天津夏季边界层低层大气中PAN和O3的输送特征分析

采用在线仪器监测分析2017年夏季天津气象铁塔220 m观测平台大气中过氧乙酰硝酸酯(PAN)和O_3的体积分数,并结合气象观测资料和后向轨迹分析PAN和O_3的输送特征.观测期间PAN和O_3体积分数平均值分别为(0.73±0.56)×10~(-9)和(53±25)×10~(-9),最大小时体积分数分别为3.49×10~(-9)和137×10~(-9),PAN和O_3体积分数具有相似的日变化特征,白昼PAN和O_3浓度高于夜间,且PAN和O_3浓度相关系数(R2=0.52)显著高于夜间(R2=0.21).观测期间偏南风下PAN和O_3浓度最高,偏东风下最低,风玫瑰图和后向轨迹聚类分析都表明,来源于西南方向的气流轨迹对应的污染物浓度最高,途经渤海和河北、辽宁沿海地区的偏东气流对应的PAN和O_3体积分数最低,边界层内输送对PAN和O_3的体积分数分布起到了重要作用.

Transport Characteristics of PAN and O3 in the Lower Atmosphere of the Boundary Layer in Tianjin in Summer

The volume concentration of peroxyacetyl nitrate (PAN) and O₃ in the atmosphere were measured at the Tianjin Meteorological Tower in summer 2017 by using the online instrument with meteorological parameters and back trajectory analysis to analyze the delivery characteristics of PAN and O₃. The average volume concentrations of PAN and O₃ during the observational period are (0.73±0.56)×10^-9 and (53±25)×10^-9, respectively. The hourly maximum concentrations of PAN and O₃ are 3.49×10^-9 and 137×10^-9. The volume concentrations of PAN and O₃ show pronounced diurnal profiles, which are both characterized by much higher values at daytime than at nighttime. In addition, the correlation coefficient between PAN and O₃ at daytime (R²=0.52) is notably higher than that at nighttime (R²=0.21). The air masses originating from the south show the highest volume concentration of PAN and O₃, with the lowest volume concentration originating from the east. The wind rose plot and cluster analysis of the back trajectories show that the highest concentration of pollutants mainly originates in the southwest. The air massess originating from the east and circulating through the Bohai Sea and coastal areas of the Hebei and Liaoning provinces show the lowest volume concentrations of PAN and O₃. The transportation within the boundary layer plays an important role in the concentration distribution of PAN and O₃.