Temporal and spatial distribution of phosphorus in the Xiangxi River

The phosphorus in water and sediment collected at different time from the Xiangxi River were analyzed. The results indicated that the phosphorus pollution have significant relations to human activities (especially the phosphorus industry). The concentrations of total-phosphorus (TP), total dissolved phosphorus (TDP) and dissolved phosphorus (DP) in Dec. 2004 were higher than those in Jul. 2005; the TP contents of sites 15 and 16 were much higher than others', the TP content of the largest site 16 was 1946.29 mg/kg in Dec. 2004 and 1756.11 mg/kg in Jul. 2005, respectively, which was much higher than the average (1497.51 mg/kg and 1369.38 mg/kg, respectively). The TP content in the sediment of the Xiangxi River was from 1179.53 mg/kg to 1851. 20 mg/kg. The TP contents of most sites except site 18, 19 and 20 were higher in Dec. 2004 than those in Jul. 2005. The aluminium-phosphorus (Al-P) content in the sediment was obviously higher in Jul. 2005 than that in Dec. 2004, which indicated that the stability of Al-P has a significant relation to the change of season

The comparison of phosphorus and nitrogen pollution status of the Xiangxi Bay before and after the impoundment of the Three Gorges Reservoir

As the first tributary of Changjiang River nearby Three Gorge reservoir, the water quality of Xiangxi River could directly influence the water quality of the Three Gorges reservoir, thus the research of phosphorus of Xiangxi River could provide useful information for preventive measures. Water and sediments samples along the Xiangxi River were collected before and after the impoundment of the Three Gorges Reservoir at 1996-1997 and 2004, respectively. Total phosphorus and nitrogen of water samples, as well as species of phosphorus of sediment samples were determined to reveal the pollution Status of the River. The results indicated the concentrations of total phosphorus was lower than 0.05mg/L for the upper reaches and 0.22-0.34mg/L for the lower reaches before the impoundment of the Three Gorges Reservoir, which was mainly influenced by the discharge of industry wastewater as well as domestic sewage. However, the concentrations of nitrogen mainly depended on agricultural pollution and show little difference along the river, which was among 0.7-1.1mg/L. After the impoundment of the Three Gorges Reservoir, the concentrations of phosphorus and nitrogen increased obviously except for phosphorus of the backwater area, which was caused by the deposit process of the particle phosphorus. Even though, as the ratios of nitrogen to phosphorus were general greater than 10 in the backwater area as well as the slower water now, the possibility of algae bloom eruption increased. Also, compared with some other rivers in China, the phosphorus pollution of the sediment of the Xiangxi River was serious. The concentration of total phosphorus in the sediments is as high as 1221 mg/kg, with the inorganic phosphorus as the main portion. In addition, with the average concentration of 609.4mg/kg, the calcium bound phosphorus is the main form among different inorganic phosphorus forms, compared with labile phosphorus and iron / aluminium bound phosphorus. This research suggested that the adverse impact caused by the Three Gorges Reservoir emerged and necessary measure is urged to prevent the eutrophication

Characters of phosphorus sorption in sediment of Three Gorges Reservoir Xiangxi Bay

Natural adsorption of phosphorus and the phosphorus force adsorption of different grain size on three samples of sediments taken form Xiangxi liver Bay Three Gorges Reservoir were determined in laboratory. The results indicated that the total phosphorus (TP) concentration of overlying water was significantly correlated to the TP concentration of sediment, the TP concentration of sediment influenced the water quality of the overlying water greatly. The critical equilibrium concentration of three samples were CI :0.188mg/L, C2:0.147mg/L and C3:0.188mg/L, respectively. And the saturated adsorption capacities were Delta Q1:268.16mg/kg, Delta Q2:57.96mg/kg, Delta Q3:267.27mg/kg; the two items were consistent. The influence of grain size oil phosphorus adsorption was significantly related to the physico-chemical properties of sediment. The adsorption capacities of three unfiltered samples were 1.5mg/g, 0.8mg/g and 1.4mg/g respectively. The result also indicated that the saturated adsorption capacities didn't change according to the largest adsorption capacities. The phosphorus in sediment of xiangxi liver was a source to overlying water until the environment condition changed. If the saturated adsorption capacities, largest adsorption capacities and critical equilibrium concentration can be correlated mathematically, the Department of the Enviroment will have a scientific basis to administer industries near the Xiangxi River

Comparative toxicity of nano-ZnO and bulk ZnO suspensions to zebrafish and the effects of sedimentation, (center dot)OH production and particle dissolution in distilled water

With the common application of nanoscale zinc oxide (nZnO) and significant potential for its release directly into aquatic environments, it is urgent to carry out research on ecotoxicological impact of nZnO. The characterization of nZnO, the amount of (center dot)OH in suspensions in the presence of light and the acute toxicity of nZnO and its bulk counterpart suspensions, as well as the acute toxicity of Zn(2+) solution to zebrafish (Danio rerio) at 96 h were studied. It was found that nZnO aggregated into irregular shapes in suspensions, and showed a relationship between its size distribution and concentration. In the presence of light, nZnO suspensions could generate (center dot)OH, the concentration of which increased with time. Although it was generally thought that (center dot)OH played a role in the biotoxicity to zebrafish, similar toxicity was observed for the nZnO and bulk ZnO suspensions (96 h LC(50) 3.969 mg L(-1), 2.525 mg L(-1), respectively). Furthermore, the sedimentation of nZnO and bulk ZnO in suspensions, and the accumulation of Zn in zebrafish were studied. The results showed that dissolved Zn(2+), from nZnO and bulk ZnO in suspensions, were toxic to zebrafish, while the aggregation and sedimentation of nZnO suspensions reduced the toxicity of nZnO. However, Zn(2+) may not be the main source of acute toxicity of nZnO and bulk ZnO to zebrafish. The experimental results highlight the importance of a systematic assessment of toxicity mechanisms of metal oxide nanoparticles (NPs) to determine definitively whether their toxicity is caused by nano-effects