亚硝酸（HONO）光解是室内大气OH自由基重要来源，精准解析白天HONO来源对于研究室内空气氧化能力至关重要。近期高精度观测发现室内环境日间HONO浓度测量值远高于预期，其对OH的贡献也被低估。室内环境HONO实测值和光化学模型估算值之间的巨大差异，昭示其室内生消过程的科学认识有待深入。本项目拟重点探讨室内表面附着有机质与NO2光化学非均相反应对日间HONO的潜在贡献。拟在典型时段采集日照和背阴处尘垢，采用流动管技术模拟研究NO2光照时与室内表面非均相反应生成HONO的动力学过程、反应产物与机制途径。同时，通过真实室内环境中NOx、HONO和VOCs同步在线测量，将HONO测量值与NO2与室内表面有机质非均相反应生成的HONO水平相比较，在此基础上发展并应用零维模式模拟氮素再活化过程对广州室内空气质量潜在影响。项目研究有助于深入认识室内环境HONO日间未知源以及氮化学和氧化过程。

Nitrous acid (HONO) is the most important precursor of hydroxyl radical (OH) in indoor air. Attributing sources of HONO during daytime is of great importance for improving understanding of oxidation capacity of the indoor atmosphere. However, recent field measurements in real-life indoor environments using very sensitive HONO instruments have shown that daytime HONO concentrations are much higher than previously assumed and that the contribution of HONO to the OH radical formation was underestimated in the past. The scientific knowledge about these processes is still in its infancy and there is still a huge discrepancy between the field measurements and the photochemical models. .This project will focus on light-induced (photosensitized) heterogeneous processing of adsorbed organic material on indoor surfaces by gas-phase NO2 as a potential source of daytime HONO in indoor environments. The grime will be firstly collected on glass plates over various collection time in direct sunlight and in the shade of the room. The glass plates will be then inserted in a horizontal flow tube photo-reactor to investigate kinetics, reaction products and mechanistic pathways of HONO formation from the NO2 light-induced heterogeneous processes under laboratory conditions. Meanwhile, time-resolved measurements of NOx, HONO, and VOCs will be performed in real-life indoor environments to compare with the HONO levels emerged from light-induced heterogeneous reactions of NO2 with the organic content of the indoor surfaces. The compared results will be implemented in the 0D model especially developed for this purpose to simulate the impact of renoxification processes on the indoor air quality in Guangzhou. The studies will shed new insights into the “missing source” of HONO during daytime and benefit understanding the nitrogen chemistry and oxidation processes in the indoor atmosphere.