Nitrogen isotopes (δ¹⁵N) can trace sources of major inorganic NO_y species (here referring to nitrogen dioxide (NO₂), nitric acid (HNO₃), and nitrate (NO₃^–)) in the atmosphere. However, δ¹⁵N variations during transformation and deposition processes of NO_y species remain poorly understood. Here, we dissected δ¹⁵N differences between NO₂, HNO₃, particulate NO₃^–, and precipitation NO₃^– by converging observations of their concentrations and δ¹⁵N from literature sources. δ¹⁵N values of HNO₃ were higher by 6.9 ± 4.6‰ than those of NO₂, indicating that the hydroxyl radical pathway dominated the HNO₃ formation. δ¹⁵N values of particulate NO₃^– were higher by 4.9 ± 4.2‰ than those of HNO₃, indicating HNO₃ as a main precursor of particulate NO₃^–. δ¹⁵N values of precipitation NO₃^– were lower than those of HNO₃ (by 2.8 ± 3.3‰) and particulate NO₃^– (by 7.5 ± 3.5‰) but higher than those of NO₂ (by 5.1 ± 4.5‰). Relative contributions of NO₂, HNO₃, and particulate NO₃^– to precipitation NO₃^– were estimated as 45 ± 10%, 32 ± 5%, and 23 ± 7%, respectively, which differed from their fractions in ambient atmosphere (57 ± 14%, 14 ± 8%, and 29 ± 11%, respectively). This revealed NO₂ as an important precursor of precipitation NO₃^– and a preferential scavenger of HNO₃ by precipitation. This work is beneficial for more accurate evaluations on sources and processes of atmospheric NO_y pollutants.

中文翻译：

---

主要大气NO _y物种之间的氮同位素差异：对转化和沉积过程的影响

氮同位素（δ ¹⁵ N）可以跟踪主要无机NO的来源_Ý物种（在这里指的是二氧化氮（NO ₂），硝酸（HNO ₃）和硝酸（NO ₃ ^- ））在大气中。然而，δ ^15个中NO转化和沉积工艺Ñ变化_ÿ物种仍知之甚少。在这里，我们解剖δ ¹⁵ Ñ差异NO之间₂，HNO ₃，微粒NO ₃ ^- ，和沉淀NO ₃ ^-由会聚它们的浓度的和δ观测¹⁵N来自文献资料。δ ¹⁵ HNO的N个值₃分别为6.9±4.6‰比NO的较高₂，表明该羟基自由基途径支配的HNO ₃的形成。δ ^15个微粒NO的N个值₃ ^-分别为4.9±4.2‰比HNO的更高₃，表明HNO ₃作为颗粒NO的主要前体₃ ^- 。δ ^15个沉淀NO的N个值₃ ^-均较HNO的下部₃（2.8±3.3‰）和颗粒NO ₃ ^-（7.5±3.5‰）但高于那些NO的₂（5.1±4.5‰）。NO的相对贡献₂，HNO ₃，和微粒NO ₃ ^-以沉淀NO ₃ ^-被估计为分别为45±10％，32±5％和23±7％，这从它们在环境气氛馏分差异（57 ±14％，14±8％和29±11％）。这揭示NO ₂作为沉淀的一种重要前体NO ₃ ^-和HNO的优选清除剂₃通过沉淀。这项工作有助于更准确地评估大气中NO _y污染物的来源和过程。