城市灰尘PAHs累积与迁移过程的影响因素研究

以上海市为例,探讨了城市中心城区地表灰尘中多环芳烃(PAHs)累积与迁移过程的影响因素.结果表明,粒度只是影响城市灰尘吸附PAHs的一个次要因子,与PAHs含量之间没有明显的相关关系.城市灰尘TOC与PAHs含量显著正相关(冬季r=0.62,p＜0.000 1;夏季r=0.55,p=0.002),说明对于城市地表灰尘而言,有机质的含量越高,其吸收PAHs的能力就越强,这种结果与理论上PAHs的憎水亲脂性相一致.风向能够直接影响PAHs在空间上的分布趋势,污染源下风向的地区更容易累积较多的PAHs,且距离污染源越近,污染程度越重,相反,污染源上风向的地区则不利于PAHs的累积,污染程度较轻.夏季最高值出现在西北城区,含量为27 766 ng·g-1,冬季最高值出现在南部和东部城区,含量分别为30 741 ng·g-1和32 573 ng·g-1.大城市中心区存在PAHs污染的"空心效应".温度是影响城市灰尘PAHs累积与迁移的重要气象参数.

Effective Factors on Accumulation and Transportation of PAHs in Road Dust from Shanghai

The influencing factors on the accumulation and transportation of PAHs (polycyclic aromatic hydrocarbons) in road dust from Shanghai city were systematically discussed. The results showed that grain size was only a minor factor affecting the adsorption of PAHs by urban road dust, and there was no obvious correlation between grain size and PAHs concentrations. TOC (total organic carbons) was significantly correlated with PAHs concentration (r = 0.62, p < 0.0001; r = 0.55, p = 0.002 for winter and summer, respectively), which suggested that for urban road dust, the higher the organic matters were, the stronger the adsorption capacity was. The result was consistent with the hydrophobic characteristic of PAHs theoretically. Wind direction significantly influenced the accumulation and transportation of PAHs in urban road dust. Wind direction could directly affect the spatial distribution of PAHs, which led the leeward was ready to accumulate less PAHs while the windward was likely to accumulate more. In summer, the highest concentration existed in northwest of Shanghai, with a value of 27,766 ng x g(-1), and in winter, the south and east of Shanghai were the most polluted areas, with values of 30,741 ng x g(-1), 32,573 ng x g(-1), respectively. And the "Hollow Effect" was found at urban centre area. Temperature was an important factor affecting the accumulation and transportation of PAHs in urban road dust.