玉龙雪山PM2.5稳定碳同位素特征及来源分析

于2020年4~8月在青藏高原东南部玉龙雪山进行PM_2.5采样,共采集44个样本,测定其水溶性离子成分、水溶性有机碳(WSOC)浓度、总碳(TC)浓度及其稳定碳同位素组成(δ¹³C_TC).结果表明,玉龙雪山春夏季TC浓度分别为(7.1±3.8)μg/m³和(2.9±0.7)μg/m³,WSOC浓度分别为(3.3±2.1)μg/m³和(1.5±0.4)μg/m³,均呈现春高夏低的变化趋势.春夏季δ¹³C_TC值分别为(-24.7±1.0)‰和(-26.0±0.6)‰,春季较夏季偏正,表明可能受到不同来源影响.通过对非海盐钾离子(nss-K⁺)相关性、NASA火点图及后向轨迹分析可知,东南亚地区春季生物质燃烧可能是主导原因.利用贝叶斯模型计算玉龙雪山PM_2.5中TC来源贡献,结果表明春季主要来源于生物质燃烧和煤燃烧,贡献比分别为60.6%和23.5%;夏季主要来源于生物质燃烧、植物蒸发和机动车排放,同时二次有机气溶胶形成对TC的贡献也不可忽视.

Composition characteristics of chemical and stable carbon isotopes in PM2.5 of Yulong Snow Mountain

In this study, PM_2.5 samples were collected in the Yulong Snow Mountain in the southeastern Qinghai-Tibet Plateau from April to August 2020. A total of 44 samples were taken to measure the composition of water-soluble ions, the concentration of water-soluble organic carbon (WSOC), the concentration of total carbon (TC), and alongside the composition of stable carbon isotope (δ¹³C_TC). As measured, the TC concentrations of Yulong Snow Mountain in spring and summer were (7.1±3.8) μg/m³ and (2.9±0.7) μg/m³respectively, and the WSOC concentrations (3.3±2.1) μg/m³ and (1.5±0.4) μg/m³, showing a trend as high in spring and low in summer. The δ¹³C_TC values in spring and summer were measured as (-24.7±1.0)‰ and (-26.0±0.6) ‰ respectively, which were more positive in spring than in summer, indicating that the value difference may be affected by different sources. As suggested by analysis of nss-K⁺correlation, FIRMS of NASA, and backward trajectory, biomass burning in Southeast Asia in spring may serve as the dominant contributor. Besides, the Bayesian model was also utilized to calculate the contribution of TC sources to PM_2.5 in Yulong Snow Mountain. The results pointed that biomass burning and coal combustion accounted for the main sources in spring, with contribution rates of 60.6% and 23.5% respectively. Whereas in summer, TC mainly comes from biomass burning, plant evaporation, and vehicle emissions, together with the formation of secondary organic aerosol whose contribution cannot be ignored.