南京及周边黑碳气溶胶对臭氧影响的观测分析和数值模拟

Observation alanalysis and numerical simulation of effect of black carbon on ozone in Nanjing and its surrounding areas

摘要:

利用南京地面站点2016—2017年黑碳气溶胶（Black Carbon，BC）和臭氧（O₃）逐小时观测资料，对比分析了不同季节BC与近地面O₃的关系。结果表明，高BC（高于平均值）影响下的O₃质量浓度值明显比低BC（低于平均值）影响下的O₃质量浓度值低，这种抑制作用在秋冬季明显高于春夏季，且BC与O₃的负相关性在秋冬季显著高于春夏季，而PM_2.5与O₃的负相关性不显著。利用WRF-Chem模式，对2017年12月个例开展BC反馈效应对O₃影响的数值模拟，结果再次证实BC对O₃存在负反馈影响。其影响机制是：BC可通过抑制边界层发展，使近地面NO_x积聚，从而减少臭氧的化学生成（VOCs控制区）；BC可通过抑制边界层垂直湍流交换，减少边界层上部高O₃向下的湍流输送，从而减少近地面O₃；BC可通过减小近地面风速，减少O₃的平流输入，从而减少地面O₃。不同个例的主要控制因子不同。

Abstract:

Based on the hourly observation data of black carbon (BC) and ozone (O₃) at Nanjing ground station from 2016 to 2017, the relationship between BC and near surface O₃ in different seasons was analyzed.Results shows that the O₃ value under the influence of high BC (higher than average) is significantly lower than that under the influence of low BC (lower than average).The inhibition effect is obviously stronger in autumn and winter than in spring and summer, and the negative correlation between BC and O₃ is significantly higher in autumn and winter than in spring and summer, while the negative correlation between PM_2.5 and O₃ is not significant.Based on the WRF-Chem model, the numerical simulations of BC feedback effect on O₃ are carried out for the cases in December 2017, and the results confirm that BC has negative feedback effect on O₃.The influencing mechanisms are as follows:BC can reduce the photochemical production of ozone (VOCs control area) by inhibiting the development of boundary layer and accumulating NO_x near the ground;BC can reduce the downward turbulent transport of high O₃ in the upper part of the boundary layer by suppressing the vertical turbulent exchange in the boundary layer, so as to reduce O₃ near the ground;BC can reduce the advection input of O₃ from upwind region by reducing the near ground wind speed, so as to reduce the ground O₃.The main control factors of the cases are different and should be analyzed in detail.