Accurate sampling and analysis of PM2.5 is essential to determine the compliance with promulgated ambient PM2.5 standards and identify the sources of PM2.5 pollutants. USA PM2.5 FRM(federal reference method) manual sa...
详细信息
Accurate sampling and analysis of PM2.5 is essential to determine the compliance with promulgated ambient PM2.5 standards and identify the sources of PM2.5 pollutants. USA PM2.5 FRM(federal reference method) manual samplers or FEM(federal equivalent method) monitors are commonly used but there are still rooms to improve the accuracy. In several air monitoring stations in Taiwan, it was found PM2.5 concentrations are over-estimated by the VEREWA-F701 BAM(beta attenuation monitor) by as much as 58.4 %, and 28.4-29.8 % by the earlier version of the Met-One BAM-1020s(without FEM designation). In this talk, reasons why PM2.5 concentrations are overestimated by automatic beta attenuation monitors, including positive artifacts due to acid gas adsorption by the glass fiber filter tapes used in the monitors, aerosol water content and volatilization loss of inorganic semi-volatile species will be presented(Liu et al., 2013a). Then the size-selective inlets of current manual PM samplers, including impactors and cyclones, will be reviewed and problems associated with particle bounce, evaporation loss, ambient relative humidity and substrate coating conditions will be discussed. It was found that the BGI VSCC(very sharp cut cyclone) has a better solid particle loading performance than that of the WINS impactor and oil-coated Teflon substrates are capable of resolving solid particle loading problems in impactors(Tsai et al., 2012). The results of using the newly developed MFPPS(multi-filter PM10-PM2.5 sampler) in NCTU(Liu et al., 2011) to determine artifacts during filter sampling and conditioning of PM2.5 manual samplers will be presented. The evaluation of PM2.5 monitoring accuracy of the Model 1405-DF TEOM-FDMS, which is capable of correcting for positive and negative PM2.5 artifacts, will also be presented. For obtaining accurate size-classified aerosol samples, a newly developed 10-stage NCTU micro-orifice cascade impactor(NMCI, 56 nm to 10 m) which contains new nozzle plate
借鉴分光光度法测定水样中阴离子表面活性物质的研究,结合国内外大气气溶胶阴离子表面活性物质的研究结果,开展了气溶胶中阴离子表面活性物质分光光度分析法的条件实验,分别优化了亚甲蓝分光光度分析法和乙基紫分光光度分析法。结果表明,两种分析方法的样品超声提取条件基本相同,超声频率选择超声清洗器的最高频率40 Hz,起始水浴温度设定为30℃,以30 min为最佳超声提取时间。亚甲蓝显色剂的最佳使用量为1 m L中性亚甲蓝溶液(0.35 g/L)和1 m L酸性亚甲蓝溶液(0.35 g/L),乙基紫显色剂的最佳加入量为0.2 m L乙基紫溶液(0.49 g/L)。亚甲蓝法萃取完成后应放置30~45 min再测定氯仿相的吸光度,而乙基紫法样品的放置时间不宜过长,在30 min时测定最好。乙基紫分光光度法中应依次加入p H=5的醋酸盐缓冲液0.4 m L、EDTA溶液(0.1 mol/L)0.1 m L和硫酸钠溶液(1 mol/L)0.25 m L,以此达到提高测定灵敏度和降低实验误差的目的。
暂无评论