Riverine runoff is an important mode to transport anthropogenic pollutants from terrestrial sources to oceans. Polybrominated diphenyl ethers (PBDEs) were measured in riverine runoff samples from the eight major outlets within the Pearl River Delta (PRD), China, an economically fast developing region housing a vast number of electronics manufacturing and assembling plants. The sigma 17PBDEs (sum of 17 BDE congeners, i.e., BDE-28, -47, -66, -85, -99, -100, -138, -153, -154, -183, -196, -197, -203, -206, -207, -208, and -209) concentrations varied from 344 to 68,000 pg/L, with those of BDE-209, BDE-47, and BDE-99 being 335-65200, 3-143, and <1-200 pg/L, respectively. These levels were in the high end of the global PBDEs concentrations in the aquatic environments. The monthly inputs of sigma 17PBDEs ranged from 0.21 to 215 kg at individual outlets, and the annual input of sigma 17PBDEs from all the outlets was estimated at 2140 kg/year. Of the target BDE congeners, BDE-209 was the most predominant component with an annual input of 1960 kg/year, followed by BDE-47 (13.3 kg/year) and BDE-99 (11.7 kg/year). An extrapolation of the past use of PBDEs in the region concluded that 23 metric tons of sigma 17PBDEs have been discharged into the coastal ocean from the PRD in the last 20 years. The amount of PBDEs imported to China in the form of e-waste was estimated at 35000 metric tons/year, higher than the annual domestic production of brominated fire retardants (approximately 10000 metric tons/year) and the annual riverine input of total PBDEs from the PRD, suggesting that the majority of PBDEs inventory has been accumulated from importation of e-wastes. Because of the continuous importation of e-wastes and strong demand for brominated fire retardants, the impact of PBDEs on China's and the world's environments is expected to persist for many years to come.

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.

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Sources, compositions, and historical records of polycyclic aromatic hydrocarbons (PAHs) in sediment cores collected from the Yellow Sea and the South China Sea were analyzed to investigate the influence of anthropogenic activities. The occurrence of PAHs was mainly derived from various combustion sources, especially the combustion of biomass and domestic coal. Uniform composition of sedimentary PAHs (52−62% of phenanthrene, benzo[b]fluoranthene, indeno[1,2,3-cd]pyrene, and benzo[g,h,i]perylene) suggested air-borne mixtures intractable to degradation. The concentrations of the sum of 15 PAHs (16 priority pollutants designed by the United States Environmental Protection Agency minus naphthalene; designed as Σ 15 PAH) in Yellow Sea sediment cores were generally higher than those in the South China Sea. The profiles of Σ 15 PAH concentrations recorded in the sediment cores closely followed historical socioeconomic development in China. In general, Σ 15 PAH concentrations started to increase from the background pollution level posed by agricultural economy at the turn of 20th century. In addition, a Σ 15 PAH concentration reduction was observed during the Chinese Civil War (1946−1949) and Great Cultural Revolution (1966−1976, suggesting them as setbacks for economic development in Chinese history. Increasing PAH emissions as a result of increasing coal combustion associated with the rapid urbanization and industrialization since the implementation of the Reform and Open Policy (since 1978) accounted for the fast growth of Σ 15 PAH concentrations in sediment cores. The decline of Σ 15 PAH concentrations from subsurface maximum until sampling time was inconsistent with current-day economic development in China, and may possibly suggest emission reductions due to decreasing proportional use of domestic coal and increasing consumption of cleaner energies (natural gas and liquefied petroleum gas).

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On the basis of a one-year (from October 2006 to September 2007) sampling campaign, 34 air samples and 23 bulk precipitation samples were collected in the Pearl River Delta (PRD) in southern China and analyzed for polybrominated diphenyl ethers (PBDEs). Fifteen tri- to deca-BDE congeners (sum of which is defined as Sigma15PBDE) were detected in more than 70% of the samples. In three urban-rural regions, Sigma15PBDE concentrations ranged from 77 to 372 pg/m3 in air (particulate + vapor) and 1.98 to 15.5 ng/L in rain (particle+dissolved) from Dongguan, from 195 to 1450 pg/m3 in air and 4.71 to 17.2 ng/L in rain from Shunde, and from 23.7 to 148 ng/L in rain from Guangzhou. Among the BDE congeners, BDE-209 was the predominant component. Linear correlations between the gas-particle partition coefficients (Kp) and the subcooled vapor pressures (P(O/L)) of individual BDE congeners were observed for both the wet and dry seasons, but the slopes (-0.572 to -0.525) of the fitted equations all substantially deviated from equilibrium condition (slope = -1). The total washout ratio by bulk rainfalls was determined to be 2 x 103 for tri-BDEs and 6 x 104 for BDE-209. The estimated annual dry and wet depositional rates were 6720 and 2460 kg/yr, respectively, for BDE-209, and 7270 and 2940 kg/yr for Sigma15PBDE in the PRD, indicating a dominant pathway for PBDEs input into the PRD soil and aquatic environments.

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