北京东南郊大气降尘中的多环芳烃

Polycyclic Aromatic Hydrocarbons in Dustfall in the Southeastern Suburb of Beijing, China

对2005-03—2006-01北京市东南郊4个采样点约10个月的降尘样品进行采集,利用索氏提取法提取样品中16种美国EPA优控多环芳烃(PAHs),并利用GC-MS对其定量。结果表明,16种PAHs组分在4个采样点全年的降尘样品中均能检出,浓度最大和最小的组分分别为PHE和DahA,年平均值分别为2017.36和2.55ng·g^(-1),降尘样品中16种PAHs组分浓度之和范围在713.63￣40448.38ng·g^(-1)之间。通州区境内降尘以及降尘样品中16种多环芳烃(PAHs)的沉降通量分别为466.8t·km^(-2)·a^(-1)和1.85kg·km^(-2)·a^(-1)。降尘及PAHs的沉降通量存在着明显的季节变化,分别为春季>冬季≈夏季>秋季,冬季>春季>秋季>夏季的趋势。地面扬尘作用可以对降尘中PAHs浓度产生一定的稀释作用,降尘中PAHs浓度与SO2的API指数呈显著正相关关系。风速和风向对降尘的沉降速率和降尘中PAHs浓度的影响比较复杂。

Dustfall samples were collected at 4 sampling sites in the southeastern suburb of Beijing from March, 2005 to January, 2006. 16 USEPA priority PAHs in dustfall samples were extracted by acetone and cyclohexane （1：1） for 20 h at 72 ℃ using soxhlet extraction, then detected by GC-MS. All the 16 PAHs compounds could be detected in all samples, and the maximum and minimum compounds were PHE and DahA with concentrations of 2 017.36 and 2.55 ng·g^-1, respectively. Total concentration of 16 compounds in dustfall samples ranged from 713.63 to 40 448.38 ng·g^-1. The fluxes of dustfall and PAHs were 466.8 t·km^-2·a^-1 and 1.85 kg·km^-2·a^-1, respectively, and they followed the orderofspring〉winter^summer〉autumnandwinter〉spring〉autumn〉summer, respectively. The ground dust had a dilution impact on the concentrations of PAHs in dusffall samples, and it had a larger effect in winter and spring than in summer and autumn in Beijing. PAH concentration in dustfall had a significant positive correlation with SO2 API, and it might be caused by the similar sources of PAHs and SO2. Wind speed had a complex effect on the deposition velocity. When wind speed was less than 5 m· s^-1, deposition velocity decreased with the increase of wind speed, but increased with the increase of wind speed when wind speed was more than 5 m· s^-1.