**4. Conclusions**

In this study, VOCs samples were collected in Jinghong and analyzed for their mass concentration, ozone formation potential, source identity, and health risk assessments in dry and rainy seasons. During the sampling period, a total of 48 VOC species were detected at the urban and suburban monitoring sites. In the dry season, the TVOCs concentration was 146.19 μg/m3 in the urban area and 47.15 μg/m3 in the suburban areas. In the rainy season, the TVOCs concentration was 142.5 μg/m<sup>3</sup> in the urban area and 49.27 μg/m<sup>3</sup> in the suburban area. TVOCs in urban areas were much higher than those in suburbs, which was related to human activities. The concentration of VOCs in the dry season at the urban sampling site was higher than in the rainy season, while at the suburban sampling sites, the concentration in the rainy season was higher than that in the dry season. These results may be related to the emission of more olefins in the rainy season when the vegetation is dense and grows vigorously.

The species with high concentrations of atmospheric VOCs in Jinghong were propane, toluene, propylene, and isoprene, and their OFPs were olefins > aromatic hydrocarbons > alkanes. The species with the highest OFP was isoprene, indicating that the surrounding dense vegetation contributes significantly to the generation of O3. The ratio of specific species was used to analyze

the primary sources of VOCs in the atmosphere of the main urban area of Jinghong: plant sources, motor vehicle exhaust, and oil and gas volatilization; combined with the study of air mass trajectories, the transmission of biomass combustion sources in the Myanmar region may influence VOCs in the study area. The health risk of VOCs in the main urban area of Jinghong was generally lower than those of other cities, and the noncarcinogenic risk was within the safety threshold. However, benzene's lifetime carcinogenic risk value in the atmosphere exceeded the safety range (R < 1.00 × 10<sup>−</sup>6), and there was a particular carcinogenic risk. The control of local VOC sources should be strengthened appropriately to reduce benzene emissions.

In this paper, chemical composition and source characteristics of VOCs in a plateau border city were first studied, and the main sources of VOCs in Jinghong were resolved. The results can provide scientific data to support VOCs pollution control in local and similar cities. In addition, due to high vegetation coverage, forest and vehicle exhaust emissions were prone to produce phytotoxic ozone, which reduced forest productivity and damaged terrestrial vegetation. Therefore, the local government needs to take corresponding measures. Biomass burning activities in Myanmar had an impact on VOCs concentration changes in Jinghong, and cross-border pollution issues also need attention, which has a certain guiding significance for our government to carry out international cooperation projects in Southeast Asia.

**Author Contributions:** Conceptualization, J.S. and X.H.; investigation, Z.W. and L.R.; resources, J.W. and F.X.; data curation, X.P.; writing—original draft preparation, Y.B.; writing—review and editing, J.S. and X.H.; supervision, P.N. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was partially supported by the National Natural Science Foundation of China (grant number 21966016), the National Key R&D Program of China (grant number 2019YFC0214405), and the Science and Technology Special Project of Demonstration Zone for National Sustainable Development in Yunnan (grant number. 202104AC100001-A14).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data used in this paper can be provided by Jianwu Shi (shijianwu@kust.edu.cn).

**Acknowledgments:** This work was partially supported by the National Natural Science Foundation of China, the National Key R&D Program of China (No. 2019YFC0214405), and the Science and Technology Special Project of Demonstration Zone for National Sustainable Development in Yunnan.

**Conflicts of Interest:** The authors declare that there are no competing financial interests that could inappropriately influence the contents of this manuscript.
