北京城区大气多环芳烃的沉降特征

Deposition of Atmospheric PAHs in Urban Area of Beijing

从2006年6月至2007年6月期间采集了北京市区的降尘和大气TSP,分析了其中的PAHs和降尘的粒度。降尘颗粒大部分在100μm以下,体积平均径和中位径D50的范围分别为18.89-53.117μm和11.59-28.98μm。全年降尘平均沉降通量为0.451 9 t/（km2.d）,冬季高,夏秋季低;∑16PAHs的沉降通量平均为4.76 g/（km2.d）,冬季高,夏季低,与同期的大气SO2的API指数显著相关。TSP中的∑16PAHs与降尘中的∑16PAHs具有显著的相关关系,成分谱一致。PAHs的沉降速率变化范围为0.004-5.46 cm/s,夏季高、冬季低。交通沿线∑16PAHs的沉降通量远远高于非交通线的沉降通量。

Dustfall and TSP samples were collected from June,2006 to June,2007.Sixteen USEPA priority PAHs in dustfall and TSP samples were analyzed.The sizes of the dustfall were also measured.The sizes of most of the dustfall particles were below 100 μm.The volume of averaged sizes ranged between 18.89 and 53.117 μm,while the median sizes were between 11.59 and 28.98 μm.The deposition flux averaged at 0.451 9 t/（km2·d）,and it was higher in winter than in summer and autumn.The average deposition flux of ∑16PAHs was 4.76 g/（km2·d）,and deposition flux was higher in winter than in summer.The deposition flux showed a significant positive correlation with API index of SO2.The profile of PAHs in dustfall was consistent with that in TSP,and ∑16PAHs in dustfall correlated with that in TSP significantly.The deposition velocity of PAHs ranged between 0.004 and 5.46 cm/s,with higher velocity in summer than in winter.The deposition flux of ∑16PAHs was much higher along traffic road than in non-traffic sites.