[Phosphorus Adsorption Characteristics and Loss Risk in Sediments of Lake Bay During the Overwinter Period of Cyanobacteria].

The overwinter period is the pre-stage of the algal bloom, and the endogenous phosphorus (P) in sediments is one of the main P sources of algal blooms during this period. Based on the investigation of the water quality and sediment pollutants during the overwinter period of cyanobacteria (recruitment period and dormancy period), this study analyzed the P release characteristics of sediments in the horizontal and vertical directions and clarified the P release risk of sediments and the change in microbial community structures. The results showed that the lake bay was moderately eutrophic in the two periods of the study area, and the water quality and sediment nitrogen and P pollution were more serious, and the chlorophyll a content (Chl-a) was still at a high level in the overwinter period. The pseudo-second order model and the modified Langmuir model could respectively describe the P kinetics and sorption isotherm behavior in the sediment. The theoretical maximum P sorption capacities (Qmax) of sediments were bottom layer>middle layer>surface layer, and the highest value was 1.648 mg·g-1 with the highest P sorption rate constant of the pseudo second-order kinetic model of 6.292 g·(mg·min)-1. Additionally, the P adsorption parameters (Qmax, NAP, and EPC0) were mainly affected by the physical and chemical properties of the sediment itself and the nutritional level of the lake bay. The surface sediments from the dormancy period mainly played the role of P sinks, and the part of sediments from the recruitment period played the role of P sources, in which existed the risk of endogenous P release. The analysis of the microbial community structure in sediments indicated that the microbial diversity in the sediments during the dormancy period was higher than that during the recruitment period, and some microbial categories with phosphate-solubilizing function of relative abundance was high.

[Characteristic analysis of the adsorption/desorption of nitrogen and phosphorus in the sediments of Taihu Lake].

The adsorption isotherms curves of 90 simples were studied in Taihu Lake through the experiment of adsorption/desorption. And the relation between the equilibrium concentrations, NAP, adsorption efficiency and corresponding parameter in interstitial water and sediment has been analyzed, in order to analyze the "source" and "collection" of Taihu. The results showed that the isotherms curves of nitrogen and phosphorus in the sediment had significant correlations in the range of the concentrations of experiment. The average equilibrium concentrations of nitrogen and phosphorus are 1.10 mg/L and 0.11 mg/L respectively. The average of NAP of nitrogen and phosphorus are 23.55 mg/kg and 11.72 mg/kg respectively. The NAP of nitrogen and phosphorus are higher in the area of serious pollution. The average adsorption efficiency of nitrogen and phosphorus are 23.14 L/kg and 102.09 L/kg respectively. Significant correlations were found between the equilibrium concentrations of adsorption/desorption of nitrogen and phosphous and corresponding parameter in interstitial water or sediment. Overall the sediment is the "source" of the nitrogen and phosphorus.

[Classification and pollution characteristic analysis for inflow rivers of Chaohu Lake].

Based on main pollution sources and characteristics of inflow rivers of Chaohu Lake, the inflow rivers are clustered and the pollution levels are classified by statistical methods. In addition, the correlation between algal biomass and the river nutrients input loads is derived according to the inflow river water quality monitoring parameters and the Chl-a concentrations in lake areas. Results show that the inflow rivers are classified into three groups. Urban pollution, soil and water conservation, and non-point source pollution are the major factors which influence water quality respectively. The input loads of permanganate index, NH4(+) -N, TN, TP from urban pollution rivers to the whole lake are 41.29%, 89.49%, 72.27% and 60.14% to all inflow rivers respectively. Organic pollution is the main pollution source of inflow rivers by factor analysis. The pollution rank of nine inflow rivers are as follows: Nanfei River > Shiwuli River > Paihe River > Shuangqiao River > Zhegao River> Yuxi River> Baishishan River > Zhaohe River> Hangbu River. The algal biomass and the NH4(+) -N, TN, TP inputs of inflow rivers are positively correlated.