Heterogeneous reactions play an essential role in the research area of formation processes of secondary aerosols. In this study, heterogeneous reactions of NH₃/SO₂/NO₂ with α-Fe₂O₃ particles at different relative humidities (RHs) were investigated by using a gas-flow system combined with diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The results show that the presence of NH₃ leads to the rapid conversion of SO₂ to sulfate as a result of the proton transfer function and neutralization on the α-Fe₂O₃ particles in dry condition. NH₃ can also promote the hydrolysis of NO₂ dimers to HONO formation and result in the formation of more sulfate on the particle surface in humid conditions. On the other hand, water vapor plays both positive and negative roles in the uptake of SO₂ during the reaction processes. When the RH increases from 0% to 62%, the formation rate of sulfate and uptake coefficient for SO₂ in the initial stage increase about 3-fold. However, due to the inhibition effect of water layer between trace gases and active surface, the above values of reaction kinetic decrease about 21% when the RH increases from 62% to 72%. Our results may provide insight into the effects of NH₃ and RH for the converting SO₂ into sulfate on α-Fe₂O₃ particles, which supply basic data for the formation of secondary particles in field studies of atmospheric environment.

非均相反应在二次气溶胶形成过程的研究领域发挥着重要作用。在这项研究中，NH ₃ /SO ₂ /NO ₂与α-Fe ₂ O ₃颗粒在不同相对湿度（RHs）下的多相反应通过使用气流系统结合漫反射红外傅立叶变换光谱（DRIFTS）进行了研究. 结果表明，NH ₃的存在导致SO ₂快速转化为硫酸盐，这是干燥条件下α-Fe ₂ O ₃颗粒上的质子传递函数和中和作用的结果。NH ₃还可以促进 NO ₂二聚体水解成 HONO，并导致在潮湿条件下在颗粒表面形成更多的硫酸盐。另一方面，水蒸气在反应过程中对 SO ₂的吸收起着积极和消极的作用。当相对湿度从0%增加到62%时，初期硫酸盐生成率和SO ₂吸收系数增加约3倍。然而，由于微量气体与活性表面之间水层的抑制作用，当相对湿度从62%增加到72%时，上述反应动力学值下降约21%。我们的结果可以深入了解 NH ₃和 RH 对 SO ₂转化为硫酸盐对 α-Fe 的影响₂ O ₃粒子，为大气环境实地研究中二次粒子的形成提供基础数据。