## 5 Conclusions  
In this study, an integrated method based on ArcGIS geoprocessing was presented to quantify the contribution of external sources of SOB to elevated urban PM\({}_{2.5}\) concentrations during specific haze episodes at a high temporal resolution of 1 h. The results of this study showed that during the SOB season in 2020-2021, Changchun experienced severe urban PEs three times (PE I, PE II, and PE III) and heavy urban PE once (PE IV), which lasted 97 h in total. Additionally, we discovered that the total PM\({}_{2.5}\) contributions from SOB sources were 352 \(\upmu\)g m\({}^{-3}\), 872 \(\upmu\)g m\({}^{-3}\), and 1224 \(\upmu\)g m\({}^{-3}\) during the three instances of severe PEs, respectively, accounting for 7%, 27%, and 23% of the urban cumulative PM\({}_{2.5}\) level; these were more obvious than contribution during the heavy PE. During PE IV, the total PM\({}_{2.5}\) contribution from SOB sources (4.9 \(\upmu\)g m\({}^{-3}\)) was only 0.31% of the urban cumulative PM\({}_{2.5}\) level; this is mainly due to the long transport distance of SOB sources and the higher PBLH along the transport pathways. In addition, it seemed that primary pollutants from SOB sources played a more important role in the early stage of the evolution of haze episodes, characterized by bimodal or multimodal distribution, and the later peak was possibly not only related to the primary pollutants of SOB but also ascribed to the formation of secondary aerosols. The advantages of our integrated method are mainly the following. First, the spatial and temporal distribution scope of potential SOB sources associated with a specific PE could be determined via reconstructed HTPs and HWFGs, and the SOB fire spots associated with elevated PM\({}_{2.5}\) concentrations during PEs could be identified. Moreover, the TSSTMB model linked the spatial scope of external SOB sources, their transport pathways, and the hourly pollution level in the receptor city. Furthermore, the interactive model based on ArcGIS geoprocessing can integrate different types of multi-source datasets. Although secondary particulate matter formation during transport should be further supplemented in future directions, we believe this integrated method is physically realistic regarding the regional transport of SOB-caused primary PM\({}_{2.5}\). Additionally, the refined policy recommendations put forward in this paper are applicable to cities, such as Changchun, which are located in the major grain-producing areas of the plains; this would help to change the implementation of planned and systematic SOB in rural areas to minimize the adverse effects on urban air quality. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/rs14184671/s1](https://www.mdpi.com/article/10.3390/rs14184671/s1)]([https://www.mdpi.com/article/10.3390/rs14184671/s1](https://www.mdpi.com/article/10.3390/rs14184671/s1)). Figure S1: Schematic of identifying potential straw open burning sources; Table S1: Computation table of PM\({}_{2.5}\)-inflow contribution to urban hourly average PM\({}_{2.5}\) concentrations; Table S2: Hourly and staged average contribution of straw open burning sources during PE II and PE III. Conceptualization, X.W. ; methodology, X.W. ; software, X.W. and W.C.; investigation, X.W. ; resources, X.W. and P.Z. ; formal analysis, X.W. ; data curation, X.W., W.C. and J.C.; writing--original draft preparation, X.W. ; writing--review and editing, X.W., W.C. and P.Z. ; visualization, X.W. and G.S. ; supervision, X.W. and W.C.; project administration, X.W. and W.C.; funding acquisition, X.W. and W.C. All authors have read and agreed to the published version of the manuscript. This research was funded by [the National Natural Science Foundation of China] grant number [42171297] And [the Strategic Priority Research Program of the Chinese Academy of Sciences] grant number [Grant No. XDA28110100] And [the Key Research Program of Frontier Sciences,Chinese Academy of Sciences) grant number [No.