Evaluation of a method for measuring vehicular PM with a composite filter and a real-time BC instrument. (December 2015)

• Record Type: Journal Article
• Authors: Kamboures, Michael A.; Rieger, Paul L.; Zhang, Sherry; Sardar, Satya B.; Chang, M.-C. Oliver; Huang, Shiou-Mei; Dzhema, Inna; Fuentes, Mark; Benjamin, Michael T.; Hebert, Annette; Ayala, Alberto
• Is Part Of: Atmospheric environment. Volume 123:Part A(2015)
• Page Start: 63
• Page End: 71
• Publication Date: 2015-12
• Subjects: Black carbon -- Particulate matter -- Vehicular -- California -- Measurement -- Regulatory; Air -- Pollution -- Periodicals; Air -- Pollution -- Meteorological aspects -- Periodicals; 551.51
• DOI: 10.1016/j.atmosenv.2015.10.061
• Languages: English
• ISSNs: 1352-2310

Abstract

Abstract: As part of the California Air Resources Board's effort to confirm the ability of the vehicular particulate matter (PM) reference method (RM) to measure PM emissions at sub-one milligram per mile (mg/mi), and to explore alternative methods, we evaluated a combination method (CM) that utilizes both gravimetric and real-time particle quantification. PM, collected on a single composite filter is apportioned to the three Federal Test Procedure (FTP) cycle phases using real-time equivalent black carbon (EBC) measurements, reducing the need to carry out separate gravimetric filter measurements for each of the test phases. Four light-duty gasoline vehicles, emitting PM at or below one mg/mi, were dynamometer tested repeatedly on the FTP cycle. PM was quantified by the RM and by two variants of the CM. One variant used photoacoustic spectroscopy to measure EBC (CM-MSS), and the other used an Aethalometer (CM-AE51). The CM was evaluated on repeatability, bias, and correlation with the RM. For the tested vehicles, the observed repeatability of the CM was superior to the RM regardless of the mode of EBC measurement or the test vehicle considered (σCM−MSS = 0.08 mg/mi, σCM−AE51 = 0.07 mg/mi, σRM ≈ 0.11 mg/mi). However, the CM was negatively biased by −0.08 mg/mi, versus the RM, in one of the test vehicles. We attribute the bias in this vehicle's data to organic carbon emissions that were not equivalently collected on the composite filter of the CM. When all data were combined, the correlation between the methods was good (R = 0.90 for CM-MSS vs. RM and R = 0.91 for CM-AE51 vs. RM). Highlights: The new composite filter + BC method for vehicular PM is more repeatable than the reference method. The combined method was biased negatively vs. the reference method in one of four vehicles. The data suggest that the reference method and the combined method can measure PM < 1 mg/mi.