an article published in the journal Nature revealed the worrying discovery in detail – CFC-11 was blowing over the Pacific Ocean from East Asia.

而莫纳罗亚天文台(Mauna Loa)的数据证实了他的猜想。自20世纪50年代以来,巨型夏威夷火山上的莫纳罗亚天文台不断监测着从太平洋飘过的空气数据。2018年5月,发表在《自然》杂志上的一篇文章详细揭示了令人担忧的发现——飘过太平洋的氟利昂来自于东亚。

Now, an international investigation is underway to find the source. That process could never have started without those initial measurements. By ‘sniffing the air’ and monitoring the levels of various gases in it, scientists are able to detect the presence of pollutants. This is the story of how they do it – and what happens when they find something fishy.

如今,寻找污染源的国际调查正在展开。若没有这些初步监测数据,这个调查可能永远不会开始。通过"嗅探空气",监测其中各种气体的水平,科学家们能够检测出污染物的存在。科学家们如何进行监测?当他们发现可疑状况时,会怎样应对?

Chlorofluorocarbons, or CFCs, were banned internationally in 1996 under an important treaty called the Montreal Protocol. Through the treaty, countries around the world decided how they would protect ozone – a trace gas in the atmosphere that keeps out ultraviolet radiation emitted by the sun. CFCs contain the ozone-destroying gas chlorine, which is gradually released from the CFCs as they linger in the atmosphere. Stopping CFCs from being used in products and by industry was meant to result in their steadily accelerating decline.

1996年,根据重要条约《蒙特利尔议定书》,氯氟烃(CFCs),或被称为氟氯化碳(Chlorofluorocarbons)的物质在国际上被禁止使用。通过该条约,世界各国确定了保护臭氧(一种大气中的微量气体,可阻挡太阳紫外线辐射)的措施。氟氯化碳含有破坏臭氧的氯气,氟氯化碳在大气中逗留时,氯气会逐渐从中游离出来。在产品中和生产过程中停止使用氟氯化碳,意味着它们的存量应该会持续的加速下降。

But Montzka and colleagues noticed that, since 2012, the rate of decline for a particular CFC, trichlorofluoromethane – CFC number 11 – had gone off track.

但蒙扎克和同事们注意到,自2012年以来,一种特定氟氯化碳的下降速度并没有加快反而减缓了。

There were various bits of evidence that pointed to a potential new source of CFC-11, says co-author Alistair Manning at the UK Met Office. This included the fact that the gradient, or difference in levels of atmospheric CFC-11 in the northern hemisphere and southern hemisphere, was diverging.

英国气象局的曼宁(Alistair Manning)表示,有各种各样的证据表明,氟利昂可能的新来源为东亚。这包括北半球和南半球大气氟利昂数据呈现出明显的梯度或差异。

“That narrowing of the gradient – it was starting to widen again, which then pointed to the fact that maybe there are new emissions in the northern hemisphere,” he says.

"南北半球缩小的梯度开始再次扩大,这意味着在北半球可能有新的污染源",他说道。

But that wasn’t enough to prove that someone was emitting a lot more CFC-11. It took the Mauna Loa data to reveal that. Manning was able to use the Met Office’s atmospheric dispersal-modelling tool to confirm the likely place from which this potential new CFC-11 had originated. He discovered that whenever Montzka’s CFC-11 measurements at Mauna Loa were lower, there was less wind from the direction of East Asia.

这还不足以证明有人正在排放更多的氟利昂。但莫纳罗亚天文台的数据证实了这一点。曼宁能够使用气象局的大气扩散建模工具来确认这种潜在的新氟利昂可能来自何处。他发现,蒙扎克在莫纳罗亚天文台获得的氟利昂测量数据较低时,都是来自东亚的风力较弱的时候。

“That’s another part of the jigsaw – something happening in East Asia that could possibly be causing this increase in emissions,” says Manning.

"这是另一个证据,说明在东亚的某种活动正在导致着污染物排放量的增加",曼宁说道。

When news broke that the prohibited gas appeared to be leeching out of East Asia, many were keen to look more closely. The UN, for one, has launched an investigation. But the paper in Nature also caught the attention of the Environmental Investigation Agency (EIA), a charity that campaigns against environmental crime and abuse.

当消息传开,禁用气体可能正在从东亚流出,许多人都密切关注。例如,联合国已针对此事展开调查。《自然》杂志的论文也引起了环境调查署(EIA)的注意,这是一个反对环境犯罪和滥用的慈善机构。

“As soon as we read it… we realised it was a really big deal,” says Clare Perry, a campaigner at the agency.

"我们一读到它......就意识到这是一个非常重要的事情",该机构的活动家佩里(Clare Perry)说道。

She and her team immediately thought to look for potential sources of CFC-11 in China. Researchers contacted several Chinese companies that process chemicals or make products that could be insulated with foam containing bubbles of CFC-11. The responses were candid. A representative at one firm allegedly said, “We purchase CFC-11 and mix it up. You see, nobody comes to inspect our processing work.”

佩里和她的团队立即开始在中国寻找氟利昂的来源。研究人员联系了几家中国公司,它们都调配过化学品或是直接生产隔热用的泡沫材料, 这种材料中含有氟利昂。中国公司的答复很坦诚。一家公司的代表说:"我们购买氟利昂并混合使用。事实上,没有人会来检查我们的加工工作。"

In all, the EIA says it received indications from 18 companies that they use CFC-11 in some form, often when blowing insulating foam into appliances and buildings.

总的来说,环境调查署表示,已收到18家公司的回复,称他们皆以某种形式使用氟利昂,通常是在将绝缘泡沫吹入家用电器和建筑物时使用。

The challenge now is to prove that such activity can account for the additional volume of CFC-11 apparently being released every year: about 13 million kilograms, according to Montzka and his colleagues.

现在面临的挑战是,如何证明这就是氟利昂的排放来源:数量高达每年1300万公斤,蒙扎克及其同事表示。

“Sniffing the air” sounds simple, but the science involved in actually measuring molecules or particles in the atmosphere is a little more complex. The method used to detect the CFC-11 at Mauna Loa was gas chromatography, a process by which gases in a sample of air are separated along a long, coiled tube. As they’re blown along the tube, the rate at which they arrive at the other end is measured and compared. Larger particles, for instance, arrive more slowly than smaller ones. Mass spectrometry, the science of identifying molecules by their mass, is often used in conjunction with chromatography.

"嗅探空气"听起来很简单,但实际测量大气中分子或粒子的科学原理是十分复杂的。用于检测莫纳罗亚天文台中氟利昂的方法是气相色谱法(gas chromatography),这种方法将空气样本中的气体沿着长的盘管分离。当它们沿着管子飘动时,测量并比较它们到达另一端的速率。较大的颗粒比小的颗粒更慢地到达。质谱法是通过质量鉴定分子,通常与色谱法结合使用。

And then there’s the instrumentation needed to measure particulate, tiny clumps of solids or liquids that float around in the air.

然后是测量漂浮在空气中的微粒,微小团块,固体或液体所需的仪器。

This can be done by shining light through, say, a column of smoke and measuring how the light is scattered sideways off the particles. Tools that do this sort of measuring were unexpectedly put to the test this year, when a large wildfire broke out on Saddleworth Moor in the north of England in June. The fact that something was burning was no mystery – in fact, the fire was so large that a plume of smoke from it was easily visible from space.

通过将光线穿过一列烟雾,测量光线如何从粒子侧面散射,可完成这项任务。这种测量工具今年意外地得到了实际运用。在今年6月份,英格兰北部的萨德尔沃思沼泽(Saddleworth Moor)发生了一场大型野火,火势之大,从太空中都可以看到一股烟雾。

But how polluting was the fire? That’s something not discernible with the naked eye. To find out, a new array of instruments for measuring air quality at the University of Manchester were used. They revealed an extremely high concentration of particulate, which is highly polluting. The particulate comes from organic matter, vegetation, as it burns and smoulders. In fact, the lingering smouldering stage of a wildfire is when vast amounts of particulate matter are released.

但火灾造成了多少污染?肉眼无法辨认。为了找到答案,科学家使用了一组用于测量曼彻斯特大学空气质量的仪器。他们发现了浓度极高的微粒,都是高度污染物。颗粒来自有机物,植物,因为燃烧和阴燃产生。实际上,野草没有火焰、缓慢燃烧,释放出大量颗粒物质。

As with CFCs, part of the objective in keeping an eye on the atmosphere is to see whether countries are accurately reporting how much of a certain pollutant they have emitted in a given period. These declarations are often required as part of environmental protection regulations.

与氟氯化碳一样,关注大气环保,部分工作是观察各国是否准确报告了他们在特定时期内排放的某种污染物的数量。这通常是环境保护法规要求的。

Sometimes, this kind of double-checking yields good news.

有时候,这种观察和评估还会带来好消息。

Earlier this year, a paper reported that California appears to be accurately cataloguing its fossil fuel carbon dioxide (CO2) emissions. To check, co-author Heather Graven of Imperial College, London and her team used accelerator mass spectrometry to measure the ratio of different kinds of carbon in atmospheric CO2. Carbon-14 is a new, slightly radioactive carbon that is produced naturally in the atmosphere. Fossil fuel carbon has been around for many millions of years and has consequently decayed to become carbon-12, which has a slightly smaller mass and is no longer radioactive. Therefore, a lower ratio of carbon-14 to carbon-12 in the atmosphere is an indication that fossil fuel CO2 emissions are up.

今年早些时候,一篇论文认为,加利福尼亚似乎准确地报告了化石燃料二氧化碳(CO2)的排放量。为了核查,伦敦帝国理工学院的格雷文(Heather Graven)和她的团队使用加速器质谱法测量大气二氧化碳中不同种类碳的比例。碳14是一种新的轻微放射性碳,在大气中自然产生。化石燃料碳已存在数百万年,并因此腐烂成为碳12,其质量略小且不再具有放射性。因此,大气中碳14与碳12的比率较低表明化石燃料的二氧化碳排放量增加。

“From the data that we have, and incorporating atmospheric models, we found what we observed is very similar to what we expected,” says Graven.

"根据我们拥有的数据,并结合大气模型,我们发现我们观察到的与我们预期的非常相似",格雷文说。

“The atmospheric data is providing a tentative validation of what California is reporting.”

"借鉴大气测量数据,科学家正在对加利福尼亚报告中数据的准确性进行初步验证"。

What floats around in the air doesn’t just tell us about fossil fuel pollution or the release of banned chemicals – it can also reveal unreported activity with nuclear weapons and radioactive materials used in the nuclear energy industry.

大气悬浮颗粒不仅能显示化石燃料污染或禁用化学品的排放,还可揭示未被报告的核武器和核能工业中放射性物质的使用状况。

There is a worldwide radionuclide monitoring network that takes constant samples of the air in an effort to pick up unexpected radioactivity. After an above-ground nuclear accident or explosion, radioactive isotopes, or radionuclides, are released into the atmosphere and blown around by the wind. Stations all over the globe sample the air once a day and radiation detectors can tell exactly which isotopes are present.

世界范围的放射性核物质监测网络不断采集空气样本,以收集实时的放射性数据。地球上发生核事故或核试验之后,放射性同位素或放射性核物质被释放到大气中并被风吹散。全球各地的监测站每天对空气进行一次采样,辐射探测器可以确定有哪些同位素存在。

In October 2017, the French radiation safety authority (IRSN) disclosed that a strange, small spike in ruthernium-106 had been detected by several European networks.

2017年10月,法国核安全机构(IRSN)披露,一些欧洲监测网络检测到一种奇怪的放射性核元素——钌106(ruthernium-106)出现小高峰。

The IRSN was quick to determine that the levels wouldn’t be harmful to human health, but discovering this particular isotope was a worry, recalls Jean-Luc Lachaume at the IRSN.

法国核安全机构很快就确定,空气中如此浓度的钌106不会对人体健康产生危害,但发现这种特殊的同位素让人担忧,该机构的拉肖姆(Jean-Luc Lachaume)回忆道。

“This level of activity is totally unusual,” he says. “That radionuclide is an indicator of an incident or accident at a nuclear facility.”

"这种同位素的活动水平完全不同寻常",他说,"该放射物是核设施事故或意外所形成的。"

We know this because specific kinds of nuclear activity cause specific radionuclide releases. For example, you might expect to see some iodine-131 in the atmosphere, says Lachaume, because it is associated with radioactive materials used in hospitals. Ruthenium-106 is much rarer.

我们知道这一点,因为特定种类的核活动会导致特定放射物的溢出。拉肖姆举例说,你可能会在大气中看到一些碘131,因为它与医院使用的放射性物质有关。钌106却是十分罕见的。

Public information, including some found online, raised the suspicions of IRSN researchers that the source of the radionuclide was Mayak, an isotope plant in Russia, which had been due to produce cesium-144 in 2017. The industrial process for making that isotope would involve the creation of ruthenium-106. What’s more, analysis of wind patterns – much like the work done to investigate the source of CFC-11 – also suggested a place of origin in eastern Russia.

公共信息,包括一些在网上发现的信息,引起了法国核安全机构研究人员的怀疑:放射性核元素来自于玛雅克(Mayak),一座位于俄罗斯的同位素工厂。该工厂原定于2017年生产铯144。制造该同位素的过程会产生钌106。更重要的是,就像调查CFC-11的来源一样,研究人员对风力模型进行了分析,结果指向了俄罗斯东部。

Did an accident at Mayak cause the unintended release of ruthenium-106 into the skies over Europe?

是玛雅克工厂的事故导致了钌106在无意中被泄漏并散播到了欧洲吗?

When quizzed about it, Russian officials said there was no safety incident at Mayak to report. Lachaume has been left not knowing exactly what to think, given the lack of conclusive evidence that Mayak definitely was the source.

调查中,俄罗斯官员表示玛雅克并没有发生安全事故。由于缺乏确凿的证据表明玛雅克为其确切来源,拉肖姆一直不知道该如何做。

“There are some mysteries in the universe,” says Lachaume, “and this is one of them.”

"宇宙中有一些解不开的谜团",拉肖姆说,"我想这就是其中之一。"

But with scientists around the world ‘sniffing the air’, some mysteries are becoming easier to solve. In the wake of nuclear accidents or illegal, unreported emissions, these people are often the first to know – the first to reveal an otherwise invisible truth.

但随着世界各地的科学家们"嗅探空气",一些谜团变得越来越容易解决。在核事故或非法、未报告的排放之后,科学家们通常是第一个知道的,他们也是揭示这隐形真相的先驱。

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