气态污染物和气溶胶在线检测装置(GAC)测量结果评估

Evaluation of the Performance of a Gas and Aerosol Collector (GAC)

气态污染物和气溶胶在线检测装置(GAC)是一种连续收集、测量气态污染物和气溶胶水溶性组分的装置.分别将GAC的测量结果与二氧化硫(SO2)分析仪、差分吸收光谱(DOAS)、颗粒物-液体转换采集系统(PILS)和膜采样法的测量结果进行比对.结果表明:GAC对SO2吸收完全,测量结果稳定可靠;GAC测量的气态亚硝酸(HONO)质量浓度比DOAS测量值略偏高,原因可能是在相对湿度较高的条件下GAC对HONO的测量受到了NO2的干扰;GAC和PILS测量的硫酸盐、硝酸盐和氯离子质量浓度〔分别以ρ(SO42-),ρ(NO3-)和ρ(Cl-)计〕均有较好的相关性,将ρGAC(SO42-)校正到与PILS相同的粒径范围后,与ρPILS(SO42-)的系统偏差仅为-2%;GAC与膜采样法测量的ρ(SO42-)具有较好的相关性(R2=0.96),而二者的ρ(NO3-)相关性较差,原因可能是硝酸盐在膜采样过程中有损失,使膜采样法的测量结果偏低.

A Gas and Aerosol Collector （GAC） can continuously collect and measure gaseous and particulate water-soluble ions. Comparisons were performed between a GAC and other instruments including a SO2 analyzer, Differential Optical Absorption Spectroscopy （DOAS）, a Particle into Liquid Sampler （PIES） and fdter-based measurements. The results indicated that the GAC could absorb SO2 completely and give reliable SO2 measurement results. The GAC gave higher HONO mass concentrations than DOAS because NO2 may interfere with HONO measurement under high relative humidity. The mass concentrations of sulfate, nitrate and chloride measured by the GAC had good correlations with those by the PIES. After modifying the PM10 by chemical size distribution, the GAC-sulfate and PIES-sulfate mass concentration had a difference within -2%. The sulfate mass concentration measured by the GAC had very good correlation with that by filtering. The GAC-nitrate mass concentration was poorly correlated with that by filtering; the filter-nitrate mass concentration was lower than the GAC-nitrate mass concentration because of loss of nitrate in the sampling process.