Xiaofei Qin's research while affiliated with Qingdao University of Technology and other places

... Recently, Wang et al. (2019) developed the minimum R-squared (MRS) method to differentiate the light absorption determined by AE33 into secondary BrC and primary BrC in fine particles. The MRS method has also been extended to explore the secondary WS-BrC (Li, Qin, et al., 2023). However, BrC chromophores in the atmosphere rapidly bleach to colorless or produce darker ones due to photolysis (such as UV) or oxidation (such as O 3 , NH 3 , NO x ) (He et al., 2022;Lee et al., 2014;Updyke et al., 2012). ...

... The most important advantage of the MAX-DOAS is that it can simultaneously monitor various atmospheric components, including aerosols, NO 2 , and HCHO, thereby overcoming the errors of atmospheric component monitoring using different instruments. MAX-DOAS has been widely used in studies of the vertical distribution characteristics of atmospheric components in different environments (suburban, regional, island, and offshore) in different regions, e.g., the Beijing-Tianjin-Hebei [9,[17][18][19], the Pearl River Delta region [13,20,21] and the YRD region [22][23][24][25][26][27]. This technology provides a promising method for the accurate monitoring and management of air pollution. ...

... Based on importance diagnose of variables, Ye et al. (2022) showed that a prediction bias for ozone concentrations in chemical transport models resulted from the underestimation of dry deposition and cloud optical depth. Further, coupled with a SHapley Additive ExPlanation (SHAP) approach, any ML model can provide a clear explanation of variable importance (evaluating contributions in physical units such as μg/m 3 ), which can support the dimension reduction of variables for the source apportionment of pollutants (Hou et al., 2022;Qin et al., 2022b;Zhang et al., 2022). ...

... ributions of anthropogenic sources to amines in PM 2.5 suggested that the formation of particle-phase amine salts (e.g., MA and DMA) was closely associated with the origins of gas-phase amines (C. . This is because these gas-phase amines can be largely converted into amine salts in the particle phase through secondary processes (Huang et al., 2022;C. Liu et al., 2022;Liu et al., 2018). Different pathways for converting gas-phase amines to amine salts in the particle phase will be discussed in detail in the following section. ...

... This further leads to disruptions in the energy balance, which could affect the aerosol formation and removal processes (Flamant et al., 2018). The weakening effect of SLB also results in more serious atmospheric pollution which directly or indirectly affects the health and living standards of the residents (Budhiraja et al., 2019;Wang et al., 2022). Previous studies have primarily focused on the effects of SLB on pollution episodes (Ding et al., 2004) or a short-term (1-3 days) mesoscale circulation (El-Geziry et al., 2021;Shen et al., 2019;Zhu et al., 2017). ...

... g studies did not quantify the importance of the input variables, making these the machine learning process nonexplainable or like a "black box" (Wang et al., 2022a;Lin et al., 2023a). An explainable machine learning algorithm such as the SHapley Additive exPlanation (SHAP) can quantify the impact of meteorological variables (Lundberg et al., 2020;X. Qin et al., 2022;Wang et al., 2022a). However, few studies have applied the explainable machine learning algorithm to study the trend in vehicular emissions. Moreover, most previous studies focused on the changes in the measured NO 2 concentrations, which were routinely measured at an air quality monitoring site , while few studies reported vehicular EC ...

... Considering the vast area of the ocean (covering 70% of the Earth's surface), marine carbonaceous aerosols are an integral and significant component of global aerosols. Marine carbonaceous aerosols are a complex system consisting of both marine and continental sources (Hegde et al., 2022;H Li, Qin, et al., 2022). On the one hand, evaluating the impact of anthropogenic carbonaceous aerosols on the ocean environment is especially important for marine regions that are strongly influenced by continental outflows, such as the Northwest Pacific and the Indian Ocean (Hegde et al., 2022;Z L Wu et al., 2020). ...

... The strict quarantine measures taken to control COVID- 19 have benefited the quality of air across China within the short term, with significant reductions in concentrations of PM2.5, CO, and NO2 [22]. However, little research has been performed on the effects of emission changes on toxic elemental species in PM2.5 during the COVID-19 lockdown [30] and whether the health risks of toxic elements in the environment decreased during the lockdown period, and whether the source-specific health risks have changed are unclear. ...

... Y. Liu et al., 2019). Existing studies have reported the trends in GEM concentrations at three sites in eastern China covering a few (≤4) years (Qin et al., 2020;Tang et al., 2018;Wu et al., 2020). Analysis of these data using multiple source identification methods, including trajectory-based source identification, positive matrix factorization, and statistical models, helps to understand the mechanisms controlling GEM concentrations. ...

... The capillary cell was cleaned every 3 days with methanol (UV-HPLC-gradient grade, CNW), hydrochloric acid solution (HCl, 2 mol/L), sodium hydroxide solution (NaOH, 1 mol/L), and ultrapure water. More details of IGAC and LWCC-TIDAS can be found in Figure S1 in Supporting Information S1 and our previous studies in J. Xu, Chen, Shi, et al. (2020), G. Wang et al. (2022), and H. . ...