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In this study, the distribution and partitioning of nine perfluorinated compounds (PFCs) in the water and sediment of Nansi Lake were systematically investigated. The total concentration of PFCs was in the range of 38.4-91.4 ng/L in the water and 0.47-1.81 ng/g in the sediment. The concentration of perfluorooctanoic acid (PFOA) was the highest in all the homologues in the water and was in the range of 34.9-84.6 ng/L. However, perfluorooctane sulfonate (PFOS), PFOA, and perfluoroundecanoic acid (PFUnDA) were the predominant PFCs in the sediment, and their levels were similar. The levels of PFOA, PFHpA, PFOS, PFNA, and the total PFCs in the water were relatively higher in the upper region than those in the lower region of Nansi Lake. In the sediment, the levels of PFOA, PFOS, and PFUnDA showed the similar distribution tendency. Industrial wastewater discharged from the cities around Nansi Lake was the main sources of PFCs. The partitioning coefficients (K d ) of PFOA, PFNA, PFDA, and PFOS were in the range of 0.29-0.87, 1.43-2.18, 2.08-3.15, and 2.20-2.80, respectively. Therefore, the log K d of PFDA and PFOS was apparently high as compared to two other compounds. The organic matter content of the sediment had no effect on the partitioning of PFCs between sediment and water in Nansi Lake.

The long-term industrialization and urbanization of Guangzhou city may lead to heavy metal contamination of its aquatic sediment. Nevertheless, only few studies have been published on the distribution and contamination assessment of heavy metals in this urban river sediment. Thus, the major objective of this study was to quantitatively assess contamination of heavy metals and their chemical partitioning in the sediments of the Guangzhou section of the Pearl River (GSPR). Surface sediment samples were collected at 10 sites in the main river and 12 sites in the creeks of the GSPR. The total content of Cd was determined by graphite furnace atomic adsorption spectrometry (GF-AAS), and content of Cr, Cu, Pb and Zn was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). The chemical partitioning of these heavy metals in the sediments of the main river was determined by the sequential selective extraction (SSE) method. Results indicated that the average total concentrations of Cd, Cr, Pb, Cu and Zn in the sediments of the main river were 1.44, 63.7, 95.5, 253.6 and 370.0 mg/kg, respectively, whereas they were 2.10, 125.5, 110.1, 433.7 and 401.9 mg/kg in the sediments of the creeks. The sediment at M4 and C9 sites was heavily contaminated with about 8 and 11 of toxic unit, respectively. Cr, Cu, Pb and Zn were mostly bound to organic matter and in the residual phase, whereas Cd was mostly associated with the soluble and exchangeable phase and the residual phase. The mobility and bioavailability of Cd, Zn and Cr in the sediments of the main river were relatively higher than Cu and Pb, due to higher levels in the soluble and exchangeable fraction and the carbonate fraction. The potential acute toxicity in the sediments of the main river and creeks was mainly caused by Cu contamination, accounting for 21.7-37.1% and 16.9-46.3% of the total toxicity, respectively, followed by Zn and Pb. Adverse biological effects induced by heavy metals would be expected in the sediments of the GSPR. Therefore, the sediments of the GSPR, especially at M4 and C9 sites, need to be remediated to maintain aquatic ecosystem health.

The Nansi Lake has been seriously affected by long-term intensive industrial and urban activities. The objectives of this study were to determine the content, distribution, and ecological risk of arsenic and investigate the geochemical relationships between arsenic forms and sediment mineral phases of the Nansi Lake. Twenty samples of surface sediments were collected and analyzed for arsenic contents and chemical forms. Results indicated that total content of arsenic in the sediment samples averaged 13.45 mg/kg and ranged from 8.27 to 21.75 mg/kg. The arsenic was mostly associated with iron oxides (67.3%), followed by the association with the residual fraction (19.2%). In addition, total content of arsenic was positively correlated with the organic matter and iron contents in the sediment. The molar ratios of iron oxide bound arsenic content to iron content are lower than the maximal molar ratios of arsenic to iron for natural hematite, magnetite, and goethite. The total content of arsenic in the sediment samples was usually higher than threshold effect concentration of 9.79 mg/kg, but lower than probable effect concentration of 33.0 mg/kg for arsenic in freshwater sediments. Adverse effects or toxicity to the aquatic organisms, caused by arsenic in the sediments of the Nansi Lake, will likely occur at these levels of arsenic contamination.

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