超大城市SO2排放对硫酸盐区域分布影响的观测与模拟

2002年8月14—24日在临安采集气溶胶样品,对气溶胶质往往w量和离子成分的尺度分布进行分析.结果表明:SO₄2-主要集中在粒径<2.1 μm的细粒子中,约占所有尺度段上SO42-质量总和的94%;细粒子(PM_2.1)中,ρ(SO₄2-)和ρ(NH₄+)最高,二者之和占所分析离子质量浓度总和的89%. 利用公共多尺度空气质量模式(CMAQ)的过程分析对影响硫酸盐气溶胶分布特征的主要因子进行定量评估,结果表明:经过云内液相氧化和湿清除形成硫酸盐气溶胶的速率为0.19 μg/(m3·h),其对硫酸盐气溶胶的贡献最大;SO₂液相氧化反应中速率最大的是H₂O₂〔5.26 μg/(m3·h)〕,其次是O₂〔4.14 μg/(m3·h)〕和O₃〔1.56 μg/(m3·h)〕. 模拟分析证明,采样期间研究区域SO₄2-主要是由上海及其以南的浙江沿海一带通过SO₂云内与H₂O₂和O₂的液相氧化反应生成. 通过模式敏感性试验发现,在个例的风场配置下,上海排放的SO₂对临安地区的SO₂和硫酸盐的贡献率分别达15%和22%. 

Impact of SO2 Emissions from a Megacity on the Regional Distribution of Sulfate Aerosols: Observation and Model Simulations

Aerosol samples were taken in Lin'an city from 2002-08-14 to 2002-08-24 in order to analyze the size distributions of aerosol mass and ionic components. The results indicated that SO₄2- with size less than 2.1 μm accounted for 94% of the total mass in all size ranges. In fine particles (PM_2.1), SO₄2- and NH₄+ had the largest mass concentrations and accounted for 89% of the total mass ofall analyzed ionic components. The Community Multiscale Air Quality (CMAQ) model was used to analyze the main factors affecting distribution of sulfate aerosol. The results indicated that the sulfate formation rate through in-cloud aqueousoxidation and wet deposition was 0.19 μg/(m3·h), which was 2.5 times the rateof sulfur gas condensation. Among the SO₂ aqueous oxidations, H₂O₂ had the largest reaction rate 5.26 μg/(m3·h), followed by O₂ 4.14 μg/(m3·h) and O₃ 1.56 μg/(m3·h). This proved that SO₄2- in Lin'an was produced via the in-cloud aqueous oxidations of SO₂ by H₂O₂ and O₂ over Shanghai and the coastal region of Zhejiang. A sensitivity test was applied by shutting down SO₂ emissions in Shanghai, and it was found that SO₂ emitted from Shanghai accounted for 15% and 22% ofSO₂ and SO₄2- in Lin'an, respectively.