## 5 Discussion and Conclusions
In the future, additional work that combines emission sources and external monitored PM\({}_{2.5}\) concentration data is needed to improve the prediction of PM\({}_{2.5}\) source regions and validate the analysis results quantitatively. This paper analyzes the external and internal potential source regions of PM\({}_{2.5}\) pollution and their influences on Weifang City. Our findings can provide scientific support for the design of region-specific measures for atmospheric pollution prevention and the development of a chemical transport model combined with meteorology. However, this work also has limitations. For instance, the resolution of the study grid based on the backward trajectory model is not very high and may not be applied to small-scale regions. Furthermore, the estimation of the sources of PM\({}_{2.5}\) is not perfect because the contributing sources were calculated only based on meteorological data without information such as the production and deposition of dust. In future research, based on the results in this paper, auxiliary parameters such as the local emission sources and external PM\({}_{2.5}\) monitoring value will be combined to improve the simulation analysis accuracy and evaluate the accuracy of potential sources contributing to the PM\({}_{2.5}\) in Weifang quantitatively. Furthermore, analyses for various years will be further conducted to assess the inter-annual variability. Conceptualization, C.L. ; methodology, C.L. and Z.D. ; software, Z.D. and X.L. ; validation, Z.D., X.L. and P.W. ; formal analysis, Z.D., X.L. and P.W. ; investigation, Z.D. and X.L. ; resources, C.L. ; writing--original draft preparation, Z.D. ; writing--review and editing, C.L. and Z.D. ; supervision, C.L. ; and funding acquisition, C.L. and Z.D. 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 numbers 41907389 and 41871375, National Key Research and Development Program of China, grant number 2018 YFB2100700, and Basic Foundation of Chinese Academy of Surveying and Mapping (AR2010). The authors declare no conflict of interest. * [PERSON] et al. (2016) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] Mortality effects assessment of ambient PM2.5 pollution in the 74 leading cities of China. _Sci. Total Environ._**2016**, _569-570_, 1545-1552. [CrossRef] [PubMed]
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