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Abstract: The contamination status of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (DL-PCBs) was preliminarily investigated in surface sediments collected from the East River during April 2007. The contamination levels of PCDD/Fs and DL-PCBs ranged from 2.1 to 9.8 with mean concentration of 4.5pg WHO98-TEQg−1 and ranged from 0.042 to 0.45 with mean concentration of 0.19pg WHO98-TEQg−1, respectively. All sediments were characterized by the elevated levels of PCDDs, especially OCDD. Higher concentrations of PCDD/Fs were found in the sediments from Guangzhou and Dongguan. Source analysis revealed that PCDD/Fs in the sediments from Guangzhou were mainly from the secondary copper smelters and steel-making plants, and PCDD/Fs in the sediment from Dongguan were mainly from MSWIs. PCP and paper mills were unlikely to be the main sources. [Copyright &y& Elsevier]

Abstract: Stream sediments play an important role in the transport and storage of phosphorus in the stream ecosystems. This research investigated the sorption and fraction of P in the sediments of a long-term seriously contaminated river, the Daliao river system, using isotherm sorption and selective sequentially extraction tests. Results indicated that the total content of P in the sediments was 479–1202mgkg−1, depending on iron content in the sediments. The content of potential bioavailable P, including soluble and loosely bound P, Al bound P, Fe bound P, and reductant soluble P was only 10–20% of total P in the sediments of the Hun river and Taizi river, while it was 40–55% in the sediments of the Daliao river, the downstream of the river system. Equilibrium phosphorus concentration without net P sorption (EPC0) was from 0.05 to 0.54mgL−1, with an increasing trend from upstream to downstream, indicating increasingly release potential. On the other hand, the upstream sediment generally sorbed more P than the downstream sediment for each river at the same equilibrium P concentration. The binding energy constant of P on the strong sites of the sediments generally decreased from 2.24 to 2.65Lmg−1 at upstream to 0.41Lmg−1 at downstream or estuary, suggesting that the strong binding sites have been occupied and partly saturated by the phosphate added by point and diffuse sources along the river. On the other hand, molar ratio of Fe to TP contents in the sediments showed sorption capacity of the sediments to P might be under-saturated. The added or sorbed P by the isotherm test was primarily bound to Fe oxides and secondly to Al oxides. Long-term pollution of the river lead to the decrease of P sorption capacity of the river sediment and the increase of P release potential. [Copyright &y& Elsevier]