辛达雅思代报考位，雅思代报名截止前提醒广大考生抓紧时间报名，欢迎前来咨询在线客服。

       Blackest day

　　ON January 12th of last year, in an article in the print edition of The Economist, we reported that the public outcry over Beijing’s atrocious air quality was putting pressure on officials to release more data about more kinds of pollutants. We also noted that Chinese authorities had already embarked on a wide range of strategies to improve air quality, and that they probably deserve more credit than either foreign or domestic critics tend to give them. But we concluded with the sad reality that such work takes decades, and that “Beijing residents will need to wait before seeing improvements.”

　　On January 12th of this year, Beijing residents got an acrid taste of what that wait might be like, as they suffered a day of astonishingly bad air. Pollution readings went, quite literally, off the charts. Saturday evening saw a reading of 755 on the Air Quality Index (AQI). That index is based on the recently revised standards of the American Environmental Protection Agency (the EPA), which nominally maxes out at 500. For more perspective, consider that any reading above 100 is deemed “unhealthy for sensitive groups” and that anything above 400 is rated “hazardous” for all.

　　Like many Beijing residents, your correspondent has mobile-phone apps that keep up with the pollution readings. At an otherwise pleasant Saturday-evening meal with friends, he joined his companions in compulsively checking for updates.

Those previously unseen numbers were hard to believe, but they did seem to match up well enough with the noxious soup we could see, smell and taste outside. We are all far more familiar with the specifics of air-quality measurement than we would like to be. Apart from the AQI readings above 700, we were quite struck to see the readings for the smallest and most dangerous sort of particulate matter, called PM 2.5, which can enter deep into the respiratory system. These are named for the size, in microns, of the particles. A reading at a controversial monitoring station run by the American embassy showed a PM 2.5 level of 886 micrograms per cubic metre; Beijing’s own municipal monitoring centre acknowledged readings in excess of 700 micrograms.

　　For perspective on that set of figures, consider that the guideline values set by the World Health Organisation regard any air with more than 25 micrograms of PM 2.5 per cubic metre as being of unacceptable quality.

　　Chinese authorities have complained about the American embassy's insistence on independently monitoring—and publicly reporting—Beijing’s air quality. And sometimes much is made of the vast differences between those readings and China’s own official ones, which are often less dire. Indeed, a key feature of one of those mobile-phone apps is the side-by-side comparison of those competing data-sets. (It is of course a bad sign that people here need more than one app to keep up with all this.)

　　But on a day like Saturday, the discrepancy between official readings and independent ones hardly seemed to matter; you didn't need a weatherman to know which way the ill wind blew. Or failed to blow, as the case may have been. One expert quoted by Chinese media attributed this spike in pollution to a series of windless days that allowed pollutants to accumulate.

But wind can be a problem when it does blow, too. In the outlying provinces that are part of Beijing’s airshed, there is a great deal of heavy industry. Pollution regulations are much harder to enforce there. And, in this colder-than-average winter, people have been burning more coal and wood than usual.

　　It is likely to be many more Januarys to come before China gets the upper hand on its air-pollution problems. Indeed, as we mentioned last January 12th, after nearly sixty years of trying and a vast amount of progress, the city of Los Angeles has yet to meet America's federal air-quality standards. If there is any consolation to what Beijing had to endure this January 12th, it is that it should lend urgency to the public outcry, and help speed things in the right direction.

　　The other consolation is that readings like the ones showing now on Monday midday (in the mid 300s, merely “hazardous” and “severely polluted”) feel fine by comparison.

　　参阅译文：

　　北京空气污染——最漆黑的一天

　　上一年1月12日，咱们在印刷版的《经济学人》中报导了大众关于北京恶劣空气质量的呼吁迫使官方发布更多品种污染物数据一事。咱们也注意到我国政府开端着手于采用多种战略来进步空气质量，因而他应该遭到来自国外或许国内评论家更多的信赖。但令人懊丧的现实是，这些工作需求花费数十年来完结，“在情况有所改观曾经，北京居民还需等候少许时日。”

　　本年1月12日，北京居民的等候换来的却是辛辣的感觉，由于他们阅历了空气质量出奇恶劣的一天。毫不夸大地，污染物读数飙升，超越了记载。星期六晚上，空气质量指数为755.这个指数是依据美国环境保护署最近修正的规范，名义上的最大值为500.有更多观念以为，指数只需高出100就会“不利于灵敏人群的健康”，高出400的话，就会对所有人“有风险”。

　　像许多北京居民相同，咱们记者的移动手机应用程序能够时间更新污染指数。本应该是一次和朋友团聚其乐融融的周六晚餐，他却与火伴们不断地查看着数据的更新。

　　从前没有看到的那些数字有些难以置信，可是从咱们看到闻到外面稠密的毒雾来判别，应该也差不多。尽管咱们不肯供认，但咱们对测量空气质量的细节心知肚明。除了空气质量指数超越700之外，PM 2.5——空气中最小但最风险并能够进入呼吸系统的一种悬浮颗粒——的读数让咱们十分震动。它们是依照粒子微米下的体积来命名的。来自一座有争议的美国大使馆监测站的数据显现，PM 2.5的水平达到了886微克每立方米;北京市当地检测中心供认数据超越了700微克。

依据这一组数据，有观念以为，依据世界卫生组织指定的辅导值，但凡PM 2.5高于25微克每立方米，即被以为是不能接受的空气质量。

　　我国官方一向就美国大使馆对北京空气质量坚持独自检测并发布表明诉苦。有时分，美国的指数会与我国官方的有很大差异，我国的通常会相对平缓一些。的确，移动手机应用的主要特征之一就是那些相互竞争的数据搜集站的平行比较。(当然，这儿的人们需求不止一个应用程序来更新这些数据，这并不是个好的现象。)

　　可是在这样一个星期六，官方的数据与独立监测站之间的差异也显得不重要了;你也不需求气候员来通知你污浊的气体是朝哪边吹的。或许说，事实上是底子没有在活动。引用我国媒体的报导，一位专家将这次污染指数爆表归罪于接连几天无风导致的污染物积累。

　　可是当起风的时分，也会出现问题。在北京气流区域的边远省份有许多重工业。这些区域的污染管理更难实施。此外，在这个比平时要冰冷的冬天，人们烧了更多的煤和木柴。

　　看来，我国还需求许多年才能在空气质量问题上有所成效。的确，正如咱们在上一年1月12日说到的那样，洛杉矶经过大约六十年的尽力和很多开展才达到了美国联邦空气规范。假如说对北京在这个1月12日有必要接受的压力有少许安慰的主张，那就是北京应该更为急迫地应对民众呼吁，而且促进事物往正确的方向开展。

　　另一个安慰就是像星期一正午发布的指数(大约300过半，仅仅是“对人风险的”和“严峻污染”)在相比之下就容易接受多了。