Summertime HONO concentrations were synchronously measured at two (agricultural and nonagricultural) sites in the North China Plain (NCP). Daytime HONO (1.4 ± 0.6 ppbv) and HONO/NO₂ ((12 ± 8)%) over the agricultural field after fertilization were found to be remarkably higher than those before fertilization, implying strong HONO emission from the fertilized fields. Synchronous enhancements of HONO and O₃ after fertilization at both sites suggested that the emitted HONO accelerated the local and the regional O₃ pollution. HONO budget analysis further revealed that its emission was significantly enhanced after fertilization. Soil HONO emission flux and its uncertainty were estimated and discussed. The estimated emission flux exhibited a distinct diurnal variation with a noontime maximum. The net OH production rate from HONO photolysis greatly exceeded that from O₃ photolysis over the agricultural field, and their maximum ratio of 4.7 was obtained after fertilization. We provide field evidence that fertilized fields in the NCP act as a strong HONO source, which accelerates daytime photochemistry, leading to an increase of regional photo-oxidants such as O₃. Considering the severe O₃ pollution in the summer NCP and that the large area of the agricultural field is regularly treated with high fertilization amount in this region, HONO emission should be taken into account in the regional air quality deterioration.

中文翻译：

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华北平原夏季农田强烈HONO排放的证据及其对区域O ₃污染的显着影响

在华北平原（NCP）的两个（农业和非农业）地点同步测量了夏季的HONO浓度。发现施肥后农田的白天HONO（1.4±0.6 ppbv）和HONO / NO ₂（（12±8）％）显着高于施肥前的水平，这表明施肥田地强烈释放出HONO。两个地点施肥后HONO和O _3的同步增强表明，所释放的HONO加速了本地和区域性O ₃污染。HONO预算分析进一步表明，施肥后其排放显着增加。估算并讨论了土壤HONO的排放通量及其不确定性。估计的排放通量表现出明显的昼夜变化，其中午间时间最大。在农田上，HONO光解的净OH生成速率大大超过了O ₃光解的OH生成速率，施肥后其最大比例为4.7。我们提供的田间证据表明，NCP中的施肥田地是强大的HONO来源，可加速白天的光化学反应，从而导致区域性光氧化剂（例如O _3）增加。考虑到严重的O ₃ 夏季NCP污染严重，并且该地区大面积农田受到高施肥量的定期处理，因此在区域空气质量恶化时应考虑HONO排放。