Ambient particulate matter significantly impacts air quality, climate, and human health. In the Indo-Gangetic Plain (IGP), home to nearly one-seventh of the global population, severe air pollution is prevalent with high PM_2.5 levels dominated by organic aerosols (OA). However, the sources and formation of OA pollution remain poorly constrained. For the first time, we characterize OA sources in two cities, Delhi and Kanpur in the IGP, over an entire year by combining near-molecular characterizations using an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF) combined with advanced statistical approaches. We identified three key local biomass burning sources—affected by various fuels such as wood, straw, and cow dung—that had a more pronounced impact on Kanpur (66 %) compared to Delhi (35 %), particularly during colder months. Additionally, we identified transported agricultural fire emissions from Northwest India, which significantly contributed to OA during the post-monsoon rice harvest season, playing a critical role in haze formation. Acute mortality estimates indicated that while urban OA sources were substantial, rural crop residue burning posed a notable health risk during the post-monsoon, accounting for 32 % of PM_2.5-attributable mortality in Delhi and 53 % in Kanpur. These results highlight the need for coordinated air pollution mitigation strategies that extend beyond urban centres to a regional scale, with a particular focus on crop residue management in Punjab to reduce the health burden of PM_2.5 pollution in the IGP.

中文翻译：

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季风过后，印度北部城市焚烧农作物残茬产生的烟雾是有机气溶胶的主要来源和健康风险

环境颗粒物对空气质量、气候和人类健康有重大影响。在拥有全球近七分之一人口的印度恒河平原 （IGP） 地区，严重的空气污染普遍存在，有机气溶胶 （OA） 以高 PM _2.5 水平为主。然而，OA 污染的来源和形成仍然受到很好的限制。我们首次通过使用萃取式电喷雾电离飞行时间质谱仪 （EESI-TOF） 结合先进的统计方法将近分子表征相结合，在一整年的时间里表征了 IGP 中德里和坎普尔两个城市的 OA 源。我们确定了三个关键的当地生物质燃烧源——受木材、稻草和牛粪等各种燃料的影响——与德里 （35%） 相比，它们对坎普尔 （66%） 的影响更为明显，尤其是在较冷的月份。此外，我们还确定了印度西北部运输的农业火灾排放物，这在季风后水稻收获季节对 OA 有重大贡献，在雾霾形成中起着关键作用。急性死亡率估计表明，虽然城市 OA 来源很大，但在季风后，农村作物残留物焚烧构成了显着的健康风险，占德里 PM _2.5 归因死亡率的 32%，占坎普尔的 53%。这些结果突出表明，需要制定协调一致的空气污染缓解策略，从城市中心扩展到区域范围，特别关注旁遮普邦的作物残留物管理，以减轻 IGP 中 PM _2.5 污染的健康负担。