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Performance assessment of a portable nephelometer for outdoor particle mass measurement

Abstract

The availability of portable nephelometers has improved exposure assessment of atmospheric particles at a high resolution regarding space and time. However, nephelometer performance has seldom been evaluated for outdoor measurements, especially in Chinese cities. During 37 days of measurements at four outdoor sites in Shanghai, we assessed a popular nephelometer called SidePak (TSI Inc., USA) for PM1.0, PM2.5 and PM10 mass measurements and compared them to US federal reference methods (FRMs) based on different measurement principles. The nephelometer showed high measurement precision and stability and was strongly correlated with FRMs, which is superior to the portable light scattering monitors reported in the past and thus indicates the maturity of this principle. The nephelometer measurements overestimated all those of FRMs by a factor of two, which is higher than in evaluations in other international cities. This overestimation showed a descending order for PM1.0 (2.9-fold), PM2.5 (2.2-fold) and PM10 (1.9-fold) relative to FRMs of tapered element oscillating microbalance or beta attenuation combined with nephelometry, based on whole samples. Sites that are far from direct pollution sources showed very good agreement between the nephelometer and FRMs for PM2.5 mass measurements, while by comparison, the roadside site showed a lower SidePak/FRM PM2.5 ratio that is likely due to higher components of element carbon in roadside particles. Relative humidity (RH) was proved to be a key factor that distorted the measurement of the nephelometer. An empirical formula considering an RH adjustment developed to correct the nephelometer could produce a reasonable result, even across the various sites. This study demonstrates the great potential of the nephelometer for outdoor particle mass measurements, but for accurate and comparable data, a site-specific calibration is strongly recommended before using.

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Publication details

The article was received on 26 Jul 2017, accepted on 25 Nov 2017 and first published on 27 Nov 2017


Article type: Paper
DOI: 10.1039/C7EM00336F
Citation: Environ. Sci.: Processes Impacts, 2017, Accepted Manuscript
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    Performance assessment of a portable nephelometer for outdoor particle mass measurement

    Z. Wang, D. Wang, Z. Peng, M. Cai, Q. Fu and D. Wang, Environ. Sci.: Processes Impacts, 2017, Accepted Manuscript , DOI: 10.1039/C7EM00336F

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