Halogen atoms affect the budget of ozone and the fate of pollutants such as hydrocarbons and mercury. Yet their sources and significances in polluted continental regions are poorly understood. Here we report the observation of unprecedented levels (averaging at 60 parts per trillion) of bromine chloride (BrCl) at a mid-latitude site in North China during winter. Widespread coal burning in rural households and a photo-assisted process were the primary source of BrCl and other bromine gases. BrCl contributed about 55% of both bromine and chlorine atoms. The halogen atoms increased the abundance of ‘conventional’ tropospheric oxidants (OH, HO₂ and RO₂) by 26%–73%, and enhanced oxidation of hydrocarbon by nearly a factor of two and the net ozone production by 55%. Our study reveals the significant role of reactive halogen in winter atmospheric chemistry and the deterioration of air quality in continental regions where uncontrolled coal combustion is prevalent.

中文翻译：

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一个意想不到的大型大陆活性溴和氯源，对冬季空气质量有重大影响

卤素原子会影响臭氧的平衡以及碳氢化合物和汞等污染物的归宿。然而，人们对它们在受污染大陆地区的来源和意义知之甚少。在这里，我们报告了冬季在华北中纬度地区观察到的前所未有的氯化溴 (BrCl) 水平（平均为万亿分之 60）。农村家庭中广泛燃烧的煤和光辅助过程是 BrCl 和其他溴气体的主要来源。BrCl 贡献了大约 55% 的溴和氯原子。卤素原子增加了“常规”对流层氧化剂（OH、HO ₂和 RO ₂) 增加 26%–73%，碳氢化合物的氧化增加了近两倍，臭氧的净产量增加了 55%。我们的研究揭示了活性卤素在冬季大气化学中的重要作用以及普遍存在不受控制的煤炭燃烧的大陆地区空气质量的恶化。