Particulate nitrate formation in a highly polluted urban area: a case study by single-particle mass spectrometry in Shanghai.
Particulate nitrate formation in a highly polluted urban area: a case study by single-particle mass spectrometry in Shanghai.
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DOI：
10.1021/es8020155
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发表时间：
2009-03
影响因子：
11.4
通讯作者：
Xiaofei Wang;Ya-ping Zhang;Hong Chen;Xin Yang;Jianmin Chen;F. Geng
中科院分区：
文献类型：
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作者：
Xiaofei Wang;Ya-ping Zhang;Hong Chen;Xin Yang;Jianmin Chen;F. Geng
2007年8月，我们部署了一台气溶胶飞行时间质谱仪，对上海0.1-2.0微米直径的颗粒物进行了表征，以检测含硝酸盐的颗粒物。单个粒子的质谱中约有39%含有硝酸盐离子峰。硝酸盐信号的相对强度表现出明显的昼夜变化特征，在高污染日的深夜或清晨达到峰值，且与环境相对湿度（RH）密切相关。然而，在空气质量较好的采样日，硝酸盐的日变化模式发生了变化，硝酸盐的信号强度低得多，变化不规则。质谱中铵态氮和硝态氮信号相关性较差，排除了NH4NO3作为颗粒硝态氮的主要形式的可能性，高RH和低温有利于其形成。夜间硝酸盐峰值强度和高浓度的O3和NO2强烈表明，N2O5和NO3在污染日气溶胶表面的非均相反应主导了颗粒物硝酸盐的形成。
An aerosol time-of-flight mass spectrometer was deployed in August 2007 to characterize the 0.1-2.0 microm diameter particles in Shanghai to examine nitrate-containing particles. About 39% of the mass spectra of single particles contained nitrate ion peaks. The relative intensity of nitrate signals showed a pronounced diurnal profile, peaking in the late night or early morning during highly polluted days, and is closely correlated with the ambient relative humidity (RH). However, during the sampling days with good air quality, the diurnal pattern of nitrate changed by showing much lower signal intensity of nitrate with irregular variation. Poor correlation between the signals of ammonium and nitrate inthe mass spectra excluded the possibility of NH4NO3 as a major form of particulate nitrate, whose formation is favored by high RH and low temperature. The peak intensities of nitrate during the nighttime and high concentrations of O3 and NO2 strongly suggest that the heterogeneous reactions of N2O5 and NO3 onthe aerosol surface dominated the particulate nitrate formation on polluted days.