The authors use the high-frequency sampling function of the fine particle mass concentration measurement instrument E-Sampler and the eddy covariance method to calculate PM_2.5 concentration fluctuation and turbulent flux of the multiple pollution events of the Dezhou city atmospheric environment experimental station in Shandong Province from December 27, 2018 to January 7, 2019, and the turbulence characteristics of PM_2.5 concentration are discussed. The results show that the mean value of the turbulent flux of PM_2.5 concentration during the observation period is 0.026 μg/(m²·s). The transmission direction of the turbulent flux of PM_2.5 concentration in different pollution processes is different, indicating that the sink or source property is not static. With the increase of turbulence statistical characteristic quantities (such as turbulent kinetic energy, standard deviation of horizontal wind speed, standard deviation of vertical wind speed, horizontal wind speed, momentum flux and sensible heat flux), the vertical flux of PM_2.5 decreases exponentially, namely, it decreases sharply, and then changes little with the increase of each variable. With the increase of the concentration of PM_2.5, the absolute value of the turbulent flux of PM2.5 shows an increasing trend. The turbulent vertical flux of PM_2.5 concentration is related to the PM_2.5 concentration and the intensity of turbulence. The normalized standard deviation of PM_2.5 concentration and the stability parameter ζ = z/L follow the -1/3 power relationship under unstable conditions, that is σ_c/C_* = 6.7(-ζ)^-1/3. Under stable conditions, the experimental results are relatively discrete. In addition, the variance spectrum curve of PM_2.5 concentration satisfies the -2/3 power exponential rate in the high frequency range, and the covariance spectrum curve of the PM_2.5 concentration and the vertical wind speed satisfies the ?4/3 power exponential rate in the high frequency band. The result shows that 1 Hz high-frequency sampling function of E-Sampler can obtain continuous and effective turbulent flux of PM_2.5 concentration.

利用PM_2.5质量浓度测量仪E-Sampler的1 Hz高频采样功能, 采用涡动相关法, 计算山东省德州大气环境实验站2018年12月27日至2019年1月7日多次污染事件的PM_2.5浓度脉动和湍流通量, 探讨PM_2.5浓度湍流特征。结果表明, 实验观测期间PM_2.5浓度湍流通量均值为0.026 μg/(m²·s); 不同污染过程中PM_2.5浓度湍流通量传输方向不同, 表明不同污染过程的污染源汇属性不同。随着湍流统计特征量(如湍流动能、水平风速标准差、垂直风速标准差、水平风速、动量通量和感热通量)增大, PM_2.5湍流垂直通量呈现指数型减小的趋势, 即先急剧减小, 然后随各变量的增长变化不大。随着PM_2.5浓度增大, 其湍流通量绝对值呈现增加趋势, 因此PM_2.5浓度湍流通量的大小与PM_2.5浓度和湍流强弱有关。不稳定条件下, PM_2.5浓度归一化标准差与稳定度参数ζ = z/L 遵循-1/3幂次关系, 即 σ_c/C_* = 6.7(-ζ)^-1/3; 稳定条件下, 实验结果相对离散。另外, PM_2.5浓度脉动方差谱曲线在高频段满足-2/3幂指数率, PM_2.5浓度脉动与垂直速度脉动的协方差谱曲线在高频段满足-4/3幂指数率。研究结果表明, 利用E-Sampler的PM_2.5浓度1 Hz高频采样功能可以得到连续且有效的PM_2.5浓度湍流通量。