To improve the methodology of measuring the mass concentration and chemical composition of atmospheric particulate matter, size-segregated samples were collected at three sites, i.e., Beijing, Qianyanzhou and Mountain Dinghu, using a 9-stage impactor (Andersen, USA). Mass concentration deviation and membrane choice were discussed based on weighting condition and chemical analysis. Under the constant temperature and humidity (50% RH, 25℃), mass concentrations of PM2.1 gained from the quartz membrane were 20% higher than that of PM2.5 measured by TEOM, due to the high relative humidity. In contrast, this magnitude decreased to 8% under dry condition (10% RH, 25℃), which falls in a reasonable range. Moreover, if the quartz membrane was conditioned in a dryer (10% RH, 25℃) for 72h before weighing to obtain mass concentration, a significantly linear correlation can be found between the mass concentration of weighted PM2.1 sampled using the Andersen impactor and that of PM2.5 measured by TEOM (R2 = 0.89,P<0.05). To improve the mass closure of particles, asynchronous sampling scheme with cellulose membrane and quartz membrane was built. Consequently, a significantly linear correlation between weighted and chemical reconstructed PM2.1 mass concentration (R2 = 0.89,P<0.05) was observed.%为提高不同粒径段大气颗粒物质量浓度及化学组成测量数据的准确性,使用惯性撞击式采样器对北京、千烟洲和鼎湖山3个站点的大气颗粒物分9个粒径段进行了采集,从质量浓度偏差和化学组成的角度进行了方法学探讨.结果表明,在恒温25℃、恒湿50%平衡条件下,称量石英材质的采样膜获得的PM2.1质量浓度相对于TEOM在线PM2.5观测结果的正偏差为20%左右,正偏差诱因是环境空气相对湿度过高.干燥(10%湿度,25℃)微环境平衡处理方法有利于采样后膜片中H2O析出,使得上述正偏差降低至8%.通过条件实验,确定了石英膜采样前后在干燥器中放置72h平衡后称重、差减获得各级质量浓度的方法,可将偏差控制在可接受范围之内.基于这种方法获得的PM2.1质量浓度与 TEOM 在线 PM2.5观测结果呈显著线性相关(R2=0.89,P<0.05).为达到通过化学成分重构质量浓度的需求,建立了同步使用石英膜采集样品并用于水溶性成分、有机碳和元素碳含量分析,而使用纤维素膜采样后用于金属元素分析的方案.应用上述方案对样品进行了全化学分析,对PM2.1质量进行了重构,重构获得的质量浓度与称重获得PM2.1质量浓度也呈显著线性相关(R2=0.89,P<0.05).
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