Polycyclic aromatic hydrocarbons in riverine runoff of the Pearl River Delta (China): concentrations, fluxes, and fate.

On the basis of a monthly sampling effort from March 2005 to February 2006, the total concentrations of the sums of 27 and 15 polycyclic aromatic hydrocarbons (defined as sigma27PAHs and sigma15PAHs, respectively) in riverine runoff of the Pearl River Delta (PRD), China, and associated fluxes were determined. No clear temporal and spatial trends of PAH concentrations were found at all eight riverine runoff outlets where the samples were collected. The annual fluxes of sigma27PAHs and sigma15PAHs from the PRD to the coastal ocean were 60.2 and 33.9 metric tons, respectively. Assuming that riverine flux was positively related to the regional emission of PAHs, the annual riverine fluxes from five major rivers in China to the global oceans were estimated, which are quite significant relative to other major rivers of the world. On the basis of mass balance considerations, approximately 87% of sigma15PAHs inputting to the Pearl River Estuary and northern South China Sea was derived from riverine runoff from the PRD. In addition, approcimately 22.3 metric tons of sigma15PAHs annually outflow to open seas, which is equivalent to a concentration of 0.34 pg/L in the global oceans if the PAHs are evenly distributed in the upper 200 m of the water column. A comparison with the global background level of PAHs indicated that approximately 0.4% of PAHs in the open oceans may have been contributed by 1-year discharge from the PRD.