Volatile organic compounds at a highland forest site in the southeast of the Tibetan Plateau: Source apportionment and reactivity contributions

• Published in: Environmental pollution (1987) 2025-02, Vol.366, p.125410, Article 125410
• Main Authors: Guo, Shuzheng, Ye, Chunxiang, Lin, Weili, Chen, Yi, Zeng, Limin, Yu, Xuena, Cui, Jinhui, Zhang, Chong
• Format: Article
• Language: English
• Subjects: Biogenic sources; OVOC contributions; Oxygenated volatile organic compounds; Sunlight-impacted sources
• ISSN: 0269-7491; 1873-6424; 1873-6424
• DOI: 10.1016/j.envpol.2024.125410

Atmospheric volatile organic compounds (VOCs) are reactive species and the primary precursors of free radicals; thus, VOCs play important roles in tropospheric chemistry. Tibet field campaigns from April 4 to May 11, 2021 found high mixing ratios and reactivity contributions of oxygenated VOCs (OVOCs) at Lulang, a site with high vegetation cover and strong solar ultraviolet radiation on the southeast of the Tibetan Plateau (TP). The 13 OVOCs detected accounted for 49% of the total VOCs (TVOCs, with a mean mixing ratio ±1σ of 11.7 ± 4.4 ppb）. These OVOCs exhibited typical diurnal variation, with high values in the daytime and a peak at approximately 12:00. OVOCs contributed 65% and 63% to VOC-kOH and the ozone formation potential, respectively. Two independent methodologies were employed to determine the contributions of various sources and revealed concordant conclusions regarding the importance of biological sources there. The source apportionment results obtained through positive matrix factorization indicated that sunlight-impacted and direct plant emission sources both related to plant sources contributed 47% of the TVOCs and 65% of the OVOCs. OVOC source fitting through the photochemical age parameterization method also indicated that biogenic sources made the largest contribution (67%) to OVOCs and revealed a clear peak at noon. In addition, biomass burning sources were found to be closely related to the VOC background because biomass burning is highly prevalent across the whole TP; these sources made the second greatest contribution (33%) to the TVOCs and contributed more than 23% of OVOCs. Our findings enhance comprehension of VOCs in the highland forest region, potentially impacting tropospheric chemistry significantly. [Display omitted] •OVOC mixing ratios constituted up to 49% of TVOCs in SE Tibet.•Sunlight-impacted biogenic sources contributed 58% to OVOCs.•Two methods confirmed biogenic dominance of OVOCs and peaking midday.