Nitrous acid (HONO) is a precursor of the hydroxyl radical in the atmosphere, which controls the degradation of greenhouse gases, contributes to photochemical smog and ozone production, and influences air quality. Although biomass burning is known to contribute substantially to global aerosols and reactive gas emissions, pyrogenic contributions to HONO emissions are poorly constrained and often omitted in models. Here we present a global survey of TROPOMI/Sentinel-5 Precursor satellite sounder observations and show that HONO emissions are consistently enhanced in fresh wildfire plumes. Comparing major ecosystems (savanna, grassland, shrubland and tropical and extratropical forests), we found that the enhancement ratios of HONO to nitrogen dioxide varied systematically with biome type, with the lowest in savannas and grasslands and highest in extratropical evergreen forests. Supported by airborne measurements, we demonstrate that previous assessments underestimate pyrogenic HONO emissions by a factor of 2–4 across all ecosystem types. We estimate that HONO emissions are responsible for two-thirds of the hydroxyl radical production in fresh wildfire plumes worldwide and act to accelerate oxidative plume chemistry and ozone production. Our findings suggest that pyrogenic HONO emissions have a substantial impact on atmospheric composition, which enhances regional ozone levels by up to 7 ppbv.

亚硝酸（HONO）是大气中羟基自由基的前体，它控制温室气体的降解，有助于产生光化学烟雾和臭氧，并影响空气质量。尽管已知生物质燃烧对全球气溶胶和反应性气体的排放有很大贡献，但热能对HONO排放的贡献受到的约束很有限，并且在模型中经常被忽略。在这里，我们对TROPOMI / Sentinel-5前体卫星测深仪进行了一次全球调查，结果表明，新鲜野火烟羽中HONO的排放量不断增加。比较主要生态系统（稀树草原，草地，灌木林以及热带和热带森林），我们发现HONO对二氧化氮的增强率随生物群落类型而系统地变化，在稀树草原和草原中最低，而在温带常绿森林中最高。在空中测量的支持下，我们证明了先前的评估在所有生态系统类型中低估了热源性HONO排放量的2-4倍。我们估计，HONO的排放量占全球新鲜野火烟羽中羟基自由基产量的三分之二，并起到加速氧化烟羽化学和臭氧生产的作用。我们的发现表明，热解HONO的排放对大气成分具有重大影响，从而将区域臭氧水平提高了7 ppbv。我们估计，HONO的排放量占全球新鲜野火烟羽中羟基自由基产量的三分之二，并起到加速氧化烟羽化学和臭氧生产的作用。我们的发现表明，热解HONO的排放对大气成分具有重大影响，从而将区域臭氧水平提高了7 ppbv。我们估计，HONO的排放量占全球新鲜野火烟羽中羟基自由基产量的三分之二，并起到加速氧化烟羽化学和臭氧生产的作用。我们的发现表明，热解HONO的排放对大气成分具有重大影响，从而将区域臭氧水平提高了7 ppbv。