Chow Judith C, Doraiswamy Prakash, Watson John G, Chen L W Antony, Ho Steven Sai Hang, Sodeman David A
Division of Atmospheric Sciences, Desert Research Institute, Reno, NV 89512, USA.
J Air Waste Manag Assoc. 2008 Feb;58(2):141-63. doi: 10.3155/1047-3289.58.2.141.
Recent improvements in integrated and continuous PM2.5 mass and chemical measurements from the Supersite program and related studies in the past decade are summarized. Analytical capabilities of the measurement methods, including accuracy, precision, interferences, minimum detectable levels, comparability, and data completeness are documented. Upstream denuders followed by filter packs in integrated samplers allow an estimation of sampling artifacts. Efforts are needed to: (1) address positive and negative artifacts for organic carbon (OC), and (2) develop carbon standards to better separate organic versus elemental carbon (EC) under different temperature settings and analysis atmospheres. Advances in thermal desorption followed by gas chromatography/ mass spectrometry (GC/MS) provide organic speciation of approximately 130 nonpolar compounds (e.g., n-alkanes, alkenes, hopanes, steranes, and polycyclic aromatic hydrocarbons [PAHs]) using small portions of filters from existing integrated samples. Speciation of water-soluble OC (WSOC) using ion chromatography (IC)-based instruments can replace labor-intensive solvent extraction for many compounds used as source markers. Thermal gas-based continuous nitrate and sulfate measurements underestimate filter ions by 10-50% and require calibration against on-site filter-based measurements. IC-based instruments provide multiple ions and report comparable (+/-10%) results to filter-based measurements. Maintaining a greater than 80% data capture rate in continuous instruments is labor intensive and requires experienced operators. Several instruments quantify black carbon (BC) by optical or photoacoustic methods, or EC by thermal methods. A few instruments provide real-time OC, EC, and organic speciation. BC and EC concentrations from continuous instruments are highly correlated but the concentrations differ by a factor of two or more. Site- and season-specific mass absorption efficiencies are needed to convert light absorption to BC. Particle mass spectrometers, although semiquantitative, provide much information on particle size and composition related to formation, growth, and characteristics over short averaging times. Efforts are made to quantify mass by collocating with other particle sizing instruments. Common parameters should be identified and consistent approaches are needed to establish comparability among measurements.
总结了过去十年中超级站点计划及相关研究在集成式连续PM2.5质量与化学测量方面的最新进展。记录了测量方法的分析能力，包括准确性、精密度、干扰、最低检测限、可比性和数据完整性。集成采样器中上游使用除雾器后接滤膜组件可对采样假象进行估算。需要做出努力来：（1）解决有机碳（OC）的正负假象问题，以及（2）制定碳标准，以便在不同温度设置和分析环境下更好地分离有机碳与元素碳（EC）。热脱附后接气相色谱/质谱联用（GC/MS）技术的进展使得利用现有集成样品中的少量滤膜部分，能够对约130种非极性化合物（如正构烷烃、烯烃、藿烷、甾烷和多环芳烃[PAHs]）进行有机形态分析。使用基于离子色谱（IC）的仪器对水溶性有机碳（WSOC）进行形态分析，可替代许多用作源标记物的化合物的劳动密集型溶剂萃取法。基于热气体的连续硝酸盐和硫酸盐测量会使滤膜离子低估10%-50%，需要根据现场基于滤膜的测量进行校准。基于IC的仪器可提供多种离子，并报告与基于滤膜的测量结果可比（±10%）的结果。在连续仪器中保持大于80%的数据捕获率需要大量人力，且需要经验丰富的操作人员。有几种仪器通过光学或光声方法对黑碳（BC）进行定量，或通过热方法对元素碳进行定量。少数仪器可提供实时有机碳、元素碳和有机形态分析。连续仪器测得的BC和EC浓度高度相关，但浓度相差两倍或更多。需要特定地点和季节的质量吸收效率来将光吸收转换为BC。颗粒质谱仪虽然是半定量的，但在短平均时间内可提供大量有关颗粒大小和与形成、生长及特性相关的组成信息。正努力通过与其他颗粒尺寸测量仪器并置来对质量进行定量。应确定共同参数，并需要采用一致的方法来建立测量之间的可比性。
