[Distribution characteristics of polycyclic aromatic hydrocarbons in runoff from the middle line source area of south-to-north water diversion project].

The distribution characteristics of polycyclic aromatic hydrocarbons in runoff from the middle line source area of south-to-north water diversion project were studied. Five groups of artificial runoff fields were established to collect runoff based on the different types of land-use, the contents of 16 USEPA priority PAHs in the runoff were determined using GC/MS method. The results showed that the average concentrations of PAHs of the aqueous phase in the collected runoff samples of different land-use types decreased in the order:cultivated land (26.53 ng x L(-1)) > oak forest (20.91 ng x L(-1)) > orchard (17.59 ng x L(-1)), and the average concentrations of PAHs of the particle phase were cultivated land (1 073.72 ng x g(-1)) > orchard (652.29 ng x g(-1)) > oak forest (385.46 ng x g(-1)). The high carcinogenic components Bap were detected in both run off of cultivated land and orchard with a detected rate of 30%. According to National Recommended Water Quality Standards of priority toxic pollutants (2006 USEPA), it was found that Chr exceed standard 40%, with a detected rate of 100%. It was also found that the runoff volume and the total PAHs content in runoff increase with the slope, and PAHs loss and slope were closely related in same land-use types. Based on the Molecular Markers Indicative Law, it can be concluded that the dominant source of PAHs in runoff of study area was combustion of coal, and a small amount came from vehicle exhaust emissions. There is a certain degree of ecological risk about runoff PAHs pollution in the study area, which is worth further attention.