Size-Dependent Mixing Characteristics of Volatile and Nonvolatile Components in Diesel Exhaust Aerosols

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• 作者：Hiromu Sakurai ; Kihong Park ; Peter H. McMurry ; Darrick D. Zarling ; David B. Kittelson ; and Paul J. Ziemann
• 刊名：Environmental Science & Technology
• 出版年：2003
• 出版时间：December 15, 2003
• 年：2003
• 卷：37
• 期：24
• 页码：5487 - 5495
• 全文大小：142K
• 年卷期：v.37,no.24(December 15, 2003)
• ISSN：1520-5851

文摘

Mixing characteristics of particles of different volatilitiesfrom a diesel engine were studied with two tandem differentialmobility analyzers (TDMAs) and an aerosol particle massanalyzer (APM). In both TDMA systems, a heater was locatedin the aerosol path between the first and second DMAs.Diesel exhaust particles that were size-selected in the firstDMA were passed through the heater, and the changein particle size due to loss of volatile components wasdetermined by the second DMA. On the basis of the volatilitymeasurements, the particles could be separated intotwo overlapping modes that varied in peak diameter andmagnitude depending on the engine operating conditions.Particles in the smaller size mode were almost completelyvolatile, while those in the larger size mode containeda nonvolatile core. The TDMA data inversion technique usedhere allowed accurate determination of the mixing ratiosof the two types of particles. These data were in turn usedto validate a simple fitting method that uses two log-normal curves to obtain the mixing ratios. In some experiments,the APM was used downstream of a TDMA to directlymeasure the particle mass loss due to evaporation. Theloss determined by the TDMA-APM system was significantlygreater than that calculated from mobility size changesmeasured solely with the TDMA. The TDMA-APM resultswere used to calculate the size-dependent massconcentrations of volatile and nonvolatile components forparticles in the size range from 70 to 200 nm.