High light：Ethyne is the lightest of the non-methane hydrocarbons, whose oxidation product, glyoxal, is an important precursor of secondary organic aerosol. This study explores the effects of relative humidity on the formation of secondary organic aerosol under irradiation in the presence of nitrogen oxides and sodium chloride. Results show that relative humidity can enhance aerosol formation, which provides evidence of the contribution of ethyne to organic particles.
FTIR spectra of SOA from ethyne
The heterogeneous photochemical oxidation of ethyne was investigated under different relative humidity (RH) conditions in the presence of nitrogen oxides and sodium chloride in a self-made indoor smog chamber. The purpose was to study the influence of RH on the formation of secondary organic aerosol (SOA) from C2H2. Through the experiments, we found that SOA was rarely formed at <22% RH in the presence of NaCl seed particles, and that SOA began to be formed at ≥29 % RH in the presence of NaCl, which shows the importance of RH in the formation of SOA. The yield of SOA (YSOA) from C2H2 was 0.2 % at 51 % RH, and increased by a factor of 17.5 as RH reached 83%. The SOA yield increased with increasing RH. The geometric mean diameter of the particles increased by a factor of 1.17, 1.22, 1.28 and 1.51 at a RH of 51, 63, 74 and 83% respectively at the end of the experiment, indicating that the growth of the particle size also increased with increasing RH. Analysis of the SOA with Fourier-transform infrared (FTIR) spectrometry indicated that the particles generated from C2H2 contained the functional groups –OH, C=O, C–O–C and C–C–OH, for whose absorption peaks increase with increasing RH.
Ge Shuangshuang, Xu Yongfu, Jia Long (2016) Secondary organic aerosol formation from ethyne in the presence of NaCl in a smog chamber. Environmental Chemistry 13, 699-710.
The formation of ozone and secondary organic aerosol (SOA) from ethylene-NO x -NaCl(aerosol) irradiations was studied under various relative humidity (RH) conditions in an indoor smog chamber. In the absence of NaCl seed aerosols, SOA was hardly formed and peak O3 concentrations decreased linearly with increasing RH in ethylene irradiations. For the irradiations with NaCl seed aerosols, when RH <48% (efflorescence relative humidity of NaCl), NaCl existed as solid phase and had little effect on peak O3 concentrations. The infrared spectra from sampled particles showed that SOA was rarely formed on solid NaCl particles. However, when NaCl was in the aqueous phase as RH ≥ 48%, the peak O3 concentration was sharply reduced by over 20 % as compared to experiments without NaCl aerosol, and the absorption of NaNO3 in aerosols was coincidently increased with RH. Model results indicated that the heterogeneous reaction of N2O5 with aqueous NaCl aerosols was the main cause for the sharp decrease of O3. Besides, the absorptions from C-H, C = O, ONO2 and COO groups all greatly increased with RH. Our results show that SOA from ethylene-NOx irradiations was mainly formed through aqueous reactions. The yields of SOA from ethylene were measured to be 1.5 and 2.3% at RH of 65 and 84%, respectively.
Jia, L.; Xu, Y. Ozone and secondary organic aerosol formation from Ethylene-NOx-NaCl irradiations under different relative humidity conditions. J. Atmos. Chem. 2016, 73(1):81-100; doi:10.1007/s10874-015-9317-1
摘要：氧化镁(MgO)是大气中矿物气溶胶的重要组分之一, 对二次污染物的形成有着重要影响. 本研究采用原位漫反射红外傅里叶变换光谱(DRIFTS)与离子色谱(IC)技术, 研究了二氧化氮(NO2)在MgO颗粒表面的非均相反应. 探讨了无光照、紫外光照、臭氧(O3)、温度及相对湿度(RH)等对该反应的影响机制, 建立了新的测定摄取系数的方法. 结果表明, 无光照时, NO2在MgO颗粒表面生成的主要产物为硝酸盐和亚硝酸盐; 在NO2-MgO-O3和NO2-MgO-hn两种反应体系中主要产物均为硝酸盐, 生成的硝酸根峰面积分别是无光照条件下的1.54倍和3.04倍, O3和紫外光照对硝酸盐的生成均具有促进作用; 在紫外光照条件下, NO2在MgO颗粒物表面生成硝酸根的初始速率随温度的升高而呈单峰变化, 40℃时初始速率最大; 影响NO2与MgO颗粒物反应的敏感因素为紫外光照和臭氧, 其次为相对湿度和温度. 在25℃, RH为5%时, 无光照条件和紫外光照条件下反应初始摄取系数分别为9.01×10-4和5.65×10-3.
韩力慧, 陈媛媛, 贾龙, 程水源, 徐永福,等. NO2在MgO颗粒物表面的非均相反应. 中国科学 化学, 2014, 44(12),2004-2012
Heterogeneous reactions of NO2 on the surface of MgO particles
Abstract：MgO is one of the most important components of mineral aerosol, and it has an important influence on the formation of secondary pollutants. The heterogeneous reaction of NO2 on MgO particles was studied using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and ion chromatography (IC). The influences of no ultraviolet radiation(UV), ultraviolet radiation(UV), ozone (O3), temperature and relative humidity (RH) on the reaction were investigated. A new method has firstly been established to determine uptake coefficients. The main products from the heterogeneous reaction of NO2 on MgO particles were nitrate and nitrite without UV. In NO2-MgO-O3 and NO2-MgO-hv reaction systems, the main product was nitrate, and its infrared adsorption peak areas were 1.54 and 3.04 times higher than that without UV, respectively. O3 and UV were in favor of the formation of nitrate. The initial rate of nitrate, due to the rise of temperature, showed a unimodal pattern with the maximum initial rate at 40℃ under UV. More sensitive factors affecting the reaction of NO2 on MgO particles are UV and ozone, followed by relative humidity and temperature. The initial reactive uptake coefficients of NO2 on MgO particles were determined to be 9.01×10-4 without UV and 5.65×10-3 with UV at 25℃ and 5% RH.
HAN LiHui, CHEN YuanYuan, JIA Long, CHENG ShuiYuan, XU YongFu,et al. Heterogeneous reactions of NO2 on the surface of MgO particles. Scientia Sinica Chimica, 2014, 44(12),2004-2012.
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