Scientists said Wednesday they have solved the perplexing puzzle of how a major smog component, known as sulfate, forms during haze events in northern China, including Beijing.

　　周三，科学家称已经解决了形成包括北京在内的中国北部雾霾天气的一种重要的被称作硫酸盐的雾霾成分的形成谜团。

　　The study, published in the US journal Science Advances, identified reactive nitrogen chemistry and water particles in the air as the two missing pieces, suggesting that reducing nitrogen oxide (NOx) emission in particular may help curb China’s air pollution.

　　这项发布在美国期刊《科学进展》上的研究，认定活性氮化学物质和空气中的水分子是两大缺失部分，这暗示着，尤其是减少氮氧化物(NOx)排放可能有助于遏制中国的空气污染。

　　The findings were based on an analysis of the January 2013 winter haze event in Beijing, one of the worst atmospheric pollution events ever recorded in China, which saw the daily concentration of fine particle called PM2.5 exceed the World Health Organization guideline value by 16 times.

　　这项研究发现基于2013年1月发生在北京的冬季雾霾，这是中国史上最糟糕的大气污染事件之一，据观测，被称作PM2.5的微粒日浓度超过世界健康组织指南的16倍。

　　At that time, researchers performed aerosol measurements on the roof of a Tsinghua University building in Beijing and analyzed data throughout the surrounding regions.

　　当时，研究人员在北京清华大学建筑物的屋顶进行了气溶胶测量，并分析了周围地区的数据。

　　They identified a reaction pathway that could account for the missing source of sulfate, discovering that fine water particles in the air acted as an reactor, trapping sulfur dioxide (SO2) molecules and interacting with nitrogen dioxide (NO2) to form sulfate.

　　他们确定了一种可以解释硫酸盐缺失来源的反应途径，发现空气中的微粒充当反应器，捕获二氧化硫(SO2)分子并与二氧化氮(NO2)相互作用形成硫酸盐。

　　The reaction rate was further facilitated by stagnant weather in the 2013 haze event, which trapped NO2 near the Earth’s surface, resulting in NO2 concentrations that were three fold higher than clean conditions.

　　2013年雾霾事件期间，由于停滞的气候，这一过程的反应速率进一步增加了，这使得地球表面的二氧化氮被困住，造成二氧化氮浓度是清洁条件下的三倍。

　　This process, according to the researchers, was "self-amplifying," as increasing aerosol mass concentrations led to higher aerosol water content -- accelerating the accumulation of sulfate and causing more severe haze pollution.

　　据研究员，这一过程是“自我放大的”， 气溶胶质量浓度越高，气溶胶含水量越高，加速了硫酸盐的积聚，造成更加严重的雾霾天气。

　　"This study unfolds the unique sulfate formation mechanism in NCP (North China Plain) haze events, which differs from traditional scenarios," study author Guangjie Zheng of Tsinghua University said in an email to Xinhua.

　　研究作者清华大学郑广杰在给新华社的邮件中写道：“这一研究揭露了中国北部平原地区雾霾事件独特的硫酸盐形成机制，这和传统情景不一样。”

　　"In cleaner environments such as the US or Europe, sulfate is mainly formed through the traditional OH (hydroxide) reaction pathways in atmospheric gas phase, or the H2O2 (hydrogen peroxide) and O3 (Ozon) reaction pathways in cloud chemistry. In NCP haze events, however, the dominant sulfate formation pathway shifts into the NO2 reaction pathway in aerosol water."

　　“在美国或者欧洲这种更加清洁的环境中，硫酸盐主要通过传统的大气气相中的OH(氢氧化物)反应途径或云化学中的H 2 O 2(过氧化氢)和O 3(Ozon)反应途径形成。然而，在中国北部雾霾事件中，主要的硫酸盐形成途径变成了气溶胶水中的NO 2反应途径。”

　　Zheng said results in this research reveal "the complex nature" of haze pollution events in China.

　　郑说，这项研究的结果揭示了中国雾霾污染事件的“复杂本质”。

　　"The SO2 comes mainly from power plants, NOx is from power plants and mobile vehicles, while the NH3 (ammonia) and mineral dusts, which serve as the neutralizing substances, are from both natural and anthropogenic emissions such as industry and fugitive dusts," she said.

　　她说：“SO2主要来自发电厂，NOx来自发电厂和移动车辆，而作为中和物质的NH3(氨)和矿物粉尘来自自然和人为排放，如工业和扬尘。”

　　"These pollutants from various sources were emitted in high intensity at the same time, resulting in the unique heavy haze conditions, and thus the shifting in the dominant sulfate formation pathway. The complexity of haze pollutions in NCP further illustrated the importance of scientific emission-reduction strategies."

　　“这些污染物来自各种同时高浓度排放的源头，造成独特的重雾霾情况，因此造成主要的硫酸盐形成途径的转变。中国北部平原雾霾污染的复杂性进一步表明了科学减排战略的重要性。”

（编辑：何莹莹）