硝酸铵对SO2在大气颗粒物表面气-粒转化影响的模拟研究

利用流动态的原位傅里叶变换红外漫反射光谱(DRIFTS)对含硝酸铵气溶胶(以α-Fe₂O₃为主模拟气溶胶)与SO₂的非均相反应进行了研究, 比较了硝酸铵与其它金属氧化物(CaO, MgO, α-Al₂O₃和SiO₂)与SO₂反应的情况.实验结果表明, 硝酸铵和α-Fe₂O₃混合颗粒物比硝酸铵和其它金属氧化物混合颗粒与SO₂反应的吸附系数高, 表明α-Fe₂O₃比其它金属氧化物催化能力变强.利用BET面积作为反应活性表面积, 发现含有6％(质量分数)NH₄NO₃的α-Fe₂O₃混合颗粒物与SO₂反应具有最高的比表面积吸附系数(γ_BET=2.42×10^-9), 比纯氧化铁的反应高了近1.8倍.而纯NH₄NO₃颗粒与SO₂不发生反应, 表明少量硝酸铵的存在在一定程度上提高了SO₂在气溶胶颗粒物表面转化成硫酸盐的能力. 本文还讨论了含硝酸铵气溶胶与SO₂的反应机制及其对大气环境的影响.

Experimental Study of the Effects of Ammonium Nitrate on SO2 Gas-particle Transfer on the Surface of Atmospheric Aerosols

Heterogeneous oxidation of gaseous SO2 on NH4NO3-containing hematite compared to other NH4NO3-containing oxides(MgO, Al2O3, CaO, SiO2) were first studied using an in situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS). Obvious sulfate formation can be seen from the infrared spectrum of NH4NO3-containing oxides, and the catalytic activity of hematite is much higher compared to other oxides. Using BET area as the reactive surface area, the hematite sample containing 6%(mass fraction) of NH4NO3 presents the highest γBET value(2.42×10-9), which is about 1.8 times larger than that of hematite. No formation of sulfate is observed on the pure NH4NO3. The results show that appropriate NH4NO3 increases the sulfate formation while more NH4NO3 impedes. Mechanism is discussed.