Comparison of Two Methods for Obtaining Quantitative Mass Concentrations from Aerosol Time-of-Flight Mass Spectrometry Measurements
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- 作者：Xueying Qin ; Prakash V. Bhave ; Kimberly A. Prather
- 刊名：Analytical Chemistry
- 出版年：2006
- 出版时间：September 1, 2006
- 年：2006
- 卷：78
- 期：17
- 页码：6169 - 6178
- 全文大小：414K
- 年卷期：v.78,no.17(September 1, 2006)
- ISSN：1520-6882
文摘
Aerosol time-of-flight mass spectrometry (ATOFMS) measurements provide continuous information on the aerodynamic size and chemical composition of individualparticles. In this work, we compare two approaches forconverting unscaled ATOFMS measurements into quantitative particle mass concentrations using (1) referencemass concentrations from a co-located micro-orifice uniform deposit impactor (MOUDI) with an accurate estimateof instrument busy time and (2) reference number concentrations from a co-located aerodynamic particle sizer(APS). Aerodynamic-diameter-dependent scaling factorsare used for both methods to account for particle transmission efficiencies through the ATOFMS inlet. Scalingwith APS data retains the high-resolution characteristicsof the ambient aerosol because the scaling functions arespecific for each hourly time period and account for amaximum in the ATOFMS transmission efficiency curvefor larger-sized particles. Scaled mass concentrationsobtained from both methods are compared with co-locatedPM2.5 measurements for evaluation purposes. Whencompared against mass concentrations from a beta attenuation monitor (BAM), the MOUDI-scaled ATOFMSmass concentrations show correlations of 0.79 at Fresno,and the APS-scaled results show correlations of 0.91 atAngiola. Applying composition-dependent density corrections leads to a slope of nearly 1 with 0 intercept betweenthe APS-scaled absolute mass concentration values andBAM mass measurements. This paper provides details onthe methodologies used to convert ATOFMS data intocontinuous, quantitative, and size-resolved mass concentrations that will ultimately be used to provide a quantitative estimate of the number and mass concentrations ofparticles from different sources.