Scientific Reports · 2021 · 38 citations · 53 references
The hygroscopic property of particulate matter (PM) influencing light scattering and absorption is vital for determining visibility and accurate sensing of PM using a low-cost sensor. In this study, we examined the hygroscopic properties of coarse PM (CPM) and fine PM (FPM; PM<sub>2.5</sub>) and the effects of their interactions with weather factors on visibility. A censored regression model was built to investigate the relationships between CPM and PM<sub>2.5</sub> concentrations and weather observations. Based on the observed and modeled visibility, we computed the optical hygroscopic growth factor, [Formula: see text], and the hygroscopic mass growth, [Formula: see text], which were applied to PM<sub>2.5</sub> field measurement using a low-cost PM sensor in two different regions. The results revealed that the CPM and PM<sub>2.5</sub> concentrations negatively affect visibility according to the weather type, with substantial modulation of the interaction between the relative humidity (RH) and PM<sub>2.5</sub>. The modeled [Formula: see text] agreed well with the observed [Formula: see text] in the RH range of the haze and mist. Finally, the RH-adjusted PM<sub>2.5</sub> concentrations based on the visibility-derived hygroscopic mass growth showed the accuracy of the low-cost PM sensor improved. These findings demonstrate that in addition to visibility prediction, relationships between PMs and meteorological variables influence light scattering PM sensing.
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