东亚季风区近地面大气气溶胶中OCPs和PCBs纬度分布：以7Be为参照系

摘要

连续一年在北京、青岛、广州以每周3 d的时间尺度同步采集近地面大气中气溶胶中7Be的测定数据以及在春、秋季节变换时期我国5个不同纬度城市大气气溶胶中7Be和典型持久性有机污染物(有机氯农药和多氯联苯)的同步观测数据，并对文献上发表的我国其他城市近地面大气中气溶胶中7Be 年平均值数据进行了分析。通过对以上数据资料的总结和分析，观察到在东亚季风区近地表大气气溶胶中7Be浓度的年平均值呈现正态分布模式，并且在中纬度北纬40°N附近达到极大值。大气气溶胶中7Be在春、秋季节变换时期我国不同纬度城市的瞬时纬度分布仍呈现正态分布模式，但以30°N为最大值。在秋季大气颗粒相中HCHs和PCBs浓度最大值出现在30°N。气相中PCB-28所占百分比随纬度增高而增大，而颗粒相中PCB-28的纬度变化不大。，蒸汽压较低的PCB-180在气相中的浓度基本上不随纬度变化，而颗粒相中PCB-180则基本上集中在纬度36°N 左右，表明在东亚季风区大气中挥发性较低的 POPs 化合物具有某种纬度聚焦作用。以宇宙射线成因核素7Be 作为大气环流的参照系，可以得出东亚季风区大气环流可影响持久性有机污染物纬度分布的结论。%Using the cosmogenic nuclide 7Be as a reference, here we show that the atmospheric circulation in East Asian monsoon climate system (EAMCS) can affect the latitudinal distributions of POPs. Beryllium-7 (7Be) concentrations in near-surface atmospheric aerosols at sampling frequency of 3 d per week for one year in Beijing, Qingdao, and Guangzhou are summarized. Simultaneous measurements of 7Be, organochlorine pesticides (OCPs), and polychlorinated biphenyls (PCBs) at five different latitude cities in EAMCS were conducted during the seasonal transition period of spring and autumn. We observed that the latitudinal distribution of the annual average 7Be concentrations follows a normal distribution pattern, with the maximum occurring at ~40°N. The instantaneous observation of 7Be at different latitude sampling sites in EAMCS also showed a normal distribution pattern, but with the maximum at 30°N in spring and autumn. The maximum concentrations of OCPs and PCBs in near-surface aerosols occurred at different latitude showed a similar pattern as that of 7Be, i.e. with the maximum at 30°N. The abundance of PCB-28 in vapor phase increased with latitude but nearly unchanged with latitude in aerosols. PCB-180, which has low evaporation tendency, in aerosols showed enrichment at 36°N, while PCB-180 in vapor phase appeared to be nearly unchanged with latitude. Our results suggest a latitude-focused accumulation mechanism for POP compounds with lower volatile tendency in the atmosphere in EAMCS. Using cosmogenic nuclide 7Be as a reference, the conclusion that atmospheric circulation in EAMCS may influence the latitudinal distribution of POPs can be made.