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 27766 ng·g^-1, and in winter, the south and east of Shanghai were the most polluted areas, with values of 30741 ng·g^-1, 32573 ng·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.