A New Portable Instrument for Online Measurements of Formaldehyde: From Ambient to Mobile Emission Sources
2020
Zhu, Manni | Dong, Huabin | Yu, Fei | Liao, Songdi | Xie, Yan | Liu, Junwen | Sha, Qinge | Zhong, Zhuangmin | Zeng, Limin | Zheng, Junyu
Formaldehyde (HCHO) plays an important role in atmospheric photochemistry, HOₓ budget, and ozone formation. Several instruments have been developed for measuring ambient HCHO, yet few have targeted primary emission sources due to their very high HCHO levels and complex emission conditions. Here, we present a novel portable instrument, the Hantzsch-Abs, based on the Hantzsch reaction and absorption photometry, which is specifically designed for online continuous measurement of HCHO concentrations both in ambient environment and from vehicle exhaust. The Hantzsch-Abs features an adjustable liquid waveguide capillary cell (LWCC), displaying high sensitivity and strong flexibility for HCHO detection. The limit of detection of the Hantzsch-Abs based on a 50 cm LWCC was 25 pptv; the measurement range could be adjusted up to approximately 3 ppmv. A field comparison with commercially available instruments indicated that the Hantzsch-Abs was sufficiently robust in monitoring atmospheric HCHO concentrations. Furthermore, the instrument is capable of capturing dynamic patterns in HCHO emissions from vehicles under both chassis dynamometer and on-road tests, which suggests potential applications in measuring vehicle emissions. Our experimental data indicated that HCHO emission patterns from vehicles are strongly correlated with driving conditions and that current HCHO emission characteristics for vehicles likely require systematic updating.
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