Abstract As an important component of anthropogenic emissions, nitrogen oxides (NOx) are well known to interfere with daytime oxidation of biogenic volatile organic compounds (BVOCs) and secondary organic aerosol (SOA) formation. Nighttime chemistry is highly related to O3 and NOx level but, NOx effects on SOA formation from the ozonolysis of BVOCs, especially polyolefinic monoterpenes, have not been well understood. In the present study, SOA formation from pure and NOx-involved γ-terpinene ozonolysis was studied in a smog chamber under dark conditions. At atmospherically relevant particle mass loading of 10 μg m−3, the SOA yield from pure ozonolysis is estimated by a two-product model to be 8.6%. When NOx were incorporated into γ-terpinene ozonolysis, both the particle size and SOA yields increased simultaneously with elevated NOx mixing ratios. SOA yields doubled (from 0.38 to 0.77) when the system moved from NOx-free to [γ-terpinene]0/[NOx]0 = 3.5 (ppbC/ppb). The characteristic absorption of organic nitrates was detected by Fourier transform infrared (FTIR) spectroscopy and the fraction of organic nitrates increased with increasing NOx mixing ratios. Identification of the new constituents in SOA from NOx-involved γ-terpinene ozonolysis and their formation channels suggest that the formation of organic nitrates follows NO3 chemistry. NOx affects γ-terpinene ozonolysis via the enhanced generation of NO3 at high NOx and its subsequent more favored consumption of γ-terpinene than O3. The first-generation products from NO3 oxidation of γ-terpinene could be further oxidized by ozone, forming more oxidized products that contribute to SOA formation. Our investigation suggests that at night with high NOx levels, γ-terpinene may be a significant source of SOA and organic nitrates through anthropogenic-biogenic interactions.

中文翻译：

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NOx 增强了夜间 γ-萜品烯臭氧分解产生的二次有机气溶胶形成

摘要 作为人为排放的重要组成部分，众所周知，氮氧化物 (NOx) 会干扰生物挥发性有机化合物 (BVOC) 的白天氧化和二次有机气溶胶 (SOA) 的形成。夜间化学与 O3 和 NOx 水平高度相关，但是，NOx 对 BVOC，尤其是聚烯烃单萜的臭氧分解对 SOA 形成的影响尚未得到很好的理解。在本研究中，在黑暗条件下的烟雾室中研究了由纯和 NOx 参与的 γ-萜品烯臭氧分解形成的 SOA。在大气相关粒子质量负载为 10 μg m-3 时，纯臭氧分解的 SOA 产量通过双产品模型估计为 8.6%。当 NOx 加入 γ-萜品烯臭氧分解时，随着 NOx 混合比的升高，颗粒尺寸和 SOA 产量同时增加。当系统从无 NOx 变为 [γ-萜品烯]0/[NOx]0 = 3.5 (ppbC/ppb) 时，SOA 产量翻倍（从 0.38 到 0.77）。通过傅里叶变换红外 (FTIR) 光谱检测有机硝酸盐的特征吸收，有机硝酸盐的比例随着 NOx 混合比的增加而增加。从与 NOx 相关的 γ-萜品烯臭氧分解及其形成通道中识别 SOA 中的新成分表明，有机硝酸盐的形成遵循 NO3 化学。NOx 通过在高 NOx 下增强 NO3 的生成以及随后更倾向于消耗 γ-萜品烯而不是 O3 来影响 γ-萜品烯臭氧分解。γ-萜品烯 NO3 氧化的第一代产物可以被臭氧进一步氧化，形成更多的氧化产物，有助于 SOA 的形成。