“…To date, mixing state index has been applied to various machine learning (Hughes et al, 2018) and global models (Ching et al, 2017(Ching et al, , 2018Shou et al, 2019;Stevens & Dastoor, 2019;Yao et al, 2021Yao et al, , 2022Zheng & Curtis et al, 2021;Zheng & West et al, 2021;Zhu et al, 2016). The metric χ has also been derived using data from laboratory experiments (Dickau et al, 2016), and ambient measurements in the low-latitude regions (Fraund et al, 2017;Singh et al, 2021) and mid-latitude regions, including the contiguous United States and throughout Eurasia (Ching et al, 2019;Farley et al, 2023;Healy et al, 2014;Tomlin et al, 2022;Yu et al, 2020;Zhao et al, 2021). In particular, Healy et al (2014) combined single-particle mass spectrometry data with bulk aerosol mass spectrometry and BC measurements to investigate χ of ambient carbonaceous aerosol in Paris, France.…”