[Distribution and partition of polycyclic aromatic hydrocarbons (PAHs) in the Gaoyao section of Xijiang River].

To obtain the seasonal and vertical distribution and partition of PAHs between dissolved phase and particle phase in Xijiang River basin, water columns were collected during flood seasons (August, 2003 and July, 2004) and dry seasons (November, 2003 and Mar, 2004) from Gaoyao section of Xijiang River. The average PAHs concentrations in dissolved phase and particle phase were 21.7-138 ng x L(-1), 40.9-664.8 microg x kg(-1), respectively. Total PAHs concentrations (both particle phase and dissolved phase) were higher in flood seasons than that in dry seasons. No variation was found for dissolved PAHs in vertical distribution. However, a same trend of vertical distribution was observed for particle PAHs with the maximum concentration in middle layer and minimum in surface layer of water column. With increasing of content of suspended particle matter (SPM), both dissolved and particle PAHs concentration increased. In the dissolved phase, the predominant PAHs were 3 ring PAHs. While in the particle phase, 3-4 ring PAHs were the dominant PAHs. The partition coefficient (K(p)) had no correlation with the particle organic carbon content of SPM (R2 0.000 1-0.2), but influenced by concentrations of suspended particle matters and dissolved organic carbon, especially black carbon in dissolved phase (R2 0.15 -0.36). A majority of values of lg K(oc) in different seasons exceeded upper limit based on typical model of equilibrium distribution. Except the season of November 2003 (R2 0.000 4-0.12, p < 0.001), the organic carbon normalized distribution coefficients (K(oc)) computed for the PAHs were correlated well with their octanol-water partition coefficient (K(ow))(R2 0.29-0.91, p < 0.05). The lipophilic ability of SPM was stronger in flood seasons than that in dry seasons.