应用溶蚀器/后置膜系统分析上海大气PM_(2.5)中水溶性离子的组成及采样误差

Concentrations and sampling artifacts of water-soluble ions in PM_(2.5) in Shanghai sampled using denuder/backup-filter system

利用溶蚀器/后置膜采样系统分析了上海市PM2.5中主要水溶性离子（SO4^2-、NO3^-、NH4^-、Cl^-）以及大气中NH3、HNO3和HCl的浓度。结果表明,上海PM2.5中SO4^2-、NO3^-和NH4^＋的总浓度为21.55±16.43μg/m^3,其中SO24-是含量最高的水溶性离子,但冬季时NO-3/SO24-比值常大于1,说明流动源已成为上海PM2.5主要的污染源;与溶蚀器/后置膜采样方法相比,常规Teflon膜采样中Cl^-、NO3^-、NH4^＋在夏秋季时存在负误差,而冬季时存在正误差,SO24-在不同季节均出现正误差;冬季常规膜采样造成的误差相对较小;采样期间大气中NH3、HNO3和HCl的浓度范围分别为1.56-20.84μg/m^3、0.26-2.80μg/m^3和0.15-1.62μg/m^3,HNO3和HCl浓度具有显著的夏高冬低的季节变化。

Denuder/backup-filter sampling system was used to measure the water-soluble ions （SO4^2-, NO3^- , NH4^＋ and Cl^- ） in PM2.5, acidic gases and ammonia in the atmosphere in Shanghai. Total concentration of SO4^2-, NO3^- and NH4^＋ in PM2.5 during the sampling periods was high at （21±16） μg/m^3. The high NO3/SO24 ratio in winter （〉1） suggested that vehicle emission was the major contributor to PM2.5 in Shanghai. Comparing with the denuder/backup-filter system, normal sampling with Teflon filter suffered significant negative sampling artifacts for Cl^- , NO3^- and NH4^＋ in summer and autumn, while moderate positive artifacts in winter. SO24 had positive sampling artifacts of about 8% in all the sampling periods when collected with normal sampler. Gaseous NH3, HNO3 and HC1 with concentrations of 1.56-20.84 μg/m^3, 0.26-2.80 μg/m^3 and 0.15-1.62 μg/m^3, respectively, were detected in the atmosphere in Shanghai. HNO3 and HCl had obviously higher concentrations in summer/autumn than those in winter.