[Distribution Characteristics and Risk Assessment of Heavy Metals in the Sediments of the Estuary of the Tributaries in the Three Gorges Reservoir, SW China].

To investigate the pollution status of sediments at the junction of the Three Gorges Reservoir area, sediment samples were collected over four seasons from the junction of the estuary located at a tributary of the Ruxi River and the Yangtze River. The content of eight heavy metals (HMs), including Cr, Zn, Mn, Ni, Cu, As, Cd, and Pb, in sediments was determined by ICP-MS. The results showed the average levels of investigated HMs (in mg·kg-1) were Cr (45.24), Zn (46.46), Mn (406.14), Ni (20.885), Cu (12.49), As (7.02), Cd (0.253), and Pb (11.042). The distribution analysis indicated that the levels of HMs at the river mouth were higher than that of the tributaries of the middle reaches and the two sections nearby. The seasonal distribution shows that the heavy metal content in the spring sediment is higher than in summer, autumn and winter. In addition, the correlation analysis indicated that the eight HMs possessed similar homologous characteristics and had common exogenous inputs. The assessment of the Geo Accumulation Index showed slight Cd pollution in the estuary of Ruxi River, and the Potential Ecological Risk index showed that Cd presented moderate ecological risks. The toxic effect of benthonic organisms was possibly correlated to Ni contamination at the intersection of the tributary and main stream, which was supported by the evidence from the sediment quality criteria. In conclusion, the rating of ecological risk at the mouth of the Ruxi River tributary is slight.

[Seasonal variation characteristics of phosphorus speciation in the sediment of Changshou Lake].

To further know the seasonal variation characteristics of phosphorus species in lake sediment, the contents of different phosphorus species in the surface sediment sampling from Changshou Lake were determined by using the SMT sequential extraction method in July and November, 2009, and March, 2010. The contents of total phosphorus (TP) basically show an order of the low-water period, high-water period, and normal-water period from high to low, and the maximum appeared in Shoudao (2960.29 mg/kg) while the minimum in Guanjiakou (586.05 mg/kg). The mass fractions of phosphorus associated with hydrous ferric/aluminum oxides (Fe/Al-P) and organic phosphorus (OP) in TP at all sampling sits are in an order of the normal-water period, high-water period, and low-water period from high to low, and the maximum of Fe/Al-P appeared in Lewen (40.01%) while that of OP in the dam mouth (72.44%). The mass fraction of phosphorus bound to calcium salt (Ca-P) in TP is in an order of the low-water period, normal-water period, and high-water period, and the maximum appeared in Baibudang (15.52%). These results suggested that the phosphorus speciation in the sediment of Changshou Lake shows obviously temporal and spatial distribution characteristics, and Fe/Al-P is mainly influenced by pH of the overlying water, while OP is not apparently influenced by dissolved oxygen (DO).