基于热扩散管的深圳大气气溶胶半挥发性分析

在气溶胶质谱仪采样口前接入热扩散管,对深圳市2013年8月7日-9月7日大气细颗粒物进行连续在线观测,实现对气溶胶半挥发性的同步测定,量化其半挥发性水平.结果表明:加热温度为50℃时,约63%质量浓度的硝酸盐组分挥发至气相,是颗粒物中半挥发性最高的组分;而硫酸盐仍有约90%的颗粒残留,是半挥发性最低的组分;有机物的平均半挥发性高于硝酸盐,但低于硫酸盐.加热温度为200℃时,各组分的半挥发性接近,约有20%~30%的颗粒残留.在较为接近实际大气温度的50℃时,硝酸盐、有机物和硫酸盐的半挥发性因细颗粒物污染程度加剧而呈现不同的变化趋势.本文结果表明,深圳夏季大气细颗粒物具有显著的半挥发性,其大气环境影响值得今后深入研究.

Characterization of atmospheric aerosol semi-volatility in Shenzhen using the thermal denuder

The aerosol semi-volatility had become a key issue in the field of atmospheric chemistry. Here, a newly-developed thermal denuder-aerosol mass spectrometer (TD-AMS) system was utilized to measure atmospheric fine particles in Shenzhen, China, continuously during August 2013, focusing on the quantification of aerosol semi-volatility. The results showed that, nitrate had the highest semi-volatility, with 63% of the total mass evaporating into the gas phase at a heating temperature of 50℃, while sulfate was the most stable component, with almost 90% of its mass remaining in the particle phase. Organic matter showed a middle level of semi-volatility between nitrate and sulfate. When heated to 200℃, each component had a similar semi-volatility level, with 20%~30% mass remaining in the particle phase. In addition, the semi-volatilities of organic matter, nitrate and sulfate at 50℃, which was the closest to the ambient temperature, showed different trends as the function of the particle pollution level. This study suggested that the aerosol in Shenzhen in summer had a significant semi-volatility level, which was worthy of further study.