青藏高原东缘气溶胶粒径分布特征及其来源

气溶胶粒径分布可反映气溶胶的主要来源及其经历的动力学和化学等过程。使用宽范围粒径谱仪对青藏高原东缘四川省理塘县2017年7月6日至8月3日10 nm～10 μm气溶胶粒径分布进行观测,结合环保六要素(PM_2.5、PM₁₀、SO₂、NO₂、CO和O₃)和气象要素数据、HYSPLIT轨迹模式、潜在源区贡献函数(PSCF)和浓度权重轨迹(CWT)分析,探讨了青藏高原东缘气溶胶的粒径分布特征、潜在来源和影响区域。结果表明:青藏高原东缘理塘地区气溶胶数浓度较低,平均值为4 660.3 cm^-3,粒径分布主要集中在500 nm以下,占总数浓度的99.95%; 不同模态粒子数浓度差异较大,核模态、爱根核模态、积聚模态和粗模态粒子数浓度分别为391.9、4 218.0、50.1和0.4 cm^-3; 不同模态粒子数浓度日变化均为双峰型分布,但是峰值时间存在差异,核模态粒子数浓度日变化的峰值时间位于12:00和19:00,爱根核模态、积聚模态和粗模态粒子数浓度日变化的峰值时间位于08:00和20:00; 气溶胶数浓度谱和表面积浓度谱均为单峰型分布,峰值分别位于50 nm和170 nm,峰值浓度分别为7 361.9 cm^-3·nm^-1和215.5 μm²·cm^-3·nm^-1。青藏高原东缘气溶胶数浓度的潜在来源高值区主要分为两个区域,即东北部的局地污染区和西南部的境外远距离传输区。青藏高原东缘气溶胶数浓度的影响范围主要集中在中国境内,影响区域的高值区相对比较分散。

Size Distributions and Sources Apportionment of Aerosol Number Concentrations over the Eastern Qinghai-Tibet Plateau,China

The spatio-temporal variation of aerosol size distribution, which indicates the primary and secondary sources of atmospheric aerosols, can reflect the dynamic and chemical processes that they were subjected to. A wide-range particle size spectrometer was used to observe the aerosol size distributions(10 nm-10 μm)in Litang county of Sichan province over the eastern Qinghai-Tibet Plateau from July 6 to August 3, 2017. Combining with the data of six atmospheric pollutants(PM_2.5, PM₁₀, SO₂, NO₂, CO, and O₃), meteorological elements, trajectory model of HYSPLIT, potential source contribution function(PSCF)and concentration-weighted trajectory(CWT)analysis, the size distributions, potential sources and affecting areas of aerosols on the eastern margin of Qinghai-Tibet Plateau were discussed. The results show that the average aerosol number concentration is 4 660.3 cm^-3 in Litang area, and mainly concentrates below 500 nm, which accounts for 99.95% of total number concentration; the aerosol number concentrations in different modes of particle vary greatly, that of nucleation mode, Aitken mode, accumulation mode, and coarse mode of particle are 391.9, 4 218.0, 50.1, and 0.4 cm^-3, respectively; meanwhile, the diurnal variations of aerosol number concentration in different modes of particle are all bimodal distributions, with a discrepancy in the peak time, which is located at 12:00 and 19:00 for the nucleation mode of particle, and at 08:00 and 20:00 for the Aitken mode, accumulation mode and coarse mode of particle; the spectrum of aerosol number concentration and surface area concentration has both unimodal distributions with peaks at 50 nm and 170 nm, respectively, the peak concentrations of which are 7 361.9 cm^-3·nm^-1 and 215.5 μm²·cm^-3·nm^-1, accordingly. Finally, the potential sources of aerosol number concentration with high PSCF values in Litang area include two areas, which are a local polluted region in the northeast and a foreign region in the southwest triggered by the long range transport process. Conversely, the affecting areas of the aerosol number concentration in the eastern Qinghai-Tibet Plateau are mainly in the domestic region, and the affecting areas with high PSCF value are relatively scattered.